Ruurlo Formation DCCR

 

Premise Unit, defined by Van Adrichem Boogaert and Kouwe (1995). This formation incorporates the larger part of the former coal-mining groups Wilhelmina (Upper Westphalian A) and Hendrik (Lower Westphalian B) of South Limburg. It comprises the middle part of the known Productive Measures of NAM (1980) .
Derivatio nominis Named after the village of Ruurlo in the province of Gelderland, where the type well is situated.
Type section Location map See figure (pdf)
  Well Ruurlo-1 (pdf)
  Location N 52°05’22.1
E 06°29’11.5
  Depth 814 to 1503 m
  Length 689 m along hole
Additional section Location map See figure (pdf)
  Well M11-01 (pdf)
  Location N 53°28’43.2
E 05°21’51.3
  Depth 3036 to 3524 m
  Length 488 m along hole
  Well P10-01 (pdf)
  Location N 52°27’48.3
E 03°08’55.8
  Depth 1960 to 2540 m
  Length 580 m along hole
  Well Goldhoorn-1 (pdf)
  Location N 53°11’46.6
E 07°04’30.7
  Depth 3199 to 37777 m
  Length 34578 m along hole
  Well Hardenberg-2 (pdf)
  Location N 52°00’26.0
E 06°34’20.9
  Depth 3175 to 3536 m
  Length 361 m along hole
  Well Lievelde-1 (pdf)
  Location N 52°00’26.0
E 06°34’20.9
  Depth 1091.5 to 1690 m
  Length 598.5 m along hole
  Well Steenwijkerwold-1 (pdf)
  Location N 52°48’12.6
E 06°01’48.0
  Depth 1915 to 2675 m
  Length 760 m along hole
  Well Woubrugge-1 (pdf)
  Location N 52°09’49.6
E 04°33’34.2
  Depth 3117 to 3722 m
  Length 605 m along hole
Definition Succession of dark-grey or black, silty mudstones containing a variable number of coal seams, and grey or buff, very fine- to fine-grained, fairly- to poorly-sorted, argillaceous or silty sandstone beds (up to 5 m thick). Sandstones are developed as minor channel fills and thin sheets of fair lateral continuity. The coal content (seams up to 2 m thick) demonstrates considerable lateral variations. The wire-line log patterns of the formation tend to be serrate (ratty), with gentle bell and funnel shapes, reflecting the stacking of fining- and coarsening-upward cycles and the continuous alternation of thin-bedded lithologies. The formation is characterised by a stacking of more or less symmetrical fining- and coarsening-upward sequences which show an average thickness of 50 m. In the unit a gradual upward shift from coarsening-upward- to fining-upward-dominated cycles can be observed, in four discrete stages. The formation lacks the diagnostic features of other formations: no clear predominance of funnel shapes (as in the Epen and Baarlo Fms.), or spiked sonic, resistivity, and density logs (as in the Maurits Formation). The Ruurlo Formation can be discriminated from the Klaverbank Formation and the formations of the Dinkel Subgroup by the lack of thick, massive sandstone intercalations.
Upper Boundary The top of the formation is marked by the abrupt transition into the coal-dominated claystones of the Maurits Formation.
Lower Boundary The unit rests conformably on the Baarlo Formation. At the transition the pattern of thick, stacked coarsening-upward sequences of the latter is succeeded by thinner fining- and coarsening-upward sequences. The boundary has been placed at the base of the sandstone truncating the uppermost thick coarsening-upward sequence. An overall shift is frequently observed in the wire-line logs, reflecting the more silty character of the Ruurlo Formation. An increase in coal-seam content can commonly be observed above this level. The Klaverbank Formation is a lateral equivalent in the northwestern offshore.
Correlation In the UK offshore adjoining the Dutch quadrants P and K, the Westoe Coal Formation is the equivalent of the Baarlo, Ruurlo and Maurits Fms. Adjoining Quadrants J and D the Caister Coal Formation corresponds with the Klaverbank Formation. The Westoe Coal Formation is equivalent to the Maurits Formation there (Cameron (1993) ). The basal interval of the Schooner Formation can be correlated with the youngest interval of the Maurits Formation.
Distribution Originally occurred over much of the Netherlands on- and offshore, but subsequently eroded over large areas (e.g. flank of the London-Brabant Massif, Krefeld-Maasbommel High, Texel-IJsselmeer High (see pdf) , Friesland Platform, Noord-Holland Platform, Zandvoort Ridge-IJmuiden High, Achterhoek High, Groningen High and Ringkøbing Fyn High; see Figures A.2 to A.7 in Section A, and Figure C.4 (see pdf) ).
Age Late Westphalian A - Early Westphalian B (Figure C.1 (see pdf) ). The formation is characterised by the first in situ occurrence (F.O.D.) of R. aligerens immediately below its base (Upper Westphalian A) and representatives of zone NJ (Clayton (1977) ) in the younger parts.
Depositional Setting Formed by a poorly-drained delta and fluvial-plain system, building out repeatedly into, and gradually filling up a lake basin. Clays and silts settled in the lake and in fluvial interchannel areas. Marine incursions (mainly brackish) are scarce. The interbedding of lacustrine fines and coals indicates fluctuations in lake level. Coarser-grained sediments scarcely reached the southern province. Only thin sandstone beds were deposited by fluvial channels and elongated lacustrine deltas, both of restricted lateral continuity. Four consecutive stages of regression can be recognised in this formation. In each stage, the contribution of deltaic deposition diminishes in favour of fluvial-plain sedimentation. The transition into the lake/swamp deposition of the Maurits Formation in the mid-Westphalian B indicates basin-wide flooding.
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].