skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Geology of 1. 7 GA ( ) Baldwin gneiss in the Baldwin Lake type area, San Bernardino Mountains, southern California

Abstract

Precambrian gneisses in the San Bernardino Mountains were first identified and described in the vicinity of Baldwin Lake by Guillou (1953). Five lithologic units mappable at 1:24,000 scale are recognized: biotite [+-] muscovite quartzofeldspathic gneiss, amphibolite, pyroxene metagabbro, augen gneiss, and biotite [+-] muscovite granitic gneiss. Baldwin gneiss with this L < S tectonite fabric is unconformably overlain by latest Proterozoic, upright, greenschist/hornfels facies quartzite (Big Bear Group). North and northeast of Baldwin Lake, the gneissic fabric is rotated toward the northwest, subparallel to the Doble fault. Along this fault, Baldwin gneiss is structurally underlain by overturned Paleozoic quartzite and marble (Zabriskie Quartzite and Carrara Formation). Regional relations suggest that the Doble fault is a northeast-directed basement thrust fault of pre-Late Cretaceous age, and may be contemporaneous with late Paleozoic deformation and metamorphism of Paleozoic rocks further west in the range. Field relations suggest that Baldwin gneiss in its type area largely retains Proterozoic fabrics and mineral assemblages, despite marginal Phanerozoic reworking. Silver (1971) reported a U-Pb zircon age of ca. 1,730 Ma for Baldwin augen ( ) gneiss, from an unknown locality, and Miller and Morton (1980) reported Late Cretaceous mica K-Ar ages from a sample of augen gneiss.more » Preliminary Pb isotopic ratios in galena, feldspar and whole rock samples of Baldwin gneiss, and feldspars in Mesozoic plutons suggest isotopic affinity to the Mojave crustal province of Wooden and Miller (1990).« less

Authors:
 [1];  [2];  [3]
  1. Indiana/Purdue Univ., Indianapolis, IN (United States). Dept. of Geology
  2. California State Univ., Los Angeles, CA (United States). Dept. of Geology
  3. Geological Survey, Menlo Park, CA (United States)
Publication Date:
OSTI Identifier:
5423093
Report Number(s):
CONF-9305259-
Journal ID: ISSN 0016-7592; CODEN: GAAPBC
Resource Type:
Conference
Journal Name:
Geological Society of America, Abstracts with Programs; (United States)
Additional Journal Information:
Journal Volume: 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; Journal ID: ISSN 0016-7592
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; CALIFORNIA; GEOLOGIC FORMATIONS; ISOTOPE DATING; PETROGENESIS; PETROLOGY; GNEISSES; ARGON ISOTOPES; GEOLOGY; LEAD ISOTOPES; LITHOLOGY; MINERALOGY; PARAGENESIS; PETROCHEMISTRY; POTASSIUM ISOTOPES; PRECAMBRIAN ERA; URANIUM ISOTOPES; ZIRCON; ACTINIDE ISOTOPES; AGE ESTIMATION; ALKALI METAL ISOTOPES; DEVELOPED COUNTRIES; GEOLOGIC AGES; ISOTOPES; METAMORPHIC ROCKS; MINERALS; NORTH AMERICA; ROCKS; SILICATE MINERALS; USA; 580000* - Geosciences

Citation Formats

Barth, A P, Ehlig, P L, and Wooden, J L. Geology of 1. 7 GA ( ) Baldwin gneiss in the Baldwin Lake type area, San Bernardino Mountains, southern California. United States: N. p., 1993. Web.
Barth, A P, Ehlig, P L, & Wooden, J L. Geology of 1. 7 GA ( ) Baldwin gneiss in the Baldwin Lake type area, San Bernardino Mountains, southern California. United States.
Barth, A P, Ehlig, P L, and Wooden, J L. 1993. "Geology of 1. 7 GA ( ) Baldwin gneiss in the Baldwin Lake type area, San Bernardino Mountains, southern California". United States.
@article{osti_5423093,
title = {Geology of 1. 7 GA ( ) Baldwin gneiss in the Baldwin Lake type area, San Bernardino Mountains, southern California},
author = {Barth, A P and Ehlig, P L and Wooden, J L},
abstractNote = {Precambrian gneisses in the San Bernardino Mountains were first identified and described in the vicinity of Baldwin Lake by Guillou (1953). Five lithologic units mappable at 1:24,000 scale are recognized: biotite [+-] muscovite quartzofeldspathic gneiss, amphibolite, pyroxene metagabbro, augen gneiss, and biotite [+-] muscovite granitic gneiss. Baldwin gneiss with this L < S tectonite fabric is unconformably overlain by latest Proterozoic, upright, greenschist/hornfels facies quartzite (Big Bear Group). North and northeast of Baldwin Lake, the gneissic fabric is rotated toward the northwest, subparallel to the Doble fault. Along this fault, Baldwin gneiss is structurally underlain by overturned Paleozoic quartzite and marble (Zabriskie Quartzite and Carrara Formation). Regional relations suggest that the Doble fault is a northeast-directed basement thrust fault of pre-Late Cretaceous age, and may be contemporaneous with late Paleozoic deformation and metamorphism of Paleozoic rocks further west in the range. Field relations suggest that Baldwin gneiss in its type area largely retains Proterozoic fabrics and mineral assemblages, despite marginal Phanerozoic reworking. Silver (1971) reported a U-Pb zircon age of ca. 1,730 Ma for Baldwin augen ( ) gneiss, from an unknown locality, and Miller and Morton (1980) reported Late Cretaceous mica K-Ar ages from a sample of augen gneiss. Preliminary Pb isotopic ratios in galena, feldspar and whole rock samples of Baldwin gneiss, and feldspars in Mesozoic plutons suggest isotopic affinity to the Mojave crustal province of Wooden and Miller (1990).},
doi = {},
url = {https://www.osti.gov/biblio/5423093}, journal = {Geological Society of America, Abstracts with Programs; (United States)},
issn = {0016-7592},
number = ,
volume = 25:5,
place = {United States},
year = {Thu Apr 01 00:00:00 EST 1993},
month = {Thu Apr 01 00:00:00 EST 1993}
}

Conference:
Other availability
Please see Document Availability for additional information on obtaining the full-text document. Library patrons may search WorldCat to identify libraries that hold this conference proceeding.

Save / Share: