Peak District GeoWalk
- Thread starter pwhole
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Mrs Trellis
Well-known member
Gutted about the Speedwell vent. Hmmmmm. Mind you it makes thingy's anomaly rather more interesting n'est-ce pas?
Pitlamp
Well-known member
Glanced through a couple of those; they're really well produced.
I wonder if Dr.TDF would have agreed with that interpretation of the Speedwell Vent? The explanation of it in that particular walk begs the question as to why the whole of the volcanic outcrop is "brecciated" if the surrounding rocks aren't. Rocks are usually brecciated as a result of being within a fault zone, in which case outcrops of brecciated rock are usually linear. It also begs the question as to where the vent which supplied these volcanic rocks is actually to be found.
(I must do a bit of reading up about this one, when I get time.)
I wonder if Dr.TDF would have agreed with that interpretation of the Speedwell Vent? The explanation of it in that particular walk begs the question as to why the whole of the volcanic outcrop is "brecciated" if the surrounding rocks aren't. Rocks are usually brecciated as a result of being within a fault zone, in which case outcrops of brecciated rock are usually linear. It also begs the question as to where the vent which supplied these volcanic rocks is actually to be found.
(I must do a bit of reading up about this one, when I get time.)
pwhole
Well-known member
Don't be sure about the Speedwell Vent - a few of us from the TSG helped Mark Harwood of Terra Dat do some detailed sub-surface scanning of the vent and associated veins a few years ago, and then extended it for a work-experience student's MSc thesis later on - his scans are documented in TSG 19, and produced quite convincing (but only partial) evidence that it is indeed a vent, and not a lava flow. Nathalia's project backed that up - we also found an interesting void under Middle Bank, but it's Duchy land so I don't hold out much hope of a dig.
I'm hoping to meet up with Mark in a few weeks to discuss this further, and show him some other very interesting things - like some tuff from a completely unmapped outcrop, and not in the usual area. Top one is Pindale Tuff, bottom one is the new one - it's darker, harder and heavier and has far more bubbles and inclusions but less of the 'cat dirt' structure. Sorry for the shitty photo but it was just off my phone.
I'm hoping to meet up with Mark in a few weeks to discuss this further, and show him some other very interesting things - like some tuff from a completely unmapped outcrop, and not in the usual area. Top one is Pindale Tuff, bottom one is the new one - it's darker, harder and heavier and has far more bubbles and inclusions but less of the 'cat dirt' structure. Sorry for the shitty photo but it was just off my phone.
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