Biostratigraphy and Paleoecology of Naples Bluff Coastal Section Determined from Diatoms and Benthic Foraminifers: ABSTRACT

Abstract

An integrated biostratigraphic and paleoecologic study of the Naples Bluff coastal section used diatoms and benthic foraminifers. This section, composed of a thick sequence of Tertiary marine rocks, represents one of the most completely exposed Neogene sections along the central coast of California. The interval examined in this study is 1800 ft thick, and represents early to late Miocene rocks and the overlying early Pliocene sediments. This sequence contains well-preserved diatom floras and benthic foraminiferal faunas that enabled us to integrate diatom biochronology with the provincial benthic foraminifer stages and to construct a sediment accumulation curve. Although generally abundant in this section, the benthic faunas are dominated by an inner marginal bathyal assemblage. However, rare deeper water assemblages occur in some samples. Five faunal events are recognized that indicate response to paleo-oceanographic and tectonic influences. The diatom assemblages in this section are relatively abundant and range from the Actinocyclus ingens zone to the Thalassiosira oestrupii zone of J.A. Barron. The diversity and abundance of these assemblages made precise age control for this section possible. A major unconformity or severely compressed interval developed between 15 and 9 Ma.