Terrane |
Main rock units |
(1) Hebridean Terrane |
Archean and Lower Proterozoic gneiss overlain by undeformed sediments from the Upper Proterozoic (terrigenous red sandstones) and Cambrian to Middle Ordovician (shallow-water marine siliciclastics and limestones). |
(2) Northern Highlands Terrane |
Precambrian to Upper Ordovician and Silurian metamorphosed sediments and mafic to felsic igneous rocks. |
(3) Central Highlands (Grampian) Terrane |
Upper Proterozoic metasediments overlying gneiss. Based on metamorphic evidence, this terrane is known to have accreted to the previous two by the Early Silurian. |
(4) Midland Valley Terrane |
A series of small, discrete terranes faulted into one main region, or superterrane. The main basement is thought to be an ancient fore-arc region, covered by Upper Palaeozoic volcanics (tholeiitic and calc-alkaline), volcaniclastic sediments, mudstones, sandstones and carbonates. |
(5) Southern Uplands Terrane |
Lower–Middle Palaeozoic sediments including turbidites, mudstones, pillow lavas, chert and some ophiolite material, indicative of an open, spreading oceanic environment. |
(6) Leinster–Lakes Terrane |
Lower Palaeozoic marine siliciclastic sediments, mudstones and limestones, along with subduction-related calc-alkaline volcanics. |
(7) Monian Terrane |
Precambrian calc-alkaline volcanics, blueschists, sediments and mélange, representative of a Precambrian to Early Cambrian subduction zone. |
(8) Avalon–Midland Platform Terrane |
Cambrian–Ordovician sedimentary succession of shallow-water marine siliciclastics and limestones on a Precambrian basement, grading to terrigenous red beds and some mafic volcanics. |
(9) Lizard Terrane |
Middle–Upper Devonian ophiolite complex associated with metamorphosed igneous and sedimentary successions, overlying Ordovician quartzites. |