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Title: The Rheic and Palaeotethys Oceans : Palaeozoic evolution of the northern Gondwana margin in north Spain and related areas
Author: Doherty, Helen Mary
ISNI:       0000 0004 5990 6632
Awarding Body: Keele University
Current Institution: Keele University
Date of Award: 2014
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The Fold and Nappe Province of the Cantabrian Zone, NW Spain displays a prolonged and complex geological history, initiated in the late Neoproterzoic by the Cadomian compression and followed by Cambro-Ordovician, Silurio-Devonian and Carboniferous phases of extensional and strike-slip basin formation as well as Variscan compression in the Carboniferous and Alpine compression in the Palaeogene. Within this thesis, quantified structural, sedimentological and stratigraphic analyses were utilised to produce basin models for the Palaeozoic Era when this region was north of the West African sector of Gondwana in the peri-Gondwana realm. The tectonostratigraphic framework and basin fill lithofacies provide the context for a detailed megasequence interpretation, burial history and thermal maturity models, Correlation and structural panels suggest sedimentation took place on a continental rifted margin, Sedimentation is greater in the hanging-wall side of high-angle, dip-slip, normal faults indicating syn-sedimentalY evolution. Stratigraphic thickening occurs in the mid-late Cambrian to early Ordovician Period, in the north-east of the region to the north of the peri-Gondwana realm and is attributed to the initiation phases of the Rheic Ocean. Stratigraphic thickening is also observed in the Silurian (upper Llandovery) to early Devonian (Lochkovian), in the south-east of the region, parallel to the northern Gondwana margin and is attributed to rifting and the opening of the Palaeotethys Ocean. Furthermore, syn-sedimentary faults are observed within the upper Formigoso and Furada/San Pedro Formations that are late Silurian to early Devonian in age. Back-stripped fault analysis indicates that east-west and northeast-southwest trending extensional faults were active during this time. Maximum Palacozoic tectonic subsidence values range from 1,750 m to 3,485 m and indicate phases of rapid subsidence in the mid-late Cambrian to early Ordovician, late Silurian to early-middle Devonian and in the late Carboniferous Periods, Carboniferous subsidence relates to the formation of the foreland basin ahead of the Variscan thrust belt. Pseudo-wells across the Fold and Nappe province display a similar burial history signature albeit varying due to its proximity to the Cantabrian high where lower subsidence rates are observed in the lower-middle Palacozoic Era. Thermal maturity models, constrained by radiometrically dated diagenetic muscovite mica of the Tanes Member of the Barrios Formation, indicate El mean burial and diagenetic age for the Cantabrian region at 384.4 Ma (Givetian Age). Calculated vitrinite %Ro values for the Formigoso Formation source-rock, broadly equivalent to the Tannezuft Formation source-rock in North Africa, indicate maturity for oil and gas in the Fold and Nappe Province from ~389 - 299 Ma. The Southern Versant Nappes of the Montagne Noire, Southern France and the Foreland and External Nappe Zones, Southern Sardinia display a similar Palaeozoic tectonostratigraphic history to the Cantabrian Zone, due to the proximity of the these terranes in the peri-Gondwana realm.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available