Preprints
https://doi.org/10.5194/esurf-2022-29
https://doi.org/10.5194/esurf-2022-29
 
08 Jun 2022
08 Jun 2022
Status: this preprint is currently under review for the journal ESurf.

Geomorphic signature of relief rejuvenation in Sierra Morena (Betic forebulge, Spain): evidence of segmented uplift in a strongly strain-partitioned, tectonic scenario

Inmaculada Expósito1, Alejandro Jiménez-Bonilla1,, Michele Delchiaro2,, José Luís Yanes1, Juan Carlos Balanyá1, Francisco Moral1, and Marta Della Seta2 Inmaculada Expósito et al.
  • 1Departamento de Sistemas Físicos, Químicos y Naturales, Universidad Pablo de Olavide, Seville, 41013, Spain
  • 2Department of Earth Sciences, Sapienza University of Rome, Rome, 00185, Italy
  • These authors contributed equally to this work.

Abstract. The foreland relief of Alpine orogenic belts is often rejuvenated due to the intraplate propagation of orogenic deformation. Thus, in these long-lived areas, localization of relief rejuvenation may be greatly controlled by reactivation of previous mechanical discontinuities. In this regard, we have explored the relationship among relief rejuvenation pattern and the distribution, geometry and kinematics of faults in a wide sector of the Betics foreland (Sierra Morena, Southern Spain). Specifically, we have focused on the forebulge, a WSW-ENE oriented flexural relief that formed, paired to the Betics foreland basin, in response to orogenic load. For this purpose, we have applied both qualitative and quantitative geomorphological tools, including geomorphic indexes and knickpoints pattern modelling in χ space. We have found that the pattern of relief rejuvenation responds to tectonic activity of two groups of faults that often show evidence of reactivation: overall WSW-ENE faults contributing to both regional NNW-SSE relief segmentation and vertical extrusion of the forebulge, and NW-SE reverse faults associated with an outstanding WSW-ENE topographic segmentation in the west of the study area. In addition, our knickpoint modelling suggests that faults related to the southernmost Sierra Morena mountain front have been particularly active in recent times, although their activity span and the relative uplift that they accommodate differ along the Sierra Morena/foreland basin limit. Knickpoint pattern also suggests a significant reorganization of the analysed drainage basins. The strain partitioning accommodated by the structures involved in relief rejuvenation suggests intraplate propagation of the transpressional deformation reported from the Betics external fold and thrust belt.

Inmaculada Expósito et al.

Status: open (until 20 Jul 2022)

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Inmaculada Expósito et al.

Inmaculada Expósito et al.

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Short summary
In long-lived areas, relief rejuvenation can be greatly controlled by both the geometry of reactivated structures and the kinematics setting. We have applied geomorphological qualitative analyses, geomorphic index and knickpoints modelling to detect Quaternary reactivation of fractures in the Betics foreland (southern Spain). The obtained relief rejuvenation pattern and fault kinematics agree with propagation of transpressional deformation from the Betics fold and thrust belt.