Inner Hebrides Group

In geology, the Inner Hebrides Group is a lithostratigraphical division containing a range of rocks mainly of Upper Cretaceous age which occur around the west coast of the Scottish Highlands. It comprises the following formations:

Inner Hebrides Group
Stratigraphic range: Cenomanian to Paleocene
Entrance to silica sand mine in Lochaline White Sandstone Formation
TypeGroup
Sub-unitsMorvern Greensand Formation, Lochaline White Sandstone Formation, Coire Riabhach Phosphatic Formation, Griburn Chalk Formation, Feorlin Sandstone Formation, Strathaird Limestone Formation, Beinn Iadain Mudstone Formation
UnderliesPaleocene lavas
Overliesunconformable
Thickness10-22m
Lithology
Primarysandstones
Othermudstones, limestones
Location
RegionInner Hebrides
CountryUnited Kingdom
ExtentMull, Eigg, Skye, Scalpay, Soay, Raasay and the Morvern peninsula

The Clach Alasdair Conglomerate Member and the Laig Gorge Sandstone & Limestone Members are rock units below formation level, assigned to the Strathaird Limestone Formation.

Each of these formations is of limited geographical extent, the Scottish Chalk Province being fragmented amongst the islands of Skye, Eigg and Mull and the adjacent Scottish mainland district of Morvern. Each of the rock units has gone by different names in the past - the succession outlined here is based on an interpretation by the British Geological Survey reflecting more recent survey and age analysis. It is likely that the youngest of these formations, the Beinn Iadain Mudstone Formation, is largely of Paleogene age. The Group as a whole is the age equivalent of the Chalk Group of southern England. [1]

References
  1. Hopson, P.M. 2005 A stratigraphical framework for the Upper Cretaceous Chalk of England and Scotland, with statements on the Chalk of Northern Ireland and the UK Offshore Sector. British Geological Survey Research Report RR/05/01 102pp ISBN 0-85272-517-5
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