Extensive coastal and estuarine plains, associated with several large seasonal rivers, characterize the southern shore of van Diemen Gulf, Northern Territory, Australia. The Mary River is unique among these rivers in that, despite a catchment of 7700 km2, it fails to reach the sea as a discrete channel but breaks up into a series of terminating, multiple channels, leaving much of the freshwater discharge to evaporate from the plains. The extent and morphology of these plains have changed markedly during the Holocene. Drilling, radiocarbon dating and pollen analysis indicate a transgressive phase that began about 7000 years ago as the rising seas flooded the prior valley. This was followed by a big swamp phase as sea level stabilized around 6000 years ago, during which widespread mangrove forest development occurred. Rapid progradation of the coast occurred between 6000 and 4000 years BP. The shoreline has prograded little since that time, but has been modified by episodic chenier ridge deposition and palaeochannel abandonment, infill and reoccupation. The lower Mary River differs from adjacent systems in that several former estuarine channels across the plains appear to have become completely blocked with sediment, leaving low-lying billabongs and palaeochannels which have been preferentially reinvaded by later channels. Several alternative explanations are examined, but it remains unclear what has driven major variations in palaeochannel activity and sedimentation during the mid-Holocene, and why these have decreased so markedly in the last 2000 years.
Applegate, R. 1990: Landcare – a case study on the coastal plain . Environment 90 Conference, Conservation Commission of the Northern Territory, Darwin, 4.29–4.33 .
2.
Chappell, J.1990: Some effects of sea level rise on tropical riverine lowlands. In Bishop, P. , editor, Lessons for human survival: Nature's record from the Quaternary, Geological Society of Australia Symposium Proceedings 1, 37–49.
3.
Chappell, J.1993: Contrasting Holocene sedimentary geologies of the Daly River, northern Australia, and lower Sepik-Ramu, Papua New Guinea . Sedimentary Geology83, 339–358 .
4.
Chappell, J. and Grindrod, J.1984: Chenier plain formation in northern Australia. In Thom, B.G. , editor, Coastal geomorphology in Australia, Sydney: Academic Press , 197–231.
5.
Chappell, J. and Grindrod, J.1985: Pollen analysis: key to past mangrove communities and successional changes in North Australian coastal environments. In Bardsley, K.N. , Davie, J.D.S. and Woodroffe, C.D. , editors, Coasts and tidal wetlands of the Australian Monsoon region, North Australia Research Unit Monograph, 225–231.
6.
Chappell, J. and Thom, B.G.1986: Coastal morphodynamics in North Australia: review and prospect . Australian Geographical Studies24, 110–127 .
7.
Chappell, J. and Woodroffe, C.D.1985: Morphodynamics of Northern Territory tidal rivers and floodplains. In Bardsley, K.N. , Davie, J.D.S. and Woodroffe, C.D. , editors, Coasts and tidal wetlands of the Australian Monsoon region, North Australia Research Unit Monograph, 85–96.
8.
Chappell, J. , Rhodes, E.G. , Thom, B.G. and Wallensky, E.1982: Hydro-isostasy and the sea level isobase of 5500 BP in North Queensland . Marine Geology49, 81–90 .
9.
Clark, R.L. and Guppy, J.C.1988: A transition from mangrove forest to freshwater wetland in the monsoon tropics of Australia . Journal of Biogeography15, 665–684 .
10.
Clark, M.F. , Wasson, R.J. and Williams, M.A.J.1979: Point Stuart chenier and Holocene sea levels in Northern Australia . Search10, 90–93 .
11.
Crowley, G.M. and Gagan, M.K.1995: Holocene evolution of coastal wetlands in wet-tropical northeastern Australia . The Holocene5, 385–399 .
12.
Finlayson, C.M. and Woodroffe, C.D.1996: Wetland vegetation, In Finlayson, C.M. and von Oertzen, I. , editors, Landscape and vegetation ecology of the Kakadu region, Northern Australia, Dordrecht: Kluwer , 81–112.
13.
Gould, H.R. and McFarlan, E.1959: Geologic history of the chenier plain, southwestern Louisiana . Transactions of the Gulf Coast Association of Geological Societies9, 261–272 .
14.
Grindrod, J.1988: The palynology of Holocene mangrove and saltmarsh sediments, particularly in northern Australia . Review of Palaeobotany and Palynology55, 229–245 .
15.
Gupta, S.K. and Polach, H.A.1979: Radiocarbon dating practices at ANU. Radiocarbon Dating Laboratory, Research School of Pacific Studies, Australian National University, Canberra .
16.
Head, L.1996: Rethinking the prehistory of hunter-gatherers, fire and vegetation change in northern Australia . The Holocene6, 481–487 .
17.
Hope, G. , Hughes, P.J. and Russell-Smith, J.1985: Geomorphological fieldwork and the evolution of the landscape of Kakadu National Park. In Jones, R. , editor, Archaeological research in Kakadu National Park, ANPWS Spec. Pub. 13, 229–240.
18.
Jennings, J.N.1975: Desert dunes and estuarine fill in the Fitroy estuary (northwestern Australia) . Catena2, 215–262 .
19.
Jones, B.G. , Martin, G.R. and Senapati, N.1993: Riverine-tidal interactions in the monsoonal Gilbert River fandelta, northern Australia . Sedimentary Geology83, 319–337 .
20.
Kershaw, A.P. 1983: The vegetation record of northeastern Australia , 7±62 ka, In Chappell, J. and Grindrod, A. , editors, Proceedings of first CLIMANZ conference, ANU Press, 100-100 .
21.
Kingston, D.1991: Hydrology of the northern wetlands. In Haynes, C.D. , Ridpath, M.G. and Williams, M.A.J. , editors, Monsoonal Australia: landscape, ecology and man in the northern lowlands, Rotterdam: Balkema , 31–35.
