In May of 2017 we initiated a study of the sediments of Naihehe Cave, which is a large solution cave that lays approximately 200 m south of the site of Qaraqara. Preliminary survey of the cave in 2013, 2014, and 2015 identified a large bank of sediment in the cave that had visible layers of charcoal embedded in the strata. After consulting with the traditional owners of the cave (the Sawaii mataqali of Koronisagana village), and the local land owner (Vili Valanamua), we asked for permission to conduct a series of investigations inside the cave that would include survey, excavation, and the collection of sediment samples. Our goal was to determine if the cave preserved a long record of sedimentation that matched that of Qaraqara (2500+ years), and if cultural deposits of similar antiquity were present. We also wished to determine the depositional context and history of the cave, as these processes may inform on local climate and biogeography in the past. To meet these goals, we planned a series of excavations that would collected samples of sediment for later analysis, and also the collection of cultural materials, including charcoal, which could be used for radiocarbon dating. These analyses were directed and conducted by MA student Kyle Riordan from Ohio State University.
Several banks of sediment were evident along the floor of the cave, and our investigations were focused on these banks. We hypothesized that these sediments resulted from water percolating through the cave, or from the erosion of the limestone over time, forming drifts of sediment at the bottom of an underground lake. We also hypothesized that these deposits may be organic in origin, and formed by the droppings of nesting bats and birds. In order to discern their origins, we performed two excavations atop the sediment banks. The first, Test Unit 1 (TU1) was located on the southern side of the sediment bank in the largest chamber. The second, Test Unit 2) was located within a small alcove just inside the entrance to the cave, but just beyond the reach of daylight.
The laboratory investigation is still in the process of being completed and interpreted. This includes a geoarchaeological study of grain size from the identified strata, loss-on-ignition analysis in order to determine carbonate and organic content, pH, and instrument analysis including scanning electron microscopy, laser ablation inductively coupled mass spectometry, and radiocarbon dating. These analyses will reveal what the sediment in the cave is composed of, how it was deposited, and how how and when humans were active in the cave.