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Mourne Plain Complex - Moore Lodge MoraineDown
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Summary Full report
Site Type: Inland exposure
Site Status:
District:
Grid Reference: J32873150
Rocks
Rock Age: Quaternary (Late Midlandian)
Interest
Other interest: No data, Glacial deposit, Glaciomarine deposit, Glaciotectonic, ice lobe, moraine ridge, outwash

Summary of site:

From Derryvogue Harbour to the Giant's Grave, a distance of around 3 km, a muted and breached ridge runs north and then swings north west. It is about 20 m high and up to 150 m wide. At Moore Lodge towards the southern end, a sand pit exposes the deposit and three distinct sedimentary units can be seen. The first consists of thin beds and lamination of sand which are persistent laterally but show clear evidence of contortion with folds up to a metre high. There are also minor faults, both normal and reverse.

Lying on top of this unit without break are bedded gravels totalling around a metre in thickness. They are also deformed but to a lesser degree than the sands below. The third unit follows without break and is a stack of diamict beds (rocks with grain sizes from clay to cobble, usually unsorted glacial debris) some with large rocks suspended in a finer groundmass, others of pebbles or cobbles in direct contact with each other. The finely bedded first unit appears to be a shallow water spread of sediment flowing in sheets from a moderately distant source to form flat, laterally persistent beds. The sediment supply appears to have been winnowed sand from a local glacier and the progressive coarsening towards the top suggests increasing proximity to the ice front. A push from the advancing glacier bulldozed and buckled the earlier, finer beds and created the moraine ridge partly from material riding up on its front. As the ice wasted with climatic improvement, it retreated westwards leaving the western flank of the ridge unsupported, resulting in the adjustment that created the minor faults. There are similar ridges either side of the Moore Lodge moraine and in all there are 14 of them, of varying character, spread across the Mourne Plain each representing a period of temporary standstill during the final stages of glacial retreat from the area.


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