Sedimentological and Paleontological Analysis of Jurassic North Sea Deposits From Deltaic Environments

Nagy, Jenő; Dypvik, Henning; Bjærke, Tor

doi:10.1111/j.1747-5457.1984.tb00173.x

Cited by 20 publications

(2 citation statements)

References 3 publications

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“…The unit has been divided into five formations (Deegan & Scull, 1977), with the Broom Formation at the base, overlain successively by the Rannoch, Etive, Ness and Tarbert Formations. The Broom Formation is of problematical origin, being described variously as a mass-flow deposit (Parry, Whitley & Simpson, 1981), a transgressive sand (Gray & Barnes, 1981), a storm deposit (Chauvin & Valachi, 1980), a distributary mouth bar sand (Nagy, Dypvik & Bjaerke, 1984), a fluvial sand (Kirk, 1980) or, more broadly, an offshore sand sheet (Budding & Inglin, 1981). It consists of two facies, a coarse-grained arkosic sand No, of ions on the basis of 24 0 6.…”

Section: The Brent Sandstonesmentioning

confidence: 85%

A new approach to provenance studies: electron microprobe analysis of detrital garnets from Middle Jurassic sandstones of the northern North Sea

1985

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Reading provenance from heavy‐mineral suites is hampered by the depletion of diagnostic, but unstable, heavy minerals through intrastratal solution, a common phenomenon in deep sedimentary basins such as the North Sea. This paper demonstrates the potential of electron microprobe analysis in overcoming this problem, by concentrating on the compositional variations shown by detrital garnets, which are relatively resistant to intrastratal solution. Studies of the garnets from the Brent Group (Middle Jurassic) of the Murchison and Tern oilfields in the northern North Sea reveal that three distinct areas supplied detritus. Association 1 which characterizes the Broom Formation in both areas and recurs higher in the sequence in the Tern field, is ascribed to an Orkney‐Shetland source. The location of the areas supplying the garnets of Association 2, best represented in Murchison, and Association 3, common to both fields, is less clear. Their ultimate sources clearly include high‐grade metamorphics, and therefore probably lie on the Norwegian landmass, the Orkney‐Shetland Platform, or, conceivably, the Scottish landmass, but the possibility of recycling makes it difficult to judge their immediate provenances. Nevertheless, the presence of three garnet associations indicates that the most widely accepted model of Brent sedimentation, with sands derived from a domal uplift in the outer Moray Firth and channelled northward along the Viking Graben, is untenable.

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Section: The Brent Sandstonesmentioning

confidence: 85%

A new approach to provenance studies: electron microprobe analysis of detrital garnets from Middle Jurassic sandstones of the northern North Sea

1985

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“…Thus, the dominance of Ammobaculites, Bulbobaculites, Kutsevella and Haplophragmoides, as well as the low diversity (cf. Nagy et al 1984Nagy et al , 1990Nagy 1992) suggest that the uppermost Pliensbachian -Toarcian sediments at Anholt record progressive shallowing of the environment. The presence of a few ammonite fragments and some dinoflagellate cysts show that marine influence persisted.…”

Section: Palaeoenvironmentmentioning

confidence: 99%

The Lower–Middle Jurassic of the Anholt borehole: implications for the geological evolution of the eastern margin of the Danish Basin

et al. 2003

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This study of Upper Pliensbachian – Bajocian/Bathonian deposits in a borehole drilled on the island of Anholt, Denmark incorporates sedimentology, biostratigraphy (palynomorphs and foraminifera), palaeomagnetism and coal petrology. The studied succession records a gradual change from marine inner shelf storm-influenced clays to mainly terrestrial sands, clays, and lignite containing a flora of mainly freshwater algae and pollen. The regression was initiated at the Pliensbachian–Toarcian boundary and marine influence ceased during Bajocian–Bathonian times; the regression thus took place earlier at Anholt than in the centre of the Danish Basin. The sediments in the Anholt borehole are referred to the Fjerritslev and Haldager Sand Formations. Although the Lower–Middle Jurassic boundary is commonly placed at the boundary between the two formations, our data indicate that at Anholt the upper Fjerritslev Formation (member F-IV) is of Aalenian age. The Lower–Middle Jurassic boundary occurs close to the boundary between members F-III and F-IV of the Fjerritslev Formation. In contrast to other Lower–Middle Jurassic successions in the North Sea region, smectites of inferred volcanic origin are preserved in the Anholt section, suggesting limited burial and hence less intense diagenetic illitisation or chloritisation of smectites. A down-hole increase in diagenetic influence is reflected by the increase down-section both in the thermal stability of kaolinite and in the vitrinite reflectance. Kaolinite of inferred authigenic origin forms a white powder in the quartz-dominated sands of the Haldager Sand Formation; this kaolinite is thermally very unstable and is interpreted to be of late diagenetic, post-uplift origin. The vitrinite reflectance data indicate that the Jurassic formations have been exposed to thermal maturation corresponding to burial to a depth of 1000–1200 m below their present depth. Post-maturation uplift of the order of 1 km probably occurred partly during Late Cretaceous – Paleocene inversion in the Kattegat area and partly during Oligocene–Recent regional uplift, the latter being the most important of the two uplift phases. Palaeomagnetic data indicate that the main carrier of magnetic remanence is fine-grained magnetite. The stable remanence shows a pronounced inclination shallowing, which is attributed to post-depositional compaction.

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Facies Controlled Distribution of Foraminifera in the Jurassic North Sea Basin

Nagy

Pilskog²,

Wilhelmsen³

1990

Paleoecology, Biostratigraphy, Paleoceanography and Taxonomy of Agglutinated Foraminifera

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Sedimentological and Paleontological Analysis of Jurassic North Sea Deposits From Deltaic Environments

Cited by 20 publications

References 3 publications

A new approach to provenance studies: electron microprobe analysis of detrital garnets from Middle Jurassic sandstones of the northern North Sea

A new approach to provenance studies: electron microprobe analysis of detrital garnets from Middle Jurassic sandstones of the northern North Sea

The Lower–Middle Jurassic of the Anholt borehole: implications for the geological evolution of the eastern margin of the Danish Basin

Facies Controlled Distribution of Foraminifera in the Jurassic North Sea Basin

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