The Appin Group is a thick sequence of

metamorphosed Metamorphic rocks arise from the transformation of existing rock to new types of rock in a process called metamorphism. The original rock (protolith) is subjected to temperatures greater than and, often, elevated pressure of or more, causi ...

Neoproterozoic The Neoproterozoic Era is the unit of geologic time from 1 billion to 538.8 million years ago. It is the last era of the Precambrian Supereon and the Proterozoic Eon; it is subdivided into the Tonian, Cryogenian, and Ediacaran periods. It is ...

sedimentary rock Sedimentary rocks are types of rock that are formed by the accumulation or deposition of mineral or organic particles at Earth's surface, followed by cementation. Sedimentation is the collective name for processes that cause these particle ...

s that outcrop across the

Central Highlands of Scotland The Grampian Mountains (''Am Monadh'' in Gaelic) is one of the three major mountain ranges in Scotland, that together occupy about half of Scotland. The other two ranges are the Northwest Highlands and the Southern Uplands. The Grampian ran ...

, east of the

Great Glen The Great Glen ( gd, An Gleann Mòr ), also known as Glen Albyn (from the Gaelic "Glen of Scotland" ) or Glen More (from the Gaelic ), is a glen in Scotland running for from Inverness on the edge of Moray Firth, in an approximately straigh ...

. It forms a part of the Dalradian Supergroup. It is divided into three subgroups each consisting of multiple named formations. In stratigraphic order i.e. youngest at the top, these are: Blair Atholl Subgroup :Islay Limestone Formation :Mullach Dubh Phyllites Formation :Lismore Limestone Formation :Cuil Bay Slates Formation Ballachulish Subgroup :Appin Phyllite & Limestone Formation :Appin Quartzite Formation :Ballachulish Slate Formation :Ballachulish Limestone Formation Rock Strata in Glen Nevis

Lochaber Subgroup :Leven Schist Formation :Glencoe Quartzite Formation :Binnein Schist Formation :Binnein Quartzite Formation :Eilde Schist Formation :Eilde Quartzite Formation This whole succession reflects alternate periods of deepening and filling of the

sedimentary basin Sedimentary basins are region-scale depressions of the Earth's crust where subsidence has occurred and a thick sequence of sediments have accumulated to form a large three-dimensional body of sedimentary rock. They form when long-term subsidence ...

References

{{Reflist Geology of Scotland