Programme: 2009 - 2010

© Craven & Pendle Geological Society

Indoor Meetings

Friday: 16 October
Bowland Forest: unveiling the secrets of an ancient cold war. Paul Kabrna

Friday: 13 November
Turbulence, displacement, death and worms: molluscs in the Millstone Grit. Ian Kane Ph.D., University of Leeds

Friday: 12 February
Evidence of global sea level change across western Ireland and northern England during the mid Marsdenian (Carboniferous). Rachael Dale MGeosci (Hons), University of Leeds

Friday: 12 March
Redevelopment of the Rotunda Museum - 180 years in the making. Will Watts BSc. (Hons)., Scarborough Museums Trust

Friday: 16 April
Members Evening. Paul Kabrna, Mike Squirrell.

Friday: date to be confirmed
Rhyolite glaciovolcanism at Öraefajökull Volcano, SE Iceland: a window on
Quaternary climate change
. Angela Walker BSc.(Hons), University of Manchester

Field Meetings

Saturday: 22 May
Salthill Quarry Trail & Clitheroe Castle Keep. Guide: Paul Kabrna

Sunday: 13 June
Rotunda Museum and Jurassic rocks of Cayton Bay, Scarborough. Guide: Peter Robinson

Saturday: 10 July
Quaternary features in Wharfedale, south of Appletreewick. Guide: Jon Barber Ph.D. University of Leeds.

Sunday: 8 August
Carboniferous geology of Slaidburn. Guide: Paul Kabrna

Saturday: 11 September
Millstone Grit in Lee and Greens Moor Quarries, Rossendale. Guides: David Turner, Jean Chicken and Paul Kabrna


Bowland Forest: unveiling the secrets of an ancient cold war
Paul Kabrna, CPGS

Overview of the stratigraphy of the Bowland Sub-Basin
The Bowland Sub-Basin lies within the Craven Basin and is currently the focus of a possible book to be published by CPGS in 2010. Geographically it covers the region from Skipton to Chipping and from Sykes to Clitheroe. Many of the localities are situated in and around the River Hodder and River Ribble.

View from Hall Hill Quarry,Whitewell

View from Hall Hill Quarry near Whitewell towards Dunsop Bridge
Photo: © P. Kabrna 2008

Geologically the Craven Basin was initiated during the collision of two continental land-masses, Laurussia and Gondwanaland, with both continents becoming fused together in the climax of the Hercynian (Variscan) Orogeny at the end of Carboniferous times. Seismic reflection profiles indicate that the Craven Basin extends south westwards into the Formby Basin and underneath the Fylde and East Irish Sea.

Our focus however is on the Bowland Sub-Basin, an Early to Mid Mississippian north-east trending half-graben bounded to the south by the Pendle Fault System, coincident with the Pendle Monocline, and to the north by the faults of the Bowland Line from the Bowland High and the Askrigg Block. The Carbonate sequence is very thick (>6km) especially in the Clitheroe area. Marine sedimentation in the Early Mississippian began on a carbonate shelf (Chatburn Limestone). Progressive steepening of the basin floor produced a carbonate ramp thus hastening the onset of deposition of the Clitheroe Limestone Formation. A variable and complex stratigraphy resulted reflected initially by the development of Waulsortian limestones in deeper water (see photo below).

Waulsortian Limestone

Limekiln Wood Limestone with boulder ded (Arbour Quarry, near Chaigley)
Photo: © P. Kabrna 2009

By Mid-Mississippian time (Tournaisian-Viséan boundary), the steepened ramp had fractured by tectonic rifting into a series of intra-basinal highs and lows which resulted in a change in depositional style (Hodder Mudstone Formation). The base of the Hodder Mudstone Formation is associated with widespread submarine erosion and unconformity, marking the switch from carbonate ramp to hemipelagic depositional regime. This influx of terrigenous mudstone was interrupted by repeated limestone turbidite input into the basin (sourced from the newly submerged surrounding blocks). The widespread deposition of the pelagic cephalopod limestones (Hodderense Limestone Formation) coincides with the basin becoming progressively starved of sediment due to the fact that sea level fell thus cutting off carbonate supply from the surrounding platforms.To compound matters, the surrounding carbonate platforms became fringed with reefs (Settle, Malham and Cracoe). This interrupted circulation between the basin and platform interiors with the result that the water column became stratified, and in these poorly oxygenated waters, the Bowland Shale Group were deposited.

During Late Mississippian to Early Pennsylvanian times northern England occupied an equatorial position; increased rainfall, combined with the uplift in the Norwegian-Greenland Sea region, supplied large volumes of sediment which led to the generally southerly progradation of a turbidite-fronted delta system on the scale of the modern Brahmaputra. Fully marine conditions are marked by ‘marine bands’ usually dominated by thick-shelled goniatites and signifying an increase in sea-level - a product of eustatic sea-level changes caused by glacial fluctuations in the southern hemisphere. Minor coarse grained siliciclastic turbidites comprising the Pendleside Sandstone (Little Mearley Clough; Lower Core near Chipping) are found within the upper parts of the Bowland Shales - a precursor to the Pendle Grit.

