During the most intense stage of the Alpide orogeny in the Pyrenees (Middle Eocene), marlstones were affected by dramatic deformations which folded and broke their strata. Through fractures, some fluids flowed depositing calcite.
At the beginning of the Middle Eocene, the western end of Sobrarbe was the transition area between the continental domain, eastwards, and the marine domain, westwards. Huge quantities of sediments were deposited in this area and later transported into the deep sea.
During heavy rainfalls, storms or blizzards, hyper-concentrated flows were formed, transporting massif quantities of sediments to the bottom of the sea with enough energy to dramatically erode the substratum.
At the bottom of the Eocene sea, sand layers were turned over by currents which left a mark of their activity as a succession of tracks known as ripples.
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