The Pliocene sediments of Ventura field, more than 10,000 ft (3,048 m) thick, were deposited in a deep-sea basin, and subsequently were folded into an anticline. Three approaches were used to investigate sand trends within the basin: (1) facies relations using isopach maps, fence diagrams, and textural analyses of core samples; (2) grain orientation by visual inspection, thin-section analysis, and dielectric-anisotropy measurements; (3) sedimentary structures, mainly cross-bedding.

Facies relations suggest that the sands were deposited as elongate lenticular bodies by laterally restricted westerly flowing currents in deep parts of a deep-sea basin. The sand trends are oriented predominantly east-northeast, approximately parallel with the axis of the present Ventura anticline. Studies of grain orientation and cross-bedding support evidence for approximately east-northeast lower Pliocene sand trends in the Ventura field.

Maximum sand development in the central parts of ancient deep-sea basins in tectonically active areas is in direct contrast to the sand-development patterns in shallower water paralic and platform types of depositional basins. This study suggests that the search for sand reservoirs in tectonically active regions might be directed toward the central parts of ancient depositional basins if paleoecologic and sedimentologic data suggest conditions of deep-sea sedimentation. Parallelism of structural axis and trend of sand bodies in folded deep-sea basins suggests an influence on structural trends by sediment-distribution pattern; anticlinal traps might be expected to coincide with maximum sand development, and stratigraphic traps might be expected on the flanks of such folds.

From detailed isopach maps of sand trends offset by faults it is possible to determine fault displacements accurately. Such evidence indicates that the thrust faults in Ventura field have had right-lateral movements. The Padre Juan fault northwest of the Ventura field is perhaps also a right-lateral fault, offsetting an originally continuous structure into the en-echelon Rincon and Ventura anticlines.