The Pendle Grit Formation (type section Nick O’ Pendle) represents a deep water marine sand-rich slope channel/fan complex deposited during the earliest major phase of siliciclastic input into the Bowland Sub-Basin. The lowest parts of the stratigraphy are generally accepted to crop out on the flanks of Pendle Hill near Clitheroe at the Pendleian type-section of Little Mearley Clough. The Pendle Grit is a medium-coarse grained arkosic sandstone. Beds are commonly tabular, bound by thin muddy layers and frequently dominated by massive amalgamated beds. Top surfaces of massive beds are often scoured and mantled by very coarse sediment. Mud-clasts may be scattered throughout massive sandstones, or may define amalgamation surfaces. Wiswell Quarry exposes 80 metres of Pendle Grit (Fig.3) and demostrates all the key features of the sand-rich complex. Eventually the basin was infilled by the transgression of the fluvial Warley Wise Grit.

The Global Stratotype Section and Point (GSSP) for the Mid-Carboniferous Boundary is located in Arrow Canyon, Nevada. Nevertheless, Stonehead Beck, Cowling, remains the European stratotype for the Mid-Carboniferous Boundary therefore ensuring its continued international importance. The outcrop lies within the Sabden Shales at the northwestern end of the Pendle Monocline and spans the Eumorphoceras - Homoceras ammonoid Genus-Zone. Sabden Shales represent the time when hemipelagic muds were deposited in relatively anoxic deep water of the basin. Fully marine conditions are marked by marine bands dominated by a diagnostic thick-shelled ammonoid fauna. The Mid-Carboniferous boundary has been defined at the first entry of the conodont Declinognathodus inequalis about 9.4 metres above the Arnsbergian/Chokerian boundary and significantly is marked by a (moderate?) extinction of faunas (ammonoids and brachiopods in particular). May be the extinction of certain species was triggered by the collision of Gondwana and Laurasia or perhaps the growth of the Gondwanan ice cap lowered sea level suffiiciently to usher in the demise of many taxa.

The Bowland Sub-Basin has a complex and varied stratigraphy with its many formations and members and wide ranging depositional environments will no doubt continue to excite geologists’ for years to come. The diverse fossil assemblage, especially among the trilobites, may provide future Ph.D students with much to do!

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Turbulence, displacement, death and worms: molluscs in the Millstone Grit
Ian Kane, Leeds University

Introduction
The study of trace fossils is known as ichnology. A trace fossil may be a trail, track, or burrow made by an animal in ancient sediments such as sandstone, shale, or limestone. They may be regarded as reliable indicators of original conditions in the sedimentary environment particularly where body fossil preservation is rare. Indeed tracks, trails and burrows have been recognised in Carboniferous strata since the mid nineteenth century particularly within the Late-Mississippian and Pennsylvanian of the British Isles. The Rough Rock and Rough Rock Flags at Cracken Edge, Derbyshire is an area where I studied trace fossils as an independent project whilst at the University of Derby between 2001-2004. They are deposits of a progradational fluvio-deltaic system within the Pennsylvanian Pennine Basin of northern England.

Lockeia
Bivalves are considered as tracemakers of Lockeia, and different living and feeding strategies of bivalves may cause different morphologies of Lockeia. The research work at Cracken Edge was based on the occurrence and distribution of traces attributed to the non-marine bivalve Carbonicola with the aim of answering the following questions: (1) What features of Lockeia and associated traces are indicators of palaeoflow direction, and what do these features tell us about the hydraulic regime? (2) What factors might induce the observed regular spacing of Lockeia? (3) How are Lockeia associated with other traces? (4) Collectively, can interpretation of these observations provide generic insights for palaeoenvironmental analysis? (5) Can these insights provide areas for further study of the Rough Rock and Rough Rock Flags?

Cracken Edge
This topographical feature is a north-south trending escarpment composed of Rough Rock and Rough Rock Flags which are exposed discontinuously in a series of disused quarries for 5 kilometres. The main areas researched were Cracken Edge Quarry (disused) and Fox Holes Clough 1 km north. The sequence flooring the valley are shales which in turn are overlain by the fluvial Chatsworth Grit and two marine bands, the Gastrioceras cancellatum and Gastrioceras cumbriense marine bands. Overlying the Rough Rock at Cracken Edge is the Gastrioceras subcrenatum marine band marking the boundary between the European Namurian and Westphalian stages. This equates to the geology seen in Ratten Clough in the Cliviger Valley. Here the Chatsworth Grit is referred to as the Holcombe Brook Grit. Of the three marine bands seen at Cracken Edge only the Gastrioceras cumbriense marine has not been found in Ratten Clough.

Lockeia

Hypichnial expressions of Lockeia
Photo: © Ian Kane, University of Leeds

Interpretation
These traces have received scientific attention over the last two centuries but several new insights from this study further demonstrate the generic importance of these traces in terms of paleoenvironmental analysis:

(1) A number of palaeocurrent indictors are commonly associated with Lockeia and are confirmed by this study: (a) downstream inclination of vertical burrows. The angle may hint at sedimentation rates and also the size of the individual, (b) Long axes of Lockeia are commonly oriented parallel to palaeoflow. presumably with inhalant siphons pointing upstream. Additional palaeocurrent indicators include: (c) steeper sided scour and higher sediment surface on the upstream side of the trace; (d) diffuse lamination downstream of the trace, or. more widespread downstream erosion.

