Hunze Subgroup DCH

 

Premise Unit, defined by Van Adrichem Boogaert and Kouwe (1995).The name Hunze Subgroup replaces the former Barren Measures (DCCR) of NAM (1980) . Prior to 1980, that term was applied to all Silesian red-bed deposits, irrespective of the primary or secondary nature of reddening, or the sand/shale ratio. NAM and RGD (1980) restricted the use to predominantly fine-grained, primary red beds with some sheet sandstones in the eastern Netherlands onshore, overlying the Tubbergen Sandstone Formation.
  Continued use of the name Barren Measures could lead to controversial interpretations, and is therefore not recommended. The new Hunze Subgroup is restricted to largely fine-grained deposits with a predominant, but not unique red-bed character.
Derivatio nominis Named after the Hunze river, which runs through the province of Drenthe, where deposits of this subgroup are common in the subsurface.
Type section Location map See figure (pdf)
  Well De Lutte-6 (pdf)
  Location N 52°19’49.7
E 07°00’50.8
  Depth 2232 to 2987 m
  Length 755 m along hole
Definition Succession of largely orange- or brownish-red, but also grey or variegated mudstones with some intercalated sandstone beds, mostly without coal seams.
Correlation The upper Ketch Member of the Schooner Formation and the Brig Formation of Cameron (1993) are partial lithostratigraphic counterparts in the UK offshore.
Distribution The De Lutte Formation is probably restricted to the Ems Low (see Figure A.2, section A) and its western margin. The Step Graben Formation is found in the northern and western offshore. The Strijen Formation is restricted to the Campine Basin.
Age Latest Westphalian C to Westphalian D and possibly Stephanian. Deposition of this subgroup may have continued into the Stephanian. Some samples from Westphalian D intervals show an arid hinterland overprint. These assemblages resemble ‘Stephanian/Autunian’ microfloras, characterised by Cordaitina spp., Illinites spp., Striatodiplopinites sp., Lundbladispora gigantea, Potonieisporites spp. and Cadiospora magna (Figure C.1 (see pdf) ). In-situ palynological assemblages and macroscopic plant remains yield consistent Westphalian D ages (Torispora spp., Thymospora spp., Laevigatosporites spp.: van der Zwan (1991) ). The intercalation of ‘Westphalian D’ and ‘Stephanian/Autunian’ microfloras points to simultaneous existence of humid and arid floral provinces. Palaeobotanical data tend to result in more accurate age datings (van Amerom (1994) , in prep.). Palynology may yield too young age datings, which has recently cast some doubt on some German Stephanian datings. The palaeobotanical biozonation of the Dutch Westphalian D, as defined in well De Lutte-6 (see pdf) , is presented in Figure C.2 (see pdf) . The existence of Stephanian in the eastern Netherlands (Ems Low) has never been confirmed palaeontologically, but has frequently been assumed on lithological grounds and from log correlations with Germany where the occurrence of deposits of this age has been confirmed (Josten (1997) ; Hedemann (1984) ;Teichm├╝ller et al (1984) (map);Selter (1990) ; Tantow (1993) ; van der Meer (1994) , in prep.).
Depositional Setting Characterised by distal flood-plain deposition. Intercalated sand sheets were formed by sheet floods and small-scale fluvial channels. Most of the succession consists of a well-drained, primary red-bed facies, but less well-drained, grey, carbonaceous facies also occur. The tropical humid climate of the Westphalian C gradually changed to a (semi-)arid climate during the Stephanian (van der Zwan (1993) ;van de Laar (1994) , in prep.). Carbonaceous matter, very rare coal seams, ferruginous soil profiles, (oxidised) plant remains and bioturbation in the Upper Westphalian C and Lower Westphalian D reflect periods of poor soil drainage. The predominantly calcic soils in the Westphalian D indicate increased aridity (Besly (1993) ; Besly (1988) ; van der Zwan et al (1993) ). ‘-Primary’ reddening was caused by very early-diagenetic water-table fluctuations (Besly (1993) ).
Subdivision The Hunze Subgroup comprises three formations, representing the relatively fine-grained upper Westphalian in various parts of the Dutch Northwest European Basin.
  DC. Limburg Group
  DCH Hunze Subgroup
  DCHS Strijen Formation
  DCHL De Lutte Formation
  DCHP Step Graben Formation
References See References Upper Carboniferous

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