Step Graben Formation

Formal (Van Adrichem Boogaert & Kouwe 1995).
Lithological description

Red- to orange-brown, grey, or variegated, silty to fine-grained sandy mudstones. Intercalated sandstone beds consist of 2 to 10 m thick sheets. The sands are white, grey or red-brown, subangular to rounded, moderately- to well-sorted, fine- to medium-grained, with coarse-grained, pebbly intercalations. Carbonaceous matter is common in some grey intervals, specifically in the lower section. Coal seams are restricted to a few localities and specific stratigraphic horizons. Some thin, light-grey, dolomitic limestone beds can be encountered.

Depositional setting

Well-drained flood plain. During certain periods of elevated base level, swamp areas with poorly-drained soils formed. Mudstone with thin sheet sandstones: distal depositional setting. Sandstones: sheet floods or small-scale fluvial channel systems (Leeder 1990; Besly 1988; Besly 1993).

Definition of lower boundary

Placed at the top of the uppermost massive sandstone bed of the Hospital Ground Formation, which is overlain by a mudstone interval of more than 60 m thick. Locally, the Step Graben Formation may rest directly on the Maurits Formation. This contact can be conformable or unconformable. In the vicinity of the Mid North Sea High and Schill Grund High, the formation might rest unconformably on older formations, analogous to the Brig Formation in the UK offshore (Cameron 1992).

Definition of upper boundary

Covered unconformably by the Upper Rotliegend Group. The top of the formation is constituted by the Saalian Unconformity.

Thickness indication
Up to 217 m.
Geographical distribution
Regional correlation
UK: Upper Ketch Unit of the Schooner Formation; GER: ?; BEL: ?.
Depth (thickness) AH:
3462 - 3641m (179 m)
Depth (thickness) AH:
3983 - 4058 m (75 m)
Depth (thickness) AH:
3651 - 3735 (84 m)
Origin of name
Named after the Step Graben, a fault block situated between the Elbow Spit High and the Central Graben. The formation has also been found in the vicinity of this area.
Previous name(s)
Reviewed by (date)
Tom van Hoof (2017).
Leeder, M.R. & Hardman, M. 1990. Carboniferous of the Southern North Sea basin and controls on hydrocarbon prospectivity - ln: Hardman, R.F.P. & Brooks, J. (eds.): Tectonic events responsible for Britain's oil and gas reserves - Geol. Soc. London, Spec. Publ., 55,
Besly, B.M. 1988. Palaeogeographic implications of late Westphalian to early Permian red beds, central England. ln: Besly, B.M. & Kelling, G. (eds.), Sedimentation in a synorogenic basin complex - the Upper Carboniferous of Northwest Europe, 200 - 221.
Besly, B.M., Burley, S.D., Turner, P. 1993. The late Carboniferous 'Barren Red Bed' play of the Silver Pit area, Southern North Sea. ln: Parker, J.R., (ed.): Petroleum Geology of Northwest Europe, Proc. 4th Conference, Geological Society London, 727-740.
Cameron, T.D.J., Crosby, A., Balson, P.S., Jeffrey, D.H., Lott, G.K., Bulat, J., & Harrison, D.J. 1992. U.K. Offshore Regional Report: Geology of the Southern North Sea - British Geol. Surv., HMSO, London, 152 pp.
Van Adrichem Boogaert, H.A. & Kouwe, W.F.P. 1995. Stratigraphic nomenclature of The Netherlands, revision and update by RGD and NOGEPA, Section C, Silesian. Mededelingen Rijks Geologische Dienst, 50, 1-40.
Cite as
TNO-GDN ([YEAR]). Step Graben Formation. In: Stratigraphic Nomenclature of the Netherlands, TNO – Geological Survey of the Netherlands. Accessed on [DATE] from