Paleoenvironmental Interpretation of the late Miocene Deposits, from El cajón Valley (Catamarca Province, Argentina) Based on calcareous microfossils

MORTON LOURDES SUSANA; ZAMUDIO MARÍA BELÉN

Advances in South American Micropaleontology Selected Papers of the 11th Argentine Paleontological Congress

Springer Earth System Sciences

Año: 2019; p. 115 - 129

The Neogene sedimentary sequence from El Cajón Valley, Catamarca Province, Argentina, includes alloformations or sequences of three orders: Peñas Azules, Totoral, and Playa del Zorro, being this last one the one studied in this work. The samples come from the Río Totoral site, located in the southern portion of the valley. The calcareous microfossils associations, together with gastropods and bivalves, were found in levels of green and yellow-green fine sandstones and mudstones, with gypsum intercalations. The microfossils are represented by foraminifers of the genus Ammonia, together with Ostracoda, Cytherocopina, from which were recognized Cyprideis sp. Perissocytheridea sp., Limnocythere sp.1, and Limnocythere sp. 2. Foraminifers were found only at one level, where they constitute the 15% of the total specimens. The ostracods were dominant in all the associations, and they were represented by valves and carapaces of juveniles and adults. In many cases, they showed signs of compression and fragmentation. Cyprideis and Perissocytheridea were common in the lower levels of the outcrop; they are known as typical from brackish water. At the middle section level, the association was characterized by the dominant taxa of Cyprideis and Limnocythere. This association could indicate brackish waters with precipitations higher than evaporation and high alkalinity. At the upper section level, a low foraminifera diversity is represented only by Ammonia in association with Cyprideis. This fact would denote a shallow lacustrine and oligo?mesohaline paleoenvironment.