Earth Science Conservation Review
| Fallaghearn - site of local interest | Tyrone |
| Site Type: | Inland exposure, Pit |
| Site Status: | local interest |
| Council area: | Omagh District Council |
| Grid Reference: | H608628 |
| Google maps: | 54.51041,-7.0613 |
| Rocks | |
|---|---|
| Rock Age: | Quaternary |
| Rock Type: | Gravel, Sand |
| Interest | |
| Other interest: | Subaqueous outwash, flat-topped delta, meltwater channel, subaqueous fan, glacial |
Description:
This area around Fallaghearn is characterised by four flat delta surfaces dissected by 10-40m deep meltwater channels. The resulting isolated sand and gravel fragments are separated by steep-sided, deeply entrenched valleys and flat alluvial or peatland-dominated spreads. Delta surfaces occur between 233-235m O.D. There are exposures of delta sediments in a series of linked pits at Altagallagy [H608 682], 6km northwest of Ballygawley. A series of three large pits have developed in three dissected delta fragments. Linked pits extend to 1.5km long and 400m wide, covering a total area of 60ha. There is major exposure in the west and east pits.
The sediment sequences in the west pit record periodic flow pulses into a subaqueous depocentre. One face in this exposure is approximately perpendicular to flow input direction and shows relatively flat bedding structures, vertically offset bed stacking, shallow channelling and reactivation surfaces. This is characteristic of a shallow water, mid-fan environment dominated by processes regulated by the input of sediment pulses to the system. Sandy interbeds record periods of flow cessation. Exposure in the east pit is characterised by laterally continuous and stacked beds of well-sorted and stratified fine- to medium-grained sand with discontinuous pods and interbeds of matrix-supported granules and pebbles. There is little vertical or lateral variation in sand bed texture or sorting. The east pit records the subaqueous deposition of distal sediment sequences dominated by density and instability-driven processes, such as grainflow and massflow. This exposure is stratigraphically below the west pit and therefore illustrates the type of depositional environment that existed before major delta progradation.
The sediment sequences in the west pit record periodic flow pulses into a subaqueous depocentre. One face in this exposure is approximately perpendicular to flow input direction and shows relatively flat bedding structures, vertically offset bed stacking, shallow channelling and reactivation surfaces. This is characteristic of a shallow water, mid-fan environment dominated by processes regulated by the input of sediment pulses to the system. Sandy interbeds record periods of flow cessation. Exposure in the east pit is characterised by laterally continuous and stacked beds of well-sorted and stratified fine- to medium-grained sand with discontinuous pods and interbeds of matrix-supported granules and pebbles. There is little vertical or lateral variation in sand bed texture or sorting. The east pit records the subaqueous deposition of distal sediment sequences dominated by density and instability-driven processes, such as grainflow and massflow. This exposure is stratigraphically below the west pit and therefore illustrates the type of depositional environment that existed before major delta progradation.
| Enlander, I., Dempster, M. & Doughty, P., 2024. Fallaghearn - site of local interest, County Tyrone, site summary. [In] Earth Science Conservation Review. https://www.habitas.org.uk/escr/summary.php?item=727. Accessed on 2024-12-26 |
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