The BGS Lexicon of Named Rock Units — Result Details

Holt Farm Group

Computer Code: HFM Preferred Map Code: notEntered
Status Code: Full, pending ratification
Age range: Frasnian Age (DR) — Famennian Age (DA)
Lithological Description: A limestone shale facies comprising a dark grey marine shale sequence. A grit and sandstone facies comprising pale whitish grey fine-grained sandstone and a calcareous sandstone shale facies comprising alternating thinly bedded dark grey fine-grained silty sand with fragmental limestone.
Definition of Lower Boundary: Drawn at the base of the calcareous sandstone shale facies where it rests conformably upon the lagoonal red beds of the Hopcroft Hall Group.
Definition of Upper Boundary: Drawn at the unconformity between the limestone shale facies of the Holt Farm Group with the overlying basalt igneous intrusion.
Thickness: 65m approx.
Geographical Limits: Steeple Aston, Oxfordshire.
Parent Unit: Not Entered (?)
Previous Name(s): none recorded or not applicable
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Area  Steeple Aston, Oxfordshire. 
Reference(s):
Poole E G. 1977. Stratigraphy of the Steeple Aston Borehole, Oxfordshire. Bulletin of the Geological Survey of Great Britain, Vol. 57, 1-85. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
none recorded or not applicable