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Abstract

The Trinity Peninsula Group (Permo-Triassic?) at Hope Bay, northern Antarctic Peninsula, is represented by the Hope Bay Formation, more than 1200 m thick. It is subdivided into three members: the Hut Cove Member (HBF,), more than 500 m thick (base unknown), is a generally unfossiliferous marine turbidite unit formed under anaerobic to dysaerobic conditions, with trace fossils only in its upper part; the Seal Point Member (HBF2), 170—200 m thick, is a marine turbidite unit formed under dysaerobic conditions, with trace fossils and allochthonous plant detritus; the Scar Hills Member (HBF3), more than 550 m thick (top unknown), is a predominantly sandstone unit rich in plant detritus, probably formed under deltaic conditions. The supply of clastic material was from northeastern sources. The Hope Bay Formation was folded prior to Middle Jurassic terrestrial plant-bearing beds (Mount Flora Formation), from which it is separated by angular unconformity. Acidic porphyritic dykes and sills cut through the Hope Bay Formation. They were probably feeders for terrestrial volcanics of the Kenney Glacier Formation (Lower Cretaceous) which unconformably covers the Mount Flora Formation. Andean-type diorite and gabbro plutons and dykes (Cretaceous) intrude the Hope Bay Formation, causing thermal alteration of its deposits in a zone up to several hundred metres thick. All the above units are displaced by two system of faults, an older longitudinal, and a younger transversal, of late Cretaceous or Tertiary age.

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Authors and Affiliations

Krzysztof Birkenmajer
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Abstract

This study is a detailed lithofacies analysis of the Wiar and Leszczyny members of the deep-marine Ropianka Formation (Campanian–Paleocene) exposed in the Hucisko Jawornickie section of the Skole Nappe, Polish Carpathian Flysch. The sedimentary succession (>400 m thick) represents a channelized lobe complex that prograded at the base of submarine slope. Seven sedimentary facies are recognized as a record of the principa modes of sediment deposition. Based on their stratigraphic grouping and grain-size trends, six facies associations are distinguished as representing specific sub-environments of the depositional system: distributary channels, channel-mouth lobes, channel levees, crevasses and interlobe basin plain with crevasse splays. The individual facies associations are characterized statistically and their internal facies organization is analysed by the method of embedded Markov chains to reveal the time pattern of depositional processes. The environmental changes indicated by the vertical succession of facies associations are attributed to the autogenic processes of the distributary channel shifting within an aggrading lobe area and the lateral switching of depositional lobes. Eustatic influences are likely, but difficult to ascertain with poor biostratigraphic data. The bulk basinward advance of the base-of-slope system was probably due to a pulse of the tectonic narrowing of the synclinal Skole Basin.

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Authors and Affiliations

Piotr Łapcik

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