UKC

Climbed on the Long Wall area of HH today. There are lots of excellent hidden finger jugs and small positive holds that seem almost stuck on (but are very solid and enjoyable to pull on). They resemble crystalline intrusions but are exactly the same colour and texture as the surrounding fairly blank rock (and I didn't think you could get intrusions into sedimentary rock). Anyone know how they were formed?

In reply to Sam Beaton:

Anyone?

In reply to Sam Beaton:

Got a picture?- I've never been

In reply to wbo2:

Sorry, no

In reply to Sam Beaton:

It's limestone isn't it?  Limestone concretions are a thing...

"Concretions are masses of mineral matter embedded within rock layers, including limestone, sandstone, and shale. They often take shape when minerals precipitating (settling) out of water collect around a nucleus, such as a pebble, leaf, shell, bone, or fossil."

In reply to Sam Beaton:

Don't know Harpur Hill sorry and not certain as to your excellent edge holds, but with limestone and other sedimentary rocks you most certainly get other stuff sneaking in there too 😉.

Usually a bloomin' great crack/fault in the limestone or in the weakness of a bedding plane some hot stuff, often hot and wet stuff got squished through the gap and then solidified. Examples of solidified stuff include Galena/lead ore and fluor Spar  (there's a lot of lead/fluor mines up Buxton way), but other minerals can cohabit with lead, such as Zinc (blende), iron ore (siderite mostly in UK and that's a sort of iron carbonate so an irony variant of limestone).

Plus look about the peak limestone and there plenty of examples of naughty intrusions of lava here and there, thinking of a few in Castleton just off the top of my head but maybe some in Buxton too?. The old Peak miners gave name some forms of igneous intrusions in limestone the name "toadstone".

Also, not an intrusion like lava, but because limestone, mudstone and shale were ancient sea beds, there's a lot is stuff in that water that precipitated out, usually in discrete layers and also sometimes as lumps/nodules or crystals. Chert especially which is a silica rich sediment, it is usually black and hard and sharp and commonly in layers in limestone, you sometimes see bands of nodules in chalk where it is really hard and  gets called flint (flint is excellent at cutting ropes, beware).

While crawling/wading about underground underneath a lot of limestone on Saturday I even saw some lumps of coal in one spot, although that was in the Y Dales not Peak but mentioning as all sorts of stuff can be mixed up between the layers of limestone series.

I'd hazard a guess your solid holds are bits of chert in the limestone, but happy to defer to someone with local knowledge 

In reply to Sam Beaton:Wen quarried they hit a fault line of Corel intrusions and Long wall and perched block are  prime examples of this prime examples and more on the upper tier but some routes like Corel seas are ruined by people thinking this is top 50 and can’t think of other better routes sadly 

In reply to Sam Beaton:

The bedrock unit is Bee Low limestone with some influence from the Lower Miller's Dale Lava Member formation around that area. BGS suggests from thermal interaction between the limestone and the basalt unit. 

Limestone-
https://webapps.bgs.ac.uk/lexicon/lexicon.cfm?pub=BLL
Olivine basalt-
https://webapps.bgs.ac.uk/lexicon/lexicon.cfm?pub=LMB

In reply to CantClimbTom:

There's a cherty band on Portland (very visible (and sharp...) at Cheyne Weares), but that tends to be black, so not the same colour as OP described.

Calcite growths within the limestone are a possibility, and would be closer to the colour of the limestone.

In reply to Sam Beaton:

Just looking through the responses so far:

- There are igneous intrusions in the area but they do not form holds on the limestone of the crag, here or anywhere in the peak that I've seen

- Silicified corals or other macrofossils form small sticking out holds on some peak lime crags (e.g. Fossil Wall in Taddington Dale), but I don't recall seeing this to any notable extent at Harpur Hill

- Chert nodules certainly form sticking out holds on some peak limestone crags, notably around Matlock and Stoney. The Bee Low limestone is not very cherty though https://webapps.bgs.ac.uk/lexicon/lexicon.cfm?pub=BLL 

- Crystaline minerals - The surface colour of the rock is mostly due to organic matter and dirt so crystaline holds might sometimes be hard to distinguish from base limestone holds

Another possibility is brecciated limestone. This is where fragments of limestone eroded off the main mass and gather in voids within the rock and then get cemented together and back onto the main mass with stalactite/tufa material. It's basically conglomerate on a small scale. These often form good finger holds which look like random lumps of limestone stuck onto the face.

It would be easy enough to answer the question with a few photos.

In reply to Sam Beaton: There will be plenty of fluids moving thro' the rock, and given there's not shortage of CaCO3 some recrystallisation , growth of nodules will occur , particularly along faults, fractures, but elsewhere in the matrix of the rock as well. These sorts of nodular growths might be what you're looking at

And , yes, you can get intrusions into sedimentary rocks, both volcanics and more interestingly also remobilised sediments.  Last time I went to Annot it was to look at soft sediment injectites

In reply to Sam Beaton:

Some interesting answers here, thanks.

They definitely aren't large scale intrusions, such as the basalt dykes within the gabbro in the Cuillin.

I'm pretty sure they're not chert, if the juggy white holds on Chert Wall at Moss Rake are indeed chert.

Concretions or brecciated limestone seem like the most likely candidates.

Yes, I wish I'd taken some photos now!

In reply to Gary Gibson:

Gary, I can't think of a better f6a on Peak lime, it's certainly the best f6a at Harper Hill!

In reply to galpinos:

I'm with Gary, it was a 3 star route 15 years ago, it's now worn out

In reply to Sam Beaton:

In what way? I last climbed it a couple of years ago. It was a bit polished but "worn out" seems a bit strong?

In reply to Sam Beaton:

I thought it was worth  1 star 20 odd years ago and after doing it again last year the same! 

In reply to galpinos:I saw over 30 people top roping it the other week really odd when perched block is way better 

likewise with cairn which is desperately over polished 

In reply to Gary Gibson:

I agree Gary: how can anything at Harpur Hill be top 50? Outrageous. 

In reply to Sam Beaton:I should know I we completely rebolted it out of our own money