A MINERALOGICAL ANALYSIS OF HSPDP CORE SAMPLES FROM THE NORTHERN AWASH: RECORD OF AN EAST AFRICAN PALEOLAKE FROM THE PLIOCENE HADAR FORMATION, ETHIOPIA

The Northern Awash Valley is located in the southwestern portion of the Afar Depression in Ethiopia. During the 2014 field season, two core sites were drilled as part of the Hominin Sites and Paleolakes Drilling Project, recovering a total of ~600 m of sediment from both localities (NAO and NAW). Mineralogical analyses of the bulk sediments and clays in the Hadar formation have helped to begin constructing a more complete picture of the paleoenvironmental conditions of the Northern Awash during the Pliocene. The two sites are about 3 kilometers apart and likely were in the same paleolake basin. Most of the minerals in the core samples are detrital, save for calcite, Mg-calcite, gypsum, pyrite, and a few zeolites. The detrital mineralogy suggests relatively fresher water conditions in the Pliocene, compared to the modern. 060 analyses of the clays in NAW/NAO show dominantly Al-rich dioctahedral clays, an indication that the lake water did not become highly saline and alkaline during its evaporation. Many NAO core samples contain gypsum, and so far, no pyrite. NAW, on the other hand, contains both pyrite and gypsum. The pyrite in NAW is mostly at the bottom of the core, whereas, the gypsum is intermittent throughout the core and much more sparse toward the bottom. This suggests that the two sites within the paleolake experienced different post-depositional redox conditions. It may be that NAO was in a more shallow part of the lake and NAW was in the deeper section. These data are contributing to our understanding of Pliocene salinity/alkalinity as well as the sulfur cycling in the Hadar Formation paleolake.