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Earth Science Conservation Review
| Mourne Plain Complex - Tullyframe Pit | Down |
| Site number: | 443 | ||
| ESCC: | IS | ||
| Locality Type: | Pit | Status: | TBC |
| Grid Reference: | J32633168 Approximate | ||
| Google maps: | 54.21662,-5.96726 | ||
| County: | Down | Council area: | Newry, Mourne & Down District Council |
| Period: | Quaternary | ||
| Stages: | Late Midlandian | ||
| Site Description | |
|---|---|
| Description: | |
The Tullyframe pit is located on the northern face of the Cranfield moraine at the mouth of a valley to the west of Knockchree Mountain. The section measures 530m in length by 23m in depth, and occupies an area of 7.4ha. Four main facies are present. F1 Tabular sand and gravel Tabular beds of horizontally and cross-bedded sand and gravel (<1.5m thick) are massive and normally graded. The gravel varies from matrix supported to openwork. Sand facies show a well-marked overall coarsening up from silty sand with frequent discontinuous mud drapes over ripples, to laminated coarse sand with silt drapes. The top of the sequence consists of crudely-stratified, poorly sorted, largely clast-supported gravel interbedded with stringers of coarse sand. Beds thicken upwards to a maximum of ~30cm. Beds towards the top of the facies show an increasing frequency of isolated pebbles and cobble clusters. Occasional boulders (<0.9m) have variable a-axis orientations. Sediments underlying cobbles and boulders are deformed with high angle normal faults and displacements of 10cm. F2 Crudely stratified to massive diamict Crudely stratified matrix-supported diamict (<8m thick) directly overlies the sand and gravel of F1. The diamict is characterised by crudely-stratified, stacked beds (<60cm thick) demarcated by boulder lines and sandy partings. The facies contains less matrix and more markedly stratified with increasing distance from the ridge crest. Occasional channels are lined with boulders and cobbles. Dispersed boulders frequently have a vertical a-axis orientation. F3 Interbedded silt, clay and sand, with occasional gravel interbeds The upper surface of F2 forms a planar to undulating contact with overlying tabular beds of clay, silt and sand. The interbedded facies are between 1.0-3.2m thick and contain medium sand and silt couplets (frequently rippled), laminated mud, and rhythmically bedded silty sand and silt. Beds are <20cm thick. A mud bed contains delicate cross-laminations which have been disrupted into vertical pillar structures, and some mud beds contain small dish and pillar structures (<8cm across). The sand and silt has an undulating erosional contact with ca. 1.8m of stratified mud to pebble gravel. F4 Crudely stratified diamict A planar contact separates F3 from crudely stratified diamict (F4). The diamict (<3m thick) has a sandy matrix containing large isolated clasts, is crudely stratified and is both matrix to clast supported. Stratified gravel in the uppermost 2m of the section infills a channel (<10m wide). Chaotic matrix-to-clast supported gravel lenses are interbedded with the diamict. Isolated boulders and cobbles are frequent towards the top of the section. The uppermost meter of the diamict contains folded beds verging to the north. Fold amplitude is up to 1m, with fold frequency declining northward. INTERPRETATION The sediment sequences and facies architecture in the Tullyframe pit record periods of variable flow and sediment supply in a subaqueous, proglacial environment. F1 Tabular sand and gravel Cross-bedded gravel may result from discharges of varying energy into a body of standing water (Church & Gilbert, 1975). Sediment sorting and small clast size are the result of low energy underflow transport, while pods of open work gravel are generally deposited from higher energy pulses. Normal grading in F1 probably records turbulent flow, while inverse coarse tail grading is the result of dispersive pressures in higher density flows. Stacked, interbedded sediment sequences are typical of prograding outwash environments (Rust & Romanelli, 1975). Interbedded silt, sand and gravel records variable flow conditions, with ripples resulting from bottom flows draped by clay and silt settling out of suspension during periods of flow cessation. Poorly sorted gravel with sand interbeds are interpreted to represent cohesionless debris flows (Postma, 1986) and increased cobble