File:Cryogenian-Ediacaran boundary (basal Nuccaleena Formation, Neoproterozoic; Enorama Creek section, Flinders Ranges, South Australia) 17.jpg
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English: This is a "GSSP", a global stratotype section and point. Stratigraphers have been establishing these for important boundaries on the geologic time scale for many years now. This particular GSSP is in the Flinders Ranges of South Australia - it defines the boundary between the last two systems of the Precambrian, the Cryogenian (below) and the Ediacaran (above).
The reddish rocks in the lower part of the photo are sandstones in the basal Nuccaleena Formation, which overlie dark reddish glacial tillites of the Elatina Formation (out of frame here). The tillites were deposited during the Marinoan Glaciation, which was one of two or three Snowball Earth glaciations in the Neoproterozoic - all or almost all of Earth was covered in ice. Each Snowball Earth glaciation was followed by a super-greenhouse climate, which resulted in the deposition of "cap carbonates" (= buff-colored dolostones at the very top of the photo). The drillholes were done by Yale University for paleomagnetic analysis. The GSSP marker, called a "golden spike", was placed at the wrong bedding plane. The actual GSSP is a parting just above the top of the GSSP plate - this mistake resulted in a meaningless golden spike. Another meaningless GSSP is the Precambrian-Cambrian boundary in Newfoundland, which is supposedly defined by the first appearance of complex trace fossils, exemplified by Treptichnus pedum. That trace fossil has since been found below the golden spike erected at that section. Yet another meaningless GSSP is the Cambrian-Ordovician boundary, which was established in a section with reversed biostratigraphy, due to the presence of sediments redeposited downslope from the shelf edge. The lesson? Science is not done, and will never be done, by dictatorial decree. Stratigraphy: Ediacaran-Cryogenian boundary in the basal Nuccaleena Formation, middle-upper Neoproterozoic boundary Locality: outcrop along Enorama Creek, Brachina Gorge Geologic Trail, Flinders Ranges National Park, South Australia (31° 19.892’ South latitude, 138° 38.001’ East longitude) See info. at: en.wikipedia.org/wiki/Cap_carbonate and en.wikipedia.org/wiki/Marinoan_glaciation and en.wikipedia.org/wiki/Snowball_Earth |
| Date | |
| Source | https://www.flickr.com/photos/47445767@N05/50847134166/ |
| Author | James St. John |
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This image was originally posted to Flickr by James St. John at https://flickr.com/photos/47445767@N05/50847134166. It was reviewed on 18 January 2021 by FlickreviewR 2 and was confirmed to be licensed under the terms of the cc-by-2.0. |
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| current | 03:06, 18 January 2021 | | 3,008 × 2,000 (6.01 MB) | Ser Amantio di Nicolao (talk | contribs) | Uploaded a work by James St. John from https://www.flickr.com/photos/47445767@N05/50847134166/ with UploadWizard |
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