Kim Zauderer¹, David C. Mohrig¹

(1) ExxonMobil Upstream Research Company, Houston, TX

ABSTRACT: Initiation of Sinuosity for Turbidity-Current Channels

Detailed mapping of single-cycle seismic elements, located within 1.5 to 2.0 sec of the water bottom, help to constrain the interpretation of processes controlling initial growth of submarine channel sinuosity. Highly sinuous channels (i.e., sinuosity > 1.5) typically are multi-seismic cycle in thickness representing multiple phases of sediment erosion and deposition. It is difficult to reconstruct histories of channel evolution from these amalgamated deposits so we have chosen to focus on the simplest channels and work towards more complex forms.

These smallest channels have a narrow range of widths (75 m - 200 m) and depths (less than 10 m), and possess little detectable evidence of erosion at channel bases. Lateral confinement is entirely the product of selective deposition at channel edges, constructing levees. The channels can typically be mapped over distances ranging from 5 to 20 km in the downstream direction and are very straight in plan view (sinuosity < 1.0001). Possible explanations for a lack of sinuosity associated with these channels include: 1) insufficient time for sinuosity to develop before channel abandonment; 2) low values for channel width-to-depth ratios; and 3) a lack of significant bedload transport of sediment. The latter two act to suppress the development of cross-channel topography necessary to force bend growth. First occurrence of channel sinuosity appears to be associated with detectable amounts of erosion at the bases of these channels. Mechanisms possibly controlling this change in plan form will be discussed

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado