Geochemical records of mudflat sediments from southern Saurashtra,Western India: Implications for Holocene climate and global teleconnection

Abstract

The heat transfer from the low latitudes to high latitudes is responsible for maintaining the earth’s climate dynamics. Thus, deciphering the possible mechanism driving the variability of the Indian summer monsoon (ISM) during the Holocene Epoch has been critical to understand the hydroclimatic changes of the low latitudes. Despite several efforts, the teleconnection of ISM with the global climate dynamics remains under-represented and poorly understood. The present study aims to delineate the ISM variability and its possible forcing mechanism from western India (Gujarat). In this study, a sediment core (~65 cm long) was raised from the Jaffrabad mudflat (MIT) in western Gujarat. The sediment samples were subjected to geochemical analysis to investigate paleomonsoon, paleo-sediment source and paleoweathering changes. The results show that, with the addition of intermediate sources, the sediments were principally derived from the hinterland’s Deccan basalts. Further, the study suggested a warm and wet climate due to strong ISM during 10,650−5500 cal yr BP associated with the solar as well as orbital forcings. The weak monsoon during 5500−2700 cal yr BP has been linked with southward migration of the Intertropical Convergence Zone (ITCZ) along with the increased El Niño-like conditions. Further, the wavelet analysis revealed that a combined influence of solar, orbital and North Atlantic forcings led to monsoon variability along western India, during the Holocene Epoch. By reconciling the geochemical proxies, the present study has implications in the reconstruction of paleomonsoon and establishing the possible teleconnection with the global climate system.

Keywords

Geochemical proxies Global teleconnection Holocene Natural climate forcings Paleoweathering southern Saurashtra Wavelet analysis

Introduction

The dynamics of the Earth’s climate system rely on the oceanic and atmospheric heat transport from low latitudes to high latitudes. The current interglacial period, the Holocene Epoch (~11.8 ka to present) was initially assumed to be of consistent climate. However, the globally distributed paleoclimate reconstruction provided mounting evidence to demonstrate that the Holocene has evolved as a fluctuating climate modulated by the internal and external forcing mechanism (Banerji et al., 2020; Mayewski et al., 2004; Misra et al., 2019; Wanner et al., 2008). The solar inputs have been the prime factor which can be attributed to long-term changes caused by Earth’s orbital variability while short-term changes have been led by perturbations in the sun itself during the Holocene epoch (Mayewski et al., 2004). In higher latitudes, the enhanced solar insolation of the early Holocene driven by orbital forcing resulted in the stepwise withdrawal of the largest ice sheets of the northern hemisphere (Laurentide Ice Sheet) that prevailed during the last glaciation and finally disappeared ~6.8 ka (Carlson et al., 2008; Clark et al., 1999). While at low latitudes, the increased solar insolation during the early Holocene triggered the northward migration of the mean latitudinal position of the Intertropical Convergence Zone (ITCZ) promoting the boreal summer monsoon rainfall thereby leading to prominent changes in the hydrological cycle (DeMenocal et al., 2000; Fleitmann et al., 2007; Haug et al., 2001). Concisely, it can be underscored that the high latitude climate variability is demonstrated through the growth and decay of ice sheets while the monsoon intensities predominantly govern the climate system of low-latitude regions (DeMenocal and Rind, 1993). Despite the colossal evidence from both high and low latitudes, the response of the low-latitude climate system towards climatic signals emanating from the high latitudes remains severely unaddressed.

The Indian Summer Monsoon (ISM), being a part of the low-latitude Asian Monsoon System exhibits a major control on the global hydrological cycle (Clift and Plumb, 2008). The ISM causes >80 % of rainfall over the Indian subcontinent and nearby regions and generally prevails during June-August as a result of northward migration of the ITCZ. The southward shift in the ITCZ leads to the winter monsoon [western disturbances (WD) from December to February and northeast monsoon (NEM) from October to December] in the selected regions of India (Dimri et al., 2016; Dixit and Tandon, 2016; Resmi and Achyuthan, 2018).

The variations in the ISM strength have been linked with the rejuvenation and collapse of civilisation over thousands of years (Enzel et al., 1999; Pokharia et al., 2017; Prasad et al., 2014; Staubwasser and Weiss, 2006). Moreover, in the last few decades, the conspicuous occurrence of torrential rainfall events or severe droughts (Krishnan et al., 2009; Shaw and Nguyen, 2011) have profoundly impacted agricultural production, economic status, and a few billion of human lives. Such ISM perturbations have invoked the stark need to provide robust predictions of the seasonal monsoon rains with better accuracy that has canonical implications in the socio-economy of the country. However, the direct observational data of ISM rainfall seldom goes beyond the last few decades to centuries. Hence, a comprehensive view of the large-scale mechanism operative on the local, regional and global scale climate system is needed with improved spatiotemporal scale for advanced and accurate prediction of the Indian monsoon and for developing mitigation strategies for the ongoing global warming scenarios (Krishna Kumar et al., 2005).

Gujarat, the westernmost state of India, witnesses varied climatic patterns ranging from humid, subhumid, semi-arid, and arid to the extremely arid zones (Merh, 1995; Prasad et al., 2014) which have been endorsed due to variability in ISM rainfall pattern (Kshetrimayum, 2007). The prevalence of climatic variability led to substantial attempts to address the ISM perturbations during the Holocene Epoch. The multiproxy attempt on the Wadhwana Lake deposit, mainland Gujarat demonstrated a cool and moist climate during ~7500−5560 cal yr BP and stronger ISM after ~3500 cal yr BP, interrupted by a dry climate during 5560−4250 cal yr BP (Prasad et al., 2014). A multiproxy approach on the sediment core from Pariyaj Lake, Vatrak River basin, Gujarat revealed a wet climate and high lake stand during ~11,000 cal yr BP, 7630 cal yr BP and 4680−3500 cal yr BP interspersed by dry climate during 5864−4680 cal yr BP and 8000−9000 cal yr BP. The wet climate during 7630 cal yr BP and 4680−3500 cal yr BP has been attributed to winter rainfall in the Pariyaj Lake region (Raj et al., 2015). The lacustrine sequence of Timbi lake, Dhadhar river basin underscored three large flash floods from 4830 to 2730 cal yr BP and during ~1770 cal yr BP while enhanced monsoon and warm climate prevailed during 1730−880 cal yr BP and 880−360 cal yr BP (Sridhar et al., 2020). The Nal Lake, central Gujarat indicated a transition phase from arid to humid during 6.6−6 ka following which a dry climate interrupted by wet spells was observed during 6−4.8 ka. From 4.8 to 3 ka wettest climate was observed which later trended towards an arid phase till 2 ka and the present climate was attained after 2 ka (Prasad et al., 1997). Likewise, a wet phase before 2185 cal yr BP followed by an arid phase till 1809 cal yr BP has been revealed by the Narmada valley sediments (Sridhar et al., 2015). A multiproxy approach on the three sediment units at the Khari, Saraswati and Sabarmati Rivers demonstrated marine influence and high sea stand during 6070 ± 150 cal yr BP which was followed by high terrestrial flux till 2650 ± 180 cal yr BP interspersed with reduced rainfall and dry climate during 2650 ± 180 and 1530 ± 350 cal yr BP (Sridhar et al., 2018). The palynological attempt in the Mahi Estuary, mainland Gujarat revealed a coupled summer and winter monsoon rainfall during 3400−3000 cal yr BP followed by an arid climate from ~2850 cal yr BP onwards (Prasad et al., 2007). Similarly, two dry events at ~2.1 ka and 1.3 ka preceded by a subhumid condition at ~3 ka has been demonstrated from the lower Narmada valley, mainland Gujarat (Laskar et al., 2013). Further, four episodes of enhanced monsoon such as >5 ka, 4.6 ka and 4.6−1.7 ka were reported from slack water deposits of Mahi River, mainland Gujarat (Sridhar, 2007) while larger flood events were demonstrated during 1400−1440 CE (Sridhar et al., 2014). The mainland Gujarat has been significantly studied for the Holocene monsoon variability.

The Saurashtra peninsula of western Gujarat has provided enormous evidence of being the focal point for maritime activities during the Harappan civilisation (Gaur et al., 2009; Gaur and Bhatt, 2008; Pramanik, 2004). Other studies have combined archaeology and palynology to demonstrate the presence of rich forest cover due to the moist climate during the mid-Holocene which also resulted in the settlement and growth of Harappans along the Saurashtra coast as they significantly sustained based on agriculture, domestication and maritime activity (Farooqui et al., 2013). Considering the present and past socioeconomic significance of the Saurashtra region, there have been attempts to demonstrate the monsoon variability during the mid-Late-Holocene (Banerji et al., 2021, and references therein) using relict and active mudflats of the southern Saurashtra coast. However, a continuous reconstruction of monsoon variability throughout the Holocene epoch with special emphasis on the early Holocene and the response of the Saurashtra region towards global climate scenarios during the early Holocene remains poorly explored.

In general, the sheltered coastal environments such as mudflats, lagoons, estuaries, bays, rias, inlets and isolated basins are the prime realms that are capable of preserving thick Holocene sediment sequences and thus provide an opportunity to reconstruct a continuous paleoclimate and paleoenvironmental reconstruction, while occasionally it may also offer to investigate past sea level and land level changes (Lamb et al., 2006). The southern Saurashtra coast is marked by 40–50 m vertical cliffs of miliolite limestone and extensive tidal mudflats. These active mudflats receives terrestrial contribution only during the monsoon rainfall which leads to the activation of seasonal rivers and during high tides when they receive marine sediments, thereby demonstrating its inimitable characteristics. Considering the above, the present study broadly aims to reconstruct the paleomonsoon variability and decipher the global teleconnection during the Holocene Epoch from the mudflats of the Southern Saurashtra coast, Western Gujarat. The objectives for the present study are: (i) To understand the paleoweathering and paleo-sediment source in the mudflats of southern Saurashtra coast; (ii) To reconstruct the past ISM rainfall variability from the southern Saurashtra region that predominantly witnesses ISM rainfall; (iii) To deconvolute the possible teleconnection of the ISM with regional and global climate scenarios.

Regional settings

Geologically, the Saurashtra peninsula of western Gujarat, India comprises Deccan basalt with Tertiary and Quaternary limestone along with alluvium fringed around the coastal region (Figure 1). The extensive thickness of tholeiitic flood basalts (Najafi et al., 1981), several volcano-plutonic complexes (Naushad et al., 2019), the prevalence of rhyolite and granophyre and extensive compositional diversity (Sheth et al., 2011, 2012) are the prime features that distinguish Saurashtra Deccan basalts from the rest of the Deccan plateau of west-central India. The Deccan trap is unconformably overlain by miliolites, Gaj beds, fluvial gravels and clays (Figure 1). Three age ranges viz. 200–140, 115–75 and 70–50 ka have been identified for the miliolites based on U-Th dating techniques, nevertheless, the age and its origin are still contentious (Baskaran et al., 1986).

Figure 1.

Geology of southern Saurashtra along with the seasonal rivers draining into the mudflats of Jafrabad and Rohisa. The MIT core location has been marked by a red star. The Jafrabad mudflat is drained by Raidy River which is active during ISM.

The mean annual rainfall of the Saurashtra region is ~600 mm with a maximum precipitation during the ISM (June to September) (Farooqui et al., 2013). The mean maximum and minimum temperatures vary between 34°C and 19°C respectively (Gundalia and Dholakia, 2013). Based on the forest type classification (Champion and Seth, 1968), the study area falls under 5A/C-1a (very dry teak forest). The dry deciduous teak forest constitutes Terminalia, Diospyros melanoxylon, Tectona grandis, Wrightia tinctoria. Savannah includes Acacia grasses such as Dicanthium annulatum, Sehima nervosum, Apludamutica, Chrysopogon, Heteropogon, Cymbopogon, Aristida. Thorn scrub forest consists of A. catechu, A. marmalos, A. nilotica, B. aegyptica, A. leucophloea, etc. (Farooqui et al., 2013). The previous study at the Vasoj relict mudflat, NE Diu Island, southern Saurashtra coast revealed the prevalence of extensive mangrove forest including core mangrove species (Sonneratia sp., Bruguiera gymnorrhiza, Rhizophora mucronata, and Excoecaria agallocha) during 4.7 ka which gradually diminished as a result of sea regression and monsoon weakening (Banerji et al., 2015). The present study has been conducted on the exposed mudflats of Jaffrabad which is located ~40 km NE of Vasoj village along the southern Saurashtra coast, Gujarat.

Material and methods

The exposed mudflats Jaffrabad, southern Saurashtra coast, Gujarat were selected for the sediment core collection. Geologically, the mudflat is surrounded by biogenic carbonate rocks (miliolite) dated to ~178 ka (Baskaran et al., 1987). Presently the region seldom receives any marine influence, but the seasonal rivers get activated and deposit sediment during the ISM. The modern tidal flat sediments are dominated by clay, whereas the beach sediments are dominated by biogenic carbonate (Hardas and Patel, 1982).

A sediment core of 65 cm in length was raised from the exposed mudflat of Jaffrabad (MIT; Latitude: 20.889°N; Longitude: 71.382°E) with the help of a PVC hand-held corer (Figure 1). The sediment core was sub-sampled at 1 cm intervals with a Perspex knife to avoid metallic contamination. During the sampling of the sediment core, small-sized gastropod shells, broken shell pieces and bivalves were encountered from 26 cm to 65 cm. While the section from surface to 26 cm depth the sediment core was barren in terms of gastropod shells. The subsamples were preserved in zip lock polythene bags in a deep freezer till further analysis.

Chronology

The chronology of the core was established using AMS radiocarbon (¹⁴C) dating on the decarbonated sediment samples from the depths of 10.5, 22.5, 46.5 and 62.5 cm. The homogenised crushed bulk sediment samples were decarbonated with 0.5 N HCl to remove the carbonate fraction following which they were repeatedly washed with deionised water. The AMS radiocarbon dating for the organic fraction was conducted at the AURiS-AMS Facility at the Physical Research Laboratory, Ahmedabad, Gujarat (Bhushan et al., 2019a, 2019b).

