Search results

Filters

  • Journals
  • Authors
  • Keywords
  • Date
  • Type

Search results

Number of results: 4
items per page: 25 50 75
Sort by:

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.
Go to article

Abstract

The Bravaisberget Formation in Spitsbergen embraces an organic carbon-rich, clastic sequence that reflects a general shallow shelf development of the Middle Triassic depositional system in Svalbard . New observations and measurements of the type section of the formation at Bravaisberget in western Nathorst Land allow to present detailed lithostratigraphical subdivision of the formation, and aid to reconstruct its depositional history. The subdivision of the formation ( 209 m thick at type section) into the Passhatten, Somovbreen, and Van Keulenfjorden members is sustained after Mørk et al. (1999), though with new position of the boundary between the Passhatten and Somovbreen mbs. The Passhatten Mb is defined to embrace the black shale-dominated sequence that forms the lower and middle parts of the formation ( 160 m thick). The Somovbreen Mb ( 20 m thick) is confined to the overlying, calcite-cemented sequence of marine sandstones. The Van Keulenfjorden Mb ( 29 m thick) forms the topmost part of the formation composed of siliceous and dolomitic sandstones. The formation is subdivided into twelve informal units, out of which eight is defined in the Passhatten Mb (units 1 to 8), two in the Somovbreen Mb (units 9 and 10), and also two in the Van Keulenfjorden Mb (units 11 and 12). Units 1, 3, 5, 7 and 9 contain noticeable to abundant phosphorite, and are interspaced by four black shale sequences (units 2, 4, 6, and 8). Unit 9 passes upwards gradually into the main sandstone sequence (unit 10) of the Somovbreen Mb. The base of the Van Keulenfjorden Mb is a discontinuity surface covered by thin phosphorite lag. The Van Keulenfjorden Mb consists of two superimposed sandstone units (units 11 and 12) that form indistinct coarsening-upward sequences. The Bravaisberget Fm records two consequent transgressive pulses that introduced high biological productivity conditions to the shelf basin. The Passhatten Mb shows pronounced repetition of sediment types resulting from interplay between organic-prone, fine-grained environments, and clastic bar environments that focused phosphogenesis. The lower part of the member (units 1 to 5) contains well-developed bar top sequences with abundant nodular phosphorite, which are under- and overlain by the bar side sequences grading into silt- to mud-shale. The upper part of the member (units 6 to 8) is dominated by mud-shale, showing the bar top to side sequence with recurrent phosphatic grainstones in its middle part. Maximum stagnation and deep-water conditions occurred during deposition of the topmost shale sequence (unit 8). Rapid shallowing trend terminated organic-rich environments of the Passhatten Mb, and was associated with enhanced phosphogenesis at base of the Somovbreen Mb (unit 9). Bioturbated sandstones of the Somovbreen Mb (unit 10) record progradation of shallow-marine clastic environments. The sequence of the Van Keulenfjorden Mb (units 11 and 12) was deposited in brackish environments reflecting closure of the Middle Triassic basin in western Svalbard .
Go to article

Abstract

The area of NW Wedel Jarlsberg Land south of Bellsund (Spitsbergen), between Dunderbukta in the west and the Berzeliustinden mountain group in the east, consists of five fault-bounded blocks: (1) the Renardbreen Block (Middle–Late Proterozoic basement rocks), (2) the Chamberlindalen Block (Late Proterozoic basement rocks), (3) the Martinfjella Block (Late Proterozoic through Early Ordovician basement rocks), (4) the Berzeliustinden Block (Late Proterozoic and Early Ordovician basement rocks covered by Late Palaeozoic–Tertiary platform deposits), (5) the Reinodden Block (Late Palaeozoic and Mesozoic rocks). The paper presents an outline of lithostratigraphy (Middle/Upper Proterozoic–Lower Ordovician: Hecla Hoek Succession) and architecture of the Caledonian basement in which several thrust-sheets and thrust-folds have been recognized. It also discusses some aspects of Tertiary overthrusting, faulting and rotation with affected the basement rocks and remodelled its Caledonian architecture.
Go to article

This page uses 'cookies'. Learn more