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www.lancashire-geologists.co.uk The Geologists’ Association (GA) was formed in 1858, and actively promotes the study of geology to all who are interested in Earth Sciences. The Lancashire Group is a local branch of the GA which meets monthly in Clitheroe. It is an informal, friendly and inclusive organisation and welcomes members and guests regardless of their level of geological knowledge. It organises a programme of winter lectures and summer field excursions which are open to all. The group has very close ties with GeoLancashire and the two organisations have worked together on a number of projects in recent years. The Ribble Way provides a ready-made excursion into many of the geological landscapes of Lancashire and the Yorkshire Dales. These short geotrails provide a way of exploring them. A geological guide to the whole route is planned for the future. River Douglas Ribble Way Longton Preston Walk No1 River Ribble Lytham St Anne’s Brockholes Walk No2 Preston Ribchester Walk No3 Blackpool Dinckley Walk No4 Longridge Fell Clitheroe Clitheroe Walk No5 River Hodder Fleetwood Gisburn Easington Fell Stainforth Ordovician-Silurian Settle (See timeline below) The Geologists’ Association (LGGA) Gisburn Clitheroe Ribchester POCKET GUIDE POCKET GUIDE POCKET GUIDE Walk 2 Brockholes Walk 3 Ribchester Walk 4 Dinckley Gorge Walk 5 Clitheroe ARNSBERGIAN CHOKERIAN 370 Million years 590 4500 DINANTIAN (Carboniferous Limestone) 515 445 415 370 280 235 135 195 NAMURIAN (Millstone Grit) Westphalian (Coal Measures) 280 Million Years Stephanian 2.5 PENDLEIAN ORIGIN OF EARTH Ribble alley POCKET GUIDE Walk 1 Preston CAMBRIAN 5 POCKET GUIDE ORDOVICIAN POCKET GUIDE SILURIAN 4 Ribble alley DEVONIAN POCKET GUIDE CARBONIFEROUS 3 Ribble alley The youngest solid rocks are of Permian and Triassic age (290-205 Ma). These are also sandstones but mostly reddish in colour; they form the coastal plain of West Lancashire and the Fylde. PERMIAN POCKET GUIDE Overlying the limestone are Carboniferous sandstones, gritstones and finer-grained sediments of Namurian 'Millstone Grit' age (326–312 Ma). Erosion over millions of years has removed much of this rock to form the dark moorland landscapes of Bowland, Pendle Hill and Longridge Fell. JURASSIC Ribble alley Walk 4 Dinckley Gorge CARBONIFEROUS STAGES The Ribble Way Ribble alley POCKET GUIDE Walk 4 Dinckley Gorge Ribble alley Age/Million Years (Ma) Whernside Ribble alley QUATERNARY GeoLancashire Ribble alley PERIOD or SYSTEM Ingleborough Ribblehead Ribble alley POCKET GUIDE CRETACEOUS Horton in Ribblesdale Ribble alley Ribble alley 65 Stainforth Ribble alley ROCKS occurring in the study area Preston TERTIARY Settle Geolancashire is a voluntary organisation founded in 1991 to protect and raise public appreciation of the geology and landscapes of Lancashire. It has produced a number of geotrail guides and other publications for several sites across the county, details of which may be found on the website. Ribble alley Rocks of Carboniferous age (360-290 Ma) covered the older rocks and now dominate the landscape of the Ribble valley. The river rises in an area of the oldest Carboniferous rocks, the Craven limestones, which have given the Yorkshire Dales National Park its characteristic landscapes. The sink holes, caves and limestone pavements around Ingleborough, Whernside and Pen-y-ghent are produced by solution weathering of these limestones. TRIASSIC Morecambe Bay www.geolancashire.org.uk Ribble alley 2 Horton Carboniferous Limestone (Dinantian) THE GEOLOGICAL TIMESCALE Pendle Hill 1 Permo-Triassic Millstone Grit (Namurian) POCKET GUIDE 4 Ribble alley Ribble alley The Ribble valley's oldest rocks are sandstones and limestones which were laid down 410-510 million years (Ma) ago in the Ordovician and Silurian periods. They have been affected by folding and faulting during their long history. Around Horton-in-Ribblesdale and Stainforth these processes uplifted the older rocks to the surface, where today they are quarried for roadstone at Horton and Ingleton. Ribblehead Age of Rocks Ribble alley This Ribble Valley Geotrail Pocket Guide is just one of 5 pocket guides currently available or in preparation POCKET GUIDE The Geology How old are the rocks? Ribble alley Millstone Grit (Gritstone), Rossendale CAINOZOIC ERA MESOZOIC THE GEOLOGICAL TIMELINE ORDOVICIAN Million Years Ago 515 w w w. g e o l a n c a s h i r e . o r g . u k 445 DEVONIAN 415 DINANTIAN 370 The most recent deposits are less than 25,000 years old. Thick layers of glacial till (boulder clay) can be found especially on the lower ground, while sands and gravels CARBONIFEROUS characterise the hill margins. Post-glacial NAMURIAN WESTPHALIAN STEPHANIAN PERMIAN TRIASSIC deposition includes alluvium on the river PENDLEIAN ARNSBERGIAN 280 235 195 floodplain, mud and sand in the estuary Warley Pendle Sabden Shales Wise and blanket peat over the higher hilltops. Grit Grit Limestone Pavement Gordale Scar Copster Green Sandstone THE GEOLOGICAL TIMELINE CARBONIFEROUS GeoLancashire RIGS Group This is a Quick Response (QR) code. When scanned with a smartphone (see below) it can link you directly to a page on the GeoLancashire website to provide you with more information about this walk. To scan a QR code you will need a smartphone or tablet with a camera and an ‘app’ to read the code. You will also need access to the internet on your device. There are many free QR scanner apps available. You can download them from sites like www.qrstuff. com and www.qrdroid.com