Dwyka DiamictiteDuring the Permian, the last period of the Paleozoic Era, much of southern Gondwanal

Dwyka DiamictiteDuring the Permian, the last period of the Paleozoic Era, much of southern Gondwanaland was near the planet’s south pole. After the evolution of land plants and forests, carbon dioxide was pulled out of the atmosphere rapidly and locked into rocks such as coal, a process that defines the typical rocks from the “Carboniferous” period. As a consequence of this drawdown in carbon dioxide, the planet was cooled, leading to formation of glaciers at the poles and locking the planet into an “icehouse” state.This rock, today found in the nation of South Africa, formed from those glaciers. A “Diamictite”, by definition, is defined by having two distinct grain sizes (the Di prefix). Glacial till, the piles of rocks pushed to the end of glaciers, are typically completely unsorted, although sometimes people will apply the term “diamictite” to any type of glacial deposit.A classic diamictite forms in a marine environment, where glaciers are interacting with a lake or the ocean. As ice breaks off of the glacier, it carries some larger clasts with it and drops those clasts into the larger body of water. The sedimentary deposit produced by this interaction will be large, unsorted clasts of nearby rocks surrounded by the fine-grained sediments that were otherwise being deposited in that body of water.How many different types of clasts can you spot?-JBBImage credit: Brian Romanshttps://flic.kr/p/4GnykqRead more:http://bit.ly/1QDbcNF -- source link
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