Abstract

QUATTROCCHIO, Mirta Elena. New fossil record of Lactoridaceae in the Paleogene of southern Patagonia (South America). Rev. Mus. Argent. Cienc. Nat. [online]. 2017, vol.19, n.1, pp.71-84. ISSN 1853-0400.

The new record of the family Lactoridaceae (Rosannia manika Srivastava) in Tierra del Fuego, Austral Basin corresponds to a sedimentary succession located at the south of the Irigoyen River, nearby the Cerro Malvinera. The palynology (principally dinoflagellates cysts) of different Paleogene formations (La Barca, Punta Torcida and Puesto José) in the Austral Basin was analyzed to calibrate the age of this outcrop. 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 the 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 Ma). An age not older than early Eocene is proposed for the LB2 member of the La 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 discarded.

Keywords : Lactoridaceae; Paleogene; Southern Patagonia; South America.