“Bottomsets” of the lava−fed delta of James Ross Island Volcanic Group, Ulu Peninsula, James Ross Island, Antarctica

Abstract

Sedimentological study of the three geographically separated outcrops of bottom− sets of a single lava−fed delta (Pliocene) in the James Ross Island (Antarctica) allows recogni− tion of six lithofacies. Deposits of traction currents, deposits of volcaniclastic debris flows and products of such flows transformations (both low− and high−density turbidity currents) and glacigenic deposits (subaqueous debris flows and traction/turbidity currents) were all recog− nised. Existence of submarine proglacial environment formed prior to formation of volcani− clastic deposits partly covering the subaqueous slopes of volcano is supposed. The principal role of mass flow processes was recognised and explained by relative steep slopes of the lava−fed delta. The distribution of lithofacies significantly differs in the individual outcrops. These variations in sedimentary succession and also in thickness of volcaniclastic deposits of "bottomsets" of the single lava fed delta suggest principal role of local conditions and paleogeography for development and preservation of this part of delta depositional system. Moreover proximal and distal setting can be followed and direct vs. more distant relation to over−riding lava−fed delta supposed. The sedimentary succession terminated by foresets of hyaloclastite breccia.

Seasonal hydrological and suspended sediment transport dynamics in proglacial streams, James Ross Island, Antarctica

“…Cretaceous strata present in Bohemian Stream catchment are generally made of conglomerates and pebbly to silty sandstones (Ineson et al, 1986;Olivero et al, 1986;Whitham et al, 2006), while fine-grained sandstones and mudstones are more common in Algal Stream catchment (Olivero et al, 1986;Pirrie, 1989;Crame et al, 1991). James Ross Island Volcanic Group rocks cropping out in the studied catchments are represented by hyaloclastite breccia, subaerial basalt caprocks, dolerite dykes (Košler et al, 2009); hyaloclastite tuffs, volcanic ash, lapillistone and volcaniclastic sandstones to conglomerates are associated with Bibby Hill and crop out in the upper part of Bohemian Stream catchment only (Nehyba and Nývlt, 2014;Mlčoch et al, 2016), while the interbedded siliciclastic to volcaniclastic siltstones, diamictites and conglomerates are associated with the Lachman Crags-Berry Hill volcaniclastic delta and they crop out only in the upper part of Algal Stream catchment (Nehyba and Nývlt, 2015;Mlčoch et al, 2016). Mendel Formation sediments cropping out in lower reaches of both catchments are locally made of clast-rich diamictites and tuffaceous laminated siltstones to fine sandstones (Nývlt et al, 2011).…”

Igneous seismic geomorphology of buried lava fields and coastal escarpments on the Vøring volcanic rifted margin

“…Inner Flows, Lava Delta, Landward Flows as labelled in Figures 1 and 2). In this scenario the Inner Flows represent an aggradational bottom-set consisting of volcaniclastic sediments mixed with pillow-basalt and massive sheet flows (e.g., Nehyba and Nyvlt, 2015). Lava Deltas are recognized by prograding internal architecture (e.g., Wright et al, 2012) whereas the Landward Flows form sheets of stacked subaerial lavas which transition into Lava Delta facies at the escarpment (e.g.…”

Geomorphology of Ulu Peninsula, James Ross Island, Antarctica

“…Morphologically prominent volcanic mesas (flattopped hills), such as the Lachman Crags and Johnson Mesa (see Figure 2 for locations), originated as a result of subglacial and subaqueous volcanic activity (Smellie et al, 2008(Smellie et al, , 2013. They are composed of steeply dipping foresets of hyaloclastite breccia covered by subaerial basalt topsets (Smellie, 2006), and in places, bottomset glacigenic strata (Hambrey et al, 2008;Nehyba & Nývlt, 2015). Weathered basalt cover produces large blockfields with metre-scale basalt boulders on the surface of the mesas (2013).…”