Geophysical evidence on the nature of the Hebrides Terrace Seamount

Abstract

Synopsis A magnetic and seismic reflection survey of the Hebrides Terrace Seamount (56°28′N., 10°17′W.) is supplemented by gravity data obtained by the Ministry of Defence (Hydrographic Office). The Seamount has a guyot-like morphology, and is supposed to be a volcanic feature. Seismic reflection profiles suggest that it ante-dates a succession of sediments on the continental slope to which a tentative Eocene–Recentage is assigned; and there are indications that its flat summit may represent an erosional bevel coeval with a (?Palaeocene) phase of erosion of the adjacent continental shelf margin. The associated magnetic anomaly is complex and cannot be simply modelled, but its general character is consistent with the presence of basic igneous rocks emplaced during an epoch of reversed polarity. The gravity profile is consistent with a model invoking a deep-rooted cylindrical core of density 3.0 gm cm −3 , flanked by pyroclastics and sediments of density 2.4 gm cm −3 . Thus the assembled data tend to confirm that the Seamount is an early Cenozoic volcanic feature.