A subsided island west of Flores, Azores

Abstract

Investigation of a seamount 50 km west of Flores, in the Azores, has shown it to be a subsided island. This has been established by the fact that some of the cores recovered by a drill from the seamount at 450 m water depth were composed of subaerial basalt. The presence of Globoratalia truncatulinoides in some cores has dated them at less than 1.8 Ma. The basalt has been dated at 4.8 Ma. These facts give a subsidence rate faster than that of normal oceanic crust. The magnetic properties of the basalts have been measured and the results used in an attempt to calculate the anomaly of the seamount using its bathymetry. No calculated anomaly based on our models resembled the observed anomaly. The observed anomaly shows a linear trend typical of normal oceanic crust.