The BGS Lexicon of Named Rock Units — Result Details

Dirk Sandstone Member

Computer Code: DKSA Preferred Map Code: notEntered
Status Code: Full, pending ratification
Age range: Tithonian Age (JI) — Berriasian Age (KR)
Lithological Description: Very fine to medium-grained, well sorted, well cemented, locally carbonaceous and weakly calcareous sandstones, interbedded with dark coloured, organic-rich mudstones typical of the Kimmeridge Clay.
Definition of Lower Boundary: The boundary is defined by the down-section decrease in the proportion of sandstone to mudstone and a down-section increase in gamma-ray values. A distinctly high gamma-ray mudstone unit separates the Dirk Sandstone Member from the Claymore Sandstone Member in the type section.
Definition of Upper Boundary: The top is marked by a downward change from mudstones to sandstones interbedded with mudstone, together with a decrease in average gamma values and an increase in velocity.
Thickness: Up to 28 m.
Geographical Limits: Known only in the Galley Field, Block 15/23.
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 15/23-2 between the depths 3900 and 3928.5 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