File:Clast-rich mixtite (Coleman Member, Gowganda Formation, Paleoproterozoic, ~2.3 Ga; Percival Lake roadcut, Ontario, Canada) 5 (40760525673).jpg
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Mixtite in the Precambrian of Ontario, Canada. This outcrop includes glacial conglomerates and massive, thick-bedded, clast-poor mixtite. "Mixtite" here supposedly refers to a subglacial melt-out till - a type of tillite or diamictite. More generally, "mixtite" appears to be a synonym of "tillite" (?). These glacial deposits are part of the famous Gowganda Formation, a ~2.3 billion year old deposit in Ontario, Canada representing a very ancient Ice Age. Other glacially-deposited sedimentary rocks of Paleoproterozoic age have been reported from Wyoming, Finland, India, southern Africa, and Australia. The glaciation was likely a widespread event, and may have persisted for a long time. This ice age is hypothesized to have been triggered by decreasing levels of methane gas (CH4) in the atmosphere as oxygen gas (O2) levels increased (the methane oxidized to carbon dioxide). This lessened the effects of greenhouse warming, and resulted in climate cooling. Stratigraphy: Coleman Member, Gowganda Formation, lower Cobalt Group, Huronian Supergroup, Paleoproterozoic, ~2.3 Ga Locality: Percival Lake outcrop - roadcut on the eastern side of Route 144, opposite Percival Lake, north-northwest of the town of Cartier, Ontario, southeastern Canada (46° 45’ 47.38" North latitude, 81° 35’ 50.64" West longitude) (= stop 35 of Rousell et al. (2009) - A field guide to the geology of Sudbury, Ontario. Ontario Geological Survey Open File Report 6243, p. 165.) |
| Date | |
| Source | Clast-rich mixtite (Coleman Member, Gowganda Formation, Paleoproterozoic, ~2.3 Ga; Percival Lake roadcut, Ontario, Canada) 5 |
| 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@N05/40760525673 (archive). It was reviewed on 22 October 2019 by FlickreviewR 2 and was confirmed to be licensed under the terms of the cc-by-2.0. |
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| current | 06:05, 22 October 2019 | | 4,000 × 3,000 (8.79 MB) | Rudolphous (talk | contribs) | Transferred from Flickr via #flickr2commons |
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