South central Pyrenean foreland basin fill preserves the eroded remnants of the early stages of fold‐thrust belt evolution and topographic growth. Specifically, the Eocene Hecho Group in the Ainsa Basin contains a succession of turbiditic channels and levees deposited in the transition zone between the fluvial‐deltaic and deep marine depozones. Detailed isotopic provenance analyses allow for the reconstruction of sediment sources of the ancient sediment routing systems. This study presents 2332 new detrital zircon (DZ) U‐Pb ages and 246 new DZ double‐dated (U‐Th)/(He‐Pb) ages from 19 turbiditic and fluvio‐deltatic sandstones in the Ainsa Basin. These data indicate a progressive provenance shift from Cadomian/Caledonian plutonic and metamorphic rocks of the eastern Pyrenees to Variscan plutonic rocks in the central Pyrenees. Minor sediment contributions from sources located to the S and SE of the basin are seen throughout the section. New DZ (U‐Th)/He results identify four main cooling events: Pyrenean orogenesis (~56 Ma), initial basin inversion (~80 Ma), Cretaceous rifting (~100 Ma), and pre‐Mesozoic cooling ages related to earlier tectonic phases. This study imposes new constraints on the paleogeographic evolution of the Pyrenees and illustrates that high‐frequency fluctuations in sediment delivery processes and sediment routing introduce superimposed noise upon the basin‐scale long‐term provenance evolution during orogenesis.

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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.

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Purple Bench is a middle Eocene fossil locality in the Devil's Graveyard Formation of the Trans-Pecos region of West Texas. In addition to yielding a range of taxa characteristic of the Uintan North American Land Mammal Age, the Purple Bench locality is noteworthy in documenting a number of endemic species that are known only from the site. Despite the Uintan character of the mammalian fauna, the absolute age of Purple Bench is a matter of debate. This uncertainty stems from the wide interval of time encompassed by current radiometric dates bracketing the Purple Bench locality and from conflicting magnetostratigraphic correlations in the Devil's Graveyard Formation. This study constrains the absolute age of the Purple Bench locality through detrital zircon U-Pb geochronological analyses. For these analyses, 147 new detrital zircon U-Pb ages were collected from five tuffaceous sandstones and reworked tuff horizons and analyzed via Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS). These new detrital zircon U-Pb geochronological analyses suggest a maximum depositional age of 43.7 +0.8 /-0.2 Ma for the Purple Bench tuff, a significant marker horizon immediately below the Purple Bench locality. These new maximum depositional age dates presented here provide constraints on the true depositional age of the lower and middle members of the Devil's Graveyard Formation, bringing clarity to the previously ambiguous age of the fossil-bearing Purple Bench locality. The age constraints presented here also aid the characterization of the temporally and spatially variable Uintan North American Land Mammal Age.