Abstract
The Romilly region, situated at the junction of two major geological features of the Paris Basin, exhibits numerous Quaternary deformations. The origin of these deformations has been the subject of conflicting publications: seismites versus periglacial. The existence in Gélannes of an anthropogenic pit dating from the Late Bronze Age, affected by a fault approximately 0.35 m high, has reignited the debate. Thus, periglacial deformations may have been reactivated by a Holocene earthquake, thereby explaining, amongst other things, the flame-like structures and faults. This is all the more likely given that Holocene faults are found at Sauvage, as are late-stage injections of chalk mud reaching the surface. The intersection of the Saint Martin and Sézanne faults could be the cause of the observed deformations. Petroleum seismic surveys thus show that, locally, the Saint Martin fault extends up to the top of the chalk. The epicentre is likely to be found near the most deformed sites at Marcilly and Sauvage. This seismic hypothesis also corroborates the conclusions of Damon et al. (2023). This author suggests a potential current slip on the Vittel and Saint Martin faults, as a result of the melting of the Scandinavian glaciers. It is also interesting to note a higher local geothermal flux at Saint Just Sauvage (98 mW/m² compared with 86 mW/m² in the Paris Basin), likely linked to heterogeneities at the base of the crust. This author suggests that the Vittel and Saint Martin faults may currently be active again, as a result of the melting of the Scandinavian glaciers. It is also interesting to note a higher geothermal flux locally at Saint Just Sauvage (98 mW/m² compared with 86 mW/m² in the Paris Basin), which is likely linked to heterogeneities at the base of the crust. This type of thermal anomaly is sometimes put forward as an explanation for intraplate earthquakes.