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Chasing the 400 kyr pacing of deep-marine sandy submarine fans: Middle Eocene Ainsa Basin, Spanish Pyrenees

Cantalejo, B; Pickering, KT; Miller, KG; Niocaill, CM; (2021) Chasing the 400 kyr pacing of deep-marine sandy submarine fans: Middle Eocene Ainsa Basin, Spanish Pyrenees. Journal of the Geological Society , 178 (1) , Article jgs2019-173. 10.1144/jgs2019-173.

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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.

Type: Article
Title: Chasing the 400 kyr pacing of deep-marine sandy submarine fans: Middle Eocene Ainsa Basin, Spanish Pyrenees
DOI: 10.1144/jgs2019-173
Publisher version: http://dx.doi.org/10.1144/jgs2019-173
Language: English
Additional information: This version is the author accepted manuscript. For information on re-use, please refer to the publisher’s terms and conditions.
Keywords: SOUTH-CENTRAL PYRENEES, SEA-LEVEL CHANGES, LATE QUATERNARY, TURBIDITE SEDIMENTATION, SEQUENCE STRATIGRAPHY, DISPLACEMENT RATES, BOLTANA ANTICLINE, TECTONIC CONTROL, DELTAIC COMPLEX, MISSISSIPPI FAN
UCL classification: UCL
UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Earth Sciences
URI: https://discovery.ucl.ac.uk/id/eprint/10124442
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