Geological Conservation Review Sites Research Articles

Quaternary sea level landforms and sediments in southern England: Description of Geological Conservation Review sites

The Hampshire Basin of southern England contains a number of sites, reviewed here, that contain evidence for former sea levels over a period of c. 0.5 million years and can also be used to aid in understanding of uplift over time and human activity in the landscape. They include three sites where fossiliferous sediments overlie a palaeo shore platform in either Chalk (Boxgrove and Black Rock) or softer sediments (Bembridge), which are the most robust evidence of former sea levels. The other four sites are less useful as palaeo sea level indicators, but contain rich fossil sequences (e.g., Selsey East Beach, Boxgrove, Earnley, Stone Point) or abundant archaeological artefacts (Boxgrove, Priory Bay). Black Rock is most significant for the very rare cold-stage deposits overlying the raised beach and their associated fauna.

Chapter 7 Scottish mineral Geological Conservation Review sites – Metamorphic minerals

Much of Scotland north of the Highland Boundary Fault has been affected by regional and, to a lesser extent, thermal metamorphism and minor metasomatism which, through variable temperatures and pressures, has produced a range of metamorphic minerals. This paper, the seventh of eight on Scottish Mineral Geological Conservation Review Sites, describes ten sites of the highest conservation value within the Lewisian, Moine and Dalradian terranes of the Scottish Highlands, together with thermally altered inclusions in Paleogene volcanic rocks. The minerals featured include the constituents of pelitic and semipelitic schist, such as kyanite and staurolite, unusually large garnet with orthopyroxene and clinopyroxene in ultramafic rocks, and calc silicate minerals, such as tremolite, actinolite, diopside and epidote, together with phlogopitic mica. One site is noted as having stratabound pyrite, chalcopyrite and sphalerite along with large concentrations of chromium mica. The presence of kyanite and tourmaline on the Ross of Mull is one of the few significant mineral sites within rocks of the Neoproterozoic-age Moine Supergroup.Six of the sites encompass extremely rare minerals, generated by the metamorphism of precursors with unusual rock compositions. Foremost amongst these are the barium minerals celsian, cymrite and hyalophane, and the first recorded occurrence in Great Britain of armenite. Although a range of amphibole species occur in both meta-igneous and metasedimentary rocks of the Scottish Highlands, the iron-magnesium clinoamphiboles of the grunerite-cummingtonite series are extremely rare. Indeed the site described in this paper is one of only two occurrences of cummingtonite within the Precambrian-age Dalradian Supergroup. In some cases, the regional mineral assemblages, including the cummingtonite-bearing rocks, have been overprinted by subsequent high temperature/low pressure thermal events associated with the emplacement of igneous intrusions. Pre-eminent amongst the thermal sites must be the occurrence of mullite and sapphire in aluminous shale xenoliths entrained within Paleogene-age basaltic lava flows on the Isle of Mull.

The value of English geoconservation sites in understanding historical collections of lower and middle palaeolithic artefacts

Lower and Middle Paleolithic archaeological sites in England risk falling through the cracks between different types of heritage conservation, since they lack recognisable structures; these sites have often benefitted from protection under geoconservation, particularly through selection as Geological Conservation Review sites, and subsequent designation as Sites of Special Scientific Interest (SSSIs). The geoconservation of key sites, particularly in the formative years of British geoconservation, has allowed combined geological and archaeological reinvestigation. This is of particular benefit to understanding Lower and Middle Paleolithic artefact assemblages, which were often collected in the later 19th–earlier 20th century and consequently lacked both detailed spatial or stratigraphic provenance and contextual geological information. As such, the ‘fine grained’ data which could be gleaned from such artefact collections was limited. Here we review the benefit of geoconservation in allowing the contextualisation of historical archaeological collections, focussing on six key English sites where geological and archaeological reinvestigation has led to important archaeological findings. In particular, the emerging evidence of chronological patterning in Lower and Middle Paleolithic artefacts makes the preservation of such deposits valuable to Quaternary science in general.

