Regional cross sections and net-sand isopach maps depict the geometry and genetic relations of Maestrichtian deltaic and submarine fan depositional systems in the southern Sacramento and northern San Joaquin basins. The six Starkey sands are multilobed cuspate to lobate deltas with east-west or northeast-southwest axes and apices near Sacramento and Stockton. The overlying sand ("Bunker," "3rd Massive," etc) in the Sacramento Valley is an elongate delta with north-south axes and multiple apices. Submarine fans (lower and upper Winters, Tracy, Blewett, and Azevedo sands) are elongate northwest-southeast, parallel to the basin axis. Most fan shapes are distorted owing to onlap on basin slopes or the cross-valley sill termed the Stockton Arch, but less confined fans show the expected fan shape.

Initially the slope was fault controlled, but the deltas prograded the slope, constricting the basin. Five deltas overtook the prograding slope and fed sand over the shelf edge or through shallow slope channels to the fans. Deltas were abandoned during cyclic sea level rises; during the succeeding progradations, mud was swept out of the deltas and draped over the slope and previous fan. Thus, five cycles of delta progradation, fan growth, delta retreat, and fan abandonment are preserved. As the basin filled and water depth decreased, deltas became larger and fans grew smaller.

Local cross sections show facies relations and lithologies. Cuspate deltas consist mainly of coarsening-upward prodelta mud-delta front/shoreface sand. Elongate deltas are largely delta-plain marsh and channel facies. Fans are mainly thick-bedded (amalgamated) massive to fining-upward sand; bed thickness and grain size decrease in a narrow periphery where fans onlap basin slopes or grade to basin-plain shale. Gas is produced from both suprafans and fan margins.

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