University of Bristol Spelæological Society

BE THERE OR BE SQUARE!


Join us on 14th March for a delicious three course meal with half a bottle of wine per person (red or white or non-alcoholic alternative).


A form for sign ups and menu choices will be circulated shortly. You are requested to arrive at 6.30pm for 7pm. The restaurant need to start service promptly so plese don't be late!

MUD IN A MAZE


The intrepid team arrive at the cave. Photo by Willhem Glass.
Team: 0, Lionel's Hole: 1 is a not uncommon score when it comes to this particular Burrington classic, known for its muddy boulders and occasionally unstable rocks. Tess tells the story of a recent attempt to find elusive round trip.

Our trip to Lionel’s Hole in Burington was a first for all of us, Kenny Maciver, Tommy DeAth, Willem Glass, Toby Hocking, and I, which meant relying heavily on the survey and a lot of optimism. The day got off to a strong start when Tommy  managed to fall down the hill before we’d even entered the cave, setting the tone perfectly.

Inside, Lionel's Hole turned out to be an extremely muddy experience, perhaps the muddiest any of us had ever had. Toby and I acquired full mud “war paint,” and watching Kenny come out of a squeeze looking like Augustus Gloop emerging from the chocolate pipes was a definite highlight. Navigation quickly became a recurring theme, with Kenny frequently heading off to check passages while the rest of us stood around hoping he’d come back, especially since he has a habit of forgetting to respond when called.


Yes, it's muddy and it's a maze. Photo by Willhem Glass.
Despite being promised a dry cave, we found ourselves in a streamway crawl, singing our way through it. At a crossroads section, while Kenny searched yet another passage, we filmed a vlog and officially named ourselves the Brown Boots. Unfortunately, the survey defeated us in the end, and we had to retreat the way we came, which revealed that everything is far easier on the way down, especially when recovering from the previous night’s drinking shenanigans. We eventually surfaced very muddy, well past our ETA (but not over our call out), but in good spirits. Overall, it was a great, slightly hungover trip with good people, and we walked back like the Ghostbusters.

REDHOUSE LANE SWALLET


Mark Tringham explains the recent science and radio location survey work carried out in one of the UK's fastest growing sites, Redhouse Lane Swallet in the Forest of Dean.
 
With prolonged dry weather extending well into October several Redhouse trips were possible to make scientific observations, take photos, gather rock samples and perform some radio location measurements. These visits have further built up our knowledge about the cave morphology, geology and speleogenesis. The trips are described chronologically below and the areas visited are highlighted on the survey plan below.
 
1) 20/9/2025. Participants: Tim Gibbs, Stephanie Lee, Mark Tringham & Elin West
 
Objectives: Make observations on geology and speleogenesis and take photos from Toto’s Pitch to Mindless Optimism (MO) and along Cryogenic Causeway (CC).
 
Geological features were observed and photographed including the pervasive wrench type faults with steep to vertically inclined fault surfaces, thick breccias and sub-horizontal slickensides. Bedding dip across the newly found Redhouse Monocline was traced out between Tiffs Treat (TT) and CC with bedding dip reaching a maximum of about 35 degrees just before MO. The Lower Dolomite – Crease Limestone boundary was found at MO, where it is heavily mineralised. Travelling along CC the bedding dip is seen to quickly reduce to more or less flat and this passage remains within the Crease Limestone. The Crease Limestone along the first part of CC is of particular interest due to its colourful iron mineralisation and likely paleo-cavern infills.


Above left; Toto’s Passage perched boulders in wrench fault zone. Right; The Crease Limestone – Lower Dolomite contact half way up and with red haematite mineralisation in the lowermost Crease.


Above Left; Crease Limestone (white) with brown dolomite (?) likely infilling paleo-caverns. Right; Contact within Crease Limestone with alteration halo beneath likely paleo-cavern fill.
 Speleogenetic features seen included rare wall scallops in dolomite found on the approach to MO showing westerly paleo-flow. Then in the Crease Limestone all along CC plenty of wall scallops occur and these also show westerly paleo-flow. Many cryogenic features were observed and photographed in CC including powdery calcite along the passage centre-line, copious amounts of fluffy mud and interesting mud ridges and mounds. Perched stones and perched fluffy mud was seen in several places along the passage walls, perhaps supported at one time by a partial ice fill, as reported by Joel and the survey team before. Green marl run-in cones occur in several places, blocking or partially blocking the route and these seem likely to be paleo-karst potholes formed during the Carboniferous and infilled by muddy Whitehead Limestone sediments. These cones include fragmented calcite speleothems. The CC Passage is very beautiful with its white coloured host rock and green run-in cones and it contains a real feast of interesting geological and speleogenetic features that will repay further visits and more detailed scientific work.


Above upper left; wall scallops which show flow to left (WSW) in Cryogenic Causeway. Lower left; perched angular cobbles on shelf and muddy ‘tide mark’. Centre; broken calcite speleothems that were entrained in green marl run-in. Right; mounded cryogenic calcite and fractured ceiling with green marl infill.


Above left; Keyhole shaped passage formed along vertical wrench fault in Cryogenic Causeway, with scalloped walls and unusual ‘fluffy mud’ sediment ridge. Right; big meandering phreatic tube passage in Causeway North with fallen blocks, a centre-line of white cryogenic calcite and more fluffy mud.
2) 5/10/2025. Participants: Andrew Brander, Tim Gibbs & Mark Tringham.
 
Objectives: Make observations on geology and speleogenesis and take photos along Mindless Optimism (MO), We’re Off to See the Wizard (WOTSW) passage, the first part of Into the Void, Frosty Freeway area, Higher March and Chocolate River.

Geological observations included following by eye the roof of MO which is formed at or close to the Lower Dolomite- Crease Limestone boundary and this dips at a moderate angle of about 20 degrees to the West. In WOTSW just past the junction with Into the Void the cave passes wholly into the Crease Limestone, and dips were seen to decrease quickly to more or less flat. Nice coral fossils and other coarse bioclastic grains are visible in the white coloured limestone. The Crease Limestone is quite faulted and has large zones which are mineralised, probably formed as paleo-cavern infills. Like Cryogenic Causeway green marl ceiling patches and debris run-ins occur. The final part of WOTSW is heavily faulted with breccia and iron mineralisation, so much so that the host Crease Limestone is not visible at all. The passage stops at a large green marl/claystone run-in. Speleogenetic features along WOTSW include roof pendants, wall scallops that indicate westward paleo-water flow and a thick sediment fill of dried out and cracked fluffy mud and some cryogenic calcite which in places has a small scale dendritic form. Because of the broken down nature where faulted and mineralised and the sediment fill, clear phreatic vs vadose features are not visible, but based on what can be seen and the comparative position relative to Cryogenic Causeway, a largely phreatic origin seems likely.

Into the Void passage seemed too hard to free climb up into, so a visit there was postponed.

Just before the end of MO Passage and into Wicked North the passages were seen to pass stratigraphically down into the Lower Dolomite. After descending the Wicked Pitch the team went westwards to check out geology and scallop directions towards Frosty Freeway and into the unnamed passage going NW. We found all the passages to be fault aligned in the Lower Dolomite and with scallop flow back towards the foot of the pitch coming out of Frosty Freeway as well as to the NW along the unnamed passage.

Taking the main route on from the bottom of Wicked Pitch bedding dip becomes fairly flat in the Lower Dolomite host rock and many scallops occur showing paleo-flow consistently to the NW. At a cross-rift just before Consolation Climb a prominent fault brings the cave down into the Crease Limestone. Going onwards towards and into Chocolate River the cave stays wholly in the Crease Limestone with meandering form not much controlled by fault alignment and with consistent paleo-flow to the NW as evidenced by scallops. Cryogenic fluffy mud is abundant in the dry section and powdery cryogenic calcite occurs in a few places. Interesting side gutters occur to the mud banks in places with unusual mud mini-gours as noted by the original explorers/survey team.

The Burrow appears to act as an inlet complex as evidenced by wall scallops there. In the first part as well as cryogenic calcite, broken calcite flowstone plates occur about 2cm thick formed over an arched mud floor, the arch and fragmentation likely related to frost heave under cryogenic conditions. The team only had time for a quick look into the near part of The Burrow and to visit the far end of Chocolate River to admire the mud cracked but very sticky floor. The water source here is enigmatic, with ponding evident when first explored earlier in the year. But the water might well have flowed down from The Burrow even though in this area the Coal Measures above generally form a fairly impermeable cap. Sediment fill here obscures the floor everywhere and phreatic passage forms are visible only.


