Sediment provenance and routing evolution in the Late Cretaceous–Eocene Ager Basin, south‐central Pyrenees, Spain

Abstract

This study constrains the sediment provenance for the Late Cretaceous-Eocene strata of the Ager Basin, Spain, and reconstructs the interplay between foreland basin subsidence and sediment routing within the south-central Pyrenean foreland basin during the early phases of crustal shortening using detrital zircon (DZ) U-Pb-He double dating. Here we present and interpret 837 new DZ U-Pb ages, 113 of which are new DZ (U-Th)/He double-dated zircons. U-Pb-He double dating results allow for a clear differentiation between different foreland and hinterland sources of Variscan zircons (280-350 Ma) by leveraging the contrasting thermal histories of the Ebro Massif and Pyrenean orogen, recorded by the zircon (U-Th)/He (ZHe) ages, despite their indistinguishable U-Pb age signatures. Cretaceous-Paleocene sedimentary rocks, dominated by Variscan DZ U-Pb age components with Permian-Triassic (200-300 Ma) ZHe cooling ages, were sourced from the Ebro Massif south of the Ager Basin. A provenance shift occurred at the base of the Early Eocene Baronia Formation (ca. 53 Ma) to an eastern Pyrenean source (north-east of the Ager Basin) as evidenced by an abrupt change in paleocurrents, a change in DZ U-Pb signatures to age distributions dominated by Cambro-Silurian (420-520 Ma), Cadomian (520-700 Ma), and Proterozoic-Archean (>700 Ma) age components, and the prominent emergence of Cretaceous-Paleogene (<90 Ma) ZHe cooling ages. The Eocene Corçà Formation (ca. 50 Ma), characterized by the arrival of fully reset ZHe ages with very short lag times, signals the accumulation of sediment derived from the rapidly exhuming Pyrenean thrust sheets. While ZHe ages from the Corçà Formation are fully reset, zircon fission track (ZFT) ages preserve older inherited cooling ages, bracketing the exhumation level within the thrust sheets to ca. 6-8 km in the Early Eocene. These DZ ZHe ages yield exhumation rate estimates of ca. 0.03 km/Myr during the Late Cretaceous-Paleocene for the Ebro Massif and ca. 0.2-0.4 km/Myr during the Eocene for the eastern Pyrenees. K E Y W O R D S foreland basins, geochronology, provenance analysis, source to sink, tectonics and sedimentation, thermochronology 486 | EAGE THOMSON eT al.

Tethyan closure drove tropical marine biodiversity: Vicariant diversification of intertidal crustaceans

“…The results show parallels with spatial patterns found in marine fish and molluscs (Barber & Bellwood, 2005;Bellwood et al, 2004;Bowen, Muss, Rocha, & Grant, 2006;Malaquias & Reid, 2009) The TTE functioned as an impenetrable dispersal barrier for marine species, fragmenting their previously continuous distributions and leading to vicariant speciation (Hou & Li, 2017). However, it formed the Gomphotherium land bridge, allowing terrestrial connections between Africa and Eurasia and providing pathways for transcontinental migration of terrestrial animals and plants (Harzhauser et al, 2007;Koufos, Kostopoulos, & Vlachou, 2005;P erezguti errez et al, 2015;Portik & Papenfuss, 2015;Zhou & Saunders, 2012).…”

“…The TTE, preceded by the northward movement of the African-Arabian plates and simultaneous counter clockwise rotation of the Arabian plate, formed the so-called Gomphotherium land bridge which permitted terrestrial interchange between Eurasia and Africa during the early Miocene (Harzhauser et al, 2007;Kapli et al, 2015). Concurrently, the TTE also caused the emergence of geographical barriers for marine species, fragmenting previously continuous Tethyan distribution ranges into Mediterranean-East Atlantic (MS-EA) and Indo-West Pacific (IWP) and leading to vicariant speciation (Hou & Li, 2017). Despite the broad importance of the final closure, its effect on marine biodiversity during this complex and prolonged process remains contentious, and the temporal patterns of vicariant events associated with TTE among various tropical marine taxa are poorly studied (Floeter et al, 2008).…”

Thermochronological and Geochronological Constraints on Late Cretaceous Unroofing and Proximal Sedimentation in the Sevier Orogenic Belt, Utah

“…DZ U-Pb MDA estimates, based on syndepositional volcanic zircon, have been shown to yield robust age constraints in retro-arc foreland basins during phases of continuous and voluminous arc magmatic activity (e.g., Dickinson & Gehrels, 2009b). The addition, zircon single-grain (U-Th)/(He-Pb) double dating has the ability to improve provenance analysis by combining DZ U-Pb crystallization ages with constraints on the source area's thermal and exhumation history (e.g., Filleaudeau et al, 2012;Rahl et al, 2003;Reiners et al, 2005;Thomson et al, 2017Thomson et al, , 2019 (Figure 4). Furthermore, double dating is also essential for the identification of first-cycle volcanic grains (U-Pb age = ZHe age) and their differentiation from exhumational cooling ages (Saylor et al, 2012).…”

“…Samples within the HePRZ, however, can display greater ZHe age variance and dispersion due to kinetic or grain specific variations modulating the effective He diffusivity, such as radiation damage, grain size and morphology, parent nuclide distribution (zoning), or variable He age inheritance (e.g., Guenthner et al, 2013;Guenthner, Reiners, DeCelles, & Kendall, 2014;Guenthner, Reiners, & Tian, 2014;Ketcham et al, 2013;Nasdala et al, 1995Nasdala et al, , 2001Nasdala et al, , 2004Reiners et al, 2002;Reiners & Farley, 2001). Hence, partially reset detrital samples represent a particular challenge when trying to reconstruct thermal histories and perform source-to-sink analyses due to common large intrasample ZHe age dispersion (e.g., Thomson et al, 2019).…”

Magnetostratigraphy and stable isotope stratigraphy of the middle-Eocene succession of the Ainsa basin (Spain): new age constraints and implications for sediment delivery to the deep waters

“…Coeval with the development of the Bóixols thrust sheet, shallow marine successions (Aren Sandstone Formation, Mey et al, 1968) and fluvial and lacustrine deposits (Tremp Group, Pujalte and Schmitz, 2005) were subsequently deposited in the eastern part of the Southern Pyrenean Zone. The asymmetrical collision between the Eurasian and the Iberian plate induced flow toward the WNW with the deposition of deep-water carbonate and siliciclastic sediments in the western part of the Southern Pyrenean Zone (Whitchurch et al, 2011, Thomson et al, 2019. During the Ilerdian stage (early Eocene), a major transgression flooded the southern basins leading to the deposition of the Alveolina Limestone Formation (Puigdefàbregas and Souquet, 1986).…”