December 2008 Geology and GSA Today media ...(University of California-Berkeley Berkel...)

The Middle Stone Age (MSA) of Africa is thought to be a period wherein human ancestors experienced significant advancement of cognitive abilities and physical dexterity, but the nature and timing of these advances is not yet well understood. MSA archaeology at Gademotta, in the Main Ethiopian Rift Valley, is dated to older than 277 thousand years ago, over 40 thousand years older than previously believed. The workmanship and sophistication of tool making at Gademotta and nearby Kulkuletti are markedly advanced for the antiquity of the sites' ages, suggesting that more primitive MSA archaeology should be even older, and that the MSA evolved at different rates in different places. If the emergence of the MSA is linked to the evolutionary appearance of Homo sapiens, as has often been suggested, then by implication early forms of our species may be 100 thousand years older than previously believed. The ready availability of high-quality geological materials such as obsidian may have played a role in rapidly advancing technology in certain areas such as Gademotta/Kulkuletti. The results are based primarily on new 40Ar/39Ar dating of volcanic ashes by Morgan and Renne at the Berkeley Geochronology Center.

Sulfur isotopes in sediment-hosted orogenic gold deposits: Evidence for an early timing and a seawater sulfur source

Zhaoshan Chang et al., CODES ARC Centre of Excellence in Ore Deposits, University of Tasmania, Private Bag 126, Hobart, Tasmania 7001, Australia. Pages 971-974.

Chang et al. report sulfur isotopic compositions of sulfides of various paragenetic stages in the giant Sukhoi Log sediment-hosted orogenic gold deposit. The overall mean value and the significant variability in early pyrite indicates that the sulfur was from the reduction of seawater sulfate. The later generations of sulfide have 34S values in successively smal
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