On the geology of the Alpujarride complex in the Western Sierra de las Estancias (Betic Cordilleras, SE Spain)

Abstract

The Alpujarride complex in the western sierra de las Estancias comprises a pelite-psammite Sequence and an overlying carbonate sequence. A Ladinian to Late Triassic age seems most likely for the carbonate sequence, while a Middle Triassic and possibly older age is inferred for the remaining part of the section. The tectono-metamorphic evolution took place during the Alpine orogeny. No indications have been found for pre-Alpine metamorphism and deformation. The rock sequences have been affected by plurifacial metamorphism during three metamorphic events' The first event (M1) involved an increase in temperature under low to intermediate pressure, resulting in a prograde metamorphism up to amphibolite facies. M1 seems related to the intrusion of hot ultramafic masses. This event was followed by retrograde metamorphism (M2). Renewed increase of temperature, without a change of the existing low-pressure conditions, locally caused a third metamorphic event (M3). The plurifacial metamorphism was accompanied by polyphase deformation. The first phase (D1) resulted in mainly isoclinal, similar folds. During the second phase (D2) important translations gave rise to the superposition of at least three major overthrust masses. Associated folds have a vergence to the north, indicating a northerly direction of transport. Subsequently the rock sequences have been deformed into S to SE vergent folds, N to NW dipping reverse faults, E-W trending subvertical faults and into NNW trending wrench faults.