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Iri Flysh geosite

In the Aras geopark, there are sedimentation of flysch deposits in two different periods, one in Cretaceous and the other in Eocene. These two sedimentary units have extended vastly in the geopark area especially in Iri, Dastgerd, Holaq and Arsi villages. The main difference between these two, is that the Cretaceous flysch is intensely folded, but Eocene flysch show a smooth outcrop and has folded gently.

Flysch deposits consist of regular paired beds of sandstone and shale. Sand grains rarely reach to deep parts of marine basin and due to its weight usually deposit in coastal environment. Whenever lands are quickly eroding and rivers sediments load is significantly increasing, the grains flows due to gravity and deposits in deep parts and forms a flysch facies. The sandstone beds are indicating the influx of sand-rich streams into the deep part of the marine basin and the shale beds represent relative quietness when they were depositing. The flysch facies usually represents deposition of sediments in a deep marine (more than 200 m) environment in the conditions in which influx of clastic particles with sizes of mud to sand into the basin is much more than the formation and deposition of limy sediments.

In flysch facies, given to entering enormous amounts of clastic sediments into the basin, ichnofossils are frequent, and by contrast fossil fragment can rarely be found. Ichnofossils or trace fossils are the marks of biological activities which remained in sea floor muds and buried by sandstone deposits. These marks frequently recorded as casts in the sole of the sandstone sedimentary beds. In addition to ichnofossils, in these beds it can be enormously seen various sedimentary structures like ripple marks, tool marks and load casts.