Abstract

At least fifteen diagenetic minerals are present in the sandstones of the Temblor Formation and McAdams sandstone (Tertiary) at Kettleman North Dome. Glauconite, phosphatic pellets, dolomite, pyrite, and kaolinite formed during early diagenesis, whereas quartz, albite, K feldspar, laumontite, sphene, montmorillonite, more kaolinite, mica, anhydrite, barite, and calcite crystallized later at temperatures of about 100 degrees C and depths of as much as 4600 m. Quartz overgrowths are present throughout the section. Albitized plagioclase and albite overgrowths are also common throughout, but more abundant in the Temblor than in the McAdams. K feldspar overgrowths occur sporadically in both the Temblor and the Mcadams. Diagenetic sphene, laumontite, and montmorillonite occur in dacitic arenites toward the bottom of the Temblor, and anhydrite is a cement in one thin bed of quartz arenites near the bottom of the Temblor. Kaolinite is a cement in the quartzo-feldspathic arenites of the McAdams and mica probably replaces some of this kaolinite. Plagioclase and quartz clasts in Temblor sandstones have a remarkable pattern of fractures produced in place and probably during compaction. Commonly, fractures in the plagioclase are healed by albite. Diagenetic reactions involved usually no more than 10 percent of the rock. For the Temblor zone V, a unit in the basal part of the Temblor, the amounts of aluminum, silicon, and titanium necessary to form the late diagenetic minerals are of the same order of magnitude as the amounts released by alteration of detrital marie minerals, plagioclase, quartz, and volcanic glass in the sandstones. By contrast more sodium and calcium, and less potassium, were used in diagenetic minerals than released by alteration of detrital minerals.

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