English: Cap carbonates in the Precambrian of South Australia.

These structurally-tilted, horizontally-laminated dolostones make up a “cap carbonate” unit that immediately overlies sediments of the Marinoan Glaciation, which was one of two or three Snowball Earth glaciations in the Neoproterozoic. Many lines of geologic evidence indicate that these were the most severe ice ages in history - all or almost all of Earth was covered in glacial ice. Each Snowball Earth Glaciation was followed by a super-greenhouse climate. The resulting sedimentary record of these “freeze-fry” events typically consists of glacial tillites and overlying cap carbonates. These units are preserved at many localities on Earth, including the section seen here.

This cap carbonate unit is the Nuccaleena Formation. It conformably overlies Elatina Formation glaciofluvial sediments - reworked tills. The Elatina-Nuccaleena boundary is a sharp break in many places, but appears gradational at this section. The Nuccaleena grades upward into redbeds of the Brachina Formation. At this site, the Nuccaleena Formation is about 5 meters’ worth of dolostone with some barite. South of this area, it is about 15 meters thick. The carbonate was deposited at a time of very hot global climate. Research indicates that the rocks were originally calcitic, with dolomitization occurring during early diagenesis.

Stratigraphy: Nuccaleena Formation, near-lowermost Ediacaran, near the base of the upper Neoproterozoic

Locality: outcrop along Enorama Creek, Brachina Gorge Geologic Trail, Flinders Ranges National Park, South Australia (vicinity of 31° 19.892’ South latitude, 138° 38.001’ East longitude)

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See info. at: en.wikipedia.org/wiki/Cap_carbonate and en.wikipedia.org/wiki/Marinoan_glaciation and

en.wikipedia.org/wiki/Snowball_Earth