Paleogene terrestrial ecosystems related to Patagonian mammal faunas: preliminary reconstructions

BELLOSI E. S. Y J.M. KRAUSE

Buenos Aires

Workshop; Reunion Anual Comunicaciones Asociacion Paleontologica Argentina; 2010

Asociacion Paleontologica Argentina

Paleogene terrestrial ecosystems related to Patagonian mammal faunas: preliminary reconstructionsPaleogene climates and environments of the Patagonian region, inhabited by successive vertebrate faunas, can be reconstructed using sedimentological, paleopedological, ichnological, paleobotanical and invertebrate information, preserved in pyroclastic and siliciclastic continental and shallow-marine sequences (e.g. Río Chico, Laguna del Hunco, RíoPichileufú, La Buitrera, Sarmiento, San Julián, Río Leona). Main characteristics of these terrestrial ecosystems in San Jorge basin are summarized for eight land mammal assemblages/ages in chronological order. Carodnia (Late Paleocene. Peñas Coloradas Formation): Permanent meandering rivers. Mixed subtropical forests. Temperate-warm, humid seasonal conditions. Itaboraian (Late Paleocene-Early Eocene. Las Flores Formation): Broad flood-plains. Subtropical-tropical, highlydiverse, multistratified forests. Abundant megathermic taxa. Warm and humid climate. Riochican (Early-Middle Eocene. Koluel-Kaike Formation): Stable loessic plains, small rivers and ponds. Frequent but discontinuous ashfalls. Similar vegetation. Warm, humid to subhumid seasonal conditions. Vacan (Middle Eocene): Loessic-fluvial plains. Subhumid (scarce information). Barrancan (Middle Eocene. Gran Barranca Member): Dry loessic plains, rolling landscape, swampy ponds. Continuous and intense ashfalls. Widespread palm groves, subordinated tall grasslands. Highland Nothofagus forests. Temperate-warm, subhumid-semiarid slightly seasonal climate. Mustersan (Middle-Late Eocene. Rosado, Lower Puesto Almendra Members): Variable conditions. First, temperate semiarid-arid loessic plains, poorly vegetated. Later, ephemeral braided river plains. Widespread grasslands, subordinated open forests. Temperate-warm, subhumid-humid seasonal conditions. Tinguirirican (Late Eocene-Early Oligocene. Vera Member): Dry unstable loessic plains. Continuous and intense ashfalls. Scarce vegetation, highland micro-mesothermic forests. Temperate-cool(?), semiarid-arid climate.Deseadan (Late Oligocene. Upper Puesto Almendra Member): Fluvial valleys, subordinated ashfalls. Stable landscape, local basalt flows and volcanic explosions. Grasslands and open forests. Increased megathermic taxa. Temperate-warm, subhumid-humid seasonal conditions.