|Depositional environment, paleoecology and diagenetic history of the 'Marbre rouge à Crinoides de Baelen' (Late Upper Devonian, Verviers Synclinorium, eastern Belgium|
Dreesen, R.; Bless, M.J.M.; Conil, R.; Flajs, G.; Laschet, C. (1985). Depositional environment, paleoecology and diagenetic history of the 'Marbre rouge à Crinoides de Baelen' (Late Upper Devonian, Verviers Synclinorium, eastern Belgium. Ann. Soc. géol. Belg. (1968) 108: 311-359
In: Annales de la Société Géologique de Belgique (1968). Vaillant-Carmanne: Liège. ISSN 0037-9395, more
|Authors|| || Top |
- Dreesen, R.
- Bless, M.J.M.
- Conil, R.
The "Marbre rouge à Crinoïdes de Baelen" is the only Famennian reef-analogous structure known thus far in the Ardenno-Rhenish Massif. Its location within the Verviers Synclinorium is linked to the presence of deep-seated transversal faults. During a short-term transgressive pulse and a decrease of siliclastic detrital influx, carbonates were deposited on offshore, submarine structural highs. Initially, crinoids, dasyclads and sponges lowered the current velocity and trapped the lime mud. Subsequently, cyanobacteria and algae produced lime mud and/or fixed skeletal grains in place. Subsidence was important but discontinuous, so that the carbonate buildup has intermittently reached the wave base during its growth. These oscillations are reflected by the irregular but frequent interstratification of crinoidal packstones and grainstones within the mudstones. The latter include cryptalgal, algal and spiculitic mudstones, grading locally into algal bindstones and floatstones. Early-diagenetic (synsedimentary) spar-cementing of the cavities consolidated the calcareous lime buildup. Paleoecological evidence points to a quiet and/or relatively deep shelf environment for the mudstones (siliceous sponges, silicified ostracode assemblages) whereas the abundance of Issinellids would still indicate the (upper ?) photic zone. The micropaleontological content of the crinoidal pack/grainstones rather suggests more shallow subtidal conditions (broken plurilocular foraminifers, girvanellid oncoids, vermetid gastropods). The observed diagenetic processes reveal subsequent influences of marine (fibroradiaxial calcite), mixed marine-meteoric (silicifications, dolomitization) and meteoric (syntaxial rim cements, solution coronas, dedolomitization) phreatic waters, indicating a gradual uplift and possible emersion of the Baelen buildups after their deposition. A strong pressure solution produced conspicuous iden-supported stylolaminitic or stylonodular fabrics within the impurer limestones facies. Thus the Baelen limestone complex is a stratigraphic reef, located on a predestinated mounding site in an open marine shelf setting near wave base, displaying characteristics of both a mud mound and a spar-cemented debris reef. Baculella gemina n. gen. n. sp. Conil & Dreesen (Microproblematicum) and Processobairdia dreeseni n. sp. Bless (Ostracoda) are described as new.