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.

石灰岩等碳酸盐沉积岩主要由海洋化石组成。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，从而告诉我们世界的历史。此外，石灰岩是海洋生物随时间演变的重要档案，是美国地下深处最多产的碳氢化合物储层，也是淡水和人类福祉的关键含水层。这里提出的科学目的是了解当今海洋中海洋碳酸盐沉积物是如何形成的（相解剖学）以及它们如何在漫长的地质时期转化为岩石（早期成岩作用）。然后，这些发现被用来生成预测科学模型，地球科学家可以使用这些模型来解释地球表面或深埋地下的古代岩石。具体而言，重点是人们对这些沉积物和岩石中了解最少的部分，特别是冷水和高纬度海洋碳酸盐及相关沉积物、改变它们的陆地和海洋早期化学蚀变过程，以及 10 亿年前寒武纪碳酸盐的令人困惑的起源。 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，这里是现代世界最大的冷水碳酸盐沉积区。扩展以前在该地区由 NSERC 支持的研究，将解决以下问题：1）冷水海底沉积物的成分如何与上覆海水的性质相关，以及这如何控制这些沉积物的化学成分，2）相同的沉积物被吹入壮观的边缘海洋沙丘，这些沙丘的成分如何反映其来源，即近海海洋环境，3）如何做到这些 近海沉积物在某种程度上促成了广泛的边缘海洋钙质土壤的形成，其中涉及哪些过程，4）在毗邻南大洋的半干旱气候下，大型边缘海洋碳酸盐湖的成因是什么？这些问题将通过综合实地计划得到解决，该计划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。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全球海洋在新元古代（约8亿年前）期间是如何演化的，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包括解开岩石记录的古生物学家、古海洋学家和沉积地质学家等科学家，到寻找埋藏碳氢化合物储层和矿床的加拿大地球科学家，再到监测海洋环境变化的研究人员。