This a familiarisation trip aiming to reach the surveyed end of DD31. It is expected to be at least a 6 hour trip and will be physically demanding. It includes two ladder climbs, a handline climb, and a mild roof-sniff. This also entails carrying extra gear in addition to the usual personal gear. Much of the trip will be along an active stream way, so water immersion will be expected.
Selection for this trip will take into account perceived ability to cope with the physical demands of the cave.
Only five people have been to the end of DD31 so it is still a pristine environment and affords the opportunity to be involved in a unique experience.
This is definitely a fair weather cave. If rain is expected we will divert to DD4 instead.
Accommodation is caravan park cabins in Nelson. Shared cost will be worked out once final group numbers are known and accommodation is booked. Transport costs can be reduced by car pooling. Once final group participants are known there will be an opportunity to negotiate car pooling.
The itinerary will be
- Travel to Nelson on Friday afternoon/evening
- Travel to Dryk Dryk, cave, then travel back to Nelson on Saturday.
- Travel home from Nelson on Sunday
Please contact Nigel Cooke (programorganiser@caving.org.au) for expressions of interest and further details.
Trip leader: Nigel Cooke under the guidance of Peter Freemen.
Cave Description (by Peter Freeman)
3DD31 provides the continuing conduit for water that flows through 3DD4 Jones Ridge Cave, and discharges it near the Glenelg River at the long known resurgences DD25 & DD26. The cave is named in honour of the first owner and occupier of the property now called Rangeview, William Swain.
Swain Cave is an active vadose stream cave developed along the sub-horizontal contact between Gambier Limestone (Tertiary marine calcarenite) and Bridgewater Group (Quaternary eolian dune calcarenite). One supposition for its speleogenesis is that it formed later than DD4, in response to the laying down of sand dunes that formed the Quaternary limestone. This was between 0.6 and 0.2 Mabp, prior to which DD4 discharged its stream at the base of a Gambier Limestone cliff. That surface stream became buried by the dunes, but continued to flow through the sand along roughly its original path and gradually formed this vadose cave at the Gambier/dune contact.
In the early part of the cave this relationship to the two rock layers is obvious. The roof is of dune limestone with large basalt boulders embedded in it (and gradually falling out). These boulders would have been lying on the Tertiary limestone surface over which the original stream ran down to the river, and which became covered by sand dunes; the boulders became embedded in the lowest layers of the dune limestone member as it was laid down. Their source was a local lava flow during an eruption around 2.4 Mabp, or perhaps the later breakup of a lava capping on Jones Ridge that had been created during that episode.
The floor of the cave consists of Gambier Limestone, often littered with dune limestone breakdown and basalt boulders released by that breakdown. At some points the contact between the two limestones can be observed in situ, often near the base of a side-wall. The embedded basalt boulders are obvious and spectacular.
The main stream in DD31 is a continuation of that in the adjacent DD4 cave. The combined length of DD4 and DD31 would be around 5 km if they could be connected. Swain Cave itself is almost 2.5 km in length. The resurgence for DD31 is believed to be DD25 and/or DD26 near the Glenelg River, 1400m to the WSW of DD4, as the DD31 cave surveyed end is very close to the resurgences.