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首页> 外文期刊>Facies >Facies control on lower Cambrian wrinkle structure development and paleoenvironmental distribution, southern Great Basin, United States
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Facies control on lower Cambrian wrinkle structure development and paleoenvironmental distribution, southern Great Basin, United States

机译：美国大盆地南部下寒武统皱纹结构发育和古环境分布的相控

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Assessing the role that physical processes play in restricting microbial mat distribution has been difficult due to the primary control of bioturbation in the modern ocean. To isolate and determine the physical controls on microbial mat distribution and preservation, a time in Earth's history must be examined when bioturbation was not the primary control. This restricts the window of observation primarily to the Precambrian and Cambrian, which precede the development of typical Phanerozoic and modern levels of bioturbation. Lower Cambrian strata of the southern Great Basin, United States, record the widespread development of seafloor microbial mats in shallow shelf and nearshore settings. These microbial mats are recorded by wrinkle structures, which consist of millimeter-scale ridges and sinuous troughs that represent the former presence of a surface microbial mat. Wrinkle structures within these strata occur exclusively within heterolithic deposits of the offshore transition, i.e., between fair-weather wave base and storm wave base, and within heterolithic tidal-flat deposits. Wrinkle structures are not preserved in siltstone-dominated offshore deposits or amalgamated shoreface sandstones. The preservation of wrinkle structures within these environments is due to: (1) the development of microbial mats atop clean quartz-rich sands for growth and casting of the structures; and (2) the draping of the microbial mat by finer-grained sediment to inhibit erosion. The exclusion from offshore deposits may be due to a lack of sufficient sunlight, whereas the restriction from the shoreface is likely due to the amalgamation of proximal tempestites, resulting in the erosion of any incipient microbial mat development.
机译：由于现代海洋中生物扰动的主要控制，很难评估物理过程在限制微生物垫分布中的作用。为了隔离和确定对微生物垫的分布和保存的物理控制，当生物扰动不是主要控制因素时，必须检查地球历史上的一段时间。这将观察范围主要限制在前寒武纪和寒武纪，这是典型的生代时代和现代生物扰动水平发展之前的。美国南部大盆地的下寒武统地层记录了浅层陆架和近岸环境中海底微生物垫的广泛发展。这些微生物垫由皱纹结构记录，皱纹结构由毫米级的隆起和弯曲的槽组成，代表了表面微生物垫的先前存在。这些地层中的褶皱结构仅出现在海上过渡带的异质岩沉积物中，即在天气波基和风暴波基之间，以及异质性潮滩沉积物中。皱纹结构不能保存在粉砂岩为主的离岸沉积物中或合并的岸面砂岩中。在这些环境中保留皱纹结构的原因是：（1）在干净的富含石英的沙子上开发了微生物垫，以生长和铸造结构; （2）细颗粒沉积物覆盖微生物垫以抑制侵蚀。离岸沉积物被排除在外可能是由于缺乏足够的阳光，而从岸面的限制很可能是由于近端的陨石合并所致，从而腐蚀了任何初期的微生物垫。

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