1.2 Definitions
Geological unit -- In this Code, the term geological unit is used to signify a body of rocks or superficial deposits, a form element, geological structure, or geological time unit which requires a special, recognizable name for use on geological maps, in scientific articles, and in technical or economic reports. Formal unit terms are those used in formal classification systems. Examples are formation, group, suite, biozone, etc.
Rock, bedrock, superficial deposit, type of superficial deposit, etc. -- The term rock is used in this Code for a solid, coherent material consisting of (a) minerals formed by precipitation, crystallization, recrystallization, or cementation of older mineral and rock fragments, (b) glass formed by solidification of magma, and (c) organic material (e.g. coal). A rock constitutes part of the bedrock (berggrunnen). The bedrock is the solid fundament beneath the superficial deposits. In this Code, superficial deposits embody all kinds of loose, incoherent deposits such as clay, sand, gravel, organic material and the like, as well as the weathered, fractured and fragmented uppermost surface of the bedrock. Portions of more or less compacted and cemented material may be found within superficial deposits. A gradual transition from bedrock to superficial deposit is feasible. The term "superficial deposit", as used here, is synonymous with regolith (Bates & Jackson 1980). Type of superficial deposit corresponds to rock and designates a superficial deposit having special characteristics, e.g. a sand deposit, clay deposit, moraine, peat, and the like. Sediment is material which is transported and deposited by ice, water, air, sliding and mass movement, chemical and biochemical precipitation or biological growth. The term sediment is mostly used in connection with unconsolidated deposits, but also when dealing with coherent deposits and sedimentary rocks.
Category -- A category is one or more geological unit(s) having one or more special trait(s) in common. For example, all units of stratified rocks or superficial deposits which are deposited with younger layers above older ones belong to the category of lithostratigraphical units. The Code comprises 17 main categories (see the summaries in Section 1.3 and Table 1).
Class -- A class embodies types of rocks, superficial deposits, form elements, structures or geological time units that are distinguished from other types by having a fundamentally different character or mode of formation. For example, the three classes of rocks are igneous, sedimentary and metamorphic rocks, and the classes of form elements are erosional forms, depositional forms and forms of mixed origin.
Lithology -- Lithology is the combined expression of all the physical properties on the basis of which a rock or sediment can be identified: composition, texture, grain orientation and structures. In an extended sense, lithology also embodies derived properties registered with the help of various measuring techniques: porosity and permeability, chemical, magnetic, electrical, thermic, seismic, gravimetrical and radiological properties.
Lithological units -- Lithological units are geological units that are classified on the basis of their lithological properties. Lithological units comprise both rocks and superficial deposits. Categories of lithological units are lithostratigraphical, lithodemic and pedostratigraphical units.
Stratigraphy -- Stratigraphy is used here as in ISSC (1976), as a science that treats rocks and superficial deposits as beds: their original sequence, absolute age, relative age relationship, form, extent, lithology, fossil content, geophysical and geochemical properties, interpretation of mode of formation and geological history. All classes of rocks and superficial deposits are described and classified stratigraphically.
Stratigraphical division, classification -- Stratigraphical division is the systematic organization of rocks and superficial deposits, as they occur in their stratal successions, into units distinguishable from each other on the basis of their properties and/or boundary relationships. There are many types of stratigraphical division, according to which properties and relationships form the basis for the division.
Stratigraphical unit -- A stratigraphical unit comprises one or more beds distinguished as a distinct unit on the basis of any property or group of properties found in rocks and superficial deposits. The unit constitutes, together with other units, part of the systematical organization of stratal successions on the Earth. The basis for the definition of the unit determines to which category of stratigraphical units it belongs.
Stratigraphical terminology -- Stratigraphical terminology is concerned with terms for types of stratigraphical units. There are usually different unit designations for the individual stratigraphical categories. Such terms can designate the rank of the unit in the classification system and perhaps which position the unit occupies in a hierarchical classification system. Examples of such unit designations are formation, group, biozone, system and stage.
Stratigraphical nomenclature, naming -- Stratigraphical nomenclature is used here to embrace naming of geological units in general, irrespective of category. Nomenclature has to do with the full name of the unit, consisting of a characterizing name and the unit term. There are formal and informal categories of names (see Sections 2.2 and 2.3).
Correlation, comparison -- To correlate is, in a stratigraphical sense, to be able to demonstrate agreement in properties and stratigraphical position between two or more stratigraphical units. Correlations can be made on the basis of lithology (lithostratigraphical correlation), fossils (biostratigraphical correlation), morphology (morphostratigraphical correlation), time (chronostratigraphical correlation) and other properties.
System -- "System" is a formal unit term in the chronostratigraphical classification system. The term is also used in combination with geological type designations in other categories, e.g. fault systems, joint systems and nappe systems. In this Code, "system", used in this wide sense, characterizes a geological unit which embraces rocks, superficial deposits, form elements or structures that are related in mode of formation within a limited time period.
Complex -- "Complex" is a formal unit term in the lithodemic classification system. The term is also used in combination with geological type designations in other categories, e.g. fault complex, joint complex and nappe complex. In this Code, "complex", irrespective of category, characterizes a geological unit which embraces rocks, superficial deposits, form elements or structures, and which is a heterogeneous collection of dissimilar individual elements. The individual elements have either a different age and/or mode of formation, or their relative age relationships are uncertain or unknown.
