Gravity measurements made during 1979 and 1980, combined with
existing gravity measurements, provide data for the interpretation
of upper crustal structures relevant to the assessment of the geothermal
potential of south-central Oregon.
West of Upper Klamath Lake, free-air gravity anomalies trend
north-south and average near 35 mgals. East of Upper Klamath Lake,
free-air gravity anomalies trend west to northwest, and average near
ten mgals.
The complete Bouguer anomaly field exhibits a regional gradient
of nearly .4 mgals/km, which is attributed to the existence of a low-density
upper mantle layer beneath the Basin and Range province. The
large northwest-trending negative anomaly associated with the Klamath
graben suggests a depth of low-density fill of up to 2300 m (7500
feet).
The regional gravity field exhibits a broad regional high over
the area surrounding Klamath Falls which may be caused by a shallow
mantle or a large intrusive body at depth, or may simply be due to
intense silicification of the area by thermal waters.
The residual anomaly field exhibits broad bands of positive
anomalies which enclose the negative anomaly associated with the
Klamath graben. The easternmost of these broad, positive trends may
correspond to the eastern flank of an anticline which may have existed
prior to graben faulting. Positive anomalies west of the graben
coincide with the Mount McLoughlin lineament. A large positive
anomaly located south of Sprague River is interpreted to be a volcanic
center and the heat source for thermal waters found in the
Sprague River Valley.
A two-dimensional cross section near 42°26' N. latitude suggests
that step-like faults form the west side of the Klamath graben. The
model indicates the presence of a high density body south of Sprague
River that is interpreted to be a buried volcanic source for local
extrusive volcanic rocks.
Northwest-trending gravity anomalies west of Upper Klamath Lake
indicate that structural trends of the Basin and Range province extend
into the Cascade Mountains, and suggest that a heat source for
thermal waters may exist beneath the High Cascades, rather than
beneath the areas which exhibit geothermal activity. / Graduation date: 1982
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/29198 |
| Date | 02 July 1981 |
| Creators | Veen, Cynthia A. |
| Contributors | Couch, Richard W. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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