MAGical meadows and the Durham Magnesian Limestone Marsden old quarry local nature reserve Preface The United Kingdom is blessed with landscapes celebrated nationally and internationally for their beauty and biodiversity. Many are protected and enhanced, others, including Durham’s Magnesian Limestone areas, have been given relatively little protection and have been exploited with scant consideration as a result. This book tells a story of a landscape of great rarity. It is also a story of crude exploitation of minerals, habitats and species over many years, culminating in the great ecological and visual damage caused by coal mining, quarrying and waste disposal in former quarries. It is a story about both the fragility and resilience of the area and tells how it has survived and is being restored following belated recognition of its unique importance. The Turning The Tide Millennium Project, which accelerated the recovery of the Durham coast after more than a hundred years of colliery waste tipping on clifftops and beaches, is evidence of the scale of restoration required. The purpose of this publication is to further increase awareness of the importance of this limestone landscape and show how it can be handed on to future generations in a state that reflects well on our stewardship. David Miller DURHAM photo: www.wildstock.co.uk Contents Thrislington NNR Introduction Introduction 01 The vast areas of limestone laid down beneath Caribbean-like shallow warm seas about 290 million years ago, in what is now northern Europe, have been the basis for prosperous agriculture and rich resources of wildlife and minerals. These lime-rich bedrocks provide fertile soils, which are home to widely diverse Geological History 02 habitats and species, abundant water in aquifers and quarried stone for building and chemical processes. Where limestone exists, settlements have thrived as local people have benefited from the exploitation of this rich resource. Social History 10 Limestone, however, is not a uniform material. It exists in many forms, depending on the fineness of its grains and its chemical content. The Magnesian Limestone of County Durham is one of the rarest and most valuable and the Current Status 14 coastal cliffs are unique in the British Isles, home to plant communities not seen together anywhere else in the country. Because as much as two thirds of the national resource of Magnesian Limestone grassland occurs in the North-East of Plants and plant communities 18 England, it is seen as the jewel in the crown of the region’s biodiversity. This has counted for little in the past and the crude exploitation of mammals, plants and minerals has diminished the area’s natural diversity. This book records Durham coastal cliffs 24 the loss of several species of mammal and many plant species. Agricultural practice, as is the case almost everywhere in the country, has been a major factor in further depredation. It is, however, the existence of the many limestone quarries on the escarpment, once so crucial to the steel and refractory industries Invertebrates 28 of the North-East, that has provided the refuge for threatened wildlife. Indeed, many of the best sites to explore the wildlife and geology of the area are old quarries. Butterflies 30 A further threat to this fragile balance came from pressure to fill the quarries with household and industrial waste. Many have been filled and it is unknown what effect this will have long-term on the quality of water supplies taken from Mammals, amphibians and reptiles 36 the primary aquifer that underlies the area. Much of this threat has now been contained as regulations for new and extended quarries have become more tightly drawn. Birds 40 The conservation of the area’s resources is a matter of considerable importance and there are yet more uncertainties in the face of climate change that could have a dramatic impact if temperatures rise according to current predictions. The Future 44 Nevertheless, for many years to come the Magnesian Limestone needs to be protected and its wildlife conserved. The recognition by local people of the importance of caring for their unique natural environment is crucial if their communities are to be truly sustainable. Ten Places to Visit 48 photo: www.wildstock.co.uk Carboniferous Rocks - Fig 2. Horizontal section through Durham Coalfield the world’s great deserts in which sand, Geology of the Durham formed by the wearing away of the hills, The Coal Measures accumulated as long belts of dunes. We see these today as the ‘Yellow Sands’, Magnesian Limestone Most of the coal worked in County that are extensively worked for building Durham occurs within a group of rocks sand in quarries around Quarrington, known to geologists as the Coal Coxhoe and Ferryhill (Fig 3). Evidence of Measures. The coal occurs as thin layers, their