Ashua Formation was deposited in Coniacian-Early Santonian time near shore of a shallow sea and in a plethora of continental arid environments. Its main component is fine-grained siliciclastic materialforming lithic and subordinate arkosic graywackes. Limestones are frequent in the lower member, and in the upper one gypsum and halite are present. Based on sedimentary textures and detailed petrographic studies, nine general microfacies were identified: shallow sea, beach, brackisch and mud flats, lagoon, sabkha and playa, deltaic, alluvial, mud flows, dunes at shoreline of an agitated water basin. The present authors suggest that the main source of detritus was pyroclastic deposits. They probably belong to the heavily eroded Lower Cretaceous Matalaque Formation.
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