First marine cryptotephra in Antarctica found in sediments of the western Ross Sea correlates with englacial tephras and climate records

Abstract

We report the discovery of an important new cryptotephra within marine sediments close to Cape Hallett (northern Victoria Land), in the western Ross Sea, Antarctica. The cryptotephra is fully characterized for its texture, mineralogy and major- and trace-element data obtained on single glass shards. On the basis of geochemical composition, the cryptotephra is unequivocally correlated with the proximal deposits of an explosive eruption of the poorly known Mount Rittmann volcano, situated in northern Victoria Land. The cryptotephra is also correlated with a widespread tephra layer, which was erupted in 1254 C.E. and is present in numerous ice-cores and blue ice fields across East and West Antarctica. The characteristics of the tephra indicate that it was produced by a prolonged, moderate energy, mostly hydromagmatic eruption. This is the first time that a cryptotephra has been identified in marine sediments of the Ross Sea and in ice cores. It provides an important new and widespread stratigraphical datum with which the continental cryosphere and marine sedimentological records in Antarctica can be correlated. Moreover, from a purely volcanological point of view, the discovery further confirms the occurrence of a long-lasting, significant explosive eruption from Mount Rittmann in historical times that produced abundant widely dispersed fine ash. The study also highlights the inadequacy of current hazard assessments for poorly known volcanoes such as Mount Rittmann, located at high southern latitudes.

Volcanic Fluxes Over the Last Millennium as Recorded in the Gv7 Ice Core (Northern Victoria Land, Antarctica)

“…This age is consistent with the spike in nssSO 4 2− concentration at a depth of 183.07 m, where traces of volcanic materials (tephra) were visible to the naked eye. Such a tephra layer was already observed and accurately dated in ice [32,47] and marine cores [48] and was recently attributed to the eruption of Mount Rittmann that occurred in 1254, according to Narcisi et al [47], or in 1252 ± 2 according to Lee et al [49]. The complete list of the known volcanoes found in the nssSO 4 2− profile, their location, type, and altitude are reported in Table 1, while the nssSO 4 2− concentration throughout the whole ice core and the volcanic signatures are reported in Figure 2.…”

Resolving sea ice dynamics in the north-western Ross Sea during the last 2.6 ka: From seasonal to millennial timescales

“…seven half-lives according to Arias-Ortiz et al (2018)) and a tephra layer recently found in the Edisto inlet sediments (Fig. S1 and S5) (Mount Rittmann volcano eruption, (Di Roberto et al, 2019), which has been identified in the Talos Dome core (696 ± 2 yrs BP; ice record) (Narcisi et al, 2012), Taylor Dome core (709 ± 71 yrs BP; ice record) (Hawley et al, 2003) and West Antarctic Ice Sheet (WAIS) Divide cores (687 ± 7 yrs cal BP) (Di Roberto et al, 2019). For our final age-depth model, we used the more precise age assignment derived from the annually-counted portion of the WAIS Divide 2014 chronology.…”

Environmental and Oceanographic Conditions at the Continental Margin of the Central Basin, Northwestern Ross Sea (Antarctica) Since the Last Glacial Maximum

“…The glass compositions of BC04 cryptotephra match those of the 1254 C.E. (or 1252 ± 2) tephra from Mount Rittmann widespread in the marine sediments from Cape Hallett [31,57] and in the ice records of the entire West Antarctica [58,[68][69][70][71]. BC04 38-39 cryptotephra compositions also match very well with the composition of 11.1 ± 1.4 ka Aviator tephra (AVT tephra) found in the marine sediments of the Aviator Basin ( [60], and again derived from the Mount Rittmann.…”

“…These can be clearly distinguished from the pyroclastic products of the other volcanic complexes of North Victoria Land namely Mount Melbourne and the Pleiades volcanoes or from the products of the Mt Erebus volcano, which is located further south than the Central Basin. BC04 38-39 cryptotephra shares a geochemical affinity with several marine tephra and cryptotephra layers recently found interbedded in the Holocene-late Pleistocene sediments of the Ross Sea and in ice records [57,60,61]. The glass compositions of BC04 cryptotephra match those of the 1254 C.E.…”

“…The Glass composition of BC04 38-39 cryptotephra plot in the compositional field of phonolite to trachyte and overlap the compositions of the products of Mount Rittmann [57,58,60,67] (Figure 7c,d). These can be clearly distinguished from the pyroclastic products of the other volcanic complexes of North Victoria Land namely Mount Melbourne and the Pleiades volcanoes or from the products of the Mt Erebus volcano, which is located further south than the Central Basin.…”