Long term evolution of an escarpment in a tableland landscape (Serra Geral de Goiás, Brazil): Insights from in situ-produced cosmogenic nuclides

Abstract

Topographic escarpments are striking geomorphic features shaping the Earth's surface, often forming distinct water divides in tectonically stable regions. This study presents a new analysis of the geomorphic evolution of the Serra Geral Escarpment in the State of Goiás, Central Brazil, using in situ-produced cosmogenic nuclides. The objective is to quantify Quaternary denudation rates associated with different geomorphic compartments of this regional-scale escarpment by measuring the concentrations of ¹⁰Be, ²⁶Al, and ³⁶Cl in river-borne sediments and bedrock outcrops. The results reveal three distinct denudation regimes: the summit surface of the Western Bahia Plateau (7.4 ± 0.2 m Myr⁻¹), the pediplanation surface at the toe of the Serra Geral Escarpment (22.6 ± 0.6 m Myr⁻¹), and the steep escarpment slopes (84.4 ± 3.8 m Myr⁻¹). The significant influence of regolith burial and landslides on isotopic signatures is highlighted, underscoring the importance of accounting for these processes when interpreting cosmogenic nuclide data. Estimated escarpment retreat rates range from 30 to 90 m Myr⁻¹ along active segments, while the southern region shows stabilization indicative of an advanced stage of landscape evolution. These findings demonstrate the complex interplay between geomorphic processes, lithology, and climate in shaping escarpments within continental interiors. Preliminary geomorphic evidence suggests that escarpment retreat and pediplanation at the glint's base may have initiated as early as the upper Miocene. This study establishes a framework for understanding tropical plateau erosion and offers insights into the evolution of similar escarpments worldwide.