As an intermediate basin between coastal and offshore depressions of the California continental borderland, Santa Cruz basin occupies a 1,900-m depression south of the Channel Islands. Steep walls with a thin sediment cover abut the flat basin floor. Hummocky topography, probably related to slumping, characterizes the northwestern quadrant of the basin floor. Three major canyon systems are filling the basin from the northern and southern island platforms, and buried channels show the previous existence of a fourth system. The western wall is relatively straight and featureless compared with the structural terraces, volcanic knolls, and other irregularities of the eastern slope.

Radiographic and photographic analyses of several box cores and numerous gravity and piston cores reveal a complex pattern of sedimentation. Paired cores indicate that this may be related partly to coring technique. Biologic structures are abundant, in many places disrupting sedimentary structures so greatly that they become almost indiscernible. Geologic structures, primarily related to very calcareous sand layers with

End_Page 461------------------------------

associated cross-bedding, laminations, and other "turbidite" features, indicate that much of the basin fill comes from the insular shelves surrounding the basin.

End_of_Article - Last_Page 462------------