Devonian contourites in oceanic passageways between Gondwana and Laurussia

冈瓦纳大陆和劳俄罗斯之间海洋通道的泥盆纪等高线

• 批准号: 263581133
• 负责人: Professor Dr. Heiko Hüneke
• 金额: --
• 依托单位: Institut für Geografie und Geologie
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2015
• 资助国家: 德国
• 起止时间: 2014-12-31 至 2019-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/263581133?language=en
• 关键词: Devonian; contourites; oceanic; passageways; between

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.

虽然底流在大陆边形成过程中的基本作用现已得到充分记载，但从经济角度和科学界对深水环流的过程和产物仍知之甚少。沉积物沉积或显着影响这些底层电流被称为contourite。该项目将重点研究中晚泥盆世期间形成的化石钙质等深流岩，这些等深流岩形成于不断靠近的冈瓦纳大陆和劳鲁西亚大陆之间以及各种夹层微大陆之间的狭窄海洋通道中。泥盆纪的情况下，代表了一个以前认识到的例子，底流沉积物的古代记录。在国际地球科学方案“等高线：工艺和产品”（IGCP 619），我们的目标是（1）建立更好的等深岩化石识别标准，完善现有的等深岩沉积体系相模式，（2）绘制泥盆纪等深岩产状和分布图，为更详细的古海洋和古地理重建提供线索，（3）评价泥盆纪等深漂积岩作为储层研究的露头类似物。在所有海洋环境中对等深流岩的观测越来越多，这就要求在更好地整合小尺度特征（沉积相、层序）、中尺度特征（漂流几何形状、内部结构、相分布和趋势、侵蚀不整合面）和大尺度特征（古海洋学背景）的基础上，制定更明确的诊断标准。这可以通过参考陆地上的地点，牢固地建立基于露头的古等深岩识别来实现。由于海洋深水和浅水环流受板块构造控制，等深流沉积物是过去地球动力学变化的有用记录，因此将有助于更好地重建大陆和海洋板块。海洋通道在一系列古海洋学过程中占有重要地位;它们的打开和关闭在过去的地质、海洋物理循环和全球气候中发挥了重要作用。在这种背景下，泥盆纪等深流岩的出现是一个非常重要的事实。这些等深岩保存了一个独特的记录，为钙质深海软泥的底流改造提供了有力的证据。基于沉积学和地层学的调查，我们的目标是解码泥盆纪等深沉积体系的具体古海洋学记录与冈瓦纳和劳鲁西亚之间的海洋门户和他们的逐步关闭。在确定年龄和相关的侵蚀不连续性和磷酸盐矿床，这是由特别强大的底流造成的程度，我们的目标是建立一个全球性的等深岩相古海洋学签名的相关性。