Search the Community
Showing results for tags 'stratotype'.
-
Dear members, the present post of mine deals with my visit to the Barremian Stratotype. I'd like to point out, however, that no fossil collecting was involved, since that was a protected area. The Barremian (129.4 - 150 Myr) is the fourth stage of the Lower Cretaceous. The base is marked by the lowest occurrence of the Taveraidiscus hugii and the Avramidiscus vandeckii ammonite groups. A stratotype (or type section) is defined as "the specific stratal sequence used for the definition and/or characterization of the stratigraphic unit or boundary being defined." Almost all the geochronological stages have a stratotype. If these sections meet a number of criteria, they are assigned as GSSPs, informally known as Golden Spikes (see https://stratigraphy.org/gssps/). The Barremian Stratotype does not have a GSSP yet (a candidate is in Spain), but does have a stratotype. Originally located near the town of Barrême (whence the name), it was later redefined using a roadside exposure near Angles, a small town in the Alpes-de-Haute-Provence department, southeastern France. I pinpointed the location with a red arrow: By the way, in the city centre of Barrême you can see sculptures of heteromorph ammonites made with fiberglass: The section of Angles consists of 232 beds, that encompasse the latest Hauterivian, the whole Barremian and the earliest Aptian. Decimeter-thick calcareous beds alternate with thin dark coloured marls, rich in ammonites and belemnites. Eight ammonite biozones have been established for the Barremian section (see http://laboratoire.gpa.free.fr/Dossiers/Ammonites/Cretace/Barremien/stratotype.html). Here you can see a panoramic view of the outcrop, even though it's not the whole exposure: Here I'm posing so that you can have an idea of the unit's thickness: Each bed's number has been marked with green spray paint. Bed 72 represents the base of the Barremian: Walking alongside the section I noted a few specimens that I pictured, but eventually I didn't collect them. Above bed 80 I saw this tiny ammonite (diameter 2,5 cm or 1 in): Above bed 28 I saw this "flat" fossil, that might be a belemnite rostrum, but I'm not sure of that. I sincerely hope that you enjoyed my brief account. Thank you!
- 4 replies
-
- 10
-
- france
- cretaceous
-
(and 1 more)
Tagged with: