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On multi-millennial scales, sedimentary systems can be disturbed by external forcings such as tectonic uplift and climate change. These environmental changes affect sediment fluxes and sediment composition from the zone sediments are produced to their deposition zone. Although we have a good understanding of how sedimentary systems react to forcings such as sea-level change, tectonic uplift or global warmings, major challenges remain concerning the record and unravelling of these signals in past sedimentary archives. These archives may hold key information for predictive models concerning actual and future environmental problems. To better understand how tectonic and climatic signals are recorded and are reflected in past sedimentary successions, an Eocene (33-56 Ma) sedimentary system in the south Pyrenean foreland basin was studied during a time-period rich in tectonic and climatic events.

Among the most urgent challenges in future climate change scenarios is accurately predicting the magnitude to which precipitation extremes will intensify. Analogous changes have been reported for an episode of millennial-scale 5 °C warming, termed the Palaeocene-Eocene Thermal Maximum (PETM; 56 Ma), providing independent constraints on hydrological response to global warming. However, quantifying hydrologic extremes during geologic global warming analogs has proven difficult. Here we show that water discharge increased by at least 1.35 and potentially up to 14 times during the early phase of the PETM in northern Spain. We base these estimates on analyses of channel dimensions, sediment grain size, and palaeochannel gradients across the early PETM, which is regionally marked by an abrupt transition from overbank palaeosol deposits to conglomeratic fluvial sequences. We infer that extreme floods and channel mobility quickly denuded surrounding soil-mantled landscapes, plausibly enhanced by regional vegetation decline, and exported enormous quantities of terrigenous material towards the ocean. These results support hypotheses that extreme rainfall events and associated risks of flooding increase with global warming at similar, but potentially at much higher, magnitudes than currently predicted.

Continental to marine correlations have always been a challenge regarding to sequence stratigraphy. The longstanding debate is about how surfaces and sedimentary packages translate from one environement to another and the various origins that have been put forward to explain them : eustastic sea level changes, sediment supply variations, subsidence pulses or tectonic variations. In the deep water system of the lower-middle Eocene Ainsa basin, in the southern Pyrenees (Spain), as well as in its fluvial counterparts in the Tremp- Graus basin, stratigraphic cyclicity in the form of repetitive packages of sand and shale alternations of intermediate timescales (10^4 to 10^6 years) has long been recognized and has typically been imputed to eustatic changes, with a modulation by active tectonics. Most of the studies have so far focused either on the deep water system or on their fluvial counterparts without a detailed effort at the correlation between both. Our objective is to evaluate the role of eustatic variations, that are well known to have taken place at these periods, in generating or modifying such cyclicities and to understand the link, at high resolution, between the continental and marine deposits. This is particularly important in order to understand how sea-level fluctuations are tided to depositional environments over multi-millennial times-scales and how the deep- sea sedimentary record can be used to reconstruct the Earth's history of surface response to climate change. To address these issues, a mapping and multi-proxy approach was undertaken in the Tremp-Graus and Ainsa basins. We focus on the middle Eocene Castissent formation, a major fluvial excursion and its deep marine time-equivalent; the turbiditie systems of Fosado, Arro and Gerbe. Through a study of carbon and oxygen stable isotopes on the bulk rock and on the organic matter, geochemistry of major and trace elements performed on two sections representing the distal marine and the continental part of the basin, we attempt to trace environmental signals across the whole source-to- sink system. These analyses coupled with thorough physical mapping on the field allow us to discuss hypotheses on the timing of deposition of the different continental sedimentary packages with repect to the marine ones.

Cyclicities in the sedimentary record have long been documented at di↵erent time and space scales. The longstanding debate is about the various origins that have been put forward to explain them : eustastic sea level changes, sediment supply variations, subsidence pulses or tectonic variations. In the deep water system of the lower-middle Eocene Ainsa basin, in the southern Pyrenees (Spain), as well as in its fluvial counterparts in the Tremp-Graus basin, stratigraphic cyclicity in the form of repetitive packages of sand and shale alternations of intermediate timescales (104 to 106 years) has long been recognized and has typically been imputed to eustatic changes, with a modulation by active tectonics. Most of the studies have so far focused either on the deep water system or on their fluvial counterparts without a detailed e↵ort at the correlation between both. Our objective is to evaluate the role of eustatic variations, that are well known to have taken place at these periods, in generating or modifying such cyclicities. This is particularly important in order to understand how sea-level fluctuations are tided to depositional environments over multi-millennial times- cales and how the deep-sea sedimentary record can be used to reconstruct the Earth's history of surface response to climate change. To address these issues, a mapping and multi-proxy approach was undertaken in the Tremp-Graus and Ainsa basins. We focus on the middle Eocene Castissent formation, a major fluvial excursion and its deep marine time-equivalent; the turbiditic sequence between the systems of Arro and Banasto ́n. Through a study of carbon and oxygen stable isotopes, geochemistry of major and trace elements and strontium dating performed on four increa- singly distal cross-sections, we attempt to trace environmental signals across the whole source-to-sink system. These analyses coupled with thorough physical mapping on the field allow us to discuss hypotheses of climatic and eustatic controls of cyclicity.