Upper Jurassic and Lower Cretaceous radiolaria biostratigraphy of California Coast Ranges.

摘要

Radiolarian faunas from the Upper Jurassic and Lower Cretaceous strata of the Great Valley Supergroup, Northern California Coast Ranges were studied. The Great Valley Supergroup was sampled at Grindstone Creek, Glenn County, California; for the Tithonian to lower Valanginian interval, and at McCarty Creek, Tehama County, California for the upper Tithonian to lower Albian interval. These two localities were chosen because of their biostratigraphic and geochronometric data. Ninety six species, including eighteen new species and one new genus, were identified from the micrite nodules. The radiolarian fauna is very diversified, but not abundant. Nassellarians dominate the fauna. Samples collected from the Grindstone Creek section of the Great Valley Supergroup contain Upper Jurassic (upper Tithonian) to Lower Cretaceous (upper Hauterivian) Radiolaria (Zone 4, Subzone 4 alpha to Zone 5, Subzone 5c). Micrite nodules from the McCarty Creek section yielded upper Tithonian to lower Albian radiolarian. U/Pb geochronometric data from Grindstone Creek section of the Great Valley Supergroup indicate an age of Berriasian. This study also describes a method of extracting well-preserved calcified radiolaria from micrite utilizing acetic acid.