Pitlamp
Well-known member
Anyone with no special interest in the fine details of the Great Scar Limestone depositional sequence in the Yorkshire Dales - stop reading now!
However, for those few who are interested . . . .
Three or four years ago there was a BCRA field day, based on the Porcellanous Bed of limestone, famously seen in Gaping Gill. We met at Ingleton in the Community Centre for a morning of presentations, then split into two groups to view the PB in Crummackdale and Kingsdale. I was involved in planning for that day and we specifically scheduled to meet up again in the afternoon so that arrangements could be made for anyone interested to do follow up work and map the PB elsewhere in the Dales and / or look for it underground.
Unfortunately this all went pear shaped, because (with no prior warning and despite our booking having been made well in advance) we were asked not to reassemble at the community centre in the late afternoon, due to an event. This is a great shame because that was really the most important part of the whole initiative to bring people together. Everyone drifted away and, apart from a small number of individuals who are still quietly working on mapping the PB, we still have no co-ordinated collective effort to arrive at a better understanding of how the PB influences cave development and whether its outcrop might lead us to discover more caves. This was a great opportunity missed.
Since then, two further things have happened which should make possible the resumption of this work. Firstly, Tony Waltham and Deej Lowe produced their fabulous Part 2 of their "Caves & Karst of the Yorkshire Dales", book which has many references to the PB at the boundary between the Cove and Gordale limestones. Secondly, the owners of this website have provided this area for BCRA to use as a forum (thank you!).
Thus we can now communicate easily and so we perhaps have the opportunity to get this project off the back burner again.
What's prompted me to post this is that I found a very thick bed of porcellanous limestone in Jingle Pot last week. (I'll ask Badlad or Pegasus if they'll post an image of a specimen for me; I still find posting photos a bit of a challenge I'm afraid :-[) This is from just above water level at the base of Jingle Pot's entrance shaft.
The 64,000 dollar question is whether it's one of the other porcellanous beds known to exist in the Great Scar limestone, or the main Porcellanous Bed (of GG fame, at the top of the Cove limestone - but absent at Malham, note). This latter bed outcrops outside the entrance of Midge Hole, further down valley from Jingle Pot. But the dip is up-dale and steeper than the normal regional dip, so the GG PB "should" be at least 40 m to 50 m below water level at Jingle Pot. (A glance at the useful elevation on page 381 in Part 2 of the Caves & Karst book reveals this - bear in mind though that this was the best possible interpretation at the time of publication and may need to be revised in light of future observations.)
The possible existence of the main PB in Jingle Pot (as opposed to a different pb) can't be ruled out with the knowledge currently available - between Midge Hole and Jingle Pot there are numerous fairly major faults crossing the dale, which collectively could account for significant displacement. This would be unusual but the possibility has to be borne in mind. All we know as I type is that there is a thick PB outside Midge and a very similar thick pb (or "PB?") some 15 m below the riverbed at Jingle Pot.
One test of this might be whether the Jingle Pot pb can be found at surface exposure in the dry riverbed down valley from Jingle Pot. So if anyone happens to be in that area, do please keep your eyes open for it.
As mentioned above, certain noteworthy individuals continue to search for and find the PB elsewhere in the Dales. Please could you consider adding notes of your findings here? This would then develop a single point of reference, which could grow into a valuable resource.
Thanks.
However, for those few who are interested . . . .
Three or four years ago there was a BCRA field day, based on the Porcellanous Bed of limestone, famously seen in Gaping Gill. We met at Ingleton in the Community Centre for a morning of presentations, then split into two groups to view the PB in Crummackdale and Kingsdale. I was involved in planning for that day and we specifically scheduled to meet up again in the afternoon so that arrangements could be made for anyone interested to do follow up work and map the PB elsewhere in the Dales and / or look for it underground.
Unfortunately this all went pear shaped, because (with no prior warning and despite our booking having been made well in advance) we were asked not to reassemble at the community centre in the late afternoon, due to an event. This is a great shame because that was really the most important part of the whole initiative to bring people together. Everyone drifted away and, apart from a small number of individuals who are still quietly working on mapping the PB, we still have no co-ordinated collective effort to arrive at a better understanding of how the PB influences cave development and whether its outcrop might lead us to discover more caves. This was a great opportunity missed.
Since then, two further things have happened which should make possible the resumption of this work. Firstly, Tony Waltham and Deej Lowe produced their fabulous Part 2 of their "Caves & Karst of the Yorkshire Dales", book which has many references to the PB at the boundary between the Cove and Gordale limestones. Secondly, the owners of this website have provided this area for BCRA to use as a forum (thank you!).
Thus we can now communicate easily and so we perhaps have the opportunity to get this project off the back burner again.
What's prompted me to post this is that I found a very thick bed of porcellanous limestone in Jingle Pot last week. (I'll ask Badlad or Pegasus if they'll post an image of a specimen for me; I still find posting photos a bit of a challenge I'm afraid :-[) This is from just above water level at the base of Jingle Pot's entrance shaft.
The 64,000 dollar question is whether it's one of the other porcellanous beds known to exist in the Great Scar limestone, or the main Porcellanous Bed (of GG fame, at the top of the Cove limestone - but absent at Malham, note). This latter bed outcrops outside the entrance of Midge Hole, further down valley from Jingle Pot. But the dip is up-dale and steeper than the normal regional dip, so the GG PB "should" be at least 40 m to 50 m below water level at Jingle Pot. (A glance at the useful elevation on page 381 in Part 2 of the Caves & Karst book reveals this - bear in mind though that this was the best possible interpretation at the time of publication and may need to be revised in light of future observations.)
The possible existence of the main PB in Jingle Pot (as opposed to a different pb) can't be ruled out with the knowledge currently available - between Midge Hole and Jingle Pot there are numerous fairly major faults crossing the dale, which collectively could account for significant displacement. This would be unusual but the possibility has to be borne in mind. All we know as I type is that there is a thick PB outside Midge and a very similar thick pb (or "PB?") some 15 m below the riverbed at Jingle Pot.
One test of this might be whether the Jingle Pot pb can be found at surface exposure in the dry riverbed down valley from Jingle Pot. So if anyone happens to be in that area, do please keep your eyes open for it.
As mentioned above, certain noteworthy individuals continue to search for and find the PB elsewhere in the Dales. Please could you consider adding notes of your findings here? This would then develop a single point of reference, which could grow into a valuable resource.
Thanks.