Identification of reworked foraminifera in temperate carbonate sediments - A pilot study from the Coorong Coastal Plain, southern Australia

摘要

The extent of aspartic acid and valine racemization (total hydrolysable amino acids) in single tests of the benthic foraminifer Lamellodiscorbis dimidiatus is examined as a potential method for identifying remanie fossils within temperate, bioclastic carbonate sediments. The foraminifer Lamellodiscorbis dimidiatus is a physically robust species capable of withstanding reworking from weathered calcarenites, and has the potential to experience multiple sedimentary cycles of deposition and erosion with subsequent inclusion in younger sedimentary units. The extent of racemization measured in single tests of Lamellodiscorbis sp., reveals that the skeletal carbonate sand sampled from the modern foreshore at Long Beach, Guichen Bay, southern Australia, contains foraminifera ranging in age, from modern individuals, to specimens of late Holocene and Late Pleistocene age. The age of individual foraminifer, however, cannot easily be distinguished based on their taphonomic appearances. The AAR data for Lamellodiscorbis sp., imply that a significant proportion of the skeletal carbonate constituents within the calcarenites of the Coorong Coastal Plain represent reworked bioclasts. The reworked sedimentary constituents within younger sediments, has resulted from the erosion of older calcarenites during glacial cycles.