Interaction between eustacy and block-faulting in the Carboniferous of the Vise - Maastricht area (Belgium, The Netherlands)

The Vise-Maastricht sedimentation area (VSA) is situated at the eastern end of the Brabant Massif and suffered block-faulting tectonics during Lower Carboniferous time. The south edge of the VSA, the area corresponding now to the vicinity of Vise, comprised three main tectonic blocks: the Hermalle-sous-Argenteau, Souvre and Bombaye blocks. They were bounded to south by the Booze-Val-Dieu block. To the north, in the vicinity of Maastricht, blocks are not well differentiated and are referred to as the Maastricht block system. From the end of the Tournaisian, the latter evolved into a rapidly subsiding graben, recording mainly debris flows and limestone turbidites, whereas the southern blocks remained relatively high. Through much of Lower Carboniferous time, they were emergent, but during high eustatic sea levels, they were flooded and covered by limestone deposits. The differences in the nature and the age of the deposits between blocks result from the interaction between block-faulting and eustacy. In the VSA, the Upper Devonian and Lower Tournaisian (Hastarian) deposits are similar to those known in the north part of the Namur-Dinant Basin. But from the late Tournaisian (Ivorian), the uplift of the Booze-Val-Dieu block prevented all connections with the Namur-Dinant Basin and the VSA became linked with the Campine Basin. The Souvre block subsided from the latest Givetian to the late Frasnian and recorded a thick middle Frasnian limestone series, but was later emergent, so much that karstic cavities developed. The Souvre block was submerged for a short time at the top of the Tournaisian, during the very high highstand (HST) corresponding to eustatic sequence 4, and the caves filled up with sediments. The Hermalle-sous-Argenteau and the Bombaye blocks, situated respectively west and east of the Souvre block, evolved in the same way during the late Devonian. They subsided slightly from the earliest Tournaisian to the late Visean (Warnantian), but usually remained emergent and recorded deposits only during times of high eustatic levels corresponding to the early Tournaisian (for the Bombaye block), the end of the Tournaisian (HST of sequence 4), the end of the early Visean (HST of sequence 6), then the late Visean (HST of sequences 9 and 10). In its southern part, the Hermalle-sous-Argenteau block recorded also lowermost Visean limestones correlated with the highstand of the eustatic sequence 5, probably as a result of the tilting of the block to the south at this time.