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Widespread active detachment faulting and core complex formation near 13° N on the Mid-Atlantic Ridge

Nature volume 442, pages 440–443 (2006)Cite this article

Abstract

Oceanic core complexes are massifs in which lower-crustal and upper-mantle rocks are exposed at the sea floor1,2,3. They form at mid-ocean ridges through slip on detachment faults rooted below the spreading axis2,3,4,5,6. To date, most studies of core complexes have been based on isolated inactive massifs that have spread away from ridge axes. Here we present a survey of the Mid-Atlantic Ridge near 13° N containing a segment in which a number of linked detachment faults extend for 75 km along one flank of the spreading axis. The detachment faults are apparently all currently active and at various stages of development. A field of extinct core complexes extends away from the axis for at least 100 km. Our observations reveal the topographic characteristics of actively forming core complexes and their evolution from initiation within the axial valley floor to maturity and eventual inactivity. Within the surrounding region there is a strong correlation between detachment fault morphology at the ridge axis and high rates of hydroacoustically recorded earthquake seismicity. Preliminary examination of seismicity and seafloor morphology farther north along the Mid-Atlantic Ridge suggests that active detachment faulting is occurring in many segments and that detachment faulting is more important in the generation of ocean crust at this slow-spreading ridge than previously suspected.

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Figure 1: Location map and bathymetry near 13° N on the MAR.
Figure 2: Bathymetry map of a well-explored, extinct core complex south of the Atlantis fracture zone on the MAR3.
Figure 3: Multibeam bathymetry showing detachment faults and core complexes in the 13° N segment.
Figure 4: Schematic three-dimensional oblique view of the evolution of a core complex by detachment faulting.

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Acknowledgements

We are grateful to the captain and crew of the RV Knorr (Leg 182, 2005). We are also grateful to P. Lemmond, H. Schouten and M. Tivey for their help in collecting the data at 13° N. We had fruitful discussions with R. Searle, H. Schouten, M. Tivey and R. Sohn. We also thank J. Goff for constructive comments on the manuscript. This work was supported by the National Science Foundation. This is an IPGP contribution.

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Authors and Affiliations

  1. Woods Hole Oceanographic Institution, Woods Hole, Massachusetts, 02543, USA

    Deborah K. Smith

  2. School of Earth Sciences, University of Leeds, Leeds, LS2 9JT, UK

    Johnson R. Cann

  3. CNRS, Marine Geosciences Group, IPGP Case 89, 75252, cedex 05, Paris, France

    Javier Escartín

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  1. Deborah K. Smith
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  3. Javier Escartín
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Correspondence to Deborah K. Smith.

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Smith, D., Cann, J. & Escartín, J. Widespread active detachment faulting and core complex formation near 13° N on the Mid-Atlantic Ridge. Nature 442, 440–443 (2006). https://doi.org/10.1038/nature04950

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