New Approach on the Extinction of Spreading at the Phoenix Ridge, Antarctica

Abstract

K-Ar ages have been determined for the submarine basalts dredged from the P2 and P3 segments of the Phoenix Ridge, Drake Passage, Antarctica, for better understanding on the extinction of seafloor spreading. At the P3 segment, the K-Ar ages of the rifted ridge basalts are 3.5-6.4 Ma, and those for the axial seamount basalts are 1.5-3.1 Ma. The K-Ar ages for the basalts at the rifted ridge and axial central high in the P2 segment are 2.1 and 1.4-1.9 Ma, respectively. We suggest that the extinction of seafloor spreading at the P3 and P2 segments occurred at 3.3 and 2.0 Ma, respectively, on the basis of ridge structure and formation time of basalts. This result favors the a stepwise extinction model rather than a simultaneous one on the extinction of the Phoenix Ridge.