Sequence stratigraphy, chemostratigraphy and facies analysis of Cambrian Series 2 – Series 3 boundary strata in northwestern Scotland
Sequence stratigraphy, chemostratigraphy and facies analysis of Cambrian Series 2 – Series 3 boundary strata in northwestern Scotland
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DOI：
10.1017/s0016756816000947
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发表时间：
2016-11
影响因子：
2.3
通讯作者：
Luke E. Faggetter;P. Wignall;S. Pruss;Yadong Sun;R. Raine;R. Newton;M. Widdowson;M. Joachimski
中科院分区：
文献类型：
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作者：
Luke E. Faggetter;P. Wignall;S. Pruss;Yadong Sun;R. Raine;R. Newton;M. Widdowson;M. Joachimski
摘要寒武系2 - 3统界线与全球范围内的碳同位素漂移、海平面变化和三叶虫灭绝相吻合。在这里，我们研究的沉积学，层序地层学和碳同位素记录的这段时间在苏格兰西北部的寒武纪地层（杜内斯组）。Durness群（Ghrudaidh组）下部的碳酸盐碳同位素数据表明，浅海劳伦阶边缘碳酸盐记录了两个相关的海平面和碳同位素事件。虽然碳同位素的偏移并不像其他地方所表达的那样明显，但与全球记录（Sauk I - Sauk II边界和Olenellus生物地层约束）的相关性将其确定为代表ROECE和DICE的局部表达。ROECE的上部记录在Ghrudaidh地层基底中，而DICE则位于该单元基底上方约30 m处。这两个碳同位素偏移共同发生的表面解释记录海退-海侵事件，产生合并的序列边界和沟壑/洪水表面覆盖的砾岩改造内碎屑。ROECE与redlichiid和olenellid三叶虫化石有关，但在苏格兰西北部，Olenellus是在碳同位素偏移负峰之后但在层序边界形成之前发现的。
Abstract Globally, the Series 2 – Series 3 boundary of the Cambrian System coincides with a major carbon isotope excursion, sea-level changes and trilobite extinctions. Here we examine the sedimentology, sequence stratigraphy and carbon isotope record of this interval in the Cambrian strata (Durness Group) of NW Scotland. Carbonate carbon isotope data from the lower part of the Durness Group (Ghrudaidh Formation) show that the shallow-marine, Laurentian margin carbonates record two linked sea-level and carbon isotopic events. Whilst the carbon isotope excursions are not as pronounced as those expressed elsewhere, correlation with global records (Sauk I – Sauk II boundary and Olenellus biostratigraphic constraint) identifies them as representing the local expression of the ROECE and DICE. The upper part of the ROECE is recorded in the basal Ghrudaidh Formation whilst the DICE is seen around 30m above the base of this unit. Both carbon isotope excursions co-occur with surfaces interpreted to record regressive–transgressive events that produced amalgamated sequence boundaries and ravinement/flooding surfaces overlain by conglomerates of reworked intraclasts. The ROECE has been linked with redlichiid and olenellid trilobite extinctions, but in NW Scotland, Olenellus is found after the negative peak of the carbon isotope excursion but before sequence boundary formation.