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Hallowe'en Rift, Mendip Hills

Excursions [and other notes] involved in the exploration of Hallowe'en Rift; a cave, so far, formed within Triassic Dolomitic Conglomerate.

The exploration of Hallowe'en Rift was started in 1982 by Trevor Hughes with other members of the Bristol Exploration Club, then during the early 1990's Vince Simmonds and other, mostly, local diggers were active at a number of locations within the cave, including the start of the dig to the 'east' side of the entrance, leading to An Unexpected Development in August 2018, with Graham Johnson in December 1991. The current phase of exploration was commenced in 2009, with the majority of the early work being carried out by Vince Simmonds and Alex Gee, now the regular team also includes Rob 'Tav' Taviner, Graham 'Jake' Johnson, Nick Hawkes, Jonathon Riley, Paul 'Brockers' Brock, Roz Simmonds, Duncan Price and Mike Moxon. There has been occasional help from others including Matt Tuck, Mike Willett, John 'Tangent' Williams, Pete Bolt, Bob Smith, Callum and Hazel Simmonds, and several appearances by that well-known antipodean, Ray Deasy.

There have been visits from some notable experts in their various fields including: Charlie Self, Andy Farrant, Christopher Smith, Derek Ford, Joyce Lundberg, Don MacFarlane, Marc Luetscher and Gina Moseley. All have added to a better understanding of Hallowe'en Rift.

7th October 2019

notes Posted on Tue, October 08, 2019 06:27:26

Vince, Estelle Sandford and James Begley.

A trip to An Unexpected Development (AUD) followed by a tour around the rest of the cave. There were a few puddles of water along the way to AUD including a pond at the ‘dig’ in the lowest point in the rift. That was a surprise. Looking up the rift, thought to myself “really ought to finish that climb!”.

I had brought along my 100 LED 395nm UV torch to try out in parts of AUD. However, that turned out to be disappointing as the torch had turned ‘on’ inside my bag so the batteries were depleted – will have to try harder next time!

UV illumination.

There was a pool of water in the low crawl into Trick or Treat so that became well lubricated. Toil and Trouble somehow appeared shorter but that must be in the mind only. In the Cold Gnarly North there is a bit more water in the ‘lake’ than there was on Saturday. The dig is still dry and there was a good detectable movement of air noted.

I think the guests enjoyed the trip.

Back again tomorrow. Might find some clean [and dry] kit for that trip!



Apologies!

notes Posted on Wed, July 31, 2019 05:57:58

My apologies to all on the appearance of some of the posts. This blog and others have all been migrated to WordPress, in the process the layout has been lost. All wholly unsatisfactory! I haven’t had the time to edit it all yet.



14th June 2019

notes Posted on Fri, June 14, 2019 05:52:10

Notes by Vince.

Just after the breakthrough into An Unexpected Development in August 2018, we’d had a discussion regarding the possible origins of the cave system along with other geomorphological processes and events, i.e. Pleistocene
frost and ice damage. At the time I started to put together the following
notes:

Notes on geomorphology. Is there a hypogenic origin for Hallowe’en Rift?

Cave development can occur in deep-seated conditions, without direct recharge from the surface, by recharge to the cave-forming zone coming
from depth. This type of speleogenesis is termed hypogenic (or hypogene).
The concept of hypogene speleogenesis does not necessarily mean cave
development at great depth but refers to the origin of the cave-forming agency from depth. Hypogene speleogenesis is defined as the formation of
solution-enlarged permeability structures by water that recharges the cavernous zone from below, independent of recharge from the overlying or immediately adjacent surface.

The following elementary cave patterns are typical (although not necessarily exclusive) for hypogene speleogenesis:

· Single passages or rudimentary networks of passages;

· Cavernous edging along transverse hypogene conduits;

· Network maze;

· Sponge-work maze;

· Irregular isolated chambers;

· Rising, steeply inclined passages or shafts;

· Collapse shafts over large hypogenic voids and breccia pipes.

Network maze caves of hypogene origin are known in limestones, dolomites and gypsum, in mixed limestone-dolomite-gypsum strata, and in
conglomerates. A common feature of network mazes is a very high passage
density.

Rising, steeply inclined passages or shafts are outlets of deep hypogene systems in which the “root” structure remains unknown in most cases.
Possibly formed by rising thermal waters charged with CO2 and H2S.

Composite 3D systems are comprised of various elementary patterns
at different levels, such as irregular chambers, clusters of network or
sponge-work mazes and rising, subvertical conduits and other morphs connecting them.

Hypogenic features may become relict but still, remain within
contemporary systems, for example, in a system where original confinement was breached and the flow pattern reversed from upwelling to descending (Klimchouk, 2012).

