Spatial Variations of Tectonic Uplift - Subducting Plate Effects on the Guerrero Forearc, Mexico

Krzysztof Gaidzik,María Teresa Ramírez-Herrera,Steven L Forman

doi:10.3389/feart.2020.573081

Krzysztof Gaidzik, María Teresa Ramírez-Herrera + Show 1 more

Open Access

https://doi.org/10.3389/feart.2020.573081

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Abstract

Uplift is the predominant factor controlling fluvial systems in tectonically deforming regions. Mountains along subduction zones force incision, aggradation, or sinuosity modifications, showing differential uplift and variations in erosion rates, in river incision, and in channel gradient produced by ongoing tectonic deformation. Thus, landscape can provide information on the tectonic activity of a defined region. Here, field studies, analysis of geomorphic indices using a digital elevation model, and dating of river terraces were undertaken to extract the following: (1) determine rates of ongoing tectonic deformation, (2) identify evidence of active faulting, and (3) explain the possible relation of ongoing differential uplift in the topography of the overriding plate with the geometry and roughness effects of subducting slab along the Mexican subduction within the Guerrero sector. Landscape analysis using geomorphic indices suggests segmentation along stream of the studied Tecpan River basin. Rates of tectonic uplift were derived from river incision rates computed with the combination of strath terrace heights and associated dating. Tectonic uplift rates vary from ∼1 ± 0.3 mm/yr up to ∼5 ± 0.6 mm/yr during the Holocene, consistent with inferred high tectonic activity in this zone. These results vary significantly spatially, i.e., increasing upstream. Possible explanations for spatial variations of tectonic uplift rates are most likely related to an effect of the geometry and the rugged seafloor of the oceanic Cocos plate subduction beneath a faulted continental lithosphere.

Highlights

Uplift is the predominant factor controlling fluvial systems in actively deforming regions, such as forearcs on overriding plates along subduction zones, forcing incision, aggradation, or sinuosity modifications
Tecpan River Segments Based on the river river longitudinal profile (RLP), transverse profiles (TP), and calculated geomorphic indices (G, Vf, sinuosity index (SI), Streamlength gradient index (SL), minimum bulk erosion (MBE), and ksn), Tecpan River shows five distinct segments with variable characteristics (Table 2, Figures 2–4, and Video 2)
High uplift rates in this segment of the Mexican subduction zone may be associated with the roughness and seamount subduction of the Cocos plate

Summary

Introduction

Uplift is the predominant factor controlling fluvial systems in actively deforming regions, such as forearcs on overriding plates along subduction zones, forcing incision, aggradation, or sinuosity modifications. The central morphotectonic segment of the MSZ (Ramírez-Herrera and Urrutia-Fucugauchi, 1999) coincides with the Guerrero Seismic Gap (GSG), characterized by the absence of significant megathrust earthquakes since 1911 (Anderson et al, 1989; Kostoglodov and Ponce, 1994) This region provides a unique opportunity to study how the tectonic framework has affected the styles, rates, and spatial and temporal variations for long-term crustal deformation and uplift in the onshore forearc region of an overriding plate (e.g., Ramírez-Herrera and Urrutia-Fucugauchi, 1999; RamírezHerrera et al, 2007; Ramírez-Herrera et al, 2009; RamírezHerrera et al, 2011; and Ramírez-Herrera et al, 2018)

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