| Computer Code: |
TCSA |
Preferred Map Code: |
TS |
| Status Code: |
Full |
| Age range: |
Pliensbachian Age (JE)
— Pliensbachian Age (JE) |
| Lithological Description: |
Yellow-weathering silty very fine-grained sands, locally bioturbated and with hummocky cross-bedding. Impersistent 0.3m limestone in middle. At base 'Blue Band' - 1.8m of blue-grey mudstone - overlies Margaritatus Stone. At top 2.3m of grey mudstone occurs between the Thorncombiensis Bed and the Beacon Limestone Formation |
| Definition of Lower Boundary: |
Top of the Margaritatus Stone. |
| Definition of Upper Boundary: |
Base of Beacon Limestone Formation (formerly termed Junction Bed). |
| Thickness: |
23m |
| Geographical Limits: |
Southwest Dorset. Mapped on Sheet 327 (Bridport). Northern limit not yet proved. |
| Parent Unit: |
Dyrham Formation (DYS)
|
| Previous Name(s): |
Thorncombe Sands
(-563)
|
| Alternative Name(s): |
none recorded or not applicable
|
| Stratotypes: |
| Type Section |
Seacliffs between Seatown and Eype Mouth. Howarth, M K, 1957. |
| Reference(s): |
| Day, E C H, 1863. On the Middle and Upper Lias of the Dorsetshire Coast. Quarterly Journal of the Geological Society of London, Vol.19, 278-297. |
| Arkell, W J. 1933. The Jurassic System in Great Britain (Oxford: Clarendon Press.) |
| Howarth, M K, 1957. The Middle Lias of the Dorset coast. Quarterly Journal of the Geological Society of London, Vol.113, 185-204. |
| Buckman, S S. 1922. Jurassic Chronology: II - Preliminary studies. Certain Jurassic strata near Eypesmouth (Dorset): the Junction-Bed of Watton Cliff and associated rocks. Quarterly Journal of the Geological Society of London, Vol. 78, 378-436. |
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: |
|
E327
E341
E342
E343
|