(2) Enhancement of turbulence by flow around individual or clusters of bivalves may lead to the development of a fan shaped zone of increased erosion immediately downstream; this may lead to disturbance and destabilisation of sediment, and hence other bivalves, downstream. This effect may plausibly explain the relatively uniform spacing pattern of Lockeia and provides an additional indication of palaeoflow.

(3) Scavenging of transported bivalves (killed prior to, or during transport) by polychaete and nematode worms, marked by Planolites and Cochlichnus traces respectively which often radiate towards the imprints of dead bivalves. These assemblages indicate that areas which were suitable for bivalve colonisation occurred in upstream areas.

Conclusion
These findings may provide generic insights into systems with similar settings. In terms of the Rough Rock and the Rock Rough Flags, the traces provide further insights into this well-studied system: (a) palaeocurrent analysis of the traces suggests that a significant component of the flow which deposited the Rough Rock Flags was towards the north-east to south-east: this is confirmed by detailed observation of sedimentary current indicators within the section but is counter to previous interpretations of palaeoflow dominantly to the south-west. This may reflect a different source as postulated for the Haslingden Flags, or may reflect flow divergence associated with overbank flow, crevasse splays or point bars, (b) The occurrence of Lockeia-Planolites-Cochlichnus scavenging horizons within the Rough Rock braided river sandstones suggests that suitable environments for bivalve colonisation existed in upstream localities, suggesting that Rough Rock Flags type facies are probably lateral, as well as distal equivalents to the Rough Rock.

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Evidence of global sea level change across western Ireland and northern England during the mid Marsdenian (Carboniferous)
Rachael Dale, University of Leeds

Many researchers have recognised sea level change during the Carboniferous, resulting in the varying styles of sediment deposition that can be seen across the landscape of the British Isles. During the Namurian, clastic deposition prevailed in which high frequency cyclic patterns in sedimentation can be recognised. At the base of each cycle there are mudstone deposits interbedded with thin bands containing goniatitic faunas. These bands of goniatites, which are commonly found throughout the Namurian, are termed marine bands. These marine bands represent major rises in sea level that can be traced across the successions of the British Isles. Overlying deposits coarsen upwards from siltstones to sandstones and are capped by palaeosols and coal seams which represent periods of emergence. The high frequency cycles can be grouped together to identify larger scales of cyclicity caused by glacio-eustasy. The aim of this study is to document these larger scales of cyclicity in Marsdenian successions and to establish how the depositional environment and sedimentation was controlled by global sea level change.

Exposure of strata in Western Ireland provides ideal data to investigate these glacio-eustatic fluctuations in sea level due to the continuous outcrop. During the mid Carboniferous, the Shannon Basin developed in the County Clare region of Ireland with clastic deposition dominating the Namurian. In this clastic succession, five well-defined cycles of sedimentation occurred from the mid Kinderscoutian to late Marsdenian that form five cyclothems. The lower three cyclothems have been named, whilst the upper two have retained an informal nomenclature (Cyclothem IV and V). Biostratigraphically, Cyclothem IV and Cyclothem V were deposited between Bilinguites bilinguis (R2b1) and Bilinguites superbilinguis (R2c1) goniatite zones of the Marsdenian, which helps to facilitate the development of a sea level model and a comparison with correlative successions of northern England.

Marsdenian goniatite

Goniatite B. bilingue late form specimen from a marine band
at Spanish Point, County Clare Ireland. Photo © Rachael Dale

A comparison study between the (R2b2) and (R2c1) interval was carried out across northern England. During the mid Marsdenian, sediments were sourced primarily from the northeast with a general deepening trend to the southeast. At this time sedimentation rates had begun to match subsidence rates leading to the formation of shallow water, sheet-like deltas. The extensive sandbodies are commonly erosive, incising into the underlying deltaic front deposits. The interval of interest in the Central Pennine Basin are the erosive sandbodies of the Pule Hill Grit / Midgley Grit overlain by the Guiseley Grit / Hazel Greave Grit, whereas in the North Staffordshire, it is the occurrence of the Roaches / Ashover Grit above the B. metabilingue (R2b5) marine band.

Roaches Grit

Roaches Grit exposure in the North Staffordshire Basin.
Photo © Rachael Dale

An interpretation of facies and analysis of stacking patterns between northern England and Western Ireland, has enabled the recognition of fluctuations in sea level. Between the (R2b3) to (R2b5) marine bands, the development of mud prone cycles that lack sandstones made recognition of a lowering in sea level problematic in Western Ireland and the North Staffordshire Basin. Within the (R2b5) biozone sand prone cycles are recognised implying a prograding event. These sandstones are tentatively interpreted to represent a perched lowstand shelf delta. The duration of this lowstand was short lived and occurred within one biozone. A potential glacio-eustatic flooding event is recognised that constrains the distribution of a transgression in the late Marsdenian.