sized clasts at the top of the sequence probably records increased berg rafting and rainout. F2 Crudely stratified to massive diamict The deposition of F2 is the result of a variety of processes, particularly suspension fallout, high density debris flows, and high density underflows. The preponderance of matrix support within the association is characteristic of debris flows (Middleton & Hampton, 1976). It is likely that boulder lines are the result of winnowing between flow events. Sand beds separating flows are the result of the deposition of finer material out of suspension. Bed-discordant boulder and cobble lines record winnowed scour surfaces. The vertical orientation of many boulders suggests deposition from floating ice (Domack & Lawson, 1985). F3 Interbedded silt, clay and sand, with occasional gravel interbeds The mud, silt and sand of F3 record reduced sediment supply and variable flow conditions in a subaqueous environment. Rhythmite formation is typical of proglacial lacustrine environments (Shaw, 1975), due to differential settlement of sediment from density underflows. Dish, pocket and pillar structures record water escape events through the sediment. Repeated fining-up sequences of sand and silt record cycles of suspension from turbid flows (Kuenen & Migliorini, 1950). Massive sand is a characteristic deposit of subaqueous outwash (Rust & Romanelli, 1975). Erosional contacts record local scouring as the sediments accumulated. F4 Crudely stratified diamict F4 is characterised by stacked beds of stratified diamict. Bad contacts, graduated contacts and lateral deformation all suggest that debris flow was the dominant depositional process (Middleton & Hampton, 1976). Chaotic, clast-rich clusters may be associated with flow noses, and are interpreted as recording plug formation in semi-mobile sediment gravity flows (Postma, 1986). Folded beds at the top of the section record slumping of saturated sediment. Stratified gravels within the diamict are the result of deposition in a channel. The limits of the water body recorded by the sediments at Tullyframe and Glenloughan are constrained by the altitude of the Cranfield moraine in the area at 90m O.D. The eastern lake margin was formed by the lower slopes of Knockchree Mountain, which rises to 305m O.D. The western limit was formed by the lower slopes of Rocky Mountain. The northern shoreline of the lake depends on the height of the ice above its frontal moraine, internal ice drainage, the time available for lake infilling and the time taken for lake drainage to be initiated. Valley ice in the White Water River valley was coincident with the Carlingford Lough ice lobe, and the moraine which records its furthest extent must be regarded as synchronous with the Cranfield moraine. In the absence of an obvious shoreline notch, probably reflecting the short life of the lake, it is inferred that the minimum likely area of the lake was ca. 1.2km2, based on the crest height of the Cranfield moraine, and the crest height (99m a.s.l) of the most distal valley ice moraine (at 326300 317800). | |
| Interpretation: | |
The sediment sequences and facies architecture in the Tullyframe pit record periods of variable flow and sediment supply in a subaqueous, proglacial environment. F1 Tabular sand and gravel Cross-bedded gravel may result from discharges of varying energy into a body of standing water (Church & Gilbert, 1975). Sediment sorting and small clast size are the result of low energy underflow transport, while pods of open work gravel are generally deposited from higher energy pulses. Normal grading in F1 probably records turbulent flow, while inverse coarse tail grading is the result of dispersive pressures in higher density flows. Stacked, interbedded sediment sequences are typical of prograding outwash environments (Rust & Romanelli, 1975). Interbedded silt, sand and gravel records variable flow conditions, with ripples resulting from bottom flows draped by clay and silt settling out of suspension during periods of flow cessation. Poorly sorted gravel with sand interbeds are interpreted to represent cohesionless debris flows (Postma, 1986) and increased cobble sized clasts at the top of the sequence probably records increased berg rafting and rainout. F2 Crudely stratified to massive diamict The deposition of F2 is the result of a variety of processes, particularly suspension fallout, high density debris flows, and