Marie Byrd Land and Ellsworth Land: volcanology

• Main Authors: T.I. Wilch, W.C. McIntosh, K.S. Panter
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Geological Society of London 2021
• Subjects: Geology; FOS Earth and related environmental sciences; Antarctic; West Antarctic Ice Sheet; Byrd; Marie Byrd Land; Ellsworth Land; Takahe; Mount Takahe; Mount Murphy; Antarc*; Ice cap; Ice Sheet
• Online Access: https://dx.doi.org/10.6084/m9.figshare.c.5205362.v2; https://geolsoc.figshare.com/collections/Marie_Byrd_Land_and_Ellsworth_Land_I_Volcanology/5205362/2

Nineteen large (2348–4285 masl) 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 40 Ar/ 39 Ar 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.