The BGS Lexicon of Named Rock Units — Result Details

Ptarmigan Sandstone Member

Computer Code: PASA Preferred Map Code: notEntered
Status Code: Full, pending ratification
Age range: Kimmeridgian Age (JD) — Kimmeridgian Age (JD)
Lithological Description: Thinly bedded, pale to medium grey-brown, fine- to medium-grained, quartzose, variably dolomitic and moderately sorted sandstones. Interbedded dark grey mudstones present. Wire-line log responses are erratic.
Definition of Lower Boundary: The base is defined by a down-section change from sandstone with interbedded mudstone to dominantly mudstone (Kimmeridge Clay Formation). There is a change from the erratic wireline log responses to a more uniform response.
Definition of Upper Boundary: The top is defined by a down-section change from mudstone (Kimmeridge Clay Formation) to sandstone with interbedded mudstone. The boundary is marked by a down-section decrease in gamma-ray values and an increase in velocity.
Thickness: Up to c. 150 m.
Geographical Limits: The member is restricted to the area around the Magnus Field (Quadrant 211/12 in the northern part of the East Shetland Basin).
Parent Unit: Kimmeridge Clay Formation (KC)
Previous Name(s): none recorded or not applicable
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Section  North Sea well 211/12-5 between the depths 3261 and 3295 m below KB (Richards et al., 1993). 
Reference(s):
Richards, P C, Lott, G K, Johnson, H, Knox, R W O'B. and Riding, J B. 1993. 3. Jurassic of the Central and Northern North Sea. In: Knox, R W O'B and Cordey, W G. Lithostratigraphic nomenclature of the UK North Sea. [British Geological Survey, Nottingham] 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
none recorded or not applicable