Geophysical and geological constraints on the evolution of the Guadalquivir foreland basin, Spain

Abstract

This paper presents a compilation and reinterpretation of available geophysical and geological data recently acquired for the ENE-WSW Guadalquivir foreland basin, located on the northern margin of the Betic orogen in southern Iberia. The data include seismic reflection and refraction profiles, well logs, gravity, geoid, surface heat-flow data and field observations. The deep structure of the southern Iberian margin is characterized by large variations in crustal thickness and high heat-flow values, which result in a very low lithospheric rigidity for the whole area. Geoid and gravity data show that deformation affected the crust and the lithospheric mantle differently, producing anomalous mass distributions that could act as subsurface loads. Seismic sequence analysis of the basin infill has permitted the re-assessment of the depositional sequential arrangement of the sediments deposited from Late Langhian-Early Serravallian to Messinian. They are arranged in six sequences and do not show any E-W progradational pattern indicating that during this period the acting loads moved essentially in a NNW direction. A careful analysis of the southern border of the basin shows that the ‘so-called olistostromes’ correspond to lateral diapirs of squeezed Triassic evaporites and internally imbricated Miocene wedges. We discuss the results obtained in terms of palaeo-geographic environments, time distribution and nature of acting loads, and constraints for future basin modelling approaches.

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

“…In the process, the rootless and highly chaotic Guadalquivir Allochthon, a late Tortonian tectonosedimentary complex of Mesozoic and Tertiary rock units comprising diapirically emplaced Triassic evaporites and olistostromes, was formed along the southern basin margin. This was in front of the Subbetic nappe stack that was moving basinward during continued thrust loading Berástegui et al, 1998;Fernández et al, 1998). The crustal-foreland shortening and flexuring that had given rise to the basin, ceased in the late Tortonian.…”

“…From Langhian times onwards the mobile ProtoGuadalquivir trough extended northward as far as the postSerravallian Guadalquivir Basin. The in situ (late) Langhian to Serravallian deposition is represented by a three-fold succession with diatomaceous marls (Sequences 1, 2 (syn-extensional) and 3 of Fernández et al, 1998; correlative with sequences Atlantida-1 and 2 of Riaza & Martínez del Olmo, 1996). The Late Miocene fill of the actual Guadalquivir Basin consists of two Tortonian (syn-compression) sequences with diatomaceous marls (Sequences 4 and 5 of Fernández et al, 1998; sequences Atlantida-3 and Betica of Riaza & Martínez del Olmo, 1996; Sequence 5 correlated with Sequences A and B (lower part) of Sierro et al, 1996) and a single (post-compressional) sequence of latest Tortonian to Messinian age without diatomaceous marls (Sequences B (upper part) and C of Sierro et al, 1996; Sequence 6 of Fernández et al, 1998; sequence Andalucia of Riaza & Martínez del Olmo, 1996; age modified after Sierro et al, 1996).…”

“…Six (seismo)stratigraphic sequences bounded by unconformities that appear to correlate with third-order chances of the global sea level, are distinguished in the Guadalquivir basin for the Middle and Late Miocene Berástegui et al, 1998). Older, (Late) Oligocene and Early Miocene deposits are absent.…”

“…This was in front of the Subbetic nappe stack that was moving basinward during continued thrust loading Berástegui et al, 1998;Fernández et al, 1998). The crustal-foreland shortening and flexuring that had given rise to the basin, ceased in the late Tortonian.…”

“…Especially so in the post-collisional phase of late Burdigalian/Langhian and Serravallian overthrusting which followed upon the areally extensive late(st) Chattianearly Aquitanian episode of extension and the pre-collisional late Aquitanian-early Burdigalian period of contractional deformation caused by the expulsion of the 'Alboran Block' (Van der Beek & Cloetingh, 1992; Biermann, 1995). The Tortonian closure of the originally deep-marine North Betic Corridor was caused by folding and uplifting of the eastern half of the foredeep and the northward transport and emergence of the adjoining Prebetic mountain chain (especially the SSW-NNE striking thrust imbricates of the Sierra de Cazorla and the thrust anticlines of the Sierra Segura).Six (seismo)stratigraphic sequences bounded by unconformities that appear to correlate with third-order chances of the global sea level, are distinguished in the Guadalquivir basin for the Middle and Late Miocene Berástegui et al, 1998). Older, (Late) Oligocene and Early Miocene deposits are absent.…”