A.H. Cooper

Humans as major geological and geomorphological agents in the Anthropocene: the significance of artificial ground in Great Britain

Since the first prehistoric people started to dig for stone to make implements, rather than pick up loose material, humans have modified the landscape through excavation of rock and soil, generation of waste and creation of artificial ground. In Great Britain over the past 200 years, people have excavated, moved and built up the equivalent of at least six times the volume of Ben Nevis. It is estimated that the worldwide deliberate annual shift of sediment by human activity is 57 000 Mt (million tonnes) and exceeds that of transport by rivers to the oceans (22 000 Mt) almost by a factor of three. Humans sculpt and transform the landscape through the physical modification of the shape and properties of the ground. As such, humans are geological and geomorphological agents and the dominant factor in landscape evolution through settlement and widespread industrialization and urbanization. The most significant impact of this has been since the onset of the Industrial Revolution in the eighteenth century, coincident with increased release of greenhouse gases to the atmosphere. The anthropogenic sedimentological record, therefore, provides a marker on which to characterize the Anthropocene.

The stratigraphy, correlation, provenance and palaeogeography of the Skiddaw Group (Ordovician) in the English Lake District

A new lithostratigraphy is presented for the Skiddaw Group (lower Ordovician) of the English Lake District. Two stratigraphical belts are described. Five formations are defined in the Northern Fells Belt, ranging in age from Tremadoc to early Llanvirn. They are all mudstone or sandstone dominated, of turbidite origin; in ascending order they are named the Bitter Beck, Watch Hill, Hope Beck, Loweswater and Kirk Stile formations. Two formations are defined in the Central Fells Belt, ranging in age from late Arenig to Llanvirn. These are the Buttermere Formation - a major olistostrome deposit - overlain by the Tarn Moor Formation, consisting of turbidite mudstones with volcaniclastic turbidite sandstone beds. A revised graptolite and new acritarch biostratigraphy for the Skiddaw Group is presented with eight graptolite biozones and thirteen acritarch assemblages and sub-assemblages. The provenance of the group is assessed from detailed petrographical and geochemical work. This suggests derivation, in the early Ordovician, largely from an old inactive continental arc terrane lying to the south-east, with the appearance of juvenile volcanic material in the Llanvirn. Comparisons and correlations of the Skiddaw Group are made with the Isle of Man and eastern Ireland.

Evaporite Dissolution Subsidence in the Historical City of Calatayud, Spain: Damage Appraisal and Prevention

Calatayud in NE Spain is an historically important city built on recent alluvial deposits underlain by gypsum and other soluble rocks. Since its foundation by the Muslims in 716 A.D., the city development has been strongly influenced by geohazards including flooding, subsidence and slope movements. Most of the flooding problems have been mitigated by diversion of the local drainage. However, dissolution of the evaporite bedrock in the urban areas continually causes subsidence and triggers rock-falls from the gypsum cliffs overlooking the city. Subsidence is also caused by the hydrocollapse of gypsiferous silt in the alluvial fan deposits. Building damage in the city was surveyed using a classification scheme developed originally to record damage in British coal mining areas. The Calatayud damage survey shows that the worst building subsidence is concentrated along the line of a buried channel that runs underneath the gypsiferous silt alluvial fan. Natural subsurface drainage causes the dissolution and subsidence, which is aggravated by leakage from water and sewage pipes. Some building damage has been exacerbated during reconstruction by incomplete piling leaving buildings partially unsupported. Mitigation measures include the control of water leakage by the installation of flexible service pipes. Careful construction techniques are needed for both conservation and new developments, especially when piled and minipiled foundations are used. Geomorphological mapping is cost-effective in helping to locate and avoid the zones of subsidence for future development.

Classification of artificial (man-made) ground

Abstract The legacy inherited from anthropogenic processes needs to be addressed in order to provide reliable and up-to-date ground information relevant to development and regeneration in the urban environment. The legacy includes voids as well as anthropogenic deposits (artificial ground). Their characteristics derive from former quarrying and mining activities industrial processes creating derelict ground, variably consolidated made ground, and contaminated groundwater and soils. All need to be systematically assessed to inform the planning process and provide the basis for engineering solutions. Site-specific investigation needs to be conducted on the back of good quality geoscientific data. This comes from ‘field’ survey, remotely sensed data interpretation, historical maps, soil geochemical sampling, and geotechnical investigation. Three-dimensional and, in the future, four dimensional, characterization of superficial deposits is required to reach an understanding of the potential spatial lithological variability of artificial ground and the geometry of important surfaces, i.e. the boundary conditions. The classification scheme for artificial ground outlined in this paper and adopted by the British Geological Survey, will help in achieving this understanding.

Subsidence hazards caused by the dissolution of Permian gypsum in England: geology, investigation and remediation

Abstract About every three years natural catastrophic subsidence, caused by gypsum dissolution, occurs in the vicinity of Ripon, North Yorkshire, England. Holes up to 35 m across and 20 m deep have appeared without warning. In the past 150 years, 30 major collapses have occurred, and in the last ten years the resulting damage to property is estimated at about £1000000. Subsidence, associated with the collapse of caves resulting from gypsum dissolution in the Permian rocks of eastern England, occurs in a belt about 3 km wide and over 100 km long. Gypsum (CaS04.2H20) dissolves rapidly in flowing water and the cave systems responsible for the subsidence are constantly enlarging, causing a continuing subsidence problem. Difficult ground conditions are associated with caves, subsidence breccia pipes (collapsed areas of brecciated and foundered material), crown holes and post-subsidence fill deposits. Site investigation methods that have been used to define and examine the subsidence features include microgravity and resistivity geophysical techniques, plus more conventional investigation by drilling and probing. Remedial measures are difficult, and both grouting and deep piling are not generally practical. In more recent times careful attention has been paid to the location for development and the construction of low-weight structures with spread foundations designed to span any subsidence features that may potentially develop.

