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The AAPG/Datapages Combined Publications Database
The morphology and sedimentation patterns of large, deep-ocean submarine fans along the California coast, like Monterey fan, differ from that of smaller borderland or slope-basin submarine fans like the Navy and La Jolla fans. Small borderland fans feature areas of channels, isolated depressions, and a convex upward profile which are characteristic of the area defined as a suprafan and regarded as the location of active sand deposition.
Large submarine fans are not simply scaled-up versions of small fans but seem to have certain features that suggest a composite of many small fans. On large fans, the basin shape and basin topographic features are a significant factor in the location of active turbidite depositional areas and the duration of these areas as principal sites of deposition. Bathymetric highs act as dams, restricting fan progradation, or deflecting the transport of fan sediments. Continued deposition commonly results in breeching topographic barriers, producing a rapid shift of primary depocenters to more distal regions. What was formerly a lower-fan environment may become the site of a middle-fan depositional lobe, and lower-fan deposition moves further seaward. Owing to these abrupt large-scale changes o fan deposition, it is difficult to recognize classic middle-fan environments on large submarine fans. Extensive channel
systems result in sediment bypassing the old middle-fan region. At the lower end of the main valleys on Monterey fan, channels and isolated depressions are observed but the characteristic morphology of suprafans is not clearly developed. Large sediment waves are present on the upper fan valley levee and at various locations on Monterey fan, but are absent on the smaller Navy and La Jolla fans.
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