Facies, phosphate, and fossil preservation potential across a Lower Cambrian carbonate shelf, Arrowie Basin, South Australia
Facies, phosphate, and fossil preservation potential across a Lower Cambrian carbonate shelf, Arrowie Basin, South Australia
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DOI：
10.1016/j.palaeo.2019.05.022
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发表时间：
2019-11
期刊：
影响因子：
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通讯作者：
Sarah M. Jacquet;Sarah M. Jacquet;Marissa J. Betts;Marissa J. Betts;J. Huntley;G. Brock;G. Brock
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文献类型：
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作者：
Sarah M. Jacquet;Sarah M. Jacquet;Marissa J. Betts;Marissa J. Betts;J. Huntley;G. Brock;G. Brock
寒武纪小壳化石保存潜力受沉积学、沉积学和埋藏学过程的影响，这对它们在生物地层学和高分辨率对比中的应用具有重要意义。为了研究这些过程对化石产状的影响，详细的微相分析，生物地层学数据和多变量分析被集成从一个典型的地层剖面相交的一套下寒武统碳酸盐岩古环境在北方弗林德斯山脉，南澳。这种继承加深了剖面，穿过低梯度的浅海大陆架。六个沉积相序列被确定为保护（FS 1）和开放（FS 2）的陆棚/泻湖系统，高能量的内斜坡浅滩复合体（FS 3），中陆架（FS 4），中到外陆架（FS 5）和外陆架（FS 6）环境。非度量多维尺度排序和双向聚类分析揭示了底层的水深梯度是SSF分布的主要控制因素。与产生初级有机生物矿物的类群不同，构建钙质骨架的类群更多地受到埋藏学控制，这进一步加剧了采样和处理偏差。一个强大的相关联与浓缩和改造的视野表明，石灰岩组的地层发生反映了有利于保存（磷酸盐和磷酸盐化），而不是真正的地层范围的条件。因此，在划分下寒武统层序的生物地层带时，应优先考虑有机藻类类群。
The effects of sedimentological, depositional and taphonomic processes on preservation potential of Cambrian small shelly fossils (SSF) have important implications for their utility in biostratigraphy and high-resolution correlation. To investigate the effects of these processes on fossil occurrence, detailed microfacies analysis, biostratigraphic data, and multivariate analyses are integrated from an exemplar stratigraphic section intersecting a suite of lower Cambrian carbonate palaeoenvironments in the northern Flinders Ranges, South Australia. The succession deepens upsection, across a low-gradient shallow-marine shelf. Six depositional Facies Sequences are identified ranging from protected (FS1) and open (FS2) shelf/lagoonal systems, high-energy inner ramp shoal complex (FS3), mid-shelf (FS4), mid- to outer-shelf (FS5) and outer-shelf (FS6) environments. Non-metric multi-dimensional scaling ordination and two-way cluster analysis reveal an underlying bathymetric gradient as the main control on the distribution of SSFs. Unlike groups that produced primary organophosphatic biominerals, taxa that built calcareous skeletons are more taphonomically-controlled, which is further exacerbated by sampling and processing biases. A strong facies association with condensed and reworked horizons suggests the stratigraphic occurrence of calcareous groups reflects conditions conducive to preservation (phosphogenesis and phosphatization) rather than true stratigraphic ranges. Consequently, organophosphatic taxa should take precedence in the erection of biostratigraphic zones for subdivision of lower Cambrian successions.