GEOSPATIAL ANALYSIS OF THE GEOLOGY AND FAUNAL COMMUNITIES OF THE TOPERNAWI LOCALITY IN NORTHERN TURKANA, KENYA

Topernawi is a middle Oligocene locality within the Ekitale Basin, located on the Western rift shoulder of the northern Turkana Depression (Kenya). The locality has been dated to ∼29.3+0.08Ma, and more than 500 vertebrate specimens have been recovered from 19 sites identified within the locality. The geomorphology of the Ekitale Basin is primarily controlled by tectonic structures and is bordered by N40º-50º normal faults characterized by intrusive and cross-cutting volcanic dikes. The Murue-rith fault is one of the major normal faults separating the Topernawi Formation from the Plio-Pleistocene of the Nachukui Formation. Previous geological studies have identified the basin's base as thick basaltic lava flows with columnar jointing in some places. Five stratigraphic intervals were mapped of which two have yielded most of the fossil specimens (Units1 through 5, oldest to youngest).

Here, we aim to describe and quantify the faunal spatial distribution by site and within their distinct stratigraphic unit, show species richness, diversity, geological discrepancy as well as their contextual relationship within the locality. Eight fossil sites are each spatially distributed in Unit 3 and 4, and only two sites can be found in Unit 5. Fossil sites from Units 3 and 4 can be combined into Northern (Unit 4), Central (Unit 4), and Southern (Unit 3) aggregates for faunal analysis. Hyracoids dominate each aggregate (44.7-63.8%) but are best represented in the South (63.8%),whereas primates are most common in the Central aggregate (9.5%). Based on preliminary data, the fossil assemblages of the Topernawi Formation have important implications for Oligocene mammal biogeography and evolution.