Jamaican Caving Notes
May 7, 2005
Team: Stewart, Conolley.
Notes: RS Stewart
On our way to and from Marta Tick Cave the day before, May 6, we had noticed a shaft to the west of the track in bottomland near Sawmill. In past years, this cockpit bottom had been very bushed-up and we had passed this opening several times without seeing it. Now, post-Hurricane Ivan, flooding of the cockpit the autumn before had killed-off enough of the brush that the hole was revealed. The bottomland held primarily low grasses that had grown back over the months since the flooding, and the opening to the shaft was obvious from 50 metres away. Our main goal for the day was to continue explorations of the district in hopes of finding an easy route to where we expected to find Gremlin and Undernose caves, but it was decided that this new discovery should also be done. We were successful in both expanding our knowledge of the bush enough to enable us to find Gremlin and Undernose later in the expedition, and in determining that this new shaft was previously unexplored, and unlisted, and is one of the more interesting caves of the district. It should be noted that at first we thought we might have found either Gremlin or Undernose, with the JU positions being in error by over 500 metres, because this cave resembles the maps for those two, and we have known of caves to be listed over a km from where they are actually found. This problem with accurate coordinates is understandable, because most of the listed caves were explored and mapped long before GPS technology became available. Plotting of positions was done by comparison with topographical maps, and this is very difficult to do in the Cockpit Country. These days, we regularly repeat positions for caves to within five metres, and subsequent plotting on the topos invariably shows them to match reality. At times, canopy and hills make satellite acquisition less than ideal, but we still manage, at worst, to establish positions that repeat to within 30 metres on our second visit. We know when we obtain the positions how good the fix is, by noting the number of satellites (we enter this on our datasheets), and afterwards list the accuracy accordingly.
The entrance to Sawmill Cave is close to the bottom of the hill on the west side of the glade. It faces roughly 45 degrees true, but because the opening is rather horizontal, the entrance aspect is vague. Like other caves and shafts in the district, the opening is through breakdown boulders that have fallen in from the hill immediately above. The boulders are large (2-3 metres), and jagged. Care must be taken to not have the rope cut by these. Our method, upon reaching the shaft and deciding it needed to be explored, was to use old logs as rope pads at the top where our rope was in greatest contact with the rock, and then to descend and ascend as delicately as possible. I will now describe the actual descent into what we would later decide should be called Sawmill Cave.
The rope that we had brought this day was 60 metres in length. It was tied to a solid tree about 10m back from the opening, and fed into what appeared to be the best route through the boulders into the shaft. After getting on rappel, I began to carefully thread my way down, adjusting where the rope made contact with the boulders by traversing sideways in places, while pushing myself away from the rocks. As I went lower, the shaft did not become smooth-sided, such as Minocal's Glory Hole, but continued to lead through jagged boulders, with the voids less than 1 metre in places. I carried on downwards as delicately as possible, thoroughly expecting to hit a final choke at the bottom. Instead, to my pleasant surprise, I finally found myself descending into a medium sized chamber with an obvious extension.
After getting off-rope, I explored onwards and found a second chamber of about the same size that is some 7m high, 10m wide, and 12m long (these numbers are conservative). A close look for what might be living here resulted in the discovery of several Sesarma verleyi, but no other trog inverts. It should be noted that the chambers, and shaft itself, were quite muddy in places and it appeared that there had been flooding, probably during Hurricane Ivan. This is similar to several other caves we are familiar with in the district (Gremlin, Undernose, Minocal's) that also did not have troglobitic macroinvertebrates that we were able to find. The Sesarma, water-loving stygobites, seem to be little bothered by the mud, and as at Minocal's were present in the lowest sections of the cave.
