T250 The Andes from Top to Bottom (Posters)

Wednesday, 18 October 2023
8:00 AM - 5:30 PM
Hall B

USING THERMOCHRONOLOGY TO UNDERSTAND PATTERNS OF STRUCTURAL UPLIFT, TOPOGRAPHIC GROWTH, AND EROSION IN THE NORTHERN ANDES

Paper number: T250-2
Program: Technical Sessions
Time: 8:00 AM – 5:30 PM

Authors

Abstract

Due to its position in the low latitudes, patterns of uplift, chemical weathering and erosion in the northern Andes may provide an important contribution towards late Miocene-Pliocene cooling.To better understand the elevation and erosion history of the northern Andes, we compiled data from 20 papers, focusing on Apatite (U-Th)/He (AHe), Apatite Fission Track (AFT), Zircon (U-Th)/He (ZHe), and Zircon Fission Track (ZFT) systems. The data were binned in increments of 3 Ma (AHe, AFT) to 10 Ma (ZFT) and plotted using ArcGIS, to highlight the spatial distribution of the thermochronometers and their relationship to topography. Plotting the data on 6 across-strike transects of age vs distance highlight locations where different chronometers overlap or separate into discrete dates.

Ages in southern Colombia transect are the youngest across the northern Andes with AFT ages that range from 0.8 to 3 Ma across the Eastern Cordillera (EC) and ZFT ages that range from 6-13 Ma. On the western edge of the EC, AHe ages cluster around ~10 Ma while AFT ages decrease to 15-40 Ma. To the north, the age of exhumation recorded by AFT increases (~ 5-10 Ma) and the magnitude of exhumation decreases with ZHe ages that range from reset (~ 11-15 Ma) to potentially detrital ages >70 Ma. Like southern Colombia, ages on average get older moving east to west. ~4-11 Ma AHe ages, and ~ 30-60 Ma AFT ages in the central and Western Cordilleras (WC) of Colombia highlight that the generation of topography here is young with limited exhumation.

In Ecuador, AFT ages in the Subandean zone are 4-8 Ma. 20 km west, exhumation in the EC is recorded by ~ 2-10 Ma AHe ages and ~ 10 Ma AFT ages. Between these two regions of active exhumation, AFT ages increase to 20-57 Ma, and are co-located with 33-48 Ma ZFT ages. In the WC, young AHe (3.8-12.5 Ma) and AFT (10-21.7 Ma) ages highlight young exhumation here.

Recent WC exhumation recorded by AFT and AHe in Ecuador but only AHe in Colombia require higher exhumation magnitudes over a potentially longer time in western Ecuador. Conversely, 6-13 Ma ZFT ages in the EC of Colombia emphasize ongoing uplift and exhumation since ~ 13 Ma that is markedly greater than the EC of Ecuador. This dataset combined with thermokinematic models of deformation, elevation and erosion will elucidate the timing and processes contribute to the topography and weatherability in the Northern Andes.

Geological Society of America Abstracts with Programs. Vol. 55, No. 6

doi: 10.1130/abs/2023AM-394769

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