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Facies Architecture of Slope Channel Complexes, Tres Pasos Formation at Cerro Divisadero, chile

By
Brian W. Romans
Brian W. Romans
1
Department of Geological and Environmental Sciences, Stanford University, Stanford, California, USA
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Michael R. Shultz
Michael R. Shultz
1
Department of Geological and Environmental Sciences, Stanford University, Stanford, California, USA
2
Present address: chevron Energy Technology Company, San Ramon, California, USA
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Stephen M. Hubbard
Stephen M. Hubbard
1
Department of Geological and Environmental Sciences, Stanford University, Stanford, California, USA
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Stephan A. Graham
Stephan A. Graham
1
Department of Geological and Environmental Sciences, Stanford University, Stanford, California, USA
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Published:
January 01, 2008

Abstract

Outcrops of the Upper Cretaceous (Campanian-Maastrichtian) Tres Pasos Formation at Cerro Divisadero, southern chile, expose a >500-m (>1640-ft)-thick succession of clastic deep-water deposits. The Tres Pasos Formation represents the upper portion of a 5000-m (16,400-ft)-thick deep-water succession recording sedimentation in the narrow (<10 km [<6.2 mi]) foredeep of the Magallanes basin. Facies, local paleocurrent data, and regional context from previous work indicate these strata record the southward progradation of a deep-marine slope. The Tres Pasos Formation at Cerro Divisadero consists of four discrete sandstone-rich units (20–50 m [65–150 ft] thick) interbedded with mudstone-rich intervals of comparable thickness. Two of these units are presented here. Paleocurrent information indicates the outcrop is oriented parallel to depositional dip although arroyos provide local three-dimensionality.

The lower sandstone element (C1) is 40–50-m (130–150-ft)-thick and continuous for >2 km (>1.2 mi) parallel to depositional dip. The cliff-face exposure documented here is a representative example of the facies associations and internal architecture. This element is subdivided into two components based primarily on bedding geometry and degree of sandstone bed amalgamation, and separated by thin-bed element Tl. The lower subelement (C1a) has a basal erosional surface, complex internal scouring, and a high sandstone-shale-ratio because of amalgamation of sedimentation units. The upper subelement (C1b) is characterized by wedge-shaped to tabular bedsets and decreased sandstone amalgamation and distinct compensational stacking. The overlying channelform element (C2) is thinner (5–20 m [15–65 ft] thick) and more lenticular than C1. Lower subelement (C2a) has a basal erosional surface and an onlapping heterolithic fill

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Contents

AAPG Studies in Geology

Atlas of Deep-Water Outcrops

Tor H. Nilsen
Tor H. Nilsen
Desceased
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Roger D. Shew
Roger D. Shew
University of North Carolina
Wilmington, North Carolina
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Gary S. Steffens
Gary S. Steffens
Shell International E&P
Houston, Texas
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Joseph R. J. Studlick
Joseph R. J. Studlick
Maersk Oil America Inc.
Houston, Texas
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American Association of Petroleum Geologists
Volume
56
ISBN electronic:
9781629810331
Publication date:
January 01, 2008

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