Neotectonic features of the Catalan Coastel Ranges, Northeastern Spain

Abstract

The Catalan Coastal Ranges constitute the northwestem emerged sector of the Catalan-Valencian domain of the Valencia trough. Since late Oligocene this domain of the Valencia trough was subjected to extension wich gradually attenuated during later periods. The Miocene tectonic evolution of the Catalan Coastal Ranges is relativelly well known while the Pliocene to-Quaternary stages have not been studied in detail. The recorded seismicity of the area is moderate and constant but not sufficiently intense to cliaracterize and locate recent tectonics. However, geological analysis provides further information. A morphotectonic and deformational analysis of the Catalan Coastal Ranges is presented in this paper. Three main mountain fronts which show characteristic neotectonic features are examined: El Camp, El Baix Ebre and El Montseny mountain fronts. These fronts have faceted spurs, -with more than one generation in El Camp and El Montseny fronts-, moderate to low sinuosity (1.30-1.50), orthogonal drainage across the fault, "wine glass" drainage basins with moderate Se/L index -0.52 in El Baix Ebre front- and convexity in the topogr4phic profiles orthogonal to the front. Severa1 fault scarps are aligned parallel to the main faults in the southern half of the studied zone. Morphological anomalies are also apparent in the fluvial network, for example: asymmetrical drainage basins indicating tilting. Segmentation is noticeable in St. Jordi alluvial fan located near the Baix Ebre basin. Brittle deformation in Pliocene and Quaternary sediments is sparse, but is evident in St. Onofre outcrop (Baix Ebre) with normal faulting with vertical o1 and NNW-SSE ~3 in Pliocene sediments and NNW-SSE normal faults in Quaternary sediments. Liquefaction deformational features are described and may be related to paleoseismology. Vertical normal slip is inferred for the main neotectonic mountain fronts with more activity concentrated in the southern Catalan Coastal Ranges. Present-day tectonic activity is characterized as very small.