Total organic carbon (TOC) and total nitrogen (TN)

The total organic carbon (TOC) indicates the in-situ productivity while the ratio between TOC and total nitrogen (TN) is frequently used for organic carbon source (Lamb et al., 2006; Tribovillard et al., 2006). In general, the TOC/TN >12 represents C₃ plants with high cellulose and lignin (Prahl et al., 1980) while TOC/TN <10 indicates C₄ plant of aquatic origin having high proteins and nucleic acids (Blackburn, 1983).

The total organic carbon (TOC) and total nitrogen (TN) was estimated on ~65 bulk homogenised sediment samples. The sediment samples were decarbonated with 0.1N HCl and thoroughly washed with the deionised water. Later, the dried decarbonated sediment samples were crushed and packed in tin capsules for the measurement of TOC and TN in NC analyzers (FISONS model NA 1500). The NC analyzer was calibrated using Low Organic Soil Sample (LOSS; Batch no. 647582814) as a reference material with 1.65% and 0.14% of carbon and nitrogen contents respectively (Bhushan et al., 2001).

Textural and geochemical analysis

The combined sieving and pipette analysis techniques of Lewis (1984) were used for the estimation of sand, silt and clay contents in the sediments. Nearly 20 samples were treated with 30% H₂O₂ and 10% HCl followed by wet sieving (diameter: 63 µm) to separate the sand fraction. The remaining fraction consisting of silt and clay was determined using pipette analysis.

Nearly, 33 samples from the MIT sediment core were selected, oven-dried at ~70°C, crushed, homogenised and washed with deionised water to eliminate the salt content in the sediment. Approximately 2 gm of the dried and combusted sediment samples were utilised in the preparation of pressed pellets to estimate the major oxides (SiO₂, Al₂O₃, Fe₂O₃, MgO, CaO and K₂O) and Zr using X-ray Fluorescence (XRF) technique at National Centre for Earth Science Studies (NCESS), Thiruvananthapuram, India. The finely powdered sediment samples were sprinkled over a boric acid binder filled in aluminium cups and pressed with a 40-ton hydraulic press for the 30 s. The measurement was performed on a Bruker S8 Tiger wavelength dispersive (WD) XRF instrument. The reproducibility of the instrument was monitored using international reference material SCO-1 and MAG.

Nearly 0.3 g of bulk sediment samples were digested by treating them with concentrated acids (HCl, HF and HNO₃) using a microwave digestion system. The digested samples were analysed for various trace elements (Ba, Cr, Co, Ni, Mn, Ti, Cu) by aspirating the sample solutions in the ICP-MS (Thermo-X series2) and rare earth elements (REE), Th and Sc were measured in HR-ICP-MS (Element XR HR-ICP-MS; Thermo Fisher Scientific) at Geosciences Division, Physical Research laboratory, Ahmedabad, India. The reproducibility of the geochemical data was monitored using NOVA (Agnihotri, 2001; Amin et al., 1972) and MAG. The precision and accuracy for the major and trace elements through XRF and ICP-MS were better than 5% (Banerji et al., 2017; Shaji et al., 2022) while for REE, Th and Sc measured through HR-ICP-MS were better than 7%.

Results

In the present study, the sediment core from Jaffrabad mudflats (MIT) was analysed with geochemical proxies supported by radiocarbon ages and textural variability to investigate the past climate and hydrological variability based on detrital flux, weathering changes, in-situ productivity, and possible influence of the sea level variability.

Chronology

The MIT sediment core was chronologically constrained using four AMS radiocarbon ages. The organic fractions at the depths of 10.5, 22.5, 46.5 and 62.5 cm yielded an age of 3644 ± 73, 4236 ± 61, 9279 ± 61 and 9786 ± 61 years BP respectively. The obtained radiocarbon ages were calibrated using Marine20 using CALIB Rev 8.2 (Heaton et al., 2020) with reservoir age (ΔR) correction of −4.0 ± 57.0 (Dutta et al., 2001; Southon et al., 2002). The calibrated ages obtained were 3391 cal yr BP, 4150 cal yr BP, 9893 cal yr BP and 10,567 cal yr BP for the depths 10.5, 22.5, 46.5 and 62.5 cm respectively (Figure 2a; Table 1). The age-depth model was prepared using the help of the RBACON package in R software (Figure 2b) which utilises the gamma autoregressive semiparametric method and yields the age estimations with the most reliable uncertainty estimation (Blaauw and Christen, 2011; Wang et al., 2019). The sedimentation rates varied from 0.042 to 2.4 mm/year with the lowest sedimentation rate observed during 22−47 cm (4150−9893 cal yr BP) and the MIT represented a sediment depositional history between 2790 and 10,650 cal yr BP. In order to investigate the past monsoon and hydroclimate variability from the MIT core, the respective sample depths have been transformed into ages based on the sedimentation rates and following linear extrapolation using the calibrated radiocarbon ages.

Figure 2.

(a) The lithology of the sediment core MIT indicates that most of the core is composed of silty Clay and silty Mud. (b) the age-depth plot for the MIT sediment core generated using RBACON package [Note. zM – silty Mud; cM – clayey Mud; and zC – silty Clay].

Table 1.

Sample details along with the AMS radiocarbon ages and their respective calibrated ages for the MIT sediment core collected from the southern Saurashtra coast.

Sample Id	Lab Id	Depth (cm)	Radiocarbon Age (yr BP)	Age range (1 σ) (cal yr BP)	Median age (cal yr BP)
MIT-10-11	AURIS/19-75	10.5	3644 ± 73	3254−3668	3391
MIT-22-23	AURIS/19-74	22.5	4236 ± 61	4005−4283	4150
MIT-46-47	AURIS/19-72	46.5	9279 ± 61	9845–10,164	9893
MIT-62-63	AURIS/19-71	62.5	9786 ± 61	10,416−10,869	10,567

Textural variation

The textural variation in the sediment core provides cues on the hydraulic activity (Pettijohn, 1957) thereby demonstrating the depositional environment. The textural variation for the MIT sediment core indicated sand, silt and clay ranging from 1.1% to 32.4%, 35.0% to 48.8% and 21.0% to 62.4 % respectively (Figure 3; Table 2). The MIT sediment core is predominantly composed of silty clay from 26 to 60 cm (~5130−10,440 cal yr BP) while silty mud prevails from surface to 21 cm (2790−4100 cal yr BP) and 60−65 cm (10,440−10,650 cal yr BP). However, a conspicuous layer of clayey mud is found at a depth of ~24.5 cm (~4655 cal yr BP). The textural variation and its classification is based on Picard (1971) while the classification of hydrodynamic conditions through the textural variation has been adopted from Pejrup (1988). Thus, the sediment from 24 to 60 cm consisting of silty clay (zC) deposited under calm conditions (Figure 3b and c) while the deposition of silty mud (zM) deposited under relatively higher hydrodynamic conditions (Pejrup, 1988).

Figure 3.

(a) The downcore variation of sand, silt, clay and mud indicates that the MIT core is primarily composed of mud. The ternary plots of the MIT core depicting (b) textural variation broadly falling within silty mud, clayey mud and silty clay (Picard, 1971) and (c) energy regimes of the sediment depositional environment varying from calm to marginally violent (Pejrup, 1988). [Note. C – Clay; S – Sand; Z – Silt; zC – Silty Clay; cZ – Clayey Silt; sZ – Sandy Silt; cM – Clayey Mud; zM – Silty Mud; sC – Sandy Clay; sM – Sandy Mud; cS – Clayey Sand and zS – Silty Sand.]. The obtained AMS ages are marked as red star on the depth profile.

Table 2.

Textural variation for the MIT sediment core.

Sl. No	Sample ID	Depth (cm)	Sand (%)	Silt (%)	Clay (%)	Mud (%)	Textural classification
1.	MIT-0–1	0.5	32.38	46.65	20.97	67.62	Silty Mud (zM)
2.	MIT-8–9	8.5	12.16	48.75	39.09	87.84	Silty mud (zM)
3.	MIT-13–14	13.5	26.28	48.53	25.19	73.72	Silty mud (zM)
4.	MIT-20–21	20.5	26.14	46.36	27.50	73.86	Silty mud (zM)
5.	MIT-24–25	24.5	6.59	43.99	49.42	93.41	Clayey mud (cM)
6.	MIT-26–27	26.5	4.96	35.66	59.38	95.04	Silty clay (zC)
7.	MIT-28–29	28.5	4.41	41.56	54.03	95.59	Silty clay (zC)
8.	MIT-29–30	29.5	2.42	39.90	57.68	97.58	Silty clay (zC)
9.	MIT-31–32	31.5	5.3	42.12	52.58	94.7	Silty clay (zC)
10.	MIT-33–34	33.5	2.72	37.34	59.94	97.28	Silty clay (zC)
11.	MIT-34–35	34.5	1.7	35.88	62.42	98.3	Silty clay (zC)
12.	MIT-35–36	35.5	3.12	35.80	61.08	96.88	Silty clay (zC)
13.	MIT-37–38	37.5	2.06	40.21	57.73	97.94	Silty clay (zC)
14.	MIT-39–40	39.5	1.06	38.19	60.75	98.94	Silty clay (zC)
15.	MIT-41–42	41.5	1.78	42.70	55.52	98.22	Silty clay (zC)
16.	MIT-43–44	43.5	1.38	41.23	57.39	98.62	Silty clay (zC)
17.	MIT-45–46	45.5	5.60	35.01	59.39	94.4	Silty clay (zC)
18.	MIT-52–53	52.5	2.07	37.15	60.78	97.93	Silty clay (zC)
19.	MIT-59–60	59.5	8.21	40.33	51.46	91.79	Silty clay (zC)
20.	MIT-64–65	64.5	31.44	37.29	31.27	68.56	Silty mud (zM)

Major and trace elemental variation

In the MIT core, a marginally high TOC content with a gradual lowering has been observed during 10,650−9900 cal yr BP followed by a consistently low TOC until 6000 cal yr BP (Figure 4). From 6000 to 2700 cal yr BP, the TOC content has significantly fluctuated with a noticeable increase between 3300 and 3900 cal yr BP. However, unlike TOC, the TN content consistently remained low from 10,650−5000 cal yr BP while like TOC it also indicated prominent enhancement between 3300 and 4000 cal yr BP. In case of TOC/TN, higher values are observed during ~10,650 cal yr BP with a gradual declining trend in two steps viz during 7000−8000 cal yr BP and ~3900 cal yr BP (Figure 4). Until 8000 cal yr BP, the TOC/TN >12 demonstrating significant contribution of terrestrially derived TOC while after 8000 cal yr BP the region plausibly witnessed more of aquatic environment till 2700 cal yr BP.

Figure 4.

Downcore variation of CaCO₃, TOC, TN and TOC/TN for the sediment core MIT. The TOC/TN >12 indicated enhanced contribution of terrestrially derived TOC. The obtained AMS ages are marked as red stars on the depth profile.

The SiO₂ variation remained nearly consistent with marginal enhancement during 10,350−10,650 cal yr BP and reduction during 5000−6000 cal yr BP. The overall trend of Al₂O₃ and TiO₂ displayed a similar trend (r = 0.71) with higher values between 10,650 and 5000 cal yr BP followed by significant lowering from 5000 to 2790 cal yr BP (Figure 5). Additionally, other major elements such as Na₂O, K₂O, Fe₂O₃ and trace elements viz Mn, Cu, Co, and Sr concentration also followed a trend comparable with Al₂O₃ and TiO₂. In the MIT core, the SiO₂/Al₂O₃, TiO₂/Al₂O₃ and Zr/Al₂O₃ remained nearly consistent during 10,650−5000 cal yr BP with a conspicuous spike in case of TiO₂/Al₂O₃ between 10,350 and 10,600 cal yr BP while a significant enhancement in SiO₂/Al₂O₃, TiO₂/Al₂O₃ and Zr/Al₂O₃ is inferred during 5000−2700 cal yr BP (Figure 6).

Figure 5.

Downcore variation of elemental concentration indicating its mutual association [Note. The concentration of SiO₂, Al₂O₃, TiO₂, Na₂O, K₂O and Fe₂O₃ are in %; and Mn, Cu and Co are in ppm]. The obtained AMS ages are marked as red stars on the depth profile.

Figure 6.

Downcore variation of textural and chemical weathering proxies. The high values of textural proxies corroborated with the presence of increased sand and silt content while chemical weathering agrees with the clay fraction of the sediment core MIT. The obtained AMS ages are marked as red stars on the depth profile.

The chemical weathering is an imperative process in controlling the global hydrogeochemical cycle of elements resulting in the elemental partition between continental rocks and water (Taylor and McLennan, 1985; Zhao and Zheng, 2015). Sediment weathering can result due to microbes, climate, the nature of source rocks, and relief (Joshi, 2014; Madhavaraju et al., 2016; Xi et al., 2014). The chemical weathering has been addressed using Chemical Index of Alteration (CIA) that measures the degree and intensity of chemical weathering (Fedo et al., 1996; Nesbitt and Young, 1982) and the Plagioclase Index of Alteration (PIA) that access the plagioclase weathering (Fedo et al., 1995). The CIA and PIA values in the MIT sediment core ranged from 47 to 61 and 46 to 63 respectively with a gradual increase during 10,650−10,200 cal yr BP and remained consistently high till 5000 cal yr BP following which abruptly declined and remained consistent till 2790 cal yr BP (Figure 6). Additionally, the index of compositional variability (ICV) is also being estimated which deciphers the abundance of alumina with respect to the other major cations in minerals or rocks, and it is also frequently used to study mineralogical maturity and weathering intensity (Cox et al., 1995). In addition to this, the ICV values were also estimated wherein it ranged from 2.7 to 8 and remained consistently low during 1065−5000 cal yr BP followed by enhancement till 2700 cal yr BP. Overall the ICV demonstrated an anticorrelation pattern with CIA and PIA variation. The ICV values suggested immature sediments as the rock forming minerals shows ICV >0.84 while clay minerals such as kaolinite, illite, etc. show <0.84 (Cox et al., 1995). Usually, the Ti/Ca successfully provided cues on Ti-bearing clastic sedimentary flux compared to the in situ carbonates (Hu et al., 2012).

