Collaborative Research: Interbasinal Applications of Newly- Resolved Middle to Late Cambrian Sr Isotope Stratigraphy: North American Cordilleran Margin

小行星9628535 拟议的研究有一个主要目标：进行协调的层序地层学和Sr同位素研究暴露在加拿大落基山脉南部的中上寒武统碳酸盐岩。 该项目是大盆地南部同时代地层相关工作的自然延伸，将沉积成因模型与锶同位素地层学相结合。 大盆地研究的结果是：1）对古生代锶同位素海水曲线中定义最差的一部分进行了相当大的改进; 2）有证据表明，过去20亿年来海水87Sr/86Sr的最高值是在1980年至2000年之间。可能发生在中寒武世晚期至晚寒武世早期的海洋中，3）在这一时间间隔内增强年代地层分辨率的潜力，4）在温室时代期间，地球化学和海水87 Sr/86 Sr之间的机械联系的建议，以及5）对寒武纪造山事件的时间和幅度施加限制的潜力。 本提案中规定的研究的最终目标是进行一次流域间试验，以评估温室期间铕和海水87 Sr/86 Sr之间可能存在的联系。 这项合作提案与NSF VPW计划的平行提案一起提交，该提案列出了完成和扩大大盆地研究时间范围的计划。 将用于开展拟议工作的方法包括两个阶段。 首先，将在加拿大落基山脉南部测量三个具有最完整暴露和最高生物地层控制程度的剖面，重点是Mt。怀特穿过莱尔下层 将使用层序地层学的基本前提来解释这三个部分的数据，并使用由此产生的成因模型来构建可容纳空间历史。 在所有可用的生物地层学信息被整合到成因地层学中之后，将尝试与同时代的Bonanza King Baglion进行相关，以评估适应事件之间的同步性程度。 在三个测量剖面中，一个剖面的岩石学和地球化学分析结果最高。 所有样品将通过平面光、阴极发光和落射荧光检查重结晶、微组构和显微结构保存、发光特性以及样品溶解过程中可能导致放射性87 Sr的非碳酸盐包裹体的存在。 将对符合岩相学标准的样品进行地球化学指标分析，以评估其成岩改造状态，作为选择蚀变最小组分进行Sr同位素分析的额外先决条件。 最后，样品将通过预处理技术运行，这些技术是由于以前对南部大盆地样品的测试而改进的。 拟议的流域间项目的最终目标是评估一个新的模型，该模型表明在温室期间，铕和海水87 Sr/86 Sr之间存在机械联系。 大盆地南部的早期研究表明，Sr同位素地层学与长期海侵和海退之间存在相关性，这些海侵和海退影响了可供风化的大陆表面积。 这个模型，以及长期海水同位素曲线，需要在一个完全不同的盆地进行测试，以评估其科学有效性。 如果从加拿大落基山脉南部的结果证实了时间海水87 Sr/86 Sr的趋势和Euronium和海水87 Sr/86 Sr之间的连接，那么一个全新的水平的分辨率在Sr同位素曲线的古生代时间将已经达到。 这可能会促使进一步的研究，以寻找在古生代海水87 Sr/86 Sr曲线在106年尺度上的趋势，可能与海平面变化。 在更广泛的范围内，87 Sr/86 Sr数据，从这个综合研究将有助于关键信息广泛的寒武纪造山作用与组装的冈瓦纳，寒武纪生物辐射和反射，并可能广泛发展的寒武纪被动边缘沉积序列。

9628535 Banner The proposed research has one primary objective: to carry out a coordinated sequence stratigraphic and Sr isotope study of Middle to lower Upper Cambrian Carbonates exposed in the southern Canadian Rocky Mountains. This project is a natural extension of related work on coeval strata in the southern Great Basin that integrated a genetic model of deposition with Sr isotope stratigraphy. The Great Basin research has resulted in 1) considerable refinement of a portion of the most poorly-defined interval of the Phanerozoic Sr isotope seawater curve, 2) evidence that the highest seawater 87Sr/86Sr values over the past 2 b.y. likely occurred in latest Middle to earliest Late Cambrian oceans, 3) potential for enhanced chronostratigraphic resolution in this time interval, 4) suggestion of a mechanistic link between eustasy and seawater 87Sr/86Sr during greenhouse times, and 5) potential for placing constraints on the timing and magnitude of Cambrian orogenic events. The ultimate goal of the research laid out in this proposal is to perform an interbasinal test to evaluate the possible connection between eustasy and seawater 87Sr/86Sr during greenhouse times. This collaborative proposal is being submitted in conjunction with a parallel proposal to the VPW Program at NSF that lays out plans for completing and extending the temporal range of the research in the Great Basin. The methods that will be used to carry out the proposed work involved two phases. First, three sections with the most complete exposure and highest degree of biostratigraphic control will be measured in the southern Canadian Rockies, focusing on the Mt. Whyte through lower Lyell Formations. Data from the three sections will be interpreted using the fundamental premises of sequence stratigraphy, with the resulting genetic model used to construct an accommodation history. After all available biostratigraphic information is integrated into the genetic stratigraphy, correlations with the coeval Bonanza King Formati on will be attempted to assess the degree of synchroneity between accommodation events. Of the three measured sections, the one section with the highest petrographic and geochemical analysis of collected samples. All samples will be examined by plane-light, cathodoluminescence, and epifluorscence for evidence of recrystallization, preservation of microfabrics and microstructures, luminescence characteristics, and presence of noncarbonate inclusions which could contribute radiogenic 87Sr during sample dissolution. Samples that meet petrographic criteria will be analyzed for geochemical indicators to assess their state of diagenetic modification as an additional prerequisite to selection of least-altered components for Sr isotope analysis. Finally, samples will be run through pretreatment techniques that have been refined as a result of previous testing on samples from the southern Great Basin. The ultimate goal of the proposed interbasinal project is to evaluate a new model that suggests a mechanistic link between eustasy and seawater 87Sr/86Sr during greenhouse times. Earlier work in the southern Great Basin suggests a correlation between the Sr isotope stratigraphy and long-term transgressions and regressions that affect the amount of continental surface area available for weathering. This model, as well as the secular seawater isotope curve, need to be tested in a completely different basin to assess their scientific validity. If the results from the southern Canadian Rocky Mountains confirm the temporal seawatep 87Sr/86Sr trend and the connection between eustasy and seawater 87Sr/86Sr, then an entirely new level of resolution in the Sr isotope curve for Paleozoic time will have been attained. This may spur further research into searching for trends in the Paleozoicseawater 87Sr/86Sr curve at the 106 year scale that may be related to eustatic variation. On a broader scale, the 87Sr/86Sr data from this integrated study will contribute critical information regarding the widespread Cam brian orogenesis associated with the assembly of Gondwana, Cambrian biotic radiations and extinctions, and perhaps about the extensive development of Cambrian passive margin depositional sequences.