RATTRAY FM
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General information
General information Attribute Value Lithostrat. unit The lithostratigraphic unit's official name.RATTRAY FMNPDID lithostrat. unit Norwegian Offshore Directorate's unique id for lithostratigraphic units.206Level Indicates the lithostratigraphic unit's level. Legal values: GROUP, FORMATION, MEMBER.FORMATIONLithostrat. unit, parent The parent lithostratigraphic unit's official name. See also level. Will be empty if Level = GROUP. -
Level below
Level below Lithostrat. unit -
Description
Rattray Formation
NameFrom Rattray Head on the coast of Scotland adjacent to the volcanic province.Well type sectionWell reference sectionNone at present but Howitt and others (1975, (Fig 1.1-2) . illustrate the nature of the formation in wells adjacent to the type well.Thickness742.3 m (2436 ft) in the type well but the base of the formation was not reached.LithologyIn the type section and adjacent wells (BP 21/9-1 and Shell/Esso 22/6-1), the formation consists of a thick series of basaltic lava flows (1 to 9 m thick where cored), with interbedded agglomerates, tuffs and tuffaceous sediments. The lavas are grey or purplish, vesicular and often partially altered, and locally completely laterised. Large fresh pyroxene phenocrysts and smaller altered olivine phenocrysts are set in a groundmass of pyroxene and feldspar. Autobrecciation, late hydrothermal activity and deep weathering and oxidation are fairly common. The epiclastics, ranging from agglomerate to tuffs, comprise lava and phenocryst clasts, or primary pumice and ? lapilli fragments. Only minor pyroclastics have been recognised. Interbedded sediments are present towards the base of the type section, consisting of dominantly red to brown mudstone, which is soft to firm and locally calcareous. Minor amounts of red-brown or grey-green siltstone and fine grained, friable, brown sandstone are present. Lateral lithological and petrographical variations have been described by Howitt and others (1975).BoundariesThe base of the formation generally rests on pre-Jurassic rocks and is marked by the incoming of igneous rocks. The upper boundary of the formation is normally a distinctive contact with Late Jurassic or Cretaceous rocks and is marked by clear changes of log character (Fig 1.23-26) ure.DistributionThe volcanic province extends from approximately 0° to 1°40’E and from 57°40’ to 58°45’ in the UK sector. Scattered occurrences of thin volcanic have been reported from the Norwegian sector but no details are available. The province appears to be controlled by faults at the junction of the Viking and Central grabens and the Moray Firth Basin. Both the amount of volcanic detritus and the percentage of lava decrease sharply along the south-eastern and western margins, with a more gradual change towards the north and east. The thickest sections of lavas and volcanic detritus pass into an outermost zone dominated by volcanic clastics with much interbedded non-volcanic sediment.AgePresent evidence indicates a Middle Jurassic age (Bajocian–Bathonian). In the southern part of the volcanic province the interbedded red-beds are barren, but sparsely fossiliferous grey beds in the north near the base and top of the formation yield Bajocian–Bathonian dates, based on floral dating and rare ostracods. Radiometric dating of whole-rock samples which are sheared, altered and often with secondary mineralization has provided a range of minimum ages from 165+/- 4 Ma (million years) to 109+/- 2 Ma. No systematic change in age has been recognized and the volcanic are assumed to be essentially the product of one synchronous episode.Source-
Deegan, C. E. and Scull, B. J. (compilers) 1977: A standard lithostratigraphic nomenclature for the Central and Northern North Sea. UK Institute of Geological Sciences, Report 77/25; the Norwegian Petroleum Directorate, NPD-Bulletin No. 1, 36 pp.
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Wellbores penetrating
Wellbores penetrating 07.01.198241624300 -
Wellbores with cores