Holocene distribution and amino acid racemisation of the benthic foraminiferMassilina milletti, northern Spencer Gulf, South Australia

Abstract

The benthic foraminifer Massilina milletti increases numerically with increasing depth of water in northern Spencer Gulf. In contrast, Cribrobulimina mixta, Nubecularia lucifuga, Peneroplis planatus and Discorbis dimidiatus are more characteristic of shallow water. Vibrocore #198 recovered a section of Quaternary sediments from one of the deepest parts (c. 20 m) of northern Spencer Gulf. The distribution of benthic foraminifera in the upper 1.5 m of this core records the Holocene transgression and indicates continuous sedimentation since c. 8,000 radiocarbon years B.P. Amino acid racemisation values for samples of Massilina milletti taken from core #198 are generally consistent with their depth in core. The D/L ratio, taken as an indicator of age, increases with depth. Anomalously high D/L values for the sample from 27–29 cm depth are attributed to slumping and reworking of Lower Holocene sediments, apparently initiated by a sudden seismic event c. 1,700 radiocarbon years B.P.