Środowisko sedymentacji i domniemane Źródło materiału detrytycznego w górnokredowej formacji red-bed Ashua (Peru)
Abstract
Depositional environment and probable source of detritus in the Upper Cretaceous red-bed Ashua Formation (Peru).
A b s t r a c t. 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 material forming 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 mudflats, 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
A b s t r a c t. 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 material forming 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 mudflats, 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