 | | Polltullyard: entrance passage in cherty facies of the Dartry Limestone. |
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| Site Type: | Cave, Sinkhole | | Site Status: | ASSI | | Council area: | Fermanagh & Omagh District Council | | Grid Reference: | H09443241 | | Bing maps: | 54.24087,-7.8558 | | Google maps: | 54.24087,-7.8558 | | Rocks |
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| Rock Age: | Quaternary, Carboniferous (Asbian, Holocene, Visean) | | Rock Name: | Dartry Limestone Formation, Knockmore Limestone Member | | Rock Type: | Limestone | | Interest |
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| Other interest: | rift, cave, clastic sediments, doline, sinkhole |
| Summary of site: |
| The entrance to Polltullyard is at the base of a large depression which leads on to a soil slope. This chute ends in a 20m passage of comfortable walking height but with a clinging mud floor. This section of the cave is developed in cherty limestone of the Dartry Formation. The passage ends at a 30m vertical shaft in the Knockmore Limestone Member, a rock prone to extensive vertical karst developments throughout the area. At the foot of this pitch the main stream enters the passage and flows into boulders where it disappears. A boulder slope on the downstream side enters a boulder-filled chamber after 25m. From here a 30m crawl relocates the stream, which promptly vanishes again into a narrow rift. | | On the upstream side, a 4m climb enters 200m of well developed but now abandoned phreatic (formed below the water table) passages, with the stream now flowing along a vadose (formed above the water table) ‘canyon’ cut into the base of the phreatic tube. The passage ends in another boulder chamber which narrows to an impenetrable cleft. | | Most of the boulders in the system are of locally derived Carboniferous gritstone. |
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