Meet the Adelaide Rift ComplexBetween 870 and 500 million years ago as the supercontinent Rodinia wa

Meet the Adelaide Rift ComplexBetween 870 and 500 million years ago as the supercontinent Rodinia was breaking up, a variety of sediments with minor associated volcanics was deposited on the (as it was then) eastern coastal margin of what is now Australia, and as you can see from the photo the original horizontal layers have had an interesting geological time in the intervening years separating the late Proterozoic from the present day. Supercontinents are thought to break up because the huge span of thicker continental crust acts like a blanket on mantle heat, which builds up and eventually rifts it apart in the splitting phase of the Wilson cycle. They then reassemble as they did some 200 million years later to form Pangaea, and are currently splitting apart again in their eternal stately ballet across the surface of the globe.The story starts with a thinning crust that was being stretched by the forces governing the supercontinental separation. As a thousand km long basin arc shaped formed, it filled with layers of marine mud, sand and lime as the vagaries of geology and sea level changed the depositional conditions, ending as the Cambrian Era came to a close.Also known by the slightly archaic term of geosyncline, the contents of this fault bound basin (now turned into limestone, shale and sandstone) were later inverted into a mountain range in an event known as the Delamarian orogeny (514-500 million years ago) accompanied by extensive tilting, folding and faulting. As the layers of crust detached from the basement and stacked atop each other, the heat rose and the deeper layers started to melt, producing a variety of granites that rose and froze in the folded sedimentary crust.Said range has since been extensively eroded and now covers a chunk of what is now the state of South Australia. The last remnants of a long gone mighty range are now called the Mount Lofty and Flinders Ranges. The enigmatic Ediacaran fauna was first discovered in some of these rocks by exploration geologist Reg Sprigg (see http://bit.ly/1CIifKC and http://bit.ly/1BlFejb).Authors have also noted the similarity in these rocks with ones found in western North America and have suggested that they were formerly adjacent to each other in Rodinia. The photo covers roughly 260 square kilometres.LozDear Readers, Most of our posts are not reaching your news feed due to fb’s filtering system. If you wish to enjoy our posts more often, use the following for information on how to go about it: http://tmblr.co/Zyv2Js1VWMUJ0.Image credit: Digital Globehttp://bit.ly/2saDSJthttp://bit.ly/2sKQBPOhttp://bit.ly/1FY6D8B -- source link

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