Hypo-theses » fieldwork

Beech Caves

hypocentre — Sat, 19 Jun 2010 17:09:37 +0000

Now that teaching and exams have finished for another year, thoughts turn to the field. Whilst the likes of Geotripper and Dr Jerque get to visit some spectaclur and unspoilt places, my field work takes me to somewhere interesting but not quite as pretty. These are Beech Caves in Staffordshire.

The caves aren’t natural but the result of mining the Triassic Bromsgrove Sandstone (formerly the Keuper Sandstone) for building stone. The pillar and stall workings were begun possibly in 1633 for the construction of the nearby Trentham Hall. The Trentham records for August 31st 1633 note a Roger Low being paid 22 pence per score for carrying 130 foot of stone from Beech.

Trentham Hall 1686 : Image source – Lost Heritage

This was the first of several halls at Trentham, being rebuilt in 1690 and again in the 1830s, ultimately becoming one of the finest buildings in England. Unfortunately, pollution from the growing Potteries conurbation filled the lakes with sewage and the magnificent hall was abandoned and demolished in 1912. The gardens did remain and now the lakes have been cleaned and the gardens refurbished (well worth a visit) there are plans to rebuild the hall as a five star hotel.

Beech Caves still show the evidence of the hand-pick marks by the miners as they followed a layer of pale-coloured sandstone dipping gently down into the hillside. The thick overburden made mining rather than quarrying a more attractive proposition.

In more recent times the caves were probably used as a munition store in the second world war but lately they have been used for raves and other undesirable activities. The caves are now litter strewn and graffiti covered. The land owner and the local council now want to block off the entrances to stop the ne’er-do-wells from getting in. However, in doing so, they will bury an important piece of Staffordshire’s geological history. It would be a great shame if these historic pillar and stall workings were lost. Whilst understanding the landowner’s concerns for the site, it is hoped that some limited, secure access can be maintained for historians and geologists alike.

Reference: Middleton T, 1986. A survey of Beech Cave, Staffordshire. Bulletin of the Peak District Mines Historical Society, 9, 401-403

Shark!

hypocentre — Sun, 06 Jun 2010 23:06:48 +0000

On a field trip to the Peak District this weekend. He is a close up of some Lower Carboniferous shark dermal denticles.

Also some nice crinoid fragments.

Wenlock Edge

hypocentre — Mon, 22 Mar 2010 23:59:04 +0000

Two visits this weekend to Wenlock Edge, Shropshire with strongly contrasting weather (cold and wet on Saturday, warm and sunny on Sunday). This is Knowle Quarry at Presthope, the original GSSP of the Wenlock, and studied by Roderick Impey Murchison in his establishment of the Silurian System. Knowle Quarry is owned by the National Trust and open to the public but being a SSSI no collecting of material is allowed.

There are two distinct facies present, massive reef knolls and interbedded limestones and marls. The red colour in the photograph is below is iron staining on a strike-slip fault plane that cuts the reefs, the near horizontal slickenside lineations can be seen on the surface.

After studying the features here we moved on to the neighbouring Lea Quarry, which was active until recently. Note that the quarry is on private land and permission from the landowner must be given before entering. Here is the margin between the two main facies.

Here the recently quarried faces and the low sun (on the Sunday at least) led to some very successful fossil hunting. Note that I’m a geophysicist who was along on the trips as a van driver so I apologise in advance for any mis-identification.

Crinoid and brachiopod fragments

Ketophyllum

Favosites

Heliosites

Stromatoporoid

Using Gigapan and Photosynth in Geology Teaching

hypocentre — Fri, 22 Jan 2010 00:59:50 +0000

This week I presented some work in progress on the use of gigapan and photosynth to assist mobility impaired geology students at the “Overcoming Barriers to Learning in the Geosciences” meeting of the Geography, Earth and Environmental Sciences (GEES) subject centre of the Higher Education Academy (HEA).

The main aim of our MIS:TIQUE project (mobility impaired students : teaching in quite unsuitable environments) is to provide alternative technologies for mobility impaired students so that they can attain an equivalent learning experience to the able-bodied in geology fieldwork. Gigapan and photosynth allow us to mimic the observation patterns that we would like all students to use. This involves starting with an overview to develop hypotheses to what might be going on, moving in and around the outcrop to make more detailed observations and test the hypotheses, and then move back out again to revise the overview.

