A microstratigraphic reevaluation of the Florisbad spring site, Free State Province, South Africa: Formation processes and paleoenvironment

The Florisbad spring site has produced a large collection of fossil bones dating to the Middle Pleistocene and several assemblages of Middle Stone Age (MSA) artifacts. The species featured in the faunal collection define the Florisian Land Mammal Age, characterized mainly by grazing ungulates that reflect an open grassland environment. Early MSA artifacts found within the basal layers represent the earliest evidence of human presence at Florisbad, followed by an intact MSA occupation horizon characterized by stone tools and animal bones, in direct association and primary context. These fossils and artifacts were found embedded within sand and peat layers. Previous studies investigated the genesis of such deposits using field descriptions and bulk sedimentological analyses. However, sediments were never studied within their original context, thus leading to difficulties in determining the formation processes of the deposits. Using a multianalytical micro-geoarchaeological approach including sediment micromorphology, FTIR and XRD, we were able to show that the site is characterized by alternating aeolian sand layers reworked by lacustrine water during the wet phases of the Pleistocene, and peat layers formed in marshes during dry phases. The results confirm most of the previous paleoenvironmental reconstructions and provide a refined stratigraphic sequence of the site.