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Paleo-oceanographic Circulation as Determined from Radiolarian Populations in Humboldt Basin

C. O. Nelson, A. L. Weinheimer

Analyses of radiolarian assemblages from middle Miocene to Pliocene samples along a transect in the Humboldt basin were utilized to determine the presence of various water masses at key time planes off of the coast of northern California. Structural analyses indicate that the basin has acted as a "structural" unit throughout the Miocene to present. Therefore it was possible to infer paleophysiography by assuming that the past continental shelf geometry was similar to that of the present. Radiolarian fauna indicate that initial deposition was in a basin open to deep marine waters. Through time and in an east to west direction, the radiolarian populations exhibit increasingly shelfal characteristics, and from these data nearshore paleo-oceanic circulation was determined.

AAPG Search and Discovery Article #91038©1987 AAPG Annual Convention, Los Angeles, California, June 7-10, 1987.