Cantalejo Lopez, B; (2014) Impact of basin tectonics and climate change on the timing of sediment flux to the Ainsa Basin, Middle Eocene, Spanish Pyrenees. Doctoral thesis , UCL (University College London).

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Abstract

This thesis integrates sedimentological, geochemical, magnetostratigraphic and spectral work from field and core data from the Middle Eocene, deep-marine siliciclastic sediments in the Ainsa Basin, Spanish Pyrenees. The deep-marine sediments of the Ainsa Basin comprise an alternation of coarse-grained sandbodies (submarine fans) and fine-grained packages of fan lateral-margin and interfan deposits. Time-series analysis performed on spectral gamma-ray and sandstone turbidite intensity data from 10 fine-grained interfan stratigraphic sections covering ~ 1.5 km of stratigraphy, and using multiple geochemical proxies (including high-resolution elemental XRF scanning, total organic carbon and carbon stable isotopes), all show that the interfan sediments contain a strong Milankovitch cyclicity. Orbital parameters most likely paced the cyclic delivery of the finer-grained sediments mainly by river- and delta-derived hyperpycnal turbidity currents. Sediment accumulation rates determined from spectral analysis reveal an overall decrease throughout the deep-marine stratigraphy from ~ 50 to ~13cm/kyr. Orbital tuning of the fine-grained sections using polarity reversals as anchor points permits the conversion from a depth-stratigraphy to a chronostratigraphy and also allows the estimation of the timing of initiation of each sandy submarine fan. The pacing of these sandbodies appears to have occurred at irregular time intervals and to have been of variable duration. They are, therefore, most likely controlled by the tectonic pulsating activity of the Pyrenean thrust systems linked with episodic changes in relative base level (e.g., overall tilting of the graded profile from source to sink, changing relative sea level).Climate may still have been important but only as a contributory rather than principal driver of submarine-fan development.

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