I’ve embedded the presentation below. Feel free to use any of the ideas but obviously if you use any of it please credit the source. If you have any questions, comments or feedback please use the blog comments. [Apologies for my powerpoint style - I tend to talk over images without using much text on the slides but this wouldn't make much sense in this context so I have added what I said to the images.]

igs_gees_overcoming_barriers

See more presentations by hypocentre | Upload your own PowerPoint presentations

OpenGeoscience

hypocentre — Tue, 01 Dec 2009 00:02:12 +0000

BGS Make-a-map

Well, it’s about time. The British Geological Survey has been lagging behind its US cousin for some time now. Like the USGS, the BGS is funded by the taxpayer but unlike the American version the data has always been hard to get hold of and expensive. Bits of data have become available slowly as the BGS has gone digital. The 1:625000 scale digital geology map was released through geoindex and the OneGeology global geological mapping portal and this year I’ve been making a lot of use of their on-line rock lexicon, but up until now the 1:50000 digital geology maps have only been available via a paywall to universities or in paper form for the great unwashed.

Today, the BGS released their OpenGeoscience portal, a free service for non-commercial private study, research and educational activities for viewing geological maps, downloading photographs and other information.

There are six OpenGeoscience sections. The Data section covers parts that we’ve had access to previously like the geoindex graphical front end to the BGS’s data holdings such as maps, boreholes, earthquakes and the like, the lexicon of terms used on BGS maps, their rock classification scheme and their database of mineral and rock samples. The education section also links to stuff we have had before – notably ‘Make-A-Map’ for creating basic geological maps of the British Isles. They also (somewhat bravely) provide a link to their new climate change poster which shows that climate change is nothing new and puts into context the current fluctuations with respect to those over geological time.

The maps section provides three ‘views’. The first, a ‘simple’ view allows a zoomable view down to street level with the 1:50000 geological map (where available – not Northern Ireland yet) as an overlay. The geology layer, the transparency of which is variable with a slider control, is a vast improvement on what was previously available to the general public. However, the street map is several years out of date and the satellite view is quite poor resolution. Their ‘intermediate’ view is actually the 1:625000 geology kml layer for Google Earth that has been available through OneGeology for some time and which I blogged about previously here back in August last year. The ‘advanced’ data allows users to down load the 1:625000 data in in ESRI© and MapInfo© formats and also view the 1:50000 data using their Web Map Service.

As an educator, however, the best part for me is GeoScenic, the browsable collection of the BGS’s photographs. I can see this being really useful for examples in lectures.

Finally, and really something quite interesting, is a downloadable version of BGS·SIGMAmobile, the BGS ‘digital field data capture system’ (geological field notebook connected to a database) designed to run on a rugged tablet PC with integrated GPS units. Effectively this is a heavily customised versions of ArcMap 9.2 and MS Access 2003 and is something I’m going to be trying out in the near future.

All in all, it is good to have everything together in one portal, but much is not new and still lags behind what is accessible for the US.

Geology Can Seriously Damage Your Health

hypocentre — Sun, 20 Sep 2009 17:27:25 +0000

[Spotted at Milford on Sea, Hampshire]

Ossum’s Hill

hypocentre — Wed, 26 Aug 2009 20:48:13 +0000

Recently I attended a geological walk lead by Mike Allen from the South Peak Estate of the National Trust to have a look at a new geological section that has been opened upon the side of Ossum’s Hill above the Manifold Valley in the Staffordshire part of the Peak District. The geology of the area is shown in Figure 1.

Figure 1: Geology around Ossum's Crag after The Hamps and Manifold Geotrail, Staffordshire RIGS 2007. Grey = Mixon Limestone Shales; Pale Blue = Ecton Limestones; Dark Blue = Milldale Limestone; Purple = Milldale Limestone Knoll Reefs

The walk departed from the car park opposite Wetton Mill which was the site of the shaft, dressing floor and smelter for the Botstone Lead Mine that operated until around 1850. Machinery was driven by a waterwheel from the River Manifold. The assent of Ossum’s Hill was via the footpath that follows the path of the Hoo Brook, a small misfit river in a wide valley carved by meltwater at the end of the last Ice Age. Part way up, a large Ash tree on the right marks the site of one of the entrances to the Botstone Mine (Figure 2).

Figure 2: Adit Entrance to Botstone Mine

The Hoo Brook valley sides show evidence of landslipage, probably the result of over-steepening of slopes by meltwater undercutting them. On the climb up the valley, many of the pauses for breath were used to discuss different facets of global climate change, both during the Ice Age and during the Carboniferous Period. The route then took us up a side valley to the left up beyond Ossum’s Hill Farm and then left again to the top of Ossum’s Hill where the depressions from numerous old mine shafts can be seen. The local farmer estimates the shaft of one of them to be at over 50 metres deep.
Over the hillcrest, the path then follows a farm track slanting down the hillside back towards Wetton Mill. It is here that the farmer, in widening the track, has opened up some new exposures of the Carboniferous Limestone. The upper part of the section displays the mid-grey coarse bioclastic crinoidal Ecton Limestone (Figure 3). This was deposited on the lower part of the shelf slope as turbidites from the shallower shelf areas.

