Hospital Ground Formation DCDG

 

Premise Unit, defined by Van Adrichem Boogaert and Kouwe (1995).
Derivatio nominis Named after the Hospital Ground, a fishing ground in the vicinity of the type well.
Type section Location map See figure (pdf)
  Well E18-02 (pdf)
  Location N 54°09’05.1
E 03°46’40.7
  Depth 4058 to 4241 m
  Length 183 m along hole
Additional section Location map See figure (pdf)
  Well E13-01 (pdf)
  Location N 54°17’26.1
E 03°08’22.2
  Depth 3575 to 3773 m
  Length 198 m along hole
  Well K04-02 (pdf)
  Location N 53°44’56.3
E 03°03’01.3
  Depth 3633 to 3742 m
  Length 109 m along hole
Definition Alternation of sheet-like, amalgamated channel sandstones, red-bed mudstones, and a few thin, grey mudstone beds with rare coal seams. Sandstone intervals show thicknesses of 3 to 15 m, with an average of around 5 m. Sands are cream to pink, fine- to very coarse-grained, micaceous, locally conglomeratic, rounded to subangular, well- to poorly-sorted and well-cemented. Red-orange, white, and rarely variegated sandy mudstone intervals can reach up to 50 m in thickness.
Upper Boundary The Hospital Ground Formation is succeeded conformably by the Step Graben Formation. This boundary has been drawn above the uppermost massive sandstone which is succeeded by a mudstone interval of more than 60 m thick. In many wells (e.g. E13-01 (see pdf) ) the actual thickness of the uppermost mudstone interval cannot be determined as a result of truncation. Regional correlation of the uppermost sandstone level may provide a lead in this case, but it must be kept in mind that the bounding surface between the two formations is diachronous. In most wells the top of the formation is formed by the unconformable contact with the Upper Rotliegend Group. The precise boundary can be difficult to pick. Generally, a higher degree of lithification can be observed in the Carboniferous section. Moreover, Silesian sandstones tend to be more micaceous. In the northeastern offshore, the Hospital Ground Formation grades into grey, fine-grained, carbonaceous deposits, which belong to the upper part of the Maurits Formation (e.g. well G18-01, Annex C-19).
Lower Boundary The basal contact with the Maurits Formation has been placed at the base of the lowermost massive sandstone interval, overlying light-grey mudstones with frequent coal seams.
Correlation The Schooner Formation of Cameron (1993) combines the UK offshore equivalents of the Hospital Ground Formation and the Step Graben Formation. Comparable deposits from the adjoining UK off- and onshore were described sedimentologically by Besly (1988) and Besly (1993) .
Distribution Restricted to pre-Permian lows on the Cleaver Bank High, Silverpit Basin and adjoining areas.
Age Late Westphalian C - Early Westphalian D. For palynological markers of this interval, see Figure C.1 (see pdf) .
Depositional Setting Well- to poorly-drained fluvial fan to fluvial plain. Sandstones were deposited by small-scale braided fluvial channel systems and sheet floods. The fluvial systems formed sheets of stacked channel fills. The observed lateral thickness variations point to the existence of syndepositional tectonic activity. Actual marine bands have not been encountered, but some marine influence can be inferred Besly (1993) . The abundance of ferruginous soil profiles, absence of caliche soils, intercalated coal seams, oxidised plant remains and bioturbation indicate deposition under poorly-drained soil conditions, followed by very early diagenetic reddening Besly (1993) .
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].