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Open-File Report 2011-1028


Review of the Origin of the Braid Scarp near the Pebble Prospect, Southwestern Alaska

By Peter J. Haeussler and Christopher F. Waythomas

ABSTRACT

A linear geomorphic scarp, referred to as the “Braid Scarp,” lies about 5 kilometers north of Iliamna Lake, Alaska, and has been identified as a possible seismically active fault. We examined the geomorphology of the area and an 8.5-meter-long excavation across the scarp. We conclude that the scarp was formed by incision of a glacial outwash braid plain into a slightly older outwash plain as ice stagnated in the region during deglaciation 11–15 thousand years ago. We found no evidence for active faulting along the scarp.

First posted February 15, 2011

For additional information contact:
Director, Alaska Science Center
U.S. Geological Survey
4210 University Dr.
Anchorage, Alaska 99508-4650
http://alaska.usgs.gov

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Suggested citation:

Haeussler, P.J., and Waythomas, C.F., 2011, Review of the origin of the Braid Scarp near the Pebble prospect, southwestern Alaska: U.S. Geological Survey Open-File Report 2011-1028, 14 p.



Contents

Abstract

Introduction

Quaternary Geology and Geomorphology of the Braid Scarp

Deposits Exposed in Braid Scarp Trench

Interpretation of Trench Deposits and Surface Features

Discussion

Recommendations for Future Work

Acknowledgments

References Cited


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