Cenozoic sediment bypass versus Laramide exhumation and erosion of the Eagle Ford Group: Perspective from modelling of organic and inorganic proxy data (Maverick Basin, Texas, USA)

Abstract

Abstract The Cenozoic unconformity above the Late Cretaceous carbonates within the Maverick Basin is a unique feature of Texas (USA). Hypotheses accounting for the unconformity include (1) Cenozoic sediment bypass, and (2) ~6400 m of erosion during the Laramide orogeny. Both hypotheses have different implications for the burial history of the Eagle Ford Group (EFG) and for our understanding of the Laramide orogeny. We generated clumped isotope data and organic maturation proxies from the same location. Carbonate clumped isotope temperatures obtained (113 ± 9 °C) represent recrystallization during burial and a minimum estimate of the maximum burial temperature. This constraint is significantly warmer than apparent organic temperatures derived using an Arrhenius equation (40–55 °C). Organic matter transformation and carbonate recrystallization respond to temperature over different time scales and therefore capture snapshots of the thermal history particular to the chemical reactions that control the respective processes. Using numerical forward modeling on the combination of two different temperature proxies, we derived a new hypothesis: ~2800 m of Cenozoic sediments were accumulated and then eroded during late Laramide compression. This is significantly less erosion than previous estimates, indicating the impact of the Laramide orogeny in the basin may have been less severe than previously thought.