Five members of the Geology group met at East Quarry Car Park on the edge of Otley and headed East along the path following the Geology Trail.  We made good use of the Chevin Forest Park Geology Trail leaflet to guide us and to try and make sense of the geology around us.  The quarry excavated Addingham Edge Grit which formed in the Carboniferous period. Our first stop was to look at the tidal laminations in the sandstone.  Each laminate was formed in a single tide and is an extremely rare sight.

Further along the path, we headed up a steep and slippery slope to see cross-bedding in the Addingham Edge Grit.  This stone is very course and were formed from sands deposited in a river delta.  As well as the horizontal bedding planes, we could also make out other lines which sloped down at a gentle angle representing sandbanks in the river channel – this is known as cross-bedding.  We also made out rusty red colour on the rocks which comes from iron.

Further along the path, we turned south to climb steeply up the hill side before turning along a path which took us past the Vacca Wall, a man-made wall of standing blocks of local sandstone used to keep cattle from straying.

After a lot of mud, we made it to the top of the Great Dibb Landslip.  We were standing on the top of Long Ridge Sandstone and looking down a steep slope into Otley formed by landslips.  At the end of the ice age, the slope became unstable in summer when the ice melted and the sandstone slipped on the mudstones below. Today, the trees help to stabilise the slopes.

Our route continued through lots of mud and then climbed up to another set of crags made of Doubler Stones Sandstone which lies on top of the mudstones.  We could make out evidence of slump bedding with lots of contorted lines.  On one of the rocks, we found fossils of tree branches caused by trees and branches being washed downstream by floods.

Further along, the Doubler Stones Sandstone showed really clear evidence of cross-bedding.  Sand grains rolling along the river bed would have fallen down the slope of sandbanks and settled at an angle.

We climbed up above the crags to a wall where we had a welcome rest looking south to Guisley and Menston.  From there, we headed in the disused Yorkgate quarry with its pond and up to an outcrop of Doubler Stones Sandstone sloping 24 degrees to the South.  This sandstone was made up of much smaller sandgrains than the other stones we had been seeing and was dimpled with the fossils of tree routes.  Just above the outcrop, we could see a thin layer of coal from the Morton Banks coal seam encased in grey fireclay.

From there we splashed through yet more mud and standing water across to the Variscan Orogeny. This was caused by a plate collision at the end of the Carboniferous period and which led the uplifting of northern England into the Pennine anticline.

Finally, we walked along the ridge to Surprise View where we were able to make out the towns and cities of the Aire Valley to the south and east as well as Brimham Rocks to the north and over to Upper Ribblesdale and Upper Wharfedale.  It was starting to rain a little at this point, and was quite windy and exposed on the ridge, so we headed back down the face of the escarpment back to the car park.

Leader: Jane Welsh

Words and Photos: Jane Welsh

Content created by Keith Parker

The Craven Museum hosted a session attended by 15 members of the Geology Group. Just right for a very cold and windy morning!

Several trays of exhibits from the Raistrick Collection were made available in the Education Room. The group appreciated seeing samples of rocks and fossils with explanations from Josephine Drake, Steve Warren and Shirley Everett.

The rocks of particular note were Fluorite with large right-angled crystal formations indicating slow cooling of magma. Samples of Fluorite with Malachite (small samples seen on the ground on the Pikedaw trip) and Barite which Steve Warren told us is an important ingredient in drilling muds used in the petroleum extraction industry because of its high density.

Josephine Drake passed around Black Marble which is actually a fossiliferous limestone and looks glossy black when polished, as seen in Dent Church; Tufa (deposits of calcium carbonate) which can be seen on rocks behind Janet’s Foss. There were many fossils to marvel at, Crinoids, Corals, and Brachiopods, a reminder that the Yorkshire Dales limestone  was formed under a warm tropical sea near the equator.

We were shown Graptolites,  fossils of primitive animals from an even earlier time which appear to resemble Viking runes, examples of which are rarely seen in the Dales but possible seen on a dry stone wall near Helwith Quarry in Ribblesdale during a previous Geology trip.

