Late Holocene Environmental Changes On Kurnell Peninsula, NSW Adrian G. Johnson (Communicated by H. MARTIN) Johnson, A.G. Late Holocene environmental changes on Kurnell Peninsula, New South Wales. Proc. Linn. Soc. 114(3): 119-132(1994). Studies of stratigraphy, mineral magnetic characteristics, organic matter, selected cation, pollen and charcoal abundances were used to reconstruct environmental changes from three perched swamps on Kurnell Peninsula, NSW (151°13 ' E, 34°02 ' S). Swamp sediments began accumulating between 2400 and 1680 years ago. Organic matter collected in these depressions continuously as vegetation communities developed on the newly formed Holocene dunes. Periods of mineral sediment supply from eroding catchments and oceanic influx punctuated this organic build-up. An increase in charcoal input into the sediments was noted for the period 1040-200 years Before Present, most probably due to Aboriginal burning. This was accompanied by an increase in the abundance of sclerophyllous vegetation species. Since European settlement, increasing catchment erosion, increased turbidity of swamp waters, an altered fire regime, and a greater supply of magnetic aerosols have occurred. A. G. Johnson, School of Geography, University of NSW, P.O. Box 1, Kensington, Australia 2033; manuscript received 19 January 1993, accepted for publication 23 June 1993. Introduction The fundamental method of identifying past physical changes from swamp profiles is stratigraphic — aided by sedimentological, petrographic, palaeontological, geomorphic and geochemical studies (Chappell, 1978). Therefore, a multi-disciplinary approach to the analysis of environmental change is desirable for quantifying past changes. This study draws on a number of techniques to reconstruct a history of environmental conditions on Kurnell Peninsula during the last 2400 years. Study Area Kurnell Peninsula forms the southern shore of Botany Bay, about 12 km south of Sydney (Fig. 1). It is a unique cultural resource because of its historical significance, its importance for recreational and scientific purposes, its value as a source of extractive materials and the site for many manufacturing industries. The current climate of the study area is temperate coastal. However, due to the rugged topography of the Kurnell Headland, and its coastal location, many micro-climates result. The region experiences warm to hot summers and mild winters. Average annual rainfall is 1100 mm, most of which falls in the period January to June. Rainfall occurs approximately 130 days per year. Prevailing winds are from the south east during summer and autumn, and the west during winter (Bureau of Meteorology). During the Early Holocene, when sea level rose to between 9 and 20 m below its present level, marine sands were reworked from the Pleistocene marine substrata and washed into the near-shore zone to form spits and beach ridges. Tidal deltaic deposits issued from the Georges River and Port Hacking Estuary. These sediments and those supplied by littoral drift from further south were deposited between Port Hacking Point and Kurnell Headland (island) to form a proto-barrier. This material was to be later reworked across Bate Bay to form the present day Kurnell Isthmus. Activity had probably ceased by the Late Holocene (Roy and Crawford, 1979; Hann, 1986). Urwin (1980) described five land units for the study area (Fig. 1). The Bedrock PkOC. LINN. Soc. N.S.W., 114(3), 1994
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