Jurassic Paleoceanography: Oxygen Isotope Study of Lower to Middle Jurassic Carbonate Strata in the Central High Atlas Mountains of Morocco

这项研究将确定一个 中部侏罗纪碳酸盐岩古海洋学项目 位于摩洛哥的阿特拉斯山脉。 主要问题是 解决的问题是：1）下坡运输的复杂性是否可以 克服了这一困难，所以生活在浅水和深海中的化石 环境可以恢复地球化学分析？2)做 这些化石同位素组成是沉积作用的结果 条件（即，他们是不变的），或者有同位素 在随后的成岩事件中，成分发生了变化？ 沉积环境与 中生代腕足动物的形态应该有助于区分 来自浅海和深海环境的化石。 第二个问题 是通过各种地球化学和岩相学方法来解决的 对样本本身的分析，以及广泛关注的 研究碳酸盐岩成岩作用，确定区域 成岩趋势 未改变的腕足材料应该显示纤维， 原始腕足动物典型的“龙骨和马鞍”显微结构， 不应阴极发光，且应含有微量元素 在先前测量的组成范围内的组成， 侏罗纪腕足动物。 同位素组成本身是有用的 在协变趋势中 和 通常可以用来 区分原始签名和修改的作品。 化石与其他岩石同位素组成的比较 组件也应该有助于确定腕足动物的可靠性， 用于古海洋学研究的合成物。 例如浅 而来自同一地区的深海腕足动物 如果保存完好的话会有不同的同位素组成 而相同的成分则暗示成岩作用的改变。 同样，如果腕足动物的组成与其他动物不同， 化石和水泥或泥晶灰岩，似乎埋葬 再平衡并不广泛。 这些同位素组成也将更好地理解， 从区域到亚区域的侏罗系成岩作用研究 中阿特拉斯山脉南部的碳酸盐岩。 这样的 研究应能估计成岩流体的类型 穿过这些岩石的水流， 这些液体。 这些方法的结合（直接观察， 与其他岩石成分的比较，以及与区域的比较 成岩趋势）应允许确定是否同位素 阿特拉斯山脉中央高地腕足动物的组成 摩洛哥的古海洋学研究是适宜的。 如果是则 将为一项研究奠定基础， 侏罗纪深海环流的结论。

This study will determine the feasibility of a paleoceanographic project on Jurassic carbonates in the Central High Atlas Mountains of Morocco. The principal questions to be addressed are: 1) Can the complexities of downslope transport be overcome, so that fossils that lived in both shallow and abyssal environments can be recovered for geochemical analysis? 2) Do the isotopic compositions of those fossils result from depositional conditions (i.e., are they unaltered), or have the isotopic compositions been changed during subsequent diagenetic events? The relationship between depositional environment and morphology in Mesozoic brachiopods should help distinguish between fossils from shallow and abyssal environments. The second question is to be addressed by a variety of geochemical and petrographic analyses of the samples themselves, as well as by a broadly-focused study of carbonate diagenesis in the area to determine regional diagenetic trends. Unaltered brachiopod material should display the fibrous, "keel and saddle" microstructure typical of pristine brachiopods, should not cathodoluminesce, and should have trace element compositions in the range of compositions previously measured in Jurassic brachiopods. Isotopic compositions themselves are of use in that covariant trends in and can often be used to distinguish between original signatures and altered compositions. Comparison of isotopic compositions of fossils and other rock components should also help determine the reliability of brachiopod compositions for paleoceanographic research. For example, shallow and abyssal brachiopods from the same locality will most likely have differing isotopic compositions if they are well-preserved, whereas identical compositions would suggest diagenetic alteration. Similarly, if brachiopod compositions differ from those of other fossils and cements or micrite, it would appear that burial reequilibration has not been extensive. These isotopic compositions will also be better understood in light of a regional to sub-regional study of diagenesis in Jurassic carbonates of the southern Central High Atlas Mountains. Such a study should allow estimation of the types of diagenetic fluids that have passed through these rocks, as well as the flow paths of those fluids. The combination of these approaches (direct observations, comparison with other rock components, and comparison with regional diagenetic trends) should allow determination of whether isotopic compositions of brachiopods from the Central High Atlas Mountains of Morocco are suitable for paleoceanographic research. If so, the stage will be set for a study that should allow significant conclusions about Jurassic deep ocean circulation.