Palynology and facies of the Late Triassic of Comallo (Northern Patagonia, Argentina)

ZAVATTIERI, A.M., VOLKHEIMER, W. & ROSENFELD, U.

Zentralblatt für Geologie und Paläontologie, Teil I, Geologie

Schweizerbart science publishers

Lugar: Stuttgart; Año: 1994 vol. I p. 133 - 154

0340-5109

In the region of Comallo, Rio Negro Province, Argentina, continental Late Triassic clastic sediments have been deposited unconformably on the metamorphic basement of the North Patagonian Massif. These sediments generally form characteristic fining upward sequences indicating a braided river system in the lower and hanging parts of the succession,meandering river system in the middle part. In the latter the top layers of the sequences partly bear thin (cm-dm) autochthonous lignite seams. From 10 stratigraphic levels 3 types of microfloristic assemblages were distinguished which characterize different sedimentary environments. Prevailing Polypodiacean ferns or Osmundaceans resp. characterize two different swamp environments, bisaccate grains and Araucarian type pollen higher topographic levels. A Late Triassic age of the microflora is indicated by the simultaneous occurrence of typical Triassic taxa like Guthoerlisporites cancellosus and first representatives of the genus Classopollis, which does not appear before the Norian in the Gondwanide floral province. The investigated flora represents an Ipswich type and indicates temperate climatic conditions. The great amount of trilete spores in nearly all assemblages locally points to a moist environment.