2.3.2 Types of informal names and designations
There are many ways of informally designating geological units, both orally and in writing. This may be done using (a) a lithological or other descriptive designation alone, e.g. the mica schist, the grey shale, the anticline, laminated limestone, etc., (b) rank or unit designations from the formal terminology, or combined with a lithological or other descriptive designation, e.g. the formation, the quartzite member, the nappe series, the moraine ridge, etc., (c) an informal unit designation alone or combined with a lithological or other descriptive designation, e.g. the unit, the division, the limestone unit, the basaltic portion, the sandstone sequence, the greenstone belt, etc., (d) a number and/or letter code combined with formal or informal rank or unit designations, or together with a lithological or some other kind of descriptive designation, e.g. formation A, B-division, moraine c, 3c-stage, 1st conglomerate member, nappe pile 3, etc., (e) position designations such as lower, middle and upper, in conjunction with designations for rank, unit, lithology and so on, e.g. lower sandstone unit, middle tectonostratigraphical unit, upper biozone (if these adjectival designations are used in conjunction with a formal unit name the sub-units are nonetheless informal, e.g. the upper Landersfjorden Formation (øvre Landersfjordformasjonen)), (f) designations from engineering and economic geology, e.g. the ore layer, the oil shale, the quickclay horizon, the lead formation, etc., (g) geographical names (or alternative names on the continental shelf) along with an informal designation for unit, lithology or some other characterizing property, e.g. the Ågotnes sand, the Årungen beds, the Tuddal lava, etc. Such names will structurally resemble formal formation names written by combining a geographical name and the principle lithology (see Section 2.2.2). Because of this, informal names of this nature should be used as little as possible, and their informal status must be emphasized.
Names of informal units are not to be constructed by combining a geographical name with a designation for a fundamental, more highly ranking unit in hierarchical classification systems. This limitation applies to all geological units defined on the basis of time or age (see Table 1 and Section 1.2). Such combinations are to be reserved for formally defined units (see Sections 2.2.2, 2.2.3 and 2.2.4, and ISSC 1976, p. 35). Examples: the Valdres sparagmite (Valdressparagmitten) is an informal designation, but the Valdres Group (Valdresgruppen) is a formal one. The Biri limestone (Birikalken) is an informal designation, but the Biri Formation (Biriformasjonen) is a formal one. The terms the Lathus flow (Lathusstrømmen) or the Lathus member (Lathusleddet) can be used for an informal unit, but not so the Lathus Formation (Lathusformasjonen).
