Regional subsurface studies indicate that the Upper Cretaceous Kione (deltaic), Starkey (deltaic), Winters (slope), Tracy (slope), and Lathrop (slope) formations accumulated as part of high-constructive delta and slope systems which prograded westward from the Sierra Nevada into the Sacramento basin to contribute part of the terrigenous clastic sediments that filled the Sacramento Valley of California.

Principal facies include those typical of the fluvial-deltaic systems--meander-belt, delta-plain, distributary- and interdistributary-channel, delta-front, prodelta-mud, and turbidite--associated with the distal delta front. Facies in the slope system include sandstone channel fill, and proximal and distal turbidite facies which are part of well-developed, deep-sea fans.

Gas accumulations are related to (1) structures affecting distributary channel-fill reservoirs of the relict delta plain, (2) structures affecting turbidite reservoirs deposited perpendicular to the paleoslope seaward of distal delta-front facies, and (3) submarine-fan reservoirs concentrated in elongate trends of submarine channel-fill sandstone in proximal-fan facies.