--> Abstract: Deep-water Sedimentary Processes and Systems: The Role of Internal vs. External Controls on Lithology Distribution and Stratigraphy, by Ole J. Martinsen; #90101 (2010)

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Deep-water Sedimentary Processes and Systems: The Role of Internal vs. External Controls on Lithology Distribution and Stratigraphy

Ole J. Martinsen
Statoil Hydro Research, Bergen, Norway

The understanding of deep-water sedimentary processes and systems has developed considerably since Kuenen and Migliorini’s (1950) first publication on the origin of turbidity currents. Still, their primary methods of investigation, flume studies and outcrop work in the Apennines, are still very valid methods today, although new technology has allowed for more accurate assessment of flow parameters, resulting sedimentary architecture and the role of external controls on deposits. Not least has 3D seismic and the study of modern and sub-modern deep-water sedimentary systems with shallow seismic and side-scan sonar been instrumental in capturing new data and insight to allow for a better understanding.

A debate that is still highly active today is the relative role of intrinsic/autocyclic vs. extrinsic/allocyclic mechanisms on flows and sedimentary architecture. Flow processes vary from dilute, bottom-hugging currents through “normal” turbidity currents to huge mass-transport events several 1000s of km3 in scale. Even though the effects of these processes may be considered intrinsic to the deep-water sedimentary system, the causes of such events are usually extrinsic. In such a respect deep-water sedimentary systems are different from most other sedimentary systems because their deposits are dominated by events representing relatively short time periods. In most other sedimentary environments, the deposits record longer time intervals.

Although the range of external controls such as sea level change, climate and various types of tectonics is relatively clear, their relative roles in time and space are uncertain, even in many modern and sub-modern systems. Across small areas, the relative roles of external factors may vary significantly, and it is of utmost importance to analyse each system independently. While previously there was a bias towards understanding deep-water sedimentary systems based on local factors, recent insight into sub-modern and modern systems has shown that changes even at process level in deep-water sedimentary systems are driven by extrinsic factors in the ultimate onshore sediment source area. A complete understanding of deep-water sedimentary systems must involve analysis of updip onshore drainage and the adjacent shallow-marine and slope systems. This complicates analysis of deep-water sedimentary systems at outcrop and ancient systems, where commonly only system remnants are preserved. In addition, another complication involves the question of uniformitarianism: how analogous are current and sub-modern deep-water sedimentary systems to ancient systems?

 

AAPG Search and Discovery Article #90101 © 2010 AAPG Foundation Distinguished Lecturer Series 2009-2010