Initial micromorphological results from Liang Bua, Flores (Indonesia): Site formation processes and hominin activities at the type locality of Homo floresiensis

Liang Bua, a karstic cave located on the island of Flores in eastern Indonesia, is best known for yielding the holotype of the diminutive hominin Homo floresiensis from Late Pleistocene sediments. Modern human remains have also been recovered from the Holocene deposits, and abundant archaeological and faunal remains occur throughout the sequence. The cave, the catchment in which it is located and the gross aggradational phases of the sediment sequence have all been subject to a great deal of scientific scrutiny since the discovery of the holotype of H. floresiensis in 2003. A recent program of geoarchaeological research has extended analyses of the site's deposits to the microstratigraphic (micromorphological) level. The stratigraphic sequence in the cave is well defined but complex, comprising interstratified sediments of diverse lithologies and polygenetic origins, including volcanic tephras, fine-grained colluvium, coarse autogenic limestone gravels, speleothems and anthropogenic sediments, such as combustion features. The sedimentological and chemical heterogeneity suggest that processes of site formation and diagenesis varied markedly through time, both laterally and vertically. We present initial results from samples collected in 2014 from an excavation area near the rear of the cave, which yielded radiocarbon ages from charcoal that fill an important temporal gap in the chrono-stratigraphic sequence of previously excavated areas of the site. The results indicate marked changes in site environment and hominin activity during the Late Pleistocene, relating primarily to the degree to which the cave was connected to the hydrogeological system and to the varying intensities of use of the cave by hominins. Importantly, we identify anthropogenic signs of fire-use at the site between 41 and 24 thousand years ago, most likely related to the presence of modern humans.