Seismic, morphologic and scale variabilities of subsurface pipes and vent complexes in a magma-rich margin

Abstract

Subsurface pipes related to fluid flow are observed in seismic reflection data as vertical to sub-vertical features of low-amplitude reflections, linking chaotic reflections at the base (root zones) of volcanic constructs to their summits which can comprise craters, mounds or eye-shaped vents. To date, uncertainties remain regarding the linear correlation and scaling relationship between pipes and their overlying vent structures. Using 3D seismic reflection data from a magma-rich basin, the Vigrid Syncline in the Voring Basin (offshore Norway), this study provides a seismic, morphometric and statistical description of forty (40) pipes and their associated structures. These pipes include conical, bifurcated, fault-controlled and columnar types, which are a consequence of the intrusion of two mappable magmatic sills of Early Eocene age. The heights (av. 1098 m), widths (av. 1740 m) and slenderness ratios (i.e. the heights/widths (Ω)) of the pipes (av. 0.6) show low to moderate correlation coefficients with vent parameters such as height (av. 258 m), area (av. 2.3 km2) and ellipticity (av. 1.5). The morpho-statistical analyses provided here show that ‘pipe’ formation mechanisms are mutually exclusive and that vent geometries are not particularly systematic in nature.