A Proposed Model for Late Eocene Paleogeographic Transitions of Western Oregon and Washington Reconstructed from Stratigraphic Relationships, Facies Interpretation, and Paleoecological Analysis of Fossil Assemblages
Abstract
Eocene rifting between the Kula and Farallon plates of Western North America resulted in the formation of a string of volcanic islands along northwestern Oregon and southwestern Washington, which were later accreted to the continent. Previously undescribed flora assemblages from these islands reflect a low-level coastal swamp dominated by Sabalites and Platanophyllum, backed by higher altitude uplands with lacustrine deposits dominated by Pinus, Picea, and Chamaecyparis. Diversity of one of the assemblages allows a paleoclimate analysis based on foliar physiognomy. These assemblages apparently correlate with the late Ravenian flora stage in the Pacific Northwest, a period formerly lacking a definitive marine-nonmarine correlation. Furthermore, these strata, assigned to the upper Narizian foraminiferal stage, seem to correlate with the hydrocarbon producing strata of the Mist Gas Field. (JHD)
Document Details
- Document Type
- Technical Report
- Publication Date
- Jul 07, 1989
- Accession Number
- ADA216266
Entities
People
- John E. Ries
Organizations
- United States Naval Academy