VPW: Extension of the Temporal Scale of Newly Resolved Middle Cambrian Sr Isotope Stratigraphy

相对于显生宙海水Sr同位素曲线中晚古生代至新生代部分的分辨率，早古生代海水87Sr/86Sr的变化记录较少。显生宙海水Sr同位素曲线的寒武系部分具有明显的分散程度和较大的不确定包络度。此外，新建立的前中寒武纪海水87Sr/86Sr长期变化数据库显示，中-晚寒武纪海水Sr同位素记录存在明显差距。因此，Sr同位素在提高中至上寒武统地层序列的年代地层分辨率方面的潜力非常有限，无法提供对中至晚寒武统海洋-大气-生物圈系统的深入了解，也无法潜在地限制这一时期的生物地球化学循环速率。本研究的两个主要目标集中在批判性地解决这些限制；这项研究的结果应该最大限度地减少或潜在地克服这些限制。第一个目标是完成大盆地南部Bonanza King碳酸盐岩第二段的详细Sr同位素分析，以测试新解析的Sr同位素地层学的稳健性。二是将综合研究扩展到大盆地南部富南扎王组Papoose湖段下寒武统碳酸盐岩和卡拉拉组上碳酸盐岩。本文的研究结果将与新解析的Sr同位素曲线和最近发表的早寒武世海水87Sr/86Sr值相结合，将提供一条与晚古生代和中生代许多部分Sr同位素曲线相当的分辨率的寒武纪海水Sr同位素曲线。反过来，这将提高寒武纪地层演替的年代地层分辨率，对寒武纪海洋-大气-生物圈系统的精确理解，并有效地限制这一时间间隔内生物地球化学循环的速率。最后，87Sr/86Sr数据库将最终从这个综合研究中产生，将不可避免地有助于洞察和潜在地解决许多有争议的“寒武纪”问题。互动活动包括四个方面：1)教授一场研究生-高年级本科生旋回地层学研讨会；2)积极参与其他碳酸盐沉积学、地层学和成岩作用研讨会；3)积极让本科生和研究生参与本研究项目；4)带领系对德克萨斯州和墨西哥东北部白垩纪进行实地考察。

Seawater 87Sr/86Sr variations during the Early Paleozoic are poorly documented relative to the resolution of the Late Paleozoic through Cenozoic portions of the Phanerozoic seawater Sr isotope curve. The Cambrian portion of the Phanerozoic seawater Sr isotope curve is especially characterized by a significant degree of scatter and a large uncertainty envelope. Moreover, the newly emerging data base of secular seawater 87Sr/86Sr variations for pre-Middle Cambrian time underscores a conspicuous gap in the Middle to Late Cambrian seawater Sr isotope record. Consequently, the potential of Sr isotopes for enhanced chronostratigraphic resolution of Middle to Upper Cambrian stratigraphic successions, is extremely limited for providing insight into the Middle to Late Cambrian ocean- atmosphere-biosphere system, and for potentially constraining rates of biogeochemical cycling during this time interval. The two main objectives of this study focus on critically addressing these limitations; the results of this research should minimize or potentially overcome these limitations. The first objective is to complete a detailed Sr isotopic analysis of a second section of Bonanza King carbonates from the southern Great Basin in order to test the robustness of the newly resolved Sr isotope stratigraphy. The second objective is extend the integrated study to lower Middle Cambrian carbonates of the Papoose Lake Member of the Bonanza King Formation and the upper Carrara Formation, southern Great Basin. The results of this research, when integrated with our new resolved Sr isotope curve and recently published Early Cambrian seawater 87Sr/86Sr values, will provide a Cambrian seawater Sr isotope curve of resolution comparable to many portions of the Late Paleozoic and Mesozoic Sr isotope curve. In turn, this will afford enhanced chronostratigraphic resolution of Cambrian stratigraphic successions, a refined understanding of the Cambrian ocean-atmosphere-biosphere system, and potent ial for constraining rates of biogeochemical cycling during this time interval. Lastly, the 87Sr/86Sr database which will ultimately result from this integrated study will inevitably contribute insight into and potentially resolve many controversial 'Cambrian' issues. Interactive activities consist of four facets: 1) teaching one graduate-upper division undergraduate level seminar in cycle stratigraphy, 2) actively participating in other carbonate sedimentology, stratigraphy and digenesis seminars, 3) actively involving undergraduate and graduate students in this research project, and 4) leading department field trips to the Cretaceous of Texas and northeastern Mexico.