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Week 3: ESA Archaeological research in East Africa: new data & new questions

Map of East African early hominid sites

Work began at Olduvai Gorge

• discovery of Zinjanthropus skull by Mary Leakey in 1959

Burial in lake and river sediments = potential data for understanding hominid activity patterns

Multiple methods for DATING:

• Correlations based on long sequences at Omo and Olduvai
• Biostratigraphy
• Paleomagnetism
• Tephra-chronology (correlation of volcanic ashes)
• Radiometric dating possible on volcanic sediments
  • e.g. K/Ar technique (1.3 by half life... K40 decays to Ar40) During volcanic eruption, all argon expelled from minerals and "clock" set to zero:

Example: Turkana Basin sites (northern Kenya and Ethiopia):

• Omo, Shungura Formation (north of Lake Turkana)
  • Long sequence of tuffs good for dates and biostratigraphy
  • Big channel sediments break up fossils and move artifacts... lots of tooth fossils, but little else
• East Turkana (e.g. Koobi Fora site of KBS and KNM-ER 1470 fossil locality)
  • Sequence broken up / interrupted by erosion
  • Context: quiet water streams and lake margins
  • Great preservation of archaeology & hominids... complete skulls found
• West Turkana

KBS Tuff dating controversy

First season at Turkana in 1969 found first A. boisei skull + early Homo + tools embedded in volcanic ash by Kay Behrensmeyer called "KBS tuff" The the "1470" skull identified as Homo habilis was found at a locality buried just below the KBS tuff.

KBS site and HAS site associated with it (about 1 km apart)

Feldspar from tuff dated by Fitch and Miller with K/Ar and Ar/Ar to 2.42 mya , then 2.6 + 0.26 my

(later presented 41 separate age determinations, ranging from 223 my to 0.91 only 7 close to original)

Basil Cooke, Time White, John Harris and the PIGS

Pig teeth are a kind of paleonological clock increase in length and height through time. KBS pigs matched pigs from ~2 my at Omo and Olduvai, as did the OTHER fauna antelopes, zebras, etc

KBS team argued initially that fauna at Koobi For a looked younger because of a "faunal barrier" ... species in different parts of the basin evolved at different rates... but this proved to be wishful thinking. Pigs win.+ new dates @ 1.87 +/- 0.04mya, based on single crystal fusion Ar/Ar method.

Professor Jeanne Sept
(812) 855-5395 ; email: SEPT
Office Hours Student Bldg 038 TH 1:00-3:00, or by appt.	Lectures: Student Bldg 150 TuTh 11:15-12:30