Late-Holocene sea-level changes in south and southwest Iceland reconstructed from littoral molluscan stratigraphy

Abstract

Sediments deposited during late-Holocene rise in sea level have been found in the Stokkseyri Eyrarbakki (Flói) area of south Iceland. At Stokkseyri, marine littoral sediments containing a thermophilic intertidal faunal assemblage, mainly consisting of gastropods, bivalves and barnacles with a few polychaets, bryozoans and echinoids, have been encountered behind the present storm beach a short distance from the sea. The shell layers are up to 4 m in thickness and reach up to 6 m above the present sea level and 300 m inland. During the late-Holocene sea-level rise, the sea brought sediments and shell material from the coast into a lagoon behind the ridge where it accumulated on former bog layers, during two transgressive tendencies separated by a short regressive tendency. The ages of the two transgressive tendencies are apparently 2600-2800 and 2200-2400 'C years BP, respectively. Then, after the sea retreated, a thin soil layer formed on top of the marine series. Marine sediments of late-Holocene age containing thermophilic littoral species, which have been found in peat layers in the tidal zone of Gardskagi, Reykjanes, southwest Iceland, were deposited during a sea-level rise 3200 years ago. Thus, there are sporadic occurrences of sediments with thermophilic marine fauna of late-Holocene age along the Icelandic south and southwest coast, especially in sheltered places. The mollusc stratigraphy reveals three short periods with a rise in sea level during the late Holocene, 3200-2200 cal. years BP. The calculated sea-level index points indicate an average 'long-term' trend of sea-level rise as high as 2.11 mm/yr during this period in south and southwest Iceland. There are no indications of crustal subsidence occurring in the area at the same time.

Keywords

Sea-level change marine transgression late Holocene littoral thermophilic mollusc fauna south and southwest Iceland

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References

Allen, J.R.L. 1999: Geological impacts on coastal wetland landscapes: some general effects of sediment autocompaction in the Holocene of northwest Europe . The Holocene 9, 1-12 .

Andersen, G.J. , Heinemeier, J. , Nielsen, H.L. , Rud, N. , Johnsen, S. , Sveinbjornsdóttir, A.E. and Hjartarson, A. 1989: AMS 'C dating on the Fossvogur sediments, Iceland . Radiocarbon 31, 592-600 .

Aronson, J.L. and Saemundsson, K. 1975: Relatively old basalts from structurally high areas in Central Iceland . Earth and Planetary Science Letters 28, 83-97 .

Askelsson, J. 1935: Some remarks on the distribution of the species Zirphaea crispata L. and Purpura lapillus L. on the north coast of Iceland . Videnskabelige Meddelelserfra dansk naturhistorisk Forening 99, 65-72 .

Bairdarson, G.G. 1906: Purpura lapillus L. i haevede Lag paa Nordkysten af Island . Videnskabelige Meddelelser fra dansk naturhistorisk Forening 58, 177-185 .

Bairdarson, G.G. 1910: Maerker efter Klimaog Niveauforandringer ved Hdnaflói i Nord-Island . Videnskabelige Meddelelser fra dansk naturhistorisk Forening 62, 35-79 .

Bruun, P. 1986: Sedimentary balances land and sea with special reference to the Icelandic south coast from Thorlakshbfn to Dyrholaey: river nourishment of shores practical analogies on artificial nourishm. In Sigbjarnarson, G. , editor, Icelandic coastal and river symposium, Proceedings, Reykjavfk: University of Iceland, Icelandic Harbour Authority, National Energy Authority, National Power Company, Marine Research Institute, Public Roads Administration , 17-32.

Einarsson, A. and Bjarnadóttir, S. 1992: Saga lifrfkis f Tjorninni. In Nielsen, O.K. , editor, Tjornin: Saga og Iffrilki, Reykjavik: Reykjavikurborg , 19-30.

Einarsson, P. 1994: Crustal movements and relative sea level changes in Iceland. In Viggosson, G. , editor, Proceedings of the Hornafjordur International Coastal Sytnposium at Hofn, June 20-24, 1994, Reykjavik: Organizing Counmnittee of the Symnposiun , 23-34.

10.

