20. Cone-in-cone and Beef-in-shale Textures from Dsdp Site 330, Falkland Plateau, South Atlantic

Sediments of Late Jurassic to Early Cretaceous age, overlying a continental gneissic basement, were sampled in fifteen cores at Site 330, Falkland Plateau. Thin limestone bands occur at intervals throughout much of the succession represented by Cores 3 through 14. Many of the limestones, which vary in thickness from two or three centimeters to several tens of centimeters, are characterized by secondary recrystallization features commonly known as "cone-in-cone" and "beef-in-shale." These features are particularly well developed in some of the limestone bands of Oxfordian-Kimmeridgian age between Cores 5 and 10 where the intervening olive-black sapropelic claystones have a relativley high organic carbon content (ca 5%). We record some of the textural relationships observed and comment briefly on their origin. Samples for petrographic examination were prepared by smooth grinding the split core sections and etching them with dilute acid to accentuate the shale partings. Some of the more interesting features were later studied in thin section.