To assist in the assessment of the geothermal potential of north-central
California and to aid in defining the geologic transitions
between the physiographic provinces of the Klamath Range, the Cascade
Range, the Modoc Plateau, the Great Valley, and the Sierra Nevada
Range, personnel from the Geophysics Group in the College of Oceanography
at Oregon State University conducted a detailed aeromagnetic
survey extending from 40°15' to 42°00'N latitude and from 120°45'
to l22°45'W longitude.
Two forms of spectral analysis, the energy spectrum and the exponential
methods, were used to make source-top and source-bottom depth
calculations. The magnetic source-bottom depths were interpreted as
Curie-point isotherm depths. Based on the energy spectrum analysis,
several regions with elevated Curie-point isotherm depths were mapped:
(1) the Secret Spring Mountain-National Lava Beds Monument area, (2)
the Mount Shasta area, (3) the Big Valley Mountains area, and (4) an
area northeast of Lassen Peak. The elevated Curie-point isotherm
depths within these areas, as shallow as 4 to 7 km below sea level
(BSL) in the Secret Spring Mountain-National Lava Beds Monument area,
the Mount Shasta area, and the area northeast of Lassen Peak, and 4 to
6 km BSL in the Big Valley Mountains area, imply vertical temperature
gradients in excess of 70°C/km and heat flow greater than 100 mW/m²
when assuming a Curie-point temperature of 580°C. Shallow source-bottom
depths of 4 to 5 km BSL were mapped in the Eddys Mountain area
and interpreted to be the depth of a lithologic contact. Source-top
depths show that the magnetic basement varies from about 3.5 km BSL,
beneath the sedimentary assemblages of the Great Valley and the eastern
Klamath Range, to near sea level in the Cascade Range. The exponential
approximation method yielded source-bottom depths which
agreed, in general, with depths determined by the energy spectrum
method. However, this method appears less reliable and its depth
estimates less accurate compared to the energy spectrum method.
A broad negative anomaly, observed on the total field magnetic
intensity map and low-pass filtered anomaly maps, suggests the sedimentary
rocks of the Klamath Complex underlie Mount Shasta and the
Medicine Lake Highlands. Magnetic lineations are oriented mainly NW. / Graduation date: 1984
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/29281 |
| Date | 01 November 1983 |
| Creators | Huppunen, JoAnne L. |
| Contributors | Couch, Richard W. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
Page generated in 0.002 seconds