Main Buntsandstein Subgroup RBM

 

Premise The Main Buntsandstein was formally introduced as a formation by NAM and RGD (1980) for the German Middle Buntsandstein interval, excluding the Solling sequence. All members of the former Main Buntsandstein. Formation were arranged in sandstone-clay/siltstone couplets. For practical purposes, these couplets have now each received formation status. The status of the Main Buntsandstein Formation was raised accordingly to subgroup level. In the present classification the Main Buntsandstein Subgroup includes the main part of the former Middle Bunter Formation of NAM and RGD (1980) .
Derivatio nominis Named derived from the German lithostratigraphic term ‘Buntsandstein’ for the Lower Triassic red beds. The main sandy development occurred in the Middle Buntsandstein.
Type section Location map See figure (pdf)
  Well Blijham-1 (pdf)
  Location N 53°05’40.9
E 07°04’40.0
  Depth 2736 to 2898 m
  Length 162 m along hole
  Reference (amended after NAM and RGD (1980) )
Additional section Location map See figure (pdf)
  Well L02-01 (pdf)
  Location N 53°57’14.0
E 04°30’47.0
  Depth 3970 to 4205 m
  Length 235 m along hole
  Reference (amended after NAM and RGD (1980) )
  Well Buurmalsen-1 (pdf)
  Location N 51°54’18.7
E 05°18’49.2
  Depth 1387 to 1576 m
  Length 189 m along hole
  Well Strijen West-1 (pdf)
  Location N 51°44’41.0
E 04°31’14.3
  Depth 2535 to 2728 m
  Length 193 m along hole
Definition Alternating succession of often anhydritic, grey to reddish-brown sandstones and silty claystones, containing occasionally some intercalated oolitic limestone beds.
Upper Boundary The unit comprises the strata between the Lower Buntsandstein Formation and the Solling Formation of the Upper Germanic Trias Group.
Lower Boundary The lower boundary is placed at the base of the lowermost thick sandstone bed and the upper boundary at the base of the Solling Formation, which is generally a well recognisable, regional marker. As a result of differential pre-Solling erosion, each formation of the Main Buntsandstein Subgroup may be unconformably overlain by the Solling Formation. Along the basin margin, where sandy sediments prevail, it may be difficult to distinguish the boundaries between the formations in the Main Buntsandstein Subgroup, and to discern the base of the Solling Formation. This is particularly true for well sections that are studied in isolation. In such cases it is possible to lump these formations (Volpriehausen, detfurth and Hardegsen) together with the Basal Solling Sandstone Member into an informal unit: the Middle Bunter sandstone, which is for the major part the equivalent of the Middle Bunter Formation of the old nomenclature of NAM and RGD (1980) ).
Distribution The subgroup has a wide distribution in the Dutch subsurface. On the Netherlands Swell the thickness of the subgroup is much reduced. The unit may be absent as the result of pre-Solling erosion. Owing to later erosion, it is now absent from most of the Late Kimmerian highs (see Fig. A.6 in Section A).
Age Scythian.
Depositional Setting During deposition of this subgroup fluvial influence repeatedly extended far into the basin, alternating with intermittent rises in water-level in the basin. Wind-blown deposits occur locally. Subtle unconformities at the base of the Volpriehausen and Detfurth Formations indicate the onsets of new sedimentary cycles, and possibly periods of minor tectonic uplift. No unconformity has been recognized at the base of the Hardegsen Formation. On the swells, the sedimentary sequences are condensed and reduced in thickness owing to erosion.
Subdivision The subgroup has been subdivided into three formations:
  RB Lower Germanic Trias Group
  RBM Main Buntsandstein Subgroup
  RBMH Hardegsen Formation
  RBMD Detfurth Formation
  RBMV Volpriehausen Formation
References See References Triassic

Van Adrichem Boogaert, H.A. & Kouwe, W.F.P., 1993-1997. [Stratigraphic unit]. In: Stratigraphic Nomenclature of the Netherlands.
Retrieved [Datum] from [url].