Mississippian–Early Permian brachiopods from western Argentina: Tools for middle- to high-latitude correlation, paleobiogeographic and paleoclimatic reconstruction

TABOADA, ARTURO CÉSAR

PALAEOGEOGRAPHY PALAEOCLIMATOLOGY PALAEOECOLOGY

ELSEVIER SCIENCE BV

Lugar: Amsterdan; Año: 2010 p. 152 - 173

0031-0182

Brachiopod faunas from western Argentina are reviewed to improve the current understanding of theirbiostratigraphic and paleobiogeographic value for intercontinental correlation and paleoclimatic reconstruction,especially for middle to high paleolatitudes. The oldest faunal assemblage, the late Tournaisian–early ViséanMalimanian fauna, indicates an incipient biogeographic segregation of southwestern South America fromcontemporaneous peri-Gondwana and northern hemisphere regions, likely due to the enhanced thermalgradient that predated the pronounced latest Viséan global cooling and the major latitudinal bioticdifferentiation on a global scale. Paleogeographical distribution of key brachiopod taxa provides evidence offaunal interchange along western Gondwana during late Early Carboniferous. The paleoclimate of the region bythis time has been interpreted as temperate preglacial conditions, in a higher paleolatitudinal setting. Globalcooling and strong differentiation between marine biota of circum-polar and paleoequatorial regions occurredafter late Viséan. The Barrealian fauna (Rugosochonetes-Bulahdelia and Levipustula assemblages), represents theoldest faunal record in western Argentina of this major latitude-related biotic segregation linked with the onsetof the mid-Carboniferous glaciation. The Barrealian fauna appeared during a major late Viséan–Serpukhovianglacial episode with short-lived glacial and interglacial stages. Climatic fluctuations were probably related tolocal faunal changes and marine biotic exchange between higher and middle paleolatitudes of southwesternand eastern Gondwana. Widespread postglacial deposits bearing Bashkirian faunas demonstrate the beginningof a progressive climatic amelioration trend until early Permian times, barely affected by short-lived colderpaleoclimatic fluctuations. The incoming of the late Bashkirian–early Moscovian Marginovatia-Maemia faunawas linked to a climatic change in the region following the disappearance of glacial conditions in westernmostArgentina. Ocean currents from the north, that reached the region bringing boreal brachiopods, were warmenough since Bashkirian times to build a thermal barrier for the biotic interchange with peri-Gondwana regionsunder subpolar settings and a faunal disconnection was established. In addition, asymmetrical climatic recordbetween western Argentina and regions still under strong glacial influence, such as Patagonia and easternAustralia, reflect the clockwise rotation of Gondwana and consequent migration of western Argentina to lowerlatitudes. After a preceding mainly regressive depositional interval, the marine incursion bearing the Tivertonia-Streptorhynchus fauna accompanied the most extensive transgression that covered western Argentina. It wasprobably linked with the beginning of a thalassocratic regime by the global major sea level rise of late Asselian–Sakmarian times. The Tivertonia-Streptorhynchus assemblage represents a middle paleolatitude temperate andmixed fauna, which migrated toward southern Gondwana regions, indicating a marine faunal connectionduring a climatic amelioration trend. The last marine incursion in western Argentina brought the Costatumulusfauna, linked to a brief interruption of the mostly temperate paleoclimatic conditions established since thePennsylvanian. A short-lived minor glacial pulse associated with the Costatumulus fauna reflected localmitigated climatic fluctuations, by the paleolatitudinal gradient to circumpolar areas where a major glacialpulse occurred during Sakmarian–Artinskian times.