February - 2019

Mulu Caves 2012 was the 20th Anglo-Sarawak Expedition to Gunung Mulu National Park and operated in the field between 3rd and 29th April 2012. The expedition based itself at National Park headquarters. The team was led by Andy Eavis and Dick Willis and included a total of sixteen members from the UK and Australia, together with a number of participants from our hosts at Sarawak Forestry. The expedition was further assisted by National Park Management, staff and local people.
The expedition had a mixture of scientific, exploration and filming objectives and The Mulu Caves Project is very pleased that all the major objectives were successfully completed.

Paku Valley

Looking into the Melinau Paku valley | photo. Andy Eavis

Scientific programme

Bellhole with bat

Bellhole with bat | photo. Dave Checkley

Bellhole formation – Julia James
A study of bellholes was undertaken in 3 caves –Lagan’s, Lang’s and Fruit Bat. Measurements were taken of numbers, distribution, width (by 4 different methods) and depth; the presence of bats was recorded. Expedition members also recorded the presence of bellholes in other caves. In addition, water samples were taken and analysed for pH and conductivity. Two papers are planned for publication in due course, one on methodology and the other on the formation of these fascinating features. Many informed discussions were held between members of the team regarding possible formation processes.

Lagan’s Cave Sediments – Jason Lin and Prof Peter Smart
The sedimentary sequences in Lagan’s cave were logged in detail. Samples of gravel matrix and clays were taken for grain size, and Xray diffraction (XRD) sampling. In addition, a detailed morphological study with the sedimentological data will be used to correlate Lagan’s cave formation phases to the aggradation of the Melinau Paku and Melinau River. Sedimentary sequences in other caves have also been sampled and characterised for comparison. This study will contribute to Jason’s Master’s thesis.
At least one paper is planned for publication.

Sediment sampling

Sediment sampling in Lagan's Cave | photo. Dave Checkley

Cave Dating – Chris Smith and Prof Peter Smart
In continuation of earlier studies, samples of speleothems, mud and quartz crystals were collected from a number of locations in Lagan’s, Clearwater, Red Leaf Monkey One and Two and Train caves. Of particular interest was a complete sequence of fine sediments found and sampled in Red Leaf Monkey One Cave. Such complete sequences are very unusual in the Mulu caves and may allow an indication of the duration of sediment accumulation during paragenetic cave development. Speleothem samples will undergo preliminary analysis via UraniumThorium dating at Bristol, samples exhibiting basal ages greater than 500 ka will be analysed via UraniumLead at the NERC Isotope Geosciences Laboratory (NIGL) facility at Keyworth. Speleothem ages will help to establish the minimum age of passage dewatering, which is crucial to understanding the rate of regional base level incision, and the overall age of the caves. Mud and sediment samples will be dated using Palaeomagnetic and Cosmogenic nuclide methods to provide alternative chronologies. This intercomparative dating approach will help to provide a more refined estimate of the regional rate of incision and timings of cave evolution within the Gunung Mulu National Park.

Guano Geochemistry Prof – Peter Smart
In a new study, samples of guano and the related crusts and derived powdery sediments have been sampled from a number of caves to obtain an understanding of the geochemistry and mineralogy of these deposits. Of particular interest is the role of the precursor mineral phase (clastic sediments or bedrock) and the possible coexistence of gypsum (calcium sulphate) in the deposits. The latter is highly soluble and not normally found in humid tropical cave environments. Samples of cave drip waters and those which had been in contact with fresh guano were also collected to determine possible sources for the sulphate.

Cave Exploration

Mayday Cave
The 2010 Expedition reported a potential lead in Mayday Cave which required bolting. This was climbed to reach a large shelf above the main chamber from which a well decorated passage trending south ended in a 10m pitch down which was followed by a slope and a pitch of 15m into a chamber with a sloping floor choked in dried mud. Past the passage entrance, a boulder slope leads to a NS trending headwall. A crawl north for 150m ended at a stal constriction.

Daniel’s Cave
The 2010 Expedition also reported a potential lead at the head of a climb. Two days of bolting determined that this lead was blind.

Lagans Cave

'A Bit on the Side' Lagans Cave | photo.Dave Checkley

Lagan’s Cave
Significant extensions were made to Lagan’s Cave with the survey of ‘A Bit on the Side’. This is a large, well decorated chamber to the south of the lower entrance to the cave (the show cave exit), which appears to lie on top of a massive boulder collapse. The chamber is accessible at various points from the show cave via climbs of varying difficulty. From this chamber a steep climb down leads to Leopard Passage, named after the appearance of a bed of rock with oncolites (cyanobacterial concretions) which forms the roof. This point can also be reached via a low section of passage, ‘MUSS be Mistaken’ which ends in a 4m bolted pitch which drops to the edge of a sump pool.

Leopard Passage runs parallel to an active streamway which appears and disappears in a series of sumps: the stream contains a population of large fish and other, smaller fishes. Passing over a small rock barrier leads to a wide, mudfloored chamber, Toad Hall named after a pair of resident toads, which appears to be a flood reservoir. A tricky climb up from Toad Hole leads to a higher level, Up In The Gods, which is well decorated and leads to a further ramp upwards to a point where a high level passage can be seen, this was bolted into and lead to a further 150m of passage closing down in a draughting choke. A traverse across a muddy ledge in the roof of Toad Hole leads to an area of stal that closes down. Beyond Toad Hole, the streamway is regained but sumps after a short section of canal. An aven above may lead to a way on but will require bolting. Wading across one section of stream leads to a short walking section, a static pool and a flowstone climb of 4m into a low section, lonely Swift Passage, which appears to skirt a choke. The passage draughts strongly in places, however it closes down after approximately 180m at a point with no draught.

