The BGS Lexicon of Named Rock Units — Result Details

Hillswick Formation

Computer Code: HIWK Preferred Map Code: notEntered
Status Code: Full
Age range: Tonian Period (AT) — Tonian Period (AT)
Lithological Description: Psammite; semipelite, locally pyritic; minor metaconglomerate.
Definition of Lower Boundary: Overlying Eastern Gneisses (EGNS) (equivalent of Lewisian Gneiss), presumbaly via a highly sheared unconformity.
Definition of Upper Boundary: Overlain by rocks of the Queyfirth Group (QYFH) (equivalent of Dalradian), separated by a shear zone (Virdibreck Shear Zone).
Thickness: Unknown: strongly deformed.
Geographical Limits: Shetland; NW Mainland, west of the Walls Boundary Fault.
Parent Unit: Sand Voe Group (SDVO)
Previous Name(s): none recorded or not applicable
Alternative Name(s): none recorded or not applicable
Stratotypes:
none recorded or not applicable
Reference(s):
Krabbendam, M. 2021. A stratigraphic framework for the early Neoproterozoic successions of the Northern Highlands of Scotland. UK Stratigraphic Framework Series. British Geological Survey Open Report, OR/21/072. 86pp. 
British Geological Survey. 2004. Northmaven, Scotland Sheet No. 129, 1:50,000 scale. 
Flinn, D. 1988. The Moine rocks of Shetland. In: Later Proterozoic Stratigraphy of the Northern Atlantic Regions, p. 74-85. Winchester, J A (editor). (Blackie.) 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
S129