Variation in the ITCZ position controls the evolution of the piedmont landscape of the tropical Andes (Colombia) during the late Quaternary

Autor(es)

Breda, Caio ; Pupim, Fabiano N. ; Cruz, Carolina Barbosa Leite ; Souza, Priscila Emerich ; Monsalve, Gaspar ; Cardona, Agustin ; Sawakuchi, Andre Oliveira ; Parra, Mauricio

• Tipo de documento: Artigo Científico
• Fonte: Geomorphology; v. 462, p. 14-pg., 2024-07-17.

Resumo

The sedimentary record of fluvial systems is known to preserve important archives of the effects of climate change on the landscape over time and space. While temperate and arid (semi-arid) regions are relatively well studied, our understanding of fluvial dynamics in tropical mountainous areas throughout the Quaternary is poorly known. Here, we propose a model of the landscape evolution of the Upper Caqueta<acute accent> River in the Northern Tropical Andes (NTA) over the past 130 ka, based on mapping and optically stimulated luminescence (OSL) dating of the sediments building alluvial fans and fluvial terraces. The OSL ages indicate that the distributary system was active from 130 to 65 ka; from 65 to 31 ka channels carved the deposits, reorganizing the drainage network to a tributary pattern with rivers flowing into incised valleys. Four fluvial terrace levels were mapped in these valleys and OSL ages indicate sediment deposition around 30, 15, 5, and 1 ka. Based on available palaeoenvironmental data, we have interpreted that the shift in the fluvial landscape from distributary to tributary incised system is related to precipitation change in the NTA, driven by the variation in the latitudinal position of the Intertropical Convergence Zone (ITCZ) due to insolation cycles. Our data suggest that the decreased rainfall, caused by the northernmost position of the ITCZ, combined with the expansion of arboreal elements in the Andean Piedmont, favoured alluvial deposition by both the distributary system (Marine Isotopic Stage - MIS 5 and 4) and the tributary (MIS 2 to the present). Our data supports that following an incision phase during MIS 3, the decrease in the amplitude of precession and obliquity signals led to greater stability of the landscape and to the transition of the distributary fluvial pattern in the upper Caqueta<acute accent> River to its present tributary pattern. (AU)

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