Devonian contourites in oceanic passageways between Gondwana and Laurussia

尽管海底流在大陆边缘构造中的基本作用迄今已有很好的记载，但无论是在经济上还是在科学界，对深水循环的过程和产品仍然知之甚少。受这些底流沉积或显著影响的沉积物称为等深流。该项目将重点研究中-晚泥盆世在冈瓦那和洛鲁西亚大陆之间以及各种夹层微大陆之间狭窄的海洋通道中形成的钙质等深岩化石。泥盆纪的案例是之前从古代记录中发现的为数不多的海底流沉积实例之一。在国际地球科学计划“等高线：过程和产品”(IGCP 619)的框架内，我们的目标是：(1)建立更好的等深岩化石识别标准，完善现有等深岩沉积体系的相模式；(2)绘制泥盆纪等深岩的产状和分布图，为更详细的古海洋和古地理重建提供线索；以及(3)评价泥盆纪等深部漂移作为储集层研究的露头类似物。在所有海洋环境中对等高线的观察越来越多，这就需要更明确的诊断标准，其基础是更好地结合小尺度特征(沉积相、层序)、中尺度特征(漂移几何、内部结构、相分布和趋势、侵蚀不整合)和大尺度特征(古海洋环境)。这可以通过牢固地建立以露头为基础的古等值线识别来实现，参照陆地上的位置。由于大洋深水和浅水环流受控于板块构造，海侵沉积是过去地球动力学变化的有用记录，因此有助于更好地重建大陆和海洋板块。海洋通道参与了一系列古海洋过程，它们的开启和关闭对大洋的地质历史、S的物理循环和全球气候都起到了重要作用。在此背景下，泥盆纪等深线的出现是一个极其重要的事实。这些等深线保存了独特的记录，为钙质深海渗漏的底流改造提供了强有力的证据。在沉积学和地层学研究的基础上，我们旨在破译与冈瓦那和劳鲁西亚之间的洋门有关的泥盆纪等深岩沉积体系及其逐步闭合的特定古海洋学记录。在确定由特别强烈的底流引起的相关侵蚀不连续和磷酸盐沉积的年龄和范围时，我们的目标是建立等深岩古海洋学特征的全球对比。

Although the fundamental role of bottom currents in the construction of continental margins has by now been well documented, the processes and products of deep-water circulation remain poorly understood, both economically and in the scientific community. The sediments deposited or significantly affected by these bottom currents are known as contourites. The project will focus on fossil calcareous contourites formed during the Middle-Late Devonian in the narrowing oceanic passageways between the approaching continents Gondwana and Laurussia, as well as between the various sandwiched micro-continents. The Devonian case represents one of the few previously recognized examples of bottom-current deposits from the ancient record. Within the framework of the International Geoscience Programme "Contourites: Processes and Products" (IGCP 619), we aim to (1) establish better diagnostic criteria for the identification of fossil contourites and refine the existing facies models for contourite depositional systems, (2) chart the occurrence and distribution of Devonian contourites, to provide clues for more detailed palaeoceanographic and palaeogeographic reconstructions, and (3) evaluate the Devonian contourite drifts as outcrop analogues for reservoir studies. The increasing observation of contourites in all marine environments calls for more unambiguous diagnostic criteria, based upon a better integration of small-scale characteristics (sediment facies, sequences), medium-scale (drift geometry, internal architecture, facies distribution and trends, erosional disconformities), and large-scale (palaeoceanographic setting). This can be achieved by firmly establishing the outcrop-based recognition of ancient contourites with reference to localities on land. Since oceanic deep- and shallow-water circulation is controlled by plate tectonics, the contouritic deposits are useful recorders of past geodynamic changes and will therefore assist in a better reconstruction of the continental and oceanic plates. Ocean passageways are prominently involved in a range of palaeoceanographic processes; their opening and closing played an important role in the geological past in the ocean s physical circulation and the global climate at large. In the light of this context, the occurrence of Devonian contourites is a hugely important fact. These contourites preserve a unique record giving strong evidence for bottom-current reworking of calcareous deep-sea oozes. Based on sedimentologic and stratigraphic investigations, we aim to decode the specific palaeoceanographic record of Devonian contourite depositional systems associated with the oceanic gateways between Gondwana and Laurussia and their stepwise closing. In determining the age and extent of the associated erosional discontinuities and phosphatic deposits, which are caused by particularly strong bottom currents, we aim to establish a global correlation of the contourite palaeoceanographic signatures.