Downloaded from http://sp.lyellcollection.org/ at British Geological Survey on June 19, 2014 Geological Society, London, Special Publications An assessment of lithostratigraphy for anthropogenic deposits J. R. Ford, S. J. Price, A. H. Cooper and C. N. Waters Geological Society, London, Special Publications 2014, v.395; p55-89. doi: 10.1144/SP395.12 Email alerting click here to receive free e-mail alerts when service new articles cite this article Permission click here to seek permission to re-use all or request part of this article Subscribe click here to subscribe to Geological Society, London, Special Publications or the Lyell Collection Notes © The Geological Society of London 2014 Downloaded from http://sp.lyellcollection.org/ at British Geological Survey on June 19, 2014 An assessment of lithostratigraphy for anthropogenic deposits J. R. FORD*, S. J. PRICE, A. H. COOPER & C. N. WATERS British Geological Survey, Environmental Science Centre, Nicker Hill, Keyworth, Nottingham NG12 5GG, UK *Corresponding author (e-mail: [email protected]) Abstract: The deliberate anthropogenic movement of reworked natural and novel manufactured materials represents a novel sedimentary environment associated with mining, waste disposal, con- struction and urbanization. Anthropogenic deposits display distinctive engineering and environ- mental 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 anthro- pogenic 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 designa- tion 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 anthropo- genic deposits. A practical alternative may be to establish an ‘anthrostratigraphical’ approach, or ‘anthrostratigraphy’. Gold Open Access: This article is published under the terms of the CC-BY 3.0 license. Human activity has modified the geological struc- including land-use planning, development and ture of the Earth and continues to do so at an accel- archaeological study (Edgeworth 2013). erating rate. Humans are now the major driving Establishing the geometrical shape and spatial force behind geological change, responsible for relationships of artificially modified ground re- man-made unconformities and the modification of quires appropriate systems of characterization and sedimentary patterns. The anthropogenic modifi- classification. Existing stratigraphical classifica- cation of sedimentary patterns can be attributed tion schemes used for the geological mapping and to two overlapping processes (Price et al. 2011; modelling of artificially modified ground in Great Zalasiewicz et al. 2011): (1) the creation of novel Britain are largely based on morphogenetic attri- sedimentary environments and sediments (artifi- butes (British Geological Survey 1995; McMillan cially modified ground), and which is the focus of & Powell 1999; Price et al. 2004; Ford et al. this paper; (2) modifications to natural sedimentary 2010a; Price et al. 2011). Morphogenetic classifi- environments through processes such as damm- cation offers a practical and effective means of dif- ing, coastal reclamation or straightening of rivers ferentiating broadly defined classes of artificially (Syvitski & Kettner 2011). modified ground, including worked ground, made In many novel sedimentary environments, such ground and infilled ground. In contrast, a lithostrati- as urban areas, the landscape and shallow sub- graphical classification is used for bedrock and, surface is dominated by anthropogenic processes, increasingly, for natural superficial deposits based including erosion (i.e. excavation) and anthro- essentially on lithological characteristics and spa- pogenic sedimentation (i.e. deposits of ‘made tial relationships (Salvador 1994). Unlike litho- ground’). This presents a range of potential envi- stratigraphy, a morphogenetic approach does not ronmental and engineering challenges including generally allow different phases of artificial ground unpredictable ground conditions, geological haz- or lithologically distinct anthropogenic deposits to ards and contamination (Rosenbaum et al. 2003). be differentiated, nor allow the changing magnitude Anthropogenically modified ground can also offer of anthropogenic transformation of the landscape a record of landscape evolution and the impacts of to be determined. A lithostratigraphical approach humans on the natural environment. As such, a to classifying anthropogenic deposits could contrib- range of approaches exist to characterize and clas- ute to an improved understanding of the role of sify artificially modified ground to inform activities humans as major geological and geomorphological From:Waters, C. N., Zalasiewicz, J. A., Williams, M., Ellis,M.A.&Snelling, A. M. (eds) 2014. A Stratigraphical Basis for the Anthropocene. Geological Society, London, Special Publications, 395, 55–89. First published online January 23, 2014, updated April 8, 2014, http://dx.doi.org/10.1144/SP395.12 # The Authors 2014. Publishing disclaimer: www.geolsoc.org.uk/pub_ethics Downloaded from http://sp.lyellcollection.org/ at British Geological Survey on June 19, 2014 56 J. R. FORD ET AL. agents in the Anthropocene (Price et al. 2011). The The aim of this paper is to determine whether Anthropocene, if defined, will be a chrono- anthropogenic deposits can be classified using the stratigraphical unit representing a specified time same lithostratigraphical procedures employed for interval. Throughout the geological column, from natural deposits. The purpose is not to define a the late twentieth century onwards, chronostra- lithostratigraphical classification for anthropogenic tigraphical and lithostratigraphical schemes have deposits, but to consider whether such an approach been developed separately. Chronostratigraphical could be used. It discusses where, or in what circum- units have typically been recognized as a response stances, it would work and where it would fail. It to a significant global event, particularly in the also looks at how elements of a pure lithostrati- context of changing biotic communities. Conse- graphical approach can be adapted or incorporated quently, the study of the lithostratigraphy of anthro- with other classification schemes to offer the func- pogenic deposits will not be used to define this new tionality necessary to characterize, quantify and age. However, changes in the nature and extent of investigate the recent geological record, and con- such deposits, discernible through lithostratigraphy, tribute to the study of the Anthropocene. could provide one line of evidence to consider This paper is largely based on the study of in deciding if, and how, such a time unit should anthropogenic deposits in Great Britain, including be defined. their lithostratigraphical classification to support Novel sedimentary environments and anthropo- systematic survey and three-dimensional (3D) geo- genic deposits share many similarities with ancient logical modelling. However, the value of lithostrati- depositional systems, including lithological char- graphical classification in recording and interpreting acteristics and successions that conform locally to anthropogenic successions in sections and boreholes the Law (or Principle) of Superposition. This sug- and other ‘non-geographical’ contexts is also con- gests that a lithostratigraphical approach may be sidered. Examples from diverse geographical set- applicable. However, several characteristics of tings highlight the global relevance of establishing anthropogenic deposits present a challenge to lithos- effective systems for their classification. tratigraphical classification, for example: † Terrestrial anthropogenic deposits vary greatly Novel sedimentary environments, in both lateral and vertical extent. Although artificially modified ground and sequences can attain thicknesses of 65 m or anthropogenic deposits more in Great Britain, component units are com- monly only a few metres thick. It has been recognized that anthropogenic processes † By their nature, many anthropogenic units are that result in the creation of sediments, erosive fea- strictly allostratigraphical; that is, defined and tures and associated landforms can be broadly clas- identified on the basis of bounding disconti- sified in two main types (Szabo´ 2010; Price et al. nuities. However, allostratigraphy has not been 2011; Zalasiewicz et al. 2011). The first type com- popularly applied in Great Britain (Rawson prises those anthropogenic activities that are delib- et al. 2002). The bounding discontinuities can erate, direct and intentional in their modification be defined as unconformities (e.g.