References
Aitkenhead, N, Barclay, W J, Brandon, A, Chadwick, R A, Chisholm, J I, Cooper, A H, and Johnson, E W (editors). 2002. British regional geology: the Pennines and adjacent areas. (London: HMSO for the British Geological Survey.)

Brettle, M.J. et al. 2002. Identifying cryptic tidal influences within deltaic successions: an example from Marsdenian (Namurian) interval of the Pennine Basin, UK. Journal of the Geological Society, London, Vol. 159, pp. 379-391.

Collinson, J D. and Banks, N L. 1975. The Haslingden Flags (Namurian G1) of south east Lancashire: Barfinger sands in the Pennine Basin. Proceedings of the Yorkshire Geological Society Vol.40, pp. 431-458.

Collinson, J D. 1988. Controls on Namurian sedimentation in the Central Province basins of northern England. 85-101 in Sedimentation in a synorogenic basin complex: the Upper Carboniferous of northwest Europe. Besly. B M. and Kelling, G (editors). (Glasgow and London: Blackie.)

Jones, C M. and Chisholm, J I. 1997. The Roaches and Ashover Grits: sequence stratigraphic interpretation of a ‘turbidite fronted delta’ system. Geological Journal, Vol. 32, pp. 45-68.

Ramsbottom, W H C. 1977. Major cycles of transgression and regression (mesothems) in the Namurian. Proceedings of the Yorkshire Geological Society, Vol. 41, pp. 261 -291.

Waters, C. N. et al. 1996. Late Carboniferous stratigraphy and sedimentology of the Bradford area, and its implications for the regional geology of northern England. Proceedings of the Yorkshire Geological Society, Vol. 51, pp. 87 -101

Waters, C. N. et al. 2008. Regional evolution of a fluviodeltaic cyclic succession in the Marsdenian (late Namurian Stage, Pennsylvanian) of the Central Pennine Basin, UK. Proceedings of the Yorkshire Geological Society, Vol. 57, pp. 1-28

Wignall, P. B. & Maynard, J. R. 1996. High resolution sequence stratigraphy in the early Marsdenian (Namurian, Carboniferous) of the central Pennines and adjacent areas. Proceedings of the Yorkshire Geological Society, Vol. 51, pp.127-140.

Wignall, P.B. & Best. J.L. 2000. The Western Irish Namurian Basin reassessed. Basin Res., 12, 59-78.

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Redevelopment of the Rotunda Museum - 180 years in the making
Will Watts, Scarborough Museums Trust

Rotunda Museum, Scarborough

Rotunda Museum: Photo © Paul Kabrna (13 June 2010)

Rotunda Museum
The Rotunda Museum, opened in 1829 for the recently formed Scarborough Philosophical Society, was designed by R.H. Sharpe of York in accordance with a plan suggested by William Smith, to convey his theory that rocks could be ordered by the fossils they contain. Smith acted as site manager during part of the time of construction and was responsible for the original unique display of rocks and associated fossils in correct geological sequence. Its design, in particular the central cylindrical drum, was heavily influenced by Smith. The central cylinder of the Rotunda stands just over 15 metres high and is built of Middle Jurassic Hackness Rock quarried on the Hackness Estate and donated by Sir John V.B. Johnson of Hackness. The Rotunda Museum is an iconic Grade II listed building. Scarborough Borough Council won a Heritage Lottery Fund to allow work on the re-roofing of the original exposed stone dome and lead work, installation of a cylindrical feature lift to all principal floors, general stonework repairs and landscaping to the surrounding area. The museum reopened its doors in Spring 2008 after a two-year £4.4m restoration programme. The Scarborough Rotunda Museum is now described as The Jewel in the Crown of Britain’s Geological Heritage and forms the informative centre for the geology of Yorkshire’s Dinosaur Coast.

With over 5500 fossils and 3000 minerals, the strengths of the Scarborough collection include: numerous type specimens, which were the first of their kind ever to be described and one of the finest collections of Middle Jurassic fossil plants in the country. The collection also includes a large selection of Cretaceous fossils from the Speeton Clay and the Chalk, a wide variety of Upper and Lower Jurassic specimens, specimens from the Ice Age such as mammoth teeth and fossils from the Kirkdale Cave and a pristine Carboniferous plant collection. The whole collection was catalogued and conserved in 2007 and the more spectacular specimens are now on display in the refurbished Rotunda Museum. These give a taste of the quality and range of the fossils and minerals that have been found along Yorkshire’s Dinosaur Coast which stretches from Redcar in the north to Flamborough in the south.

Hackness

Collecting fossils from the Hackness Coral-Sponge Bed and its associated sediments within the Passage Beds Member of the Coralline Oolite Formation (Corallian Group; Oxfordian). Left to Right: Felix Whitham (Hull Geol. Soc.), Yvonne James, Andy Booth and Paul Wignall (kneeling) from CPGS.
Photo © Paul Kabrna (1992).

