Birth and death of a triple junction: The example of the Bay of Biscay

The Bay of Biscay fossil triple junction separated three tectonic plates: North America, Europe and Iberia. It is defined by three pairs of conjugate margins: Armorican-North Iberian margins, the Goban Spur-Flemish Cap margins, and the West Iberia-Newfoundland margins. In this area, although it was proposed that steady-state spreading started in Aptian/Albian times and ceased around 80 Ma (Verhoef et al., 1986), the timing and opening directions during rifting and spreading remain uncertain. Indeed, oceanic magnetic isochrones are badly constrained. Moreover, exhumed mantle is exposed, so the Ocean-Continent Transition (OCT) of the three conjugate margins is difficult to localize (Boillot et al., 1988; Sibuet et al., 2007; Thinon, 1999; Tugend et al., 2015).  As a result, there is no consensus on kinematic reconstructions.

This work, in the context of my PhD thesis, is part of the ANR project “FirstMove”. It is based on a multidisciplinary approach using geological data (wells, dives) and geophysical data (seismic reflection, magnetic, gravity and bathymetry data). Notably, we integrate the Breogham seismic reflection profiles which cross the fossil spreading ridge. We aim to redefine, map and date the different rift domains (necking, hyperextended, exhumed mantle and oceanic domains), in order to better constraint the evolution of the Bay of Biscay triple junction. Indeed, the Iberia plate kinematic is a keystone to understand the global kinematic of the whole Atlantic-Tethys system.

 

Boillot, G., Winterer, E. L., & et al. (Eds.). (1988). Proceedings of the Ocean Drilling Program, 103 Scientific Results (Vol. 103). Ocean Drilling Program. https://doi.org/10.2973/odp.proc.sr.103.1988

Sibuet, J., Srivastava, S., & Manatschal, G. (2007). Exhumed mantle‐forming transitional crust in the Newfoundland‐Iberia rift and associated magnetic anomalies. Journal of Geophysical Research: Solid Earth, 112(B6), 2005JB003856. https://doi.org/10.1029/2005JB003856

Thinon, I. (1999). Structure profonde de la Marge Nord Gascogne et du Bassin Armoricain. Ifremer-IUEM, Brest, France.

Tugend, J., Manatschal, G., Kusznir, N. J., & Masini, E. (2015). Characterizing and identifying structural domains at rifted continental margins: application to the Bay of Biscay margins and its Western Pyrenean fossil remnants. Geological Society, London, Special Publications, 413(1), 171–203. https://doi.org/10.1144/SP413.3

Verhoef, J., Collette, B. J., Miles, P. R., Searle, R. C., Sibuet, J.-C., & Williams, C. A. (1986). Magnetic anomalies in the northeast Atlantic Ocean (35°-50° N). Marine Geophysical Researches, 8(1), 1–25. https://doi.org/10.1007/BF02424825