Facies anatomy and early diagenesis of carbonate rocks

碳酸盐沉积岩，如石灰岩，主要是由海洋化石构成的。很久以前在海洋环境中形成的这些成分告诉我们很多关于我们这个星球上非常古老的海洋的信息，从而告诉我们这个世界的历史。此外，石灰石是海洋生物进化的重要档案，是全国最丰富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。这里提出的科学目的是了解海洋碳酸盐沉积物是如何在今天的海洋中形成的（相解剖学），以及它们是如何在漫长的地质时间中转化为岩石的（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在地下的古代岩石。具体来说，重点是对这些沉积物和岩石，特别是冷水和高纬度海相碳酸盐和相关沉积物，早期化学变化过程，陆地和海洋改变它们，以及10亿年前前寒武纪碳酸盐的令人困惑的起源。大部分计划中的研究将在南澳大利亚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。扩展nserc在该地区以前支持的研究，将解决以下问题：1)冷水海底沉积物的组成与上覆海水的性质有何关系，这如何影响这些沉积物的化学性质；2)同样的沉积物被吹成壮观的边缘海洋沙丘，这些沙丘的组成如何反映它们的来源，近海海洋环境；3)这些近海沉积物是否以某种方式促进了广泛分布的边缘海洋钙质土壤的形成，其中涉及的过程是什么？4)在这种与南大洋相邻的半干旱气候下，大型边缘海相碳酸盐岩湖泊的成因是什么？这些问题将通过一个综合的实地计划来解决，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。还需要资金来研究非常古老的石灰石，特别是1)了解古生代（5.5 - 2.25亿年）海相碳酸盐砂体是如何形成的；2)通过碳酸盐沉积的性质来确定新元古代（~8亿年前）全球冰川时期全球海洋是如何演变的，而这段时期恰好是复杂动物进化之前。这项研究的最终用户包括古生物学家、古海洋学家和解开岩石记录的沉积地质学家等科学家，寻找埋藏碳氢化合物储集层和矿床的加拿大地球科学家，以及监测海洋环境变化的研究人员。

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.