Oxygen isotopes of marine mollusc shells record Eocene elevation change in the Pyrenees

Damien Huyghe (1, 2) , Frédéric Mouthereau (1) , Laurent Emmanuel (1)

1 iSTeP - Institut des Sciences de la Terre de Paris
2 LFCR - Laboratoire des Fluides Complexes et leurs Réservoirs

Constraining paleoaltimetry of collisional orogens is critical to understand the dynamics of topographic evolution and climate/tectonics retroactions. Here, we use oxygen stable-isotope record on oyster shells, preserved in marine foreland deposits, to examine the past elevation of the Pyrenees during the Eocene. Our approach is based on the comparison with the Paris basin, an intracratonic basin not influenced by orogenic growth. The finding of a shift of 1.5‰ between 49 and 41Ma, indicating more negative δ 18O c in the south Pyrenean foreland, is interpreted to reflect the inflow of river water sourced from higher elevation in the Pyrenees. To test this and provide paleoelevation estimate, we adopt a morphologic-hydrological model accounting for the hypsometry of drainage basin. Our best fitting model shows that the Pyrenees rose up to 2000m. This indicates that the Pyrenees reached high elevation in the Eocene, thus providing new critical constraints on their long-term orogenic development. δ 18O of marine mollusc shells are proved potentially attractive for paleoelevation studies, especially for mountain belts where elevated continental surfaces have not been preserved.

Mots clés: Oyster shells; Paleoelevation; Pyrenees; Stable isotope Eocene; Oyster shell; Paris Basin; Stable isotopes Engineering controlled terms: Isotopes; Oxygen; Shellfish; Shells (structures) Engineering main heading: Stratigraphy GEOBASE Subject Index: bivalve; elevation; Eocene; intracratonic basin; orogeny; oxygen isotope; shell; stable isotope Regional Index: France; Pyrenees Species Index: Mollusca; Ostreidae

Domaines: Sciences de la Terre

Damien Huyghe, Frédéric Mouthereau, Laurent Emmanuel. Oxygen isotopes of marine mollusc shells record Eocene elevation change in the Pyrenees. Earth and Planetary Science Letters, 2012, 345-348, pp.131-141. ⟨10.1016/j.epsl.2012.06.035⟩. ⟨hal-00909541⟩