New fossil record of Lactoridaceae in the Paleogene of southern Patagonia (South America).

Resumen

Abstract: The new register of the family Lactoridaceae (Rosannia manika Srivastava) in Tierra del Fuego, Austral basin correspond to  a sedimentary succession located at the south of the Irigoyen River, nearby the Cerro Malvinera  To calibrate the age of this outcrop was analized the palynology (principally dinoflagellates cysts) of different Paleogene formations (La Barca, Punta Torcida and Puesto José) in the Austral basin. This result was compared with large datasets of organic dinoflagellate cyst (dinocyst) assemblages from Southern Pacific Ocean shelf sediments and other sections of the world. The majority of palynomorph taxa from the Cerro Malvinera succession are present in the upper member LB2 of the La Barca Formation and both shared the presence of Lactoridaceae (Rosannia manika Srivastava) and the age-diagnostic dinocysts Pentadinium laticinctum (First Occurrences 51.95) and Batiacasphaera  micropapillata. These dinocysts, which are also recorded in the lower part (Early Eocene) of the Agua Fresca Formation, Chile, indicate an age not older than early Eocene for the LB2 member of theLa Barca Formation and the Cerro Malvinera strata.

This data expands the known fossil range of the Lactoridaceae in Patagonia and contributes to elucidate the probably migration routes of this family. A migration via Antarctica is postulated in this paper  due to the record of this family in the Maastrichtian (López de Bertodano Formation). Depending on new records  due to the presence of this family in the  Colorado Basin in the Danian,  a migration route from the north of Patagonia to the south (Austral basin) it is not descarded.