Ref: Alexander Klimchouk. Speleogenesis, Hypogenic in The Encyclopaedia of Caves. Elsevier, 2012, p748-765

Nick made the following comments (first reported 21/08/2018):

“The polished nature of the dolomitic conglomerates was noted throughout most of the cave with hard limestone/dolomitic pebbles and crystalline red marl matrix having been eroded equally. This erosion pattern is in marked contrast to the dolomitic conglomerates in Home Close where the softer matrix is eroded preferentially compared to the limestone pebbles that stick out as knobbly lumps. The polished erosion pattern is consistent with a base of a streamway or a passage full of water as opposed to slow dripping of water. As similar polished conglomerates are clearly seen down the new pitch, as well as in the roofs of the horizontal passages which are phreatic in shape and have well developed scalloping, the logical conclusion is that water that initially formed the pitch was upward flowing. Undoubtedly there has been a limited amount of inflow from above later in the history of this cave’s development but it is relatively insignificant in terms of passage dimensions although highly significant for the development of the formations.”

Duncan and Tav also made some valid comments noted while carrying out
a survey of the cave.

These thoughts might be more salient following a recent paper by
Smart and McArdle published in the UBSS Proceedings Volume 28 (1) 2019,
p65-102, suggesting a hypogenic origin for Denny’s Hole.

It is obvious that further investigation and research is required.



Uranium-series dates

notes Posted on Sun, January 27, 2019 12:00:10

Thanks to Gina Moseley we have some more dates on speleothems sampled from Hallowe’en Rift.

230TH Age (yr BP) Corrected

HR1-T 215,221 +/- 2476
HR1-B 219,378 +/- 2429 correlates with MIS7
HR2-T 125,341 +/- 1532
HR2-B 126,834 +/- 2197 correlates with MIS5e

BP stands for “Before Present” where the “Present” is defined as the year AD 1950.



Frost and Ice at Hallowe’en

notes Posted on Thu, November 29, 2018 14:37:13

Published in December’s issue of Descent, 2018.



Rock of the day

notes Posted on Sun, January 14, 2018 12:54:35

Found last weekend during digging activities by Jonathon, another cobble of lias, with striations etched out along laminations and cleavage (?).

This weekend, Brockers recovered this fragmented stalagmite from within the sediment as digging progressed. The cave must have been open a long time for this to form. The image above was taken with LED illumination, the one below using subdued flash.



It’s that time of year!

notes Posted on Sat, December 24, 2016 07:36:56

Card design by A.G’ruffalo.



Flowstones

notes Posted on Sun, July 24, 2016 10:44:14

24th July 2016:

Sunday morning and the dog needed a walk so decided that I would go over to Hallowe’en Rift and get the lump of flowstone that I had left there. Parked at the end of Dursdon Drove and walked along the hilltop at Rookham before crossing fields down to Hallowe’en Rift. At the cave I took some photographs, put the lump of flowstone into my bag before spending a few minutes placing some more stones onto the retaining wall.

As previously mentioned (23/07/2016 entry) after splitting a lump of flowstone yesterday another older speleothem was revealed encased within it, as is clearly seen in the image below.


The other lump of flowstone also reveals an older speleothem. Just to the right of centre the remains of a small stalagmite ‘boss’ can be seen below successive layers of flowstone.


Both these remnants of flowstone have been recovered from the sediments removed from the ongoing dig at the end of Merlin’s Magic Milk Parlour. It would be interesting to get these dated to establish whether the ages are similar to the dates from previous samples.



Diggy, Diggy Hole

notes Posted on Sun, March 13, 2016 08:38:26

Here is a video clip about digging to amuse you, it made me smile anyway. WARNING: this video contains an earworm!

It’s not a theme song for the team working at Hallowe’en Rift as Jake and Alex are both far too tall.



11th January 2016

notes Posted on Tue, January 12, 2016 06:20:13

An evening stroll up to Hallowe’en Rift with Don McFarlane and Joyce Lundberg who are interested in carrying out some more stal dating on material from the cave. They weren’t dressed for an underground trip and seemed content to pick over the spoil heap for suitable material. I did venture down the shaft if only to get a hammer to break up some larger lumps of stal.

Don is Professor of Environmental Science at Claremont Colleges in California, USA; Joyce is Associate Professor at Carleton University, Ottawa, Canada.



29th and 30th August 2015

notes Posted on Mon, August 31, 2015 16:52:41

We have been playing away this weekend at Bleadon Cavern and Home Close Hole. Back next week!



