Plant inclusions from the Cenomanian flints of Archingeay, Les Nouillers, western France
Abstract
Here, we report flint nodules bearing fossil plant inclusions from the early Cenoma- nian of the Font-de-Benon sand quarry, between the villages of Archingeay and Les Nouillers, Charente-Maritime, western France. The broken-open surfaces of these dense siliceous rocks only partly show the whole diversity, which is established using a non-destructive, multi-scale approach based on propagation phase-contrast X-ray synchrotron microtomography. The conifer genera Brachyphyllum, Frenelopsis, Gein- itzia, and Glenrosa have three-dimensional preservation, and vegetative and reproduc- tive organs are in connection in some cases. The flint nodules formed by silicification of Cenomanian sediments, probably as a result of an intensive period of soil alteration and leaching under warm and wet climate during the Eocene. Although the time was long between the Cenomanian sedimentation and the Eocene silicification, the fossil plants show three-dimensional external morphology. These mineralizations are inter- preted as fine silica microcrystallization over the cell walls and thus are examples of late silica permineralization. The association of foraminifers, echinoids, sponge spicules, and conifers suggests that the Cenomanian sediments were deposited in a coastal and open to the sea palaeoenvironment, near a conifer-dominated mangrove.