Stratigraphy, palynology and conchostracans of an Early Cretaceous sequence at Cañadón Calcáreo locality, extraandean central Patagonia: Age and palaeoenvironmental significance

VOLKHEIMER, WOLFGANG; GALLEGO, OSCAR F.; CABALERI, NORA G.; ARMELLA, CLAUDIA; NARVAEZ, PAULA; SILVA NIETO, DIEGO GONZALO; PAEZ, MANUEL A.

CRETACEOUS RESEARCH (PRINT)

Elsevier

Lugar: Amsterdan; Año: 2007

0195-6671

The first palynologic record in an Early Cretaceous sequence at the  Cañadón Calcáreo locality of extraandean central Patagonia is presented. It contributes a more precise chronology and palaeoenvironmental characterization of the sequence. The conchostracofauna records support the palynologic results. Sedimentary environments are studied in relation to a tectogenetic development model. Detailed measurement of stratigraphic/sedimentologic sections in the field was complemented by sampling for palynology, conchostracans and sedimentary facies/microfacies analysis. The depositional environment is lacustrine/palustrine in the lower part, grading to fluvial. The middle and upper sections of the unit are fluvial and characterized by prevailing sandstones, conglomerates and tuffs. Dominant genera of the palynoflora  are Classopollis and Callialasporites, with an incipient presence of Cyclusphaera. The prevalence of the thermophilous genus Classopollis indicates warm climatic conditions, and the high frequency and diversity of trilete spores, corresponding to a hygrophile vegetation of ferns and bryophytes, indicates locally humid conditions. The fauna of conchostracans identified is composed by species of the genera Nemestheria (Zhestheria), Pseudestherites, Euestheria?, and probably Congestheriella. A Valanginian age is inferred for the middle part of the sequence.