Registro de la variación de la tasa de deslizamiento de la Falla de Carrascoy en los últimos ~220 ka (Béticas Orientales, SE de España)

Abstract

We present evidence of the variability of the slip rate at the NE segment of the Carrascoy Fault (Los Ramos, Murcia) based on geochronological analysis and modelling reconstruction of a progressive discordance in alluvial sediments showing cons- picuous carbonate enrichment beds (calcretes). Calcretes were dated using the Uranium Series technique, except for two of them that the age was assigned by correlation with isotopic stages of the Quaternary geochronology. The age of the calcretes range from the ~220 ka to ~34 ka, one of them located in the Upper to Intermediate Pleistocene limit. Vertical slip on the fault for each calcrete period was obtained by modelling the growth of the discordance, and hence, the slip rate variation in the last 220 ky. Our results suggest that the activity of the fault shows a cyclic behavior with long quiescence periods (~90 ka) followed by much shorter ones of high activity (~10 ka). Vertical slip rates were converted to net slip rates values using the striae (slip vector) that was deduced in a nearby area were the fault offsets streams (horizontally) and fan surfaces (ver- tically) Upper Pleistocene-Holocene in age. The net slip rates obtained here are consistent with the ones already estimated for other faults in the Eastern Betics Shear Zone. The consistency of this observation suggests that even though vertical and lateral slip rates can vary strongly depending the geometry of the fault, net values remain constant.