Ki. Mahon et al., THE THERMAL AND CEMENTATION HISTORIES OF A SANDSTONE PETROLEUM RESERVOIR, ELK HILLS, CALIFORNIA - PART 1 - AR-40 AR-39 THERMAL HISTORY RESULTS/, Chemical geology, 152(3-4), 1998, pp. 227-256
Recent developments in K-feldspar Ar-40/Ar-39 thermochronometry have p
rovided new tools to deal with interpretive impediments that previousl
y limited its application to investigating sedimentary basin thermal h
istories. These new methodologies were applied to detrital K-feldspars
recovered at various depths from a deep well drilled through a carbon
ate-cemented sandstone petroleum reservoir in the southern San Joaquin
Valley, California. Thermal histories obtained from both thermochrono
logical analysis and burial history constraints were used to constrain
a conductive heat flow model of basin evolution. The basin appears to
have experienced a broadly linear heating history due to burial throu
ghout the early and middle Miocene followed by a significant increase
in heating rate between 9 and 6 Ma. In a companion paper [Mahon, K.I.,
Harrison, T.M., McKeegan, K.D., 1998. The thermal and cementation his
tories of a sandstone petroleum reservoir, Elk Hills, California. Part
2: In situ oxygen and carbon isotopic results. Chem. Geol. 152, 257-2
71], we apply the thermal model to predict the temperature evolution o
f the much shallower late Miocene Stevens sands, a prolific petroleum
producer. Ratios of excess Ar-40 to chlorine calculated from the diffe
rential release of radiogenic and nucleogenic argon during isothermal
heating steps indicate a uniform value of 5.4 +/- 0.9 x 10(-5) over th
e 2.5 km vertical distance separating the samples from well 934-29R su
ggesting that the basin receives a high basal flux of radiogenic argon
. (C) 1998 Elsevier Science B.V. All rights reserved.