Above left; the far end of WOTSW Passage with highly altered, faulted and fractured zone in Crease Limestone and with green marl run-in. Centre; side-gutters with mini-gours cut into fluffy mud fill. Right; White Crease Limestone in Chocolate River Passage with minor fractures in ceiling and abundant .wall scallops showing flow away from the camera to NW. Mud floor shrinkage cracks that are subject to episodic flooding.
Our tour to this far NW end of the cave was a bit rushed and the observations at this initial stage were mostly confined to finding scallop flow indicators and determining the stratigraphy and dip and getting a few photos.
The trip was nearly 11 hrs duration and we came a bit close to blowing our call-out time. Thanks as ever to the co-workers for their contribution and good humoured endurance.

3) 14/10/2025. Participants: Craig Cameron and Dan Sandford (surface), Falkland Anderson, Emma Caspers, Mark Tringham and Elin West (in the cave).

Objective: radio locate Missed Chamber survey point 6.1 to confirm survey underground position from surface. This is estimated to be the closest point to the surface past the wet parts of the Entrance Series, before the cave passes under the hill.

Following a surface planning and equipment check the underground team made quick progress taking only 30mins to reach the set up point and after a short time had assembled the kit and switched it on. They then had a good look around Missed Chamber and took photos for 45 minutes. On the surface Craig picked up signal straight away close to expected location, despite power line interference close by. Within the allotted time-frame he performed the necessary traverses to determine the surface spot and calculated a depth of 34m to the transmitter. The underground team disassembled the kit, brought out the battery and transmitter, but left the coil and wooden frame in the cave at 2nd Junction for work planned the following weekend near Call of the Crow.


Above left upper; the radio transmitter set up in Missed Chamber. Left lower one of the 3 main fault planes observed there displaying sub-horizontal slickensides. Right, view down Missed Chamber with the two other vertical faults with haematised breccia visible in the roof.
After the cave team surfaced, all went to the surface spot to survey it using Distox2 and tie in to reference points marked by nail varnish on a big nearby tree and a fence post, and take a satellite GPS reading using Garmin eTrex 30. The RLP depth estimation of 34m compares to survey depth 35.5m (cave roof in chamber is 4.5m higher than survey station). So a potential dig depth from surface is 29 to 31m. Based on the Google Earth terrain model, the surface survey location is within 1m of expectation and near the side of field. Therefore the result confirms good accuracy for the underground survey for this part of the cave. The Garmin GPS satellite point showed ± 10m so the spot needs rechecking later after leaves come off an overhanging tree. Therefore in the event that a dug entrance is wanted here and bearing in mind the large chamber size we could be very confidant of hitting it.

Thanks to all participants for the successful results, but especially Elin and Emma who came up from Cardiff especially for the evening.

4) 18/10/2025. Participants: Emma Caspers, Isaac Neale and Max Theyer, Mark Tringham and Elin West.

Objectives: Collect rock samples around Mindless Optimism and first part of Cryogenic Causeway. Visit March Madness Series Upper and Lower and White Forest as far as Howling Hole, to define geological and speleogenetic features present.

Results: The team made their way in at 10.15 am and reached Mindless Optimism 1½ hours later. After checking where it would be best to take rock samples equipment was unpacked and 15 representative samples were collected in readiness for potential analysis by University of Manchester. These were labelled and packaged up securely with everyone’s help and photos taken of the locations. The mystery brown weathered rock which infills apparent paleo-karst caverns in the Crease Limestone looks like a hard grey dolomite on fresh surfaces. The samples were left at MO ready for our return out at the end of the day.


Above; example rock sample location (no.1) showing before and after removal plus the resulting sample.
The team then made their way to Wicked Pitch of the North and after some faffing about getting usable SRT kits assembled descended OK. Going northwards they took the lower route and found the way along the Lower Series until it’s termination at a boulder choke. They checked for paleoflow indicators and lithology with hydrochloric acid dropper bottle. All was found to be dolomite and flow from wall scallops trends NW. Passage fault alignments were observed, as usual, but gentle structural dip to NE was anomalous compared to other parts of the cave. Systematic measurement of stratal dip throughout the cave is warranted in the future to catch these types of detail. Photos were taken showing some of the larger parts with fine smooth muddy sediment banks. They believed their visit was only the second time this Lower Series has ever been visited since the original exploration/surveying. They found a fairly easy rift climb up to near Calibration Chamber (close to stn 136.2) and this saved quite a bit of time for the onward journey, compared to back-tracking to the start of the Lower Series.

