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...
Six early to middle Tertiary geologic units crop out in the
Saddle and Humbug Mountain area. They include the late Eocene to
early Miocene Oswald West muds tones, the lower Silver Point and
the upper Silver Point tongues of the middle Miocene Astoria Formation,
and the middle Miocene Depoe Bay...
The upper Eocene to lower Oligocene Oswald West mudstone is
the oldest formation (informal) in the Green Mountain-Young's
River area. This 1,663 meter thick hemipelagic sequence was deposited
in a low-energy lower to upper slope environment in the Coast
Range forearc basin. The formation ranges from the late Narizian
to...
Lower and Middle Devonian strata crop out on the former
stable carbonate platform that existed in the Quinn Canyon Range,
through the carbonate shelf edge in the Pancake Range, to the
carbonate slope and outer-shelf basin in the Reveille Range.
The strata of the Reveille Range record a transition from...
Sequence stratigraphic analysis of the southern Tyee basin, Oregon Coast Range, reveals that the lower to middle Eocene forearc and subduction zone strata comprise four depositional sequences. Sequence I (lower Umpqua Group) represents a partially subducted accretionary wedge. Sequence II (upper Umpqua Group) is a deltaic sequence that filled irregular...
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...