Folded flysch When continents start their slow grinding collisions a typical sequence of rocks resul

Folded flyschWhen continents start their slow grinding collisions a typical sequence of rocks results, named after the German word for ‘to flow’ by a Swiss geologist in 1827. The original sequence came from the forelands of the Alps, where interbedded limestones, sandstones and shales marked the remnants of the earliest days of the mountain chain. As the continents approach each other and the crust begins to thicken, the increased weight causes the crust to bend in a process called lithospheric flexure into a deep ocean basin. The downwarp creates a perfect trap for the new sediment being eroded from the growing topography of the developing mountain front as the orogenic event builds. Flysh forms in deep marine environments, in low energy sedimentological surroundings (as opposed to the high energy one of the seashore)These rocks have been found in mountains across the entire Spine of the World (see http://bit.ly/1oYxD67), a testament to the closing of the old ocean Tethys as India and Africa collided with Eurasia. In Europe they run from the Pyrenees, through the Alps and Carpathians and into the Balkans. In the northern Alps it is a named a stratigraphic unit, the only one allowed it as a generic name (a bit like puddingstone, see http://bit.ly/1Kd83hN for an unusual tale of geological nomenclature). These were snapped in Afghanistan, and record some of the tremendous forces created by continental collision after the flysh was deposited.LozImage credit: http://imaggeo.egu.eu/http://gsabulletin.gsapubs.org/content/58/11/979 -- source link

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