New determinations of 40 Ar/ 39 Ar isotopic ages and flow volumes for Cenozoic volcanism in the Terror Rift, Ross Sea, Antarctica

This study provides new determinations of 40 Ar/ 39 Ar isotopic ages and flow volumes for submarine and subaerial Neogene volcanism developed within the Terror Rift, Ross Sea, Antarctica, the youngest segment of the West Antarctic Rift System. The study is based on the first dredged samples from seven seamounts north of Ross Island, as well as new data from Franklin and Beaufort Islands. The sampled foidite and basanitic lavas range in age from Quaternary (90 ± 66 ka) on a small seamount ∼10 km north of Franklin Island to 6.80 ± 0.05 Ma on Beaufort Island. These ages are consistent with ages of volcanism in both the Melbourne and Erebus Volcanic Provinces and significantly expand the documented area of Neogene magmatism in Victoria Land. There is no geographic progression of volcanism through time, but volcanism was voluminous in the Pliocene and particularly widespread during the Pleistocene. Two of the dredges sampled edifices comprised of less than 0.2 km 3 of volcanic materials. The largest seamount in the study area has 58.8 km 3 of volcanic material and represents growth over a period of several thousand years. Estimated minimum eruption rates range from 2 × 10 −4 km 3 y −1 to 2 × 10 −3 km 3 y −1 , consistent with rates proposed for other rift systems and nearby Mt. Erebus. Recent estimates of extension magnitude for the Terror Rift correspond to minimal decompression of only 0.10 to 0.22 GPa and therefore limited melt output of a typical peridotite source.