Scotland Chalk nomenclature (Scottish Chalk Province) - Inner Hebrides Group: Gribun Chalk Formation: Difference between revisions

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=====Name=====
 
Name
 
 
 
The Gribun Chalk Formation was formally proposed by Braley (1990).
The Gribun Chalk Formation was formally proposed by Braley (1990).


 
=====''Type section''=====
 
 
 
 
 
''Type section''
 
 
 
The Gribun Boulder [NM 457 357] and Gribun Stream Boulder [NM 456 355], Isle of Mull.
The Gribun Boulder [NM 457 357] and Gribun Stream Boulder [NM 456 355], Isle of Mull.


 
=====''Primary Reference Section''=====
 
 
 
 
 
''Primary Reference Section''
 
 
 
Clachandhu Boulders [NM 4550 3533, NM 4550 3531, NM 4550 3528] and at Allt na Teangaidh [NM 453 328] near Gribun, Isle of Mull.
Clachandhu Boulders [NM 4550 3533, NM 4550 3531, NM 4550 3528] and at Allt na Teangaidh [NM 453 328] near Gribun, Isle of Mull.


 
=====Formal subdivision=====
 
 
 
 
 
Formal subdivision
 
 
 
None
None


 
=====Lithology=====
 
 
 
 
 
Lithology
 
 
 
Silicified Chalk. Reworked Chalk and conglomerate as (?) debris flow. Flinty in part.
Silicified Chalk. Reworked Chalk and conglomerate as (?) debris flow. Flinty in part.


 
=====Definition of upper boundary=====
 
 
 
 
 
Definition of upper boundary
 
 
 
Unconformable with the Clach Alasdair Conglomerate Member of the Strathaird Limestone Formation or Beinn Iadain Mudstone Formation (basal Paleocene age).
Unconformable with the Clach Alasdair Conglomerate Member of the Strathaird Limestone Formation or Beinn Iadain Mudstone Formation (basal Paleocene age).


 
=====Definition of lower boundary=====
 
 
 
 
 
Definition of lower boundary
 
 
 
Unconformable on the Coire Riabhach Phosphatic Formation or the Lochaline White Sandstone Formation.
Unconformable on the Coire Riabhach Phosphatic Formation or the Lochaline White Sandstone Formation.


 
=====Thickness======
 
 
 
 
 
Thickness
 
 
 
c. 5 m at Gribun, about 1 m elsewhere.
c. 5 m at Gribun, about 1 m elsewhere.


 
=====Distribution=====
 
 
 
 
 
Distribution
 
 
 
Principally on the island of Mull and within the Morvern district.
Principally on the island of Mull and within the Morvern district.


 
=====''Previous/equivalent names''=====
 
 
 
 
 
''Previous/equivalent names''
 
 
 
Silicified limestone with flint (Torosay) (h5’’’)(Senonian = Santonian to Maastrichtian) on Eastern Mull (44W and pt 44E) and Lismore (44E).
Silicified limestone with flint (Torosay) (h5’’’)(Senonian = Santonian to Maastrichtian) on Eastern Mull (44W and pt 44E) and Lismore (44E).


Silicified Chalk (≡ Gribun Chalk) on Staffa (43N).
Silicified Chalk (≡ Gribun Chalk) on Staffa (43N).


 
=====Chalk=====
 
Chalk
 
 
 
Senonian Chalk
Senonian Chalk


Gribun Chalk
Gribun Chalk


Chalk of Morvern, Judd  (1878).
Chalk of Morvern, Judd  (1878).


Silicified Chalk (Beinn Iadain), Scott (1928).
Silicified Chalk (Beinn Iadain), Scott (1928).


NOTE: - Hancock (2000), confusingly, utilised the term Gribun Formation or Gribun Conglomerate Formation to describe rocks above the Chalk (silicified Chalk) of? Santonian age which is the named Gribun Chalk Formation. This unit is probably equivalent to the Clach Alasdair Conglomerate Member of Mortimore, Woods and Gallois (2001).
NOTE: - Hancock (2000), confusingly, utilised the term Gribun Formation or Gribun Conglomerate Formation to describe rocks above the Chalk (silicified Chalk) of? Santonian age which is the named Gribun Chalk Formation. This unit is probably equivalent to the Clach Alasdair Conglomerate Member of Mortimore, Woods and Gallois (2001).


 
=====Parent=====
 
 
 
 
 
Parent
 
 
 
Inner Hebrides Group.
Inner Hebrides Group.


 
=====''Age and biostratigraphy ''=====
 
 
 
 
 
''Age and biostratigraphy ''
 
 
 
Upper Cretaceous, Cenomanian in Lowden et al, (1992); Santonian in Hancock, (2000); Santonian to Campanian in Mortimore et al., (2001).
Upper Cretaceous, Cenomanian in Lowden et al, (1992); Santonian in Hancock, (2000); Santonian to Campanian in Mortimore et al., (2001).


 
=====''References''=====
 
 
 
 
 
''References''
 
 
 
Braley (1990); Lowden, Braley, Hurst and Lewis (1992);  Mortimore, Wood and Gallois (2001).
Braley (1990); Lowden, Braley, Hurst and Lewis (1992);  Mortimore, Wood and Gallois (2001).


[[category:Scotland_Chalk_nomenclature_(Scottish_Chalk_Province)_-_Inner_Hebrides_Group | 04]]
[[category:Scotland_Chalk_nomenclature_(Scottish_Chalk_Province)_-_Inner_Hebrides_Group | 04]]

Revision as of 14:37, 6 February 2014

Name

The Gribun Chalk Formation was formally proposed by Braley (1990).

Type section

The Gribun Boulder [NM 457 357] and Gribun Stream Boulder [NM 456 355], Isle of Mull.

Primary Reference Section

Clachandhu Boulders [NM 4550 3533, NM 4550 3531, NM 4550 3528] and at Allt na Teangaidh [NM 453 328] near Gribun, Isle of Mull.

Formal subdivision

None

Lithology

Silicified Chalk. Reworked Chalk and conglomerate as (?) debris flow. Flinty in part.

Definition of upper boundary

Unconformable with the Clach Alasdair Conglomerate Member of the Strathaird Limestone Formation or Beinn Iadain Mudstone Formation (basal Paleocene age).

Definition of lower boundary

Unconformable on the Coire Riabhach Phosphatic Formation or the Lochaline White Sandstone Formation.

Thickness=

c. 5 m at Gribun, about 1 m elsewhere.

Distribution

Principally on the island of Mull and within the Morvern district.

Previous/equivalent names

Silicified limestone with flint (Torosay) (h5’’’)(Senonian = Santonian to Maastrichtian) on Eastern Mull (44W and pt 44E) and Lismore (44E).

Silicified Chalk (≡ Gribun Chalk) on Staffa (43N).

Chalk

Senonian Chalk

Gribun Chalk

Chalk of Morvern, Judd (1878).

Silicified Chalk (Beinn Iadain), Scott (1928).

NOTE: - Hancock (2000), confusingly, utilised the term Gribun Formation or Gribun Conglomerate Formation to describe rocks above the Chalk (silicified Chalk) of? Santonian age which is the named Gribun Chalk Formation. This unit is probably equivalent to the Clach Alasdair Conglomerate Member of Mortimore, Woods and Gallois (2001).

Parent

Inner Hebrides Group.

Age and biostratigraphy

Upper Cretaceous, Cenomanian in Lowden et al, (1992); Santonian in Hancock, (2000); Santonian to Campanian in Mortimore et al., (2001).

References

Braley (1990); Lowden, Braley, Hurst and Lewis (1992); Mortimore, Wood and Gallois (2001).

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