The middle to upper Eocene Tillamook Volcanics form the basement in the Rock Creek - Rocky Point area. These tholeiitic to alkalic basalts, basaltic andesites, and andesites were erupted as shield volcanoes seaward of the strandline ontop of an older deep-marine mudstone unit (Yamhill Formation) and an accreted portion of...
The early to middle Eocene submarine basalts of the Crescent Formation form the
core and basement of the structurally uplifted Willapa Hills region of southwest
Washington. The formation consists of a thick sequence of predominantly subalkaline,
tholeiitic pillow basalts and breccias formed as oceanic crust and seamounts at a sea...
A composite 732-rn thick section in Germany Creek of middle Eocene upper McIntosh and lower Cowlitz Formations, as well as the lower Grays River Volcanics, was studied using bio-, magneto- and lithostratigraphy to construct a sequence stratigraphic framework and assess hydrocarbon exploration potential. The upper McIntosh Formation forms a complete...
Since 1979, over $114 million of natural gas has been produced at the Mist Gas Field, currently the only commercial gas field in the Pacific Northwest. In the Mist Gas Field, the sandstone-dominated Clark and Wilson member of the upper Eocene Cowlitz
Formation is the reservoir and the overlying upper...
The middle Eocene Tillamook Volcanics form the oldest rock unit in the Elsie-lower Nehalem River area. K-Ar age determinations and age constraints imposed by foraminiferal and calcareous nannofossil assemblages of overlying sedimentary strata indicate an absolute age of about 42 Ma for the uppermost Tillamook Volcanics. Major oxide values indicate...
Geologic mapping of the Longview-Kelso area and the measurement and description of a composite 650-meter thick stratigraphic section of the Cowlitz Formation (Tc) in Coal Creek using bio-, magneto-, litho-, and sequence stratigraphy reveals a complex interplay of Cowlitz micaceous, lithic arkosic shelf to tidal/estuarine to delta
plain facies associations,...
This field trip consists of two geologic tours. On Tour 1, the Tertiary sedimentary rocks exposed along the Yaquina River between Newport and Toledo, Oregon, will be examined. This tour will start at the mouth of Yaquina Bay where Miocene sedimentary rocks are exposed and will proceed generally eastward and...