Sedimentary basin thermal histories through /sup 40/Ar//sup 39/Ar analysis of detrital microcline

Conference · Fri Feb 01 04:00:00 EST 1985 · Am. Assoc. Pet. Geol., Bull.; (United States)

OSTI ID:5782455

Harrison, T M

The /sup 40/Ar//sup 39/Ar age spectrum technique has the demonstrated ability to resolve gradients of /sup 40/Ar within crystals resulting from geologic heatings. A practical application of this observation is the analysis of detrital microcline from sedimentary beds to assess the source age of the feldspar, the time of basin heating, and the thermal intensity of the heating event. This intensity of the heating event is available through knowledge of the amount of /sup 40/Ar lost from the sample and the temperature-dependent rate of argon transport within microcline. Both of these parameters are obtained as a by-product of the age spectrum experiment. Results from a variety of sedimentary basins are encouraging and demonstrate the quality of information available from this technique. /sup 40/Ar gradients in samples from the Basin block of the southern San Joaquin Valley, California, indicate a heating duration of 500,000-1 m.y., which is consistent with the stratigraphy. In conjunction with the present heat-flow data, these results suggest an equilibrium thermal gradient approx. 7/sup 0/C/km higher than that presently observed - a consequence of rapid burial. K-spar separates from deep drill holes in the Albuquerque basin, New Mexico, reveal age spectra characteristic of substantial /sup 40/Ar loss. Thermal calculations based on these data indicate a simple conductive history for samples above a present depth of about 6 km, although hydrothermal activity is evident in deeper material. Microcline separates have been obtained from a Kimmeridigian Sandstone (tartan field, North Sea basin) that has been displaced about 1 km by a normal fault. Age spectra from these samples reveal minor /sup 40/Ar losses of 4 and 6% from the samples in the upthrown and downthrown blocks, respectively. These loss profiles correspond to temperature histories that agree well with the formation temperatures and burial histories estimated for these wells.

• Research Organization: State Univ. of New York, Albany
• OSTI ID: 5782455
• Report Number(s): CONF-850322-
• Conference Information: Journal Name: Am. Assoc. Pet. Geol., Bull.; (United States) Journal Volume: 69:2
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
020200* -- Petroleum-- Reserves
Geology
& Exploration
ARGON 39
ARGON 40
ARGON ISOTOPES
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
CHEMISTRY
EVEN-EVEN NUCLEI
EVEN-ODD NUCLEI
FELDSPARS
GEOCHEMISTRY
GEOLOGIC HISTORY
GEOLOGIC STRUCTURES
ISOTOPE RATIO
ISOTOPES
LIGHT NUCLEI
MATURATION
MINERALS
NUCLEI
RADIOISOTOPES
SEDIMENTARY BASINS
STABLE ISOTOPES
YEARS LIVING RADIOISOTOPES