• During the Carboniferous period, the Arran land mass was at a latitude of 8oN. The rocks of the carboniferous period found on Arran and predominantly sedimentary rocks. If we take the more recent  sub-divisions as listed in McKerrow and Atkins 1989, the Carboniferous rocks of Arran can be subdivided into the following groups from oldest to youngest. The Carboniferous rocks of Arran can be studied in detail at the coastal sections at Corrie and at Laggan, where they are exposed along with some interesting structural features. Within the various Carboniferous units abundant fossils can be found, including corals, brachiopods, bivalves, crinoids and plant fossils including root and stems, to list but a few.  Please do not hammer outcrops to collect fossils. Many fossils can be viewed in situ in outcrops and are best left there.

1. The Inverclyde Group (now including The Kinnesswood found at Hutton's Unconformity), sands and mudstones with cornstones.

2. The Strathclyde Group, sands and shales above basalts lavas and mudstones.

3. The Lower Limestone Group, sediments laid down in deltas and limestones, some of the members of this group ar highly fossiliferous (Images 1 , 2 and 3).

4. Limestone Coal Group, sediments laid down in deltas and coals.

5. Upper Limestone Group, deltaic sequences with limestones.

6. Passage Group, fluvial (river) laid sandstones and volcanic ashes.

7. Coal Measures, river sediments and sediments formed in deltas with forests, these rocks contain abundant fossilised plant remains, including fossil rootlets and fossil tree roots (stigmaria) (Images 3 and 4).

Image 1. A limestone bed at Laggan, a member of the Lower Limestone Group, containing abundant shells of the Brachiopod Gigantoproductus.

Image 2. A imestone outcrop at Laggan, a member of the Lower Limestone Group, containing abundant fossils including crinoids, spiriferids, fenestella and zaphrentids.

Image 3. A imestone outcrop at Laggan, a member of the Lower Limestone Group, containing abundant fossils including crinoids, spiriferids, fenestella and zaphrentids. The unit is fractured and calcite and sphalerite line the fractures.

Image 4. An outcrop of sandstone from the Carboniferous Coal Measures. It is exposed on the shore at Corrie and contains abundant fossilised rootlets.

Image 5. An outcrop of sandstone from the Carboniferous Coal Measures. It is exposed on the shore at Corrie and hosts a fossil tree root or stigmaria (to the right of the pencil)..

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This site was last updated Monday, 28 December 2009