Miocene Marine Transgressions: Paleoenvironments and Paleobiodiversity

SCASSO, ROBERTO A.; CUITIÑO, JOSÉ I.

© Springer International Publishing AG 2017 P. Bouza and A. Bilmes (eds.), Late Cenozoic of Península Valdés, Patagonia, Argentina, Springer Earth System Sciences, DOI 10.1007/978-3-319-48508-9_3

Springer International Publishing

Año: 2017; p. 47 - 84

Abstract Two major marine transgressions covered part of Patagonia during theMiocene and both are recorded in the Península Valdés region. The older (earlyMiocene) is represented by the volumetrically scarce outcrops of the GaimanFormation, composed by shelf mudstones and fine sandstones. The late Miocenetransgression is represented by the Puerto Madryn Formation, widely distributed inPenínsula Valdés and composed of mudstones, sandstones and shell beds, being thefocus of this work. Sediments of this unit were deposited in inner shelf, nearshore,tidal channel and tidal flat environments. Fossil content is abundant and diverse,including palynomorphs, foraminifers, marine invertebrates (dominated by molluscs),cetaceans, pinnipeds, marine fishes and birds, as well as continental mammals, birds, and fishes. Isotopic and biostratigraphical data suggest a late Mioceneage for the Puerto Madryn Formation, although some middle Miocene biostratigraphicalindicators are present. Paleoenvironmental information suggests oceanicand continental temperatures warmer than present day, evidenced by the Caribbeanmolluscan association and the continental vertebrate and palinological associations,respectively. Instead, cetaceans, dinoflagellates, and some marine fishes, suggestcolder oceanic temperatures. Precipitations were also higher than present, evidencedby the presence of freshwater mammals, birds, fishes, and plants. This workhighlighted some gaps in the geological and paleontological knowledge includinggeochronology, stratigraphic control of paleontological studies and the knowledgeof poorly known fossil groups, which should be the focus of future investigations.