Formation of the Maturín Foreland Basin, eastern Venezuela: Thrust sheet loading or subduction dynamic topography

Abstract

The Maturín Basin in eastern Venezuela is considered a good example of a peripheral foreland basin. Earthquake and tomographic data indicate that eastern Venezuela is affected by the oblique subduction of the South American Plate underneath the Caribbean Plate. New forward flexural isostatic modeling of eastern Venezuela has been carried out in order to determine whether the Maturín Basin was generated purely by thrust sheet loading from the Serranía and Monagas Foreland Thrust Belts. A sequence of forward models from middle Miocene to Present was generated for 3 profiles across the Serranía del Interior Thrust Belt, the Monagas Foreland Thrust Belt, and the Maturín Foreland Basin. The predictions of these models are constrained using seismic reflection and well data. The flexural isostatic modeling shows that thrust sheet loading associated with the Serranía del Interior and Monagas Foreland thrust belts is insufficient to generate the observed subsidence within the Maturín Basin. Dynamic fluid flow modeling of subduction related dynamic topography of eastern Venezuela has been used to investigate the influence of South American Plate subduction on the generation of the accommodation space observed in the Maturín Basin. Fluid flow modeling of subduction related dynamic topography suggests that the subduction of the South American lithospheric mantle caused downward deflection of the South American crust affecting the Maturín Basin and the Serranía Thrust Belt. This modeling suggests that the Maturín Basin subsidence has two components: 55% related to thrust sheet loading and 45% driven by continental subduction.

Negligible convergence and lithospheric tearing along the Caribbean–South American plate boundary at 64°W

“…They found that significant vertical displacements can derive from flexural bulging, asthenospheric flow, and viscous coupling with the subducting slab. Jácome et al [2003] demonstrated that thrust sheet loading could only account for 55% of the subsidence of the Maturin Basin, calculated using 96 km of shortening beneath the Serrania del Interior and foothills. Shortening of only 35 km onshore implies that basin subsidence due to thrust sheet loading is significantly less than 50%.…”

“…South of the frontal thrust of the Monagas Foothills, the Maturin Basin, generally regarded as a peripheral foreland basin, formed concurrently with the thrust belts of the Serrania del Interior [Passalacqua et al, 1995;Roure et al, 1994]. However, thrust sheet loading alone does not adequately account for the 10 km of subsidence [Jácome et al, 2003]. The Maturin Basin is the southernmost region imaged by 64W.…”

“…Shortening of only 35 km onshore implies that basin subsidence due to thrust sheet loading is significantly less than 50%. Jácome et al [2003] attribute the remainder of the subsidence to dynamic topography related to continental subduction; Clark et al [2008] show that continental subduction has not occurred in northeastern Venezuela. Instead, vertical tectonics associated with the STEP tear, as modeled by Govers and Wortel [2005], must play an integral role in orogenic uplift and basin subsidence, as well as in the second stage of metamorphic exhumation.…”

New Bouguer Gravity Maps of Venezuela: Representation and Analysis of Free-Air and Bouguer Anomalies with Emphasis on Spectral Analyses and Elastic Thickness

“…[49] used seismic refraction data to estimate a maximum of 10-13 km of sedimentary infill for this basin. According to Jácome et al [14], the amount of sediments is the result of multiple processes: (a) flexural loading of the Cordillera de la Costa range, (b) large and continuous deposition of continental material from the Guyana shield as the main source, and (c) the subduction dynamics of oceanic South America underneath the Caribbean plate. The spectral analysis of the Bouguer anomaly (Figure 6(d)) estimated an anomaly source located 12 km deep that may correspond to the top of the basin basement.…”

“…Barinas-Apure is mainly a foreland basin generated by the flexural response to the Mérida-Andes Mountain load [13]. On the other hand, the Eastern basin can be considered to be the result of (a) flexural loading of the Cordillera de la Costa range, (b) large and continuous deposition of continental material from the Guyana shield, and (c) subduction dynamics in the east [14]. The Barinas-Apure and Eastern Venezuelan sedimentary basins are separated by a geomorphologic-structural high called El Baúl High, formed by an igneous-metamorphic complex.…”