A tuff cone erupted under frozen-bed ice (northern Victoria Land, Antarctica): linking glaciovolcanic and cosmogenic nuclide data for ice sheet reconstructions

Abstract

The remains of a small volcanic centre are preserved on a thin bedrock ridge at Harrow Peaks, northern Victoria Land, Antarctica. The outcrop is interpreted as a monogenetic tuff cone relict formed by a hydrovolcanic (phreatomagmatic) eruption of mafic magma at 642 ± 20 ka (by 40 Ar-39 Ar), corresponding to the peak of the Marine Isotope Stage 16 (MIS16) glacial. Although extensively dissected and strewn with glacial erratics, the outcrop shows no evidence for erosion by ice. From interpretation of the lithofacies and eruptive mechanisms, the weight of the evidence suggests that eruptions took place under a cold-based (frozen-bed) ice sheet. This is the first time that a tuff cone erupted under cold ice has been described. The most distinctive feature of the lithofacies is the dominance of massive lapilli tuff rich in fine ash matrix and abraded lapilli. The lack of stratification is probably due to repeated eruption through a conduit blasted through the ice covering the vent. The ice thickness is uncertain but it might have been as little as 100 m and the preserved tephra accumulated mainly as a crater (or ice conduit) infill. The remainder of the tuff cone edifice was probably deposited supraglacially and underwent destruction by ice advection and, particularly, collapse during a younger interglacial. Dating using 10 Be cosmogenic exposure of granitoid basement erratics indicates that the erratics are unrelated to the eruptive period. The 10 Be ages suggest that the volcanic outcrop was most recently exposed by ice decay at c. 20.8 ± 0.8 ka (MIS2) and the associated ice was thicker than at 642 ka and probably polythermal rather than cold-based, which is normally assumed for the period.

Mid-Holocene thinning of David Glacier, Antarctica: chronology and controls

“…Outlet (Reeves and Priestley glaciers) and valley glaciers (Tucker and Campbell glaciers) along the northern Victoria Land sector began thinning at ∼ 17 ka, and the majority of thinning ceased by ∼ 7.5 ka, broadly coincident with a linear rise in sea level and ocean temperatures throughout deglaciation (Baroni and Hall, 2004;Johnson et al, 2008;Smellie et al, 2018;Rhee et al, 2019). In contrast, outlet glaciers covering a large swath of the TAM from Southern Victoria Land to Southern TAM experienced episodic thinning during the early-mid Holocene, likely due to local topographic effects associated with marine ice sheet instability (Jones et al, 2015;Spector et al, 2017).…”

Mid-Holocene thinning of David Glacier, Antarctica: Chronology and Controls

“…Subsequent grounding line retreat north of Ross Island was achieved by ∼8.6 ka and a modern configuration established by ∼2-4 ka (Anderson et al, 2014;McKay et al, 2016). Outlet and valley glaciers along the Northern Victoria Land sector (Reeves, Priestley, and Tucker, Aviator, Campbell glaciers, respectively) began thinning at ∼17 ka and the majority of thinning ceased by ∼7.5 ka, broadly coincident with a linear rise in sea level and ocean temperatures throughout deglaciation (Baroni and Hall, 2004;Johnson et al, 2008;Smellie et al, 2018;Goehring et al, 2019;Rhee et al, 2019). In contrast, outlet glaciers covering a large swath of the TAM from Southern Victoria Land to Southern TAM, experienced episodic thinning during the early-mid Holocene, likely due to local topographic effects associated with Marine Ice Sheet Instability (MISI) (Jones et al, 2015;Spector et al, 2017).…”

Lithofacies and eruptive conditions of the southernmost volcanoes in the world (87° S)

“…they were erupted in association with an ice cover, and several have been used to provide information on glaciovolcanic eruptive and depositional processes and past glacial environments (e.g. Smellie et al 1993Smellie et al , 2009Smellie et al , 2011aSmellie et al , 2011bSmellie et al , 2014Smellie et al , 2018Skilling 1994;Smellie and Hole 1997;McIntosh 2000, 2002;Smellie 2001Smellie , 2006Smellie , 2008Iverson et al 2017). Most of the volcanism is associated with the West Antarctic Rift System (WARS), one of the world's largest intra-continental rifts (Fig.…”

“…In recent years, an increasing but still relatively small number of papers describing Antarctica's glaciovolcanoes has been published, both in a paleoenvironmental context and also to advance our understanding of glaciovolcanism and glaciovolcanic processes generally (e.g. Skilling 1994;McIntosh 2000, 2002;Smellie et al 2008Smellie et al , 2011aSmellie et al ,b, 2014Smellie et al , 2018. Many volcanic outcrops remain to be described.…”