The information on this page is a summary description.
The full formal description is available here: Kunrade Formation
| Abbreviation | |
| Parent unit | Chalk group |
| Child unit | |
| Lithological description | The Kunrade limestone consists of an alternation between compact and soft limestone beds, of unequal distribution through the formation. In the outcrop area the hard beds are affected by randomly oriented vertical cleavage planes. Their thickness reaches 75 cm. The hard beds are strongly cemented. Hard beds are used as building stone (Kunrader stone), debris of hard beds and soft layers are used in limestone kilns. Lithological description in the parastratotype section in borehole KS22: 362-374 m: Alternation between yellowish-white compact and porous mostly fine-grained calcarenite. Irregular black laminae, composed of organic-rich Uranium-bearing clay. The calcarenite shows many bioturbations (cylindrical decapod burrowings 1-3 cm wide and possibly decimeters long, with 1-2 mm thick white marly wall). Bioclasts are sorted according to grain-size variations; larger molluscs (pectinidae) were observed. Glauconite is rare. 374-383 m: Grey mostly fine-grained bioturbated calcarenite, with centimetric to decimetric coarser grained layers; alternation of poorly consolidated and more lithified bands; rare dark brown clayey laminae (origin for discrete silicifations) and lithified nodules; moldic porosity (mostly dissolved mollusc shells). At 381 m fossiliferous horizon rich in serpulids, echinoderms and molluscs. This interval most closely resembles the typical Maastrichtian “tufkrijt/tuffeau” calcarenite in the Kunrade facies. 383-393 m: Yellow fine-grained porous calcarenites with dark laminae, alternating with lithified bands affected by joints and incipient stylolites. Silicification becomes more apparent in the form of grey-coloured silicified bands and dark-grey to black flints. Admixture of grey marly laminated calcilutite. The compact bands are strongly bioturbated, displaying abundant burrowings filled with loose calcarenites and moldic porosity. The crumbly, porous calcarenites disappear at the base of this unit. 393-398 m: Transition zone to chalk facies, with similar lithologies, except for yellow porous calcarenites, as the overlying interval. 398-411 m: Light-grey calcilutite to chalk with dark laminae; frequent lithified and partly silicified bands with thickness 10 to 35 cm. |
| Age | Total range of the Kunrade Formation includes a major part of the Lanaye Member equivalent of the Gulpen Formation in the type area, and the lower part of the Maastricht Formation, up to the Emael Member (Felder & Bosch, 2005, p. 73). In the eastern Campine basin, the upper part of the Maastricht Formation (Nekum and Meerssen Members) is lacking, the remaining parts (equivalent to Emael to Valkenburg Members which cannot be distinguished as individual members) being expressed under the form of the Kunrade facies. The long-lasting hiatus at the end-Cretaceous is confirmed by the absence of the bioclast zonation: ecozones Vc-d, corresponding to the Nekum-Meerssen Members of the Upper Maastricht Formation in the Maastricht type area (Felder, 1994). The core of the Kunrade beds is probably developed in beds assigned to the Gronsveld member of the Maastricht Formation in the Maastricht type area. |
| Thickness | ca 50 m. |
| Area of occurrence | The Kunrade Formation spans the same area as the underlying Dorne Formation in the eastern Campine mining district and is laterally grading into the Gulpen Formation in the western Campine mining district. The Kunrade Formation is also present in the Belgian part of the Roer Valley Graben. The formation continues into Dutch South Limburg, where the type locality is located. Interfingering with the Maastricht Formation and Lanaye Member of the Gulpen Formation complicates the mapping of the Kunrade Formation. |
| Type locality | Stratotype: limestone quarry Kunderberg at Kunrade, commune of Voerendaal (NL South Limburg). Dutch geological survey outcrop 62B-9 and coordinates 195450 – 320.210. Other quarries in the Dutch type area include the Schaelsberg section atSchin-op-Geul (Dutch geological archive 62A-236) and the geological monuments Midweg in Voerendaal (62B-79) (Felder & Bosch, 2005). Parastratotype: borehole KS22 (63E222, X 238822, Y 191259, Z 91 m), depth range 362-411 m. |
| Alternative names | |
| Authors | Dusar, M. & Lagrou, D. |
| Date | 01/01/2012 |
| Cite as | Dusar, M. & Lagrou, D., 2012. The Kunrade Formation, 01/01/2012. National Commission for Stratigraphy Belgium. http://ncs.naturalsciences.be/lithostratigraphy/Kunrade-Formation |