William Smith
William Smith (1769-1839), considered to be the Father of English Geology, came to Scarborough in 1820 after his release from a Debtors’ Prison in London. He soon recognised the geological potential in the diverse landscape of Scarborough and North Yorkshire; an ideal location from where he could continue to develop his geological ideas. He was the son of an Oxfordshire village blacksmith and grew up to be a brilliant surveyor, water engineer and above all, field geologist. By 1815 he had already produced the first geological map of England and Wales with remarkable accuracy, thereby enabling the precise position of coal and mineral resources below the surface of the earth to be determined. His often forgotten contribution to geology was as a trainer of geologists. His pupils included such later significant geologists as Roderick Impey Murchison and George Featherstonhaugh from America. In recognition of his contribution to science, William smith became the first recipient of the Wollaston Medal, the highest honour in the science of geology. King William IV granted Smith a yearly pension for life and he was awarded an Honorary Doctorate of Trinity College Dublin. Smith made a great contribution to Scarborough and it may be safe to say that no greater scientific figure than William Smith has ever resided in the town. William Smith died on the 28th August, 1839 at Northampton whilst on his way to a meeting of the British Association for the Advancement of Science.

John Phillips
William Smith’s nephew and protégé, John Phillips (1800-1874), was also a most remarkable geologist. Having worked with his uncle William, John Phillips also resided in Scarborough as well as in York, Leeds, Sheffield and Hull. John Phillips recorded in detail the biographical details of his uncle and was responsible for the diorama of the strata of the Yorkshire Coast which is displayed in the Rotunda beneath the central dome. In April 1824, Phillips wrote to tell his new friends in York that ‘Scarborough Castle Hill is surely the finest spot for a geologist that the whole earth contains’. Phillips spent the rest of his life exploring and extending Smith’s geological inventions. His 1829 publication Description of the strata and organic remains of the Yorkshire Coast remains a major landmark in the study of Yorkshire geology. In the last 18 years of his life, John Phillips was Reader and Professor of Geology at Oxford University.

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Members Evening
Mike Squirrell, Paul Kabrna et al

Mineralisation and Mining between Settle and Malham
Mike Squirrell

Introducing Ichnology (Trace Fossils)
Paul kabrna

The term Ichnology was first introduced by the Rev. William Buckland of Oxford circa 1830 (who incidentally wrote the first full account of a fossil dinosaur which he named Megalosaurus). Ichnology is the study of the behaviour of extinct organisms by looking at their traces such as tracks, burrows, borings. These features are usually preserved in sediments and or hard substrates and subsequently known as trace fossils. They were produced by the activity of animals (usually invertebrates but sometimes vertebrates). Many animals such as worms are composed of soft tissue and no hard skeletal parts so are only known from trace fossils, as after death the animal decays and the body is not preserved. Trace fossils are most commonly represented in the geologic record by features formed through animal activity in a substrate of some sort, such as sediment, rock, or wood. These features include burrows, tracks, trails, and borings.

Phycodes

Phycodes: feeding burrows made by repeated probes by an animal into sediment of Kinderscout Grit age, Hebden Formation, (Earl Crag, Cowling, North Yorkshire).
Photo: © Paul Kabrna (2009)

Burrows, tracks, and trails are examples of biogenic sedimentary structures (structures made in an unconsolidated substrate); borings are examples of bioerosion structures. Trace fossils are useful in determining the environmental conditions that prevailed when the traces were made. They are sometimes useful in working out the age of sedimentary rocks such as strata of Cambrian age (590 to 530 MA) which contain few body fossils.

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Rhyolite glaciovolcanism at Öraefajökull Volcano, SE Iceland: a window on
Quaternary climate change

Angela Walker, Manchester University

Öraefajökull is Iceland’s largest stratovolcano, situated at the southern tip of Vatnajökull Glacier in the south east of the island. Its position away from the extensional tectonic forces of the rift zone has enabled the build-up of a substantial edifice 2110m in height (Hvannadalshnúkur). The majority of the volcanic edifice, including its 5km wide caldera is covered by glacial ice, leaving only the southern flanks of the volcano exposed. This area of South East Iceland has been completely glaciated at least 16 times in the last 5 million years (Helgason and Duncan, 2001) and evidence from previous field studies suggests that throughout periods in the geological past, Öraefajökull and the surrounding area was covered by ice to a much greater extent than we see today (Stevenson et al., 2006).

Volcano Summit

Öraefajökull is Iceland’s largest stratovolcano, situated at the southern tip of Vatnajökull Glacier. Photo source: Angela Walker

The volcano has erupted twice since historical records began, in 1727 and 1362, the latter being one of Iceland’s most explosive historical eruptive events producing over 6x109 m3 of rhyolitic tephra (Selbekk and Trønnes 2007). However, the abundance of hyaloclastite (a tuff-like breccia rich in black volcanic glass) present across much of the exposed southern flank of the edifice suggests that Öraefajökull has been at its most active during glacial periods (Prestvik, 1979). The post-eruptive geomorphic evolution of volcanic deposits at Öraefajökull has been dominated by volcano-ice interaction and characteristic glaciovolcanic landforms are evident at many exposures.

A multidisciplinary approach combining field observation, geochemistry and isotope geochronology is being utilised in order to establish the geological evolution of the Goðafjall area on the southern flanks of  Öraefajökull and a record of regional minimum ice thicknesses during the development of the volcanic edifice throughout the varying climatic conditions of the mid to late Quaternary.

