The Rheic Ocean Passive Margin: a syn-sedimentary response Helen Doherty Earth Sciences, William Smith Building, Keele University, Staffordshire, ST5 5BG Email: [email protected]
Figure 1.1: A palaeogeographic map highlighting the location of the continents of Gondwana, Avalonia, Baltica and Laurentia at the time 480Ma of the Rheic Ocean origination(1)
30° N 1. Research Focus: The origin, evolution and closure of the (~400 million year old) Rheic Ocean is controversial (Figures 1.1 and 1.2). In particular, the evolution at the northern Gondwana margin (Africa and Spain) remains especially enigmatic. The history of the Rheic Ocean documents a chain of events extending across the globe that was responsible for the production of many types of sedimentary 0° basins (rift valleys and passive margins), significantly affecting the history of L life and influencing contemporary global environmental conditions (Figures 1.3, 1.4 and 1.5).
Anticline Iapetus Ocean Thrust Faults Tilted Stratigraphy 30° S Inversion B Basin Av Rheic Ocean 60° S
Figures 1.3, 1.4 and 1.5: Images from the Cantabrian Zone displaying the stratigraphy and structures from the origin, evolution and closure of the Rheic Ocean South Pole 2. Fieldwork Location: The Iberian Passive MarginG Cantabrian Zone West Austrain-Leonese Zone N 3. Aims: Central Iberian Zone Central Armorican Zone The research aims of this project are to analyse the rock sequences Ossa-Morena Zone Aramo Somiedo- Unit (stratigraphy), as well as the geometry and kinematics of extension faults North Armorican Zone Correcilla Picos de Europa South Portuguese Zone Unit Central Ponga within the Cantabrian Zone. Overall the main goals are to produce a 2D model Cornwall Zone Coal Nappe Basin of rock sequence development through time (chronostratigraphical Pisuerga reconstruction) and a 2D/3D structural plate tectonic model of the Rheic Ibero-Armorican Arc Carrion Unit Sobia-Badon Unit Ocean. N Esla Valsurvio 4. Data to be Collected: N S 30km
Iberian Fieldwork based investigations of the syn- Sedimentary logs of key syn-rift and Massif sedimentray response to the Rheic Ocean passive post-rift sequences margin will take place during 2010 and 2011 in Paleontological samples for Northwest Spain. The Cantabrian Region contains transitional rift zones 500km excellent time equivalent outcrops. Therefore, the Burial history samples - for a Figure 2.1: A map of the majority of research will be undertaken within this zircon/apatite fission track pilot study fieldwork area in Western zone (Figure 2.1). Structural orientation data for Europe (2) balanced cross-Sections and 20cm palaeogeographic reconstructions Figure 4.1: An image of a normal faults and (Figure 4.1) minor displacement 5. Preliminary Results:
30° N Burial History Analysis (Grid Ref: 277000, 4749236) Time (my) 550 523 496 469 442 415 388 361 334 307 280 pC Cambrian Ordovician Silurian Devonian Mississippian Penn Permian Age La La Ov Ba Hiatus 1 Fo La V SPHu Po B Ba Sa Em Formation 500 B Rift Phase 2 0 L Sa Em 500 Ar Ba Av Closure of the Rheic Ocean 1000 0° Hirnantian Glaciation Hu S Lu Thermal Subsidence 1500 The Iberian Passive Margin
2000 (m) Depth “Black Shale” La V 2500
Fo 3000 30° S Ov 3500 Development of the Rheic Ocean Development of the Rheno-Hercynian Ocean La Rift Phase1 Massive Transgression Foreland Basin Development4000 G Figure 5.1: A burial history diagram from the Southern region of Cantabria using Genesis software and ArcGIS 60° S Burial history analysis (Figure 5.1) shows the development of the Cantabrian region of Northwest Spain throughout the Palaeozoic (~500Ma to ~250Ma). The rifting of the Rheic Ocean took place during the Late Cambrian.(3)
Figure 1.2: A palaeogeographic map highlighting the location of the South Pole continents of Gondwana, Avalonia, Armorica, Baltica and Laurentia at 320Ma the time of the Rheic Ocean closure(1)
References: Collaboration and Sponsorship: 1)Robardet, M. 2003. The Armorica ‘microplate’: fact or fiction? Critical review of the concept and contradictory Professor Graham Williams and Dr Michael Montenari (Supervisors), University of palaeobiogeographical data. Palaeo, 195, pp. 125-148; 2) Veselovský, Z. 2004. Intergrated numerical modelling Keele, UK of a polyhistory basin, Southern Cantabrian Basin (Palaeozoic, NW-Spain). PhD Thesis, University of Ph.D. funded through NERC and ACORN Awards Heidelberg; 3) Marcos, A. Pérez-Estaún, A. Pulgar, J. A. Bastida, F. Aller, J. García-Alcalde, J. L. Sánchez de Fieldwork support from NERC and the Keel University Posada, L. C. 1980. Mapa Geológica de España 1:50,000. Institudo Geológico y Minero de España, Madrid, Hoja no. 76, 77, 101, 102 & 103. Lab support from Zetaware.inc