The organic carbon productivity was estimated for the MIT core based on TOC, however, the TOC content is usually prone to degradation and therefore, the Cu/Al₂O₃, Zn/Al₂O₃, and Ni/Al₂O₃ account for paleoproductivity changes. The Cu/Al₂O₃, Zn/Al₂O₃ and Ni/Al₂O₃ demonstrated high values during 10,650−10,050 cal yr BP following which they consistently remained low except a marginal enhancement observed during 3500−5500 cal yr BP reminiscing the TOC trend signifying the in-situ productivity (Figure 7). Usually, the TOC is being annihilated by the aerobic organism that devours the available ambient dissolved oxygen. The continued consumption of oxygen can lead to sub-oxic, anoxic or euxinic conditions depending on the concentration of the oxygen. Under such oxygen-depleted environment, the migration and enrichment of the selected elements prevail between sediment and porewater or between water and sediment-water interface (Banerji et al., 2016; Tribovillard et al., 2006) thereby leading to depletion (Mn and Fe) and enrichment (Cr, Mo, V, etc.) of selected elements, providing cues on paleoredox conditions (Tribovillard et al., 2006). The oxygen-deficient conditions can be estimated using redox-sensitive elements (Banerji et al., 2016; Tribovillard et al., 2006). In the MIT core, the enriched Mo/Al₂O₃, V/Al₂O₃, Co/Al₂O₃ and Cr/Al₂O₃ while reduced Mn/Al₂O₃ observed during 10,650−10,200 cal yr BP demonstrated anoxic conditions while an intermittent occurrence of euxinic prevailed during 10,100−10,350 cal yr BP as indicated from the conspicuous spike of Mo/Al₂O₃.

Figure 7.

Comparison of redox-sensitive proxies with the TOC content. A reducing condition has been depicted during 10,440−10,650 cal yr BP as indicated by the Al₂O₃ normalised V, Mo, Zn, Cr and Mn. The obtained AMS ages are marked as red stars on the depth profile.

Major oxides estimated from MIT core raised from the mudflats of southern Saurashtra plotted on the Harker variation diagram. A broad negative correlation between SiO₂ versus Al₂O₃, K₂O, MgO and Fe₂O₃ (Figure 8) while Al₂O₃ (Figure 8) versus TiO₂, K₂O, Fe₂O₃ and Na₂O showed a positive correlation. The binary plot of log (Fe₂O₃/K₂O) versus log (SiO₂/Al₂O₃) indicates that most of the samples fall within the Fe-sand and Fe-shale field (Figure 9). The Al₂O₃/TiO₂, SiO₂/Al₂O₃, Fe₂O₃/K₂O and K₂O/Al₂O₃ ratios in the studied sediments range from 5 to 11, 3.34 to 8.63, 4.84 to 8.21 and 0.09 to 0.20, respectively. To decipher the enrichment and depletion of major and trace elements with respect to the upper continental crust (UCC), the elemental concentrations of the sediment samples from the MIT sediment core of southern Saurashtra have been normalised with the UCC (Figure 9b). It is noted that most of the major elements (TiO₂, FeO, CaO and MgO) show enrichment as compared to the UCC.

Figure 8.

Binary variation diagram for the selected major oxides of the MIT samples from the Jaffrabad mudflats, southern Saurashtra.

Figure 9.

(a) Geochemical classification diagram for the studied sample (Herron, 1988); (b and c) UCC normalised major and trace element concentrations wherein the UCC values taken from elsewhere (Rudnick and Gao, 2013); (d) Chondrite normalised REE diagram for the Jaffrabad mudflats; (e) PAAS normalised REE diagram for the Jaffrabad mudflats.

The relative concentrations of trace elements with respect to UCC are illustrated in Figure 9c. The low field strength elements (LFSEs) such as Rb and Ba are depleted with respect to UCC while Sr remained mostly enriched. The concentration of high field strength elements (HFSEs) such as Y, Zr, Hf, Th, and U are depleted with reference to UCC values. The studied sediments have average Cr and Ni values (Cr = 74.06 ppm; Ni = 41.61 ppm; Cr/Ni = 1.99). The Cr contents of the meta-sediments are lesser than those of PAAS (110 ppm), NASC (125 ppm) and UCC (92 ppm). However, the Cr/Ni ratios of many of the studied samples demonstrate a wide range (1.06–5.02) and on an average they are lower than NASC (2.15) but concurrent with PAAS (2) and UCC (1.96). Additionally, the Sc and Co abundances in the MIT core are comparable with the UCC values.

In terms of the total REE content (∑REE), the MIT sediments range from 2.61 to 110.27 ppm (avg. ∑REE = 64 ppm). In the chondrite normalised REE patterns (Figure 9d) the studied sediments have fractionated REE patterns, with (La/Yb)_N ratio varying from 2.69 to 142.13, (La/Sm)_N from 2.47 to 4.55. The (Gd/Yb)_N ratios (0.75–1.90) suggest a reasonably flat HREE pattern. The MIT samples show weak Eu anomalies (0.83–0.98) except for two samples which have positive Eu anomalies (1.29 and 1.48). The lack of prominent negative Eu anomaly is attributed to the partial weathering of plagioclase feldspar, suggesting the robustness of REE during weathering. In PAAS-normalised (Figure 9e) REE patterns with a majority of samples showing slight LREE depletion [(La/Sm)_N = 0.56–1.04], HREE enrichment (Gd/Yb)_N = 0.54–3.56; except for a three samples), (La/Yb)_N ratios varying from 0.28–2.25 and positive Eu anomalies (Eu/Eu* = 1.27–2.25).

Discussion

The paleohydrological and palaeoclimatic variabilities are usually ascribed by changes in terrestrial contribution, sediment provenance, weathering intensities, redox conditions and paleoproductivity that has been prominently assessed by geochemical variations in the sediments and sedimentary rocks (Claes et al., 2019; Sun et al., 2012). The ionic potential (IP), redox potential (Eh), distribution coefficient and pH are the prime governing factors that controls the mobility of elements in the sediments and sedimentary environment (Banerji et al., 2022a; Bjørlykke, 2010). Further, the climatic parameters substantially supports in the transportation of the elements released during weathering which is either mediated by river or wind while the currents also plays a role in case for marine environment (Bertrand et al., 1996; Sageman and Lyons, 2003).

Sediment maturity and paleoweathering

Major oxides and their ratios have been used for the classification of sediments and to evaluate their maturity and sorting (Bhatia and Crook, 1986; Gupta et al., 2024). Sorting of minerals according to their size, density, and shape can strongly modify the relative abundance of different minerals, and consequently, the concentrations of chemical elements (trace elements) hosted in their lattice (Garzanti et al., 2010, 2011; McLennan et al., 1993a). Das and Haake (2003) suggested that the chemistry of the sediments is dependent on quartz and clay fraction which is related to grain size wherein there is an increase in Al₂O₃ in finer sediments (clays) and SiO₂ in the sands. A negative correlation between SiO₂ and Al₂O₃ suggests control of aluminous clay and quartz content (Figure 8). Major oxide plots against Al₂O₃ abundances make it possible to compare if the sediments are derived from significantly different source rocks, as Al₂O₃ is likely to be immobile during weathering and diagenesis. The behavioural pattern of most of the major oxides in MIT sediment of southern Saurashtra mudflat show linear positive trends with increasing Al₂O₃ (Figure 8), suggesting major influences of hydraulic fractionation (Roy and Roser, 2012) or might suggest their detrital origin and association with clay, feldspar and micaceous minerals (Babeesh et al., 2017).

The decrease in feldspar and clay content is suggestive of increased maturity and is reflected in the increased in SiO₂/Al₂O₃ ratios (Bouchez et al., 2011). The SiO₂ is generally more mobile compared to Al₂O₃ under tropical to subtropical environmental conditions, and the degree of weathering of soil profile can be differentiated by SiO₂/Al₂O₃ ratio (Nathan and Bijilal, 2016) and the SiO₂/Al₂O₃ has been used to decipher the textural maturity and sorting of sediments wherein the igneous and basic rocks have values between 3 and 5 while values greater than 5 suggest the maturity of sediments (Roser et al., 1996). Herron (1988) used Fe₂O₃/K₂O values as indicators of mineral stability while Cox and Lowe (1995) used the ratio of K₂O and Al₂O₃ wherein clays range from 0 to 0.3 while the range between 0.3 and 0.9 represents felspars thereby delineating the composition of original sediments. The studied sediments from the mudflats of southern Saurashtra have SiO₂/Al₂O₃, Fe₂O₃/K₂O and K₂O/Al₂O₃ ratios ranging from 3.34 to 8.63 (avg. = 5.82), 4.84 to 8.21 (avg. = 6.79) and 0.09 to 0.20 (avg. = 0.13) respectively, suggesting low maturity of the studied sediments which contain a considerable amount of clay.

The chemical composition of sediments rests on several geological and geomorphological factors (Joshi et al., 2021a; McLennan et al., 1993b). Various proxies like mineralogy, bulk chemistry and heavy minerals combined with statistical approaches have been widely used to distinguish the source lithologies of sediments and sedimentary rocks as well as for understanding the paleoweathering conditions (Banerji et al., 2022b; Joshi et al., 2021). Additionally, elemental ratios like Mg/Al, Ti/Al and Ti/Ca have been often used as terrestrial and well as proxies for clastic fluxes (Clift et al., 2014; Warrier and Shankar, 2009; Wayne Nesbitt and Markovics, 1997).

The intensity of the chemical weathering in the region has been inferred based on various weathering parameters like CIA, PIA and ICV (Cox et al., 1995; Fedo et al., 1995, 1996; Nesbitt and Young, 1982). The studied samples have a CIA range from 47 to 61 (Figure 10a and b) with an average value of 55 (CIA for UCC = 51 and PAAS = 70–75; Figure 8; McLennan et al., 1993; Sharma et al., 2013) suggesting that the source rocks have undergone weak chemical weathering. The CIA values of MIT sediments are well within the range and in agreement with the Mahi River sediments that drain Deccan traps (37–59; Sharma et al., 2013) and from the previously studied mudflats of Diu (CIA = 48.6–53.3; Banerji et al., 2021). The low CIA values for Mahi River sediments have been attributed to tectonically active and water-starved semi-arid conditions (Sharma et al., 2013) while low values for Diu mudflats were suggested to be caused by the absence of perennial rivers and climate. As the site of the present study is in the vicinity to the previously studied Diu mudflats, the possible reason for low CIA values could be attributed to the lack of perennial rivers and the prevailing climatic conditions. A number of studies have evaluated the degree of weathering and post-depositional K-addition using Al₂O₃–(CaO + Na₂O)-K₂O (A-CN-K) ternary diagram (Joshi et al., 2021c). As Al-rich sediments are released during weathering, the sediments tend to move sub-parallel to the A-CN join from their un-weathered source rocks which in turn can be used to decipher the composition of the source lithologies. The weathering trends for the studied samples indicate that it plots close to the feldspar line when extrapolated backward suggesting an intermediate sediment source (Figure 10a). The weathering trend of the mudflat sediment samples was similar to the Mahi River sediments that drain basaltic terrain (Sharma et al., 2013) and the previously studied Diu mudflats (Banerji et al., 2021).

Figure 10.

(a) A-CN-K ternary diagram for the MIT core wherein PAAS (Taylor and McLennan, 1995), Saurashtra Basalt (Melluso et al., 2006); Mahi River, average Tholeiite (Sharma et al., 2013); Marine Sediment off southern Saurashtra (Kurian et al., 2013) and sediments from Diu mudflats (Banerji et al., 2021) are plotted for comparison; (b) CIA versus ICV plot for MIT sediment suggest its textural immaturity and witnessed initial chemical weathering; (c) Th/U versus Th plot for the MIT core (McLennan, 1993); (d) Al₂O₃ versus TiO₂ diagram for the Jaffrabad mudflats, southern Saurashtra; (e) A-CNK-FM ternary diagram for Jaffrabad mudflats, southern Saurashtra. PAAS (Taylor and McLennan, 1995), Saurashtra Basalt (Melluso et al., 2006); Mahi River, average Tholeiite (Sharma et al., 2013) and Marine Sediment off southern Saurashtra (Kurian et al., 2013) and sediments from Diu mudflats (Banerji et al., 2021) are plotted for comparison.

The moderate CIA and high ICV values (ICV: 2.66–7.97 with an average of 5, CIA: 47–63 with an average of 56) from the studied sediments also corroborate limited chemical weathering of the source which is also attested by a low textural maturity of the studied sediments. The CIA versus ICV plot for the MIT sediment samples falls in the zone of weak weathering which reaffirms poor weathering of source rocks and generation of immature sediments (Figure 10b). The Th/U ratios of sediments have also been utilised to understand the weathering and recycling (Khan and Sarma, 2023; Ramos-Vázquez and Armstrong-Altrin, 2019). Generally, U⁺⁴ oxidises to U⁺⁶ due to the loss of U as removable (UO)⁻² during recycling and weathering. This process increases the Th/U ratio in sediments which is >4 in case of intense weathering and recycling (McLennan et al., 1995). The studied sediments have Th/U ratios ranging from 0.92 to 2.93 which is much less than UCC (3.89) and PAAS (4.84) suggesting weak weathering and recycling (Figure 10c).