Chapter 5 Scottish mineral Geological Conservation Review sites – Hydrothermal veins and mineral assemblages

This fifth paper on Scottish mineral Geological Conservation Review (GCR) sites details those of highest conservation value for hydrothermal veins and associated mineral assemblages. The GCR sites are both large and small reflecting variations in past economic mining and extraction history. During the long mining histories, and after, the sites have yielded new mineral species and a new metal. From the largest ore field for lead, zinc and copper 80 or so minerals have been recognised, including nine new species, one of which was established as the first sulphite, scotlandite. Elsewhere gold and silver were also extracted. For some veins the country rocks were analysed to determine whether they provided the vein elements for primary and secondary minerals, and sometimes dated. Two sites exhibit polymetallic mineralisation, i.e., five elements in the mineral assemblages. In one site veins in close proximity to a sanukitoid pluton received signature elements from the intrusion. Veins in various areas formed in faults, fractures and shears which became conduits for ground waters reacting with vein minerals. Oxygen in the water reacted with lead, zinc and copper minerals and in the presence of CO2 and SO4 supergene mineral assemblages formed in appropriate alkalinities. It is therefore possible to establish paragenetic sequences and calculate stability fields for specific assemblages. Alkalinities and formation temperatures may also be obtained through fluid inclusions studies and isotope analysis.

The Caledonian Structures of Shetland – Funzie and Norwick Geological Conservation Review sites

Locations at Funzie on the island of Fetlar, and at Norwick on the island of Unst contain excellent examples of structures relating to the Caledonian age disruption and emplacement of the Shetland Ophiolite Complex. The Caledonian age Shetland Ophiolite Complex contains exceptionally well developed and exposed sections of the lower parts of the characteristic ophiolite sequence, including layered gabbro, cumulates and mantle rock. Composed of two tectonic units (the Lower Nappe and Upper Nappe) each underlain by an imbricate zone, it is among the finest and most accessible examples of ophiolitic rocks in Europe. The sites at Funzie and Norwick have been selected to be part of the Caledonian Structures of Great Britain Geological Conservation Review (GCR) network, as the best examples in Britain of structures relating to Caledonian ophiolite disruption and emplacement. As the Funzie GCR site and the Norwick GCR site they form the Caledonian Structures of Shetland GCR block.Accounts of all other sites in the Caledonian Structures of Great Britain Geological Conservation Review (GCR) network are already published (Treagus, 1992). Accounts of the Caledonian Structures of Shetland GCR block sites are, therefore, presented in this paper to complete publication of the Caledonian Structures of Great Britain Geological Conservation Review (GCR) network.

Chapter 4 Scottish mineral Geological Conservation Review sites – Magmatic and skarn minerals

This, the fourth paper on Scottish Mineral GCR sites, deals with minerals produced during the late stages of granitic rocks creation. Five sites are described and interpreted, encompassing both minerals within intrusive rocks and those which formed in the adjacent country rocks. The former range from previously-mined, porphyry-style copper-molybdnum sulphide concentrations to one of the few Scottish occurrences of tungsten mineralisation. Mineral deposits formed in mostly calcareous country rocks by the exchange of elements between granitic bodies and them are generally referred to as skarns. They are geographically more widespread than the within-granite bodies, and comprise calc-silicate minerals such as diopside, grossular garnet, wollastonite and, more rarely vesuvianite. In one instance, the skarns contain a wide range of mineral assemblages including some with boron fluoride minerals and mineable concentrations of iron ore. Probably the most enigmatic of these is an apparent exoskarn type assemblage but is devoid of an associated granite.

Chapter 3 Scottish mineral Geological Conservation Review sites – Late magmatic minerals

