This study presents the first radioisotopic ages from tephra deposits interbedded within the carbonate succession of the Cabo de Gata Range in SE Spain. These carbonate rocks represent a reference Miocene sedimentary record for the western Mediterranean, marked by the widespread development of coral reefs dominated by the genus Porites. Although Porites reefs at Cabo de Gata, and broadly across the western Mediterranean, have been assigned to the late Tortonian–Messinian, two new 40Ar/39Ar ages (11.71 ± 0.11 Ma just below the base and 11.64 ± 0.18 Ma within the Porites interval) constrain their formation in the type section of La Molatilla-La Molata to the terminal Serravallian–earliest Tortonian. The radioisotopic dating of an additional tephra layer interbedded within coastal oyster- and bryozoan-bearing calcirudites, overlying the volcanic basement in Los Escullos area, and previously assigned to the late Tortonian, yielded an earliest Tortonian age of 11.29 ± 0.03 Ma. The Los Escullos tephra lies c . 4 m above sea level and about 100 m below terminal Serravallian tephra at La Molatilla-La Molata, suggesting a major sea-level drop of tens of meters during the earliest Tortonian. The findings highlight a more complex Miocene chronostratigraphy in the Cabo de Gata than previously recognized, indicating that lithostratigraphic units with similar facies and comparable stratigraphic positions, such as skeletal calcarenites and calcirudites overlying the volcanic basement or Porites reefs, may vary significantly in age here and across the western Mediterranean.
Bover-Arnal et al. (Thu,) studied this question.