Chapter 5.4a Marie Byrd Land and Ellsworth Land: volcanology

Abstract

Nineteen large (2348–4285 m above sea level) central polygenetic alkaline shield-like composite volcanoes and numerous smaller volcanoes in Marie Byrd Land (MBL) and western Ellsworth Land rise above the West Antarctic Ice Sheet (WAIS) and comprise the MBL Volcanic Group (MBLVG). Earliest MBLVG volcanism dates to the latest Eocene (36.6 Ma). Polygenetic volcanism began by the middle Miocene (13.4 Ma) and has continued into the Holocene without major interruptions, producing the central volcanoes with 24 large (2–10 km-diameter) summit calderas and abundant evidence for explosive eruptions in caldera-rim deposits. Rock lithofacies are dominated by basanite and trachyte/phonolite lava and breccia, deposited in both subaerial and ice-contact environments. The chronology of MBLVG volcanism is well constrained by 330 age analyses, including 52 new 40Ar/39Ar ages. A volcanic lithofacies record of glaciation provides evidence of local ice-cap glaciation at 29–27 Ma and of widespread WAIS glaciation by 9 Ma. Late Quaternary glaciovolcanic records document WAIS expansions that correlate to eustatic sea-level lowstands (MIS 16, 4 and 2): the WAIS was +500 m at 609 ka at coastal Mount Murphy, and +400 m at 64.7 ka, +400 m at 21.2 ka and +575 m at 17.5 ka at inland Mount Takahe.

Eruptive history of Mason Spur, a Miocene—Pleistocene polygenetic volcanic complex in southern Victoria Land, West Antarctic Rift System, Antarctica

“…Unlike most other volcanoes within the WARS (Smellie 2021; Wilch et al 2021), the stratigraphy at Mason Spur is dominated by clastic units, varying from ignimbrites, scoria, and agglutinate to sandstones and breccio-conglomerates, but lavas and intrusions are also locally prominent. The bulk of the outcrop is dominated by ignimbrite and breccia deposits and hypabyssal intrusions of MSP1.…”

“…Antarctica hosts one of Earth's largest intracontinental rift provinces, the West Antarctic Rift System (WARS), which contains numerous large polygenetic volcanoes (Wilch et al 2021; Fig. 1).…”

Introduction to volcanism in Antarctica: 200 million years of subduction, rifting and continental break-up

“…Renewed extension during the Cenozoic resulted in the creation of the WARS, a very large continental rift characterized by widespread alkaline volcanism (Fig. 1d-f) (Siddoway 2008;Smellie and Martin 2021;Smellie and Rocchi 2021;Wilch et al 2021). The rift contains numerous large and small volcanoes with basalt-trachyte, phonolite and rhyolite compositions (Martin et al 2021;Panter et al 2021b;Rocchi and Smellie 2021).…”

“…The mantle reservoir may have been emplaced as a large plume head, of late Cretaceous age or older, or lithosphere that has been metasomatized, or both sources exist (Panter 2021). Like alkaline volcanism in the Antarctic Peninsula, the volcanism in the WARS is also predominantly glaciovolcanic, and it has also provided uniquely important information on the development of the West and East Antarctic ice sheets (Smellie and Rocchi 2021;Wilch et al 2021).…”

“…The glaciovolcanic sequences contain a detailed record of the terrestrial Antarctic ice sheet going back to nearly 30 Ma and that record is now beginning to be tapped (e.g. Smellie et al 2009;Smellie and Edwards 2016;Wilch et al 2021). Despite these attributes, however, volcanism in Antarctica remains terra incognita to many Earth scientists, probably in large part because of its remoteness and inaccessibility.…”