Skip to Main Content
Book Chapter

Regional Tertiary sequence stratigraphy and structure on the eastern flank of the central Cascade Range, Washington

By
Eric S. Cheney
Eric S. Cheney
Department of Earth and Space Sciences, Box 3513l0, University of Washington, Seattle, Washington 98195-1310, USA
Search for other works by this author on:
Nicholas W. Hayman
Nicholas W. Hayman
Division of Earth and Ocean Sciences, Box 90227, 103 Old Chemistry Building, Duke University, Durham, North Carolina 27708, USA
Search for other works by this author on:
Published:
January 01, 2007

Abstract

Eocene sedimentary and volcanic rocks on the eastern flank of the Cascade Range consist of five regional, unconformity-bounded formations of the Challis synthem. These formations define a series of northwesterly striking folds. Five anticlines are 9 to 28 km apart, have pre-Tertiary crystalline rocks in their cores, high-angle reverse faults on their steeper northeastern limbs, and pass down-plunge into more gentle folds in the Neogene Columbia River Basalt Group (CRBG). Such northwesterly trending folds extend from east of the Columbia River across the Cascade Range to the Puget Lowland.

The Chiwaukum graben and Swauk basin, which heretofore were thought to be local, extensional, depositional basins, are, instead, the major northwesterly trending synclines in this series of folds. The Eocene formations were preserved, not deposited, in these synclines. Dextral, N-S faults cut the reverse faults and the pre-CRBG portion of some of the folds. The post-CRBG folds control the regional distribution of the Eocene formations.

The Cascade Range is a southerly plunging, post-CRBG anticline. Clasts in the Thorp Gravel indicate that this anticline began to rise ca. 4 Ma. The anticline has an amplitude of ∼3.5 km, and it causes the plunges of the northwesterly striking post-CRBG folds. The northerly and northwesterly post-CRBG folds form a regional interference pattern, or “egg-crate,” that dominates the present topography of Washington State.

You do not currently have access to this article.
Don't already have an account? Register

Figures & Tables

Contents

GSA Field Guide

Floods, Faults, and Fire

Pete Stelling
Pete Stelling
Geology Department Western Washington University 516 High St., MS 9080 Bellingham, Washington 98225 USA
Search for other works by this author on:
David S. Tucker
David S. Tucker
Geology Department Western Washington University 516 High St., MS 9080 Bellingham, Washington 98225 USA
Search for other works by this author on:
Geological Society of America
Volume
9
ISBN electronic:
9780813756097
Publication date:
January 01, 2007

References

Related

A comprehensive resource of eBooks for researchers in the Earth Sciences

Close Modal
This Feature Is Available To Subscribers Only

Sign In or Create an Account

Close Modal
Close Modal