Kinematic 3-D Retro-Modeling of an Orogenic Bend in the South Limón Fold-and-Thrust Belt, Eastern Costa Rica: Prediction of the Incremental Internal Strain Distribution

Abstract

The South Limón fold-and-thrust belt, in the backarc area of southern Costa Rica, is characterized by a 90°curvature of the strike of the thrust planes and is therefore a natural laboratory for the analysis of curved orogens. The analysis of curved foldand-thrust belts is a challenge because of the varying structural orientations within the belt. Based on seismic reflection lines, we created a 3-D subsurface model containing three major thrust faults and three stratigraphic horizons. 3-D kinematic retro-deformation modeling was carried out to analyze the spatial evolution of the fold-and-thrust belt. The maximum amount of displacement on each of the faults is (from hinterland to foreland); thrust 1: 800 m; thrust 2: 600 m; thrust 3: 250 m. The model was restored sequentially to its pre-deformational state. The strain history of the stratigraphic horizons in the model was calculated at every step. This shows that the internal strain pattern has an abrupt change at the orogenic bend. Contractional strain occurs in the forelimbs of the hanging-wall anticlines, while a zone of dilative strain spreads from the anticline crests to the backlimbs. The modeling shows that a NNE-directed transport direction best explains the structural evolution of the bend. This would require a left-lateral strike-slip zone in the North to compensate for the movement and thereby decoupling the South Limón fold-and-thrust belt from northern Costa Rica. Therefore, our modeling supports the presence of the Trans-Isthmic fault system, at least during the Plio-Pleistocene.

Magmatic and Tectonic Domains of Central Costa Rica and the Irazú‐Turrialba Volcanic Complex Revealed by Ambient Noise Tomography

“…This is supported by receiver function studies (Dzierma et al., 2010), finding discontinuous Moho morphologies at the CCRVF and Talamanca boundary. Proposed limits of the CCRDB from previous authors (Brandes et al., 2016; Vannucchi & Morgan, 2019) also correspond with our observations, although they did not identify such a sharp transition across the Talamanca Cordillera.…”

2-D kinematic restoration of the western Tauern Window, Eastern Alps using thermochronological and P-T constraints

“…Valid restorations require that (i) the analyzed structures display reasonable natural geometries, (ii) the geometry after retrodeformation must be reasonable, (iii) mass must be conserved and (iv) the kinematic development from the undeformed to the deformed state must be physically possible (Marshak & Wilkerson, 2004;Wilkerson & Dicken, 2001). However, standard cross-section balancing of a cross-section through the western TW is not possible, because (i) standard assumptions like plane strain conditions (Woodward et al, 1989) cannot be made and (ii), in contrast to structural restoration of deformed sedimentary basin-fills or thin-skinned foreland fold-and-thrust belts (e.g., Balling et al, 2021, Brandes et al, 2016, Tanner et al, 2003, no stratigraphic markers exist for the VD, and the SWHN were already displaced at pre-indenter stage. We therefore used other constraints:…”

From incipient island arc to doubly‐vergent orogen: A review of geodynamic models and sedimentary basin‐fills of southern Central America

“…Mechanically, the northeastward propagation of the South Limón fold-and-thrust belt is compensated by sinistral strike-slip movements along the Trans-isthmic fault system (Brandes, Tanner, & Winsemann, 2016). Towards the south the South Costa Rican arc segment is bounded by the onland projection of the subducting Panama fracture zone (J.…”

“…Fault‐scarps at the seafloor visible on seismic lines indicate ongoing deformation in the leading edge of the fold‐and‐thrust belt (Brandes, Astorga, Back, Littke, & Winsemann, , ; Brandes, Astorga, Blisniuk, et al, ). Mechanically, the northeastward propagation of the South Limón fold‐and‐thrust belt is compensated by sinistral strike‐slip movements along the Trans‐isthmic fault system (Brandes, Tanner, & Winsemann, ). Towards the south the South Costa Rican arc segment is bounded by the onland projection of the subducting Panama fracture zone (J. Krawinkel & Seyfried, ).…”

“…Balanced cross‐sections imply 8–9 % of horizontal shortening in Plio‐Pleistocene times for the external part of the fold‐and‐thrust belt in the offshore area (Brandes et al, , ). If out‐of‐sequence thrusting took place in the internal part of the fold‐and‐thrust belt, the horizontal shortening could be significantly higher.…”