T. E. Chase

Monterey Fan, Pacific Ocean

Monterey Fan is the largest modern fan off the California shore. Two main submarine canyon systems feed it via a complex pattern of fan valleys and channels. The northern Ascension Canyon system is relatively inactive during high sea-level periods. In contrast, Monterey Canyon and its tributaries to the south cut across the shelf and remain active during high sea level. Deposition on the upper fan is controlled primarily by the relative activity within these two canyon systems. Deposition over the rest of the fan is controlled by the oceanic crust topography, resulting in an irregular fan shape and periodic major shifts in the locus of deposition.

Monterey Fan: Growth pattern control by basin morphology and changing sea levels

Monterey Fan is the largest modern fan off the California shore. Two main submarine canyon systems feed it via a complex pattern of fan valleys and channels. The northern Ascension Canyon system is relatively inactive during high sea-level periods. In contrast, Monterey Canyon and its tributaries to the south cut across the shelf and remain active during high sea level. Deposition on the upper fan is controlled primarily by the relative activity within these two canyon systems. Deposition over the rest of the fan is controlled by the oceanic crust topography, resulting in an irregular fan shape and periodic major shifts in the locus of deposition.

Potential Petroleum Reservoirs on Deep-Sea Fans off Central California

Evaluation of the petroleum potential of the Monterey and Delgada submarine fans based on single-channel seismic reflection profiles and surficial sediment data indicates two high, six good, and four moderate prospects. Sediment thicknesses in a northwest-southeast basement trough at the base of the continental slope generally exceed 1 km; within internal depressions thicknesses can reach 2 to 3 km. Organic carbon contents up to 1.3 weight percent occur on the upper fan. An average heat flow of 2 HFU suggests the occurrence of a thermal gradient sufficient to exceed catagenic conditions within the trough if potential source beds are old enough.

Potential Petroleum Reservoirs on Deep-Sea Fans Off Central California: ABSTRACT

A variety of potential petroleum reservoirs are indicated in subbottom seismic profiles or implied by the depositional history of the deep-sea fans off central California. The size and extent of both the stratigraphic and tectonic traps off California are large compared to terrestrial analogs as seen only through the crude filter of acoustic profiling. Stratigraphic traps such as buried deep-sea channels, sand lobes, and updip pinch-out sands are produced as a normal consequence of the formation of deep-sea fans. Such stratigraphic traps can be expected on any submarine fan if the sand budget and porosity are sufficient. Slumps of sediment from the continental slope cover large areas of the deep-sea fans, and slumped sediment may isolate and bury channel segments and asso iated sand bodies. Tectonic traps resulting from folding or faulting are rare in deep-water fans. Faulting and folding are more commonly observed in fans from slope basins and from the California borderland and produce both tectonic traps and stratigraphic traps by altering configuration of the basin. Large deep-sea fans are built over irregular oceanic crustal topography that has as much as 2 km of relief. As a result, many localized basins on the middle and outer fan are substantially thicker than much of the adjacent fan. On Monterey fan, for example, these local basins include valleys between abyssal hills and a large fracture-zone trough. End_of_Article - Last_Page 803------------