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Tempo Valley Delta Complex - OverviewTyrone
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Summary Full report
Site Type: Inland exposure, Pit
Site Status:
Grid Reference: H398542, H302411
Rock Age: Quaternary
Rock Type: Diamict, Gravel, Sand
Other interest: No data, Ice retreat, deltas, meltwater channel, moraine, outwash

Summary of site:

A suite of glacial retreat deposits spread along the Tempo River valley from its headwaters near Glengesh to the area east of Lisbellaw to the south west is interpreted in this account. Details of the main deposits are described under their topographic names (Glengesh and Tattinweer, site 513; Lough Eyes, site 515; Tempo and Pubble, site 514; Uplands areas of the Fintona Hills, site 516).

The initial direction of flow of the ice sheet of the main glaciation was from north east to the south west, inferred from the direction indicated by the shape of the rogan moraines (ice shaped deposits) that underlie this landscape. As the climate improved, the ice blanketing the area began to fragment, particularly on the Fintona Hills to the north and possibly to the west of the valley. Ice in the northern end of the valley dammed a lake to its north at Tonyglaskan with its surface at about the 150 m contour although this lake could have been higher, possibly discharging for a period into the Ballinamallard Basin. There was also a lake at Dooneen with a delta and outwash deposits, possibly fed by stagnant and decaying local ice. A further outwash surface was present around Pubble Bridge, fed by meltwater and decaying confined ice to the east. The extensive moraine ridges in the Lough Eyes area probably formed at the same time but there are differences of expert opinion about which ice sheets deposited them. The first interpretation by Charlesworth in 1931 suggests that they were formed at the margins of ice sheets centred to the west whereas McCabe in 1969 pointed out that the bulk of the rocks in the moraines were Devonian Old Red Sandstones and must have been derived from the north. Later events were the incision of meltwater channels into these deposits followed by ice retreat or stagnation in the central, main Tempo/Clogher lowland. Following final melting the modern drainage system evolved accompanied by the development of a number of raised bogs.

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