ABSTRACT We present a tephrochronologic/chronostratigraphic database for the Mount Diablo area and greater San Francisco Bay region that provides a spatial and temporal framework for geologic studies in the region, including stratigraphy, paleogeography, tectonics, quantification of earth surface processes, recurrence of natural hazards, and climate change. We identified and correlated 34 tephra layers within this region using the chemical composition of their volcanic glasses, stratigraphic sequence, and isotopic and other dating techniques. Tephra layers range in age from ca. 65 ka to ca. 29 Ma, as determined by direct radiometric techniques or by correlation to sites where they have been dated. The tephra layers are of Quaternary or Neogene age except for two that are of Oligocene age. We correlated the tephra layers among numerous sites throughout northern California. Source areas of the tephra layers are the Snake River–Yellowstone hotspot trend of northern Nevada, southern Idaho, and western Wyoming; the Nevadaplano caldera complex of central Nevada; the Jemez Mountains–Valles Caldera in northwestern New Mexico; the Southern Nevada volcanic field and related source areas in eastern California and west-central Nevada; the Quien Sabe–Sonoma volcanic centers of the California Coast Ranges; and the young Cascade Range volcanic centers of northeastern California and Oregon.

Abstract The Permian strata on the shelves around the Delaware Basin represent more than 1000 meters of carbonates and mixed carbonate/siliciclastic deposits. These strata host vast amount of hydrocarbon, and their stratigraphic architecture is very well understood based on numerous studies form the outcrop in the northern and western part of the basin and a wealth of subsurface data in and around the basin. The stratigraphic evolution of the early to middle Permian mixed carbonate-siliciclastic system is the combined result of a waning tectonic activity and a transition from an ice-house to greenhouse climatic-eustatic signal. Comparing two classic outcrop localities between the south (Glass Mountains) and the north (Guadalupe Mountains) of the basin shows some striking difference in the overall stratigraphic architecture of the Woflcampian, Leonardian, and Guadalupian strata. The Woflcampian and Leonardian in the Glass Mountains is about 75% the thickness of the similar interval in the north and has an overall retrograding architecture compared to an overall prograding motif in the north. In the Glass Mountains, the Leonardian slope (Bone Spring Fm. equivalent) is dominated by silt and coarse-grained gravity flow deposits (turbidites and megabreccia) compared to the huge volume of muddy dilute carbonate turbidites in the Bone Spring Formation of the Guadalupe Mountains. The thinner and mostly retrograding architecture of the Leonardian in the south compared to the northern margins indicates a larger accommodation space versus sediment supply ratio. This difference may be due to either an increased subsidence due to waning tectonic activity or a reduced sediment production and accumulation compared to the north, or a combination of the two. A potential explanation for a reduced sediment production rate might be the large amount of siliciclastics mixed into the carbonate system in the south due to the proximity of the orogenic front compared to a larger mostly purely carbonate Leonardian shelf in the north that produced huge amount of carbonate mud that is exported to the slope and allows for the shelf margin to prograde by more effectively infilling the basin topography. The Guadalupian interval and especially the section from the Vidrio Formation to the end of the Capitan Formation is much more prograding (17 km of basinward step for 500m of thickness) compared to the similar interval in the Guadalupe Mountains (6 km of basinward step from Goat Seep Formation to end Tansill Formation for 300m of thickness). That equates to a P/A ratio of 34 in the Glass Mountains compared to 20 in the Guadalupe Mountains. We hypothesize that the strong influx of sand on the slope and in the basin allowed the Guadalupian reef in the south to build outward in a similar fashion that the mud exported in the basin during the Bone Spring time promoted the progradation of the northern Leonardian shelf in the Guadalupe Mountains. These two overall architecture differences between the south and northern part of the basin point toward a strong control of the overall sediment production rate and accumulation of sediment on the slope combined with antecedent topography and subsidence rate on the stratigraphic architecture of those carbonate shelves experiencing the same eustatic and climatic signal.