Cap Carbonates

Definition

Cap carbonates are unusual deposits of dolostones and limestones, often enriched in barite, that sharply overlie Neoproterozoic glacial deposits. They are from 2 to 50 m thick and occur on shallow platforms, shelves, and slopes worldwide, even in regions otherwise lacking in carbonate strata.

Glaciation events during the late Neoproterozoic (Cryogenian–Ediacaran) are widespread on Earth, reflecting up to four global ice ages (“Snowball Earth Hypothesis”) between 730 and 580 Ma. Numerous publications dealing with these events exist (for example, see Chapter by Hoffman P.F., Snowball Earth, this volume; Shields, 2005; Jiang et al., 2003). Some of them exhibit characteristic, microcrystalline cap dolostones, and also limestones, which is unique and reflects a climate paradox. Particularly the Marinoan glaciation ca. 635 Ma ago is peculiar, because it provides evidence for low altitude glaciation at equatorial latitudes. Three models have been proposed to explain an increase in...