Leopard Passge, Lagans Cave

Leopard Passage, Lagan's Cave | photo. Rambli Ahmad

A surface exploration discovered a sink in the bed of the Sungai Paku that is believed to feed the stream in the Lagan’s extensions. The resurgence was not located but the Sungai Lupar was located very near the postulated resurgence for the cave and therefore seems to be the most likely candidate. The quantities of water that are observed to sink in the Paku appear to be similar to those seen flowing within the cave and also in the S. Lupar.

Dream Pool Entrance (Lagan’s Cave)
From the Dream Pool entrance, the passage was surveyed to a draughting boulder choke. This was pushed on the right down a 10m pitch to a fast flowing stream with downstream sump. The upstream the passage continued in deep water until airspace was too constricted after 14m. Flow in this stream appears to be similar to that observed in Sungai Lupar. An attempt was also made to pass the choke on the left, via a 15m bolt climb into a chamber, but this route was blocked by a drafting boulder choke approx 30m above the passage floor. Horizontal separation from the end of A Bit on the Side is approximately 100m.
A total of 1885m were surveyed in Lagan’s Cave, bringing the total length to 5,785m.

Moon Cave (Gua Bulan)
Adjacent to the HQ to Clearwater track, just before the first set of wooden steps, is a resurgence that comes from a short cave. Adjacent to this is an obvious entrance which leads to a very fine example of a phreatic tube (approx diameter 5m) with an incised trench in the floor. The passage leads to a second entrance in the hillside.

Red Leaf Monkey Cave area.
From a camp in the entrance of Red Leaf Monkey Cave One (Gua Kelasi Satu), which lies
approximately 600m above the entrance to Nasib Bagus, four caves were explored. Gua Kelasi Satu Gua Kelasi Dua, Train Cave and Gift Horse Cave.

Gua Kelasi Satu has a well established camp in the entrance used by nesters and has a fine view down on to Batu Nigel and into Tiger Cave. The cave is 1262 m long and is an easy walking cave with two large chambers. An exit from the largest chamber descends as a phreatic passage to a pitch, which was not descended, but has extensive nesters’ ropes in place both down the pitch and on the walls opposite. They have gone to extraordinary lengths to reach nests. Another route higher up in the big chamber led to a strongly draughting aven 48 m high. Gua Kedasi Dua is further west along the cliff and considerably higher. It is 850 m long with a large passage initially, but degenerates into quite small choked crawls and little climbs before getting choked with gravel. One slippery climb was not completed and was later found to be heading for the 48 m aven in Kedasi Satu.

Train Cave

Train Cave | photo. Tony White

Train Cave entrance was reached from the Kedasi camp and is situated much higher up the main track from the Paku in the first large doline heading over to Hidden Valley. A nesters’ camp was found at the high point on the track before descending over increasingly exciting pinnacle karst to the entrance climb. The cave descends vertically in a rift down a series of pitches to intersect a much larger passage with several little rope climbs and pitches to a more complex series of old passages. An upstream route led to a large shaft entrance. The main downstream route led to a nesters’ underground camp with several ways off. One way led up into two large guano filled chambers with an exposed climbing route to the ceiling, but no way on.

The main draught was followed out of the nesters’ camp and up two parallel northbound passages. These connected via pitches down. The right hand one also led to another surface shaft. Part way along this right branch a bolt climb led up to a crawl and pitch down into a complex series of passages which were only partially explored. However a series of three pitches out of this level dropped into Bridge Cave in Pipped to the Post. 4.75 km of cave were surveyed in Train Cave bringing the length of the Cobra – Cloud – Bridge – Train system to 20.25 km.

Gift Horse Cave is situated in a 70 m wide by 30 m high cave entrance to the right of the track up to Train cave. It is only 100 m long and almost completely filled with calcited gravel and boulders.

Gavin Newman, assisted by members of the expedition team, undertook some filming in the major caves. The focus of this activity was on obtaining a record of the group of cavers who were involved in the original discovery and exploration of Sarawak Chamber in 1980, taking advantage of their presence together in the Park for the first time in almost 30 years.

Summary of surveys undertaken
Cave Surveyed length

  • Lagan’s Cave 1885 m
  • Consolation Cave 117 m
  • Gift Horse Cave 104 m
  • Red Leaf Monkey Cave One 1262 m
  • Red Leaf Monkey Cave Two 850 m
  • Train Cave 4750 m
  • Mayday Cave 524 m
  • Moon Cave 279 m

Total 9771 metres

NB these figures are provisional and will be confirmed in the expedition final report

Members of the Mulu Caves 2012 expedition are very grateful for the support of the following
individuals and organisations.
From Sarawak:
The Chief Minister of Sarawak
The Sarawak State Secretary
The Director of Forests, Sarawak
Protected Areas & Biodiversity Conservation Unit, Sarawak Forestry Corporation
G.Mulu National Park Management & Staff
Local organisers and assistants
Oswald Braken Tisen
Rambli Ahmad
From UK:
Commendium Ltd
Makita (UK) Ltd
Ghar Parau Foundation

A full list of acknowledgements will be published in the final report