Local Ilkley Moor Wild Life

Just worth noting that in Old English 'mōr' refers to low-lying wetlands! Much of the Pennine moorland area was forested in Mesolithic times and I suspect Ilkley was no different.

The local sandstones underlying the area - all termed collectively "millstone grit" gives the area its acid soil comprising the substance for the heather moorland, and soft water in the Carboniferous period 325 million years ago, was in a swampy area at around sea level with meandering river channels coming from the north.

The layers in the eroded bank faces of stream gullies in the area represent sea levels with various tides depositing different sorts of sediment. Over a long period of time the loose sediments were cemented and compacted into hard rock layers. Geological forces lifted and tilted the strata a little towards the south-east and produced many small fractures, or faults.

Since the end of the Carboniferous time there has been a tremendous amount of erosion and more than a thousand metres of the coal-bearing rocks have been completely removed from the area. More recently, during the last million years or so, Ice Age glaciers modified the shape of the Wharfe valley, deepening it, smoothing it and leaving behind glacial debris.

Flora includes lots of Grasses and Rushes, Heathers and, of course, Bracken. Wavy Hair-grass covers large patches of the highest parts, while the fluffy white tufts of Cotton grass mark the damper spots. The heather comes in three - Ling (Calluna vulgaris), being the most common, but there is also
Bell Heather (Erica cinerea), and Cross-leaved Heath (Erica tetralix), both with larger flowers. In amongst, and becoming commoner, is Crowberry (Empetrum nigrum), which looks very like the heathers. You can tell it by its shiny black berries. On the drier Heather areas you will find plenty of Bilberry (Vaccinium myrtillus). Least and last among the relatives of Heather you may find Cranberry (Vaccinium oxycoccus), though only in the wettest places. There are small amounts of hard to see rich yellow spikes of Bog Asphodel (Narthecium ossifragum), and, in a a very few places, Sundew (Drosera rotundifolia), sticky and spotted with the flies it has caught. The small flowers of Tormentil (probably Tormentilla erecta), are everywhere. The lower slopes can be thickly covered with Bracken (Pteridium aquilinum). Among the other more interesting ferns is the attractive upland Lemon-scented Fern (Oreopteris limbosperma), and of course there are trees - Birch, (probably Betula pendula and Betula pubescens), Rowan (Sorbus aucuparia), Hawthorn (Crataegus monogyna), Wild Rose (Rosa acicularis), Elder (Sambucus nigra), Bramble (probably Blackberry - Rubus fruticosus), Holly (Ilex aquifolium) and (some plantations) of Pine (Pinus sylvestris).

Birds include Merlin (Falco columbarius), Short–eared Owl (Asio flammeus) and Golden Plover (Pluvialis apricaria), Red Grouse (Lagopus lagopus), Meadow Pipit (Anthus pratensis), Common Sandpiper (Actitis hypoleucos), Dunlin (Calidris alpina schinzii), Twite (Carduelis flavirostris), Snipe (Gallinago gallinago), Wheatear (Oenanthe oenanthe), Whinchat (Saxicola rubetra), Redshank (Tringa totanus), Ring Ouzel (Turdus torquatus), Curlew (Numenius arquata) and Lapwing (Vanellus vanellus), Cuckoo (Cuculus canorus), Wheatear (Oenanthe oenanthe), Nuthatch (Sitta europaea), Treecreeper (Certhia familiaris), Blackbird (Turdus merula), Song Thrush (Turdus philomelos), Chiffchaff (Phylloscopus collybita), Fieldfare (Turdus pilaris), Redwing (Turdus iliacus), Wren (Troglodytes troglodytes), Robin (Erithacus rubecula). Hawking for insects, there are plenty of Swallows (Hirundo rustica), Swifts (Apus apus), and House Martins (Delichon urbica), while Carrion Crows (Corvus corone), Jackdaws (Corvus monedula) and Rooks (Corvus frugilegus) are often on the wing looking for morsels. Kestrels (Falco tinnunculus), are distinctive, hovering on the wind..