29th and 30th August 2015

notes Posted on Mon, August 31, 2015 16:52:32

We have been playing away this weekend at Bleadon Cavern and Home Close Hole. Back next week!



Calcite

notes Posted on Wed, August 12, 2015 17:34:06


Decent calcite crystal that was recovered from blasted rock debris during the clearance work t’other day.



9th April 2015

notes Posted on Sat, April 11, 2015 06:45:38

Walked up the cave from the farm to deliver a couple of replacement skips ready for the team on Saturday.



25th October 2014

notes Posted on Sun, October 26, 2014 07:24:58

No digging today as the Hallowe’en Team went for an end of summer time tour to the west end of Mendip.


From left: Nick, Alex, Alan Gray (ACG) and Tav

Met up with the Axbridge Caving Group (ACG) diggers to have a look at their latest project and very interesting it is too. Had a great trip into Upper Canada where there appears to be some potential to extend beyond the known cave. Look forward to the presentation at Wells Museum on the 27th November.



Too much time on my hands?

notes Posted on Sat, July 05, 2014 17:32:31

Once upon a time at the
foot of a great mountain
There was a town where
the people known as Wookeyfolk lived,
Their very existence a
mystery to the rest of the world,
Obscured as it was by
great clouds.
Here, they played out
their peaceful lives,
Innocent of the litany
of excess and violence
That was growing in the
world below,
To live in harmony with
the spirit of the mountain called Mendip was enough.
Then, one day,
Strangefolk arrived in the town;
They came in ragged
caving clothes, hidden under hats,
But, no one noticed them,
they only saw shadows.
You see, without the
Truth of the eyes, the Wookeyfolk were blind.

In time, the Strangefolk
found their way into the high reaches of the mountain
And it was there that
they found caves of unimaginable sincerity and beauty.
By chance, they stumbled
upon the place where all the good souls come to rest.
The Strangefolk, they
coveted the jewels in these caves above all things
And soon they began to
dig into the mountain,
Its rich seam fuelling
the chaos of their own world.
Meanwhile, down in the
town, the Wookeyfolk slept restlessly
Their dreams invaded by
the shadowy figures digging away in the holes.
Every day, people would
wake and stare at the mountain,
Why was it bringing
curiosity into their lives?
And, as the Strangefolk
dug deeper and deeper into the mountain
Following a cold and
cheering draught that touched their very souls,
For the first time
The Wookeyfolk felt
cheerful.
For they knew that soon
that the mountain called Mendip would reveal its hidden secret.
And then came a sound,
distant at first
It grew into a cacophony
So immense it could be
heard far away in space
There were no screams,
there was no time,
The mountain called
Mendip had spoken; there was only wide open space,
And then, joy!

Adapted from ‘Fire
coming out of the Monkey’s Head’ on Demon Days by Gorillaz, written by Damon
Albarn and Jamie Hewlett. Released May 2005



Not one of ours!

notes Posted on Fri, June 13, 2014 21:44:30

3000-Year-Old Remains of Baby Found at Halloween’s
Birthplace

Jun 10, 2014 01:36 PM ET // by Rossella Lorenzi



Remains of a baby dating back to 3,000 years ago have been
found at a site in Ireland that is believed to be the birthplace of Halloween.

The fully intact skeleton, possibly belonging to a 7-10
month child, was unearthed during a three week excavation at Tlachtga, on the
Hill of Ward near Athboy Co. Meath.

One of Ireland’s most enigmatic sites, the Hill of Tlachtga
features impressive circular earthworks which are best seen from the air.
Medieval texts link the site to Samhain, the ancient Celtic Festival which is
the precursor to modern Halloween.

“We may never know what caused the death of the child. The
skeleton probably dates back 3,000 years and was found on the bedrock at the
base of a 1.5m (3-foot, 28-inch) ditch,” lead archaeologist Stephen Davis, at
University College Dublin, told the Irish Examiner.

Excavation and surveys carried out using airborne laser
revealed the area was a “key ritual site.”

“The site has several different phases of monumental
enclosures and we believe them to be associated with festivals and rituals
potentially dating back as far as 1,000 B.C.,” Davis said.

Sitting on top of the Hill of Ward, Tlachtga is a site
steeped in folklore. According to Irish mythology, it got its name from the
daughter of the powerful druid Mug Ruith. According to legend, the remains of
the druidess, who is said to have died on the hill after giving birth to
triplets, are buried there.

Tlachtga is also believed to be the site of the Great Fire
Festival in which sacrifices were offered to gods on Samhain eve. All hearth
fires throughout Ireland were extinguished and then lit again from a central
fire on the hill.

Meaning summer’s end, Samhain was a great festival of the
dead — a time when the doorways to the otherworld opened and journeys could be
made from one side to the other.

