Skip to Main Content
Book Chapter

Geology and paleontology of the early Tertiary Chuckanut Formation

By
G.E. Mustoe
G.E. Mustoe
Geology Department, Western Washington University, Bellingham, Washington 98225, USA
Search for other works by this author on:
R.M. Dillhoff
R.M. Dillhoff
Evolving Earth Foundation, P.O. Box 2090, Issaquah, Washington 98027, USA
Search for other works by this author on:
T.A. Dillhoff
T.A. Dillhoff
Geology Department, Western Washington University, Bellingham, Washington 98225, USA
Search for other works by this author on:
Published:
January 01, 2007

Abstract

Eocene nonmarine sedimentary rocks that occur in northwest and central Washington as a widespread series of outcrops are evidence of a meandering river system that existed prior to the mid-Tertiary uplift of the North Cascade Range. Arkosic strata appear to have initially been deposited in a basin that was later divided by strike-slip faulting, producing outcrops of the Swauk Formation on the eastern flank of the North Cascades, and the Chuckanut Formation to the west. Plant fossils are abundant in both formations, but the Swauk paleoflora has received little study. The Chuckanut Formation paleoflora records a marked shift in the region’s paleoclimate. The Late Paleocene to Middle Eocene Bellingham Bay and Slide Stratigraphic Members, which comprise the lower 6000 m of the formation, contain diverse assemblages of subtropical plant fossils. In contrast, the overlying 3000-m-thick Padden Member contains taxa indicative of a warm temperate paleoclimate. An unconformity may separate the Padden Member from older Chuckanut strata, and the age of the Padden Member has not been determined. The climate shift may have been a Late Eocene fluctuation, but the possibility that the floral changes represent the transitional Eocene-Oligocene cooling event cannot be discounted. Animal fossils from the Chuckanut Formation include aquatic mollusks and a soft-shelled turtle, and track impressions from a variety of birds and mammals.

You do not currently have access to this article.

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

Citing Books via

Close Modal
This Feature Is Available To Subscribers Only

Sign In or Create an Account

Close Modal
Close Modal