Rhyolite

Columnar jointed flow-banded rhyolite. Photo source: Angela Walker

Individual eruptive events have been identified in the field using a combination of traditional field mapping techniques and geochemistry, and the units are being dated using 40Ar/39Ar method. Obtaining robust Ar-Ar ages for Quaternary eruptions can be a challenging process due to the small amount of radiogenic 40Ar present in young samples. To complicate matters further, both subaerial and subglacial Icelandic silicic rocks of all ages have been found to contain relatively high levels of atmospheric argon, which can result in large errors on the determined ages (Gale et al., 1966; Flude et al., 2008). Rhyolitic lavas are preferred because of their higher potassium contents compared to basalts. Feldspar phenocrysts are avoided because they give unrealistically old apparent ages (Flude 2005), possibly from long-term pre-eruptive storage below their closure temperature, in partially crystallised magma chambers.

We are tackling these challenges with a laser Ar-Ar step-heating method and stringent sample selection. Our analyses have revealed that unaltered, unhydrated microcrystalline rhyolite groundmass produces the most consistently reliable result. Using this technique we have obtained an average age of ≈115Ka for the upper subglacial rhyolite unit. We are currently using this technique to determine the age of older rhyolites to obtain a more detailed picture of the distribution of eruptive events compared to ice sheet activity over time.

References
Prestvik, T; (1979) Geology of the Oraefi District, S.E. Iceland. Nordic Volcanological Institute Report 79-01, Reykjavik

Helgason, J; Duncan, R.A (2001) Glacial-Interglacial history of the Skaftafell Region, Southeast Iceland, 0-5Ma. Geology 29 (2): pp. 179-182

Stevenson, J., D. McGarvie, et al. (2006) Subglacial and ice-contact volcanism at the Öræfajökull stratovolcano, Iceland. Bulletin of Volcanology 68 (7): pp. 737-752.

McGarvie 2006: Volcanic eruptions into Iceland’s glaciers. (In CPGS Resumé No.29).

Pagli, C. & Sigmundsson, F. (2008) Will present day glacier retreat increase volcanic activity? Stress induced by recent glacier retreat and its effect on magmatism at the Vatnajökull ice cap, Iceland. Geophys. Res. Lett. 35: art. no. L09304

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Field Meetings

Salthill Quarry Trail & Clitheroe Castle Keep
Guide: Paul Kabrna

Time / Date: 10:30am, Saturday 22 May.

Meeting at: Salthill Quarry, Nature Trail car park [SD 7550 4265]

Logistics: Bring a packed lunch or snack at the cafe in Clitheroe's Castle Museum. Entrance to the museum is £3.50. You don't have to do the museum visit in order to snack at the cafe.

Geological setting: This quarry complex, which is an SSSI, was once considered to be formed of reef limestone. This trip hopes to demonstrate an alternative mode formation. During the morning session a wide diversity of carbonate facies can be seen to be draped over eroded Waulsortian, showing dramatic lateral facies change and palaeoslopes.  Various biofacies are represented as the sea deepened and the carbonate regime was replaced by black shales.  Prolific basal Viséan brachiopod, cephalopod, echinoderm, and trilobite faunas are known to occur through this section.

Clitheroe Castle sits on another of these Waulsortian mud-mounds. As the Museum has been re-developed, the limestone below the Norman Keep has been cleaned. This trip will enable you see the Clitheroe limestone in all its glory.

Map
1:50 000 sheet 103 Blackburn and Burnley
1: 25 000 sheet SD 64 / 74 (Clitheroe and Chipping).
Geol. Survey 1:63 360 Sheet 68 Solid Clitheroe

References
Donovan, S.K. 1992. A field guide to the fossil echinoderms of Coplow, Bellman and Salthill Quarries, Clitheroe, Lancashire. North West Geologist, 2, 33-54.

Earp, J. R., Magraw, D., Poole, E. G., Land, D. H. & Whiteman, A. J. 1961. Geology of the Country around Clitheroe and Nelson.  Geological Survey of Great Britain Memoir, England & Wales, Sheet 68

Miller, J. & Grayson, R. F. 1972. Origin and structure of Lower Viséan “reef “ limestones near Clitheroe, Lancashire. Proceedings of the Yorkshire Geological Society, 38, 607-638.

Riley, N. J. 1990. Stratigraphy of the Worston Shale Group (Dinantian), Craven Basin, north-west England. Proceedings of the Yorkshire Geological Society, 48, 163-187.

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The Rotunda Museum and Jurassic rocks of Cayton Bay, Scarborough
Guide: Peter Robinson

Time / Date: 10:00am, Sunday 13 June.

Meeting at: Rotunda Museum Grid Ref. [TA 043 882]; carry packed lunch.

Parking (Morning): Meet at Killerby Park at Grid Reference [TA 069 841] at 10am. The parking fee at Killerby Cliff is £2 for the whole day. This is paid at a machine on entry so drivers should have the coins with them when they arrive. The road layout has changed since the guide in Yorkshire Rocks & Landscape field guide was written. Turn off the new A165 at the roundabout, and take the Filey Road (old A165) to get to the Killerby Cliff/car park.

