3.7.16 Graben (Graben)
3.7.16.1 A graben is an elongate, negative structural form element bounded by parallel or nearly parallel faults along one or both flanks. It need not be, or have been, a landform.
3.7.16.2 Graben is a genetical term for a negative structural form element.
3.7.16.3 No limitations are placed on the dimensions of a graben.
3.7.16.4 Grabens are mappable with the help of geomorphological, geological and/or geophysical methods.
3.7.16.5 A graben may occur as an isolated, independent form element, but can also be part of a larger geomorphological and/or structural feature. A graben will often be divisible into smaller form elements.
3.7.16.6 A graben 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 elements (Section 3.7.1). The proper name (Section 2.2.2) is placed between the words "the ... Graben" (formal) in the compound name.
3.7.16.7 The following form elements are also covered by the general term "graben":
3.7.16.7.a Rift (rift), which is a long, narrow depression bounded along its flanks by normal faults. It is a graben of regional extent, and marks a zone where the lithosphere has been completely or partially ruptured during extension.
3.7.16.7.b Aulacogen (aulakogen), which is an elongate, tectonic depression bounded by convergent normal faults. It is a graben of regional extent on a continent, and opens towards the sea.
3.7.16.7.c Pull-apart basin (skjærbasseng), which is a rhomb-shaped graben formed between two strike-slip faults.
3.7.16.7.d Rift valley (riftdal), which is a negative landform (depression) developed along a rift.
3.7.16.7.e Half graben (halvgraben), which is a graben bounded by one or more parallel, or nearly parallel, faults along the one long side and by a flexure along the other.
3.7.16.7.f Rifts, aulacogens, pull-apart basins, rift valleys and half grabens can be given formal or informal names.
3.7.16.8 Examples: The Viking Graben (Vikinggrabenen) and Central Graben (Sentralgrabenen) are two prominent graben structures in the North Sea (Ziegler 1982). The Oslo Graben is a palaeograben which today largely stands out as a series of highs because of erosion down to the massive, Permian plutons inside the graben structure.
3.7.16.9 Key reference: Bates & Jackson (1980).