Sedimentology of geomorphologically controlled Quaternary tufas in a valley in southern Spain

Abstract

Four vertical facies sequences characterizing different environments have been identified in relation to two phases of tufa deposition (probably Pleistocene and Holocene) within a valley located in the central sector of the Betic Cordillera (southern Spain): (1) alluvial-fluvial (non-tufa) deposits, (2) fluvial tufa, (3) fluvio-lacustrine facies, and (4) spring with waterfall tufa. The first three created a stepped axial depositional system and the spring with waterfall tufa formed a transverse system. During the first phase of tufa construction, the vertical evolution in the axial system from alluvial-fluvial (non-tufa) to fluviolacustrine tufa deposits is interpreted as the consequence of geomorphological control. The evolution through time from a high-gradient and stepped fluvial system to a lowgradient fluvio-lacustrine system occurred upstream from where the progradation of the transverse, perched spring tufa system became narrower and finally dammed the valley. The tufa barrage caused an increase in the vertical accumulation within the axial system and a consequent upstream decrease of accommodation space and slope of the longitudinal profile. After a period of fluvial incision, tufa formed again during the Holocene in a high-gradient and stepped fluvial system.