Magnetobiochronology of the Late Eocene-Early Oligocene deposits of the western South Pyrenean Foreland Basin (NE Spain); tectono-sedimentary and paleoclimatic implications

We present a new magnetobiostratigraphic study, the Martes composite section in the South Pyrenean Foreland Basin, which we conducted to assess the impact that tectonic processes and past periods of global climate change have in shaping the sedimentary record of foreland basins. Our results indicate that sustained high sedimentation rates throughout much of the succession (ca 40–33.2 Ma, middle Bartonian-early Rupelian) signal a basin-wide response to tectonic loading along the internal part of the neighbouring Pyrenean orogen. Such activity intensified between 39.7 and 37.4 Ma, and resulted in temporally decreased in sedimentation rates that recovered high values only when terrigenous supply was able to keep up pace with accommodation space. We identify development of a paleogeographic high in the central part of the basin >39.6 Ma, which attest to the yet underappreciated influence that tectonic inheritance can exert in partitioning the sediment routing systems within foreland basins. Our results also provide the ultimate evidence demonstrating the rapid continentalization of the basin at ~36.1 Ma, due to a combination of tectonic uplift and a sea level drop. Even against this backdrop of intense tectonic activity, globally increased temperatures during the Middle Eocene Climate Optimum and an Early Priabonian period led to an increase in sediment supply to the marine realm in response to an enhanced hydrological cycle. In contrast, cooling associated to the Eocene-Oligocene was not associated to any significant shift in sediment supply, but rather to an increase in the occurrence of magnetite that formed pedogenically under conditions of enhanced rainfall and/or seasonality.