Parking (Afternoon): Will Watts suggests car parking at either Palm Court or Brunswick Centre or the Spa underground carpark; all are about 5 minutes from the Rotunda. For more information on parking go to the Rotunda web site. www.scarboroughmuseumstrust.co.uk/museum-trust/visiting-information.

Geological setting: Cayton Bay lies between the headlands of Knipe Point (also known as Osgodby Point) and Yons Nab on the coast of North Yorkshire, between Filey and Scarborough. The solid geology of Cayton Bay comprises a succession of Middle and Upper Jurassic rocks that are affected by faulting, with a number of NNW-SSE trending faults passing through the bay. The rocks are overlain by Quaternary glacial sediments. The Middle Jurassic consists mainly of fluviatile and deltaic sandstones with marine intercalations. The considerable thickness of rocks seen here in part is due to movement on the Red Cliff Fault.

Dinosaur tracks are abundant in the Middle Jurassic rocks of Yorkshire and indeed characterize the non-marine sequences developed within the Cleveland Basin. These tracks and associated trackways provide valuable evidence of the possible diversity of the dinosaur communities, their potential makers and behaviour and useful insights into the habitats and palaeo-environment during the time of deposition.

The instability of the cliffs at Cayton Bay has been monitored since 1999 as part of a regional coastal strategy study (Halcrow 2001). The study aims to support forward projections of cliff instability and recession, coastal erosion and the risk to people and assets.

The whole of Cayton Bay, including the area affected by landslides, is a Site of Special Scientific Interest (SSSI), owing to the its nationally important geology, rare plants and invertebrates.

Maps
O.S. 1:50 000 sheet 101 Scarborough & Bridlington.
BGS 1: 63 360 sheet 54 Scarborough

References
Fish, P.R., Moore, R. and Carey, J.M.  2006.  Landslide geomorphology of Cayton Bay, North Yorkshire, UK.  Proceedings of the Yorkshire Geological Society, 56, Pt. 1  pp. 5-14

Romano, M. and Whyte, M.  1994.  The Middle-Upper Jurassic sequence between Cayton Bay and Yons Nab.  Yorkshire Rocks and Landscape (Ed. Colin Scrutton) Chapter 19, pp. 174 - 182

Romano, M. and Whyte, M.  2003.  Jurassic dinosaur tracks and trackways of the Cleveland Basin, Yorkshire: preservation, diversity and distribution.  Proceedings of the Yorkshire Geological Society, 54, Pt. 3  pp. 185-215

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Quaternary features in Wharfedale, south of Appletreewick
Guide: Jon Barber

Time / Date: 10:30am, Saturday 10 July.

Meeting at: Burnsall car park; carry packed lunch for the day.

Quaternary setting: All of the Yorkshire Dales (with the exception of Calderdale) are reputed to hold evidence of cyclic readvances of ice during the latter part of the last glacial (Devensian). Arthur Raistrick and others had attempted to correlate these readvances across the Dales by mapping ice marginal landforms. Whilst very clear moraines exist in Swaledale and Wensleydale, the ice-marginal features of Wharfedale tend to be subdued and their explanation of their genesis a little more problematic. Raistrick’s moraines in Wharfedale coincide with the lips of a series of sediment filled rock basins cut through by the river whilst other potential ice-contact landforms are totally omitted from his map. Today’s excursion follows the riverside path from the car park at Burnsall, downstream to Drebley, one of Raistrick’s moraines that cross the Wharfe Valley and then back through the village of Appletreewick to Burnsall. Things to look out for: rock lips and basins, Silurian slates (not supposed to outcrop in Wharfedale), erratic rocks, glacial landforms.

Carboniferous setting: Near Drebley, the River Wharfe cuts a fine section to the west of Haugh through the Pendle Grit Formation, the oldest sandstone formation in the Millstone Grit Group. It represents the first major influx of coarse feldspathic sand of the Millstone Grit delta encroaching from the north. The sandstones show the massive sharp-based beds characteristic of turbidites i.e. sand deposited out of suspension in turbidity currents that flowed down the pro-delta slope. Islands or stacks of very thick bedded massive coarse pebbly sandstone in the middle of the river probably represent deep channel fills.

Maps
O.S. 1:25 000 Outdoor Leisure 10, Yorkshire Dales, Southern Area
BGS 1:63 360 New Series Sheet 61, Pateley Bridge

References
Aitkenhead, N.  2007.  Quaternary features in the Barden Bridge-Drebley area of Wharfedale. Field Visit Reports Summer 2007, Leeds Geological Association  pp. 4-5

Dakyns, J.R.  1893.  Glacial phenomena of Wharfedale between Bolton Abbey and Kettlewell. Proceedings of the Yorkshire Geological Society, 12, pp. 299 – 305

Kane, I et al.  2010.  Submarine channel response to intrabasinal tectonics: The influence of lateral tilt. AAPG Bulletin; February 2010; v. 94; no. 2; p. 189-219

Raistrick, A.  1931.  The glaciation of Wharfedale, Yorkshire. Proceedings of the Yorkshire Geological Society, 22, pp. 9 – 20

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Carboniferous geology of Slaidburn
Guide: Paul Kabrna
Special thanks to Caroline Blackwell for organising access to the localities

Time / Date: 10:30am, Sunday 8 August.