They progressed onwards towards Consolation Climb checking on geological details as they went and captured some nice passage profiles and a haematite mineralised zone at stn 91.32. All this part of the cave is formed in the Lower Dolomite, but many variations in rock texture, colour and sedimentary structure, such as cross-bedding occur. The rift passage that leads to Consolation Climb was checked carefully and it definitely has Lower Dolomite on the South LHS and Crease Limestone on the RHS as originally noted by the original explorers earlier this year. The passage has formed along a significant fault with around a half metre thick breccia and a subordinate fault branch on north side within the Crease Limestone. At the head of the climb the Crease has a brown dolomitized zone masking the contact but just around the corner in the Chocolate River direction the normal white-grey Crease Limestone character is seen again.

This team crossed paths with the outcoming radio location team who had gone into the cave earlier and set up the radio transmitter and filmed at Crow End. They had established a good connection to surface with both radio location and telecoms as well. Analysis afterwards proved the cave survey to be 6m or less from the expected plan location and at a depth of around 25m or less.

The team descended Consolation Climb without issue and made their way along through towards White Forest, making a note of the persistent fault alignments on the way, the initial part of the passage displaying an unusually light coloured metre thick fault breccia stretching high into the ceiling in places. Most of the fine speleothem formations seem to be linked to water percolation down through this prominent fault zone. Downwards on Consolation Climb the cave passes into the Lower Dolomite and appears to remain so until at least as far as Howling Hole.


Above left; keyhole shaped passage near Calibration Chamber largely phreatic in origin, but with likely vadose floor pockets and trench. Centre; the faulted rift near Consolation Climb with Lower Dolomite on the right (S) wall and Crease Limestone on the other side. Two or more fault planes converge downwards. Right; the fault-aligned passage below and just west of Consolation Climb with 2 main fault planes converging downwards and a pale breccia zone between.


Above; The White Forest with intricate straw and helictite speleothems, some with side or upward branching arborescent shapes, likely formed by aragonite.
The cave here remains largely fault-aligned but the faults divide into separate segments with differing trends, initially E-W but then further along ESE-WNW, as can be seen on the map Figure 1. The latter section of passage shows a fault zone hading South at around 15 degrees off vertical. On either side of Howling Hole where the two stream inlets occur, ceiling segments are seen with green marl. But from ground level it’s hard to tell if this is a fracture or paleokarst infill feature or whether it’s a stratigraphical contact with the overlying Crease or Whitehead Limestone. The bolt climbing team who have recently been up the 2nd inlet have observed further details about this.


Above left; The White Forest with inclined fault rift above and curtain speleothems formed on hanging wall. Centre; Inclined fault rift just before Howling Hole with multiple downward converging fault surfaces. Right; the green roof bed and very brecciated dolomite above Howling Hole.
After a snack break past Howling Hole the team made their way back along White Forest taking many photos of the superb helictites and fault features. Consolation Climb provided an awkward challenge to some of the team, especially when hauling a bag up. Otherwise an uneventful journey was made out of the cave, picking up the rock samples from MO on the way.

A lot of ground had been covered and the team spent significant time on the observations, photos and rock sampling and so they finally emerged from the entrance exhausted at 11pm after 12¾ hours underground and with only half an hour spare before the set call-out time. All objectives were fulfilled thanks to the superb assistance from everyone. The rock sample bag including hammer and chisel weighed 6kg and Emma must be congratulated on bringing this out all the way from MO.

The samples were checked the next day and all are sound and they will form a preliminary set to offer to University of Manchester for petrographic analysis as part of an MSc student project in 2nd Quarter of 2026. The observations made are preliminary, but with the other two long science trips conducted earlier in October and further investigations in 2026 we are beginning to unravel Chapter One of the fascinating story on geology and speleogenesis in this amazing new cave.