The source of the mud found here, such as at Minocal's, is not as clear-cut as would be thought. The obvious point of ingress would be from the surface, but observations at Sawmill suggest that this might not be the case. We are very familiar with the conditions found in caves that we know to take surface water (acting as seasonal or flood-time sinks). Much detritus will be found, in the form of sticks, logs, bamboo, and if close to civilization, garbage. At Sawmill, I was impressed by how little detritus was present, considering how much was available in the cockpit above. Signs of flooding were obvious, in the thick, relatively fresh mud covering many of the surfaces in the lower section. Some leaves and twigs were present, but notably, I observed several of the leaves to be stuck to the mud on the underside of boulders, not on the tops. There were no actual logs seen in the pit. The appearance of the muddy surfaces was reminiscent of places I have seen in caves where I know the water to rise (e.g. Bad Hole, near Windsor, and Duppy Cave, near Springvale). There is a characteristic "smoothness" to the surfaces, with no erosional gullies in it caused by rapidly flowing water. If I could make a guess as to what happened at Sawmill Cave, and other sites in the same district, during the previous rainy-season (including Hurricane Ivan), it would be the following process: Heavy rains did indeed at first feed some detritus into the hole, as evidenced by the leaves and twigs I observed. But either, 1 - the cave filled entirely from above, causing these leaves to rise, floating on the surface of the sumped water to stick to the underside of boulders (but there were no logs, so this is doubtful), or 2 - the flow from above was also augmented by a general rising of the local phreatic zone (water-table) causing much of the flooding of the glade to come from below, that is from the shaft itself. The fact that there was no large debris, such as logs, in the hole, makes it hard to envision a great enough flow into the opening from the cockpit, such as in case 1, to fill a shaft that no doubt has rock/mud choked extensions at the bottom that would allow the water to exit. The fact that Sesarma verleyi are present, as at Minocal's Glory Hole, indicates that there is indeed a subsurface connection between Sawmill Cave and other sites. As confirmed with Dr Schubart, at the University of Regensberg, S. verleyi, do not travel from site to site above ground. Other Sesarma species can, but not S. verleyi and we have consulted with Dr Schubart to be sure that this was the species found (this is one critter that is easy to identify).
We did not take time to survey this cave, but by using the rope we were able to determine that the chambers at the bottom are in excess of 30m deep, and probably more like 40 (it was a 60m rope, we had used about 12m up-top for rigging, there was about 5m on the floor at the bottom, and I had used up probably another 3-4m zigzagging through the boulders).
Biologically, the interest here is the Sesarma verleyi, and how they arrived. Two legs were collected and stored in 95% ethyl alcohol, to receive DNA analysis courtesy of Dr Schubart.
At the end of the day, we consulted with Minocal Stephenson to see if the NSS had explored this cave. He told us that they had looked at it, but not entered it. There are no JU positions that plot near the site. We are fairly confident that this was a first exploration. We have decided on the name “Sawmill Cave”, because Sawmill is the closest area in the bush with a name.
After carefully ascending back up through the jagged shaft, without slicing the rope en route, we stowed gear and resumed our search for the approach to Gremlin and Undernose. This meant moving further north through the cockpits, searching for holes as we went.
I will not enter separate notes for our next find, but will include it here with the designation, Sawmill Collapse.
At a bearing of 10 deg true, 210 m from Sawmill Cave, at WGS84 coords 18 18 06.0, 77 43 06.3, +/- 15m, there is a small cave in a cockpit bottom. It extends for about 30m, but the outer half has collapsed into a bouldered slope that leads down from the cockpit bottom to where there is extant cave. There is no dark zone, and the only animals of interest are E. cundalli. We are primarily noting this site for the purposes of sorting out what is what, for ourselves, and for others in the future. This listing will help researchers to not confuse this with a previously listed site. It will appear in the database that accompanies this report.
When we had finished with Sawmill Collapse, it was 3:00 PM. We decided to work our way back towards the start of the trail, and explore the saddles that lead from south Sawmill to the cockpits to the west.
This exploration resulted in us reaching a point low on the side of a deep cockpit, at 18 17 45.9, 77 43 08.1. The trek had been rough in the extreme, and it was now 4:30 PM. It had been pouring rain for hours now, and we anticipated an early sunset due to the thick clouds, so we began to make our way back towards Sawmill, taking a short detour on the way to explore the saddle further to the north, where we determined that this would be the best route to the cockpit that we had almost reached. It should be noted that at our farpoint, low on the hillside, we caught sight of what appeared to be a collapse or pit about 50m away, and below us. It is at a bearing of about 230 deg true, 40-50m from 18 17 45.9, 77 43 08.1. Although it might sound like we were almost there, and should have taken a look, conditions in that part of the bush (no trail, steep rocky slope, and fallen trees) were such that it would have taken us an hour to do it, and we did not have enough daylight left. The position has been checked against the JU database, and there is no site listed in this cockpit. The cockpit is small, surrounded by steep slopes, and is in between the Sawmill series and the Gremlin/Undernose series - in other words, there could be a cave or shaft here that the NSS did not find, because Minocal Stephenson didn't take them to it.
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