Seismic Crustal Structure and Morphotectonic Features Associated With the Chain Fracture Zone and Their Role in the Evolution of the Equatorial Atlantic Region

Journal of Geophysical Research Solid Earth, vol. 125, pp. e2020JB020275

Abstract

Oceanic transform faults and fracture zones (FZs) represent major bathymetric features that keep the records of past and present strike-slip motion along conservative plate boundaries. Although they play an important role in ridge segmentation and evolution of the lithosphere, their structural characteristics, and their variation in space and time, are poorly understood. To address some of the unknowns, we conducted interdisciplinary geophysical studies in the equatorial Atlantic Ocean, the region where some of the most prominent transform discontinuities have been developing. Here we present the results of the data analysis in the vicinity of the Chain FZ, on the South American Plate. The crustal structure across the Chain FZ, at the contact between ∼10 and 24 Ma oceanic lithosphere, is sampled along seismic reflection and refraction profiles. We observe that the crustal thickness within and across the Chain FZ ranges from ∼4.6-5.9 km, which compares with the observations reported for slow-slipping transform discontinuities globally. We attribute this presence of close to normal oceanic crustal thickness within FZs to the mechanism of lateral dike propagation, previously considered to be valid only in fast-slipping environments. Furthermore, the combination of our results with other data sets enabled us to extend the observations to morphotectonic characteristics on a regional scale. Our broader view suggests that the formation of the transverse ridge is closely associated with a global plate reorientation that was also responsible for the propagation and for shaping lower-order Mid-Atlantic Ridge segmentation around the equator.

Authors 11

1. M. Marjanović corresponding

   Centre National de la Recherche Scientifique · Institut de physique du globe de Paris · Université Paris Cité

   Affiliation as printed

   Université de Paris, Institut de Physique du Globe de Paris, CNRS Paris France

2. Satish Chandra Singh

   Centre National de la Recherche Scientifique · Institut de physique du globe de Paris · Université Paris Cité

   Affiliation as printed

   Université de Paris, Institut de Physique du Globe de Paris, CNRS Paris France

3. Emma P. M. Gregory

   Centre National de la Recherche Scientifique · Institut de physique du globe de Paris · Université Paris Cité

   Affiliation as printed

   Université de Paris, Institut de Physique du Globe de Paris, CNRS Paris France

4. Ingo Grevemeyer

   GEOMAR Helmholtz Centre for Ocean Research Kiel

   Affiliation as printed

   GEOMAR Helmholtz Centre of Ocean Research Kiel, RD4—Marine Geodynamics Kiel Germany

5. Kevin Growe Aachen Applied Geophysics Program TU Delft

   ETH Zurich · RWTH Aachen University · Delft University of Technology

   Affiliation as printed

   Applied Geophysics Program TU Delft, ETH Zürich, RWTH Aachen Aachen Germany

6. Zhikai Wang

   Centre National de la Recherche Scientifique · Institut de physique du globe de Paris · Université Paris Cité

   Affiliation as printed

   Université de Paris, Institut de Physique du Globe de Paris, CNRS Paris France

7. Venkata Vaddineni

   Centre National de la Recherche Scientifique · Institut de physique du globe de Paris · Université Paris Cité

   Affiliation as printed

   Université de Paris, Institut de Physique du Globe de Paris, CNRS Paris France

8. Muriel Laurencin

   Centre National de la Recherche Scientifique · Institut de physique du globe de Paris · Université Paris Cité

   Affiliation as printed

   Université de Paris, Institut de Physique du Globe de Paris, CNRS Paris France

9. Hélène D. Carton

   Centre National de la Recherche Scientifique · Institut de physique du globe de Paris · Université Paris Cité

   Affiliation as printed

   Université de Paris, Institut de Physique du Globe de Paris, CNRS Paris France

10. Laura Gómez de la Peña

    GEOMAR Helmholtz Centre for Ocean Research Kiel

    Affiliation as printed

    GEOMAR Helmholtz Centre of Ocean Research Kiel, RD4—Marine Geodynamics Kiel Germany

11. Christian Filbrandt

    GEOMAR Helmholtz Centre for Ocean Research Kiel

    Affiliation as printed

    GEOMAR Helmholtz Centre of Ocean Research Kiel, RD4—Marine Geodynamics Kiel Germany