Lussa Bay
Geological Conservation Review site | GCR #2682 | Structural and Metamorphic Geology | Dalradian
Scotland's geosites are chosen because of their local, national or international importance. Take only photos, leave only footprints: avoid causing any damage to this site. You can walk almost anywhere in Scotland without the need to ask permission or keep to paths, but you have a responsibility to care for your own safety, to respect people's privacy and peace of mind and to cause no damage.
The right of access does not extend to quarries, building sites or any land where public access is prohibited, or to the collection of geological samples.
Summary
This site contains a relatively undeformed section showing the transition from the top of the shallow marine Jura Quartzite up into the deeper water Scarba Conglomerate (Islay to Easdale Subgroups, Argyll Dalradian). The Jura Quartzite contains numerous sedimentary structures, and it passes up into the conglomerate through a transition group consisting of slate and sandstone. Lussa Bay itself is eroded out of a thick band of black slate which can be seen to be abruptly replaced by thick, poorly-graded sands in a marked facies change. There are many good turbidite structures in these beds. Especially notable are the mass flow deposits of incompletely mixed mud, sand and gravel, frequently containing large disintegrating boulders of sandstone and shale. They represent disrupted, partly consolidated pebbly sand and mud which has flowed plastically down slope. However, these flows stopped before they could mix with water and develop into turbidity currents. This is an interesting site of great importance in any palaeoenvironmental reconstruction of the Dalradian basin, and also important for the boundary between two major lithostratigraphic units which it shows.
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