ABSTRACT: Sandstone Provenance and Diagenesis in Relation to Late Cretaceous Regional Depositional Systems and Paleogeography, Sacramento Basin, CA

Karl A. Mertz Jr., Tor H. Nilsen

Petrographic modal analyses of sandstone samples from the Upper Cretaceous Guinda, Forbes, Kione, Marsh Creek, Chico, Starkey, Winters, and Mokelumne River formations of the Sacramento basin reveal that samples are dominated by plutoniclastic and volcaniclastic detritus (generally Qm > P = K > Lv), have mediate plagioclase-to-total-feldspar ratios (0.48-0.65), and have high but variable L_v/L ratios (0.51-0.80). Forbes/Kione sandstones, in comparison to Starkey/Winters samples, have higher proportions of volcaniclastic (plagioclase) to plutoniclastic (Q_m, K) detritus and higher Q_p/total Q and L_m/L_v ratios. The Chico Formation, like the Starkey/Winters, is dominated by plutoniclastic material; in comparison to For es/Kione samples, the Chico has higher total lithic values (L_t), especially in the L_m fraction.

These data strongly support derivation of the sands from the Cordilleran magmatic arc system to the north and east. Sandstones from the Chico, Starkey, Winters, and Mokelumne River formations were derived primarily from the dissected Sierran magmatic arc complex to the east, with a minor but significant secondary source in foothill belt metamorphic complexes. Forbes and Kione sandstones, in contrast, appear to have been derived from the Idaho Batholith and Blue Mountain regions of Idaho/Oregon to the north and northeast. When corrections are applied to account for significant diagenetic dissolution of plagioclase and compactional alteration of lithic fragments (especially L_v), the dissected or transitional arc provenance for most samples is strengthened.

Modal data and paleogeographic reconstructions suggest that during the early and middle Campanian, most detritus in the Sacramento basin was derived from the north/northeast (erosion of the Idaho batholith arc system), reflecting southward progradation of the Kion/Forbes delta-submarine fan system into the longitudinal forearc basin. Input from Sierran sources was minor and restricted to the Chico Formation along the eastern flank of the basin and the Marsh Creek Formation at the southern end of the basin. By the Maestrichtian, the Starkey/Winters delta-submarine fan system and related units in the southern and central Sacramento basin reflect renewed input of abundant plutoniclastic detritus from the Sierran arc system to the east (Rumsey petrofacies); this pattern continued into the late Maestrichtian and Paleogene during deposition of the fluviodeltaic Mokelumne River Formation.

AAPG Search and Discovery Article #91003©1990 AAPG Annual Convention, San Francisco, California, June 3-6, 1990