Palynofacies associated to hyperpycnite deposits of the Miocene, Cabo Viamonte Beds, Austral Basin, Argentina

QUATTROCCHIO, M.E.; OLIVERA, D.; MARTÍNEZ, M.A.; PONCE, J.J; CARMONA, N.

FACIES

SPRINGER

Lugar: Berlin; Año: 2018

0172-9179

The Miocene deposits in the Punta Basílica locality, southernmostArgentina, are included within the Cabo Viamonte Beds, Cabo DomingoGroup, in the Austral foreland basin of Tierra del Fuego province. Theprograding clinoform systems were accumulated during a weakcompressional tectonic regime that allowed the development of a narrowshelf. Paleoenvironmental reconstructions suggest that these clinoformscomprise two dominant architectural elements, channelleveeand lobe complexes, formed mainly by density hyperpycnal currents in outer shelf to depositional slope environments. The transitional and recurrent (vertical and lateral) alternation between sedimentary structures without rheologic boundaries associated with the cooccurrenceof plant remains (Nothofagus) are diagnostic criteria for the recognition of hyperpycnites. This type of density flow typically transports large volumes of sediment and organic matter from proximal to deepmarinesettings. Four palynofacies types were recognized in a cluster analysis. In general, the palynofacies show predominance of spores and pollen grains, tissues, cuticles, and spongy to fibrous amorphous organic matter (plant and/or freshwater to brackish algae derived), which reflect different positions within the depositional system (e.g., leveechanneland lobe deposits). The cooccurrence of inshore (Batiacasphaera spp., Lingulodinium sp.) with relatively more oceanic (Operculodinium centrocarpum, Spiniferites spp.)dinoflagellates is a strong indication that shallowwater assemblages have been displaced into deepwatersettings. Due to the presence of Lingulodinium hemicystum (first appearance data: 23.0 Ma.) and Pentadinium laticinctum (last appearance data: 11.6 Ma.) an age not older than Miocene and not younger than the Serravallian/Tortorian boundary for the Punta Basílica section is proposed.