Sedimentology and Palaeoenvironmens of Holocene Coastal Lakes, Southeastern South Australia

Alan J. Brenchley and Victor A. Gostin

The stranded Pleistocene coastal dune system of southeastern South Australia provides a uniquely preserved record of Quaternary sea level and environmental change. Between the youngest Pleistocene dunes a series of Holocene lakes has formed on the slowly uplifting coastal plain. Holocene sea-level rise produced a protected, lagoonal environment within this interdunal corridor. This study involves lakes to the south of the well documented Coorong Region.

Lakes between Robe and Beachport reveal three distinct environments of Holocene lacustrine sedimentation. Type 1 Lakes have developed within the main interdunal corridor and possess a well developed lagoonal stratigraphy. A thin sequence of lacustrine sediments overlies this lagoonal sequence following a relative fall of sea-level. Type 2 Lakes represent sedimentation within a more restricted marine environment. They began as small lagoonal embayments within the Pleistocene dune and developed a significant saline and fresh water lacustrine stratigraphy following their isolation by sea-level fall or spit accretion. Type 3 Lakes were never connected to the interdunal lagoon and thus possess no marine biota within their sediments.

Selected recently dated cores from each environment are discussed in terms of mineralogy, organic geochemistry and ostracodal / foraminiferal assemblages to provide an analysis of the sedimentary response to varying climatic conditions throughout the latter half of the Holocene Period.

AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California