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Friday, 11 December 2015

THE ASHFORD LIMESTONE CAVES



From the Ashford Tourism website
The Ashford limestone caves are located about 20km north-west of the town of Ashford, between Inverell and the Queensland border. What was once a crown reserve (set apart in 1915) is now part of the Kwiambal National Park (pronounced Kiamble), best known for the spectacular MacIntyre Falls, near which is a delightful camping area at Lemon Tree Flat. Picnic and toilet facilities are also provided at the caves.
From the Ashford Tourism website
These caves are not in the same league as the well-known show caves at Jenolan, Wombeyan and Yarrangobilly, in fact there are very few speleothems (decorations) to be found. What you will find is bats, guano (bat droppings) and a sense of adventure as you explore the unknown (to you) cave system. If you would like to read a fascinating account of “An Excursion to the Severn River and the Wallangra Caves” dating from 1892 (here) you will appreciate that some things have not changed, but others have considerably. The most notable change has been the removal of thousands of tonnes of phosphorus-rich guano for use as fertiliser, a process that was underway long before the reserve was established and continued as late as 1967.

There is a lot of information available about the geology, history and biology of Ashford Caves. I have given a list of downloadable resources at the end of the blog.
The caves have been formed in a bed of Lower Carboniferous limestone (probably, though estimates range from Devonian to Permian), which has been considerably deformed and largely converted to marble. It contains marine fossils (mainly crinoid and coral fragments), but remember that this is a National Park (no collecting allowed) and beyond the fences is private property, which limits the collecting possibilities to road reserves outside the Park. As the limestone has been traced for more than 10 km there must be some accessible outcrops, since the road basically follows the strike of the limestone. If you locate specimens of interest, tell us about it by adding a comment below.
There are a few typical karst features, notably the dolines where caves below have collapsed. You
Calcite formations 1999 (my photo)
might also come across solution grooves, widened joints and potholes as you walk around the limestone hill.
Early references note the existence of two main caves. The removal of so much guano has lowered the cave floors considerably and the two caves are now joined, making a through trip possible. There are a few other small caves but none appear to have much potential for new discoveries.
Three species of bat frequent the caves: Miniopteris schreibersii (the eastern bent-wing bat), Rhinophilus megaphyllus (the eastern horseshoe bat) and Eptesicus pumilus. Most of those you will see are bent-wing bats. Do not disturb them by making loud noises or shining lights on them. During the summer breading season, do not enter the main cave at all.
Bats 1999 (my photo)
The guano had accumulated to a depth of several metres in the most favourable places. A typical chemical analysis reveals that it contains 5-10% of phosphorus. Especially during the Second World War, when supplies of phosphate from Nauru and Ocean Island were cut off by the Japanese (both islands were occupied by them) alternative supplies were identified all over Australia. Ashford Caves was one of these.
Some useful references.
The Ashford Tourism site (here);
Guide to NSW Karst and Caves pp 10-11 (here);
DIGS website (needed for the listings below) here.
Annual Reports of the Department of Mines, New South Wales, for the period 1939-1945 (DIGS reference R00001425). This includes cave maps and guano analyses (beginning on page 82).
The Limestone Deposits of New South Wales (DIGS R00050689). An excellent report from 1919 giving information about all the then known limestone deposits.
The Limestone Deposits of NSW (1986) Lishmund, Dawood and Langley (DIGS R00056921). A modern, revised version of the above.
Geological Age of the Ashford Caves Limestone (DIGS R00019198). Report by Raggatt and Booker, 1940.
A Report on a Visit to the Ashford Cave, Northern NSW (DIGS R00023521). 1973 Anonymous.
You will find my gem hunting/mining You Tube playlist here. I have three other playlists - the Blue Mountains, Glen Innes and New Zealand.

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