Scotland Chalk nomenclature (Scottish Chalk Province) - Inner Hebrides Group: Beinn Iadain Mudstone Formation
Name
The Beinn Iadain Mudstone Formation was formally proposed by Braley (1990).
Type section
Beinn Iadain section A of Braley (1990) [NM 6917 5490] in Morvern.
Primary Reference Section
Allt na Teangaidh [NM 453 328] on Mull.
Formal subdivision
Considered by Braley (1990) to include the Feorlin Sandstone Member.
Lithology
Mudstone and siltstone, shaly and micaceous, red to purplish in colour but bleached white in places considered to be ‘argillized ash’ by Mortimore et al. (2001). Organic rich and sandy in lower part.
Definition of upper boundary
Disconformable at a sharp contact beneath Paleocene lavas.
Definition of lower boundary
Unconformable above an erosive contact with underlying conglomerates of the Clach Alasdair Conglomerate Member.
Thickness
2.5 m at Allt na Teangaidh on Mull, c.1.9 m at Feorlin tributary section [NM 5317 2225], 0.92 m at the type site on Beinn Iadain.
Distribution
Known from Morvern and the island of Mull.
Previous names
Considered by Braley (1990) to be equivalent to the ‘Upper Estuarine Series’ of Judd (1878).
Parent
Inner Hebrides Group.
Age and biostratigraphy
Upper Cretaceous or Paleocene.
References
Braley (1990); Lowden, Braley, Hurst and Lewis (1992); Mortimore, Wood and Gallois (2001).
In this volume a number of the correlations in the earlier works are adjusted and the dating of the sequence refined. The name is given Formational status in the sequences on Mull.