Estudio bioestratigráfico integrado del perfil La Horqueta (límite Aptiano-Albiano), lago Cardiel, Patagonia, Argentina

Resumen

Integrated biostratigraphical study of La Horqueta section (Aptian-Albian boundary),
Cardiel lake, Patagonia, Argentina. La Horqueta at Cardiel lake is a classical section in Santa Cruz province
where marine invertebrates include ammonites of the Aptian-Albian transition. New collections at this site
yielded palynological remains from several horizons in both Río Mayer Formation (latest Aptian) and Piedra
Clavada Formation (earliest Albian). Marine dinoflagellate cysts are found in the lower part of the section; they
agree with an Aptian to earliest Albian age suggested by ammonites. Statistical counts of six palynological
groups show the dominance of the conifer family Cheirolepidiaceae in the Río Mayer Formation coinciding with
the presence of dinoflagellate cysts and the gradual increase of pteridophitic spores and saccate pollen, mainly
of the family Podocarpaceae in the upper Piedra Clavada Formation. Angiosperm pollen is present throughout
the section although it is more significant in the upper Piedra Clavada Formation where several new types have
their first appearance (tricolpate, tricolporoidate and other types). Most palynological taxa are found across the
whole section and many are known to occur in other units cropping out in this area, as the Baqueró Group
(Early Aptian) or Kachaike Formation (Mid-Late Albian). Only few selected and probably significant species
have been found to be of a possible biostratigraphic value and their distribution along the section is shown in a
chart.