Geochemical imprints of sediment source

Major and trace elements, their ratios, U-Pb isotopes and inclusions in heavy minerals etc. have been frequently used to decipher the source of sediments (Hifzurrahman et al., 2023; Slabunov et al., 2017, 2024). In the UCC normalised major and trace element plot, the marginal depletion of SiO₂, K₂O and enrichment of MgO and FeO as compared to the UCC reveals the characteristics of the source rock to be mafic to intermediate in composition. The depletion in K₂O and Na₂O may be associated with a relatively low concentration of feldspars in the sediments. The sediment being derived from a mafic to intermediate source is also revealed by comparable concentrations of Co and Ni to the UCC. The higher partition coefficient of Ti-oxides and Fe-bearing accessory phases can lead to enriched TiO₂ and Fe₂O₃ (Greber and Dauphas, 2019; Joshi et al., 2014) while the enrichment in mobile elements such as MgO and CaO reveals a poor intensity of chemical weathering in the source. Cai et al. (2022) suggested that Al, Ti oxides, Zr and hydroxides have low solubility in low-temperature aqueous medium and the ratio of the sample between Al₂O₃ and TiO₂ is very close to their source. The studied sample from the mudflat of southern Saurashtra is plotted on the Al₂O₃ versus TiO₂ variation diagram (Figure 10d) and the ratio between Al₂O₃ and TiO₂ ranges from 5 to 11 which suggests the basic to an intermediate/mix source (Roser and Korsch, 1988). Additionally, the Al₂O₃ versus TiO₂ diagram (Figure 10d) illustrates that most samples fall in the basic to intermediate source field. Heterogeneity in the source sediments for the southern Saurashtra mudflats can also be suggested in the Fe₂O₃/K₂O versus log ratios of SiO₂/ Al₂O₃ diagram (Figure 9a) where a range from Fe-shale to Fe-sand is noted. The source of the sediments can be further confirmed from the Al₂O₃-(CaO*+ Na₂O + K₂O)-(FeO + MgO) (A-CNK-FM; Figure 10e) ternary diagram (Lamine Malick and Ishiga, 2016; Nesbitt and Young, 1989) wherein the studied sediments plot near the feldspar and biotite join near the field of basalts and average tholeiite which further reaffirms limited chemical weathering of the mafic to an intermediate source.

The enrichment and depletion of trace elements in the UCC normalised trace element diagram (Figure 9c) also suggest derivation from a mafic to the intermediate source. As Th has high partition coefficient for felsic lithologies while Sc and Co prefer mafic rocks, their ratios can provide insights into source lithologies. Mafic source lithologies have Th/Sc ratio of <0.8 and Th/Co ratios ranging between 0.04 and 1.40 while the Th/Sc ratio >1 and Th/Co ratio ranging from 0.67 to 19.4 are typical of the upper crust. The studied sediments have Th/Sc and Th/Co values ranging from 0.04 to 0.42 and 0.02 to 0.35 which suggests their derivation from mafic lithologies. This is also supported by the Th/Cr versus La/Cr, Th/Sc versus La/Sc, La/Th versus Hf and Co/Th versus La/Sc plots (Figure 11) wherein the studied sediments fall well below the UCC and felsic compositions. The samples are characterised by low Th/Cr, Th/Sc and high La/Th concentrations thereby suggesting derivation from a mafic to the intermediate source. Furthermore, the studied sediments plot well below the average values of PAAS and UCC in the field of depleted mantle sources suggesting to be derived from mafic sources (Figure 10c).

Figure 11.

Trace element discriminant plots of (a) Th/Cr versus La/Cr; (b) Th/Sc versus La/Sc (Bhatia and Crook, 1986); (c) La/Th versus Hf (Floyd and Leveridge, 1987); and (d) La/Sc versus Co/Th plot (Gu et al., 2002) for the MIT core from the Jaffrabad mudflats, southern Saurashtra. Potential sources are plotted for comparison (Condie, 1993).

The relative immobility of REEs during weathering and diagenesis makes them impeccable source indicators. The REE patterns of mafic rocks have low total REEs, (La/Yb)_N ratios and smaller or no Eu anomalies whereas those of more silicic rocks usually show higher (La/Yb)_N ratios and prominent negative Eu anomalies (Cullers et al., 1997; Cullers and Graf, 1984; McLennan, 1989; Šoster et al., 2020). Low concentrations of total REE and lack of prominent Eu anomalies in the studied sediments indicate a contribution from a mafic source. The low UCC normalised LREE/HREE (<0.1) values further support that the sediments were sourced from mafic lithologies. Similar REE (Figure 10c) patterns were earlier observed from sediments derived from mafic sources in Mahi River sediments (Sharma et al., 2013) and Cauvery catchment in southern India (Sensarma et al., 2008). The above discussion supporting mafic rocks as a dominant source, thereby suggesting that the studied sediments have been majorly derived from the Deccan basalts of Saurashtra.

Holocene climate, periodicities and global linkage

The climate variability of the recent interglacial period, ‘the Holocene Epoch’, has been a prime focus not only due to the climate perturbations but also perceived the growth and development of human society. Recently, the Holocene epoch has been broadly ratified into the Greenlandian (11.8−8.2 ka), Northgrippian (8.2−4.2 ka) and Meghalayan (4.2 ka−Present) Stages by the International Commission on Stratigraphy (ICS; Cohen et al., 2013; Walker et al., 2018). The present section aims to demonstrate the monsoon reconstruction, the interplay of dominant periodicities responsible for the monsoon variability and its global linkages.

Paleomonsoon variability

Present day, the study area is solely influenced by ISM variability causing improved hydrological conditions leading to enhanced terrestrial contribution. A high terrestrial contribution during 10,650−5000 cal yr BP followed by a prominent decline after 5000 cal yr BP can be inferred from the variations in the Al₂O₃, TiO₂, Na₂O, K₂O, Fe₂O₃ and trace elements (Mn, Cu, Co; Figure 5). The increased terrestrial contribution is supported by the TOC/TN values>12 indicating dominance of terrestrially derived TOC mediated by improved hydrological environment (Figure 4). Further, the region also witnessed improved chemical weathering accompanied by the deposition of clastic sediments from the hinterland during 10,650−5000 cal yr BP, as indicated by the higher values of CIA and PIA. The simultaneous prevalence of enhanced detrital flux and intense chemical weathering underscores warm and humid conditions during 10,650−5000 cal yr BP. The climatic period corroborated well with the globally recognised Holocene Climate Optimum (HCO) which co-occurred with the strengthening of ISM. The strong ISM strengthening has been demonstrated from Wadhwana Lake, mainland Gujarat during 7500−5560 cal yr BP based on a multiproxy approach (Prasad et al., 2014). Likewise, the palynological investigation of the Nakta Lake sediment, Chhattisgarh revealed warm and humid conditions during 11,700−8500 cal yr BP (Quamar and Kar, 2020). The persistent depletion in the δ¹⁸O_sw during 12−3 ka from the western Bay of Bengal suggested intensified ISM (Govil and Divakar Naidu, 2011) which corroborated well with the observations made from the eastern Arabian Sea (Govil and Naidu, 2010). Various marine and terrestrial (Banerji et al., 2022c; Haridas et al., 2022; Misra et al., 2019; Quamar et al., 2024) records have underscored strong ISM strength during the globally recognised HCO.

The lowering of elemental concentration of Al₂O₃, TiO₂, Na₂O, K₂O and other trace elements such as Mn, Cu and Co during 5500−2700 cal yr BP (Figure 5) corroborated well with the reduction in the clay content. While the deposition of coarser fraction during 5500−2700 cal yr BP can be inferred from increased TiO₂/Al₂O₃, SiO₂/Al₂O₃, Zr and Zr/Al₂O₃ (Figure 6) supported by higher silt content and increased ICV values. Additionally, weak monsoon and reduced humidity can be inferred from reduced chemical weathering demonstrated by low CIA and PIA. Further, during 4000−3300 cal yr BP, the region also witnessed increased in-situ productivity as indicated by enhanced TOC, along with an increase Cu/Al₂O₃ and Ni/Al₂O₃ which accounts for improved paleoproductivity (Figure 7). In addition to enhanced in-situ productivity, the peaking of ICV and Zr/Al₂O₃ (Figure 6) during 4000−3300 cal yr BP demonstrates the climate amelioration during 4000−3300 cal yr BP. The multiproxy study from the mudflats of Vasoj and Diu of the southern Saurashtra coast suggested a warm and humid climate during 4710−2825 cal yr BP (Banerji et al., 2015) and 4105−2640 cal yr BP (Banerji et al., 2017) respectively. Likewise, the study from Nal Sarovar, mainland Gujarat demonstrated the wettest climate during 4.8−3 ka which trended towards arid climate till 2 ka (Prasad et al., 1997) and the slack water deposits from the Mahi River basin elucidated enhanced episodes of monsoon during >5, 4.6 and 4.6−1.7 ka (Sridhar, 2007). The palynological investigation on the swamp, in the NW of Amarkantak, Madhya Pradesh suggested a warm and moderately humid climate during 3600−2761 cal yr BP associated with the strengthened ISM (Chauhan, 2015). An extensive mangrove forest during 7220−4770 years BP followed by its gradual decline since 3500 years BP has been inferred from the Konkan coast based on the palynological study (Limaye and Kumaran, 2012). An enhanced ISM during 10,000−5800 years BP followed and preceded by weak ISM during 11,500–10,500 years BP and 5000–2000 years BP has been demonstrated from the Sanai Tal lake, central Ganga Plain, Uttar Pradesh (Sharma et al., 2004). Thus, it can be suggested that the region witnessed reduced ISM during 5500−2700 cal yr BP with an intermittent period of climate amelioration during 4000−3300 cal yr BP resulted due to improved hydrological conditions in the study area led by the influence of monsoonal activity.

Wavelet analysis

The study of cyclicities in geological processes tend to seek periodicities in data series and explain them in terms of known natural phenomena (Preston and Henderson, 1964). Previous studies have shown cyclic patterns in marine organisms and atmospheric carbon dioxide over the past 500 Ma (Rohde and Muller, 2005). Prokoph and Puetz (2015) noted period-tripling patterns in geological and palaeobiological events on a timescale of ~30–1600 Ma. Several studies have suggested a cyclicity of ~700–900 Myr for the formation of supercontinents or continental growth events (Chen and Cheng, 2018; Joshi et al., 2022). The identification of the periodicities of the geological events in nature provides clues on past cyclic events and delineates future projections (Chen and Cheng, 2018). Generally, a Cross Wavelet Transform (XWT) is performed to reconnoitre the consistency in the phase relationship within the regions in time-frequency space with large common power. The XWT aids in revealing their common power and relative phase in time-frequency space. The continuous wavelet transform (CWT), cross wavelet transform (XWT) and wavelet coherence (WTC) analysis for CIA, ICV and TOC/TN are performed (Figures 12 and 13). The statistically significant common features in the XWT of CIA, ICV and TOC/TN time series (Figure 13) stand out at a 5% error.

Figure 12.

The continuous wavelet transforms for (a) CIA, (b) ICV and left parenthesis (c) TOC/TN for the Jaffrabad mudflats. The thick black contour designates the 95% significance level against red noise and the cone of influence (COI) where edge effects might distort the picture is shown as a lighter shade.

Figure 13.

(a and b) Cross wavelet transform for CIA-ICV and their Wavelet coherence, (c and d) Cross wavelet transform for CIA and TOC/TN and their Wavelet coherence for the MIT sediment core from southern Saurashtra mudflat. The 95% significance level against red noise is shown as a thick contour. The relative phase relationship is shown as arrows (with in-phase pointing right, and anti-phase pointing left).

In the CWTs, the CIA, ICV and TOC/TN show prominent periodicities of 2048 years and 1024 years from ~5500 to 7500 years BP and ~4000–9000 years BP, respectively (Figure 12). The intensity of the periodicities for CIA and TOC/TN is comparatively higher than ICV. A short pulse of ~256 years periodicity during 7000−8000 cal yr BP and a continuous periodicity of ~512 years during 5000−8000 cal yr BP has been indicated by the CWT of TOC/TN (Figure 12c). The periodicity of ~2050 years corroborated well with the ~2200 years periodicity observed in the sediment core from off Oman and was associated with the oceanic circulation and ¹⁴C variation in the atmosphere (Naidu and Malmgren, 1995). Further, the ~1024 years cycle is in line with the ~950 years cyclicity reported from speleothems of Oman (Neff et al., 2001) and lake sediments from Alaska (Hu et al., 2003). The northern hemispheric ∆¹⁴C data of tree ring represented both 2200 years and 950 years cyclicity (Lean, 2001) while the atmospheric variation of ¹⁴C is attributed to solar activity (Stuiver and Braziunas, 1993) thus, both the presence of periodicities underscores the role of solar forcing. The XWT of CIA and ICV (Figure 13a) demonstrated that they were in-phase only at ~2050 years cycle during 6000−7000 cal yr BP other than this, throughout it remained anti-phased with a cycle of ~1024 years. In view of the present study area, the probable reason for their being anti-phased could be because the CIA is associated with chemical weathering which generally intensifies during warm and humid conditions usually caused by strong ISM while the ICV could be due to activation of local rivers (which otherwise are seasonal) by monsoonal activity led by WD as well. The enhanced winter precipitation has been witnessed by Gujarat during 3600−3400 years BP (Prasad et al., 2007) and during 503−193 cal yr BP (Banerji et al., 2019) wherein the latter has been linked with the enhanced western disturbance. The in-phase behaviour of the CIA and ICV during 6000−7000 cal yr BP could be due to the interplay of both ISM and the WD triggered by solar forcing (~2050 years cyclicity) and reduced TSI (Steinhilber et al., 2009). Nevertheless, throughout the intensity of ISM remained dominant as depicted from the CWT of CIA (Figure 12a). Additionally, the WTC (Figure 13b) indicated a prominent anti-phased scenario of CIA and ICV with cyclicity of ~256 years during 3000−4000 cal yr BP. The time range of 3000−4000 cal yr BP corresponds well with the lesser-known Minoan Warm Period (MWP: ~3300 years BP; Easterbrook, 2016). The periodicity of ~256 years possibly corresponds to ~282 years cyclicity of North Atlantic cold event registered from the Chesapeake Bay, eastern North America which in turn has been linked with the solar variations (Willard et al., 2005). There is a possibility that the study area witnessed the influence of WD linked with the North Atlantic cold climate during 3000−4000 cal yr BP. The possibility of winter rainfall is further supported by the occurrence of ~256 years cyclicity within the 95% significance level against red noise observed in the case of ICV while CIA though represented the same periodicity but remained <95 % significance level. The plausibility of winter precipitation during 3000−4000 cal yr BP can be supported by the previous study on palynological investigation of the Kothiyakhad sedimentary sequence, mainland Gujarat which revealed enhanced winter rainfall during 3600−3400 years BP (Prasad et al., 2007). However, the ~256 years cyclicity could also be representing ~250 years cycle of orbital forcings such as eccentricity, obliquity and precession (Loutre et al., 1992) or ~205 years of sun spot cycle (Solanki et al., 2004). Thus, an interplay of both ISM and WD could have played a significant role during 3000−4000 cal yr BP reframing the monsoonal variability. However, a detailed investigation is needed to delineate the possible forcing mechanism responsible for the climate perturbation during 3000−4000 cal yr BP and its impacts on the Indian monsoon system.

