Jean-Paul Saint Martin

Late Miocene events in the Mediterranean as recorded by carbonate-evaporice relations

The Messinian Stage in the Mediterranean region is known mainly because of a major evaporitic event whose causes and global implications are still under discussion. Correlations between basinal evaporite-bearing series and marginal carbonate platforms allow for improvement of the classical depostional models, especially concerning the eustatic control of the environmental changes in the Mediterranean. These changes were controlled by the interplay of aperiodic and periodic factors: (1) tectonics, related to the relative motions of the African and Eurasian plates and resultant linear increase in the basin restriction; (2) sea-level fluctuations that alternately aggravated the restriction or allowed marine replenishment, and (3) climatic fluctuations that controlled the level of the Mediterranean during stages of isolation. The Messinian sedimentary succession reflects a typical sequence of progressive isolation: marine marls {yields} laminites {yields} transitional deposits {yields} evaporites {yields} lacustrine deposits. The first stage of the so-called salinity crisis was characterized by a Mediterranean lowstand that resulted in erosion of former platforms and deposition of the lower evaporites. During the next stage, sea level rose (TB3.3 cycle) high enough to temporarily replenish the basin (cyclic upper evaporites, with development of stromatolite-rich deposits). Finally, the uppermost Messinian freshwater to brackish lacustrine deposits reflect both themorexa0» cessation of sea-water input (maximum tectonic isolation, low sea level) and freshwater input related to increasing runoff.«xa0less

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.

New eryonid crustaceans from the Late Jurassic Lagerstätten of Cerin (France), Canjuers (France), Wattendorf (Germany) and Zandt (Germany)

The Late Jurassic plattenkalks from Europe are remarkable for their exquisitely preserved crustaceans. New specimens of polychelidan lobsters (Crustacea, Decapoda, Polychelida) from the Lagerstätten of Cerin (France), Canjuers (France), Wattendorf (Germany) and Zandt (Germany) are described and increase the palaeobiodiversity of Jurassic eryonids. Soleryon gen. nov. is described from the Cerin, Wattendorf and Zandt Lagerstätten while Cycleryon bourseaui sp. nov. is described from the Cerin and Canjuers Lagerstätten. Soleryon amicalis gen. et sp. nov. from Cerin and S. schorri sp. nov. from Wattendorf show cephalothoracic grooves that are not observed within any other fossil eryonids. Their patterns of cephalothoracic grooves are similar to those observed in extant polychelids and confirm the affinities of eryonids and polychelids. The problematic assignment of Eryon perroni Étallon, 1859 from the Oxfordian nodules of eastern France is solved and leads to the new combination Soleryon perroni (Étallon, 1859). These new eryonids are preserved in anatomical connection and thus suggest they used to live in proximity to their depositional environments. They may have inhabited the coral reefs neighbouring the lagoons and/or buried themselves in the carbonate mud of the lagoon margins at the origin of the plattenkalks. The co-occurrences of Soleryon gen. nov. and Cycleryon Glaessner, 1965 in four subcontemporaneous Lagerstätten clearly suggest connections between the Bavarian (Wattendorf, Zandt), the Jura (Cerin) and the Provence (Canjuers) platforms. For the first time, several species of crustaceans highlight and confirm the palaeobiogeographical links between the French and German plattenkalks at the end of the Jurassic. http://zoobank.org/urn:lsid:zoobank.org:pub:76AD86C3-C677-49EA-B742-0ACA6EB90F72