Late-magmatic granitic fluids are typically enriched in Si, K and rare lithophile elements, including Be, Li, Sn, W, Rb, Cs, Nb, Ta, REE and U, and are also characterised by volatile components such as OH, F and B. Consequently the resultant pegmatite bodies are very coarse-grained and contain accessory minerals with unusual mineral chemistries. Pegmatites, usually present as veins, can occur as emanations from granite bodies or be produced by granite fronts generated by migmatisation during high-grade metamorphism. The former process is represented in the sites by Loch Avon; located within the Main Granite of the Cairngorms, this is the area where large topaz crystals, renowned for their blue colour, are found along with cairngorm and citrine varieties of quartz. Rare beryllium minerals, genthelvite and bertrandite, also occur. The latter process was responsible for the generation of the South Harris and Loch Nevis pegmatite suites which collectively encompass a range of mineral assemblages as follows. The Chaipaval Pegmatite site, some 2 km long, and previously worked for potassium feldspar, contains an unusual suite of uranium-bearing minerals together with spessartine, columbite and gahnite. By contrast the Sletteval Pegmatite site, also previously worked, is more thorium-rich and again contains the rare mineral thorogummite. The more mafic biotite-magnetite-bearing Loch a’ Sgurr Pegmatite site presents an intimate association of uraninite with magnetite, monazite and feldspar. The mica pegmatites at the Loch Nevis site, which formed a series of concordant lenses and veins, were rich in extractable muscovite. Additionally garnet and minor beryl are present in some pegmatites.

An introduction to the Scottish mineral Geological Conservation Review sites

Scotland for its small size possesses a more complex geology than anywhere else in the world, consequently the country has a rich mineral legacy. There are around 650 mineral species now known to occur in Scotland; most of these are silicates, but the assemblage also includes oxides, sulphides and sulphates. Most formed by igneous or metamorphic processes. The igneous minerals produced depends on the nature of the intrusion, be it granitoid or basic to ultrabasic, and also on when it formed in the intrusive cycle; i.e., in early magmatic stages or in late-stage veining. Metamorphic minerals are the product of temperature, pressure and the nature of the precursor rock. A few minerals, such as carbonates and iron oxides are of sedimentary origin, and some formed by the addition of material (mostly metal elements) to rocks, a process known as mineralisation. The choice of mineral GCR sites is based on the presence of rare species and/or unusually large concentrations of minerals and/or the provision of good evidence of geological processes. All sites have national significance and the Meall Tairneachan-Creag An Loch Ba–Zn–Pb deposit is of world-class importance. The coverage of the nation’s mineral species is demonstrated by providing a brief description of them which highlights the sites at which they occur. Thus it will be seen that some minerals are predominant at a number of sites: e.g., galena is the main ore mineral at Leadhills-Wanlockhead, Tyndrum and Strontian. Similarly silica, mostly in the form of quartz is present at many sites, but only in its more exotic form such as agate or cairngorm is it the raison d’etre for its choice as a GCR site.

Percival Allen FRS and the Wealden of southern England

Percival (‘Perce’) Allen's lifelong research into Wealden sedimentology and palaeoenvironments (published 1938–2012) is summarized. His initial investigations, principally into the lower Wealden Hastings Group, led to publication of a deltaic model in 1959 involving eustatically controlled lithofacies architecture. This model was eventually replaced by a revised version in which alluvial fan construction was linked to uplift of source massifs. Today, the revised model and its subsequent refinements form the basis of southern English Wealden palaeoenvironmental interpretation, applicable to both the Weald and Wessex sub-basins in southern England. In later years, Percival Allen took a leading role in Wealden geoconservation, identifying and documenting Geological Conservation Review sites as vouchers for Wealden stratigraphy, palaeobiology, sedimentary processes and palaeoenvironments. A previously unpublished report written by Percival Allen is presented: an account of an excursion to Philpots Quarry, West Sussex, south-east England. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 113, 677–693.

