Macrofossil evidence for a rapid and severe Cretaceous–Paleogene mass extinction in Antarctica

Debate continues about the nature of the Cretaceous–Paleogene (K–Pg) mass extinction event. An abrupt crisis triggered by a bolide impact contrasts with ideas of a more gradual extinction involving flood volcanism or climatic changes. Evidence from high latitudes has also been used to suggest that the severity of the extinction decreased from low latitudes towards the poles. Here we present a record of the K–Pg extinction based on extensive assemblages of marine macrofossils (primarily new data from benthic molluscs) from a highly expanded Cretaceous–Paleogene succession: the López de Bertodano Formation of Seymour Island, Antarctica. We show that the extinction was rapid and severe in Antarctica, with no significant biotic decline during the latest Cretaceous, contrary to previous studies. These data are consistent with a catastrophic driver for the extinction, such as bolide impact, rather than a significant contribution from Deccan Traps volcanism during the late Maastrichtian

The Magmatic Rocks Probably Corresponding to the Andean Batholith and the Associated Metamorphic Contact Phenomena

The knowledge about the presence of outcropping plutonic rocks in the Argentine side of the Fuegian Andes is limited exclusively to the references about the dioritic bodies, in a wider sense, of Mount Jeu Jepén (immediately to the ESE of Lake Fagnano), Spion Kop (in the Lucas Bridges Range, on Paso Harberton) hills and Estancia Túnel, to the E of Ushuaia (this intrusive was attributed to the Andean Batholith and it would be comparable or not with those of the Santa Rosa Plutonic Complex).Fil: Acevedo, Rogelio Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentin

Western Sector of the Fuegian Andes Deformed Complex (FADC-WS)

The Mesozoic complex starts here from the simplest chrono-stratigraphic chart, consisting of a thick marine layer of Late Jurassic-Early Cretaceous age, superimposed to Jurassic volcanic and sedimentary rocks and overlain by Late Cretaceous marine sedimentary rocks, the whole sequence folded and metamorphosed. The marine Tertiary, folded as well, is overlying all the aforementioned units. Underlying the whole group there is a possible metamorphic basement. In this sense, several formations have been proposed, what in certain ways make much more complex the matter at the same time that they contribute to build a richer system of order and classification.Fil: Acevedo, Rogelio Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentin

The Estimated Basement of the Fuegian Andes Mesozoic Stratigraphic Series and tThose Rocks Regarded as Pre-Mesozoic in Age

The role of the Serie Porfirítica as basement is known, as a consequence of the regional extension of the quartz porphyries in Patagonia. This would be a restricted concept of the word basement. Besides this aspect, it is of interest to note the leptometamorphic rocks seen on the coastal area of the Parque Nacional Tierra del Fuego (Tierra del Fuego National Park) and neighbouring areas. They could be regarded as the basement of the Mesozoic marine column.Fil: Acevedo, Rogelio Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentin

The taxonomy and palaeobiogeography of small chorate dinoflagellate cysts from the Late Cretaceous to Quaternary of Antarctica

Small chorate dinoflagellate cysts are common in Upper Cretaceous to Quaternary sedimentary successions around the Antarctic margin. Taxonomic confusion surrounding dinoflagellate cysts and acritarchs of similar morphology throughout the southern high palaeolatitudes has hitherto limited investigation of their palaeoecological significance. This study aims to solve the taxonomic problems, and to allow a new assessment of dinoflagellate cyst acmes. A detailed morphological study of new material from the López de Bertodano Formation of Seymour Island, Antarctic Peninsula, is presented. These dinoflagellate cysts are identified as Impletosphaeridium clavusWrenn & Hart 1988 emend. nov. Their gross morphology and their vast abundances in the James Ross Basin are strongly suggestive of dinoflagellate blooms. This scenario implies similarities to modern dinoflagellate cysts from the polar regions