Underwater stalactites in the Dales

[Pitlamp]

There's a thread on the message board on the Cave Diving Group website where we're asking anyone who comes across underwater speleothems to post details. The aim is to establish a list of all those known. (This is in the wake of our discovering submerged stals at depths of up to 7.2 metres in Keld Head in recent years.)

Obviously most readers of this forum aren't divers but you might be involved in siphoning or pumping projects. If you do come across any stals in normally underwater passages the best thing to do would be to note it on the thread on the CDG site. If you have any problems finding that then a note here would be very much appreciated.

 

[SamT]

I assume you mean stal that is presumed to have formed in the dry - and then been submerged at a later date....

as opposed to gour/frond/crystal/pearl type formations formed in static sumps.

 

[Pitlamp]

That's right Sam - yer normal stalactites / stalagmites / flowstones etc. If they're in a sump they must have grown before the passage became flooded.

What sparked our interest was the flowstones which turned up in Keld Head down to 7.2 m depth. This means that huge lengths of the mighty Keld Head underwater system were once dry. We dated this flowstone (just under 90,000 years old, which is before the main Devensian ice advance). This means that before the last glaciation the valley floor in Kingsdale was at least 7.2 m deeper than it is today. Keld Head would have been a walk in entrance which would have provided an easy and impressive stroll for a quarter of a mile to a huge sump pool. From here the dive through to Kingsdale Master Cave would have been in the region of only 600 m to 700 m. ALL of the passages in the downstream Kingsdale Master Cave sump would have been dry as well. Much of the Marble Steps Branch would have been an open streamway. (In fact the latter contains what look like vadose features in places.)

Furthermore, just inside the entrance to Keld Head there is a rock floor at around - 4.5 m. Because the water level was well below this lip for long enough for substantial flowstones to grow, there must have been another resurgence elsewhere in Kingsdale, leaving what we know as Keld Head today completely dry. (This would have been similar to Sleets Gill Cave for example, now drained by the immature Moss Beck Head.) The reason that the water level has risen to its present level is almost certainly the terminal moraine (Raven Ray) down valley from Keld Head, which dammed up a post glacial lake - which then got filled up with sediment. The postulated alternative resurgence is now buried in the lake deposits and can't be identified (unless future exploratory work by diving reveals another relict outlet at the correct level).

If you look at the various posts on the CDG message board about this you'll find that the Kingsdale situation seems to be unique. However, just by dating one flowstone we've learned a huge amount about the glacial history of Kingsdale. This is why we're asking people to report any further sightings of underwater formations. They are of great interest!

(By the way, regular readers of Cave & Karst Science will be aware of a couple of recent papers on the above - but I thought it might be worth outlining the main points here as maybe some readers of this forum aren't familiar with this work.)

 

[graham]

If you look at the various posts on the CDG message board about this you'll find that the Kingsdale situation seems to be unique.

Unique in what sense?

 

[Fulk]

Time to hire a JCB and get digging?

 

[Pitlamp]

Graham - by "seems to be unique" I meant that it's the only example (at least which I'm familiar with) where we have a major underwater cave system in the Dales which has ancient submerged flowstone because the cave is now flooded due to a terminal moraine producing a lake, in which sediments were deposited - raising the "water table" (if I dare use that expression without inviting long discussion!).

Part of the reason for asking for input from as many cavers as possible is to try and find whether the assertion of uniqueness is actually true or not. I may well be wrong - but let's find out!

 

[graham]

OK, John, thanks.

Have you tried to consider the problem the other way round by looking at a map of glacial sediments and associated risings?

 

[Pitlamp]

An interesting suggestion Graham (as indeed most of yours are!).

I've not pursued it in this way - but I'm very familiar with the majority of our major resurgences and (unlike Keld Head) most are at or very near the lower Palaeozoic basement, so I'd not expect to find deeply submerged stals in the underwater caves behind these resurgences. Interestingly, one respondent on the CDG site saw something which looked like a stal curtain at - 21 m in Joint Hole. This is part of the underwater system behind God' Bridge Rising in Chapel-le-Dale, which is virtually on the basement. This feature may have been a rib of mineral though; we need to look at it again some time.

 

[molerat]

Does this mean the KMC resurgence has been

1. Valley Entrance
2. Keld Head
3. A now-blocked lower resurgence, then
4. Keld Head again

or am I getting myself confused?

