Geophysical Mapping of Seamounts and Tectonic Elements over the Extinct Aegir Ridge

The Aegir Ridge was active in the northeastern Atlantic between Norway and Greenland from early Eocene (~55 Ma) until its cessation in late Oligocene (~26–24 Ma). The ridge remains understudied in the literature despite its importance in reconstructing tectonic history of the Northern Atlantic.  Although portions of the ridge axis are visible in modern bathymetric grids, much of its morphology is subdued by sedimentary cover. Numerous seamounts are evident near the former spreading axis, serving as key indicators of magmatic and tectonic processes. However, away from the ridge axis, the seamounts are buried beneath sediments and are therefore undetectable in bathymetry alone, necessitating an integrated geophysical approach to locate them.

In this study, we perform systematic mapping of seamounts across the extinct Aegir Ridge by integrating publicly available bathymetric, gravity and vintage seismic reflection datasets. While bathymetry reveals seamounts primarily near the spreading center, we utilize gravity data to identify buried or sediment-covered edifices away from the ridge. To do that, we enhance gravity data and determine the signal from known bathymetric seamounts. We then identify and map similar filtered anomaly responses as “gravity seamounts”.  To validate these features, we analyze seismic reflection profiles obtained from the GeoMap App. This allows us to confirm “seismic seamounts” where the structures rise above the basement but are covered by sediments. Due to limited seismic coverage, not all “gravity seamounts” can be validated. Therefore, we categorize seamounts into “bathymetric”, “gravity” and “seismic” ones and compare them with previously published bathymetric seamounts and igneous complexes.

We further analyze patterns in gravity and magnetic anomalies to delineate individual spreading segments of the extinct Aegir Ridge. Our analysis shows that most mapped seamounts align with the spreading center, while some display oblique orientations. These oblique seamounts correspond to offsets between ridge segments. In addition, magnetic anomalies exhibit characteristic distortions in the polarity reversals that are aligned with those oblique seamounts. These are characteristic of pseudofaults and propagator wakes, which form when two ridge segments compete with each other for magma supply. Our integrated geophysical mapping enables identification of previously unrecognized volcanic features and tectonic elements and suggests that ridge propagation occurred during the active lifespan of the Aegir Ridge.