Growth and diagenetic history of aragonite-calcite speleothems, implications for environmental studies
Résumé
Speleothem formation is linked in a number of ways to a set of environmental parameters interfering from micro-to regional, or even global scales. Variation of such parameters with time occurs with two fundamental implications: 1) speleothem material potentially represents excellent archives for fine-scale reconstruction of past environments and climates, 2) physical and chemical modifications of the microenvironment may induce diagenetic transformation of the existing speleothems, which hence are in a nearly continuous evolution. The purpose of this work is to identify the different processes involved in the formation and the the post-depositional evolution of speleothems from the Pont-de-Ratz Cave (Hérault, S. France) and to provide reliable criteria for the distinction of primary and diagenetic features. The main objective is to discriminate products and processes involved in the development of speleothem ("spelean growth history") and those involved in the transformation of a pre-existing speleothem structure ("spelean diagenetic history"). These results highlight the diversity of potential diagenetic modifications of both initial aragonite and calcite precipitates, together with the strong interest of using coupled petrography and geochemistry for precisely deciphering the nature and origin of the different spelean products, thereby providing a reliable tool for chronological reconstruction of events interfering in connection with speleothem development.