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Factpages Norwegian Offshore Directorate
Factpages Norwegian Offshore Directorate
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23.12.2024 - 01:26
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RATTRAY FM

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  • General information
    General information
    Attribute Value
    Lithostrat. unit
    The lithostratigraphic unit's official name.
    RATTRAY FM
    NPDID lithostrat. unit
    Norwegian Offshore Directorate's unique id for lithostratigraphic units.
    206
    Level
    Indicates the lithostratigraphic unit's level. Legal values: GROUP, FORMATION, MEMBER.
    FORMATION
    Lithostrat. 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

     Name
    From Rattray Head on the coast of Scotland adjacent to the volcanic province.
    Well type section
    UK well 21/10-1 (BP) (Fig 1.23-26) ure from 2680 m (8792 ft) to 3422.3 m (11228 ft) below KB.
    Well reference section
    None at present but Howitt and others (1975, (Fig 1.1-2) . illustrate the nature of the formation in wells adjacent to the type well.
    Thickness
    742.3 m (2436 ft) in the type well but the base of the formation was not reached.
    Lithology
    In 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).
    Boundaries
    The 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.
    Distribution
    The 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.
    Age
    Present 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.

  • Wellbores penetrating
    Wellbores penetrating
    Wellbore name
    Wellbore completion date
    Top depth [m]
    Bottom depth [m]
    07.01.1982
    4162
    4300

  • Wellbores with cores
    Wellbores with cores
    Wellbore name
    Wellbore completion date
    Core length [m]