Geology of Greenland Survey Bulletin 188 - 2000
The structure of the Cretaceous-Palaeogene sedimentary-volcanic area of Svartenhuk Halvø, central West Greenland
Jørgen Gutzon Larsen and T. Christopher R. Pulvertaft
Frontispiece. View of the western margin of the flexure zone between Usuit Kuussuat and Ulissat where it emerges at the coast 4 km south-west of Ulissat. Faulted lavas of the Vaigat Formation cross-cut by c. E-W-trending dykes. The height of the cliff on the right is c. 300 m.
Svartenhuk Halvø is a peninsula lying at the northern end of the West Greenland Palaeogene volcanic province. In the downfaulted south-western part of the peninsula upper Paleocene basalts overlie Cretaceous - lower Paleocene sediments, whereas to the north-east the basalts lie directly on Precambrian basement.
This bulletin describes the structural pattern in the basin area. This is dominated by NW-SE-trending extensional faults with downthrow to the north-east. Also trending NW-SE are faulted monoclinal flexure zones that were probably generated by reactivation of deep basement faults. Both the extensional fault arrays and the flexure zones are offset at approximately E-W-trending transfer faults. The regional extension is believed to be related to the opening of Baffin Bay during the late Paleocene – Eocene.
- Colophon, contents, abstract, introduction, geological units
nr188_p01-19.pdf (pdf-file ~2.4 Mb)
- Basin development and the Cretaceous boundary fault system, Structures within the basin area
nr188_p20-31.pdf (pdf-file ~0.8 Mb)
- Origin of the structural pattern, Acknowledgement, References
nr188_p31-39.pdf (pdf-file ~0.8Mb)
- Plate1. Cross-sections of Svartenhuk Halvø, central West Greenland. Note that the colourless area in section E–F just north of the Cretaceous boundary fault consists of sediments of uncertain age.
nr188_Plate-1.pdf (pdf-file ~0.3 Mb)
- Download the entire bulletin nr188_p01-40.pdf (including Plate-1) (pdf-file ~3.9 Mb)
Larsen, J.G. & Pulvertaft, T.C.R. 2000: The structure of the Cretaceous?Palaeogene sedimentary-volcanic area of Svartenhuk Halvø, central West Greenland. Geology of Greenland Survey Bulletin 188, 40 pp.
Svartenhuk Halvø (?halvø? = peninsula) lies at the northern end of the exposed part of the Palaeogene volcanic province in central West Greenland. The peninsula is divided into two parts by a major NW?SE fault system, the Cretaceous boundary fault system. To the south-west lies a basinal area in which Cretaceous ? Paleocene sediments are overlain by upper Paleocene basalts, whereas north-east of the fault system there is an elevated area in which Precambrian crystalline basement is exposed and is overlain by basalts, with only a few isolated pockets of Paleocene sediments in depressions in the basement surface.
Subsidence and sedimentation began in Albian time with the deposition of deltaic sandstones and mudstones. In the Turonian ? early Campanian there was further subsidence and at least 1500 m of distal turbidites were deposited. During middle Campanian (?) ? early Paleocene time the area was unstable, and alternating phases of uplift, erosion and subsidence resulted in the removal of all Cretaceous sediments in the uplifted Precambrian area, and the development of discordances in the basin area.
Volcanism started in mid-Paleocene time in a subsiding marine environment, so that the earliest volcanic rocks are hyaloclastite breccias. Later volcanism was almost entirely subaerial. The volcanic rocks are divided into two formations: (1) the Vaigat Formation (lower), dominated by picritic and other olivine-rich tholeiitic basalts, with a significant contaminated unit at the base of the formation in the south-east; (2) the Svartenhuk Formation (upper), characterised by plagioclase-porphyritic and aphyric basalts. In the northern part of the area about 50 m of fluvio-lacustrine sediments, tuffs and hyaloclastite separate the two formations. Mafic dykes occur throughout the area and are most numerous within the area of exposed Vaigat Formation. Thick sills and sheets of dolerite occur in the vicinity of the Cretaceous boundary fault system and within the sediments in the eastern part of the area.
Extensional faulting and tilting occurred in the basin area, both prior to, during and after volcanism. Most extensional faults trend NW?SE and throw down to the north-east, so that the rotated fault blocks dip south-west. However, there is a great difference in the degree of faulting and tilting between the northern and southern parts of the area, with few faults and generally low dips in the north, and numerous faults and dips between 20° and 40° in the south. The increase in the degree of extension and fault activity occurs at WNW?ESE- to E?W-trending transfer faults. Some extensional faults are associated with flexure zones with relative uplift on the north-east side and dips up to 60° to south-west within the zones. The regional extensional vector that gave rise to the extensional faulting could lie in any direction between NE?SW, normal to the extensional faults, and E?W, parallel to the transfer faults. The regional setting of the area suggests that extension was NE?SW. The regional structural pattern resembles closely (in mirror image) a structural pattern that has been described from the north-east side of the Gulf of Suez.
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