Other fauna: Lizards, Frogs and Toads may be found and Green Hairstreak Butterflies (Callophrys rubi), whose caterpillars feed on the young Bilberry shoots, are most often seen.

Geology:The rocks of the Ilkley area are Upper Carboniferous (Kinderscoutian), so they are about 320 million years old. These rocks were laid down in deltas on the edge of a large continent, with mountains to the north and south. Sands and muds were deposited by rivers in shallow water. Because the continent was close to the equator, the climate was warm and wet so that tropical rain forest flourished. Dead plant material became trapped in stagnant swamps between river channels. Over geological time it was buried by muds and sands as the rivers in the delta changed position and built up more deposits. The water, oxygen and hydrogen were driven out of the plant remains, leaving only the carbon in coal seams. After the sediments were formed close to sea-level, they were buried by hundreds of metres of sediment and compressed. As the sea water was squeezed out, it carried minerals which cemented the sand and mud grains together to make rocks called sandstones and mudstones (shales).
The rocks were tilted into a large north-south trending fold, called the Pennine anticline, shortly after they were formed. However, the rocks in the Skipton area were also folded into east-west trending folds, probably because of the effect of older rocks of the Yorkshire Dales, which formed a resistant block bounded by the Craven Faults, which lie only a short distance north of Ilkley. The sandstone forming the Cow and Calf Rocks is called the Addingham Edge Grit. Higher up on Ilkley Moor are other sandstone beds, such as the High Moor Sandstone and the Doubler Stones Sandstone, which were deposited after the Addingham Edge Grit and therefore lie above it. All the sandstone beds vary in thickness and probably represent flood deposits in the delta area. Between the sandstone beds lie beds of mudstone (shales) which were deposited in marshes or swamps between the rivers on the delta. The pale grey mudstones sometimes contain fresh-water shells. During the Carboniferous period the sea-level changed regularly, because of glaciations in the southern hemisphere. Therefore the delta was sometimes drowned by sea-water which meant that dark mudstones were deposited above the delta sediments. These marine bands contain marine goniatite and bivalve fossils which can be found in some local mudstones. Because this change in sea-level happened regularly there are many alternations of sandstone and mudstone in West Yorkshire’s Carboniferous rocks. Because of later plate movements, the rocks here have been tilted to the south at a gentle angle, which results in the steep northern slope of Ilkley Moor, which overlooks the Wharfe valley.

Cross section to show the geology of the Cow and Calf Rocks, Ilkley
Sandstone is shown in yellow and is Addingham Edge Grit. Mudstones are shown without colour, underneath the sandstone. North is to the right and obviously South to the left.

Rocks and Landscapes of the Bradford District - Geology of the South Pennines

Spent a day with the West Yorkshire Geology Trust sponsored by Pennine Prospects on Friday 21st October to learn something about the local geology.

The short walk we undertook after an overview of the Watershed
OS GRID REF. SE 130 391

The Rough Rock forms a natural exposure 500m long in crags overlooking the wooded eastern slopes of Loadpit Beck. Scattered exposures of the Rough Rock Flags and the shales below occur in the beck itself. There are many fallen rocks in the slopes below the crags.

Shipley Glen was laid out for recreational pursuits during the Victorian era. There is a long history of use as a park and fairground, which only ceased in the 1990s. The exhibition in the Bracken Hall Countryside Centre adjacent to the site has photos and text documenting the history of the Baildon Moor area.

With a wide range of geological features and the proximity of the Countryside Centre, the site has high potential for educational use. Baildon Moor and its geomorphological and industrial features can be seen from the top of Shipley Glen. There are footpaths in the woods to the base of the crags, so that the sandstone textures and features can be seen easily. Paths to the exposures in Loadpit Beck are narrower and slippery but can still be reached by groups of all sizes.

