Neogene paleoelevation of intermontane basins in a narrow, compressional mountain range, southern Central Andes of Argentina.

G.D. HOKE, L.B. GIAMBIAGI, C.N. GARZIONE, J.B. MAHONEY, M.R. STRECKER

EARTH AND PLANETARY SCIENCE LETTERS

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2014 vol. 406 p. 153 - 164

0012-821X

The topographic growth of mountain ranges at convergent margins results from the complex interaction between the motion of lithospheric plates, crustal shortening, vertical uplift and exhumation. Constraints on the timing and magnitude of elevation change can provide insight into how these processes interact over different timescales to create topography. Sedimentary sequences, their potential isotopic archives, and fossil content preserved in intermontane or foreland basins constitute excellent data to assess the regional history of uplift, to decipher the impact of topography on atmospheric circulation and superposed exhumation. The semi-arid to to arid southern Central Andes of western Argentina between 30°S and 35°S host a set of intermontane sedimentary basins with considerable temporal overlap that occupy different topographic positions in the orogen. This study uses stable isotope data from pedogenic carbonates collected from seven different stratigraphic sections to examine the middle to late Miocene history of elevation change in the central Andes thrust belt, which is located immediately to the south of the Altiplano-Puna Plateau, the world?s second largest orogenic plateau. Paleoelevations are calculated using previously published local isotope-elevation gradients observed in modern rainfall and carbonate-formation temperatures determined from clumped isotope studies in modern soils. Calculated Miocene basin paleoelevations are between 1.2 km and 2.0 km for basins that today are located between 1500 and 3400 m elevation. Considering the modern elevation and precipitation d18O values of the sampling sites, three of the intermontane basins experienced significant surface uplift between the end of deposition during the late Miocene and present. Importantly, the timing of elevation change cannot be linked to any documented major episodes of crustal shortening; instead the spatial pattern of uplift is opposite that of crustal thickness. The spatial pattern of surface uplift is best explained by eastward migration of a crustal root via ductile deformation in the lower crust and is not related to flat-slab subduction.