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Jan 31, 2004

BERTIE SINKHOLE


Position: WGS84 - 18 15' 12.3" N, 77 19' 46.9" W, +/- 20 m

Field notes: R. S. STEWART

Cavers: R. S. Stewart, I. C. Conolley, M. Bellinger, D. Williams

Time in: 13:00 EST, Time out: 19:00 EST

THREAT VULNERABILITY: Low

We had been contacted by David Broderick prior to the expedition with a report on a deep, undescended sinkhole near Barbary Hill, Aboukir district. It was Saturday, and we had most of the main crew together for the weekend. Today would be the new sinkhole, and tomorrow we would tackle Hutchinson's Hole, after spending the night in Bensonton, close to Hutchinson's.

The drive to Aboukir from Windsor took us a couple of hours, and when we arrived in the district it took another hour hunting around until we found our contact person, Etan, David Broderick's cousin. At about 1:00 PM, we were parked, loading up with gear, and ready to hike in.

We'd brought the 100 m line, along with various other ropes, webbing and vertigear, so we had a fair load to carry. Etan was a big help with this, as was Delroy, and several hundred metres hiking down through pasture-land, under a hot sun, brought us to a large horizontal opening between two high cliffs. The entrance to this sinkhole is about 12 m across, hard against a high rock-wall to the north. This rock-wall is over 10 m high, surmounted by a steep, wooded slope, and drops straight down into the sinkhole. The whole layout is quite impressive.

Our rigging method follows: we used a diversion method that consisted of tying the main 100 m line to a large tree, up about 2.5 m, that was close to the south side of the opening, then diverting it with a 30 m line to a large tree on the northwest side. Etan took care of adjusting, and then tying, the diversion line. When this was all done, I got on rappel, had a quick puff on a cigarette, moved to the edge, and headed down.

The trip down was quite nice... the shaft narrowed slightly for about 15 m and then another shaft opened up on the east, joined by about 25% of the circumference for both shafts. After roughly 15 m more, the two shafts separated, to intersect again further down. I passed a couple of small chambers, about 1 m high, and several m deep, with stals, on the west side partway down. I was very much enjoying it, so I took my time, and about 10 min's later, I touched bottom on the top of a pile of stone-rubble that sloped to the clearer floor of the adjoining shaft, 10 m further down. Judging by the amount of rope left at the bottom, and what we'd used up-top, the rubble pile is about 65 m, and the deepest point is about 75 metres.

I got off-rope, used the walkie-talkie to let the others know that I was down, with rope to spare, and that the others could come ahead. I shifted to the safest, furthest corner of the shaft, and started having a good close look at things while I awaited Ivor and Mark. The only notable invert was an Amblypygid, the first seen of the expedition, which was quite surprising. I can only speculate that that the depth of the hole results in a steady enough temperature and humidity to supply proper habitat. Apparently, there are enough small, flying gnats, flies, etc making it to the bottom to produce a regular meal for this little carnivore.

Ivor and Mark were down in quick time, also both having apparently enjoyed the ride, and after I pointed out the Amblypygid, and they looked around, we began the ascent. I must confess that I don't remember the order in which we went up, only that we all made it up in decent time. Nevertheless, three people had to ascend 75 m, and with the late start, and rigging time, we weren't finished de-rigging and hiking out until about 19:00, in the twilight.

I had a hard time getting a GPS position, due to surrounding cliffs and poor satellite orientation, and because we were running out of light, I had to take what I could get. I've plotted it on the topo, and compared it to the local topography, and I believe the stated position should be accurate to +/- 15 m, but because of the uncertainty I'm listing it as +/- 20 m. Definitely, it needs another visit to refine the position.

I took several pics of the Amblypygid, but the camera that we are using will not produce a decent photo at macro.

This was a first descent, and even though it was well-known to the people of the district, it was an unlisted sinkhole. The report from David Broderick was responsible for our descent, and for this we are very grateful. The local name is Bertie Sinkhole, named after a man who owned the land, and it is being listed with this designation.

After reaching the cars, we loaded-up and headed to Bensonton, the location of Hutchinson's Hole.

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