Tectonic significance of magnetic and gravity data across northern California (lat. 39[degree]N. to lat. 41[degree]N. )

Conference · Thu Apr 01 00:00:00 EST 1993 · Geological Society of America, Abstracts with Programs; (United States)

OSTI ID:5021315

Griscom, A; Roberts, C W; Halvorson, P F ^[1]

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1. Geological Survey, Menlo Park, CA (United States)

Aeromagnetic and isostatic residual gravity maps of an east-west transect across northern California show important tectonic features. A linear magnetic anomaly and west-sloping gradient extends over 300 km along the Franciscan-Great Valley contact (FGC) and across the Klamath Mountains province (KM) north to lat. 40[degree]45'N. The anomaly source lies at depths of 5--10 km beneath the KM and the FGC, and implies that the Franciscan complex of the Coast Ranges is thrust (and wedged) at least 80 km eastward beneath the KM to approximately long. 122[degree]40 minutes W. Calculations on a circular gravity low of [minus]50 mGal centered at the circular Bald Rock pluton (diameter about 15 km) in the Sierran foothills indicate a pluton thickness of about 15 km. The nearby Cascade and Merrimac plutons are located on the gradients of this gravity anomaly, have a relatively minor effect on it, and thus are interpreted to be thick (up to 5 km) laccolithic sills that emanate from the Bald Rock pluton, thinning away from it to a feather edge. Model studies indicate that the northeast contact of the Feather River periodotite body (FRPB) north of lat. 39[degree]40 minutes N. generally dips steeply northeast or vertical. The same contact south of this latitude dips east at angles of about 45[degree] to depths of at least 10 km. Magnetic patterns extending from the northern Sierra across the Cascades to the Klamath Mountains suggest that the FRPB may correlate with the Trinity ophiolite.

• OSTI ID: 5021315
• Report Number(s): CONF-9305259-; CODEN: GAAPBC
• Journal Information: Geological Society of America, Abstracts with Programs; (United States), Vol. 25:5; Conference: 89. annual meeting of the Cordilleran Section and the 46th annual meeting of the Rocky Mountain Section of the Geological Society of America (GSA), Reno, NV (United States), 19-21 May 1993; ISSN 0016-7592
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
CALIFORNIA
GEOLOGIC STRUCTURES
GRAVITY SURVEYS
MAGNETIC SURVEYS
DATA ANALYSIS
GEOLOGIC FAULTS
GEOLOGY
MAGMATISM
PLUTONIC ROCKS
SIERRA NEVADA COLORADO
SUBDUCTION ZONES
TECTONICS
DEVELOPED COUNTRIES
GEOLOGIC FRACTURES
GEOPHYSICAL SURVEYS
IGNEOUS ROCKS
MOUNTAINS
NORTH AMERICA
ROCKS
SURVEYS
USA
580000* - Geosciences