Abstract

This paper identifies and summarizes the significant geological features of the Tertiary Princeton Submarine Valley system. In broadest terms, the objectives of this study were to analyze this system to gain a clear understanding of the complex feature itself, to use it as a prototype to gain a better understanding of other submarine and subaerial channels and their role in petroleum exploration, and to improve our capability of predicting and recognizing ancient channels in basin analysis and petroleum exploration.

The Tertiary Princeton Submarine Valley system is important because of its size and the part it plays in gas accumulation and several key stratigraphic problems in the Sacramento Valley. It is also one of the largest and best documented submarine valleys, ancient or modern, in the world. It was investigated in detail, therefore, both for its regional importance and its usefulness as a model, to which other similar ancient and modern valleys might be compared.

This feature proves to be two-storied. The older system, the lower Princeton Submarine Valley, is filled with lower Eocene, mostly marine sediments. The younger, upper Princeton Valley is filled with possibly upper Oligocene and lower Miocene fluvial sediments. Except for lower valley exposures at the type Capay Formation, and possibly at the type Vacaville Shale, both valleys are mostly subsurface features. The Sierra Nevada auriferous channels are presumably exposures of some of the lower valley’s eastern tributaries.

The somewhat sinuous, dendritic course of much of the lower valley roughly coincides with that of the Sacramento River and subparalleled a shoreline near the northeastern edge of the Sacramento Valley. Its present length from near Red Bluff to the type Capay west of Woodland is roughly 140 miles (225 km), and its overall length may approximate 165 miles (265 km). Maximum width is approximately 25 miles (40 km). Maximum paleobathymetric relief below shelf depth evidently is over 2800 feet (854 m). The upper valley is similar to the Sacramento Valley in morphology, situation, and extent.

The lower valley fill is almost entirely Capay Formation, which consists mostly of pelite, considerable amounts of sandstone, and some conglomerate. Most of these rocks are turbidites, but some are slide and/or mass flow deposits, all of which progressively filled and shoaled areas exceeding 2800 feet (854 m) in depth. At the northern end, the fill is made up of deep estuarine deposits. Farther south, it probably includes at least one deep-sea fan, and near the mouth, it may include a thin, basal section of Paleocene Meganos pelite.

The upper valley fill is mostly sandstone with many pelite interbeds and some conglomerate, possibly the Valley Springs Formation. It evidently represents meander-belt flood-plain deposits of a large, mixed-load river, with many point bars.

Paleocene subaerial erosion by an ancestral Sacramento River, whose position and course were structurally controlled by downwarping of the Great Valley synclinorium, probably initiated the lower valley. It was possibly a dominant element in the dispersal system of the Paleocene Martinez Formation. The younger valley was eroded by another ancestral Sacramento River that was reactivated by renewed downwarping of the synclinorium.

Closest modern analogues of the lower valley apparently are the San Diego Trough, the Bering Canyon, and the Cap Breton Canyon (Bay of Biscay, Spain). Times of origin and geological histories possibly were similar. The modern Sacramento Valley is an approximate analogue of the upper Princeton Valley.

The lower (submarine) valley is indirectly related to several gas fields and directly related to seven. The upper (subaerial) valley is directly related to four.