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首页> 外文学位 >Geoarchaeology, stable-isotope geochemistry, and geochronology of fossil-spring tufas, Western Desert, Egypt.
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Geoarchaeology, stable-isotope geochemistry, and geochronology of fossil-spring tufas, Western Desert, Egypt.

机译：埃及西部沙漠的地球考古学，稳定同位素地球化学和泉水化石的年代学。

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摘要

The study of past climates has implications for Homo sapiens not only as a context for the climatic changes we are experiencing now, but also as a framework for hominid evolution. In both contexts, the Sahara is an intriguing and critical region. Fossil-spring tufas with associated artifacts in Kharga Oasis, Egypt, are particularly suitable for developing a climatic and cultural history for the currently hyperarid core of the Sahara. I carried out a geologic and archaeological survey of four tufa localities to establish a relative chronologic framework for these deposits as context for uranium-series dating, and to reconstruct the landscapes of prehistoric occupation in tufa-depositing regions. Most of the tufas were deposited as part of a fluvial barrage system, characterized by terraced, vegetated pools, which were impounded by arcuate tufa dams and separated by small waterfalls. Lithic artifacts associated with the tufas indicate repeated occupation during times when increased precipitation caused spring flow at these localities.; Stable-isotope analyses of tufas and freshwater gastropods from Kharga Oasis indicate that this region received enough precipitation to support perennial lakes during the height of the oxygen isotope stage 6/5e pluvial event. However, conditions were variable over the course of each pluvial event, signified by lithologic changes and by significant oxygen-isotope variability within individual tufa stratigraphic units.; A compilation of Pleistocene dates on pluvial conditions in the Sahara reveals a number of time periods which are represented by humid conditions at multiple localities in North Africa. The timing of these events corresponds well to the peaks of a monsoon index calculated from orbital parameters. The relative magnitude of the Saharan pluvial events also matches what would be predicted from the peak values of monsoon index. As the northward expansion of monsoonal rainfall would have left dry tropics in its wake, the Saharan pluvial events not only allowed for hominid migration into North Africa, but also encouraged such migration. Based on monsoon-index values, the 210 ka pluvial event would have represented the largest “push” north for hominid populations.
机译：对过去气候的研究不仅对智人产生了影响，它不仅是我们现在正在经历的气候变化的背景，而且还是人类发展的框架。在这两种情况下，撒哈拉沙漠都是一个有趣而关键的地区。埃及喀尔加绿洲的化石春季凝灰岩及其相关文物，特别适合于开发目前撒哈拉沙漠中高度干旱地区的气候和文化历史。我对四个图法地区进行了地质和考古调查，以建立这些沉积物的相对年代学框架，作为铀系列年代学的背景，并重建了图法沉积地区的史前职业景观。大部分的凝灰岩是作为河流拦河坝系统的一部分沉积的，其特征是梯田的，无植被的水池，这些水池由弓形的凝灰岩水坝蓄水，并被小瀑布隔开。与凝灰岩相关的岩性文物表明，在降水增加导致这些地区春季水流的时期，重复的占领。来自喀尔加绿洲的石灰石和淡水腹足类动物的稳定同位素分析表明，该地区在氧同位素阶段6 / 5e暴雨事件的高度期间收到了足够的降水量来支持多年生湖泊。但是，条件在每个暴雨事件的过程中都是可变的，这由岩性变化和单个凝灰岩地层单位内的显着的氧同位素变化所表示。一份关于撒哈拉沙漠条件下的更新世日期的汇编揭示了一些时期，这些时期以北非多个地区的潮湿条件为代表。这些事件的时间与根据轨道参数计算得出的季风指数的峰值非常吻合。撒哈拉暴雨事件的相对强度也与季风指数峰值相符。由于季风性降雨向北扩展将使干燥的热带地区一扫而光，因此撒哈拉暴雨事件不仅使人为向北非的迁移成为可能，而且也鼓励了这种迁移。根据季风指数值，210 ka的暴雨事件将代表原始人类最大的“推”北。

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  • 作者

    Smith, Jennifer Rebecca.;

  • 作者单位

    University of Pennsylvania.;

  • 授予单位 University of Pennsylvania.;
  • 学科 Geology.; Paleoecology.; Geochemistry.
  • 学位 Ph.D.
  • 年度 2001
  • 页码 176 p.
  • 总页数 176
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 地质学;古生物学;地质学;
  • 关键词

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