Simona Saint Martin

Exceptional preservation of marine diatoms in upper Albian amber

Late Albian amber from Charente-Maritime (southwestern France) contains the first known marine diatoms preserved in a fossil resin. Approximately 70 inclusions were assignable to the genera Basilicostephanus, Coscinodiscus, Hemiaulus, Melosira, Paralia, Skeletonema, Stephanopyxis, Trochosira, ?Aulacoseira, and to the order Rhizosoleniales. Some of them are represented by several species. This diatom assemblage is mainly composed of colonial planktonic genera, which are typical for coastal shallow waters. The newly found amber inclusions extend the fossil record of four genera and one order from the Late Cretaceous and support certain molecular phylogenetic assumptions regarding the diversifi cation of marine diatoms in the Early Cretaceous. The unusual introduction of diatom shells from the beach or sea by wind, spray, or high tide onto the resin fl ows was possible because the amber forest grew close to the seashore.

CALCAREOUS MICROBIALITES AND ASSOCIATED BIOTA IN THE MEDITERRANEAN COASTAL LAGOONS AND PONDS OF SOUTHERN FRANCE: A KEY FOR ANCIENT BIOCONSTRUCTIONS?

Microbialites were found in various lagoons of the Mediterranean coast of southern France. They preferentially develop on pebbles on the edge of semi-enclosed water bodies, which can be temporarily dewatered and desiccated. The microbialitic building is achieved episodically with variations in the characteristics of the different layers. Its cerebroid and pustular appearance is the most remarkable macroscopic feature. Occasionally, other organisms may be involved in the construction, such as bryozoans and serpulid worms that form also in other places small unconsolidated bioconstructions. The analogy of these phenomena with bryozoans-serpulid-microbialite reefs occurring during Miocene in Paratethys, like those noticed in Romania, proposed by some authors, is considered unlikely, despite some common features.