The veil between the worlds of the living and the dead was
believed to be the thinnest on Oct. 31, a day which lies exactly between the
autumnal equinox and the winter solstice.

The excavation revealed the monument of Tlachtga is actually
the last of at least three phases of enclosure on the hill.

“As a working model for the phases of construction, at least
one small enclosure, about 15 inches in diameter, was enclosed by a very large,
tri- or quadrivallate enclosure, about 650 feet in diameter, which was replaced
by the monument we see today,” the archaeologists said.

The excavations also brought to light evidence of burning,
which could have been ritual fires or the result of glass-making, Davis said.

He believes the child was most likely not the victim of any
human sacrifice on the ritual site.

The remains have been taken to the School of Archaeology at
University College Dublin for further examination.

Image: Tlachtga from the air. Credit: Excavations at Tlachtga via Facebook



Resolutions!

notes Posted on Mon, December 30, 2013 15:50:52

Thinking of a New Year’s resolution, this could be an inspirational thought for all cave diggers!

Onward to passages as yet undiscovered. Best of luck to all of you!



1st December 2013

notes Posted on Tue, December 03, 2013 20:52:58

Interesting discussion with Trevor Hughes at lunchtime in the Hunter’s. TH had his original survey of Hallowe’en Rift and had printed off a slightly blurred copy of the east side extensions. Although the scales didn’t quite match up we managed to overlay the two surveys to give an overall picture of how the cave trends, all that was missing is the dig started by ‘Quiet’ John Watson and continued by myself and Jake et al in the early 1990’s. When viewed in its entirety the full survey certainly appears to give some clear indications as to where efforts might be made in the future – almost too many leads!



30th November 2013

notes Posted on Sun, November 24, 2013 08:33:04

Won’t be digging today as I am off to a conference at the University of Reading – Towns of Roman Britain; some eminent speakers so should be good. It was!

Might go digging Sunday, will think about it. Didn’t dig, went over to Whitcombe’s Hole instead.



22nd November 2013

notes Posted on Sat, November 16, 2013 15:24:27


The survey of the east side extensions, total survey length 64 metres. Trevor Hughes 1982 [partial] survey to the west of the entrance is included.



Remember when it was dry!

notes Posted on Mon, May 06, 2013 21:27:19


Alex took this image on the day we dug along from Stal Bend to discover Witches Cauldron and, eventually Merlin’s beyond. Happy days!



26th February 2013

notes Posted on Tue, February 26, 2013 22:45:07

Unfortunately it’s been very quiet on the cave digging front over the last few weeks due to other weekend happenings [on my part, anyway], such as archaeological conferences and the continuing Stanton Drew Survey Project, this involves geophysical and other archaeological investigations of the environs surrounding the stone circle complex, this has taken up two long weekends.

We will get back to the task ahead in Hallowe’en Rift soon!



Bison priscus

notes Posted on Mon, July 30, 2012 17:40:37

This bone was found in the sediment in October 2011 along the left side of the tube (‘Toil and Trouble’) leading from the base of Witches Cauldron. Despite very careful scutiny of sediments no other bones have, since been uncovered.

A visit to the Wells and Mendip Museum to look at the collections displayed in the Balch Room led to a positive indentification of the bone as being from the foreleg of Bison priscus, the museum specimen is dated from the Pleistocene and was found at Milton Hill.

Higham, T. 2006. AMS 14C Dating of Ancient Bone Using Ultrafiltration gives dates for Bison priscus recovered from Banwell Bone Cave as 52,700 +/- 1900 14C age BP to >59,500 14C age BP and for Hunter’s Lodge Sink as >54,800 14C age BP.



4th April 2012

notes Posted on Thu, April 05, 2012 08:18:23

A trip with John ‘Tangent’ Williams who had expressed a desire to experience the delights of Hallowe’en Rift after listening to Alex and myself discussing the digging prospects on many occasions. A reasonably comprehensive tour around the original dig sites of the 1980s and 1990s before heading up to ‘Merlins’ and finally along the ‘tube’. Tangent appeared to be suitably impressed and enjoyed the trip. Haven’t been to the Hunter’s on a Wednesday evening, traditionally digger’s night, for quite a while, I was struck by how quiet it was, it used to get a little raucous at times in the past.



Brimble Pit/Locke’s Hole

notes Posted on Sun, April 01, 2012 15:56:46

1st April 2012. A busmans holiday to look at someone elses digsites. Willie Stanton originally dug at these sites but permission has recently been given to Stu Lindsay, Trever Hughes, et. al. (BEC) to continue the excavation.

