Facies anatomy and early diagenesis of carbonate rocks

碳酸盐岩相解剖与早期成岩作用

• 批准号: RGPIN-2014-06454
• 负责人: James, Noel
• 金额: $ 5.25万
• 依托单位: Queen's University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2014
• 资助国家: 加拿大
• 起止时间: 2014-01-01 至 2015-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=567815
• 关键词: Facies; anatomy; early; diagenesis; carbonate

Carbonate sedimentary rocks such as limestone are largely made of marine fossils. These components that formed in the marine environment long ago tell us much about the very ancient oceans of our planet and thus the history of our world. The limestones are, furthermore, significant archives of the evolution of marine life through time, amongst the nation's most prolific hydrocarbon reservoirs deep underground, and critical aquifers for fresh water and so human wellbeing. The aim of the science proposed here is to understand how marine carbonate sediments form in the ocean today (facies anatomy) and how they are then transformed into rock (early diagenesis) throughout the vastness of geologic time. These findings are then used to generate predictive scientific models that can be used by earth scientists to interpret ancient rocks at the earth’s surface or deeply buried underground. Specifically the focus is on the most poorly understood of these sediments and rocks specifically cool-water and high latitude marine carbonates and related deposits, the processes of early chemical alteration, both terrestrial and marine that change them, and the perplexing origin of 1 billion year old Precambrian carbonates. Much of the planned research will take place on and adjacent to the southern Australian continental shelf, the largest area of cool-water carbonate deposition in the modern world. Expanding on previous NSERC-supported research in the region, the following questions will be addressed: 1) how is the composition of cool-water seafloor sediment related to the nature of the overlying seawater and how does this govern the chemistry of these deposits, 2) the same sediments are blown into spectacular marginal marine sand dunes and how does the composition these dunes reflect their source, the offshore marine environment, 3) do these offshore sediments somehow contribute to the formation of widespread marginal marine calcareous soils and what are the processes involved, and 4) what is the genesis of large marginal marine carbonate lakes under this semiarid climate adjacent to the Southern Ocean? These questions will be addressed via an integrated field program utilizing extensive onland mapping, and sampling and geochemical analysis, marine research, and computer modeling. Funds are also requested to investigate very ancient limestones, specifically 1) to understand how Paleozoic (550-225 million year old) marine carbonate sand bodies were formed and 2) to determine, via the nature of carbonate sedimentation, how the global ocean evolved during the Neoproterozoic (~800 million years ago) a period of global glaciation just before the evolution of complex animals. The end users of this research range from scientists such as paleontologists, paleoceanographers, and sedimentary geologists unraveling the rock record, to Canadian geoscientists searching for buried hydrocarbon reservoirs and mineral deposits to researchers monitoring marine environmental change.

碳酸盐沉积岩，如石灰岩，大部分由海洋化石组成。这些很久以前在海洋环境中形成的成分告诉我们很多关于我们星球上非常古老的海洋的信息，从而也告诉我们世界的历史。此外，石灰岩是海洋生物进化的重要档案，是美国地下深处最多产的碳氢化合物储层之一，也是淡水和人类福祉的关键含水层。这里提出的科学的目的是了解海洋碳酸盐沉积物如何在今天的海洋中形成（相解剖学），以及它们如何在整个浩瀚的地质时代转化为岩石（早期成岩作用）。然后，这些发现被用来生成预测性的科学模型，这些模型可以被地球科学家用来解释地球表面或深埋地下的古老岩石。具体来说，重点是对这些沉积物和岩石中最不了解的，特别是冷水和高纬度海洋碳酸盐和相关沉积物，早期化学蚀变过程，陆地和海洋改变它们，以及令人困惑的10亿年前寒武纪碳酸盐的起源。计划中的大部分研究将在澳大利亚南部大陆架及其附近进行，这是现代世界上最大的冷水碳酸盐沉积区。扩大以前NSERC支持的研究在该地区，将解决以下问题：1）冷水海底沉积物的成分与上覆海水的性质如何相关，以及这如何支配这些沉积物的化学性质，2）相同的沉积物被吹成壮观的边缘海洋沙丘，这些沙丘的成分如何反映其来源，近海海洋环境，3）这些近海沉积物是否在某种程度上促成了广泛的边缘海洋钙质土的形成，以及所涉及的过程是什么？4）在南大洋附近的半干旱气候下，大型边缘海洋碳酸盐湖的成因是什么？这些问题将通过一个综合的实地项目来解决，该项目利用广泛的陆上测绘、取样和地球化学分析、海洋研究和计算机建模。还要求提供资金调查非常古老的石灰岩，特别是1）了解古生代（5.5亿至2.25亿年）海洋碳酸盐砂体是如何形成的，2）通过碳酸盐沉积的性质，确定新元古代（约8亿年前）全球海洋是如何演变的，新元古代是复杂动物进化之前的全球冰川期。这项研究的最终用户范围从古生物学家，古海洋学家和沉积地质学家等科学家解开岩石记录，到加拿大地球科学家寻找埋藏的碳氢化合物储层和矿床，再到监测海洋环境变化的研究人员。