SGER: Provenance of Cambrian Sandstones Argentine Precordillera

许多地质学家认为，阿根廷西部的前寒武纪地体是在早古生代从北美的祖先克拉通劳伦蒂亚转移到冈瓦那的，尽管在转移的方法和时间上存在相当大的分歧。在研究前寒武纪的地层层序时，PI偶然分析了两个石英砂岩层中的碎屑锆石，一个是早寒武世，另一个是晚奥陶世早期。结果令人惊讶，并导致他们得出结论，Precordillera地体从来不是劳伦西亚的一部分，而是从寒武纪热带冈瓦纳的一个地点迁移到奥陶纪之后的现在。这些结果还导致PI质疑所有支持前纪地体与劳伦斯亲缘关系的基本、广泛持有的假设。因为他们的初步数据的含义是1)革命性的，2)需要重新评估大量的证据，以及3)目前受到质疑和驳回，所以对他们的初步数据进行测试是至关重要的。他们建议从前纪寒武纪额外的寒武系砂岩层中采集样品，以获得碎屑锆石的U/Pb年代学。其目的是证明，来自单一初步样本的证据不是侥幸或异常，而是真正具有代表性。

SGER: Provenance of Cambrian Sandstones Argentine PrecordilleraStanley Finney (EAR-0332442)California State University--Long BeachABSTRACTMany geologists believe that the Precordillera terrane of western Argentina was transferred from Laurentia, the ancestral craton of North America, to Gondwana in the early Paleozoic, although considerable disagreement exists on the method and time of transfer. While studying stratigraphic successions in the Precordillera, the PIs by chance analyzed detrital zircons from two quartz sandstone beds, one of Early Cambrian age, the other of early Late Ordovician age. The results were surprising, and led them to conclude that the Precordillera terrane was never part of Laurentia, but instead migrated from a location in tropical Gondwana in Cambrian time to its present location after Ordovician time. These results also lead the PIs to question all the basic, widely held assumptions supporting the Laurentian affinity of the Precordillera terrane. Because the implications of their preliminary data are 1) revolutionary, 2) require re-evaluation of a substantial body of evidence, and 3) are presently subject to challenge and dismissal, it is critical that their preliminary data be tested. They propose to collect samples from additional Cambrian sandstone beds in the Precordillera for U/Pb geochronology of detrital zircons. The objective is to demonstrate that the evidence from the single preliminary sample is not a fluke or an aberration but instead is truly representative.