The Hecla Hoeck succession in Svalbard is one of the most complete and well-exposed late Neoproterozoic sections of carbonate rocks in the world. It contains the deposits of two glacial episodes and carbon-13 isotopic (d13C) evidence for two other glacial episodes. This preservation is important because evidence suggests that events preceding the metazoan explosion were among the most extraordinary in Earth's history. Prior research indicate that a series of runaway ice albedo catastrophes occurred with each one leading to a virtual collapse of biological productivity in the surface ocean for millions of years. Stratigraphic evidence includes a unique association of glacial diamicrites, cap carbonates, and extreme d13C swings. The Principal Investigator will test the Neoproterozoic "snowball" Earth hypothesis in the Hecla Hoek succession in Svalbard. He will use integrated sequence and chemostratigraphic tools successfully used in Neoproterozoic carbonates worldwide. There is a strong possibility of unforeseen structural complications on such old rocks. Therefore, he will address the classical problem of the "bottomless" Hecla Hoeck geosyncline by testing the hypothesis that a Caledonian extensional detachment separates the Neoproterozoic sedimentary succession of eastern Ny Friesland from the Caledonian metamorphic complex to the west. This bears on the relationship between geon-18 basement to the west and geon-18 basement to the east. This relationship is key to the reconstructions of the North Atlantic in the supercontinent Rodinia. Existing paleogeographic reconstructions of this part of Rodinia are controversial, but they are believed to serve as boundary conditions for models of Neoproterozoic paleoclimate. Argon-argon (4040-3940) stable isotope analyses will be used to establish the geochronolgy.