Rb-Sr and 40Ar-39Ar geochronological studies on the Precambrian rocks in the Minnesota River Valley.
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چکیده
منابع مشابه
40Ar/39Ar geochronology of the Eocene Green River Formation, Wyoming
The deposits of Eocene Lake Gosiute that constitute the Green River Formation of Wyoming contain numerous tuff beds that represent isochronous, correlatable stratigraphic markers. Tuff beds selected for 40Ar/39Ar analysis occur within laminated mudstone, are matrix supported, and lack evidence of reworking. These tuffs contain 2%–15% euhedral phenocrysts of quartz, plagioclase, sanidine, biotit...
متن کاملThe case for a younger Imbrium basin: New 40Ar-39Ar ages of Apollo 14 rocks
Petrographically and chemically well-characterized rocks of the Apollo 14 landing site (12 impact melt breccias, 3 clast-free impact melt rocks, 2 granulitic rocks, 1 cataclastic noritic anorthosite, 1 shocked gabbronorite, 1 mare basalt, and 1 plagioclase single crystal) have been dated by the 40Ar-39Ar technique. The samples represent two different formations at the Apollo 14 site: (1) small ...
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چکیده ندارد.
15 صفحه اولHigh-resolution calibration of Eocene strata: 40Ar/39Ar geochronology of biotite in the Green River Formation
The Sixth tuff of the Wilkins Peak Member of the Green River Formation is an important potential calibration point for magnetic stratigraphy, mammalian evolution, and lacustrine processes. However, two recent 40Ar/39Ar ages based on laser fusion of biotite from this important bed are not in agreement with one other. Most large, euhedral biotite from the basal 1 cm give concordant age spectra wh...
متن کاملDiscussion and reply: 40Ar/39Ar geochronology of the Eocene Green River Formation, Wyoming Discussion
Smith et al. (2003, hereafter referred to as Smith et al.) present seven new isotopic ages from the Green River Formation in the greater Green River Basin. These data provide welcome new information in the ongoing effort to develop a coherent and reliable geochronological framework for this large and stratigraphically complex basin. Several of their main conclusions are based on a revised age e...
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ژورنال
عنوان ژورنال: GEOCHEMICAL JOURNAL
سال: 1981
ISSN: 0016-7002
DOI: 10.2343/geochemj.15.17