The XWT of CIA and TOC/TN (Figure 13c) was in-phase during 11,000−6500 cal yr BP with a periodicity of ~1024 years while after 6500 cal yr BP it suddenly shifted to anti-phased relationship continuing with the similar cycle (~1024 years). Strengthened monsoonal conditions resulted in enhanced weathering and terrestrially derived TOC causing an in-phased behaviour of CIA and TOC/TN with ~1024 years cyclicity underscoring the control of solar forcing. While after 6500 cal yr BP, the in-situ TOC was dominant thereby leading to anti-phased behaviour of CIA and TOC/TN. Moreover, the WTC (Figure 13d) indicated episodic in-phase events for CIA and TOC/TN with cyclicity of ~128−256 years (4000−5000 cal yr BP), ~256 (7000−8000 cal yr BP), 64−128 years (8000−9000 cal yr BP and 9000−10,000 cal yr BP). The possibility of in-phase events of CIA and TOC/TN could be due to the ISM variability episodes as the periodicities such as ~64 years, ~128 years and ~256 years are in-line with the periodicities obtained for ISM such as ~54 years, ~95 years, ~125 years and ~250 years from the sedimentary records of NE Arabian Sea thereby representing typically of solar forcing (Agnihotri et al., 2002).

Even though the wavelet analysis in the present study represented various periodicities originating from solar, and orbital and also showed the possible occurrence of winter precipitation, however, solar forcing remained the prime driving mechanism resulting in major variations in the monsoon thereby impacting the regional as well as the global climate system.

Global teleconnection

Unlike glacial-interglacial transitions, the Holocene climate remained nearly consistent yet the convoluted global climate system and its association with natural forcings remains poorly understood which restricted the climate modelling and their future climate projections. To decrypt the present climate variability and future projections, the high-resolution climate reconstruction and its association with climate variables need to be addressed on a regional and global scale. In view of this, the present section aims to address the linkage of monsoon variability engrossed in the mudflats of western India, with the global climate system and natural forcing mechanism.

The climate system during the Holocene has been largely regulated by Orbital, Solar and Volcanic forcings while other anthropogenic factors such as vegetation cover, Green House Gases (GHGs) and stratospheric ozone has played a prominent role during the last few centuries leading to a complicated feedback mechanism (Wanner et al., 2008). The enhanced events of the volcanic eruption during 9000−7000 yrs BP ago are prominently seen in the GISP2 ice core of Greenland (Zielinski and Mershon, 1997) resulted due to the crustal re-adjustments caused by the unloading of the glaciers during the termination of the glacial period (Grove, 1976; Zielinski et al., 1996). While the non-existence of such frequent volcanic episodes in the Antarctic ice core (Castellano et al., 2004) further supports the role of crustal readjustments during the early Holocene rather than its role in controlling the climate mechanism. The Greenland ice core (Figure 14a) demonstrated nearly 85% of the volcanic events matched with the documented volcanic eruptions during the last two millennia while only 30% of such events corroborated with documented volcanism during 2−9 ka (Zielinski et al., 1994; Zielinski and Mershon, 1997). In the MIT core, the climate for the last 2700 cal yr BP remains unregistered, thus the implication of volcanic forcing on monsoonal episodes recorded by the MIT core remains unaddressed. However, the previous study on the mudflat sediment core from Rohisa, western Gujarat revealed the possible role of volcanic event occurred after 800 cal yr BP in triggering the onset of the Little Ice Age (Banerji et al., 2019) thereby underscoring the role of volcanic forcing on monsoon variability of western India.

Figure 14.

Comparison of the global natural forcings such as Volcanic forcing from GISP2 ice core sulphate records (a; Castellano et al., 2005; Zielinski and Mershon, 1997), Orbital forcing (b; Berger and Loutre, 1994), Solar Insolation, Total Solar Insolation, and 10Be (b-c; Berger and Loutre, 1991; Finkel and Nishiizumi, 1997; Steinhilber et al., 2009), red colour intensity representing ENSO events from the Laguna Pallcacocha (d; Moy et al., 2002), Ice rafted debris (IRD) from North Atlantic (e; Bond et al., 2001), reconstructed the NAO index (e; Olsen et al., 2012) and AMOC strength (e; McManus et al., 2004), Siberian high and Icelandic low represented by K and Na content in the GISP2 ice core (f; Mayewski et al., 1997), ITCZ migration from the Cariaco Basin (g; Haug et al., 2001; Hughen et al., 1996) and Temperature reconstruction through GISP2 icecore (h; Alley, 2004) with the geochemical proxies of the present study depicting chemical weathering (i) and terrestrial contribution (j-k).

Generally, the orbital parameters (obliquity – At 9 ka: 24.230°; present day: 23.45°, perihelion – At 9 ka: 30 July; present day: 3 January and eccentricity – At 9 ka: 0.0193; present day: 0.0167) collectively (Figure 14b) led to differences for the solar radiation during July that was beyond 7% and 25–35 W/m² over a broader region of latitudes (Berger, 1978; Kutzbach and Guetter, 1986). Overall, a high obliquity and enhanced solar insolation during the commencement of the Holocene possibly led to the warming of the northern hemisphere (Lawrence et al., 2006; Mantsis et al., 2011) with the simultaneous strengthening of the ISM, as the higher solar forcings have been frequently linked with the monsoon strengthening episodes, especially during the early-Holocene (Banerji et al., 2020, 2022c). The conspicuous decline in the cosmogenic isotope such as ¹⁰Be (Figure 14c) further supports the improvement in the solar forcing (Finkel and Nishiizumi, 1997; Lal et al., 2005). Thus, the monsoon intensification from 10,650 to 5000 cal yr BP could be associated with the enhanced solar forcing with an interplay of the orbital parameters. Further, there has been a strong association of the ISM with the El Niño Southern Oscillation (ENSO) and North Atlantic Oscillation (NAO) of the Pacific Ocean and Atlantic Ocean respectively (Banerji et al., 2020, 2022c; Srivastava et al., 2017). During the Holocene, a shift towards increased El Niño activity was observed during the Late-Holocene which has been demonstrated by a coupled ocean-atmospheric model (Clement et al., 2000) and the lithic flux in off-Peru marine sediment (Rein et al., 2004) while low activities (Figure 14d) were observed during early Holocene (Moy et al., 2002). In general, the weak ISM or drought-like conditions prevails during the El Niño years (Pant and Parthasarathy, 1981; Rasmusson and Carpenter, 1983; Sikka, 1980). Thus, the ISM weakening after 5000 cal yr BP indicated by terrestrial and weathering proxies observed in the MIT agrees with increased El Niño like conditions. The prominent shift towards weak ISM indicated by the terrestrial and weathering proxies during ~5500 cal yr BP is in-line with the increased ice-rafted debris (IRD; Figure 14e; Bond et al., 2001) and weakening of Atlantic Meridional Overturning (AMOC; Figure 14e and f; McManus et al., 2004) thereby providing a linkage of ISM with the North Atlantic climate. As the ISM variability is a manifestation of the lateral migration of the ITCZ, the study from the Cariaco Basin (Figure 14g) suggested that the ITCZ has marginally shifted during the early-mid-Holocene compared to its prominent shift towards south during the Late-Holocene (Haug et al., 2001). The southward shift of the ITCZ has been associated with the weak ISM and can lead to strong WD resulting in winter precipitation. The plausibility of winter monsoon has been indicated during 3660–3400 years BP based on palynological investigation on the Kothiyakhad sedimentary sequence, Mahi estuary, Gujarat (Prasad et al., 2007). Further, the northern hemisphere temperature as indicated by the temperature reconstruction based on the GISP2 ice core of Greenland (Figure 14h) corroborated well with the trends of the geochemical proxies of the MIT sediment core (Figure 14i–k). The low chemical weathering and reduced detrital contribution in MIT possibly support the ISM weakening thereby underscoring the fact that the mudflat of Jaffrabaad, southern Saurashtra, western India responded in tandem with the regional as well as global climate variability.

Possible signatures of high sea level during early-mid-Holocene

A rapid rise of ~20 m/1000 years in the sea level has been deciphered for the western coast of India during 10,000−7000 years BP while during last 7000 years BP the sea level more or less fluctuated along the present level (Hashimi et al., 1995). In the present study, the occurrence of broken shells and intact shells of bivalve and gastropods between 26 cm (5130 cal yr BP) and 65 cm (10,650 cal yr BP) along with the presence of silty clay from 26 to 60 cm (~5130−10,440 cal yr BP) suggests the plausibility of high sea level which led to flooding of the mudflat and transforming it into a lagoon system. The presence of silty mud during 10,440−10,650 cal yr BP possibly underscores the fact that the rapid rise in the sea level during the onset of the Holocene submerged the coastal mudflat and transformed it into lagoon system. The rapid rise in sea level led to the sudden submergence of coastal plants which resulted in poor water ventilation causing oxygen-deficient conditions. In the sediment core MIT, the oxygen-deficient conditions can be deciphered from the depleted Mn/Al₂O₃ along with enhanced TOC, V/Al₂O₃, Zn/Al₂O₃, Mo/Al₂O₃, Cr/Al₂O₃ and Cu/Al₂O₃ (Figure 7). The present-day elevation of the MIT core site is ~3 m whereas the dating of the oyster shell collected from the Jaffrabad region demonstrated a high sea level of ~3 m during 5.4 ± 0.05 ka (Juyal et al., 1995). A multiproxy approach on the relict mudflat from the Vasoj village, NE of Diu Island indicated a high sea level of ~2 m inclusive of ~1 m of tectonic component (Banerji et al., 2015). As the Saurashtra peninsula witnessed neo-tectonism (Banerji et al., 2015; Bhatt and Bhonde, 2006; Pant and Juyal, 1993), the high sea level of ~3 m must have been affected by tectonic component which remains beyond the scope of the present work. However, it can be prominently underscored that a high sea level prevailed in the region during the early to mid-Holocene period followed by a gradual regression.

Conclusion

The mudflats on the southern coast of Saurashtra get terrestrial contributions only when seasonal rivers are activated. This presents a unique opportunity to study the region’s paleomonsoon, paleo-sediment supply, and paleoweathering. With relatively small contributions from intermediary sources, the major and trace elements geochemistry of the MIT core indicates poor maturity and sorting of the sediments, which mostly generated from restricted chemical weathering of Deccan basalts from the hinterland.

Despite the region experiencing strong monsoonal events during the early Holocene, the chemical weathering remained less operative thereby causing the deposition of immature sediments in the mudflat. Additionally, the sediment’s geochemical values revealed an intermediate to mafic signature, which was likely caused by the basalt from the Deccan traps in the hinterland, which was a major source of terrestrial sediment. Other sources contributed additional material, resulting in signatures with an intermediate or mixed composition, which will require further investigation in future studies.

The hypothesis that the ISM fluctuates in combination with other global climatic events and natural forcing mechanisms is supported by the mudflat records from Jaffrabad in southern Saurashtra, Gujarat, which show a connectivity between the ISM and global climate dynamics. The geochemical analysis of the MIT sediment core revealed ISM intensification with a warm and humid climate during 10,650−5000 cal yr BP followed by a prominent decline in the monsoon. The Holocene climate system was evidently controlled by the solar and orbital forcings, as supported by the trends of geochemical proxies. Further, the monsoon weakening after 5500 cal yr BP is in-line with the increased El Niño events and southward migration of the ITCZ. On the other hand, the existence of both whole and broken shell fragments provided evidence for the high sea level that formed the coastal lagoon system that eventually gave rise to a mudflat around 5500 years ago. However, further geomorphological studies are necessary to elucidate the evolutionary phases of the mudflats of Jaffrabad, southern Saurashtra coast. Additionally, the wavelet analysis also revealed interplay between ISM and WD during 3000−4000 cal yr BP which corresponded to the MWP, but it also invokes the need to explore other evidence for the occurrence of WD during the MWP.

Supplemental Material

sj-xlsx-1-hol-10.1177_09596836241266398 – Supplemental material for Geochemical records of mudflat sediments from southern Saurashtra, Western India: Implications for Holocene climate and global teleconnection

Supplemental material, sj-xlsx-1-hol-10.1177_09596836241266398 for Geochemical records of mudflat sediments from southern Saurashtra, Western India: Implications for Holocene climate and global teleconnection by Upasana S Banerji, Ravi Bhushan, Kumar Batuk Joshi, Ankur Dabhi, AK Sudheer, Chandra Prakash Dubey, Rakesh Kumar Panda, Nayana V Haridas and Mahesh Gaddam in The Holocene

Footnotes

Acknowledgements

USB and RB are thankful to Dr Navin Juyal, Dr. Balaji D. and Mr. J.P. Bhavsar for their kind help and support during the fieldwork. USB and RB are grateful to Prof. J.S. Ray for his support and help during the trace element measurement by Q-ICP-MS. USB, KBJ, and NVH thank the Director of NCESS for his encouragement and support. USB and NVH are thankful to Dr D Padmalal and Dr K. Maya for their encouragement and support. KBJ is thankful to Mr Nishanth for the help in the XRF measurements. NVH acknowledges the research fellowship through the MoES Research Fellow Program (MRFP). Authors extend special thanks to the anonymous reviewers for their constructive comments and suggestions which significantly improved the manuscript.

