The Permian rocks near Quinn River Crossing, Humboldt County,
Nevada, crop out as a north-trending block-faulted ridge and consist
of more than 2600 feet of middle Permian fossiliferous limestone.
About 1000 feet of unfossiliferous cherty shales, sandstones, and
conglomerates are associated with the limestone and are assumed also
to be...
Since the early 1950's, the distribution of sediment at the
mouth of Redwood Creek has been altered by the effects of channel
aggradation and channelization along the lower reach. Severe flooding
in 1953, 1955, and 1964 caused bank erosion, landsliding, and
channel geometry changes along Redwood Creek. The increased sediment...
About 7,000 years ago two major tephra-falls blanketed the
Pacific Northwest in volcanic ash. These two tephra-falls, identified
as the Llao and climatic tephra-falls, were a part of the eruptive
events that led up to the collapse of Mount Mazama to form Crater Lake
in the southern Oregon Cascades.
The...
The Paleocene-lower Eocene volcanic rocks of the southern Oregon Coast Range
Roseburg Formation are the oldest remnant eruptive sequence of an oceanic islandseamount
province which is presently exposed along a north-south lineament that stretches
from Vancouver, B.C. into southwestern Oregon. This seamount terrane is thought to
have formed on the...
Andesitic and rhyolitic magmatism was active during the mid-
Tertiary (Early Miocene) of the Ash Peak area, southeastern Arizona.
Andesitic magmas of similar composition both preceded and followed the
low- and high-silica rhyolitic magmas. The changes from andesitic to
rhyolitic and back to andesitic volcanism is postulated to be the...
The Sulaiman foldbelt is an active and conspicuous tectonic
feature on the northwestern margin of the Indo-Pakistani plate.
Seismic reflection data have been combined with surface geological
mapping and drillhole data to interpret the structural style and
tectonic shortening of the eastern Sulaiman foldbelt and its adjacent
foredeep. The data...