Climate signals in Middle Eocene deep-marine clastic systems, Ainsa Basin, Spanish Pyrenees

Abstract:

The Ainsa Basin, Spanish Pyrenees, occupies a crucial position between the non-marine, marginal-marine and shallow-marine environments that acted as the sediment-supply and staging areas for sediment transfer processes into the deep-marine environments of the Ainsa Basin, and the more distal Jaca and Pamplona basins. Studies of source-to-sink systems make the Eocene stratigraphy of the Pyrenees and adjoining areas one of the best natural laboratories worldwide for understanding a complete sedimentary system. The hydrocarbon industry requires good predictive models for the distribution of reservoir and non-reservoir deposits. Using a wide range of proxy physical and geochemical data, we show with a high degree of confidence that Milankovitch forcing at a range of astronomical scales controlled deposition of the thin-bedded, fine-grained sandy turbidites and hemipelagites throughout the basin (~ 70% of the stratigraphy). The driver on sandy channelised submarine-fan deposition (the principal sandbodies) cannot be simply related to Milankovitch frequencies and is likely to be due to a combination of climatic, tectonic and/or autocyclic processes.