Author contributions

Upasana S Banerji: Conceptualisation; Formal analysis; Investigation; Methodology; Visualisation; Writing – original draft; Writing – review & editing.

Ravi Bhushan: Conceptualisation; Project administration; Resources; Supervision; Writing – review & editing.

Kumar Batuk Joshi: Formal analysis; Methodology; Resources; Visualisation; Writing – review & editing.

Ankur Dabhi: Data curation; Methodology; Resources; Software

AK Sudheer: Data curation; Formal analysis; Methodology; Resources; Validation; Writing – review & editing.

Chandra Prakash Dubey: Methodology; Resources; Software; Visualisation; Writing – review & editing.

Rakesh Kumar Panda: Formal analysis; Methodology; Visualisation.

Nayana V Haridas: Formal analysis; Methodology; Visualisation.

Mahesh Gaddam: Formal analysis; Methodology; Resources.

Funding

The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This research was funded by the Ministry of Earth Sciences, Govt. of India under GEOTRACES Project.

ORCID iD

Upasana S. Banerji

Supplemental material

Supplemental material for this article is available online.

References

Agnihotri

(2001) Chemical and Isotopic Studies of Sediments from Arabian Sea and Bay of Bengal. Faculty of Science. Udaipur: Mohanlal Sukhadia University.

Agnihotri

Dutta

Bhushan

, et al. (2002) Evidence for solar forcing on the Indian monsoon during the last millennium. Earth and Planetary Science Letters 198(3-4): 521–527.

Amin

Likhite

Radhakrishnamurty

, et al. (1972) Susceptibility stratigraphy and paleomagnetism of some deep Pacific Ocean cores. Deep Sea Research and Oceanographic Abstracts 19: 249–252.

Armstrong-Altrin

Nagarajan

Madhavaraju

, et al. (2013) Geochemistry of the Jurassic and Upper Cretaceous shales from the Molango region, Hidalgo, eastern Mexico: Implications for source-area weathering, provenance, and tectonic setting. Comptes Rendus Geoscience 345(4): 185–202.

Babeesh

Lone

Achyuthan

(2017) Geochemistry of Manasbal lake sediments, Kashmir: Weathering, provenance and tectonic setting. Journal of the Geological Society of India 89(5): 563–572.

Banerji

Joshi

Pandey

, et al. (2022a) An outline of geochemical proxies used on marine sediments deposited during Quaternary Period. In: Montenari

(ed.) Stratigraphy & Timescales. United States: Academic Press, Elsevier, pp.1–38, DOI: 10.1016/bs.sats.2022.09.002.

Banerji

Arulbalaji

Padmalal

(2020) Holocene climate variability and Indian Summer Monsoon: An overview. Holocene 30(5): 744–773.

Banerji

Bhushan

Joshi

, et al. (2021) Hydroclimate variability during the last two millennia from the mudflats of Diu Island, Western India. Geological Journal 56: 3584–3604.

Banerji

Bhushan

Jull

AJT

(2017) Mid−late Holocene monsoonal records from the partially active mudflat of Diu Island, southern Saurashtra, Gujarat, western India. Quaternary International 443: 200–210.

10.

Banerji

Bhushan

Jull

AJT

(2019) Signatures of global climatic events and forcing factors for the last two millennia from the active mudflats of Rohisa, southern Saurashtra, Gujarat, western India. Quaternary International 507: 172–187.

11.

Banerji

Bhushan

Maurya

(2016) Sedimentary records of paleoredox conditions at relict mudflat of Vasoj, Southern Saurashtra coast, Gujarat, India. Earth Science India 9(2): 114–125.

12.

Banerji

Dubey

Goswami

, et al. (2022b) Geochemical indicators in provenance estimation. In: John

A-A

Kailasa

Verma

(eds) Geochemical Treasures and Petrogenetic Processes. Springer Nature, pp.95–121. Singapore.

13.

Banerji

Padmalal

(2022c) Bond events and monsoon variability during Holocene-evidence from marine and continental archives. In: Kumaran

KPN

Padmalal

(eds) Holocene Climate Change and Environment. Elsevier, pp.293–338. Amsterdam, Netherlands.

14.

Banerji

Pandey

Bhushan

, et al. (2015) Mid-Holocene climate and land–sea interaction along the southern coast of Saurashtra, western India. Journal of Asian Earth Sciences 111: 428–439.

15.

Baskaran

Baldev

Sood

, et al. (1987) Geochronological studies of strandlines of Saurashtra, India, detected by remote sensing techniques. International Journal of Remote Sensing 8(2): 167–176.

16.

Baskaran

Marathe

Rajaguru

, et al. (1986) Geochronology of palaeolithic cultures in the Hiran Valley, Saurashtra, India. Journal of Archaeological Science 13: 505–514.

17.

Berger

(1978) Long-term variations of caloric insolation resulting from the Earth’s orbital elements. Quaternary Research 9: 139–167.

18.

Berger

Loutre

(1991) Insolation values for the climate of the last 10 million years. Quaternary Science Reviews 10(4): 297–317.

19.

Berger

Loutre

(1994) Precession, eccentricity, obliquity, insolation and paleoclimates. In: Duplessy

Spyridakis

(eds) Long-Term Climatic Variations. NATO ASI Series, Vol 22. Springer, Berlin, Heidelberg, pp.107–151.

20.

Bertrand

Shimmield

Martinez

, et al. (1996) The glacial ocean productivity hypothesis: The importance of regional temporal and spatial studies. Marine Geology 130(1-2): 1–9.

21.

Bhatia

Crook

(1986) Trace element characteristics of graywackes and tectonic setting discrimination of sedimentary basins. Contributions to Mineralogy and Petrology. 92(2): 181–193.

22.

Bhatt

Bhonde

(2006) Geomorphic expression of late quaternary sea level changes along the southern Saurashtra coast, western India. Journal of Earth System Science 115(4): 395–402.

23.

Bhushan

Dutta

Somayajulu

BLK

(2001) Concentrations and burial fluxes of organic and inorganic carbon on the eastern margins of the Arabian Sea. Marine Geology 178(1-4): 95–113.

24.

Bhushan

Yadava

Shah

, et al. (2019a) First results from the PRL accelerator mass spectrometer. Current Science 116(3): 361–363.

25.

Bhushan

Yadava

Shah

, et al. (2019b) Performance of a new 1MV AMS facility (AURiS) at PRL, Ahmedabad, India. Nuclear Instruments & Methods in Physics Research Section B, Beam Interactions With Materials and Atoms 439(November 2018): 76–79.

26.

Bjørlykke

(2010) Petroleum geoscience: From sedimentary environments to rock physics. In: Bjorlykke

Avseth

(eds) Petroleum Geoscience: From Sedimentary Environments to Rock Physics. Springer Berlin Heidelberg, pp.1–508.

27.

Blaauw

Christen

(2011) Flexible paleoclimate age-depth models using an autoregressive gamma process. Bayesian Analysis 6(3): 457–474.

28.

Blackburn

(1983) The microbial nitrogen cycle. In: Krumbein

(ed.) Microbial Geo-Chemistry. Oxford: Blackwell Scientific, pp.63–89.

29.

Bond

Kromer

Beer

, et al. (2001) Persistent solar influence on North Atlantic climate during the Holocene. Science 294(5549): 2130–2136.

30.

Bouchez

Gaillardet

France-Lanord

, et al. (2011) Grain size control of river suspended sediment geochemistry: Clues from Amazon River depth profiles. Geochemistry Geophysics Geosystems 12(3): Q03008.

31.

Cai

Ouyang

Luo

, et al. (2022) Geochemical characteristics and constraints on provenance, tectonic setting, and paleoweathering of middle Jurassic Zhiluo Formation sandstones in the Northwest Ordos Basin, north-central China. Minerals 12(5): 603.

32.

Carlson

LeGrande

Oppo

, et al. (2008) Rapid early Holocene deglaciation of the Laurentide ice sheet. Nature Geoscience 1(9): 620–624.

33.

Castellano

Becagli

Hansson

, et al. (2005) Holocene volcanic history as recorded in the sulfate stratigraphy of the European project for Ice Coring in Antarctica Dome C (EDC96) ice core. Journal of Geophysical Research Atmospheres 110(D6): 1–12.

34.

Castellano

Becagli

Jouzel

, et al. (2004) Volcanic eruption frequency over the last 45 ky as recorded in Epica-Dome C ice core (East Antarctica) and its relationship with climatic changes. Global and Planetary Change 42(1-4): 195–205.

35.

Champion

Seth

(1968) A Revised Survey of the Forest Types of India. Delhi, India: Manager of Publications.

36.

Chauhan

(2015) Vegetation and climatic variability in southeastern Madhya Pradesh, India since Mid-Holocene, based on pollen records. Current Science 109(5): 956.

37.

Chen

Cheng

(2018) Cyclicity and persistence of Earth’s evolution over time: Wavelet and fractal analysis. Geophysical Research Letters 45(16): 8223–8230.

38.

Claes

Huysmans

Soete

, et al. (2019) Elemental geochemistry to complement stable isotope data of fossil travertine: Importance of digestion method and statistics. Sedimentary Geology 386: 118–131.

39.

Clark

Alley

Pollard

(1999) Northern hemisphere ice-sheet influences on global climate change. Science 286(5442): 1104–1111.

40.

Clement

Seager

Cane

(2000) Suppression of El Niño during the mid-Holocene by changes in the Earth’s orbit. Paleoceanography 15: 731–737.

41.

Clift

Plumb

(2008) The Asian Monsoon: Causes, History and Effects. Cambridge, UK: Cambridge University Press Cambridge.

42.

Clift

Wan

Blusztajn

(2014) Reconstructing chemical weathering, physical erosion and monsoon intensity since 25Ma in the northern South China Sea: A review of competing proxies. Earth-Science Reviews 130: 86–102.

43.

Cohen

Finney

Gibbard

et al. (2013; updated) The ICS International Chronostratigraphic Chart. Episodes 36: 199–204.

44.

Condie

(1993) Chemical composition and evolution of the upper continental crust: Contrasting results from surface samples and shales. Chemical Geology 104(1-4): 1–37.

45.

Cox

Lowe

(1995) Compositional evolution of coarse clastic sediments in the southwestern United States from 1.8 to 0.2 Ga and implications for relationships between the development of crustal blocks and their sedimentary cover. Journal of Sedimentary Research 65(3a): 477–494.

46.

Cox

Lowe

Cullers

(1995) The influence of sediment recycling and basement composition on evolution of mudrock chemistry in the southwestern United States. Geochimica et Cosmochimica Acta 59(14): 2919–2940.

47.

Cullers

Graf

(1984) Rare earth elements in igneous rocks of the continental crust: Predominantly basic and ultrabasic rocks. Developments in Geochemistry 2: 237–274.

48.

Cullers

Bock

Guidotti

(1997) Elemental distributions and neodymium isotopic compositions of Silurian metasediments, western Maine, USA: Redistribution of the rare earth elements. Geochimica et Cosmochimica Acta 61(9): 1847–1861.

49.

Das

Haake

B-G

(2003) Geochemistry of Rewalsar Lake sediment, Lesser Himalaya, India: Implications for source-area weathering, provenance and tectonic setting. Geosciences Journal 7(4): 299–312.

50.

DeMenocal

Ortiz

Guilderson

, et al. (2000) Abrupt onset and termination of the African Humid Period: Rapid climate responses to gradual insolation forcing. Quaternary Science Reviews 19(1-5): 347–361.

51.

DeMenocal

Rind

(1993) Sensitivity of Asian and African climate to variations in seasonal insolation, glacial ice cover, sea surface temperature, and Asian orography. Journal of Geophysical Research 98(D4): 7265–7287.

52.

Dimri

Yasunari

Kotlia

, et al. (2016) Indian winter monsoon: Present and past. Earth-Science Reviews 163: 297–322. DOI: 10.1016/j.earscirev.2016.10.008.

53.

Dixit

Tandon

(2016) Hydroclimatic variability on the Indian subcontinent in the past millennium: Review and assessment. Earth-Science Reviews 161: 1–15.

54.

Dutta

Bhushan

Somayajulu

BLK

(2001) ΔR correction values for the northern Indian Ocean. Radiocarbon 43(2A): 483–488.

55.

Easterbrook

(ed.) (2016) Temperature fluctuations in Greenland and the Arctic. In: Evidence-Based Climate Science: Data Opposing CO2 Emissions as the Primary Source of Global Warming, 2nd edn. Elsevier: Amsterdam, Netherlands, pp.137–160.

56.

Enzel

Ely

Mishra

, et al. (1999) High-resolution Holocene environmental changes in the Thar Desert, Northwestern India. Science 284(5411): 125–128.

57.

Farooqui

Gaur

Prasad

, et al. (2013) Climate, vegetation and ecology during Harappan period: Excavations at Kanjetar and Kaj, mid-Saurashtra coast, Gujarat. Journal of Archaeological Science 40(6): 2631–2647.

58.

Fedo

Eriksson

Krogstad

(1996) Geochemistry of shales from the Archean (~3.0 Ga) Buhwa Greenstone Belt, Zimbabwe: Implications for provenance and source-area weathering. Geochimica et Cosmochimica Acta 60(10): 1751–1763.

59.

Fedo

Wayne Nesbitt

Young

(1995) Unraveling the effects of potassium metasomatism in sedimentary rocks and paleosols, with implications for paleoweathering conditions and provenance. Geology 23(10): 921–924.

