Geomorphological and geophysical characterization of the MARNOK region (Mid-Atlantic Ridge north of the Kane Fracture Zone: 23°50′N-25°15′N)
Abstract
The MARNOK region of the Mid-Atlantic Ridge (23°50′N to 25°15′N), located north of the Kane transform fault, presents a valuable setting for investigating the interplay of magmatic and tectonic processes in oceanic lithosphere formation. This study integrates high-resolution bathymetric data, structural mapping, gravity anomalies (MBA and RMBA), and lithological observations from rock dredges and submersible Nautile dives to characterize accretionary styles across six ridge segments delineated by non-transform discontinuities. The region displays both orthogonal and oblique spreading geometries, enabling direct comparison between distinct accretion modes along a single ridge section.
Our results show that orthogonal segments (1 and 6), at the south and north terminations of the ridge section, are transitioning from a magmatically robust phase to a tectonic-dominated regime, as evidenced by the absence of active axial volcanic ridges, symmetrical fault patterns, along with crustal thinning near segment centers. In contrast, oblique segments (2-5) located in between the orthogonal segments are increasingly magmatic, characterized by robust axial volcanic ridges, a thickened crust, and highly negative gravity anomalies. Segment 2 illustrates a transitional case, where relict large-offset faulting and recent volcanism coexist, suggesting a recent shift from tectonic to magmatic dominance. V-shaped mantle Bouguer anomaly patterns and off-axis fault traces support the southward migration of the nontransform discontinuity at the boundary between segments 1 and 2, potentially driving the progressive narrowing of segment 1.
These findings illustrate the spatial and temporal variability of accretionary processes at slow-spreading ridges, controlled by fluctuations in magma supply, stress regime reorientation, transform fault influences, cooling and lithospheric heterogeneity. The MARNOK area thus provides critical insights into how spreading geometry and segmentation interact to govern the dynamic architecture of the oceanic lithosphere in a context of slow-spreading accretion.
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BibTeX
@article{rajeevan2026geomorphological,
title = {{Geomorphological and geophysical characterization of the MARNOK region (Mid-Atlantic Ridge north of the Kane Fracture Zone: 23°50′N-25°15′N)}},
author = {Remisha Rajeevan and Marcia Maia and Mathieu Rospabé and Ewan Pelleter and Florian Besson and Jean-Arthur Olive and Mélanie Principaud and Anne-Sophie Alix},
journal = {Marine Geology},
year = {2026},
month = may,
doi = {10.1016/j.margeo.2026.107821},
url = {https://hal.science/hal-05847804v1},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Geomorphological and geophysical characterization of the MARNOK region (Mid-Atlantic Ridge north of the Kane Fracture Zone: 23°50′N-25°15′N)
AU - Remisha Rajeevan
AU - Marcia Maia
AU - Mathieu Rospabé
AU - Ewan Pelleter
AU - Florian Besson
AU - Jean-Arthur Olive
AU - Mélanie Principaud
AU - Anne-Sophie Alix
PY - 2026
DA - 2026/05/30
JO - Marine Geology
DO - 10.1016/j.margeo.2026.107821
UR - https://hal.science/hal-05847804v1
AB - The MARNOK region of the Mid-Atlantic Ridge (23°50′N to 25°15′N), located north of the Kane transform fault, presents a valuable setting for investigating the interplay of magmatic and tectonic processes in oceanic lithosphere formation. This study integrates high-resolution bathymetric data, structural mapping, gravity anomalies (MBA and RMBA), and lithological observations from rock dredges and submersible Nautile dives to characterize accretionary styles across six ridge segments delineated by non-transform discontinuities. The region displays both orthogonal and oblique spreading geometries, enabling direct comparison between distinct accretion modes along a single ridge section. Our results show that orthogonal segments (1 and 6), at the south and north terminations of the ridge section, are transitioning from a magmatically robust phase to a tectonic-dominated regime, as evidenced by the absence of active axial volcanic ridges, symmetrical fault patterns, along with crustal thinning near segment centers. In contrast, oblique segments (2-5) located in between the orthogonal segments are increasingly magmatic, characterized by robust axial volcanic ridges, a thickened crust, and highly negative gravity anomalies. Segment 2 illustrates a transitional case, where relict large-offset faulting and recent volcanism coexist, suggesting a recent shift from tectonic to magmatic dominance. V-shaped mantle Bouguer anomaly patterns and off-axis fault traces support the southward migration of the nontransform discontinuity at the boundary between segments 1 and 2, potentially driving the progressive narrowing of segment 1. These findings illustrate the spatial and temporal variability of accretionary processes at slow-spreading ridges, controlled by fluctuations in magma supply, stress regime reorientation, transform fault influences, cooling and lithospheric heterogeneity. The MARNOK area thus provides critical insights into how spreading geometry and segmentation interact to govern the dynamic architecture of the oceanic lithosphere in a context of slow-spreading accretion.
SN - 0025-3227
ER -