Closing and continentalization of the South Pyrenean foreland basin (NE Spain): magnetochronological constraints

Abstract

This paper presents new magnetostratigraphic results from a 1100‐m‐thick composite section across the marine to continental sediments of the central part of the SE margin of the Ebro basin (NE Spain). Integration with existing marine and continental biochronological data allows a robust correlation with the geomagnetic polarity time scale. The resulting absolute chronology ranges from 36.3 to 31.1 Ma (Priabonian to Rupelian), and yields an interpolated age of ∼36.0 Ma (within chron C16n.2n) for the youngest marine sediments of the eastern Ebro basin. This age is in concordance with a reinterpretation of earlier magnetostratigraphic data from the western South Pyrenean foreland basin, and indicates that continentalization of the basin occurred as a rapid and isochronous event. The basin continentalization, determined by the seaway closure that resulted from the uplift of the western Pyrenees, was probably coincident with a mid‐amplitude eustatic sea level low with a maximum at 36.2 Ma. The base level drop that followed the basin closure and desiccation does not appear associated to a significant sedimentary hiatus along the margins, suggesting a late Eocene shallow marine basin that rapidly refilled and raised its base level after the seaway closing. Rapid basin filling following continentalization predates the phase of rapid exhumation of the Central Pyrenean Axial Zone from 35.0 to 32.0 Ma, determined from the thermochronology data. It is possible then that sediment aggradation at the front of the fold‐and‐thrust belt could have contributed to a decrease in the taper angle, triggering growth of the inner orogenic wedge through break‐back thrusting and underplating. Contrasting sedimentation trends between the western and eastern sectors of the South Pyrenean foreland indicate that basin closing preferentially affected those areas subjected to sediment bypass towards the ocean domain. As a result, sediment ponding after basin closure is responsible for a two‐fold increase of sedimentation rates in the western sector, while changes of sedimentation rates are undetected in the more restricted scenario of the eastern Ebro basin.

The age of the “Grande Coupure” mammal turnover: New constraints from the Eocene–Oligocene record of the Eastern Ebro Basin (NE Spain)

“…The normal and reversed ChRM directions yield antipodal Fisherian means (Fig. 3 A) which conform to the palaeomagnetic references for the Late Eocene to Early Oligocene (Barberà, 1999;Costa et al, 2010). The reversed secondary component yielded a mean value which is also concordant with the ChRM mean direction (Fig.…”

“…The basin infill is dominated by continental sediments, interfingered by two widespread marine units of Ilerdian and Lutetian-Bartonian age (Ferrer, 1971;Riba et al, 1983;Puigdefàbre-gas and Souquet, 1986;Serra-Kiel et al, 2003;Pujalte et al, 2009). Marine connection of the Ebro Basin was maintained until the Priabonian (Costa et al, 2010), when the tectonic uplift of the western Pyrenees led to the closing of the basin drainage. Since then, uninterrupted late Eocene to middle Miocene continental sedimentation progressively filled the basin and eventually, backfilled onto the thrust-belt margins (Riba et al, 1983;Coney et al, 1996).…”

“…1B and C). Integrated calcareous nannofossil and magnetostratigraphic data from the youngest marine units have yielded a Priabonian age (Cascella and Dinarès-Turell, 2009), and the marine-continental transition has been precisely dated at~36.0 Ma based on magnetostratigraphy (Costa et al, 2010). After the basin closure (Fig.…”

Drainage reorganization and divide migration induced by the excavation of the Ebro basin (NE Spain)

“…During the late Eocene-early Oligocene, the uplift in the Western Pyrenees (Puigdefàbregas et al, 1992) led to the closure of the Ebro and Duero basins as attested by the Ebro basin continentalization dated at ∼ 36 Ma (Costa et al, 2010). The center of these two basins became longlived lakes filled with lacustrine, sandy, and evaporitic deposits from the Oligocene to the Miocene (Riba et al, 1983;Alonso-Zarza et al, 2002;Pérez-Rivarés et al, 2002Garcia-Castellanos et al, 2003;Garcia-Castellanos, 2006;Larrasoaña et al, 2006;Vázquez-Urbez et al, 2013).…”

The chert from the Castelltallat Formation (south-central Pyrenees): archaeometric characterisation and archaeological implications

“…Gaspar-Escribano et al 2001). The basin was filled in endorheic conditions from the Late Eocene (Costa et al 2010), which means that it was disconnected from the sea, favouring lacustrine sedimentary systems in its central sector with a low topographic gradient, with powerful and frequent expansions and retractions, particularly suitable for the formation of chert (Bustillo 2010). Chert occurs as a common diagenetic product in both sulphate and carbonate lacustrine systems (Ortí 1990; and is often found in several lacustrine formations in the Ebro Basin.…”