Heavy-mineral assemblages as a provenance indicator in the Jaca basin (Middle-Late Eocene, southern Pyrenees)

Copyright© 2017 Sociedad Geológica de Españ The Jaca sequence records a major paleogeographic change in the south-central-pyrenean basin, recorded by the replacement of the deep-marine Hecho Group turbidites (Upper Lutetian) by deltaic and alluvials (Bar-tonian-Priabonian). This work studies the heavy-mineral assemblages of the Eocene clastic systems in the northern Jaca basin, applying optical analysis and Raman spectroscopy. All the clastic systems display impoverished heavy-mineral suites, mainly constituted by titanium oxides, apatite, zircon and tourmaline. Other heavy minerals, as staurolite, weathered pyrite, goethite and hematite, are found in the alluvial systems. Our results show a major heavy-mineral content shift along the transition from turbidites to shallow-water and continental deposits. The turbiditic systems display high content of apatite sourced from the Axial Zone in the eastern Pyrenees, whereas the alluvial systems are characterized by a heavy-mineral suite containing goethite and staurolite. The shift is here interpreted as related to the onset of the Gavarnie thrust, which resulted in the uplift and recycling of the turbidites as well as the exhumation of Paleozoic basement, located to the north of the Jaca basin.