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Basin evolution during the transition from continental rifting to subduction: Evidence from the lithofacies and modal petrology of the Jurassic Latady Group, Antarctic Peninsula

Willan, Robert C.R.; Hunter, Morag A.. 2005 Basin evolution during the transition from continental rifting to subduction: Evidence from the lithofacies and modal petrology of the Jurassic Latady Group, Antarctic Peninsula. Journal of South American Earth Sciences, 20 (3). 171-191. 10.1016/j.jsames.2005.05.008

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Abstract/Summary

The Jurassic Latady Basin (southern Antarctic Peninsula) developed in a broad rift zone associated with the early stages of Gondwana extension. Early Jurassic sedimentation (~185 Ma) occurred in small, isolated terrestrial to lacustrine rift basins in the present-day northwest and west and became shallow marine by the early Middle Jurassic. Quantitative modal analysis reveals a high proportion of mature, quartzose sandstone derived from cratonic and quartzose recycled-orogen provenances, most likely in the direction of the Ellsworth–Whitmore Mountains in the Gondwana interior. Sandstones with a more volcanolithic provenance probably represent an influx of sands from a Permian volcanic source in West Antarctica. The Early Jurassic Latady sequence contains abundant volcanic quartz and rhyodacite grains, locally derived from the nearby ignimbrites of the rift-related Mount Poster Formation (~185 Ma). Between the Middle and Late Jurassic (?160–150 Ma), there was a dramatic change throughout the Latady Basin to higher-energy conditions with marked lateral facies variations. Sandstones contain abundant fresh volcanic detritus and plot in the transitional arc field. Their source was a nearby, active continental margin arc, but there is no outcrop of arc material on the Antarctic Peninsula from this time. A possible source area is preserved on the Thurston Island block to the southwest. However, some fluvial systems still had access to areas of uplifted metamorphic/plutonic basement and quartzose, cratonic sources. Evidence of mixing of fluvial systems from different provenances and the lack of mixing of other fluvial systems suggest a complex topography of variably uplifted fault blocks with fluvial systems constrained in narrow valleys. The change from continental rift- to arc-related sources illustrates the shift from plume- (continental provenances) to continental margin arc-dominated tectonics. Thermal relaxation in the Late Jurassic led to the final phase of deposition in anoxic, deep-water conditions in a sediment-starved marine basin stretching from Ellsworth northward into southern South America.

Item Type: Publication - Article
Digital Object Identifier (DOI): 10.1016/j.jsames.2005.05.008
Programmes: BAS Programmes > Antarctic Science in the Global Context (2000-2005) > Antarctica in the Dynamic Global Plate System
ISSN: 0895-9811
Additional Keywords: Sedimentary basins, Detrital modes, Gondwana
NORA Subject Terms: Earth Sciences
Date made live: 17 Jan 2008 17:28
URI: http://nora.nerc.ac.uk/id/eprint/2048

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