Folded and warpedThese sedimentary rocks in the southern Australian outback date from the latest Pre

Folded and warpedThese sedimentary rocks in the southern Australian outback date from the latest Precambrian, and were deposited some 540 million years ago in a basin, before being uplifted into a mountain range and eroded into soft hills. The region is known as the Adelaide Rift Complex (or to use an older, now mostly abandoned, vocabulary geosyncline) and flows from the flinders ranges, through the Fleurieu Peninsula (of wine growing terroir fame) southwards to Kangaroo Island.The original sediments were deposited on Australia’s eastern edge as Pangaea’s precursor supercontinent Rodinia broke up between 870 and 500 million years back, and they encompass the first complex multicellular organisms found so far in the fossil record, the enigmatic Ediacaran fauna (see http://on.fb.me/1BlFejb). As the supercontinent rifted huge basins opened that became sediment traps for the products of rivers and glaciers. At their thickest they stretch some 24km deep, and their lithology is of marine sandstones, limestones and shales.At the end of the Cambrian, between 514 and 500 million years ago they were squished and baked in a mountain building event (known as the Delamarian orogeny), and the remaining hills are but the root stumps of a mighty range. The basin inverted into a mountain range in response to some huge tectonic pressure.The area was also crucial in demonstrating the reality of the Snowball Earth events, aka the Marinoan and Sturtian glaciations, in which our whole planet more or less was covered in deep ice. Rocks in the area had striations (scratches) caused by rocks stuck onto the bottom of a glacier grinding across the, and had magnetic signatures indicating that they were close to the equator when this happened.LozImage credit: Digital Globe, field of view around 160 square km. -- source link

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