60.

Finkel

Nishiizumi

(1997) Beryllium 10 concentrations in the Greenland Ice Sheet Project 2 ice core from 3-40 ka. Environmental Technology 102: 699–706.

61.

Fleitmann

Burns

Mangini

, et al. (2007) Holocene ITCZ and Indian monsoon dynamics recorded in stalagmites from Oman and Yemen (Socotra). Quaternary Science Reviews 26: 170–188.

62.

Floyd

Leveridge

(1987) Tectonic environment of the Devonian Gramscatho basin, south Cornwall: Framework mode and geochemical evidence from turbiditic sandstones. Journal - Geological Society (London) 144(4): 531–542.

63.

Garzanti

Andò

France-Lanord

, et al. (2010) Mineralogical and chemical variability of fluvial sediments1. Bedload sand (Ganga–Brahmaputra, Bangladesh). Earth and Planetary Science Letters 299(3-4): 368–381.

64.

Garzanti

Andó

France-Lanord

, et al. (2011) Mineralogical and chemical variability of fluvial sediments 2. Suspended-load silt (Ganga–Brahmaputra, Bangladesh). Earth and Planetary Science Letters 302(1-2): 107–120.

65.

Gaur

Bhatt

(2008) Marine archaeological explorations on western coast of the Gulf of Khambhat. Man and Environment 33(2): 99–104.

66.

Gaur

Sundaresh and Tripati

(2009) New evidence on maritime archaeology around Kodinar: Gujarat Coast, India. Man and Environment 34(2): 72–76.

67.

Geology of Gujarat, Geological Survey of India (GSI), Government of India, Kolkata, India, 2022.

68.

Govil

Divakar Naidu

(2011) Variations of Indian monsoon precipitation during the last 32kyr reflected in the surface hydrography of the Western Bay of Bengal. Quaternary Science Reviews 30(27-28): 3871–3879.

69.

Govil

Naidu

(2010) Evaporation-precipitation changes in the eastern Arabian Sea for the last 68 ka: Implications on monsoon variability. Paleoceanography 25(1): 1–11.

70.

Greber

Dauphas

(2019) The chemistry of fine-grained terrigenous sediments reveals a chemically evolved Paleoarchean emerged crust. Geochimica et Cosmochimica Acta 255: 247–264.

71.

Grove

(1976) Deglaciation—A possible triggering mechanism for volcanism. International Association of Volcanologists Symposium. Santiago, 88–97.

72.

Liu

Zheng

, et al. (2002) Provenance and tectonic setting of the Proterozoic turbidites in Hunan, South China: Geochemical evidence. Journal of Sedimentary Research 72(3): 393–407.

73.

Gundalia

Dholakia

(2013) Estimation of pan evaporation using mean air temperature and radiation for monsoon season in Junagadh region. International Journal of Engineering Research and Applications 3(6): 64–70.

74.

Gupta

Pandey

Arora

et al. (2024) Neoproterozoic crustal evolution of Indo-Australo-Antarctic Suture domain and Gamburtsev Subglacial Mountains, East Antarctica: Insights from the offshore sediments. Gondwana Research (In press). https://doi.org/10.1016/j.gr.2024.07.008

75.

Hardas

Patel

(1982) Coastal sands of Saurashtra, Gujarat. In: Merh

(ed.) Geology and Geomorphology of Quaternary Terrains of Gujarat With Special Reference to Coastal Evolution. Varodara, Gujarat: Geology Department, Faculty of Science, M.S. University of Baroda.

76.

Haridas

Banerji

Maya

, et al. (2022) Paleoclimatic and paleoceanographic records from the Bay of Bengal sediments during the last 30 ka. Journal of Asian Earth Sciences 229(March): 105169.

77.

Hashimi

Nigam

Nair

, et al. (1995) Holocene sea level fluctuations on western Indian continental margin: An update. Geological Society of India 46: 157–162.

78.

Haug

Hughen

Sigman

, et al. (2001) Southward migration of the intertropical convergence zone through the Holocene. Science 293: 1304–1308.

79.

Heaton

Köhler

Butzin

, et al. (2020) Marine20—The marine radiocarbon age calibration curve (0–55,000 cal BP). Radiocarbon 62(4): 779–820.

80.

Herron

(1988) Geochemical classification of Terrigenous Sands and shales from core or log data. Journal of Sedimentary Petrology 58(5): 820–829.

81.

Hifzurrahman Nasipuri

Joshi

(2023) Geochemistry of Jutogh metasediments, Lesser Himachal Himalaya, India, and their implications in source area weathering, provenance, and tectonic setting during Paleoproterozoic Nuna assembly. Journal of the Geological Society of India 99(7): 897–905.

82.

Böning

Köhler

, et al. (2012) Deep sea records of the continental weathering and erosion response to East Asian monsoon intensification since 14ka in the South China Sea. Chemical Geology 326–327: 1–18.

83.

Kaufman

Yoneji

, et al. (2003) Cyclic variation and solar forcing of Holocene climate in the Alaskan subarctic. Science 301(5641): 1890–1893.

84.

Hughen

Overpeck

Peterson

, et al. (1996) Rapid climate changes in the tropical Atlantic region during the last deglaciation. Nature 380(6569): 51–54.

85.

Joshi

Ray

Joshi

, et al. (2014) Geochemistry of pegmatites from South Delhi Fold Belt: A case study from Rajgarh, Ajmer district, Rajasthan. Current Science 106: 1725–1730.

86.

Joshi

(2014) Microbes: Mini iron factories. Indian Journal of Microbiology 54(4): 483–485.

87.

Joshi

Banerji

Dubey

, et al. (2021a) Heavy minerals in provenance studies: An overview. Arabian Journal of Geosciences. Springer 14(14): 1–16.

88.

Joshi

Banerji

Dubey

, et al. (2022) Detrital zircons in crustal evolution: A perspective from the Indian subcontinent. Lithosphere 2022(Special 8): 3099822.

89.

Joshi

Goswami

Banerji

et al. (2021) Recent developments in instrumentation and its application in absolute dating: Historical perspective and overview. Journal of Asian Earth Sciences 211: 104690.

90.

Joshi

Ray

Ahmad

, et al. (2021b) Geochemistry of meta-sediments from Neoproterozoic Shimla and Chail groups of outer lesser Himalaya: Implications for provenance, tectonic setting, and paleo-weathering conditions. Geological Journal 56(9): 4451–4478.

91.

Juyal

Pant

Bhushan

, et al. (1995) Radiometric dating of late Quaternary sea levels of the Saurashtra coast, Western India: An experiment with oyster and clam shells. Geological Society of India Memoir 32: 372–379.

92.

Khan

Sarma

(2023) Clastic rock geochemistry of the Sirohi Basin, Aravalli Craton, NW India: Implications for paleoweathering, provenance and geodynamics. Geosystems and Geoenvironment 2(1): 100105.

93.

Khan

Zhang

Liang

, et al. (2023) Geochemical assessment of river sediments at the outlets of Eastern Makran, Pakistan; implications for source area weathering and provenance. Minerals 13(3): 348.

94.

Krishna Kumar

Hoerling

Rajagopalan

(2005) Advancing dynamical prediction of Indian monsoon rainfall. Geophysical Research Letters 32(8): 1–4.

95.

Krishnan

Kumar

Sugi

, et al. (2009) Internal feedbacks from monsoon–midlatitude interactions during droughts in the Indian summer monsoon. Journal of the Atmospheric Sciences 66(3): 553–578.

96.

Kshetrimayum

(2007) Sedimentology and Geochemistry of Tidal Mudflats Along Central West Coast of India. Department of Marine Sciences. Goa, Goa University.

97.

Kurian

Nath

Kumar

, et al. (2013) Geochemical and isotopic signatures of surficial sediments from the western continental shelf of India: Inferring provenance, weathering, and the nature of organic matter. Journal of Sedimentary Research 83(6): 427–442.

98.

Kutzbach

Guetter

(1986) The influence of changing orbital parameters and surface boundary conditions on climate simulations for the past 18 000 years. Journal of the Atmospheric Sciences 43(16): 1726–1759.

99.

Lal

Jull

Pollard

, et al. (2005) Evidence for large century time-scale changes in solar activity in the past 32 Kyr, based on in-situ cosmogenic 14C in ice at Summit, Greenland. Earth and Planetary Science Letters 234(3–4): 335–349.

100.

Lamb

Wilson

Leng

(2006) A review of coastal palaeoclimate and relative sea-level reconstructions using δ13C and C/N ratios in organic material. Earth-Science Reviews 75(1-4): 29–57.

101.

Lamine Malick

Ishiga

(2016) Geochemical classification and determination of maturity source weathering in beach sands of eastern San’ in coast, Tango Peninsula, and Wakasa Bay, Japan. Earth Science Research 5(1): 44.

102.

Laskar

Yadava

Sharma

, et al. (2013) Late-Holocene climate in the lower Narmada valley, Gujarat, western India, inferred using sedimentary carbon and oxygen isotope ratios. Holocene 23(8): 1115–1122.

103.

Lawrence

Liu

Herbert

(2006) Evolution of the eastern tropical Pacific through Plio-Pleistocene glaciation. Science 312(5770): 79–83.

104.

Lean

(2001) Solar forcing of climate change in recent millennia. In: Wefer

Berger

Behre

, et al (eds) Climate Development and History of the North Atlantic Realm. Heidelberg: Springer, pp.75–88.

105.

Lewis

(1984) Practical Sedimentology. Stroudsburg, PA: Hutchinson Ross.

106.

Limaye

Kumaran

KPN

(2012) Mangrove vegetation responses to Holocene climate change along Konkan coast of south-western India. Quaternary International 263: 114–128.

107.

Loutre

Berger

Bretagnon

, et al. (1992) Astronomical frequencies for climate research at the decadal to century time scale. Climate Dynamics 7: 181–194.

108.

Madhavaraju

Tom

Lee

, et al. (2016) Provenance and tectonic settings of sands from Puerto Peñasco, Desemboque and Bahia Kino beaches, Gulf of California, Sonora, México. Journal of South American Earth Sciences 71(November 2018): 262–275.

109.

Mantsis

Clement

Broccoli

, et al. (2011) Climate feedbacks in response to changes in obliquity. Journal of Climate 24(11): 2830–2845.

110.

Mayewski

Meeker

Twickler

, et al. (1997) Major features and forcing of high-latitude northern hemisphere atmospheric circulation using a 110,000-year-long glaciochemical series. Journal of Geophysical Research 102(C12): 26,345–26,366.

111.

Mayewski

Rohling

Curt Stager

, et al. (2004) Holocene climate variability. Quaternary Research 62(3): 243–255.

112.

McLennan

Hemming

McDaniel

, et al. (1993) Geochemical approaches to sedimentation, provenance and tectonics: Processes controlling the composition of clastic sediments. Geological Society of America Special Papers 284: 21–40.

113.

McLennan

(1989) Rare earth elements in sedimentary rocks: Influence of provenance and sedimentary processes. In: Lipin

MCKAY

G.A.

(eds) Geochemistry and Mineralogy of Rare Earth Elements, Reviews in Mineralogy, vol. 21. Mineralogical Society of America, pp.169–200.

114.

McLennan

(1993) Weathering and global denudation. Journal of Geology 101(2): 295–303.

115.

McLennan

Hemming

Taylor

et al. (1995) Early Proterozoic crustal evolution: Geochemical and Nd-Pb isotopic evidence from metasedimentary rocks, southwestern North America. Geochimica et Cosmochimica Acta 59(6): 1153–1177. DOI: 10.1016/0016-7037(95)00032-U.

116.

McManus

Francois

Gherardi

, et al. (2004) Collapse and rapid resumption of Atlantic meridional circulation linked to deglacial climate changes. Nature 428(6985): 834–837.

117.

Melluso

Mahoney

Dallai

(2006) Mantle sources and crustal input as recorded in high-Mg Deccan Traps basalts of Gujarat (India). Lithos 89(3-4): 259–274.

118.

Merh

(1995) Geology of Gujarat. Bangalore: Geological Society of India.

119.

Misra

Tandon

Sinha

(2019) Holocene climate records from lake sediments in India: Assessment of coherence across climate zones. Earth-Science Reviews 190(December 2018): 370–397. Available at: https://linkinghub.elsevier.com/retrieve/pii/S0012825218304549.

120.

Moy

Seltzer

Rodbell

, et al. (2002) Variability of El Niño/Southern Oscillation activity at millennial timescales during the Holocene epoch. Nature 420(6912): 162–165.

121.

Naidu

Malmgren

(1995) A 2,200 years periodicity in the Asian Monsoon System. Geophysical Research Letters 22(17): 2361–2364.

122.

Najafi

Cox

Sukheswala

(1981) Geology and geochemistry of the basalt flows (Deccan Traps) of the Mahad-Mahableshwar section, India. Memoir-Geological Society of India 3: 300–315.

123.

Nathan

Bijilal

(2016) Geochemistry and Clay Mineralogy of Weathering and Soil Profiles. Malappuram District, Northern Kerala, India: Its Implications on Paleoclimate.

124.

Naushad

Dongre

Behera

, et al. (2019) Mineralogy of a new occurrence of lamprophyre dyke from the Saurashtra Peninsula of Gujarat, Northwest Deccan Trap, India. Journal of the Geological Society of India 93(6): 629–637.

125.

Neff

Burns

Mangini

, et al. (2001) Strong coherence between solar variability and the monsoon in Oman between 9 and 6 kyr ago. Nature 411(6835): 290–293.

126.

Nesbitt

Young

(1982) Early Proterozoic climates and plate motions inferred from major element chemistry of lutites. Nature 299: 715–717.

127.

Nesbitt

Young

(1989) Formation and diagenesis of weathering profiles. Journal of Geology 97(2): 129–147.

128.

Olsen

Anderson

Knudsen

(2012) Variability of the North Atlantic oscillation over the past 5,200 years. Nature Geoscience 5(11): 808–812.

