Chronology of the late Turolian deposits of the Fortuna basin (SE Spain): implications for the Messinian evolution of the eastern Betics

Abstract

The magnetostratigraphy of the mammal-bearing alluvial fan-fan delta sequences of the Fortuna basin (SE Spain) has yielded an accurate chronology for the late Turolian (Messinian) basin infill. From early to late Messinian (at least between 6.8 and 5.7 Ma), the Fortuna basin records the sedimentation of alluvial-palustrine deposits over a confined shallow basin. Changing environmental conditions in the latest Messinian are illustrated by the retreat of palustrine facies. A rapid progradation of the marginal clastic wedges and the initiation of an efficient basin drainage at ¾5.8 Ma (lower part of chron C3r) most likely represents the onshore response to the drastic drop of base level taking place during the Messinian salinity crisis. This study further provides improved age estimates for the late Turolian land mammal events in southern Spain. The oldest MN 13 locality in the studied sections is correlated to chron C3Ar at an age of 6.8 Ma. The entry of camels and the murid Paraethomys in southern Spain occurs in chron C3An.1n at 6.1 Ma, and gives further support for land mammal exchange between Africa and the Iberian peninsula prior to the salinity crisis, in good agreement with results from northern Africa [M. Benammi, M. Calvo, M. Prévot, J.J. Jaeger, Magnetostratigraphy and paleontology of Aït Kandoula basin (High Atlas, Morocco) and the African-European late Miocene terrestrial fauna exchanges, Earth Planet. Sci. Lett. 145 (1996) 15-29]. The age of the studied sequences provides important constraints on the understanding of the sedimentary evolution of the eastern Betic margin, and shows that previous interpretations of the evaporitic-diatomitic sequences of the Fortuna basin, as being coeval to the late Messinian salinity crisis in the Mediterranean, are not correct. The confinement leading to the emergence of the Fortuna basin occurred in the late Tortonian to earliest Messinian, similar to other intramontane basins in the Betics. Therefore, the inclusion of the Fortuna basin in a hypothetical marine Betic Corridor during the late Messinian is no longer tenable.

Tectonic control for evaporite formation in the Eastern Betics (Tortonian; Spain)

“…Although subsidence continued, this region shows a gradual transition via diatomites and evaporites to continental deposits between 7.8 and 7.6 Ma, marked by a drastic change in basin configuration. Continuously ongoing subsidence furthermore accommodated a thick series of more than 1 km of Mio-Pliocene continental deposits (Garcés et al, 1998(Garcés et al, , 2001. In summary, the Fortuna basin experienced continuous subsidence, simultaneously with the Murcia-Cartagena basin being uplifted (Fig.…”

Astrochronology for the Messinian Sorbas basin (SE Spain) and orbital (precessional) forcing for evaporite cyclicity

“…The basins that were part of the Betic Corridor (the marine connection through Spain between the Mediterranean and Atlantic in pre-Messinian times) have been uplifted at approximately the Tortonian/Messinian boundary and generally show a transition of marine to continental facies (Rodrõ Âquez-Ferna Ândez et al, 1984;Rodrõ Âquez-Ferna Ândez and Sanz de Galdeano, 1992;Weijermars, 1988;Garce Âs et al, 1998;Soria et al, 1999). This strongly indicates that the Betic Corridor became progressively closed during the latest Tortonian/earliest Messinian.…”

Punctuated Neogene tectonics and stratigraphy of the African-Iberian plate-boundary zone: concurrent development of Betic-Rif basins (southern Spain, northern Morocco)

“…During the late Chattian-early Aquitanian the Ciudad Granada Formation, a transgressive syn-rift sequence of relatively fine-grained clastics that partly accumulated in deep-water graben structures, was laid down while extensional tectonics prevailed in the Western Mediterranean (Geel & Roep, 1999;Serrano et al, 2007). These older formations have all been tectonized into imbricate units during the regionally important tectonometamorphic 'Aquitanian Paroxysm' when the 'Alboran Block' began to move westward and to disintegrate by rifting and thrusting (Geel & Roep, 1999 Garcés et al, 1998). This formation comprises gypsiferous marls and massive evaporites (Chicamo Gypsum,Tale Gypsum, Librilla Gypsum) at the base and diatomites and marls at the top.…”