BGS Rock Classification Scheme — further details

Volume 1 — Classification of igneous rocks

The RCS volume dealing with igneous materials is based to a large extent on the recommendations of the International Union of Geological Sciences (IUGS) Subcommission on the Systematics of Igneous Rocks (Le Maitre [editor] et al., 1st edition 1989; 2nd edition, 2002). However, the BGS scheme contains many changes to, and refinements of, the IUGS recommendations. Perhaps the most significant differences are that the RCS is built around a formal structure, namely a hierarchical classification tree in which igneous materials are classified in nine ranks, and that the RCS introduces a formal system for naming geological materials in a consistent, informative and unambiguous manner.

Volume 2 — Classification of metamorphic rocks

The diversity of metamorphic rocks results from the combined effects of a range of tectonic and/or metamorphic processes acting on a wide range of protolilths. The names that have been given to metamorphic rocks are similarly diverse. The objective of this scheme is to introduce a system of nomenclature that is based as far as possible on descriptive attributes that will be informative to both specialist and non-specialist users and allow any rock to be placed easily into its position in the hierarchy. There are sections on nomenclature, rocks with sedimentary, volcaniclastic and igneous protoliths, rocks with unknown protolith, mechanically broken and reconstituted rocks, metasomatic and hydrothermal rocks, special case metamorphic rocks and qualifiers. The report, issued here as BGS Research Report RR 99-02, has nine figures, seven tables and an appendix listing approved rock names.

Volume 3 — Classification of sediments and sedimentary rocks

Existing sediment and sedimentary rock nomenclature has been based on composition, texture and other physical attributes as well as depositional environment, genetic relationships and local economic importance. A consistent, workable classification for all sediments and sedimentary rocks needs a set of unifying boundary conditions: this classification attempts to do this. The sediment and sedimentary rock names used are descriptive and it should be possible to classify and name any sediment or sedimentary rock without knowledge of its field setting and without making assumptions about its mode of origin. There are sections on siliciclastics, carbonates, dolomites, phosphates, iron sediments and ironstones, organic rich sediments and rocks, non-carbonate salts, non-clastic siliceous sediments and sedimentary rocks, miscellaneous hydroxides and oxides, sediments and rocks based on grain size, hybrid sediments or sedimentary rocks, volcaniclastics and qualifiers. The report, issued here as BGS Research Report RR 99-03, includes 14 figures and 12 tables.

Volume 4 — Classification of artificial man-made ground and natural superficial deposits

This report describes the BGS classification schemes for superficial deposits of Pleistocene and Recent age comprising artificial (man-made ground) and natural superficial deposits. They are designed to be used and interpreted by both geologists and non-geologists to allow thematic material comprising identified classes of superficial deposits to be extracted from geological maps and other data-sets. The schemes can be developed further to other classes of materials particularly from overseas tropical and sub-tropical land, shelf and deep-sea areas. In Britain traditional onshore investigations of the superficial deposits have employed a morphogenetic and lithogenetic terminology resulting in an amalgam of terms with a dominantly genetic basis. This report adopts a similarly genetic approach, however it is recognised that an objective description involving sedimentological, structural, physical and chemical criteria to construct lithofacies associations is desirable and reference to such schemes is made where appropriate. The report, issued here as BGS Research Report RR 99-04, includes 26 tables and 16 figures.

BGS scheme for classifying discontinuities and fillings

This report presents a scheme for classifying and naming geological discontinuities and their fillings, and provides guidance for describing discontinuities in rock masses. The scheme is a new BGS corporate standard analogous to more established standards like the BGS Rock Classification Scheme. Its purpose is to provide geologists with the means to collect and store discontinuity and filling data succinctly and consistently, in any setting and at any scale; to supply a set of approved terms and their definitions to the dictionaries that support BGS databases, and to permit BGS staff, customers and other users to better understand BGS outputs that incorporate discontinuity data.

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