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Implications of Mass-Transport Processes from the Upper Slope for Deepwater Sedimentation and Sequence Stratigraphic Principles: Examples from the Nile Delta, Eastern Mediterranean Sea

Kertznus, Vanessa R.1; Kneller, Benjamin C.1
1 Department of Geology and Petroleum Geology, University of Aberdeen, Aberdeen, United Kingdom.

We have studied the delta-fed slope system of the Nile Cone in the south-eastern Mediterranean, using conventional 3D seismic reflection data. This analysis allows us to assess the major controls on the evolution of delta-fed slope systems and the wide-ranging implications for the distribution of sand-prone units. The overall architectural development of this system changed not only through geologic time in response to the effects of changes in external controls on the sedimentary dynamics and sediment transfer processes, but also through morphodynamic feedbacks of the slope itself.

During the Pleistocene in particular, the development of the Nile submarine cone took place through alternating phases of construction of the subaerial delta and platform, and of sediment delivery to the deep basin by turbidity flows. However, these mechanisms were modified by major mass failures on the upper slope, producing disruption of the stratigraphic record and deficits of mass in certain portions of the system. The larger of these failures occurred in the areas of additional sediment load associated with shelf-edge systems at the termini of the main delta distributaries. They evacuated large lacunae on the upper slope that subsequently acted as preferred pathways for down-slope turbidity current transport of sediment delivered by those same distributaries. This process tends to fix the sediment pathway. The sedimentary sequences that infill these depressions have a repetitive predictable pattern, typically consisting of stacked channel-levee complexes, and most of the upper slope channel systems are controlled thus. The stratigraphic section localised within these depressions has no equivalent outside the slide scar, or only a relatively condensed section, making stratigraphic correlation problematic.

These observations have important implications not only for the overall development of continental margins and sediment pathway distribution, but also for sequence stratigraphic models. Both the concepts of slope accommodation and the persistence of significant stratigraphic surfaces are called into question in this system.


AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009