U/Pb ages on detrital zircons in the southern central Andes Neogene foreland (36º-37ºs): constraints on Andean exhumation.

SAGRIPANTI, L.; BOTTESI, G.; NAIPAUER, M.; FOLGUERA, A.; RAMOS, V.A.

JOURNAL OF SOUTH AMERICAN EARTH SCIENCES

PERGAMON-ELSEVIER SCIENCE LTD

Año: 2011 vol. 32 p. 555 - 666

0895-9811

U/Pb dating on detrital zircons was performed in the Pampa de Carrizalito depocenter of the Late Miocene foreland basin associated with the Southern Central Andes orogenic front. This reveals Andean and pre-Andean components in magmatic derived zircons inhomogeneously distributed through the sequence. Andean, Grenville, Pampean, Famatinian and Gondwanic components reveal a complex source distribution from both Andean slopes, Pacific coast and foreland area. These are discussed showing different patterns in the context of the Andean orogenic cycle. Cretaceous and Jurassic components that are partly related to Mesozoic batholiths, developed at the western slope of the Andes at these latitudes, have a very contrasting behavior through the sequence: While Jurassic grains are represented from base to top, Cretaceous ones dilute upwardly. This is explained through the progressive uplift of the Southern Central Andes that could have created a barrier to Cretaceous to Jurassic detritus, while the older ones would have had an alternative source area represented by the Marifil Formation in the foreland area. Finally, a progressive enrichment in pre-Andean components to the top of the sequence is interpreted as related to the breaking of the foreland area and the consequent rapid expansion of the orogenic front at the time of development of a slab shallowing setting in the region following previous proposals.