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Evolution of a Conglomeratic Submarine Channel Complex on Sierra del Toro, Cerro Toro Formation, Magallanes Basin, Chile

Zane Jobe
Department of Geological and Environmental Sciences
Stanford University Stanford, CA, U.S.A. [email protected]

     Submarine channels serve as major conduits for the transport of coarse sediment into deep water and their deposits commonly contain excellent reservoir quality sands. It is imperative to understand the evolution of these channel systems and their fill in order to gain insight into channelized petroleum reservoirs. Outcrops of very coarse-grained channel-fill units in the Upper Cretaceous Cerro Toro Formation in the northern Magallanes retro-arc foreland basin of southern Chile allow for detailed study of submarine channel deposits, their evolution, and reservoir implications.
     Outcrops on Sierra del Toro consist of three discrete conglomeratic submarine channel complexes separated by thick mudstone intervals. The youngest and largest channel complex (5-6 kilometers wide and > 300 meters thick), informally named the “Montés” channel complex, is the focus of this study. The base of the complex shows significant erosional downcutting over 5 kilometers in a proximal to distal sense. This may be reflecting local gradient changes and/or a larger scale change in the depositional system. Internally, the Montés complex evolved as an aggradational channel complex that became wider or less confined through time. Ongoing research is aimed at comparing the degree of erosional downcutting of the channel with the amount, if any, coeval levee construction in order to understand the type of confinement of these Cerro Toro channel complexes.

 

AAPG Search and Discovery Article #90070 © 2007 AAPG Foundation Grants in Aid