The BGS Lexicon of Named Rock Units — Result Details

Gribun Chalk Formation

Computer Code: GRIB Preferred Map Code: GbCk
Status Code: Full
Age range: Santonian Age (KS) — Campanian Age (KC)
Lithological Description: Silicified chalk. Reworked chalk and conglomerate as (?) debris flow. Flinty in part.
Definition of Lower Boundary: Unconformable on the Coire Riabhach Phosphatic Formation or the Lochaline White Sandstone Formation.
Definition of Upper Boundary: Unconformable with the Clach Alasdair Conglomerate Member of the Strathaird Limestone Formation or Beinn Iadain Mudstone Formation (basal Paleocene age).
Thickness: c.5m at Gribun, about 1m elsewhere.
Geographical Limits: Principally on the island of Mull and within the Morvern district.
Parent Unit: Inner Hebrides Group (IHEB)
Previous Name(s): Silicified Limestone With Flint (-1574)
Silicified Chalk (-941)
Chalk Of Morvern (-3444)
Gribun Chalk (-4687)
Chalk Of Mull - Morvern [Obsolete Name And Code: See IHEB And GRIB] (CHM)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Section  Gribun Stream Boulder, Isle of Mull. 
Type Section  The Gribun Boulder [NM 457 357], Isle of Mull. 
Reference Section  Clachandhu Boulders [NM 4550 3533, NM 4550 3531, NM 4550 3528], Isle of Mull. 
Reference Section  Allt na Teangaidh, near Gribun, Isle of Mull. 
Reference(s):
Braley, S M. 1990. The Sedimentology, Palaeoecology and Stratigraphy of Cretaceous Rocks in N.W. Scotland. Unpublished PhD Thesis CNAA, Polytechnic SouthWest (now University), Plymouth. 
Hancock, J M. 2000. The Gribun Formation: clues to the latest Cretaceous history of western Scotland. Scottish Journal of Geology, Vol.36, 137-141. 
Lowden, B, Braley, S, Hurst, A and Lewis, J, 1992. Sedimentological studies of the Cretaceous Lochaline Sandstone, NW Scotland. 159-162 in Parnell, J (editor), Basins on the Atlantic Seaboard: Petroleum Geology, Sedimentology and Basin Evolution. Geological Society of London Special Publication, No.62. 
Mortimore, R N, Wood, C J and Gallois, R W, 2001. British Upper Cretaceous Stratigraphy. Geological Conservation Review Series. No. 23. (Peterborough: Joint Nature Conservation Committee.) 
Scott. J F. 1928. General geology and physiography of Morvern, Argyll. Transactions of the Geological Society of Glasgow, Vol.18, 149-189. 
Judd, J W. 1878. The secondary rocks of Scotland. Third paper. The strata of the Western Coast and Islands. With a note on the foraminifera and other organisms in the Chalk of the Hebrides by T R Jones. Quarterly Journal of the Geological Society of London, Vol.34, 600-743. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
S043