The geology of the coal-mining area of the Mons Basin, in which lies the village of Bernissart, animatronic dinosaur had been the subject of study before dinosaurs were ever discovered. A major review in 1870 pointed out that the coal-beaxing strata of the Mons Basin were pock-marked by ‘cran’ (naturally formed subterranean pits). Each ‘cran’ was of limited extent and filled with shales. It was concluded that these had formed by the dissolution of Palaeozoic rocks deep underground. The roofs of such caverns collapse periodically under the sheer weight of the overlying rocks, so the spaces become filled with whatever lies above: in this case soft clays or shales. Animatronic dinosaur for sale The collapse of such sediments had been recorded locally in the Mons area as rather alarming, earthquake-like shocks. By amazing coincidence, a minor ‘earthquake’ of this type took place while the dinosaurs were being excavated in August 1878 at Bernissart. Minor collapses in the galleries were noted, as well as flooding, but the miners and scientists were soon able to resume their work once the flood water had been pumped out.
Despite all the local geological knowledge, it is very curious that the scientists from the Museum in Brussels incorrectly interpreted the geological nature of the ‘cran’ at Bernissart. The mining engineers produced crude geological sections from the tunnels that yielded the dinosaurs. These showed that immediately beyond the coal-bearing seams there was a section of 10-11 metres of breccia (broken beds containing irregular blocks of limestone and coal mixed with silt and clay, the ‘collapsed coal-bearing rocks’ of Figure 18) before entering steeply dipping, but more regularly stratified, shales that yielded the fossils. Toward the middle of the ‘cran’ the clay beds were horizontally bedded, and as the tunnel approached the opposite side of the ‘cran’ the beds once again became steeply tilted in the opposite direction before passing again into a brecciated region and finally re-entering the coal-bearing deposits. The symmetry of the geology across the ‘cran’ is exactly what would be expected if overlying sediments had slumped into a large cavity.