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Ripple mark geosite

When a wind or water current flows across loose sand, the sand is dragged along the bottom and frequently is piled up to form ripples. Ripple marks usually occur in sand grains (2 to 0.06 mm) though we can see it, in coarse silts and fine gravels too.

Ripples were seen at the beach, along sandy rivers, or in the desert. Ripples are amazing because they are fairly commonly preserved in the sedimentary record of sedimentary rocks and they are quite useful in determining environmental conditions at the time of deposition.

Ripple marks come in two forms, symmetric (wave formed ripples) and asymmetric (current ripples). Wave formed ripple marks often found on beaches, they are created by a two way current, for example the waves on a beach (swash and backwash). This creates ripple marks with pointed crests and rounded troughs, which aren't inclined more to a certain direction. But current ripple marks created by a one way current, for example in the river, or in the desert (windy ripples). This creates ripple marks with still pointed crests and rounded troughs, but which are inclined more strongly in the direction of the current because the longer side of the ripple always faces the upstream direction. For this reason, they can be used as palaeocurrent indicators; in other words, which direction the wind or water was flowing from when the ripple marks were deposited.

Ripple marks in Aras geopark are not rare and we can observe it in every area. But they are best exposed in Marazad hills, 20 Km east of Jolfa city. In this area, the sedimentary rocks of Cretaceous period are folded and inclined sandstone beds outcropped very well, so we can see ripple marks structures broadly on it.