wind-borne origin may be seen in by Brian Young or seams, sandwiched between beds of the huge dune-bedding so clearly other rocks such as shale and visible in quarry faces, and in the sandstone. perfectly rounded ‘millet seed’ shape of individual grains. The sands continue at These rocks date back to the later part of the Carboniferous Period of earth history, roughly 316 to 295 million years by enormous rivers carrying sand and Coal Measures rocks lie beneath the Fig 3. Permian Yellow Sands, fossilised sand dunes, being worked for building sand at As the area described in this book ago. At this time, the area that was to silt from uplands in the area now Magnesian Limestone and crop out at Introduction Crime Rigg Quarry, Sherburn comprises the eastern part of the become Great Britain lay almost astride occupied by the Scottish Borders and the surface immediately west of the The special landscape of the Durham Photo: Brian Young Durham Coalfield, before looking more the equator. Vast, low-lying, forest- northern North Sea. The forests Magnesian Limestone escarpment Magnesian Limestone, with its closely at the Magnesian Limestone covered tropical swamps were crossed contained enormous primitive trees, (Fig 2). Apart from in the banks of the distinctive flora and fauna and itself, and in order to understand the including ancestors of the modern club- River Wear at South Hylton, Sunderland interesting social and economic history, coal mining industry that has mosses and conifers, together with and in an old quarry near Shildon, they reflects events and processes that been so important in shaping giant ferns and horsetails (Fig 1). True are rarely exposed in the area, but have shaped this area many millions of years the area, we need to look briefly flowering plants had not yet evolved. been worked in numerous collieries. ago. In order to properly appreciate the at these coal- bearing rocks. Animal life included huge newt-like The best places to see examples of the area as we see it today, we need to amphibians and giant dragonflies. Thick full range of Coal Measures rocks are understand something of the accumulations of peat and leaf litter on old colliery tips and on the beaches of fascinating story of the rocks the forest floor became compressed, the Durham coast, where large amounts beneath our feet. when buried beneath silt and sand, to of spoil were once dumped. form the coal seams we know today. Fossilised leaves and roots from these forests are commonly found in beds of Permian Rocks shale within the Coal Measures. Some The episode of earth history that fine specimens of large petrified logs of followed the Carboniferous is known as a tree known as Cordiaites were found the Permian Period. This lasted from several years ago in an opencast coal pit about 295 to 250 million years ago. It at Priors Close, near Great Lumley. was during this time that the Durham Magnesian Limestone was formed, Near the end of the Carboniferous although a few other events were to Period, as this part of the earth’s crust affect the area before the limestone Fig 1. Artist’s reconstruction shifted northwards, great earth itself was deposited. of the type of lush tropical movements squeezed and folded the forest in which the vegetation The landscape created at the end of that formed the area’s coal coal seams and other rocks, pushing Carboniferous times drifted further seams was deposited, about them up to form hills and mountains. 310 million years ago Weathering and erosion of this new northward to between 10 to 30 degrees landscape set the scene for the next north of the equator during Permian Painting: Elizabeth Pickett period of earth history. times. Northern Europe was then one of 2 3 Photo: Brian Young This desert landscape was eventually Above the Marl Slate occurs a rather Photo: Brian Young Areas of land and sea during Permian times flooded as the waters of the Zechstein complex succession of limestones of Sea, a precursor of the modern North different compositions and textures, Sea, spread rapidly across the area, formed in rather varying conditions ZECHSTEIN SEA reaching as far as the present day beneath the waters of the Zechstein ROCKY HILLS eastern edge of the Pennines (Fig 4). Sea, and collectively termed the PENNINE RIDGE County Durham Unlike the present-day North Sea, this Magnesian Limestone (Fig 7). Barrier Reef was a warm sea that dried up almost Whereas true limestone consists completely on several occasions. almost entirely of the mineral calcite (CaCO3), many of the limestones here The earliest limestone to be deposited, in east Durham contain large probably about 270 million years ago, amounts, or may consist almost was a thin bed of dark grey bituminous exclusively, of the magnesium-rich ROCKY HILLS shaly limestone, known in North-East mineral dolomite (CaMg(CO3)2).