Meeting at: Grid Ref. [693 526] on Back Lane approximately 2 miles west of Slaidburn (OL 41 Forest of Bowland and Ribblesdale O.S. Map). To assist the local farmer, please make sure you park on the grass verge and not on the lane itself. After this stop we shall drive into Slaidburn and park up for the rest of the day. The main village car park is fee paying.

Logistics: Carry packed lunch for the day. Paths are good and the walking easy. As usual be prepared for inclement weather.

Geological setting: Slaidburn lies within the Bowland Sub-Basin, an Early to Mid Mississippian north-east trending half-graben bounded to the south by the Pendle Fault and to the north by the faults of the Bowland Line. The infill of the Bowland Sub-Basin consists of up to 4 km of syn-rift Mississippian strata, predominantly carbonates, with lesser siltstones and sandstones. The carbonate rocks (Locality 1: New Biggin disused Quarry, Locality 2: Hammerton Crag and Locality 3: Hammerton Ford) were deposited across the basin during the early stages of extension. When active extension began to segregate the basin into highs and lows, mudstones, siltstones and calcareous sandstones were deposited on the basin floor (Locality 4: Barn Gill). Basinal areas were also infilled by carbonate gravity flow deposits and subordinate siliclastics (Locality 5: Barn Gill, Locality 6: Rain Gill and Locality 7: Higher High Field disused Quarry). If there is time we shall walk along the road to view an outcrop of Lower Bowland Shales which represents a time when carbonate input was cut off from the basin. In the oxygen depleted marine waters fossils such as bivalves and goniatites were preserved. (Locality 8: Langcliffe Cross Brook).

The excursion should end about 4pm.

Map
O.S. OL 41 Forest of Bowland and Ribblesdale

References
Earp, J. R., Magraw, D., Poole, E. G., Land, D. H. & Whiteman, A. J. 1961. Geology of the Country around Clitheroe and Nelson.  Geological Survey of Great Britain Memoir, England & Wales, Sheet 68.

Parkinson, D. 1935. The Carboniferous succession in the Slaidburn district, Yorkshire. Q.J.G.S. London, 92, pp. 294-331

Riley, N. J. 1990.  Stratigraphy of the Worston Shale Group (Dinantian), Craven Basin, north­west England.  Proceedings of the Yorkshire Geological Society, 48, pp. 163-187

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Millstone Grit at Lee and Greens Moor Quarries, Rossendale
Guide: David Turner, Jean Chicken and Paul Kabrna

Time / Date: 10:30am, Saturday 11 September.

Meeting at: Grid Ref: SD 863 216 - Travelling from Burnley on Bacup Road (A671), at road junction in centre of Bacup turn right on A681 in the direction of Rawtenstall. One mile along A681 turn right left opposite the Royal Oak pub into a cleared industrial site and drive forward to where a car park area has been created.

We will be parking here all day so carry a packed lunch. Walking is generally on quarry trackways but stout footwear is advisable plus usual inclement weather gear. Total Distance will be 3 to 4 miles with a moderate incline for the first half mile.

Archaeological setting: The two quarries – Lee & Greens Moor began as separate quarries but extensive working from 1820 onwards caused them to merge. The site is of interest for both Geology and Industrial Archaeology. Stone from these quarries went to build many public buildings and also the paving of Trafalgar Square. We will see remnants of railway tracks, steam powered cranes and dressing areas where window lintels, road setts and curb stones lie where they were abandoned. The site is also part of the Irwell Sculpture Trail.

Geological setting: Lee Quarry, a Site of Special Scientific Interest (SSSI) since 1997, shows one of the best available exposures in the Pennsylvanian (Upper Carboniferous) Haslingden Flags Formation (Rough Rock Group: Yeadonian age), a unique development within the Millstone Grit Group of Rossendale Sub-Basin. The formation consists mainly of fine-grained sandstones, siltstones and shales. Sedimentary structures including large-scale cross-bedding, ripple lamination and a variety of bed forms are visible in the sandstones. Through the overall form of the sedimentary units and their internal sedimentary structures, the Haslingden Flags are interpreted as having been deposited as a 'bar-finger' delta having an east-west origin.

Also of great importance is the suite of trace fossils described from the area. These include the escape shafts and resting traces of bivalves Lockeia, sinuous worm trails Cochlichnus, and Limulid (i.e. King Crab) walking traces Kouphichnusand resting traces Limnulicubichnus. This assemblage indicates shallow non-marine conditions, possibly with periodic intervals of emergence. The combination of rich trace-fossil assemblages and good sedimentary features marks Lee Quarry as being of great importance to studies of Pennsylvanian depositional environments and palaeogeography.

Map
O.S. OL21 - South Pennines

References
Wright, W. B. et al 1927. The geology of the Rossendale Anticline. Memoir of the British Geological Survey. Sheet 76.

Hampson, G. J. et al 1996. Critical application of high resolution sequence stratigraphic concepts to the Rough Rock Group (Upper Carboniferous) of northern England. Geological Society, London, Special Publications 1996; v. 104; p. 221-246

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