Scotland Chalk nomenclature (Scottish Chalk Province) - Inner Hebrides Group: Morven Greensand Formation
Name
In older literature known as the Cenomanian Greensand, Greensand and Cenomanian Greensand Member. Designated the Morvern Greensand in Rawson et al. (1978) and given formation status in Braley (1990).
Type section
In Braley (1990) two sections given on Beinn Iadain as [NM 6917 5490 and NM 6965 5645] the former presumed to be the section described in Judd (1878) and Lee and Bailey (1925). Mortimore et al. (2001) give their locality as Beinn Iadain, Morvern [NM 670 541 to NM 689 528] and also a site called Beinn na H-Uamha at [NM 68].
Primary Reference Section
Loch Aline Borehole No. 10 [NM 6890 4695] and Auchnacraig Cliff [NM 7440 2989] in Braley (1990) and Alt na Teangaigh [NM 453 328], Isle of Mull, Mortimore et al. (2001).
Formal subdivision
None
Lithology
Glauconitic calcareous sandstone, white to pale greenish. Some gritty beds and calcareous inclusions up to cobble size. Conspicuously shelly (mainly oysters) in parts.
Definition of upper boundary
Conformable with the Lochaline White Sandstone Formation. However Braley (1990) and Lowden et al. (1992) regarded the Lochaline White Sandstone Formation as a member within this formation and considered the upper boundary as unconformable with the Gribun Chalk Formation.
Definition of lower boundary
Unconformable on various Jurassic and Triassic strata.
Thickness
0.3 to 13.4 m in Rawson et al. (1978).
Distribution
Known from the Morvern district and the Isle of Mull.
Previous/equivalent names
Greensand in the literature.
Cenomanian Greensand (map code of h or h5) as on Ardnamurchan 52W, Strontian 52E, Iona 43, Mull 44.
Glauconitic Sandstone (≡ Greensand) (map code of GSM or MorG) as on Staffa 43N, Ross of Mull 43S.
Greensand of Morvern obsolete Dic_Strat entry (code of GSM).
Morvern Greensand (h5) as on Eastern Mull 44W, Lismore 44E and in general informal use in the literature.
Parent
Inner Hebrides Group.
Age and biostratigraphy
Upper Cretaceous, Cenomanian
References
Rawson et al. (1978); Lee and Pringle (1932); Braley (1990); Lowden, Braley, Hurst and Lewis (1992); Mortimore, Wood and Gallois (2001).'