| Computer Code: |
PKSL |
Preferred Map Code: |
PkSL |
| Status Code: |
Full |
| Age range: |
Asbian Substage (CR)
— Brigantian Substage (CX) |
| Lithological Description: |
Packstones and wackestones predominate, interbedded with dark grey fissile and blocky mudstone. At the type locality, the lower 17 m comprises equal proportions of limestone and mudstone. The limestone is dark bluish grey, typically with sharp bases and flute and groove casts. The limestones form graded beds (8 to 70 cm thick), with medium-to coarse-grained packstone fining upwards to calcisiltite and argillaceous wackestone. The beds have an undulatory parallel lamination. The interbedded mudstones are cherty, calcareous and platy or fissile. Thin beds of bioclastic debris, mainly crinoid, brachiopod and coral fragments, occur in places. The upper 67 m has a proportion of 70 to 90% limestone to mudstone. The limestones are grey wackestones, locally weathering to pale brownish grey. Beds range from 8 cm to 80 cm thickness, with sharp, slightly undulatory bases and tops. Faint parallel lamination is visible in some beds. The interbedded mudstone is dark grey, calcareous, blocky and strongly bioturbated. |
| Definition of Lower Boundary: |
Taken at the base of the lowermost normal-graded packstone overlying a black mudstone-dominated succession of the Bowland Shale Formation (undifferentiated). |
| Definition of Upper Boundary: |
Taken at the top of the uppermost wackestone in a limestone-dominated succession, overlain by black mudstones and siltstones of the Bowland Shale Formation (undifferentiated). |
| Thickness: |
At the type locality the member is 84 m thick. |
| Geographical Limits: |
The member is mainly found in the Garstang district, located in the western part of the Craven Basin. |
| Parent Unit: |
Bowland Shale Formation (BSG)
|
| Previous Name(s): |
none recorded or not applicable
|
| Alternative Name(s): |
none recorded or not applicable
|
| Stratotypes: |
| Type Section |
Leagram Brook, near Park Style: full thickness of member at crop. Aitkenhead et al.,1992. |
| Reference(s): |
| Aitkenhead, N, Bridge, D M, Riley, N J, and Kimbell, S F. 1992. Geology of the country around Garstang. Memoir of the British Geological Survey, Sheet 67 (England and Wales) |
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: |
|
E067
|
