The Late Cenozoic landscape development in the westernmost Mediterranean (southern Spain)

Abstract

The terrains of the Western Costa del Sol in the westernmost Mediterranean represent an outstanding example of the influence of major tectonic and climatic factors in the development of the landscape. This region belongs to the Alboran domain, which is a small continental lithosphere fragment embedded between the large Eurasian and African plates. The territory between Malaga and Marbella is composed mainly of the Sierra de Mijas and three adjacent subsidence areas: Malaga, Torremolinos, and Fuengirola basins. From the late Miocene, dip-faults of approximate directions N-S, NE-SW and NW-SE limited the Sierra de Mijas with respect to the adjacent subsidence areas and have marked the main features of the coastal morphology. Since then, the Sierra underwent mainly erosive processes linked to strong uplifting, while the surrounding basins were subjected to alternate stages of sedimentation and erosion. Thus, the paleogeographic and geomorphological evolution has been driven both by the regional tectonics and by significant base-level changes ranging from the spectacular Messinian low-stand to the catastrophic overflow at Gibraltar, followed by the global Late Tertiary and Quaternary sea-level changes.In the mountain relief, three different erosive leveling surfaces have been recognized, which developed in a staggered sequence during the Miocene, and are currently fragmented by tectonics at different elevations. The first two leveling surfaces, continental in origin, were carved during the Middle Miocene pro-part. The late one, correlating with Upper Miocene marine deposits from the Malaga basin, appears to correspond partially to an abrasion platform developed during the highstand of the late Tortonian. The strong incision of the fluvial network, especially due to the low sea-level during the Messinian salinity crisis, but also to the tectonic rise of the Sierra, has largely eroded these surfaces, which can be recognized only in narrow inter-fluvial areas.The noteworthy marine transgression in the Miocene-Pliocene transition reached the edge of the Sierra de Mijas, developing both a broad marine abrasion platform around it and the main stage of sedimentary filling in the Malaga basin. Tectonics combined with sea-level changes influenced the formation of a lower, second abrasion platform in the Torremolinos sector and along the S edge of the Sierra, showing continuity with the late Zanclean marine deposits in the Torremolinos and Fuengirola areas. During most of the late Pliocene and the Gelasian, the region remained emerged and subjected to erosion. Conversely, climate-eustatic changes throughout the Pleistocene and Holocene led to the development of three major generations of progradant alluvial fans interrupted by stages of erosion and incision of the fluvial network. In parallel, up to five episodes of travertine build-up occurred, usually coinciding with the humid and warm, odd-numbered isotopic stages.