An example of sedimentary filling in the chalk karst of the Western Paris Basin: Characterization, origins and hydrosedimentary behaviour

摘要

The Petites Dales cave is a favourable site for studying the sedimentary fillings of the chalk karst of the Western Paris Basin. Our study is based on the lithological characterization of karstic sediments and mineralogical and chemical comparisons between these sediments and the likely sedimentary sources (insoluble residue of chalk, clay-with-flints, loess). Our results show that there are three main families of sediment in the Petites Dales karst: brown clayey silts, beige silts, pale beige silts. The karst sediments essentially originate in the mechanical erosion of loess. The insoluble residue of chalk, coming from the chalk weathering, is only located in the brown clayey silts, and constitutes a weak amount of this sediment type. According to these results, we propose three conceptual models of hydrosedimentary behaviour of the Petites Dales karstic system that could have resulted in such an intra-karstic deposition sequence.