Abstract

Micrite nodules are the only source of Radiolaria within the upper Tithonian to Aptian (Upper Jurassic-Lower Cretaceous) interval of Great Valley Supergroup (GVS), California Coast Ranges. Radiolaria recovered from GVS micrite nodules are either calcified or pyritized. This paper describes a method of extracting well preserved calcified radiolaria from micrites utilizing acetic acid. The same method resulted in the extraction of well preserved Upper Cretaceous planktonic foraminifera from indurated micrite within the Khoy ophiolitic complex of northwestern Iran; from micrite in the Green Horn Formation, Pueblo Colorado; from indurated chalk in the Austin Chalk, Dallas Texas, and from indurated micrite in Albian Duck Creek Formation of Texas. The preservation of extracted radiolaria and planktonic foraminifera from the indurated micrites and chalk is excellent and is often comparable to that found in most DSDP/ODP samples. Assumedly the clay content of the rock, and the chemical homogeneity of the calcified test are the principal reasons for differential solution of the acetic acid.

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