Baarlo Formation DCCB


Premise Unit, defined by Van Adrichem Boogaert and Kouwe (1995).
  This formation combines parts of the former coal-mining groups Ubachsberg (Namurian C), Baarlo (Lower Westphalian A) and Wilhelmina (Upper Westphalian A) of South Limburg (regional correlation (see pdf) ). It is equivalent to the lower part of the Productive Measures of NAM (1980) . The lower part of the Westoe Coal Formation in the southern offshore is the UK equivalent (Cameron (1993) ).
Derivatio nominis Named after the village of Baarlo in the south of the province of Limburg. The name corresponds to a former coal-mining unit (Jongmans (1928) ; Jongmans (1940) ; Pannekoek (1965) ), representing the Lower Westphalian A. This interval constitutes the bulk of this unit.
Type section Location map See figure (pdf)
  Well Rijsbergen-1 (pdf)
  Location N 51°31’44.3
E 04°41’21.6
  Depth 2134 to 2927 m
  Length 793 m along hole
Additional section Location map See figure (pdf)
  Well Goldhoorn-1 (pdf)
  Location N 53°11’46.6
E 07°04’30.7
  Depth 3777 to 4500 m
  Length 723 m along hole
  Well Steenwijkerwold-1 (pdf)
  Location N 52°48’12.6
E 06°01’48.0
  Depth 2675 to 3216 m
  Length 541 m along hole
Definition Succession of dark-grey, brownish-grey or black mudstones, grading into grey or buff siltstones and very fine-grained sandstones. The formation consists of a large number of stacked coarsening-upward cycles of 20 to 300 metre thick, with a coarsening-upward overall trend. The mudstone intervals in the base of some cycles contain open-marine or brackish-water fossils (goniatites, Lingula). Fine- to medium-grained, (sub-)angular, moderately- to well-sorted sandstones are restricted to the tops of some of the cycles. Although the cycles may be well-correlatable, individual sandstone bodies show a restricted lateral continuity. In the Peel area and Gelderland certain sandstone intervals consist of coarse-grained sand and conglomerates. In those sequences, the stacked funnel-shaped log patterns can be obscured. Usually, less than four coal seams occur per 100 m of section. They are typically restricted to the uppermost parts of depositional cycles. Seams can be up to 2 m thick, but generally fall in the dm-range.
Upper Boundary The transition into the overlying Ruurlo Formation is marked by the transition of thick coarsening-upward sequences into thinner, combined fining- and coarsening-upward cycles. The boundary has been placed at the base of the sandstone or sandy siltstone bed which truncates the top of the uppermost thick coarsening-upward sequence. It coincides with a shift in log patterns (GR, sonic, resistivity, etc.) to combined bell-funnel-shaped patterns. The oldest interval of the Klaverbank Formation in the northwestern Netherlands offshore is a sandstone-dominated lateral equivalent (generally more than 30% sand).
Lower Boundary The basal contact of the formation with the Geul Subgroup (Epen Formation) has been placed at the base of the lowermost coal seam.
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 Present over large parts of the Netherlands on- and offshore territory, except for the northern flank of the London-Brabant Massif. Around the northwestern offshore the formation grades into the Klaverbank Formation.
Age Depending on the geographic position in the basin, peat deposition started in the Namurian B, C, or the Early Westphalian A. In the southeast and east of the Netherlands and adjoining Germany, the base of the formation has a Namurian age (e.g.Hedemann (1973) ;Hedemann (1984) ; Drozdzewski (1985) ; Wrede (1988) ; Strack (1989) ; Drozdzewski (1992) ). In the central onshore the first coal seam can be found up to 150 m above the base Westphalian A.In most wells the top of the formation more or less coincides with the first occurrence (F.O.D.) of Radiizonates aligerens, a typical Upper Westphalian A palynomorph.
Depositional Setting Each coarsening-upward cycle started with a brief, but extensive marine incursion, followed by a period of delta progradation. In the course of the Westphalian A, the overall regression reduced the deltaic realm to the basin centre. It was succeeded by coastal- and fluvial-plain deposition. The sandstone bodies in the Namurian and Lower Westphalian A cycles have been interpreted as delta-front deposits. The massive sandstone bodies are laterally discontinuous (Drozdzewski (1992) ), suggesting moderate channel shifting. Pebbly and gravelly intercalations reflect pulses of higher bed-load discharge. Coal seams developed in delta-plain swamps. Clays, silts and very fine-grained sands were deposited in the distal part of the basin, and on the delta plain as overbank sediments. Collinson (1988) and Jankowski (1993) compare this delta type with the bird-foot morphology of the present-day Mississippi delta, characterised by a large suspended sediment load (Orton (1993) . The finer-grained, distal character of the unit, compared to the Klaverbank Formation, indicates a predominant northern sediment source. However, the intercalation of coarse-grained sandstones and conglomerates in Limburg and Gelderland (Achterhoek) indicates that sediment was also supplied by a southeastern source (Rhenish Massif).
References See References Upper Carboniferous

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