 

[Pitlamp]

That's right - but even that's a simplification. There's an unidentified truncated and buried resurgence which was fed (updip) from Carrot Passage. There's also a large relict outlet tunnel called the Blue Sump which goes off partway along the KMC to KH through dive - this fed another truncated (and also buried) resurgence in the riverbed not far down valley from the Braida Garth track. Oh - and of course there's the Black Rose tunnel in the roof of the Master Cave; the destination of that is anybody's guess. Oh - there's also a cobble spill in partway around Wooding's Loop near the downstream end of the Keld Head complex, which probably represents yet another relict outlet.

 

[Pitlamp]

It's just dawned on me that the thread on the CDG message board where folk can contribute notes about seeing stals from sumps is part of the CDG only area. So if anyone does want to report anything, perhaps you could do it here or maybe send me a PM?

Thanks.

 

[gus horsley]

Does the presence of underwater stals in Keld Head indicate that the phreatic waters are saturated with calcium carbonate?  Otherwise I would have thought they would have dissolved over a period of time due to the acidic nature of the water.  Perhaps there are other resurgences which once contained underwater stals which have now disappeared.

 

[Fulk]

Does the presence of underwater stals in Keld Head indicate that the phreatic waters are saturated with calcium carbonate?  Otherwise I would have thought they would have dissolved over a period of time due to the acidic nature of the water.  Perhaps there are other resurgences which once contained underwater stals which have now disappeared.

A very interesting point. If stal has disappeared from resurgences, would this imply that stal is more susceptible to solution than cave walls are? Maybe because stal is a purer form of calcite than bedrock?

 

[graham]

Does the presence of underwater stals in Keld Head indicate that the phreatic waters are saturated with calcium carbonate?  Otherwise I would have thought they would have dissolved over a period of time due to the acidic nature of the water.  Perhaps there are other resurgences which once contained underwater stals which have now disappeared.

A very interesting point. If stal has disappeared from resurgences, would this imply that stal is more susceptible to solution than cave walls are? Maybe because stal is a purer form of calcite than bedrock?

I can think of caves in France where there is stal that has most certainly been redissolved presumably during a submerged phase. But why would stal necessarily be more or less susceptible than limestone? Surely such variations will occur from place to place depending on the micromorphology of the particular piece of rock or stal.

In any event, there is a simple way to test the state of the water in Keld Head, requiring a sample of water and a titration.

 

[Pitlamp]

I think you can rest assured that the water in there is chemically aggressive. Yes, the stal shows signs of being redissolved but there's enough of it left (fortunately) so that it can be recognised for what it is.

 

[TheBitterEnd]

Just to add to the above, limestone, like most rocks is a mixture of things and the extent of impurities affects the solubility. As an extreme example Ford and Williams state that "argillaceous limestones with 20-30% clay/silt form little karst" (sect 2.6.1, p28, Karst Hydrogeology and Geomorphology). Stals on the other hand are probably less likely to entrain impurities and so could be more soluble.

 

[graham]

Just to add to the above, limestone, like most rocks is a mixture of things and the extent of impurities affects the solubility. As an extreme example Ford and Williams state that "argillaceous limestones with 20-30% clay/silt form little karst" (sect 2.6.1, p28, Karst Hydrogeology and Geomorphology). Stals on the other hand are probably less likely to entrain impurities and so could be more soluble.

Not necessarily so. Here are some examples of stalagmites with all sorts of interesting impurities.

 

[Fulk]

Well, BitterEnd did say:

Stals on the other hand are probably less likely to entrain impurities and so could be more soluble.

Maybe they could dissolve more easily simply because they stick out ?  ?

 

[graham]

Well, BitterEnd did say:

Stals on the other hand are probably less likely to entrain impurities and so could be more soluble.

Maybe they could dissolve more easily simply because they stick out ?  ?

Yes

For two reasons: firstly that means that the piece of calcite under question will be showing a greater surface area relative to its volume to the water. Secondly, turbulent waters and those containing suspended solids will be more likely to knock bits off. Abrasion and corrasion are certainly as important as solution, if not more so, in enlarging cave passages.

 

[Fulk]

I don't doubt that abrasion and corrasion are very important under vadose conditions ? but what about phreatic conditions?