خط مشی دسترسیدرباره ماپشتیبانی آنلاین
ثبت نامثبت نام
راهنماراهنما
فارسی
ورودورود
صفحه اصلیصفحه اصلی
جستجوی مدارک
تمام متن
منابع دیجیتالی
رکورد قبلیرکورد بعدی
Document Type:Latin Dissertation
Language of Document:English
Record Number:53132
Doc. No:TL23086
Call number:‭3369111‬
Main Entry:Leah Elizabeth Morgan
Title & Author:Geochronological constraints on Plio-Pleistocene hominid evolution in the Ethiopian riftLeah Elizabeth Morgan
College:University of California, Berkeley
Date:2009
Degree:Ph.D.
student score:2009
Page No:238
Abstract:Constraining the ages of fossiliferous and artifact-rich sediments is a critical part of understanding human evolution. Precise and accurate geochronology can constrain the order and timing of specific evolutionary events, contribute to the intercalibration of tectonic, climatic, paleontological, and archaeological timescales, and allow assessment of possible relationships between these. Two chapters here involve the application of the 40 Ar/ 39 Ar method to archaeological and paleontological localities in Ethiopia. This method is most commonly applied to minerals (often feldspars) found in volcanic ash or tephra horizons interbedded with fossiliferous sediments. The first is Gademotta, a Middle Stone Age (MSA) archaeological site that is shown here to be one of the earliest of its kind, and certainly the most technologically advanced site known for early MSA sites. Since it has been suggested that the biological evolution of Homo sapiens may be causally related to the advent of the MSA, these new dates may show that H. sapiens existed nearly 300 thousand years ago. The second is Melka Kunture, an Ethiopian archaeological site covering all major archaeological periods from the Oldowan to the Late Stone Age. Few localities allow insight into archaeological changes over a wide timespan in one relatively small area. New ages from here may provide the earliest evidence for exploitation of obsidian as a raw material for tool-making--possibly ∼700 ka earlier than elsewhere. The third chapter outlines issues and solutions involved in reliably applying the 40 Ar/39 Ar method to volcanic glasses, including volcanic ashes and obsidian. Problems with 39 Ar recoil, K and/or Ar mobility and sub-atmospheric initial 40 Ar/ 36 Ar ratios are addressed. These three projects together provide significant information regarding the timing of the biological and behavioral evolution of our own species and help expand the reach of the 40 Ar/39 Ar method.
Subject:Social sciences; Earth sciences; Argon-argon dating; Geochronology; Human origins; Middle stone age; Vertebrate paleontology; Hominid evolution; Ethiopian rift; Archaeology; Geology; Geochemistry; 0996:Geochemistry; 0324:Archaeology; 0372:Geology
Added Entry:P. R. Renne
Added Entry:University of California, Berkeley