Abstract
Changes in Earth’s surface elevation can be linked to the geodynamic processes that drive surface uplift, which in turn modulate regional climate patterns. We document hydrogen isotopic compositions of hydrated volcanic glasses and modern stream waters to determine late Cenozoic surface uplift across the Peruvian central Andes. Modern water isotopic compositions reproduce mean catchment elevations to a precision better than ±500 m (1σ). Glass isotopic data show a spatiotemporally variable transition from isotopically heavy to isotopically light compositions. The latter are consistent with modern water on the plateau. When interpreted in the context of published paleoelevation estimates and independent geological information, the isotopic data indicate that elevation rapidly increased by 2–2.5 km from 20–17 Ma in the central Western Cordillera, and from 15–10 Ma in the southern Western Cordillera and Altiplano; these patterns are consistent with foundering of mantle lithosphere via Rayleigh-Taylor instability. The Eastern Cordillera was slowly elevated 1.5–2 km between 25 and 10 Ma, a rate consistent with crustal shortening as the dominant driver of surface uplift. The Ayacucho region attained modern elevation by ~22 Ma. The timing of orographic development across southern Peru is consistent with the early Miocene onset and middle Miocene intensification of hyperarid conditions along the central Andean Pacific coast.
Highlights
Development of the 4–6 km-high topography in the central Andes took place in the Cenozoic due to ongoing east-directed subduction of oceanic lithosphere[1]
Incremental removal by ablative subduction[15], thermal weakening[16], or simple shear underthrusting of lower crust and mantle lithosphere[17], predicts lower (
We present stable isotopic data from 376 modern stream water samples (179 new, 197 published42), and 136 volcanic glass samples (117 new samples, 19 published12) to determine surface uplift patterns across the central Andes of southern Peru (Fig. 1A)
Summary
Development of the 4–6 km-high topography in the central Andes took place in the Cenozoic due to ongoing east-directed subduction of oceanic lithosphere[1]. Methods applied to the central Andes have been based on timing of crustal shortening[16], or on geomorphic features such as regional tilt and monocline development[20,21], paleosurface peneplain mapping[22], and river incision[23] Biological proxies, such as phylogenetics of high-elevation biotaxa[24] and leaf physiognomy[25], have been used to infer surface uplift of the central Andes. More recently developed paleoelevation proxies exploit the stable isotopic record by measuring δ18O in soil carbonates[9], mean annual air temperatures inferred from clumped isotope Δ47 variations in carbonate[26], and paleoenvironmental waters preserved in hydrated volcanic glass[27,28,29]. During the traverse across high topography, moisture undergoes subcloud evaporation and recycling effects resulting in an inland gradient to heavier isotopic compositions[42]
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