--> ABSTRACT: Stratigraphy of Deep-Water Turbidites, Part I: A Dynamic Geomorphological Approach, by H. W. Posamentier, W. R. Morris, S. P. Ross, and J. A. Lorsong; #91021 (2010)

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Stratigraphy of Deep-Water Turbidites, Part I: A Dynamic Geomorphological Approach

POSAMENTIER, HENRY W., WILLIAM R. MORRIS, STEVEN P. ROSS, and JAMES A. LORSONG

Deep-water turbidite systems commonly can be subdivided into three geomorphological provinces: I) a tributive canyon (or gully) province, II) a turbidite valley province, and III) a distributive or braided turbidite channel complex. Reservoir facies vary predictably within each of these provinces. The canyon segment of this tripartite arrangement serves as the conduit for sediment gravity flows emanating at the shelf edge and is predominantly erosional and incised into the slope. Levees are not commonly observed in this part of the system. Canyon fill deposits primarily comprise slump and hemipelagic sediments, except m some active margin settings where the fill can also comprise coarse grain material. The canyons (or gullies) feed turbidite valleys of province II where slope gradients lessen significantly. The turbidite valleys commonly contain multiple channel threads between the master levees. The valley fills can be both erosional as well as depositional, though aggradational stacking ultimately characterizes the fill. Amalgamated channelized deposits with minimal shale breaks characterize deposits from within the turbidite valley, whereas the levee deposits are characterized by relatively continuous interbedded shale and thin-bedded sandstone. Turbidite valleys can range in width from less than 100 m to greater than 8 km, and in length from a few 100 m to 100s of km. Farther downslope, turbidite valleys feed the turbidite channel complex of province III. This complex comprises multiple relatively small channels that spread out from the individual leveed turbidite valley of province II. Deposits within province III are predominantly aggradational and progradational, and are laterally extensive due to widespread avulsions. Discontinuous shale breaks are common in this province.

All turbidite systems are characterized by this tripartite system though the relative dominance as well as the absolute magnitude of each province can vary greatly depending on a number of factors including 1) sand to mud ratio within flows, 2) continuity vs. episodicity of flows, 3) volume 0 flows, and 4) physiographic setting (e.g., length and gradient of slope, irregularity of sea floor, etc.). From a sequence stratigraphic perspective, it is notable that with the exception of the physiographic setting, each of the aforementioned factors can vary systematically with change of sea level. Thus the sequence stratigraphic expression, though highly variable, can nonetheless be predictable. 

AAPG Search and Discovery Article #91021©1997 AAPG Annual Convention, Dallas, Texas.