--> ABSTRACT: 3-D Seismic Geomorphology of Channel Systems in the Chalk Group, Southern Danish North Sea, by Masoumi, Samaneh; Back, Stefan; Reuning, Lars; Kukla, Peter; #90135 (2011)

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3-D Seismic Geomorphology of Channel Systems in the Chalk Group, Southern Danish North Sea

Masoumi, Samaneh 1; Back, Stefan 1; Reuning, Lars 1; Kukla, Peter 1
(1)Geology institut, Aachen, Germany.

The Upper Cretaceous to lower Paleogene Chalk Group of NW Europe is classically assumed to represent the settlement of homogeneous calcareous ooze from suspension draping submarine morphology under quiet pelagic conditions. Recently, the documentation of prominent intra-Chalk reflection discontinuities on 3D seismic data led to a revision of some general ideas of chalk deposition: (1) it was documented that intra-Chalk discontinuity features such as channels and drifts developed in response to strong bottom currents affecting the Late Cretaceous “chalk sea”; (2) the detection of large-scale mass-transport systems within chalk strata documented that at the same time gravity-driven erosional and depositional processes exerted a complementary control on the development of prominent intra-Chalk discontinuities.

This study presents a detailed synoptic analysis of two major elongate intra-Chalk channel systems preserved in the subsurface of the Danish North-Sea Central Graben. The first system trends over approximately 20 km in N-S direction, exhibiting a sinuous downslope course flanked by large master levees, and an infill characterized by well-developed secondary banks and overbanks on the outer bends of the channel thalweg. The second system can be traced over approximately 10 km in an E-W direction; this channel lacks sinuosity, the development of inner or outer levees, and is strongly asymmetrical. A comparative seismic-geomorphological analysis of both systems shows that the sinuous, N-S trending channel displays many of the architectural elements of “classic” siliciclastic deepwater channels, supporting its interpretation as a gravity-driven turbidite system. In contrast, the asymmetrical E-W trending system exhibits more the character of channels previously interpreted within the chalk as bottom-current features. It seems thus likely that a combination of gravity-driven processes and bottom currents influenced chalk channel development in the study area. It should be noted, however, that sinuous, leveed deepwater calciclastic turbidite systems have, to our knowledge, not yet been documented elsewhere in deepwater carbonate depositional environments.

 

AAPG Search and Discovery Article #90135©2011 AAPG International Conference and Exhibition, Milan, Italy, 23-26 October 2011.