Coarse‐grained submarine fan and slope apron deposits in a Cretaceous back‐arc basin, Antarctica

Abstract

The Cretaceous of west James Ross Island, Antarctica represents the proximal fill of a late Mesozoic backarc basin that was probably initiated by oblique extension during the early development of the Weddell Sea. The succession records sedimentation in two contrasting depositional systems: a laterally persistent slope apron flanking the faulted basin margin interrupted both spatially and temporally by coarse-grained submarine fans. Slope apron deposits are dominated by thinly interbedded turbiditic sandstones and mudstones (mudstone association), interspersed with non-channelized chaotic boulder beds, intraformational slump sheets and isolated exotic blocks representing a spectrum of mass-flow processes from debris flow to submarine gliding. Localized sand-rich sequences (sandstone-breccia association) represent sandy debris lobes at the mouths of active slope chutes. The submarine fan sediments (conglomerate association) are typified by coarse conglomerates and pebbly sandstones, intqrpreted as the deposits of high-density turbidity currents and non-cohesive debris flows. Three assemblages are recognized and are suggested to represent components of the inner channelled zone of coarse-grained submarine fans, from major fan channels through ephemeral, marginal channels or terraces to levee or interchannel environments.The occurrence of both slope apron and submarine fan depositional systems during the Early and Mid-Cretaceous is attributed to localized input of coarse arc-derived sediment along a tectonically active basin margin. Periods of extensive fan development were probably linked to regional tectonic uplift and rejuvenation of the arc source region; cyclicity within individual fan sequences is attributed to migration or switching of fan channels or canyons. Slope apron sedimentation was controlled largely by intrabasinal tectonics. Local unconformities and packets of amalgamated slide sheets and debris flow deposits probably reflect episodic movement on basin margin faults. Differential subsidence across the basin margin anchored the basin slope for at least 20 Myr and precluded basinward progradation of shallow marine environments. P R I N C E G U S T A V AMES ROSS Seymour Island Group (Tert.) Merambio Group (Upper Cret.-Tert.) 2 0 k m 5 8 Q W 5 7 ' W

Geodynamic evolution of the Antarctic Peninsula during Mesozoic times and its bearing on Weddell Sea history

“…However, major pulses of coarse sediment were deposited in the basin during Aptian-Albian times. These may reflect periodic uplift and rejuvenation of the arc (Ineson 1989) during this mid-Cretaceous deformation event. The break in the sedimentation record and major facies change in TuronianConiacian times (see above) may represent the final effects of this deformation in NE Graham Land.…”

“…In the Larsen Basin, in NE Graham Land (Macdonald et al 1988; Fig. 2c), sedimentation commenced with formation of thick submarine fan conglomerates of Hauterivian and Barremian age (135-124Ma) following an apparent hiatus in sedimentation from Late Berriasian-Valanginian times (c. 140Ma) (Thomson & Farquharson 1984;Ineson et al 1986). From AptianTuronian times (124-88Ma), sedimentation continued to be dominated by coarse clastic input in a deep submarine fan-slope apron complex (Ineson 1989).…”

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

“…Os conglomerados da Formação Lagreluis Point afloram a sudoeste da área estudada, entre a Baía Holluschickie e a Ilha Persson (Figura 1). A Formação Kotick Point é caracterizada por uma sequência de mais de 700 m de arenitos cinza escuros intercalados com lamitos e argilitos, sendo frequentes na sua porção mediana conglomerados e brechas, depósitos em um sistema de aprons e leques submarinos (Ineson, 1989). A Formação Whisky Bay, com uma espessura de até 950 m, mostra forte variação lateral de fácies e predomínio de ruditos depositados em ambiente de leques submarinos.…”

New Insights on theAristonectes parvidens(Plesiosauria, Elasmosauridae) Holotype: News on an Old Specimen

“…Esta unidad está cubierta por una megasecuencia regresiva depositada durante el intervalo Cretácico Inferior-Terciario inferior. Esta megasencuencia se divide en los grupos Gustav, Marambio y Seymour (Ineson, 1989;Rinaldi et al, 1978;Olivero, 2012). Rinaldi et al (1978) definieron el Grupo Marambio para los estratos cretácicos de la Isla Marambio que incluía a las formaciones López de Bertodano y Sobral.…”

“…Ineson (1989), al definir el Grupo Gustav, restringieron el Grupo Marambio a los "Snow Hill Island Series" de Bibby (1966). Además, restringieron la Formación López de Bertodano a la Isla Marambio, quedando sin nombre los estratos infrayascentes (unnamed strata).…”