geology Geology () is a branch of natural science concerned with Earth and other astronomical objects, the features or rocks of which it is composed, and the processes by which they change over time. Modern geology significantly overlaps all other Ear ...

, the Inner Hebrides Group is a lithostratigraphical division containing a range of rocks mainly of

Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the younger of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''creta'', the ...

age which occur around the west coast of the

Scottish Highlands The Highlands ( sco, the Hielands; gd, a’ Ghàidhealtachd , 'the place of the Gaels') is a historical region of Scotland. Culturally, the Highlands and the Lowlands diverged from the Late Middle Ages into the modern period, when Lowland Sco ...

. It comprises the following formations: * Beinn Iadain

Mudstone Mudstone, a type of mudrock, is a fine-grained sedimentary rock whose original constituents were clays or muds. Mudstone is distinguished from '' shale'' by its lack of fissility (parallel layering).Blatt, H., and R.J. Tracy, 1996, ''Petrology. ...

Formation * Strathaird

Limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms whe ...

Formation * Feorlin

Sandstone Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks. Most sandstone is composed of quartz or feldspar (both silicates) ...

Formation * Griburn

Chalk Chalk is a soft, white, porous, sedimentary carbonate rock. It is a form of limestone composed of the mineral calcite and originally formed deep under the sea by the compression of microscopic plankton that had settled to the sea floor. Chalk ...

Formation * Coire Riabhach

Phosphatic In chemistry, a phosphate is an anion, salt, functional group or ester derived from a phosphoric acid. It most commonly means orthophosphate, a derivative of orthophosphoric acid . The phosphate or orthophosphate ion is derived from phosphor ...

Formation * Lochaline White Sandstone Formation * Morvern

Greensand Greensand or green sand is a sand or sandstone which has a greenish color. This term is specifically applied to shallow marine sediment that contains noticeable quantities of rounded greenish grains. These grains are called ''glauconies'' and c ...

Formation 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 The Isle of Skye, or simply Skye (; gd, An t-Eilean Sgitheanach or ; sco, Isle o Skye), is the largest and northernmost of the major islands in the Inner Hebrides of Scotland. The island's peninsulas radiate from a mountainous hub dominated b ...

Eigg Eigg (; gd, Eige; sco, Eigg) is one of the Small Isles in the Scottish Inner Hebrides. It lies to the south of the Isle of Skye and to the north of the Ardnamurchan peninsula. Eigg is long from north to south, and east to west. With an a ...

and

Mull Mull may refer to: Places *Isle of Mull, a Scottish island in the Inner Hebrides **Sound of Mull, between the Isle of Mull and the rest of Scotland * Mount Mull, Antarctica *Mull Hill, Isle of Man * Mull, Arkansas, a place along Arkansas Highway ...

and the adjacent Scottish mainland district of

Morvern Morvern, historically also spelt Morven, is a peninsula and traditional district in the Highlands, on the west coast of Scotland. It lies south of the districts of Ardgour and Sunart, and is bounded on the north by Loch Sunart and Glen Tarbert, ...

. 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 The British Geological Survey (BGS) is a partly publicly funded body which aims to advance geoscientific knowledge of the United Kingdom landmass and its continental shelf by means of systematic surveying, monitoring and research. The BGS h ...

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 The Paleogene ( ; British English, also spelled Palaeogene or Palæogene; informally Lower Tertiary or Early Tertiary) is a geologic period, geologic period and system that spans 43 million years from the end of the Cretaceous Period million yea ...

age. The Group as a whole is the age equivalent of the

Chalk Group The Chalk Group (often just called the Chalk) is the lithostratigraphic unit (a certain number of rock strata) which contains the Upper Cretaceous limestone succession in southern and eastern England. The same or similar rock sequences occur acr ...

of southern

England England is a country that is part of the United Kingdom. It shares land borders with Wales to its west and Scotland to its north. The Irish Sea lies northwest and the Celtic Sea to the southwest. It is separated from continental Europe b ...

. 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

References

{{reflist Geology of Scotland