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Discussion papers
https://doi.org/10.5194/se-2019-141
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/se-2019-141
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: research article 30 Sep 2019

Submitted as: research article | 30 Sep 2019

Review status
This discussion paper is a preprint. A revision of the manuscript is under review for the journal Solid Earth (SE).

Uncertainties in breakup markers along the Iberia-Newfoundland margins illustrated by new seismic data

Annabel Causer1, Lucía Pérez-Díaz1,2, Jürgen Adam1, and Graeme Eagles3 Annabel Causer et al.
  • 1Earth Sciences Department, Royal Holloway University of London, Egham, TW20 0EX, UK
  • 2Department of Earth Sciences, Oxford University, Oxford, OX1 3AN, UK
  • 3Alfred Wegener Institut, Helmholtz Zentrum für Polar und Meeresforschung, Bremerhaven, Germany

Abstract. Plate tectonic modellers often rely on the identification of break-up markers to reconstruct the early stages of continental separation. Along the Iberian-Newfoundland margin, so-called break-up markers include interpretations of old magnetic anomalies from the M-series, as well as the J-anomaly. These have been used as the basis for plate tectonic reconstructions on the belief that these anomalies pinpoint the location of first oceanic lithosphere. However, uncertainties in the location and interpretation of break-up markers, as well as the difficulty in dating them precisely, has led to plate models that differ in their depiction of the separation of Iberia and Newfoundland.

We use newly available seismic data from the Southern Newfoundland Basin (SNB) to assess the suitability of commonly used break-up markers along the Newfoundland margin for plate kinematic reconstructions. Our data shows that basement associated with the younger M-Series magnetic anomalies is comprised of exhumed mantle and magmatic additions, and most likely represents transitional domains and not true oceanic lithosphere. Because rifting propagated northward, we argue that M-series anomaly identifications further north, although in a region not imaged by our seismic, are also unlikely to be diagnostic of true oceanic crust beneath the SNB. Similarly, our data also allows us to show that the high amplitude of the J Anomaly is associated to a zone of exhumed mantle punctuated by significant volcanic additions, and at times characterised by interbedded volcanics and sediments. Magmatic activity in the SNB at a time coinciding with M4 (128 Ma), and the presence of SDR packages onlapping onto a basement fault suggest that, at this time, plate divergence was still being accommodated by tectonic faulting.

We illustrate the differences in the relative positions of Iberia and Newfoundland across published plate reconstructions and discuss how these are a direct consequence of the uncertainties introduced into the modelling procedure by the use of extended continental margin data (dubious magnetic anomaly identifications, breakup unconformity interpretations). We conclude that a different approach is needed for constraining plate kinematics of the Iberian plate pre M0 times.

Annabel Causer et al.
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Short summary
Here we discuss the validity of so-called break-up markers along the Newfoundland margin, challenging their perceived suitability for plate kinematic reconstructions of the southern North Atlantic. We do this on the basis of newly available seismic transects across the Southern Newfoundland Basin. Our new data contradicts current interpretations of the extent of oceanic lithosphere and illustrates the need for a different for constraining the plate kinematics of the Iberian plate pre M0 times.
Here we discuss the validity of so-called break-up markers along the Newfoundland margin,...
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