Archaeological Sites Linked to Dry Period Focusing of Groundwater in River Bed Water Holes, New Insights from High-Resolution Climate Records, Olduvai Gorge
Abstract
Determining why an archaeological site is located exactly where it is, in space and in time, is crucial to accurate interpretation of the site. Geological mapping of sedimentary deposits of the BK area of Olduvai Gorge and the dating of intercalated volcanics permit interpretation of the paleoenvironment context of the BK and BK-E archaeological sites and their correlation with a time period of an enhanced wet/dry climate cyclicity ( 20,000 yrs). The stratigraphy is comprised primarily of subparallel to lensoidal volcaniclastic fine sediments and intercalated tuffs deposited in a low-gradient fluvial-deltaic system that discharged into a shallow playa. The delta supported a large groundwater-fed wetland separated by distributary channels. Coarse-grained channels of sandy-gravel cross beds punctuate the stratigraphy. This sedimentary sequence faithfully tracks the climate cyclicity with the flat lying fluvial/deltaic/playa deposits accumulating during wet phases while the channels recorded fluvial incision (related to drop in base level) during the dry phases.
The archaeological sites, BK and BK-E occur in incised channels and thus were formed during dry periods. Bones and stone-rich layers are interbedded with fluvial sediments suggesting the site was used repeatedly. The BK site contains a rich record of tools, vertebrate fossils of small, middle-sized and large animals, 24 Pelorvis Oldowayensis skeletons and (OH 80 Paranthropus boisei). Meat and marrow exploitation were reconstructed using the taphonomic signatures left on bones by hominins. Cut-marked bones and tools show little to no evidence of fluvial transport suggesting animals were butchered in place. Bones were commonly encrusted in carbonate (-4 δO18 PDB) likely from evaporating groundwater. The evidence for site location suggests a groundwater-sourced water holes located in the distal end of a delta distributary channel that was used during dry times for passive scavenging or hunting by hominins.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMPP31B1659A
- Keywords:
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- 0439 Ecosystems;
- structure and dynamics;
- BIOGEOSCIENCESDE: 1041 Stable isotope geochemistry;
- GEOCHEMISTRYDE: 1105 Quaternary geochronology;
- GEOCHRONOLOGYDE: 9605 Neogene;
- INFORMATION RELATED TO GEOLOGIC TIME