129.

Pant

Parthasarathy

(1981) Some aspects of an association between the southern oscillation and Indian summer monsoon. Archives for Meteorology Geophysics and Bioclimatology Series B 29(3): 245–252.

130.

Pant

Juyal

(1993) Late quaternary coastal instability and sea level changes: New evidences from Saurashtra Coast, western India. Zeitschrift fir Geo-morphologie N.F 37(1): 29–40.

131.

Pejrup

(1988) The triangular diagram used for classification of estuarine sediments: A new approach. In: DE Boer

Van Gelder

Niod

(eds) Tide-Influenced Sedimentary Environments and Facies. Reidel, Dordrecht. pp.289–300.

132.

Pettijohn

(1957) Sedimentary Rocks. Harper, New York, USA.

133.

Picard

(1971) Classification of fine-grained sedimentary rocks. Journal of Sedimentary Research 41(1): 179–195.

134.

Pokharia

Agnihotri

Sharma

, et al. (2017) Altered cropping pattern and cultural continuation with declined prosperity following abrupt and extreme arid event at ~4,200 yrs BP: Evidence from an Indus archaeological site Khirsara, Gujarat, western India. PLoS One 12(10): e0185684.

135.

Prahl

Bennett

Carpenter

(1980) The early diagenesis of aliphatic hydrocarbons and organic matter in sedimentary particulates from Dabob Bay, Washington. Geochimica et Cosmochimica Acta 44(12): 1967–1976.

136.

Pramanik

(2004) Hathab: An early historic port on the Gulf of Khambhat. Journal of Indian Ocean Archaeology 1: 133–140.

137.

Prasad

Kusumgar

Gupta

(1997) A mid to Late-Holocene record of palaeoclimatic changes from Nal Sarovar: A palaeodesert margin lake in western India. Journal of Quaternary Science 12(2): 153–159.

138.

Prasad

Farooqui

Sharma

, et al. (2014) Mid–late Holocene monsoonal variations from mainland Gujarat, India: A multi-proxy study for evaluating climate culture relationship. Palaeogeography Palaeoclimatology Palaeoecology 397: 38–51.

139.

Prasad

Phartiyal

Sharma

(2007) Evidence of enhanced winter precipitation and the prevalence of a cool and dry climate during the mid to late Holocene in mainland Gujarat, India. Holocene 17(7): 889–896.

140.

Preston

Henderson

(1964) Fourier Series Characterization of Cyclic Sediments for Stratigraphic Correlation. In: Merriam

(ed.), Symposium on cyclic sedimentation: Kansas Geological Survey, Bulletin 169, pp.415–425.

141.

Prokoph

Puetz

(2015) Period-tripling and fractal features in multi-billion year geological records. Mathematical Geosciences 47(5): 501–520.

142.

Quamar

Banerji

Thakur

, et al. (2024) Hydroclimatic changes in the core monsoon zone of India since the Last Glacial Maximum: An overview of the palynological data and correlation with the marine and continental records. Palaeogeography Palaeoclimatology Palaeoecology 633: 111844.

143.

Quamar

Kar

(2020) Prolonged warming over the last ca. 11,700 cal years from the central Indian core monsoon zone: Pollen evidence and a synoptic overview. Review of Palaeobotany and Palynology 276: 104159.

144.

Raj

Chamyal

Prasad

, et al. (2015) Holocene climatic fluctuations in the Gujarat alluvial plains based on a multiproxy study of the Pariyaj Lake archive, western India. Palaeogeography Palaeoclimatology Palaeoecology 421: 60–74.

145.

Ramos-Vázquez

Armstrong-Altrin

(2019) Sediment chemistry and detrital zircon record in the Bosque and Paseo del Mar coastal areas from the southwestern Gulf of Mexico. Marine and Petroleum Geology 110: 650–675.

146.

Rasmusson

Carpenter

(1983) The relationship between eastern equatorial Pacific sea surface temperatures and rainfall over India and Sri Lanka. Monthly Weather Review 111(3): 517–528.

147.

Rein

Lückge

Sirocko

(2004) A major Holocene ENSO anomaly during the Medieval period. Geophysical Research Letters 31(17): L17211. DOI: 10.1029/2004GL020161.

148.

Resmi

Achyuthan

(2018) Northeast monsoon variations during the Holocene inferred from palaeochannels and active channels of the Palar River basin, Southern Peninsular India. Holocene 28: 895–913.

149.

Rohde

Muller

(2005) Cycles in fossil diversity. Nature 434(7030): 208–210.

150.

Roser

Cooper

Nathan

, et al. (1996) Reconnaissance sandstone geochemistry, provenance, and tectonic setting of the lower Paleozoic terranes of the West Coast and Nelson, New Zealand. New Zealand Journal of Geology and Geophysics 39(1): 1–16.

151.

Roser

Korsch

(1988) Provenance signatures of sandstone-mudstone suites determined using discriminant function analysis of major-element data. Chemical Geology 67(1-2): 119–139.

152.

Roy

Roser

(2012) Geochemistry of Tertiary sequence in Shahbajpur-1 well, Hatia trough, Bengal basin, Bangladesh: Provenance, source weathering and province affinity. Journal of Life and Earth Science 7: 1–13.

153.

Rudnick

Gao

(2013) Composition of the continental crust. In: Holland

Turekian

(eds) Treatise on Geochemistry-The Crust. Oxford: Elsevier-Pergamon, pp.1–51.

154.

Sageman

Lyons

(2003) Geochemistry of fine-grained sediments and sedimentary rocks. Treatise on Geochemistry 7–9: 115–158.

155.

Sensarma

Rajamani

Tripathi

(2008) Petrography and geochemical characteristics of the sediments of the small river Hemavati, Southern India: Implications for provenance and weathering processes. Sedimentary Geology 205(3-4): 111–125.

156.

Shaji

Banerji

Maya

, et al. (2022) Holocene monsoon and sea-level variability from coastal lowlands of Kerala, SW India. Quaternary International 642: 48–62.

157.

Sharma

Sensarma

Kumar

, et al. (2013) Mineralogy and geochemistry of the Mahi River sediments in tectonically active western India: Implications for Deccan large igneous province source, weathering and mobility of elements in a semi-arid climate. Geochimica et Cosmochimica Acta 104: 63–83. DOI: 10.1016/j.gca.2012.11.004.

158.

Sharma

Joachimski

Sharma

, et al. (2004) Lateglacial and Holocene environmental changes in Ganga plain, Northern India. Quaternary Science Reviews 23(1-2): 145–159.

159.

Shaw

Nguyen

(2011) Droughts in Asian Monsoon Region, Community, Environment and Disaster Risk Management. Kyoto, Japan, UK: Emerald Books, Kyoto University.

160.

Sheth

Choudhary

Bhattacharyya

, et al. (2011) The Chogat-Chamardi subvolcanic complex, Saurashtra, northwestern Deccan Traps: Geology, petrochemistry, and petrogenetic evolution. Journal of Asian Earth Sciences 41(3): 307–324.

161.

Sheth

Choudhary

Cucciniello

, et al. (2012) Geology, petrochemistry, and genesis of the bimodal lavas of Osham Hill, Saurashtra, northwestern Deccan Traps. Journal of Asian Earth Sciences 43(1): 176–192.

162.

Sikka

(1980) Some aspects of the large scale fluctuations of summer monsoon rainfall over India in relation to fluctuations in the planetary and regional scale circulation parameters. Proceedings of the Indian Academy of Sciences-Earth and Planetary Sciences 89(2): 179–195.

163.

Slabunov

Joshi

Kumar Singh

, et al. (2024) Depositional age and formation conditions of Archean banded iron formations, Bundelkhand Craton, Central India: Geochemistry, neodymium isotopes and U-Pb zircon geochronology. Precambrian Research 401: 107254.

164.

Slabunov

Singh

Joshi

, et al. (2017) Paleoarchean zircons from quartzite of South Bundelkhand Supracrustal Complex: Origin and implications for crustal evolution in Bundelkhand Craton, Central India. Current Science 112: 794.

165.

Solanki

Usoskin

Kromer

, et al. (2004) Unusual activity of the Sun during recent decades compared to the previous 11,000 years. Nature 431(7012): 1084–1087.

166.

Šoster

Zavašnik

O’Sullivan

, et al. (2020) Geochemistry of Bashibos-Bajrambos Metasedimentary Unit, Serbo-Macedonian massif, North Macedonia: Implications for age, provenance and tectonic setting. Geochemistry 80(4): 125664.

167.

Southon

Kashgarian

Fontugne

, et al. (2002) Marine reservoir corrections for the Indian Ocean and Southeast Asia. Radiocarbon 44(1): 167–180.

168.

Sridhar

(2007) A mid–late Holocene flood record from the alluvial reach of the Mahi River, Western India. CATENA 70(3): 330–339.

169.

Sridhar

Chamyal

Patel

(2014) Palaeoflood record of high-magnitude events during historical time in the Sabarmati River, Gujarat. Current Science 107(4): 675.

170.

Sridhar

Laskar

Prasad

, et al. (2015) Late Holocene flooding history of a tropical river in western India in response to southwest monsoon fluctuations: A multi proxy study from lower Narmada valley. Quaternary International 371: 181–190.

171.

Sridhar

Raj

Chamyal

, et al. (2018) Mid to late Holocene fluvio-marine record from the ephemeral rivers of northern alluvial plains of Gujarat, western India. Zeitschrift fur Geomorphologie 62(1): 1–11.

172.

Sridhar

Thakur

Basavaiah

, et al. (2020) Lacustrine record of high magnitude flood events and climate variability during mid to late Holocene in the semiarid alluvial plains, western India. Palaeogeography Palaeoclimatology Palaeoecology 542(April 2019): 109581.

173.

Srivastava

Agnihotri

Sharma

, et al. (2017) 8000-year monsoonal record from Himalaya revealing reinforcement of tropical and global climate systems since mid-Holocene. Scientific Reports 7(1): 1–11.

174.

Staubwasser

Weiss

(2006) Holocene climate and cultural evolution in late prehistoric–Early historic west Asia. Quaternary Research 66(3): 372–387.

175.

Steinhilber

Beer

Fröhlich

(2009) Total solar irradiance during the Holocene. Geophysical Research Letters 36(19): L19704.

176.

Stuiver

Braziunas

(1993) Sun, ocean, climate and atmospheric 14CO2: An evaluation of causal and spectral relationships. Holocene 3(4): 289–305.

177.

Sun

Gui

Chen

(2012) Geochemistry of sandstones from the Neoproterozoic Shijia Formation, northern Anhui Province, China: Implications for provenance, weathering and tectonic setting. Geochemistry 72(3): 253–260.

178.

Taylor

McLennan

(1985) The continental crust: its composition and evolution. Palo Alto, CA: Blackwell Scientific Pub, p.312. Oxford.

179.

Taylor

McLennan

(1995) The geochemical evolution of the continental crust. Reviews of Geophysics 33: 241–265.

180.

Tribovillard

Algeo

Lyons

, et al. (2006) Trace metals as paleoredox and paleoproductivity proxies: An update. Chemical Geology 232(1-2): 12–32.

181.

Walker

Head

Berkelhammer

et al. (2018) Formal ratification of the subdivision of the Holocene Series/Epoch (Quaternary System/Period): two new Global Boundary Stratotype Sections and Points (GSSPs) and three new stages/subseries. Episodes 41(4): 213–223. Available at: http://www.episodes.org/view/2077: DOI: 10.18814/epiiugs/2018/018016.

182.

Wang

Goring

McGuire

(2019) Bayesian ages for pollen records since the last glaciation in North America. Scientific Data 6(1): 1–8.

183.

Wanner

Beer

Bütikofer

, et al. (2008) Mid- to Late Holocene climate change: An overview. Quaternary Science Reviews 27(19-20): 1791–1828.

184.

Warrier

Shankar

(2009) Geochemical evidence for the use of magnetic susceptibility as a paleorainfall proxy in the tropics. Chemical Geology 265(3-4): 553–562.

185.

Wayne Nesbitt

Markovics

(1997) Weathering of granodioritic crust, long-term storage of elements in weathering profiles, and petrogenesis of siliciclastic sediments. Geochimica et Cosmochimica Acta 61(8): 1653–1670.

186.

Willard

Bernhardt

Korejwo

, et al. (2005) Impact of millennial-scale Holocene climate variability on eastern North American terrestrial ecosystems: Pollen-based climatic reconstruction. Global and Planetary Change 47(1): 17–35.

187.

Huang

, et al. (2014) Bacillus qingshengii sp. nov., a rock-weathering bacterium isolated from weathered rock surface. International Journal of Systematic and Evolutionary Microbiology 64(Pt_7): 2473–2479.

188.

Zhao

M-Y

Zheng

Y-F

(2015) The intensity of chemical weathering: Geochemical constraints from marine detrital sediments of Triassic age in South China. Chemical Geology 391: 111–122.

189.

Zielinski

Mayewski

Meeker

, et al. (1994) Record of volcanism since 7000 BC from the GISP2 Greenland ice core and implications for the volcano-climate system. Science 264(5161): 948–952.

190.

Zielinski

Mayewski

Meeker

, et al. (1996) A 110,000-Yr record of explosive volcanism from the GISP2 (Greenland) Ice Core. Quaternary Research 45(2): 109–118.

191.

Zielinski

Mershon

(1997) Paleoenvironmental implications of the insoluble microparticle record in the GISP2 (Greenland) ice core during the rapidly changing climate of the Pleistocene–Holocene transition. Geological Society of America Bulletin 109(5): 547–559.

Supplementary Material

Please find the following supplemental material available below.

For Open Access articles published under a Creative Commons License, all supplemental material carries the same license as the article it is associated with.

For non-Open Access articles published, all supplemental material carries a non-exclusive license, and permission requests for re-use of supplemental material or any part of supplemental material shall be sent directly to the copyright owner as specified in the copyright notice associated with the article.

0.00 MB

0.03 MB