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 last of the three geologic eras of the Proterozoic geologic eon, eon, spanning from 1 billion to 538.8 million years ago, and is the last era of the Precambrian "supereon". It is preceded by the Mesoproterozoic era an ...

sedimentary rock Sedimentary rocks are types of rock (geology), rock formed by the cementation (geology), cementation of sediments—i.e. particles made of minerals (geological detritus) or organic matter (biological detritus)—that have been accumulated or de ...

s that outcrop across the Central Highlands of Scotland, east of the

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

. 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