Einarsson, T. 1970: Fjorumórinn a Gardskaga . Ndtttirufraedingurinn 40(2), 134-135 .

11.

Gehrels, W.R. 1999: Middle and Late Holocene sea-level changes in eastem Maine reconstructed from foraminiferal saltmarsh stratigraphy and AMD '4C dates on basal peat . Quaternary Research 52, 350-359 .

12.

Hansom, J.D. and Briggs, DJ. 1991: Sea-level change in Vestfirdir, north west Iceland. In Maizels, J.K. and Caseldine, J. , editors, Environmental changes in Iceland: Past and present, Dordrecht: Kluwer , 79-91.

13.

Hjartarson, A. 1988: Thjórsarhraunid mikla staersta nutimahraun jardar . Natturufraedingurinn 58(1), 1-16 .

14.

Hjartarson, A. and Ingolfsson, O. 1988: Preboreal glaciation of southern Iceland . Jokull 38, 1-5 .

15.

Imsland, P. and Einarsson, T. 1991: Sjavarflód d Eyrarbakka og Stokkseyri. Raunvfsindastofnun Hdskolans RH-01-91, 1-71.

16.

Ingolfsson, O. , Norddahl, H. and Haflidason, H. 1995: Rapid isostatic rebound in southwestern Iceland at the end of the last glaciation . Boreas 24, 245-259 .

17.

John, B. 1975: Marine mollusca from Vestfirdir strandlines . Durhamn University. Vestfirdir Project. 1975 Fieldwork Report and Research Notes, 41-45 .

18.

Jóhannesson, H. and Saemundsson, K. 1998: Geological map of Iceland. 1:500000. Bedrock geology (second edition). Reykjavik: Ndttdrufraedistofnun Islands og Landmaelingar Islands .

19.

Jónsson, J. 1957: Notes on changes of sea-level on Iceland . Geografiska Annaler 2-3, 143-212 .

20.

Kjartansson, G. 1943: Arnesinga saga I: Nttuirulysing Arnessyslu. Reykjavlfk: Arnesingafelagid , 268 pp.

21.

Kjartansson, G. , Thórarinsson, S. and Einarsson, T. 1964: C '4 aldursakvardanir a synishornum vardandi fslenzka kvarterjardfraedi . Ndtturufraedingurinn 34(3), 97-145 .

22.

Morner, N.A. 1980a: Late Quaternary sea-level changes in north-western Europe: a synthesis . Geologiska Foreningens i Stockholm Forhandlingar 100(4), 381-400 .

23.

Morner, N.A. 1980b: The northwest European 'ea-level laboratory' and regional Holocene eustasy . Palaeogeography, Palaeoclimatology, Palaeoecology 29 (1979/1980), 281-300

24.

Peltier, W.R. and Tushingham, A.M. 1989: Global sea level rise and the greenhouse effect: might they be connected? Science 244, 806-810 .

25.

Peltier, W.R. and Tushingham, A.M. 1991: Influence of glacio-isostatic adjustment on tide gauge measurements of secular sea level change . Journal of Geophysical Research 96, 6779-6796 .

26.

R6bertsdóttir, B. 1992: Forsoguleg gjóskulog fra Kotlu, adur nefnd 'Katla 5000'. Vorradstefna Jardfraedafelags Islands 1996. Agrip erinda og veggspjalda, 8-9.

27.

Shennan, I. 1987: Holocene sea-level changes in the North Sea Region. In Tooley, M.J. and Shennan, I. , editors, Sea-level changes, Norwich: Blackwell , 109-151.

28.

Sigmundsson, F. 1990: Seigia jardar undir Islandi, samanburdur lt?kanreikninga vid jardfraedileg gogn. MSc thesis. Reykjavik: University of Iceland, 121 pp.

29.

Skaftadóttir, T. 1974: Um tvo frjolinurit af Rosmhvalanesi og agrip af jardsogu thess. BS thesis. Reykjavik: University of Iceland, 17 pp.

30.

Vilmundardottir, E. 1977: Tungnarhraun: Jardfraediskyrsla Orkustofnun, Raforkudeild. OS ROD 7702, 1-156.