Figure 3: Bioclastic crinoidal Ecton Limestone

As the path descends the hillside the transition can be seen to the underlying finer bedded and laminated micritic Milldale Limestone with thin beds of chert deposited under quieter conditions. Here is also displayed some tectonic deformation with a small fault and some local small-scale folding, probably related to the fault (Figure 4).

Figure 4: Small-scale folding and faulting in Milldale Limestone

The view across the Manifold Valley clearly displays the reef-knolls within the Carboniferous Limestones as upstanding mounds in the topography (Figure 5), but, with the light fading fast, we didn’t linger too long and descended the hillside back to the Manifold Valley floor and returned to Wetton Mill.

Figure 5: Cross-section showing topography controlled by reef-knolls. Ossum's Hill is on the left. After The Hamps and Manifold Geotrail, Staffordshire RIGS 2007

Thanks go to the National Trust for organising the walk and Mike Allen leading it.

Upcoming National Trust events, including guided walks can be found here: Peak District National Trust Events.
The Hamps and Manifold Self Guided Geotrail leaflet is available from local tourist venues and downloadable from the Staffordshire RIGS website.

Hollington

hypocentre — Sun, 02 Aug 2009 21:50:28 +0000

The Red Hole, Hollington

My squelchy summer fieldwork continues with a visit to the Red Hole Quarry at Hollington, Staffordshire. Hollington Stone is Staffordshire’s most important building stone and has been used for many important buildings around the county including Lichfield Cathedral. It is Lower Triassic in age and at the same stratigraphic level as the Grinshill Stone I looked at in a previous post.

Like the Grinshill Stone, Hollington Stone comes in cream and red varieties, the cream being where fluids have leached the red iron staining. However, where as most of the current Grinshill extraction is cream stone, most of the current Hollington is Red

Hollington White and Red

The cut blocks of Hollington red were difficult to photograph because of the awful weather. Although the wet brought out the colours, it also produced a reflective sheen causing unwanted reflections. Here are some of the better attempts but even these have had to be enhanced.

Hollington Red

Anyone want to explain the bedding in this block?

Hollington Red

Thanks to the quarry operators, Staffordshire Stone Ltd. for the visit.

Fieldwork and the Great British Summer

hypocentre — Sun, 26 Jul 2009 11:22:00 +0000

It’s raining again. This is this morning’s rain radar image from raintoday.co.uk

The Great British Summer - www.raintoday.co.uk

You are not going to get the Great British public believing in global warming until we start getting those Mediterranean summers that we were promised.

This week I went into the field and got absolutely soaked, despite having some expensive waterproof clothing. Torrential rain plus high humidity and a strenuous terrain including a fast flowing stream combined rainwater, riverwater and sweat to make one sodden geologist.

This is typical British geological fieldwork. In areas of soft mudrocks there is very little rock exposure and what little there is tends to be in stream sections where the river maintains a fresh exposure. Fieldwork therefore involves struggling up and down valleys, crossing and recrossing rivers and usually getting wet from above, below and inside the waterproofs. The exposure, when one finds some is typically uninspiring black mudstone with the occasional sandstone.

You can now see why we send our students overseas to map.

Having said all that, it was a grand day out. It made a great change from working in the office. I really enjoyed been outside again. There was some minor folding …

Folded Namurian

and the occasional fossil …

Dunbarella bivalve

Note: I’m being deliberately vague about the location of this Staffordshire valley as it is in part of a nature reserve not open to the public. It was visited with the the reserve warden.

Mis:tique II : Fault Propagation Fold, Broadhaven

hypocentre — Wed, 01 Jul 2009 23:32:26 +0000

I’ve blogged briefly about this structure before here in my list of places that all geologists should visit in the UK. It is the quite spectacular Variscan fault propagation fold and Broadhaven, Pembrokeshire, Wales.

As the thrust in the middle of the section propagates up through this sequence of Upper Carboniferous sandstones and mudstones it folds them ahead of the thrust tip. Eventually, the thrust cuts through the fold, separating the hangingwall anticline from the footwall syncline.

I’ve already previewed our MIS:TIQUE project, attempting to use gigapan technology to help provide alternative geological learning experiences for mobility impaired students. I am giving a presentation on this topic at Keele University’s annual teaching innovation day on Friday so I’ve been working on the data that was collected over the Easter vacation.

One of the main reasons in getting my own domain and hosting this blog myself was the previous inability to insert gigapans and the like into blog posts when using wordpress.com – with a hosted version of wordpress this is now possible.
A full screen version can be found here.

This is one of the two gigapans than I have shot of this structure. This was shot hand held with my Canon 5D and stitched using Canon stitching software. I was experimenting a bit with this one just to see what it would turn out like with automatic focus and exposure. I think it turns out quite well and is sharper than the one I took with the Canon G10 on fixed focus and exposure and using the gigapan robotic mount which you can find here.

I also experimented by uploading all of the images from both cameras into photosynth, and again I’m quite pleased with the results which can be seen below.

The full photosynth can be found here.