a Mineralogical Analysis of Hspdp Core Samples from the Northern Awash Pliocene Hadar Formation, Ethiopia: the tale of AN East African Paleolake
Abstract
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 (HSPDP), recovering a total of 600 m of sediment from both localities (NAO and NAW). Mineralogical analyses of the bulk sediments and clays from the Hadar Formation have helped to begin constructing a more complete picture of the paleoenvironmental conditions of the Northern Awash during the Pliocene. This work is an attempt to begin to answer the questions about salinity/alkalinity of Hadar Paleolake as well as its sulfur content. The two sites, NAW and NAO, are about 3 kilometers apart and presumably part of the same paleolake basin. The data has shown that this area was much more humid during the Pliocene than it is today and that most of the minerals in the paleolake basin are detrital, save for calcite, Mg-calcite, gypsum, pyrite, and a few zeolites. 060 analyses of the clays in the cores show that the lake was a freshwater lake three million years ago, up until its eventual evaporation. Interestingly, the lack of trioctahedral clays is an indication that the lake water did not become highly saline and alkaline during its evaporation. An interesting contrast between the two cores shows that NAO contains gypsum, but 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 line of evidence suggests that the two sites within the lake may have experienced different redox conditions. It may be that the NAO core was sampled in a shallower part of the lake whereas the NAW core sampled a deeper section.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2017
- Bibcode:
- 2017AGUFMPP13B1081D
- Keywords:
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- 0444 Evolutionary geobiology;
- BIOGEOSCIENCES;
- 1051 Sedimentary geochemistry;
- GEOCHEMISTRY;
- 1165 Sedimentary geochronology;
- GEOCHRONOLOGY;
- 9604 Cenozoic;
- INFORMATION RELATED TO GEOLOGIC TIME