Late Miocene Asterozoans (Echinodermata) in the James Ross Island Volcanic Group

Abstract

Asterozoans (Echinodermata) of Late Miocene age (6.02 ± 0.12 Ma) are preserved as external moulds in water-lain tuffs of the James Ross Island Volcanic Group (JRIVG), James Ross Island, Antarctic Peninsula. The asterozoans are complete, and appear to represent specimens suffocated after having been pinioned by rapid sedimentation on the distal fringe of an erupting sub-aqueous tuff cone. Although the coarse nature of the host sediments has obliterated the fine morphological detail of the specimens, at least one suggests evidence of entrainment by a turbidity current. A second shows evidence of detachment of the distal tip of one of its arms. In addition to fossil discoveries from glaciomarine sediments, the volcanic tuffs of the JRIVG represent a new source of fossil data that can be used to interpret the ecology and environment of the Antarctic marine shelf biota during the Neogene.

Zeolite compositions as proxies for eruptive paleoenvironment

“…Here we report new geochemical data and results from our recent study of hyaloclastite breccias from James Ross Island, Antarctica (Figure 1). Field observations of the volcanic sequences on the island suggest that both submarine and subglacial eruptions occurred during the Neogene (<6.5 Ma [ Smellie , 1999; Williams et al , 2006] and unpublished data of the authors), although with a majority subglacial [ Smellie , 2006]. It is therefore an ideal place to make a comparative study of the influence of alteration environments on authigenic mineral compositions.…”

Late Miocene volcanic sequences in northern Victoria Land, Antarctica: products of glaciovolcanic eruptions under different thermal regimes

“…There is no evidence, as fossils or sediments, for marine conditions during the tuff cone eruptions (cf. Williams et al 2006;Nelson et al 2009). Although a marine setting cannot be disproven at present, at least for those tuff cones that crop out at low elevations close to and at present sea level, the generally minor modification of the landforms implies that in each case they were rapidly buried by other volcanic products before wave erosion was able to modify them (Cas et al 1989;Godchaux et al 1992;White 1996).…”

Taphonomy and sedimentology of an echinoderm obrution bed in the Lower Devonian Voorstehoek Formation (Bokkeveld Group, Cape Supergroup) of South Africa

“…The discovery of well-preserved ophiuroids in the fossil record is the result of catastrophic burial by obrution events (sensu Brett, 1990) where large pulses of sediment rapidly smother benthic communities, permanently shielding them from decay and scavengers and preventing the escape of mobile taxa (Brett and Baird, 1986;Speyer and Brett, 1991;Brett et al, 1997). Fossil ophiuroid beds have been described from the Ordovician to Cenozoic (Spencer, 1950;Aronson, 1989;Mikulas et al, 1995;Donovan et al, 1996;Radwanski, 2002;Kutscher and Villier, 2003;Salamon et al, 2003;Twitchett et al, 2005;Williams et al, 2006;Hunter et al, 2007;Shroat-Lewis, 2007;Zatoń et al, 2008;Martínez et al, 2010;Thuy, 2011;Rousseau and Nakrem, 2012;Thuy et al, 2013;Jagt et al, 2014). Aronson (1989) and references therein, relates the decline in the distribution of dense ophiuroid assemblages in the late Mesozoic and Cenozoic to the rise in durophagous and to an abrupt increase in bioturbation ("biological bulldozing") during the late Mesozoic.…”