Recently obtained airgun-sonobuoy wide-angle refraction and
reflection profiles provide data to study crustal velocities and
structures along the continental margin of northern California and
Southern Oregon.
In the thick sedimentary wedge at the base of the continental
slope, as many as five distinct layers can be seismically observed,
which range in velocity from 2.13 to 3.32 km/sec. The basement
layers beneath the wedge are disrupted. The profile which crosses
the southeasternmost portion of the Gorda Basin near Cape Mendocino
shows evidence of compression at the base of the slope. Velocities of
3.14 to 5.15 km/sec were obtained for this line. Off the central
Oregon margin on the abyssal plain near the base of the slope, oceanic
layers and 3 overlie a shallow mantle of velocity 7.65 km/sec.
Basement velocities average 4.75 km/sec and sediment velocities varied
from 1.60 to 2.78 km/sec.
The lower slope of the northern California-southern Oregon
margin is characterized by rough, folded structures which trend north-south.
Little recent sediment cover is seen. A velocity of 2.25 km/sec
was obtained for a 520 m-thick surface layer underlain by material
with a refraction velocity of 2.68 km/sec. The abyssal plain
sediments near Cape Mendocino appear to be in the process of being
uplifted and folded into the lower slope, while near Cape Blanco
the lower slope displays sediments which abut against the base of the
slope below a prominent lower shelf bench.
The upper slope shows large anticlinal folds which form the
basement of the upper slope basins, particularly beneath the Klamath
Plateau off Northern California. Velocities obtained from the
sediments of the Klamath Plateau vary from 1.73 to 2.63 km/sec.
The inner shelf region is formed by a synclinal basin controlled
by an outer continental high which parallels the shelf break.
Velocities were studied mainly from refraction arrivals with an
assumed surface sediment velocity of 1.66 km/sec. The underlying
sediment velocities range from 2.07 to 2.75 km/sec.
Evidence of uplift, basement deformation, sediment deformation
within structurally controlled basins, compression features, and the
north-south trending folds all support an imbricate thrust model
for this continental margin. / Graduation date: 1979
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/29227 |
| Date | 11 August 1978 |
| Creators | Keser, Judith |
| Contributors | Johnson, Stephen H. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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