3.7.17 Syncline (Synklinal)
3.7.17.1 A syncline is a fold which is usually concave upwards, and which has the stratigraphically youngest beds in its core. It is a structural form element that need not be, or have been, a landform.
3.7.17.2 Syncline could be a genetical term for a negative structural form element.
3.7.17.3 No limitations are placed on the dimensions of a syncline.
3.7.17.4 A syncline is mappable with the help of geological and/or geophysical methods.
3.7.17.5 A syncline can include several smaller structural elements.
3.7.17.6 A syncline can be given a formal or an informal name in accordance with the "general rules for naming and defining geological units" (Chap. 2) and the rules for naming geological form units (Section 3.7.1). The proper name (Section 2.2.2) is placed between the words "the ... Syncline" (formal) in the compound name.
3.7.17.7.a A synform (synform) is a fold which is concave upwards, and in which the beds are inverted or their relative age is unknown.
3.7.17.7.b A synclinorium (synklinorium) is a negative, structural form element of regional extent composed of several smaller folds, and in which the stratigraphically youngest beds occur in the core.
3.7.17.7.c Synforms and synclinoria can be given formal and informal names.
3.7.17.8 Examples: The ¥stmarka Syncline (¥stmarksynklinalen), defined by Graversen (1984), is found in the basement in South Norway. Foslie (1949) named a prominent fold in the Caledonian nappes of Ofoten, North Norway, Håfjellmulden (the Håfjell syncline), but it has now been redefined (Gustavson 1972) as the Ofoten Synform (Ofotsynformen).
3.7.17.9 Key reference: Bates & Jackson (1980).