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Title: Absolute age constraints on the age and tectonics of the Middle and Late Proterozoic Pahrump Group, southern Death Valley, California

The Pahrump Group unconformably overlies 1.35 Ga granite, is unconformably overlain by the Late Proterozoic Noonday Dolomite, and is divided into the Crystal Spring Formation, the Beck Spring Dolomite, and the Kingston Peak Formation. Contacts between these formations are gradational through several meters of interbedded clastic and carbonate rocks. Lithologic data, sedimentary structures, and fossil assemblages suggest that the Pahrump Group, from middle Crystal Spring to lower Kingston Peak time, was deposited in an intratidal to supratidal environment. Diamictite, volcanic ash, and mono lithologic megabreccia suggest that the middle and the upper members of the Kingston Peak Formation were deposited in a higher energy sedimentary and tectonic environment. Dikes and sills of 1.08 Ga diabase intrude the gneiss and all members of the Crystal Spring Formation; erosional clasts of diabase first appear in the middle Kingston Peak Formation. The diabase sills are up to 450 m thick and have caused at least 20 percent inflation of the Crystal Spring, Beck Spring, and lower Kingston Peak formations. If these sedimentary rocks were deposited at or above wave base, evidence of intraplate rifting or gross stratigraphic inflation is not recorded in the Pahrump stratigraphy until middle and upper Kingston Peak time. Therefore,more » the stratigraphic and petrologic data suggest that the diabase was emplaced in the Crystal Spring Formation during post-lower but pre-middle Kingston Peak time. The Beck Spring Dolomite and the lower Kingston Peak Formation are older than 1.08 Ga; the contact between the lower and the middle Kingston Peak Formation is a regional disconformity that marks significant changes in the depositional and the tectonic environments of the Pahrump Group at about 1.08 Ga.« less
Authors:
 [1] ;
  1. (Geological Survey, Menlo Park, CA (United States))
Publication Date:
OSTI Identifier:
5342684
Report Number(s):
CONF-9305259--
Journal ID: ISSN 0016-7592; CODEN: GAAPBC
Resource Type:
Conference
Resource Relation:
Journal Name: Geological Society of America, Abstracts with Programs; (United States); 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
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; CALIFORNIA; GEOLOGIC FORMATIONS; AGE ESTIMATION; GEOLOGY; DIABASES; DIKES; GEOLOGIC HISTORY; PRECAMBRIAN ERA; TECTONICS; BASALT; DEVELOPED COUNTRIES; GEOLOGIC AGES; GEOLOGIC STRUCTURES; IGNEOUS ROCKS; NORTH AMERICA; ROCKS; USA; VOLCANIC ROCKS 580000* -- Geosciences