The Old Ruminator
Well-known member
Some uneducated random thoughts.
The marks on the rock and clay washout at both digs suggest fast downward water flow of fairly short duration probably at the time when Robert et al were inwashed.( 40.000 years ago ). It was a period of significant climate instability, swinging between cold "stadials" and brief warmer "interstadials. There would have been no stalagmite deposition during a permafrost stage. The permafrost accounted for the cryogenic features we see in many Mendip caves. Clearly both dig sites were much larger voids centred on the N - S Joint and strike structures. Optimistically one could assume that both are related and interconnect further south ( or lower ) past the strike structure that we are now in. The current strike structure is thickly bedded Clifton Down Limestone giving us large detached bedding breakdown.( dark and spintery ). Actually the next series The Burrington Oolite (Burrington Combe, Burrington, Unit is 210m thick and comprises oolitic and crinoidal limestone formed in shallow tropical seas 345 million years ago. ) is only a short distance ahead to the south. That will have differant morphological features and breakdown properties but for the better or worse for us I dont know.
Unlike Snare Hole and other lost quarry voids QWUH and HWUH is a proper cave " system " so clearly of some significance when related to the catchment and Fairy Cave horizon. There was capture along strike to West Chamber in Withyhill possibly relating to a stage horizon in the catchment. There could also have been a connection via HWUH to the lost section of the Withyhill conduit at an earlier stage. In any case the whole system has its origins in the phreas. We have to imagine then that the current erosion surface was at a very much higher level than it is now. Long before the hanging valleys in the escarpment and the lowering of the Mells valley reducing the catchment by %50 were formed. Parts of the system like Shatter and Withyhill have been unroofed and lost by surface erosion. Its significant to see that none of the fossil systems exist in the Black Rock Limestone itself partly buried by solufluction deposit called Head. The Head deposit now acts as an impermeable catchment for the relatively modern stream sinks at Midway and Blakes Farm. Any thoughts of large relict or active streamways below quarry floor level is misguided. Most will be post Head deposition and largely vadose with little phreatic input. The present relict Phreatic/Vadose conduits ie Shatter, Withyhill etc formed over hundreds of thousands of years maybe dating in origin prior to the Hoxnian Interglacial/Interstadials 400,000 years ago. Anything below quarry level in geologcal terms would be " recent "and almost entirely vadose in nature. Thats where FCQ does not follow the classic Mendip pattern of deep phreatic looping.
The marks on the rock and clay washout at both digs suggest fast downward water flow of fairly short duration probably at the time when Robert et al were inwashed.( 40.000 years ago ). It was a period of significant climate instability, swinging between cold "stadials" and brief warmer "interstadials. There would have been no stalagmite deposition during a permafrost stage. The permafrost accounted for the cryogenic features we see in many Mendip caves. Clearly both dig sites were much larger voids centred on the N - S Joint and strike structures. Optimistically one could assume that both are related and interconnect further south ( or lower ) past the strike structure that we are now in. The current strike structure is thickly bedded Clifton Down Limestone giving us large detached bedding breakdown.( dark and spintery ). Actually the next series The Burrington Oolite (Burrington Combe, Burrington, Unit is 210m thick and comprises oolitic and crinoidal limestone formed in shallow tropical seas 345 million years ago. ) is only a short distance ahead to the south. That will have differant morphological features and breakdown properties but for the better or worse for us I dont know.
Unlike Snare Hole and other lost quarry voids QWUH and HWUH is a proper cave " system " so clearly of some significance when related to the catchment and Fairy Cave horizon. There was capture along strike to West Chamber in Withyhill possibly relating to a stage horizon in the catchment. There could also have been a connection via HWUH to the lost section of the Withyhill conduit at an earlier stage. In any case the whole system has its origins in the phreas. We have to imagine then that the current erosion surface was at a very much higher level than it is now. Long before the hanging valleys in the escarpment and the lowering of the Mells valley reducing the catchment by %50 were formed. Parts of the system like Shatter and Withyhill have been unroofed and lost by surface erosion. Its significant to see that none of the fossil systems exist in the Black Rock Limestone itself partly buried by solufluction deposit called Head. The Head deposit now acts as an impermeable catchment for the relatively modern stream sinks at Midway and Blakes Farm. Any thoughts of large relict or active streamways below quarry floor level is misguided. Most will be post Head deposition and largely vadose with little phreatic input. The present relict Phreatic/Vadose conduits ie Shatter, Withyhill etc formed over hundreds of thousands of years maybe dating in origin prior to the Hoxnian Interglacial/Interstadials 400,000 years ago. Anything below quarry level in geologcal terms would be " recent "and almost entirely vadose in nature. Thats where FCQ does not follow the classic Mendip pattern of deep phreatic looping.
