Pliocene pedosedimentary cycles in the southern Pampas, Argentina

KEMP ROB; MARCELO ZÁRATE

SEDIMENTOLOGY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2000 vol. 47 p. 3 - 14

0037-0746

The Plio-Pleistocene record of central eastern Pampas, Argentina, is preserved in Ioess-like sediment exposed in the sea cliffs south of Mar del Plata. The uplift of the Andes during Miocene-triggered the deposition of wind-blown material. The source areas are located about 1000 km away, in western Argentina. Volcanic ash falls play a significant role in the formation of aeolian sediments. Which were reworked and redeposited by aqueous transport in a flat, low relief landscape under varying climatic conditions. Vertebrate fossil assemblages document warm and wetter Pliocene and Early Pleistocene climates during Montehermosan and Uquian land-mammal ages. More arid and cooler conditions alternating with humid and warmer intervals prevailed during the Middle to Late Pleistocene in Ensenadan and Lujanian land-mammal ages. The Chapadmal locality is the best exposed and most complete section. Almost all the units have been modified by pedogenesis. Truncated paleosols as well as pedogenic and non-pedogenic calcrete are very frequent throughout the estratigraphic succession. Several paleosurfaces with prominent paleosols and calcretes suggest that sedimentation was an episodic process with numerous depositional gaps, recording relatively long lasting intervals of landscape stability. The depositional events represent alternations of fluvial and aeolian sedimentation. Low frequency catastrophic episodes played an important role in the sedimentation process.