Isostatic Gravity Map with Geology of the Santa Ana 30‘ x 60‘ Quadrangle, Southern California

Langenheim, V. E.; Lee, Tien-Chang; Biehler, Shawn; Jachens, R. C.; Morton, D. M.

Abstract:

This report presents an updated isostatic gravity map, with an accompanying discussion of the geologic significance of gravity anomalies in the Santa Ana 30 by 60 minute quadrangle, southern California. Comparison and analysis of the gravity field with mapped geology indicates the configuration of structures bounding the Los Angeles Basin, geometry of basins developed within the Elsinore and San Jacinto Fault zones, and a probable Pliocene drainage network carved into the bedrock of the Perris block. Total cumulative horizontal displacement on the Elsinore Fault derived from analysis of the length of strike-slip basins within the fault zone is about 5-12 km and is consistent with previously published estimates derived from other sources of information. This report also presents a map of density variations within pre-Cenozoic metamorphic and igneous basement rocks. Analysis of basement gravity patterns across the Elsinore Fault zone suggests 6-10 km of right-lateral displacement. A high-amplitude basement gravity high is present over the San Joaquin Hills and is most likely caused by Peninsular Ranges gabbro and/or Tertiary mafic intrusion. A major basement gravity gradient coincides with the San Jacinto Fault zone and marked magnetic, seismic-velocity, and isotopic gradients that reflect a discontinuity within the Peninsular Ranges batholith in the northeast corner of the quadrangle.

Genre:

USGS Numbered Series

ProdID:

79260

Citation Author:

Langenheim, V. E.; Lee, Tien-Chang; Biehler, Shawn; Jachens, R. C.; Morton, D. M.

Citation Contributing Office:

Geophysics Unit of Menlo Park

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Citation Language:

ENGLISH

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Citation LatN:

0340000

Citation LatS:

0330000

Citation LonE:

-1170000

Citation LonW:

-1180000

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Citation Phsyical Description:

25 p.; map 50 inches by 36 inches; Excel file

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Citation Series:

Scientific Investigations Map

Citation Series Code:

SIM

Citation Series Number:

2951

Citation Search Results Text:

Isostatic Gravity Map with Geology of the Santa Ana 30‘ x 60‘ Quadrangle, Southern California; 2006; SIM; 2951; Langenheim, V. E.; Lee, Tien-Chang; Biehler, Shawn; Jachens, R. C.; Morton, D. M.

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Citation Year:

2006

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citation/reference

Text:

Isostatic Gravity Map with Geology of the Santa Ana 30‘ x 60‘ Quadrangle, Southern California; 2006; SIM; 2951; Langenheim, V. E.; Lee, Tien-Chang; Biehler, Shawn; Jachens, R. C.; Morton, D. M.