The whole valley is wooded, so has interesting flora and fauna. There are extensive paths, many of which are very quiet, especially in the upper part of the valley. The views from the top of the crags towards the moors are excellent.

The South Pennines form part of the Pennine ‘backbone’ of England. This narrow range of hills, over 2,000 feet at the highest point, stretches 250 miles from the Peak District of Derbyshire to the Scottish border.

Millions of years ago, when river deltas covered this part of Britain, grit, sand and silt were washed down and deposited here. These became the gritstones, sandstones and shales of the South Pennines. As the conditions changed, these layers were covered by other sediments – forming rocks such as coal.

The Pennines formed in a great upheaval of the rocks, caused by a distant collision of continents. After the uplift, the land may have been as high as the Alps are today! But the softer rocks on top of the Pennine dome were gradually eroded away – once again exposing the harder gritstones beneath.

During successive Ice Ages, great glaciers gouged out wide valleys. As the ice retreated, meltwater torrents continued to deepen some valleys dramatically, leaving side streams to cut their way down steeply to the new valley base below. This abundance of powerful, fast-flowing stream water has had a profound impact on the industrial development of the area.

The South Pennines’ own Millstone Grit and the deposits of limestone left behind by the glaciers have also helped to shape the area’s traditional buildings and industries. They have provided stone to build local farms, homes and mills; rocks to build characteristic drystone walls; and limestone for the production of lime in kilns for use as fertilizer.

Millstone Grit

This term is used for a series of sandstones, siltstones and shales (mudstones) which date from the Namurian epoch of the Upper Carboniferous period and are about 320 million years old. The area that is now northern England lay in a subsiding basin between high mountain ranges. Rivers carried sediments which compressed under pressure of overlying rocks to give a rock sequence which is about 1,700m thick. Deltas of sand built out over deeper waters in which clay and mud was deposited. Sea-level fluctuated because of global temperature changes, so alternating beds of mudstones and sandstones are found. River and delta sediments contain plant fossils, whereas mudstones contain marine fossils, particularly molluscs such as goniatites (like the WYGT logo) and shells.

Coal Measures

After the Millstone Grit rocks were deposited the seas became shallower and deltas built out from the coastlines. Sands and muds brought down by rivers were deposited in huge channels, much like the present Amazon Basin. The continent was close to the equator, so the land surface was covered with luxuriant vegetation, such as tree ferns and other spore-bearing plants. In stagnant lakes and marshes, plant material decomposed without oxygen, so that carbon was retained in the muds. Carbon was locked into coal seams during later burial by sediments. Tree branch and root fossils are very common in river sandstones, whereas marine shell fossils are found in mudstones which were deposited in shallow seas, as sea-levels continued to fluctuate.


Geomap

Stratotable

Permian Rocks

The Permian period followed the Carboniferous period about 290 million years ago. Plate tectonic uplift of southern Europe formed large mountains, so that northern England lay above sea-level in a hot, arid climate. Wind erosion produced blown sand so the first Permian rocks are dune-bedded desert sands called the Yellow Sands Formation, found in a few places in the east of the county. In Late Permian times the land was flooded by a shallow, salty sea called the Zechstein Sea, which dried out regularly because of high evaporation and sea-level fluctuations, leaving precipitated carbonates and other salts behind. The carbonates have been altered to yellow dolomitic limestones during later burial, inter-bedded with reddish mudstones. Fossils are rare, because not many forms of life could survive in such saline waters.

FURTHER READING

Rocks and Landscapes of Huddersfield, available from Huddersfield Geology Group http:/www.huddersfieldgeology.org.uk

Yorkshire Geology by Paul Ensom, 2009, Dovecote Press ISBN 978-1-904-34964-8

Yorkshire Rock by Richard Bell, 1996, British Geological Survey ISBN 978-0-852-72269-5

Sources -

http://www.pennineprospects.co.uk/south-pennines/geology

http://www.wyorksgeologytrust.org/westyorksgeology.html