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Type section of the Bravaisberget Formation [Middle Triassic] at Bravaisberget, Western Nathorst Land, Spitsbergen, Svalbard
| Content Provider | Semantic Scholar |
|---|---|
| Author | Krajewski, Krzysztof P. Karcz, Paulina Woźny, Elzbieta Mørk, Atle |
| Copyright Year | 2007 |
| 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 litho− stratigraphical 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 Mork 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 sili− ceous 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 se− quence (unit 10) of the Somovbreen Mb. The base of the Van Keulenfjorden Mb is a discon− tinuity 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 se− quences. The Bravaisberget Fm records two consequent transgressive pulses that intro− duced 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 |
| File Format | PDF HTM / HTML |
| Volume Number | 28 |
| Alternate Webpage(s) | http://www.polish.polar.pan.pl/ppr28/PPR28-079.pdf |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