SILURIAN PALAEOZOIC Details of these may be found on our website. We plan to produce a further five Ribble Valley geotrail guides for the section from Clitheroe to Horton-in-Ribblesdale and details will be available on the website as they are published. PRECAMBRIAN GeoLancashire RIGS Group GeoLancashire RIGS Group GeoLancashire RIGS Group GeoLancashire RIGS Group RIGS Group GeoLancashire TRIASSIC 205 PERMIAN 250 Million Years Ago STEPHANIAN 290 WESTPHALIAN 307 NAMURIAN DINANTIAN 312 ARNSBERGIAN Sabden Shales 326 DEVONIAN 360 410 SILURIAN ORDOVICIAN 440 510 PENDLEIAN Warley Wise Grit Pendle Grit Copster Green Sandstone Maps used in this leaflet contain Ordnance Survey data © Crown copyright and database right 2012 Dinckley Leaflet A3 version 3.indd 1 10/01/2013 19:56 Ribble alley RIGS Group GeoLancashire 4 granite cobble Walk 4 Dinckley Gorge 1 Walk 4 Dinckley Gorge ROUTE The footpath leads to a hard rocky outcrop of Warley Wise Grit at the bottom of the gorge where the river is narrowest. This restriction contrasts with the wide basin immediately downstream known as the Sales Wheel which has been cut in the softer Sabden Shales. The rocks are youngest to the west and they get older upstream. The rocks in this little crag are made of coarse Slickensides sand grains and quartz pebbles stuck together. They were deposited in a shallow, fast-flowing river channel which was part of a large delta straddling the equator. Also, look for ‘slickensides’ (see photo) - polished surfaces with parallel scratches where faulted rocks have slid past each other. 2 Walking upstream, two beds of mudstone can be 3 by the reddish, medium to coarse Copster Green Sandstone which marks a return to deltaic deposition in shallow water. Its generally uniform texture makes it a good building stone and it has been used in many of the cottages in Copster Green and Ribchester. St Leonard’s Chapel in Old Langho is a good example. Line of Ge 4 ologic al Se ction 2 3 The shingle bank adjacent to the bridge contains many different rock types. These include pebbles of black chert sandwiched between grey limestone, various sandstones, blue/green volcanic rocks and an occasional granite cobble. All these stones have been transported by the river but some – like the granite – were originally brought here by ice from the Lake District and Yorkshire Dales. They are known as ‘glacial erratics’. 1 1 kilometre 0 4 The rock beneath the pebble bank is Pendle Grit Start: Car park east of Salesbury Hall at SD676357 Route: A footpath leads from the back of the car park down to the river bank alongside a gully containing a small stream. From Location 1, follow the footpath upstream along the river bank crossing a number of small streams. This section can be very muddy. At the end of the woods a gate gives access to the field beyond. Keep to the waymarked track through the field to the suspension bridge. At this point you can either retrace your route back to the car park or follow the extension. Distance: From car park to location 4 and return is approximately 3.5km (2 miles) Entire circuit is approximately 7.5km (4.7 miles) sandstone and it provides sound foundations for the bridge. Many of Preston’s best buildings such as the Harris Museum are made of this stone which was quarried extensively around Longridge and Waddington Fell. Millstone Grit All the rocks around Dinckley belong to the Millstone Grit group and are about 230 million years old. The coarse-grained gritstones were deposited rapidly in a huge shallow water delta. They alternate with thinner beds of finer-grained muds and shales laid down slowly in deeper water. 250m 500m 750m 1km Maps: OS Explorer 1:25K Sheet 287; OS Landranger 1:50K Sheet 103 Extension: Cross the bridge and follow the path towards Trough House farm. Immediately before the farm, watch out for the footpath marked with the Ribble Way logo on the left. Follow the Ribble Way through three fields; cross Starling Brook then take the right hand path at the edge of the wood up to above Hey Hurst. Cross the road to the house then fork left downhill looking for a fingerpost in the field. Cross the low ridge beyond then bear over to the right to Haugh Wood and down to the river bank. Follow this for half a mile to Dewhurst House. The access road on the left leads to de Tabley bridge and, turning left, the road back to the car park. seen in small exposures on the river bank, separated At the first location you will notice that the prominent flat surfaces of the rocks are dipping about 40 degrees downstream. Dips & folds: the flexible rocks Ribble alley Since the sands which make up the rocks were laid down on the horizontal surface of the sea floor, the rocks must have been crumpled up later into a series of huge folds, of which this section is just a tiny exposure. You can get some idea how big this fold is from the 2km cross-section. The Warley Wise gritstone bed which you are standing on dips to a low point north of the river and emerges back on the surface in the north face of Longridge Fell 12 miles to the North West. NORTH WEST NORTH WEST Sabden Shales bedding planes: dipping about 40 degrees POCKET GUIDE Dinckley Leaflet A3 version 3.indd 2 Sabden Shales Pendle Grit (mudstone) Warley Wise Grit Pendle Grit (mudstone) Warley Wise Grit SOUTH EAST Pendle Grit (mudstone) Copster Green (sandstone) Pendle Grit River Ribble (mudstone) Copster Green (sandstone) River Ribble Pendle Grit (sandstone) Pendle Grit (sandstone) Bowland Shale Group SOUTH EAST Bowland Shale Group 2km Geological Section 10/01/2013 19:56