Sit Rep;
Went over for a 'memory jog' (the ony jogging I'm capable of now!) on Sunday, concluded that Petras is not a continuation of the hole I remember, still got to formulate all my ideas into some kind of theory.
They certainly 'raped' the place in the closing down stages and removed most of the landmarks I noted on the site visit, the only other caver there with me on that day was Mick Fish (RIP), don't know if he left any record?, sometime between '84 & '89?, it was a P.R. open day by the company trying to drum up support for extending operations from interested bodies.
I suspect that the hole has been filled in when they levelled the floor at closure;
I also have the impression that Sidetrack, Petras, and Conveniece are all intercepted passages from abandoned swallets, akin to Nettle, Mountbatten, Thistle, Eldon, etc., accumulating in the vicinity of the quarry and descending into the 'Main Drain' - water flow marks from scallops would confirm or defeat this conjecture.
I estimate the thickness of coarse backfill on the bottom (and only remaining) terrace to be around 2-3m average, this is the thickness of loose stuff we have to detect through to map the bed rock and find a void filled with loose stuff----?? Geotech? (sonar, x-ray, resistivity?) I'm sure others here will have the expertise and experience of temperature differentials etc. to advise whether heat detection is viable through this depth, and in what conditions.
I also noted a few other observations;
1. All the faces on the West side of the quarry show signs of excessive shattering, this is often an indication of charging explosives into a non-solid void, causing uncontrolled blasting, as evidenced by a number of glacial filled cavities in this area, this is also noticeable to the West end of the top terrace of the Northern face, (Sidetrack terrace), I doubt that these would yield much length or depth but maybe some worthwhile decorations, in fact, if you look closely at some of the clay-filled orifices in the West face, there are some atmospherically deteriorated formations visible.
2. Most of the cave development on the North and South of the backfilled bench is rift developement ( also akin to Nettle, Eldon
et.al).
3. A lot of water seepage about halfway up the bottom face of the Northern side, this appears to be displaced between Sidetrack and Petras, need to determine which developement horizon this is on, maybe the Flats in Nettle? -- research needed, also, how does this relate to Eldon & Giants/P8??.
4. Water seems to disappear, evidence of sygnificant drainage from the small grain gravel heaps at the Western end and various beddings around the quarry, has anyone noticed variations in the level of the mere in the East end? (This suggests that if it is found, digging in backfilled small gravel that has been washed in will be required).
5. A noticeable inconsistency in the vegetation and levelness in the area of the 'red circle' on my map. I would be loathe to suggest anything until further research is carried out.
They are my observations, that is what it is, comments please? we buried my chief mentor last week, and I'm missing him like h*ll, anyone like to take on the role?
Its a great pity Prof. T.D.Ford is unable to provide more protege's ------
P.S., apologies for the longevity, but I hope someone will read it through and add something constructive.