Abstract

AbstractThe present study proposes to estimate the influence of climate, eustatism and local tectonics on the sedimentation of a basin margin at the syn-rift to post-rift transition. For that, paleomagnetic measurements were performed on a marine marly-calcareous sedimentary succession ranging from Upper Oligocene to Lower Miocene and located on the northern margin of the Liguro-Provençal basin. The magnetostratigraphic record is correlated to the reference geomagnetic polarity scale [ATNTS04, Lourens et al. 2004] with the help of biostratigraphy based on calcareous nannofossils and planctonic foraminifers [Oudet et al., 2010]. The resulting age model shows that the 100 m-thick sedimentary succession covers a time span of 5 m.y. from the Late Chattian to the Early Burdigalian. Despite several exposure surfaces and a change in the sedimentation rate, no significant hiatus of sedimentation is documented. In addition, we also estimate the paleoenvironmental evolution through the sedimentary succession. Comparing the dated paleoenvironmental reconstruction with global δ18O and sea level curves [Miller et al., 2005], we show that the Carry-le-Rouet succession is an excellent paleoclimatic archive. Indeed, coral reefs developed at the glacial-interglacial stage transition marking the end of the Oligocene. In addition, the most diversified coral reefs occurred during the warmest period of the Aquitanian. During rifting, bathymetric variations recorded in the studied succession are related to local synsedimentary tectonics whereas, during oceanic crust accretion, global sea level changes influence the sedimentation. This result allows to characterise and to accurately date the break-up unconformity at 20.35 Ma.

Highlights

  • The syn-rift to post-rift transition during basin opening is marked by the shift of deformation from the margin to the basin due to oceanic crust accretion

  • Sedimentation occurs on tilted blocks and under a strong tectonic activity whereas during post-rifting, sediments are deposited under quiet tectonic conditions

  • The paleoenvironmental study of syn-rift and post-rift sediments lying on a basin margin is of high interest since it allows to estimate the relative influence of climate, glacio-eustatism and tectonics on sedimentation

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Summary

Introduction

The syn-rift to post-rift transition during basin opening is marked by the shift of deformation from the margin to the basin due to oceanic crust accretion. This shift affects sedimentation on the basin margin [Einsele, 2000 and references therein]. The syn-rift to post-rift transition is marked on seismic profiles by a break-up unconformity, separating syn-rift sedimentary bodies with complex geometries from large and flat post-rift sedimentary bodies [e.g., Gorini et al, 1993]. The paleoenvironmental study of syn-rift and post-rift sediments lying on a basin margin is of high interest since it allows to estimate the relative influence of climate, glacio-eustatism and tectonics on sedimentation

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