Planning for gypsum geohazards in Lithuania and England

The rapid underground dissolution of gypsum, and the evolution of the gypsum karst in Lithuania and England, results in subsidence problems which can make construction difficult. The natural dissolution yields sulphate-rich groundwater of poor quality and the karst is susceptible to the rapid transmission of pollutants. In the north of Lithuania gypsum karst is developed in Devonian gypsum. Here the towns of Birai, Pasvalys and the surrounding countryside suffer subsidence and some buildings have been damaged. The majority of the potable water in these areas is derived from groundwater extracted from sandstone sequences that underlie the gypsum. In Lithuania conservation measures have been introduced to control agriculture and prevent pollution of the gypsum karst. These measures include environmentally-friendly farming, restrictions on land use and exclusion zones around subsidence hollows. In England subsidence caused by the dissolution of Permian gypsum has caused severe problems in the vicinity of the town of Ripon. Numerous buildings have been damaged and new sites are difficult to develop. Here formal planning regulations have recently been introduced to help to protect against the worst effects of subsidence resulting from gypsum dissolution.

An assessment of lithostratigraphy for anthropogenic deposits

Abstract The deliberate anthropogenic movement of reworked natural and novel manufactured materials represents a novel sedimentary environment associated with mining, waste disposal, construction and urbanization. Anthropogenic deposits display distinctive engineering and environmental properties, and can be of archaeological importance. This paper shows that temporal changes in the scale and lithological character of anthropogenic deposits may be indicative of the Anthropocene. However, the stratigraphy of such deposits is not readily described by existing classification schemes, which do not differentiate separate phases or lithologically distinct deposits beyond a local scale. Lithostratigraphy is a scalable, hierarchical classification used to distinguish successive and lithologically distinct natural deposits. Many natural and anthropogenic deposits exhibit common characteristics; they typically conform to the Law (or Principle) of Superposition and exhibit lithological distinction. The lithostratigraphical classification of surficial anthropogenic deposits may be effective, although defined units may be significantly thinner and far less continuous than those defined for natural deposits. Further challenges include the designation of stratotypes, accommodating the highly diachronous nature of anthropogenic deposits and the common presence of disconformities. International lithostratigraphical guidelines would require significant modification before being effective for the classification of anthropogenic deposits. A practical alternative may be to establish an ‘anthrostratigraphical’ approach, or ‘anthrostratigraphy’.

The classification, recording, databasing and use of information about building damage caused by subsidence and landslides

Building damage as a result of subsidence and lateral movement can be caused by numerous mechanisms including mining, dissolution of soluble rocks, shrink–swell of clays and landslides. In many instances, the distribution and severity of the damage caused can be diagnostic of the underlying geological condition and can be used as an aid to geological and geomorphological mapping. Many rigid buildings are sensitive to movement, meaning that careful surveys can delineate fine details that can be compiled to identify broader patterns of mass-movement. This paper discusses how damage has been recorded in the past and presents a unified scheme that is based mainly on UK and Italian practice and that can be applied to most situations. It broadens the existing schemes to include the assessment of damage to infrastructure (such as roads and pavements), which are also sensitive to movements; it also extends the existing schemes to include more serious building damage. In this way it unifies the current, disparate approaches and extends the usage of the semi-quantified approach to damage assessment. The damage assessment lends itself to storage in a database that can be interrogated, displayed and interpreted using a geographical information system (GIS).

Road and bridge construction across gypsum karst in England

Gypsum karst problems in the Permian and Triassic sequences of England have caused difficult conditions for bridge and road construction. In Northern England, the Ripon Bypass crosses Permian strata affected by active gypsum karst and severe subsidence problems. Here, the initial borehole site investigation for the road was supplemented by resistivity tomography studies. The roadway was reinforced with two layers of tensile membrane material within the earth embankment. This will prevent dangerous catastrophic collapse, but will allow sagging to show where problems exist. The River Ure Bridge was constructed across an area of subsidence pipes filled with alluvial deposits. It was built with extra strength, larger than normal foundations. If one pier fails, the bridge is designed for adjacent arches to span the gap without collapse. The bridge piers are also fitted with electronic load monitoring to warn of failure. In the Midlands area of England, road construction over Triassic gypsum has required a phase of ground improvement on the Derby Southern Bypass. Here, the gypsum caps a hill where it was formerly mined; it dips through a karstic dissolution zone into an area of complete dissolution and collapse. The road and an associated flyover were built across these ground conditions. A major grouting program before the earthworks began treated the cavities in the mine workings and the cavernous margin of the gypsum mass. Within the karstic dissolution zone, gypsum blocks and cavities along the route were identified by conductivity and resistivity geophysical surveys, excavated and backfilled. In the areas of complete dissolution and collapse, the road foundation was strengthened with vibrated stone columns and a reinforced concrete road deck was used.

The age and correlation of Skiddaw Group (early Ordovician) sediments in the Cross Fell inlier (northern England)

The Skiddaw Group in the Cross Fell inlier comprises the Catterpallot Formation of latest Tremadoc or earliest Arenig age, the Murton Formation of Arenig age, and the Kirkland Formation of early Llanvirn age. Each of these formations can be correlated with formations in the Skiddaw Group of the Lake District. The faulted contact of the Catterpallot and Kirkland formations is the probable extension of the Causey Pike Fault (CPF), which separates two distinct sequences in the Skiddaw inlier of the northern Lake District. Contrasts across the CPF in the Cross Fell inlier reflect those seen in the Skiddaw inlier. The CPF is a major basement structure, separating markedly different successions in the Ordovician strata of northern England.