Marine volcaniclastics of the Hidden Lake Formation (Coniacian) of James Ross Island, Antarctica: an enigmatic element in the history of a back-arc basin

Abstract

The Coniacian Hidden Lake Formation of James Ross Island, Antarctica is a 300-400m-thick succession of marine volcaniclastic conglomerates, sandstones and mudstones. It occurs at a point of transition in the evolution of the James Ross Basin, as it is underlain by deep-marine strata and overlain by shallow-marine strata. The succession reflects the two main factors controlling the deposition of the formation: (1) the influx of large quantities of volcaniclastic sediment; and (2) a pronounced inversion event in the early Coniacian heralding the cessation of transpressive tectonic activity in the James Ross Basin. The succession is dominated by a range of sediment density-flow deposits, which, combined with the limited faunas and the lack of wave-induced structures, suggest deposition in a relatively deep-marine environment below storm-wave base. Three main facies associations are recorded representing base-of-slope, fan-delta and basin-floor depositional environments. The volcaniclastic fan-delta association is dominated by fresh pyroclastic detritus and was deposited in response to volcanic eruptions on the adjacent arc. Thick beds of parallel-stratified sandstone record deposition from sustained, concentrated sediment density flows. The conditions immediately following pyroclastic eruptions lend themselves to the deposition of such deposits, as vegetation cover is destroyed and large amounts of poorly consolidated sediment are available for reworking. An enigmatic feature of the succession is the presence of units of cross-bedded sandstones thought to be of tidal origin that are locally abundant and are intimately interbedded with sediment density-flow deposits. The occurrence of tidal sediments in a substorm-wave base setting is explained by appealing to partial basin inversion during the final phases of strike-slip tectonic activity in the basin creating an irregular basin floor that focused and amplified tidal currents. The infilling of this basin topography by sediment and waning intrabasinal tectonism during the Coniacian resulted in the progressive elimination of this basin-floor topography and the onset of shallow-marine shelf sedimentation.

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

“…Bohemian and Algal Streams catchments (Figure 2) lie mostly on Cretaceous marine sediments of James Ross Basin (Del Valle et al, 1992) with upper reaches lying on Neogene volcanic rocks of James Ross Island Volcanic Group (Nelson, 1975;Smellie et al, 2013) and Mendel Formation sediments (Nývlt et al, 2011). 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).…”

Inferências paleoambientais a partir de análise de palinofácies da Formação Hidden Lake (Coniaciano, Cretáceo), Bacia Larsen, Ilha James Ross, Antártica

“…Uma feição comum é a presença de fragmentos de pomes achatados, lapilli acrescionais e bombas vulcânicas retrabalhadas, indicando atividade vulcânica explosiva contemporânea (Whitham et al, 2006).…”

“…Foram reconhecidas oito litofácies, baseadas na caracterização faciológica elaborada por Whitham et al (2006) na mesma região deste estudo.…”

“…Subordinadamente, ocorrem as litofácies F7 e, no perfil HL-2, as "camadas amarelas" (F8). A AF-1 no perfil HL-1 é associada aos leques deltaicos vulcanoclásticos definidos por Whitham et al (2006) para a base da Formação Hidden Lake, onde observa-se a ampla predominância de fluxos sedimentares densos ricos em detritos vulcanoclásticos (F3) derivados da intensa atividade piroclástica no arco, intercalados com as vaques seixosas e vaques (F2) derivadas de fluxos densos concentrados ou de correntes de turbidez de alta concentração. No perfil HL-2 observa-se a mesma sucessão F2-F3, entretanto, em estratos mais delgados do que em HL-1 e com uma maior frequência de F5 ao longo de toda a seção.…”

“…No perfil HL-1, intervalo semelhante ocorre entre 48,7 e 50 m, podendo ambos serem utilizados como datum de correlação entre os perfis. Estas litofácies estão relacionadas à associação de pavimento da bacia (sensu Whitham et al, 2006), em um ambiente marinho profundo com a migração de dunas de grande porte provavelmente através de correntes de maré, induzidas por altos e baixos topográficos na bacia, que podem ter amplificado as correntes. As camadas de vaques e vaques seixosas podem ter sido geradas através de fluxos gravitacionais a partir desses altos topográficos internos e/ou da borda da bacia.…”