K–Ar age of basalts from Great Meteor and Josephine seamounts (eastern North Atlantic)

Abstract

Six basalt samples from Josephine Seamount were dated by the K–Ar method. Their age ranged from 8 to 13 m.y. with increasing water depth. The Quaternary (and possibly Neogene) age of sediments overlying the basalt does not contradict those apparent ages.

Two basalt samples from the flank of the Great Meteor Seamount yielded ages of 11 and 16 m.y. Surf-rounded basalt pebbles with pocket-fillings of shallow-water limestone show that after the end of volcanic activity the basalt presently found at a water depth of about 600 m was only a few meters below sea level. Those data and assumptions about the age of underlying oceanic layer 2 (80 m.y.) allow inferences on the minimum volcanic production of Great Meteor Seamount (3.5 × 10⁵m³yr⁻¹). The volcanic activity of many eastern Atlantic seamounts ended about 10 m.y. ago.