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: 2016
• 资助国家: 加拿大
• 起止时间: 2016-01-01 至 2017-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=612231
• 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，主要由海相化石组成。这些很久以前在海洋环境中形成的成分告诉我们许多关于我们星球上非常古老的海洋的信息，因此也告诉了我们世界的历史。此外，这些石灰岩是海洋生物随时间演变的重要档案，是美国地下最丰富的碳氢化合物储集层之一，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今天海洋碳酸盐沉积物是如何在海洋中形成的(相解剖)，以及它们是如何在漫长的地质年代中转化为岩石(早期成岩作用)的。然后，这些发现被用来产生预测性的科学模型，地球科学家可以使用这些模型来解释地球表面或深埋在地下的古老岩石。具体地说，重点是这些沉积物和岩石中最鲜为人知的，特别是冷水和高纬度海相碳酸盐和相关沉积物，早期化学变化的过程，包括改变它们的陆地和海洋，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南澳大利亚大陆架及其附近进行，那里是现代世界最大的冷水碳酸盐沉积区域。在NSERC以前在该区域支持的研究的基础上，将讨论下列问题：1)冷水海底沉积物的组成如何与上覆海水的性质有关，这如何控制这些沉积物的化学成分；2)同样的沉积物被吹入壮观的边缘海洋沙丘，这些沙丘的组成如何反映其来源和近海海洋环境；3)这些近海沉积物是否以某种方式有助于形成广泛的边缘海洋钙质土壤，所涉及的过程是什么；4)在毗邻南大洋的这种半干旱气候下，大型边缘海洋碳酸盐湖的成因是什么？这些问题将通过利用广泛的陆地测绘、采样和地球化学分析、海洋研究和计算机建模的综合实地计划来解决。还需要资金来调查非常古老的石灰岩，特别是1)了解古生代(550-2.25亿年前)海相碳酸盐砂体是如何形成的，以及2)通过碳酸盐沉积的性质确定新元古代(约8亿年前)全球海洋是如何在新元古代(约8亿年前)--就在复杂动物演化之前的一个全球冰期--期间演变的。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揭开岩石记录的科学家，到寻找埋藏的碳氢化合物储集层和矿藏的加拿大地球科学家，再到监测海洋环境变化的研究人员。