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首页> 外文学位 >Variations in microbialite morphology with depositional environment in a Precambrian ramp deposit, Hamersley Group, western Australia.
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Variations in microbialite morphology with depositional environment in a Precambrian ramp deposit, Hamersley Group, western Australia.

机译：西澳大利亚州哈默斯利集团前寒武纪斜坡沉积物中微生物岩形态随沉积环境的变化。

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摘要

The Neoarchean Carawine Formation was deposited before the oxidation of the atmosphere and preserves a carbonate ramp with a range of microbially produced structures. These structures reflect the interplay of physical and chemical conditions, microbial growth, and cement precipitation. Their distribution implies that specific structures might be used as paleoenvironmental indicators. Such microbial facies are a large part of the rock record, and their identification and interpretation are important for understanding the development of many carbonate deposits.; In the Carawine, shallow, subtidal facies contain biohermal and bedded stromatolites, centimeter-scale ridge-shaped microbialites, wavy-laminated microbialites, and microbial tube structures. Tube structures are products of dewatering, microbial growth, and cementation; these fluid escape structures previously have not been recognized in the rock record but may occur in other microbial facies (e.g. Famennian, Canning Basin). Some shallow, subtidal microbial facies, such as biohermal and bedded stromatolites, are characteristic of younger carbonates that were deposited after the transition from an anoxic to oxic atmosphere. Therefore, the morphology of shallow water microbial structures may be controlled more by physical conditions than by chemical conditions.; Deep subtidal facies are composed of fenestrate microbialites, planar laminated dolomite, and rolled up microbially laminated dolomite. Fenestrate microbialites are delicate organic structures that grew in quiet, sediment-free, deep subtidal environments. They composed of vertically oriented supports and sub-horizontal drapes. Some vertical supports were created when rising gas bubbles disrupted planar laminated mat, creating vertical flaps that were substrates for further microbial growth. Drapes of mat developed between two adjacent supports in a sequence of microbial growth, cell dispersal, and cementation. The demise of fenestrate microbialites seems to coincide with the development of a sulphidic deep ocean ∼2.3 Ga, during the stepwise oxidation of the Earth's surface. This suggests that in deep subtidal environments, the morphology of microbial structures may be controlled more by chemical processes than by physical ones.
机译：在大气氧化之前，就沉积了新陈代谢的Carawine组，并保留了具有一系列微生物产生的结构的碳酸盐斜坡。这些结构反映了物理和化学条件，微生物生长和水泥沉淀之间的相互作用。它们的分布意味着特定的结构可以用作古环境指标。这种微生物相是岩石记录的很大一部分，它们的识别和解释对于理解许多碳酸盐矿床的发育很重要。在Carawine中，浅层的潮下相包含生物层状和层状叠层石，厘米级山脊形微斜岩，波浪状叠层微斜岩和微生物管结构。管结构是脱水，微生物生长和胶结的产物。这些流体逸出结构以前在岩石记录中尚未发现，但可能在其他微生物相中发生（例如，Famennen，Canning盆地）。一些浅层，潮下微生物相，例如生物层状和层状叠层石，是较年轻的碳酸盐的特征，这些碳酸盐是从缺氧气氛过渡到有氧气氛后沉积的。因此，浅水微生物结构的形态可能更多地由物理条件而不是化学条件控制。潮下带深相由有孔的微辉石，平面层状白云岩和卷起的微生物层状白云岩组成。穿孔微微生物是在安静，无沉淀物的深潮下环境中生长的精细有机结构。它们由垂直方向的支撑物和亚水平的帷幕组成。当上升的气泡破坏平面层压垫时，会产生一些垂直支撑，从而形成垂直的折板，将其作为进一步微生物生长的基质。垫子的帘子在微生物生长，细胞扩散和胶结作用的一系列相邻两个支撑物之间形成。在地球表面逐步氧化的过程中，有毒的微恶岩的消亡似乎与约2.3 Ga的硫化深海的发展相吻合。这表明在深潮下环境中，微生物结构的形态可能更多地由化学过程控制，而不是由物理过程控制。

著录项

  • 作者

    Murphy, Megan Ann.;

  • 作者单位

    University of California, Davis.;

  • 授予单位 University of California, Davis.;
  • 学科 Geology.
  • 学位 Ph.D.
  • 年度 2006
  • 页码 91 p.
  • 总页数 91
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 地质学;
  • 关键词

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