Ages of rocks in southwestern Washington and northwestern Oregon as indicated by paleontological and isotopic dates

Abstract

This report presents a compilation of 1,019 paleontologic dates and 301 isotopic dates of rocks in southwestern Washington and northwestern Oregon. The study area extends from Portland, Oregon (latitude 45°30' N.) to Bellevue, Washington (latitude 47°35f N.) and from the east flank of the Cascade Range (longitude 121°20f W.) to the coastline (longitude approximately 124°00f W.). The data are presented in two tables and come from previous summaries of isotopic ages, open-file reports, published papers and maps, and theses. Parke D. Snavely, Jr. of the U.S. Geological Survey and Weldon W. Rau of the Washington Division of Geology and Earth Resources (WDGER) generously allowed us access to files and records of more than 40 years of micropaleontological research in western Washington and Oregon. We also present unpublished data from our research since 1971 in northwestern Oregon. This compilation was undertaken for the southwestern Washington and northwestern Oregon project of the U.S. Geological Survey Evolution of Sedimentary Basins Program. Data compilation was completed in only three months and, therefore, some available data may have been overlooked. We would appreciate being contacted about omissions through:

Stratigraphy and sedimentology of the Raging River Formation (early? and middle Eocene), King County, Washington

“…Time scale is after Harland and others, 1990). Correlation with foraminiferal stages is based on Almgren and others (1988) and Niem and Niem (1992). 4.…”

Analysis of Cenozoic subsidence at three sites in vicinity of the Seattle basin, Washington

“…W. Rau is presently preparing a USGS stratigraphic chart that document the paleontology of strata penetrated in about 24 petroleum boreholes from western Washington and northwestern Oregon, and data from the Mobil Kingston #1 borehole cited in this report are part of that effort. Ages were assigned to foraminiferal stages following Armentrout and others (1983a), Prothero and Armentrout (1985), Almgren and others (1988), and Niem and Niem (1992).…”