Interesting closed basin development seems in places to follow washed out mineral vein. Colourful rocks comprising greys, red, white, yellow, orange (see below) and calcite with gravel and clay infill.

Spent a while in conversation with Stu Lindsay who suggested that there is some historical confusion about which site is which. Barrington and Stanton (1977) descriptions are as follows:

“Brimble Pit Swallet ST 5081 5075 alternative names Westbury Hill Swallet, Frog Hole.

50 yards east of Priddy-Westbury road at Brimble Pit Pool, in a depression by a wall taking the overflow from a small covered reservoir in the next field. Tight vertical rift dug by MNRC 1957-58, blocked by a boulder 50 feet down. Entrance collapsed about 1960. MNRC flood-tested the stream to Rodney Stoke rising in 1956. The Brimble Pit closed basin and overflow channel, and those of Cross Swallet nearby are scheduled as an SSSI; taken together they show all the geomorphic features of Mendip closed basins.

Locke’s Hole ST 5088 5072 alternative name Westbury Hill Swallet.

100 yards east of Priddy-Westbury road at Brimble Pit Pool, in a depression taking the natural overflow of the pool. Entrance shaft dug open by MNRC, 1955-56, entered sloping passage ending in sand-choked chamber. Digging stoppedwhen entrance shaft collapsed. A cow is said to have died in the entrance shaft about 1964, when the farmer half-filled the depression with rubble.”

Reference: Barrington, N. and Stanton, W. 1977 (third revised edition). Mendip: The Complete Caves and a view of the hills. Barton Productions in conjunction with Cheddar Valley Press.



wadi deposits

notes Posted on Sun, November 27, 2011 10:20:54

An exposure of Dolomitic Conglomerate in Harptree Combe showing good sequence of wadi deposits (refer to note on dolomitic conglomerate below).



breccia and conglomerate

notes Posted on Thu, November 24, 2011 21:30:12

A noticeable feature when describing either breccia and/or conglomerate is clast angularity, generally breccia is more angular while conglomerate is more rounded, of course it must be emphasised that the boundaries between the rock types is blurred and there may be a high degree of variability. The angularity or roundness of the clasts within breccia/conglomerate might be used as evidence of the amount of transportation that has occurred, i.e. more roundness might indicate greater transport/higher energy. Clast size might also be a factor, smaller size would require less energy to be transported a further distance.



Dolomitic Conglomerate

notes Posted on Wed, November 23, 2011 19:45:06

Boulder of Dolomitic Conglomerate removed from Hallowe’en Rift, the purple-red colour is the result of high iron content and evidence of haematitization (see below).

On the Mendip Hills, the Dolomitic Conglomerate mostly comprises clasts of Carboniferous limestone cemented into a matrix of sandy marl or fine grained limestone debris, locally derived material from the Old Red Sandstone and Quartzitic Sandstone Group is also present. The rock clasts are angular to rounded and range in size from varying sized gravels to very large boulders. The Dolomitic Conglomerate forms bold crags, it might be eroded into gorges, and it can support underground drainage systems including caves and swallets and is the locus for extensive lead/zinc mineralization. The formation represents Triassic scree and outwash fans adjacent the ancient hills of Paleozoic rocks, and it fills ‘fossil’ wadis or gorges that had been cut into the hills. Recent erosion has partially re-excavated some of these gorges, as at Burrington Combe.

Exposure of surface weathered Dolomitic Conglomerate [slightly silicified] in Harptree Combe.

The conglomerate found on the Mendip Hills has, in many cases undergone considerable secondary changes, in particular silicification, haematitization and dolomitization. Haematitization is the conversion of the conglomerate into an ‘earthy’ iron ore known as ‘red ochre’. The presence of all gradations from unaltered conglomerate to impure haematite rock show that the formation of the latter is the result of metasomatic replacement of calcium carbonate by haematite.

The most widespread form of alteration is dolomitization, hence the name ‘Dolomitic Conglomerate’. All stages of dolomitization are present, both matrix and clasts showing varying degrees of alteration. Dolomitization is usually accompanied by hydration or partial hydration of the originally disseminated haematite to limonite so that macroscopically the colour has changed from red to yellow and yellow-brown. Dolomitization affects more than one level in the Dolomitic Conglomerate though it is most marked in the upper parts of the succession.

metasomatism is a metamorphic process [where rocks are changed by heat, pressure and fluids] in which the chemical composition of the rock is changed significantly, usually as a result of fluid flow.

References:

Green, G.W. et. al. 1965. Geology of the country around Wells and Cheddar. HMSO, London.

Keary, P. 2001. The New Penguin Dictionary of Geology, 2nd Edition. Penguin.