Devonian contourites in oceanic passageways between Gondwana and Laurussia

• Applicant: Professor Dr. Heiko Hüneke
• Subject Area: Palaeontology
• Term: from 2015 to 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 263581133

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.

• DFG Programme: Research Grants
• Participating Person: Dr. Zhor Sarah Aboussalam