In geology

Geology

Geology is the science comprising the study of solid Earth, the rocks of which it is composed, and the processes by which it evolves. Geology gives insight into the history of the Earth, as it provides the primary evidence for plate tectonics, the evolutionary history of life, and past climates...

, the Inner Hebrides Group is a lithostratigraphical

Lithostratigraphy

Lithostratigraphy is a sub-discipline of stratigraphy, the geological science associated with the study of strata or rock layers. Major focuses include geochronology, comparative geology, and petrology...

 division containing a range of rocks mainly of Upper Cretaceous

Cretaceous

The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...

 age which occur around the west coast of the Scottish Highlands

Scottish Highlands

The Highlands is an historic region of Scotland. The area is sometimes referred to as the "Scottish Highlands". It was culturally distinguishable from the Lowlands from the later Middle Ages into the modern period, when Lowland Scots replaced Scottish Gaelic throughout most of the Lowlands...

. It comprises the following formations:

• Beinn Iadain Mudstone
  Mudstone
  Mudstone is a fine grained sedimentary rock whose original constituents were clays or muds. Grain size is up to 0.0625 mm with individual grains too small to be distinguished without a microscope. With increased pressure over time the platey clay minerals may become aligned, with the...
  
   Formation
• Strathaird Limestone
  Limestone
  Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate . Many limestones are composed from skeletal fragments of marine organisms such as coral or foraminifera....
  
   Formation
• Feorlin Sandstone
  Sandstone
  Sandstone is a sedimentary rock composed mainly of sand-sized minerals or rock grains.Most sandstone is composed of quartz and/or feldspar because these are the most common minerals in the Earth's crust. Like sand, sandstone may be any colour, but the most common colours are tan, brown, yellow,...
  
   Formation
• Griburn Chalk
  Chalk
  Chalk is a soft, white, porous sedimentary rock, a form of limestone composed of the mineral calcite. Calcite is calcium carbonate or CaCO3. It forms under reasonably deep marine conditions from the gradual accumulation of minute calcite plates shed from micro-organisms called coccolithophores....
  
   Formation
• Coire Riabhach Phosphatic Formation
• Lochaline White Sandstone Formation
• Morvern Greensand
  Greensand
  Greensand or Green sand is either 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 consist of a mixture of mixed-layer clay...
  
   Formation

The Clach Alasdair Conglomerate

Conglomerate (company)

A conglomerate is a combination of two or more corporations engaged in entirely different businesses that fall under one corporate structure , usually involving a parent company and several subsidiaries. Often, a conglomerate is a multi-industry company...

 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

Skye

Skye or the Isle of Skye is the largest and most northerly island in the Inner Hebrides of Scotland. The island's peninsulas radiate out from a mountainous centre dominated by the Cuillin hills...

, Eigg

Eigg

Eigg is one of the Small Isles, in the Scottish Inner Hebrides. It lies to the south of the Skye and to the north of the Ardnamurchan peninsula. Eigg is long from north to south, and east to west. With an area of , it is the second largest of the Small Isles after Rùm.-Geography:The main...

 and Mull

Isle of Mull

The Isle of Mull or simply Mull is the second largest island of the Inner Hebrides, off the west coast of Scotland in the council area of Argyll and Bute....

 and the adjacent Scottish mainland district of Morvern

Morvern

Morvern is a peninsula in south west Lochaber, on the west coast of Scotland. The name is derived from the Gaelic A' Mhorbhairne . The highest point is the summit of the Corbett Creach Bheinn which reaches in elevation....

. 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

British Geological Survey

The British Geological Survey 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 headquarters are in Keyworth, Nottinghamshire, but other centres...

 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

Paleogene

The Paleogene is a geologic period and system that began 65.5 ± 0.3 and ended 23.03 ± 0.05 million years ago and comprises the first part of the Cenozoic Era...

 age. The Group as a whole is the age equivalent of the Chalk Group of southern England

England

England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...

.