Coastal dune stabilization in Wales and requirements for rejuvenation

Welsh coastal dune systems have become increasingly vegetated in recent decades. Several rare species of plants and invertebrates have declined dramatically in abundance, and in some areas lost entirely. Of the ten dune habitats and species recognized as being features of European importance within the Welsh Natura 2000 sites, nine are currently in Unfavourable condition on at least one site. The decline in active aeolian processes has also reduced the geomorphological interest of the sites, several of which were designated as Geological Conservation Review sites principally on the basis of their physical processes and landforms. The decline in bare sand area between the 1940-50s and 2009 has been quantified at twelve Welsh dune sites using aerial photography and GIS. The decline ranged from 41 % at Gronant Dunes and Talacre Warren to 97 % at Kenfig Burrows, with an average of 81 %. Morfa Dyffryn had the highest remaining percentage of bare sand in 2009 (20 %), with 30–40 % coverage of mobile dune and pioneer communities, while seven sites had < 5 % bare sand. Dune stabilization over the past 60 years has been favoured by a number of factors, including less windy conditions, higher temperatures and longer growing season, increased atmospheric nitrogen deposition, a reduction in grazing intensity, and dune management policies aimed at controlling mobile sand. Climate change projections suggest that, in the next 50 to 100 years, Wales and adjoining areas are likely to experience higher temperatures and higher rainfall, especially in winter, and a further slight reduction in wind speeds. Without intervention, dune and dune slack habitats are likely to be increasingly replaced by fixed dune grassland and scrub, resulting in the extinction of rare plants, invertebrates and other species which require open, mobile conditions. Several intervention options exist, ranging in scale and potential impact. Increased livestock grazing, re-introduction of rabbits, scrub clearance, turf stripping and the creation of shallow ‘scrapes’ can be beneficial but will not by themselves create self-sustaining mobile dunes. In order to have any chance of achieving any significant impact, larger-scale intervention measures, involving large-scale vegetation removal and sand-re-profiling, will be required. At least in the short-term, maintenance measures will be required to prevent vegetation re-growth, and the challenge will be to encourage the development of mobile dune features which will be naturally mobile in the medium to longer term.

The Wealden (non-marine Lower Cretaceous) of the Wessex Sub-basin, southern England

The Wealden Beds (non-marine Lower Cretaceous) of the Wessex Sub-basin, southern England, are exposed principally in coastal sections on the Isle of Wight and in Dorset. Geological Conservation Review sites within these strata have been extensively documented since the earliest days of geological enquiry in Great Britain. The succession is dominated by the alluvial Wessex Formation which demonstrates a broad east–west transition from meanderplain lithofacies to coarser-grained alluvial sediments, in relative proximity to the Cornubian source massif. The meanderplain sediments on the Isle of Wight are of international importance for their plant and animal fossils, the latter including many dinosaurs and their trackways. Upper Barremian transgression resulted in the spread of muddy lakes and coastal lagoons from the Weald Sub-basin into the eastern part of the Wessex Sub-basin, around or through the Purbeck–Isle of Wight structure. The resulting richly fossiliferous mudrock-dominated strata are now represented by the Vectis Formation on the Isle of Wight and in Swanage Bay, Dorset. The Geological Conservation Review sites in the Wessex Sub-basin are documented and interpreted, with particular reference to research history, chronostratigraphy, structural context, palaeoenvironments, palaeobiology and palaeoclimatology. New directions for research are proposed, as applicable.

The Wealden (non-marine Lower Cretaceous) of the Weald Sub-basin, southern England

The Wealden strata (non-marine Lower Cretaceous) of the Weald Sub-basin outcrop in the Weald district of south-east England; the Wealden type-area. The succession is made up of the mixed alluvial–lacustrine–lagoonal Hastings Beds Group below and the predominantly lacustrine–lagoonal Weald Clay Group above. Deposition was strongly influenced by tectonism amongst surrounding massifs, and the warm to hot, periodically wet Wealden climate. Geological Conservation Review sites within the Weald district are dominated by inland sites, but also include extensive coastal cliff and foreshore exposures near Hastings, East Sussex. The Wealden strata have been documented and interpreted since the earliest days of geological enquiry in Great Britain. Collectively, the selected sites demonstrate the key elements of a depositional model for the Wealden of the Weald, developed and published by Professor Percival Allen FRS (1917–2008) in these Proceedings (Allen, 1975). The sites are documented and interpreted, with special reference to research history, chronostratigraphy, structural context, palaeoenvironments, palaeobiology and palaeoclimatology. New directions for research are proposed, as applicable.

The southern English Wealden (non-marine Lower Cretaceous): overview of palaeoenvironments and palaeoecology

Geological Conservation Review sites representing the non-marine Lower Cretaceous Wealden strata provide field evidence for the physical and biological development of what is now southern England, between approximately 120 and 135 million years ago. Knowledge of Wealden climates, palaeogeology, landscapes, hydrology and palaeobiology is synthesized and summarised, with reference to the Weald and Wessex sub-basins.

