Upper Rotliegend Group RO

 

Premise This unit was initially defined as a subgroup of the Rotliegend Group by van Adrichem Boogaert (1976) . NAM and RGD (1980) raised it to group level.
Derivatio nominis Name derived from the German stratigraphy where it is applied to the upper, non-volcanic part of the Rotliegend sequence.
Type section Location map See figure (pdf)
  Well Slochteren-4 (pdf)
  Location N 53°11’33.2
E 06°45’14.9
  Depth 2666 to 2856 m
  Length 190 m along hole
  Reference NAM and RGD (1980)
Additional section Location map See figure (pdf)
  Well Uithuizermeeden-1 (pdf)
  Location N 53°26’58.9
E 06°48’29.2
  Depth 2875 to 3167 m
  Length 292 m along hole
  Reference NAM and RGD, 1980
Definition Group of formations, comprising coarse- and fine-grained, clastic sediments, predominantly of red-bed type, as well as evaporites.
Upper Boundary The top of the Upper Rotliegend Group has been taken at the contact with the Zechstein Group. In general this contact is formed by the base of the Coppershale Member or Fringe Coppershale Member of the Z1 (Werra) Formation, reflecting the extremely rapid Zechstein transgression. However, in the southern onshore area the top of the Upper Rotliegend Group can be formed by a disconformable contact with younger Zechstein Group claystones and/or carbonates.
Lower Boundary The base of the group is formed by the unconformable contact (Saalian unconformity) with the Limburg Group (or locally the top of the volcanics of the Lower Rotliegend Group). The contact with the Limburg Group is generally characterized by a sudden shift in lithology, often combined with a downwards increase in compaction (due to pre-Saalian burial of the Carboniferous). Where thick sand bodies and red beds occur in the underlying Limburg Group, the boundary may be difficult to discern on wire-line logs. In cores, however, the difference in sedimentological character between Upper-Rotliegend and Limburg Group deposits is generally quite clear.
Distribution The main depocentre of the Upper Rotliegend in the Southern Permian Basin was located in northern Germany and the adjacent offshore area. A platform area between the London-Brabant Massif and the depocentre displays a moderately thick succession of sediments of the Upper Rotliegend Group. Subsidiary depocenters were: the Off Holland Low, the Ems Low and the Central Graben (see Fig. A.3 in Section A). Along the margins of the bordering massifs a thin veneer of Upper Rotliegend Group sediments is often preserved. In some areas the Upper Rotliegend has been removed by later uplift: from the Texel-IJsselmeer High (see pdf) , the Maasbommel High, the IJmuiden Ridge and from a few other small, unnamed structures (e.g. depicted in van Wijhe et al (1980) )
Age Saxonian. This age name is used in middle Europe for Permian continental deposits and is customarily placed in the later part of the Early Permian Odin and Odin (1990) . Recent magnetostratigraphic studies (Menning et al (1982) ; Menning (1994) ), however, indicate that this age can be largely equated with the early part of the Tatarian (Late Permian). New palynological evidence supports a Tatarian age Visscher and van Houte (1994) .
Depositional Setting On the basis of the widespread occurrence of aeolian and evaporitic sediments, in combination with their barren nature, these deposits are interpreted to have been formed in a desert-/playa-lake complex developed in a large intramontane basin. The alternation of salts and clays found in the centre of the basin is interpreted to have been caused by climatic variations (Trusheim, 1971; Hedemann et al., 1984). Only recently has the result of these climatic variations been tentatively recognised in the lithological columns of the basin fringe and transitional zones as well. Correlation between the basin and the transitional provinces remains a matter of debate (Gralla (1988) versus Gast (1991) ), but the depositional cycles are applied in the current German lithostratigraphy. George and Berry (1993) recently proposed using them in the Upper Rotliegend lithostratigraphy for the United Kingdom in the southern North Sea Basin as well. The depositional cycles were induced by climatic variations due to cyclic changes in the earth’s insolation (Milankovitch cycles, which also caused the Southern Hemisphere glaciations; Yang and Baumfalk (1994) ; Yang an Nio (1994) ; Yang et Kouwe (1997) . The three most prominent intercalations of the Silverpit Formation in the Slochteren Formation reflect longer periods of lake expansion. The tongues show marked thinning towards the south, as they grade into the Slochteren Formation. Regional log correlation suggests that lake expansion was a gradual, multiphase process, whereas subsequent progradations of the Slochteren Formation (perhaps tectonically related) into the basin occurred relatively rapidly.
Subdivision  
  The Upper Rotliegend Group has been subdivided into a sandy-conglomeratic formation deposited in the platform area, and a claystone-evaporite formation in the centre of the basin, hence:
  RO Upper Rotliegend Group
  ROSL Slochteren Formation
  ROCL Silverpit Formation
  In an E-W trending belt across the northernmost part of the Dutch onshore and adjacent offshore, sandy tongues of the Slochteren Formation and argillaceous tongues of the Silverpit Formation interfinger. The most prominent of these tongues have been given a member status (see Figs. D.1 and D.2). The lithostratigraphy of this transition zone basically can be composed of three different successions, in which recognition of members is based on lithology and stratigraphic superposition:
  succession a:
  ROCLT Ten Boer Member
  ROSLU Upper Slochteren Member
  ROCLA Ameland Member
  ROSLL Lower Slochteren Member
  succession b:
  ROCLT Ten Boer Member
  ROSLU Upper Slochteren Member
  ROCLA Ameland Member
  ROSLL Lower Slochteren Member
  ROCLH Hollum Member
  succession c:
  ROCLT Ten Boer Member
  ROSLU Upper Slochteren Member
  ROCLB* Buren Member
  The members with SL-codes are part of the sandy Slochteren Formation, whereas those with CL-codes belong to the argillaceous Silverpit Formation. Definitions of these members are presented in the detailed unit descriptions in the following paragraphs.
  Within each of the claystone members, the sand content shows a gradual increase towards the basin margin, and conversely the sandstone members demonstrate an increase in shale content in a basinward direction. Consequently, the lateral delimitation of these members is ambiguous. To reduce this ambiguity, NAM and RGD (1980) proposed to use the gamma ray log for distinguishing between coarse- and fine-grained clastics. For a unit to qualify as sandstone member, it is mandatory that it consists predominantly of sandstone (more than 50%), otherwise it is classified as claystone member. Evidence from adjacent wells (e.g. in a field or a cluster) may justify a slight variation from this definition (although an informal correlation should then be preferred). Furthermore, it is recommended that an interval under consideration should have a minimum thickness of approximately 15 m.
  As a consequence of the locally heterogeneous lithologies of the lithostratigraphic units of the Rotliegend, the lithological affixes of the formation names and most member names have been abandoned here, in line with the recommendation of Hedberg (1976) .
References See References Permian

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