Geomorphic signature of segmented relief rejuvenation in the Sierra Morena, Betic forebulge, Spain

[摘要] The foreland relief of alpine orogenic belts is often rejuvenated due to the intraplate propagation of orogenic deformation. Thus, in these long-lived areas, the localisation of relief rejuvenation may be largelycontrolled by the reactivation of previous mechanical discontinuities. Inthis regard, we explored the relationship between the relief rejuvenationpattern and the distribution, geometry, and kinematics of faults in a widesegment of the Betic foreland (Sierra Morena, southern Spain). Specifically, we focused on the forebulge, a WSW–ENE flexural relief thatformed, paired to the Betic foreland basin, in response to orogenic load.For this purpose, we applied both qualitative and quantitativegeomorphological tools, including geomorphic indices and knickpoint patternmodelling in χ  space. We found that the pattern of relief rejuvenationresponds to large-scale flexural uplift coupled with the tectonic activityof two groups of faults that often show evidence of reactivation, namely 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 the 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 SierraMorena/foreland basin limit. The knickpoint pattern also suggests asignificant reorganisation of the analysed drainage basins. The strainpartitioning accommodated by the structures involved in relief rejuvenationsuggests the intraplate propagation of the transpressional deformationreported from the Betic external fold and thrust belt.

[学科分类] 土壤学