Affiliation:
1. Department of Earth Sciences, University College London (UCL), Gower Street, London WC1E 6BT, UK
2. Department of Earth and Planetary Sciences, Rutgers University, Piscataway, NJ 08854, USA
3. Department of Earth Sciences, University of Oxford, Oxford OX1 3AN, UK
Abstract
In an attempt to understand the relative importance of climate and tectonics in modulating coarse-grained sediment flux to a tectonically active basin during what many researchers believe to be a greenhouse period, we have studied the Middle Eocene deep-marine Aínsa Basin, Spanish Pyrenees. We use orbital tuning of many spectral gamma-ray-logged fine-grained siliciclastic sections, already shown to contain Milankovitch frequencies, in conjunction with a new high-resolution palaeomagnetic study through the basin sediments, to identify polarity reversals in the basin as anchor points to allow the conversion of a depth-stratigraphy to a chronostratigraphy. We use these data, in conjunction with a new age model incorporating new biostratigraphic data, to pace the development of the deep-marine sandy submarine fans over c. 8 million years. Timing for the sandy submarine fans shows that, unlike for the fine-grained interfan sediments, coarse-grained delivery to the basin was more complex. Approximately 72% of the sandy fans are potentially coincident with the long-eccentricity (400 kyr) minima and, therefore, potentially recording changing climate. The stratigraphic position of some sandy fans is at variance with this, specifically those that likely coincide with a period of known increased tectonic activity within the Aínsa Basin, which we propose represents the time when the basin was converted into a thrust-top basin (Gavarnie thrust sheet), presumably associated with rapid uplift and redeposition of coarse clastics into deep-marine environments. We also identify sub-Milankovitch climate signals such as the c. 41.5 Ma Late Lutetian Thermal Maximum. This study demonstrates the complex nature of drivers on deep-marine sandy fans in a tectonically active basin over c. 8 Myr. Findings of this study suggest that, even during greenhouse periods, sandy submarine fans are more likely linked with times of eccentricity minima and climate change, broadly consistent with the concept of lowstand fans. However, hysteresis effects in orogenic processes of mountain uplift, erosion and delivery of coarse siliciclastics via fluvial systems to coastal (deltaic) and shallow-marine environments likely contributed to the complex signals that we recognize, including the 2–3 Myr time gap between the onset of deep-marine fine-grained sediments in the early development of the Aínsa Basin and the arrival of the first sandy fans.Supplementary Materials: Filtered records for each of the analysed gamma-ray logged sections. Anchor points, SARs tables and graphs and alternative tuning sections are available at: https://doi.org/10.6084/m9.figshare.c.5132975
Publisher
Geological Society of London
Reference161 articles.
1. Reconnaissance study of the ancient Zaire (Congo) deep-sea fan. (ZaiAngo Project)
2. Arbués, P. , Muñoz, J.A. , Poblet, J. , Puigdefàbregas, C. and McClay, K. 1998. Significance of submarine truncation surfaces in the sedimentary infill of the Aínsa basin (Eocene of south-central Pyrenees, Spain). 15th International Sedimentological Congres, Alicante, Spain. Publicaciones de la Universidad de Alicante, 145–146.
3. Turbidite deposition on the glacially influenced, canyon-dominated Southwest Grand Banks Slope, Canada
4. Morphology and architecture of the present canyon and channel system of the Zaire deep-sea fan;Babonneau;Marine and Petroleum Geology,2002
5. Architecture and sedimentology of the Kerinitis Gilbert-type fan delta, Corinth Rift, Greece