high density underflows. The preponderance of matrix support within the association is characteristic of debris flows (Middleton & Hampton, 1976). It is likely that boulder lines are the result of winnowing between flow events. Sand beds separating flows are the result of the deposition of finer material out of suspension. Bed-discordant boulder and cobble lines record winnowed scour surfaces. The vertical orientation of many boulders suggests deposition from floating ice (Domack & Lawson, 1985). F3 Interbedded silt, clay and sand, with occasional gravel interbeds The mud, silt and sand of F3 record reduced sediment supply and variable flow conditions in a subaqueous environment. Rhythmite formation is typical of proglacial lacustrine environments (Shaw, 1975), due to differential settlement of sediment from density underflows. Dish, pocket and pillar structures record water escape events through the sediment. Repeated fining-up sequences of sand and silt record cycles of suspension from turbid flows (Kuenen & Migliorini, 1950). Massive sand is a characteristic deposit of subaqueous outwash (Rust & Romanelli, 1975). Erosional contacts record local scouring as the sediments accumulated. F4 Crudely stratified diamict F4 is characterised by stacked beds of stratified diamict. Bad contacts, graduated contacts and lateral deformation all suggest that debris flow was the dominant depositional process (Middleton & Hampton, 1976). Chaotic, clast-rich clusters may be associated with flow noses, and are interpreted as recording plug formation in semi-mobile sediment gravity flows (Postma, 1986). Folded beds at the top of the section record slumping of saturated sediment. Stratified gravels within the diamict are the result of deposition in a channel. The limits of the water body recorded by the sediments at Tullyframe and Glenloughan are constrained by the altitude of the Cranfield moraine in the area at 90m O.D. The eastern lake margin was formed by the lower slopes of Knockchree Mountain, which rises to 305m O.D. The western limit was formed by the lower slopes of Rocky Mountain. The northern shoreline of the lake depends on the height of the ice above its frontal moraine, internal ice drainage, the time available for lake infilling and the time taken for lake drainage to be initiated. Valley ice in the White Water River valley was coincident with the Carlingford Lough ice lobe, and the moraine which records its furthest extent must be regarded as synchronous with the Cranfield moraine. In the absence of an obvious shoreline notch, probably reflecting the short life of the lake, it is inferred that the minimum likely area of the lake was ca. 1.2km2, based on the crest height of the Cranfield moraine, and the crest height (99m a.s.l) of the most distal valley ice moraine (at 326300 317800). | |
| Notes: | |
For site specific information on other sand and gravel sites within the Mourne Plain Complex see the following sites: Key Site 441 - Cranfield Moraine Key Site 442 - Glenloughan Pit Key Site 444 - Moore Lodge Moraine Key Site 445 - Sandpiper Pit Key Site 446 - Kilkeel Cliff For overview information and references on the Mourne Plain Complex see the following site: Key Site 440 - Mourne Plain Complex - Overview For overview and site specific information on other sand and gravel sites within the Mourne Mountains area see the following sites: Key Site 447 - Attical Complex, Mourne Mountains - Overview Key Site 448 - Bloody Bridge River Valley Complex, Mourne Mountains - Overview Key Site 449 - Northeast Mournes Complex - Overview Key Site 450 - Western Mournes - Overview Key Site 451 - Annalong Valley For general information and references on the sand and gravel landscapes of N. Ireland, and for directions to sand and gravel sites other than those within the Mourne Mountains area, see the following site: Key Site 439 - Introduction to the Sand and Gravel Landscapes of N. Ireland | |
| Keywords | |
|---|---|
| Relations: | Glacial deposit, Glaciomarine deposit, Glaciotectonic |
| Geomorph: | ice lobe, moraine, outwash |
| Record type: | ESCR report | ||
| Entered by: | E M Porter | ||
| Enlander, I., Dempster, M. & Doughty, P., 2026. Mourne Plain Complex - Tullyframe Pit, County Down, site details. [In] Earth Science Conservation Review. https://www.habitas.org.uk/escr/site.php?item=443. Accessed on 2026-11-06. |
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