The marginal Wealden (non-marine Lower Cretaceous) between Wiltshire and Buckinghamshire, England

Non-marine Lower Cretaceous beds of Wealden aspect have long been known from the northern margin of the Wessex–Weald Basin, between Wiltshire and the south Midlands. Termed the Whitchurch Sands Formation, these badly exposed and generally poorly fossiliferous strata appear to represent interdigitating alluvial and brackish-marine units separated by significant sedimentary breaks. Geological Conservation Review sites within the Whitchurch Sands are described and interpreted for their chronostratigraphic, palaeoenvironmental and palaeoclimatic significance.

Percival Allen FRS (1917–2008): a personal tribute

This paper summarises the author's research association with Percival (‘Perce’) Allen FRS (1917–2008), whose wide-ranging and seminal contributions to Wealden (non-marine Lower Cretaceous) sedimentological and palaeoenvironmental interpretation spanned seven decades. The Geological Conservation Review (GCR) Special Issue on the Wealden was initiated as a collaborative research programme initiated during the late 1990s. Stemming from this, the GCR accounts are seen very much as the summation of Perce Allen's lifelong Wealden studies, as demonstrated by GCR sites throughout southern England.

The Geological Conservation Review (GCR) in Great Britain—Rationale and methods

Geoconservation – protecting, managing and enhancing natural geological features and materials, and geomorphological landforms and processes – is especially important in Great Britain, a place sometimes described as the ‘cradle’ of the science of geology. For such a small area of land, Britain has an unusually diverse geological make-up, with rocks from every geological period present. Many stratigraphical terms used internationally were devised here, and British sites provide key study areas where important new geological theories were developed in the pioneering era of the Earth sciences. Therefore, with such a wealth of geology, and Britain's seminal place in the science itself, it is particularly important to conserve and protect key localities here for future generations. A first step in that process is the auditing of the geology and geomorphology of Britain, by carrying out a scientific evaluation exercise according to standard criteria, and creating an inventory of the most important sites for science. In the mid-1970s, the Nature Conservancy Council (NCC) began an ambitious programme for assessment and documentation of the most important sites for the scientific study of geology and geomorphology in Great Britain, building on previous statutory site conservation activity that had already been started in 1949 by the former Nature Conservancy. As a result, the ‘Geological Conservation Review’ (GCR) was formally launched in 1977. The GCR was a world-first project of its type in the systematic assessment of the whole geological heritage of a country, from first principles. Widespread consultation with geologists and geomorphologists across Great Britain was co-ordinated; their guidance and involvement was a key component of the site selection process. Almost 3000 nationally or internationally important sites had been selected for around 100 site-selection categories for the GCR register by 1990. Almost all the GCR sites are now conserved under British law as Sites of Special Scientific Interest (SSSIs), the GCR information providing the scientific evidence-base that underpins that designation. As part of the site-selection process – which is still active – a considerable archive of information about geological sites was amassed. A major publication exercise detailing all the GCR sites in what was to become the GCR Series of books was devised early on in the GCR programme. Thirty-six volumes of the GCR Series have been seen to completion by NCC and the Joint Nature Conservation Committee, and many GCR site reports have been many made freely available on the World Wide Web. As a new venture, the remaining nine volumes will now be published by Elsevier Science Publishers as Special Issues of the Proceedings of the Geologists’ Association. Each GCR volume includes an overview of the subject and outlines the history of study of the relevant branch of the Earth sciences, but most importantly contains detailed accounts of the features of geological importance in the sites described. A scientific interpretation is provided for each site account, which includes supportive illustrations, tables and photographs and an extensive reference list. The GCR rationale, methods and information resource have been invaluable in almost every aspect of geoconservation carried out in Britain, including World Heritage Site nominations, protection of stratotypes, justifying the scientific conservation value of sites at Public Inquiries, in stimulating geological research and in providing a readily available information resource for local, regional, national and international geoconservation activities.