The Plio-Pleistocen record of the central eastern Pampas, Buenos Aires province Argentina: The Chapadmalal case study

MARCELO ZÁRATE; JORGE FASANO

PALAEOGEOGRAPHY PALAEOCLIMATOLOGY PALAEOECOLOGY

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 1989 vol. 72 p. 27 - 52

0031-0182

The Plio-Pleistocene record of central eastern Pampas, Argentina is preserved in loess-like sediments exposed in the sea cliff south of Amar del Plata. The uplift of the Andes in the Miocene triggered the deposition of wind blown material. The source areas are located about 1000 km, in  western Argentina. Volcanis ashfalls played a significant role in the formation of eolian material, 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 and late Pleistocene in Ensenadan and Lujanian land mammal ages. The Chapadmalal 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 calcretes are very frequent throughout the stratigraphic succession. Several paleosurfaces with prominent paleosols and calcretes suggest that sediemtnation was an episodic process with numerous depositional gaps recording relative long lasting intervals of landscape  stability. The depositional events represent alternation of fluvial and eolian sedimentation. Low frequency catastrophic episodes played a signficant role in the sedimentation process.