The group then enjoyed a walk round the Museum looking at rocks, fossils, photographs and interpretation boards of geological significance in the Craven area demonstrating how Geology has shaped the landscape, local human activity and history.

This meeting was a follow-on from a visit in November to Cliffe Castle Museum Keighley where there are several dioramas explaining Geological processes, each museum adding to our knowledge in different ways.

A coffee shop was the next stop for discussion, friendly chat and some humour.

Leaders Pragna Unia and Josephine Drake

NB photos of samples are from the JD Collection and cannot be seen in the Raistrick collection in the Craven Museum.

Though the valley is generally dry, excess rain can cause some water to collect (when all the underground passages are full of water) as in 2015 when Storm Desmond also caused a flow over Malham Cove, a spectacular sight for those who saw it.

We managed the difficult walk eventually and arrived at the top of Malham Cove a large area of Limestone Pavement, with its blocks of limestone Clints, and gaps Grykes formed by weathering, the weakly acidic surface water dissolving the weaker parts of the rock. Walking over this landscape is very difficult so some of us climbed the hill behind to access the steep steps down to the base.

Lynchets are very early Field Systems, seen as ridges in the fields caused by plowing.

Looking back to the magnificent Malham Cove, believed to have been formed as a result of the fault in the valley above,  water flow over causing weathering so that the lip retreats backwards. There continues to be debate about this as there is a mismatch between the size of the valley and the size of the Cove.

The black marks seen on the cove are caused by mosses and lichens growing in seeping water, not the soot as proffered by Charles Kingsley in The Water Babies!

An excellent days walk and Geology field trip, enjoyed by 10 members, all very supportive and patient.

Leader Josephine Drake

Photos Ann Shaw and an occasional one by Josephine Drake

Update: Further information on mines around Malham can be found in “British Mining No 55”, section “Some questions concerning the history of the Pikedaw Calamine Caverns, Malham Yorkshire” by Jack O Myers

Also “British Mining No 97” section “The Malham Mines” by ~Mike Gill and Mike Squirrel.

Having read Jim Hutchinson’s excellent report on a similar trip, Mill Gill Force and Ballowfield’s Nature Reserve, a small group of us met in Askrigg village centre opposite  Skelldale House used in the earlier television series of All Creatures Great and Small.

Lesley Collins was our excellent and very knowledgable leader taking us past the Old Mill, first a Corn Mill, used to make hay-rakes and lastly used to produce Hydro Electric Power for Askrigg but sadly no longer in use, just various remnants of leat, pond and buildings.

In the gill below, the bedrock was the Gayle Limestone, one of the lower bands in the Yoredale series of rocks known as Cyclothems, layers of limestone shale and sandstone which then repeat as shallow seas encroach the land followed by mud deposits from river deltas and finally sandstone, larger grains deposited on the top.

Churt filled fossil

Top of Disher Force

After lunch at Ballowfields Nature Reserve, once the site of a holiday camp for people from the East Coast, we looked at the Wet Groove spoil heaps from earlier lead mining in the area. Climbing up the side of  Eller Beck and Disher Force we were able to find fossils of coral, brachiopods and some chert in the Middle Limestone, now above Hardraw and Simonstone Limestones.

Climbing higher we looked at the Eller Beck Hushes, water had been collected above the highest local limestone, the Undersett, then flushed/hushed down over the rocks to clear the surface and expose the mineral veins in the bedrock. We were also able to make out a geological feature known as the Carbeby Basin.

Eller Beck Hushes, water was collected above then suddenly released to wash off the surface debris and reveal the mineral veins.

Below Ivy Scar further east along Ox Close, a grand bridleway from Bolton Castle to Askrigg and beyond, is the Knott, now a honeycomb of old lead workings. Here we were able to look among the spoil heaps for examples of Barytes, Fluorite, Calcite, and Galena with varying levels of success.

Ivy Scar, Undersett Limestone, the highest local limestone layer, and The Knott below – a Landslip?

The old Mine workings in the Knott

We returned to the cars by the same route with an excellent appreciation of our local landscape and the people who had worked and understood it in the past, with many thanks to Lesley for her guidance and explanations.

Report Josephine Drake

Photos Ian Hughes.