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Abstract

A mainly phonolitic, 10 km in diameter, cone-sheet complex crops out on the northern area of La Gomera. The swarm intrudes into the Basal Complex, The Old BasaIts and other rocks of the Trachytic-phonolitic Complex to which they belong. The cone-sheet complex center lies south of Vallehermoso. Most of the dykes in the care of the structure are "conic dome-sheets" which start to be evidenced 400m far from the center and dip over 50°. In the surrounding area the dome-sheets are less frequent while simple canesheets are more abundant and dip more gently towards the periphery. From the analysis of their dips and distribution a single conic structure is deduced. The cane-sheets were originally connected to a hypothetical dome-shaped magmatic body whose uppermost part is at present located 7350m under sea level.