The BGS Lexicon of Named Rock Units — Result Details

Chaigley Limestone Member

Computer Code: CHGL Preferred Map Code: Chgl
Status Code: Full
Age range: Arundian Substage (CJ) — Arundian Substage (CJ)
Lithological Description: Packstones and floatstones, bioclastic, mainly medium- to coarse-grained, dark grey, thin-to-medium-bedded, commonly graded and laminated. May show soft sediment deformation structures such as slump folds and convolute ripples. Many beds display erosive, tool-marked and fluted basal surfaces and some beds contain coarse-grained lags and mudstone lithoclasts. The interbedded mudstones are dark grey, fissile, pyritic and locally sideritic and mainly barren of macrofauna. Dark sandy ferruginous siltstones with plant debris also occur.
Definition of Lower Boundary: Taken at the first coarse-grained packstone that lies above a succession of thin-bedded, laminated, calcisiltites and mudstones of the Hodder Mudstone Formation (undifferentiated).
Definition of Upper Boundary: Packstones and floatstones of the Chaigley Limestone Member are overlain by slumped, blocky, calcareous mudstones of the Hodder Mudstone Formation (undifferentiated).
Thickness: To 180m
Geographical Limits: Restricted to the western part of the Craven Basin, including the Dinckley (SD 70 35) and Thornley (SD 62 40) anticlines, southern limb of the Plantation Farm Anticline (SD 66 43) and the northern limb of the Clitheroe Anticline (SD 75 45).
Parent Unit: Hodder Mudstone Formation (HOM)
Previous Name(s): none recorded or not applicable
Alternative Name(s): none recorded or not applicable
Stratotypes:
Partial Type Section  River Hodder, north bank, at Paper Mill Wood (SD 6790 3217), 1.65km westsouthwest of Bashall Eaves: Base of member exposed; exposure continues to the foot of a meander cliff on the west bank (SD 6800 4255), 0.65km downstream. Riley, 1990. 
Reference(s):
Riley N J. 1990. Stratigraphy of the Worston Shale Group (Dinantian) Craven Basin, north-west England. Proceedings of the Yorkshire Geological Society, Vol. 48, 163-187. 
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