Paleogene Climatic and Biotic Events in the Terrestrial Record of the Antarctic Peninsula: An Overview

REGUERO, M; MARENSSI, S

The Paleontology of Gran Barranca: Evolution and Environmental Change through the Middle Cenozoic of Patagonia

Cambridge University Press

Lugar: Cambridge; Año: 2010; p. 383 - 397

The James Ross Basin in Antarctic Peninsula contains a terrestrial Eocenefauna that predates the establishment of the permanent ice sheets at the Eocene-Oligocene boundary in Antarctica. Mammalian fossil specimens are available fromthree stratigraphically controlled localities throughout this sequence.The Seymour Island La Meseta Fauna (La Meseta Alloformation, Cucullaea IAllomember, middle Eocene) contains at least twelve mammal taxa, predominantlytiny marsupials (mostly endemic and new taxa). The endemism of the marsupialssuggests the existence of some form of isolating barrier (climatic and/or geographic)since the early Eocene. Faunal similarity between the La Meseta Fauna and the Pasodel Sapo fauna assigned to the Vacan (?late Paleocene - ?early Eocene) of Patagoniastrongly suggests that the former is more derived from the latter. The occurrence onSeymour Island of the sudamericid Sudamerica ameghinoi, that had become extinct inSouth America in the Paleocene, also indicates that isolation may have allowedextended survival of this Gondwanan group in the Eocene of Antarctica and thefactors that caused their extirpation in South America did not affect Antarctica. Thefaunal evidence indicates that the La Meseta mammalian fauna was derived from latePaleocene/early Eocene Riochican/Vacan faunas. The dispersal and vicariance eventsmay have occurred during the onset of the late Paleocene-early Eocene climaticoptimum between 58.5 and 56.5 Ma, when major regressive events are recorded eitherin the northern Antarctic Peninsula and southernmost Patagonia. The absence ofnotoungulates in the La Meseta fauna is noteworthy. We speculate that thenotoungulates could have passed into Antarctica during the latest part of the Paleoceneor early Eocene when the environmental conditions were warmer, and then becameextinct at the onset of the climatic deterioration during the early Eocene.