Katy Freeborough

Potential and pitfalls in establishing the provenance of earth-related samples in forensic investigations

ABSTRACT: Earth scientists are often asked to establish or constrain the likely provenance of very small quantities of earth‐related material as part of a forensic investigation. We tested the independent and collective interpretations of four experts with differing analytical skills in the prediction of sample provenance for three samples from different environmental settings. The methods used were X‐ray diffraction, scanning electron microscopy, the assessment of pollen assemblages, and structural characterization of organic matter at the molecular level. Independent interpretations were less accurate than those where multiple techniques were combined. Collective interpretation was very effective in the assessment of provenance for two of the three sites where the mineralogy and plant communities were distinctive. At the other site, although the mineralogical analysis correctly identified the Triassic mudstone soil parent material, Carboniferous spores from domestic coal were initially interpreted as deriving directly from bedrock. Such an interpretation could be a common pitfall owing to anthropogenic redistribution of material such as coal.

Monitoring coastal change using terrestrial LiDAR

Abstract The paper describes recent applications by the British Geological Survey (BGS) of the technique of mobile terrestrial Light Detection And Ranging (LiDAR) surveying to monitor various geomorphological changes on English coasts and estuaries. These include cliff recession, landslides and flood defences, and are usually sited at remote locations undergoing dynamic processes with no fixed reference points. Advantages, disadvantages and some practical problems are discussed. The role of GPS in laser scanning is described.

Antecedent Precipitation as a Potential Proxy for Landslide Incidence in South West United Kingdom

This paper considers the effects of antecedent precipitation on landslide incidence in the United Kingdom. During 2012–2013 an extraordinary amount of precipitation resulted in an increase in the number of landslides reported in the UK, highlighting the importance of hydrogeological triggering. Slope failures (landslides on engineered slopes) in particular caused widespread disruption to transport services and damage to property. SW England and S Wales were most affected. Easy-to-use and accessible indicators of potential landslide activity are required for planning, preparedness and response and therefore analyses have been carried out to determine whether antecedent effective precipitation can be used as a proxy for landslide incidence. It is shown that for all landslides long-term antecedent precipitation provides an important preparatory factor and that relatively small landslides, such as slope failures, occur within a short period of time following subsequent heavy precipitation. Deep-seated, rotational landslides have a longer response time, as their pathway to instability follows a much more complex hydrogeological response. Statistical analyses of the British Geological Survey landslide database and of weather records have enabled determination of the probability of at least one landslide occurring based on antecedent precipitation signals for SW England and S Wales. This ongoing research is of part of a suite of analyses to provide tools to identify the likelihood of regional landslide occurrence in the United Kingdom.

The occurrence of dinoflagellate cysts in calcareous/siliceous microfossil preparations from the Eocene of southeast England

INTRODUCTION During routine analysis of some calcareous and siliceous microbiotas from the London Clay Formation of southeast England (Wilkinson, 2004a, b), some extremely well-preserved, dinoflagellate cysts were observed. These are all large, chorate (spine-bearing) forms, the overwhelming majority of which are referable to Cordosphaeridium gracile (Eisenack, 1954) Davey & Williams, 1966 (Fig. 1). This observation confirms that palynomorphs can be extracted effectively from clay-rich samples using a combination of clay deflocculation and sieving, as described recently by Riding & Kyffin-Hughes (2004). PROCESSING The London Clay Formation from 25 localities in southeast England was processed for calcareous and siliceous microfossils (diatoms, foraminifera, ostracods and radiolaria) (Wilkinson, 2004a, b). The standard British Geological Survey (BGS) procedure for the extraction of calcareous/siliceous microfossils from poorly- or non-indurated sediments was used. Samples were disaggregated by soaking in a mixture of warm water and detergent and agitated periodically. The majority of the clay fraction was removed using a 72 μm sieve. The residue was then boiled in sodium hexametaphosphate [(NaPO3)6] before being sieved again and dried. The sieving will have removed the majority of the palynomorphs, except the larger dinoflagellate cysts. Virtually all pollen and spores and most dinoflagellate cysts of this age are less than 72 μm in at least one dimension. MICROFOSSIL ASSEMBLAGES Specimens of Cordosphaeridium gracile were recovered from three clay quarries. These are Brambledown Pit, Kent [TQ 967 715], Bull’s Lodge Pit, Chelmsford, Essex [TL 7470 0850] and Heckfordbridge Pit, Colchester, Essex [TL 9550 2260], although only two are discussed here …

A national assessment of landslide hazard from Outside Party Slopes to the rail network of Great Britain

In recent years, a number of high profile landslide events have caused disruption, derailments or damage to railway infrastructure in Great Britain. A landslide susceptibility model of the entire railway network was created, designed to give a national overview of potential landslide hazard originating from Outside Party Slopes. The current assessment was compiled using Geographic Information System (GIS) techniques and desktop modelling to apply a structured analysis of each buffered Earthwork Inspection 5 Chain (c. 100 m; EI5C). Data analysed along the network included the BGS GeoSure instability model and newly updated national models for debris flow, earth flow and rock fall, supported by historical landslide data. In order to further focus the Outside Party Slope zone, a buffer of External Natural Geological Influence (BENGI) was created using a 5 m Digital Terrain Model. Landslide susceptibility for each EI5C was categorized using a ‘Classification of Hazards on Outside Party Slopes’ (CHOPS) score; representing the modelled potential for landslide hazard. The outputs were combined as a series of matrices to present the CHOPS and Network Rail Derailment Criticality Band interactions. This research will allow further focused analysis of the network, in order to prioritize and direct future investigation and policy decisions.

Creation of a National Landslide Domain Map to Aid Susceptibility Mapping in Great Britain

The need to develop a national map that characterises landslides across Great Britain has long been recognised by the British Geological Survey as part of its strategic role providing hazard information to stakeholders. Hierarchical landslide domains represent areas of similar physiographic, meteorological, climatic and geological characteristics that shaped the style of landsliding. Developed to underpin current research into how different types of landslides and terrains will be affected by changing environmental conditions, the map further assists development of a national landslide susceptibility map with conditioning factors tailored to a specific domain. This paper considers the role of national-scale land systems mapping to create a Landslide Domain Map, the refinement of a national model using landslide inventories to better reflect the spatial extent and characteristics of landslides within domains. The distribution of landsliding in Great Britain is a product of the complex range of lithologies and geomorphological processes active under a range of climatic conditions. The domains represent landslides across a series of unstable slopes ranging from very large, ancient landslides formed under periglacial climate conditions to small, modern failures, particularly along transport infrastructure corridors. Although analysis of the National Landslide Database broadly informed the nature of landsliding within a specific domain, expert knowledge was needed to supplement it especially in areas where recent mapping had not taken place. Targeted data collection is planned in data-poor domains to supplement the database. Further domain-specific research is ongoing and includes development of semi-empirical process-specific models involving the weighting of critical factors in order to refine the current national landslide susceptibility map, GeoSure. As an example of this refinement, this paper discusses an improved debris flow model for the Scottish Highlands.