|mhorn||Дата: Saturday, 04.05.2013, 18:10 | Сообщение # 1|
|Gallois R.W. (2012) A revised description of the lithostratigraphy of the Kimmeridgian-Tithonian and Kimmeridgian-Volgian boundary beds at Kimmeridge, Dorset, UK: reply to Wimbledon 2012 // Geoscience in South-West England. Vol.13. P.132-134. |
Gallois here replied to the critical notes by Wimbledon. Important information is provided concerning the Bolonian Stage. Gallois is writing: “Cope’s (1993) definition of the base of a revised Bolonian Stage was not taken at a faunal, geochemical or magnetostratigraphical event that would serve as a proxy for a timeplane. It was taken at the base of Blake’s (1875) Bed 42, an 0.3 m-thick laterally impersistent, secondarily cemented mudstone that is known from only one outcrop, at Hen Cliff…. This bed has no… value for correlation purposes. The same definition was used by Cope (1967) to define the base of the Pectinatites (Virgatospinctoides) elegans Zone, a biozone defined by an arbitrary lithological level 20 m below the lowest undoubted Pectinatites…. Crushed, incomplete specimens of virgatosphinctids [dorsoplanitids] down to and below Blake’s Bed 42 that do not preserve the distinctive horn on microconch forms could equally well belong to other genera”. Gallois also argued that the described succession is most complete than other yet described (fig. 1), but the figure containing some uncertainities: gap in the succession of Gorodischi cannot be recognized biostratigraphically and defined only by presence of phosphorites belonging to few generations at the lowermost efimovi horizons; correlation of this discontinuity with interval near to Bed 42 cannot be proved by faunal evidences, as common elements are missing in compared successions (real Gravesia records in the Russian Platform still not recognized). There are no evidences also for such a gap in the Swabian succession.
Middle Jurassic - Lower Cretaceous ammonites & aptychi