22.
Knighton, A.D. , Mills, K. and Woodroffe, C.D.1991: Tidal-creek extension and saltwater intrusion in northern Australia . Geology19, 831–834 .
23.
Knighton, A.D. , Woodroffe, C.D. and Mills, K.1992: The evolution of tidal creek networks, Mary River, Northern Australia . Earth Surface Processes and Landforms17, 167–190 .
24.
Lees, B.G.1987: Age structure of the Point Stuart chenier plain: reassessment . Search18, 257–259 .
25.
Lees, B.G.1992: Geomorphological evidence for late Holocene climatic change in northern Australia . Australian Geographer23, 1–10 .
26.
Lees, B.G. and Clements, A.1987: Climatic implications of chenier dates in Northern Australia . Radiocarbon29, 311–317 .
27.
Lonsdale, W.M.1988: Litter fall in an Australian population of Mimosa pigra, an invasive tropical shrub . Journal of Tropical Ecology4, 381–392 .
28.
McAlpine, J.R.1969: Climate of the Adelaide-Alligator area. In Story, R. et al., editors, Lands of the Adelaide-Alligator area, Northern Territory, CSIRO Land Research Series No. 25, 49–55.
29.
Nanson, G.C. , East, T.J. and Roberts, R.G.1993: Quaternary stratigraphy, geochronology and evolution of Magela Creek catchment in the monsoonal tropics of northern Australia . Sedimentary Geology83, 277–302 .
30.
Nott, J. and Price, D.M.1994: Plunge pools and paleoprecipitation . Geology22, 1047–1050 .
31.
Nott, J.F. , Price, D.M. and Bryant, E.A.1996: A 30,000 year record of extreme floods in tropical Australia from relict plunge-pool deposits: implications for future climate change . Geophysical Research Letters23, 379–382 .
Rhodes, E.G.1982: Depositional model for a chenier plain, Gulf of Carpentaria, Australia . Sedimentology29, 201–221 .
34.
Roberts, R.G. 1991: Sediment budgets and Quaternary history of the Magela Creek Catchment, Tropical Northern Australia. Unpublished PhD thesis, University of Wollongong.
35.
Roy, P.S.1984: New South Wales estuaries: their origin and evolution. In Thom, B.G. , editor, Coastal geomorphology in Australia, Sydney: Academic Press , 99–122.
36.
Roy, P.S. , Thom, B.G. and Wright, L.D.1980: Holocene sequences on an embayed high-energy coast: an evolutionary model . Sedimentary Geology26, 1–19 .
37.
Russell-Smith, J.1985: A record of change: studies of Holocene vegetation history in the South Alligator River region, Northern Territory . Proceedings of the Ecological Society of Australia13, 191–202 .
38.
Stuart-Smith, P.G. , Wallace, D.A. and Roarty, M.J.1984: 1:100,000 Geological Commentary. Mary River – Point Stuart Region, Northern Territory, Northern Territory Geological Survey, Govt. Printer, Darwin .
39.
Vertessey, R. 1990: Morphodynamics of macrotidal rivers in far northern Australia. PhD thesis, ANU.
40.
Wasson, R.J. , editor, 1992: Modern sedimentation and late Quaternary evolution of the Magela Creek Plain. Supervising Scientist for the Alligator Rivers Region, Research Report 6, 322-322 pp.
41.
Webster, P.J. and Streeten, N.A.1978: Late Quaternary Ice Age climates of tropical Australasia: interpretations and reconstructions . Quaternary Research10, 279–309 .
42.
Whitehead, P.J. , Wilson, B.A. and Bowman, D.M.J.S.1990: Conservation of coastal wetlands of the Northern Territory of Australia: the Mary River floodplain . Biological Conservation52, 85–111 .
43.
Williams, M.A.J.1973: The efficiency of creep and slope wash in tropical and temperate Australia . Australian Geographical Studies11, 62–78 .
44.
Williams, M.A.J.1976: Erosion in the Alligator Rivers area. In Story, R. et al., editors, Lands of the Alligator Rivers area, Northern Territory, CSIRO Land Reserch Series 38, 112–125.
45.
Williams, M.A.J.1991: Evolution of the landscape. In Haynes, C.D. , Ridpath, M.G. and Williams, M.A.J. , editors, Monsoonal Australia: landscape, ecology and man in the northern lowlands, Rotterdam: Balkema , 5–17.
46.
Woodroffe, C.D. and Mulrennan, M.E.1993: Geomorphology of the Lower Mary River plains, Northern Territory. Australian National University North Australia Research Unit and the Conservation Commission of the Northern Territory, Monograph .
47.
Woodroffe, C.D. , Chappell, J. , Thom, B.G. and Wallensky, E.1986: Geomorphological dynamics and evolution of the South Alligator tidal river and plains, Northern Territory. North Australia Research Unit Monograph, 190.
48.
Woodroffe, C.D. , Chappell, J. , Thom, B.G. and Wallensky, E.1989: Depositional model of a macrotidal estuary and floodplain, South Alligator River, Northern Australia . Sedimentology36, 737–756 .
49.
Woodroffe, C.D. , Mulrennan, M.E. and Chappell, J.1993: Estuarine infill and coastal progradation, southern van Diemen Gulf, northern Australia . Sedimentary Geology83, 257–275 .
50.
Woodroffe, C.D. , Thom, B.G. and Chapell, J.1985: Development of widespread mangrove swamps in mid-Holocene times in northern Australia . Nature317, 711–713 .
51.
Woodroffe, C.D. , Thom, B.G. , Chappell, J. , Wallensky, E. , Grindrod, J. and Head, J.1987: Relative sea level in South Alligator River region, North Australia, during the Holocene . Search18, 198–200 .
