INVESTIGADORES
TUNIK Maisa Andrea
artículos
Título:
Malargüe Group (Maastrichtian-Danian) deposits in the Neuquén Andes, Argentina: Implications for the onset of the first Atlantic transgression related to Western Gondwana break-up
Autor/es:
AGUIRRE URRETA, MARIA BEATRIZ; TUNIK, MAISA ANDREA; NAIPAUER, MAXIMILIANO; PAZOS, PABLO; OTTONE, G; FANNING, M; RAMOS, V. A.
Revista:
GONDWANA RESEARCH
Editorial:
ELSEVIER SCIENCE BV
Referencias:
Año: 2011 p. 482 - 494
ISSN:
1342-937X
Resumen:
The discovery of marine to brackish and fresh water carbonates in the inner Agro foldand-thrust belt at Pichaihue, Neuquén, Argentina, located to the west of the Andeanorogenic front, imposes important constraints on the paleogeography of the first Atlantictransgression in the Neuquén Basin related to the break-up of Western Gondwana. Theconstraints on the timing and areal extent of these deposits shed light on the early uplifthistory of the southern Andes. These limestones are part of the Maastrichtian-DanianMalargüe Group, which was previously only known from its exposures in the extra-Andean area, representing foreland basin deposits. The presence of stromatolites,oncoids, serpulids, bivalves and gastropods as well as silicified stems of macrophytesindicates a shallow marine, partially brackish environment associated with non-marinedeposits. These strata are interfingered with and overlie distal tuffs and proximalpyroclastic flows, whose geochemical characteristics point to a magmatic arc source.SHRIMP U-Pb dating of volcanic zircons of these tuffs yielded an age of 64.3 ± 0.9 Mathat confirms the correlation to the Maastrichtian-Paleocene marine transgression fromthe Atlantic Ocean. The change in the paleoslope of the basin from Pacific Oceantransgressions to this Atlantic transgression is related to the uplift and deformation of theAgrio fold and thrust belt. The Pichaihue Limestone is unconformably deposited onvolcanic agglomerates which in turn unconformably overlie Early Cretaceous deposits.Based on these data, it is confirmed that the Cretaceous uplift of the Andes was episodicat these latitudes, with a first pulse in the Cenomanian and a second one in pre-Maastrichtian times. The episodic uplift is also related to an eastward migration of thethrust front and the volcanic arc, related to a previously proposed shallowing of thesubduction zone. These episodes were controlled by the Western Gondwana break-up andthe beginning of absolute motion of South America toward the west