| mhorn | Дата: Friday, 18.11.2011, 15:34 | Сообщение # 1 |
Admin
Group: Администраторы
Posts: 1060
Reputation: 0
Status: Offline
| Ivanov M., Stoykova K., Idakieva V. (2010) New biostratigraphic data on the Upper Tithonian and Lower Berriasian in the Krayshte area (Southwestern Bulgaria) // Annuaire de l’Universite de Sofia “St. Kliment Ohridski”, faculte de geologie et geographie. Livre 1 – Geologie. Tome 102. P.21-42. [in Bulgarian]
pdf: http://cretaceous.ru/files/pub/ivanovetal_2010_jk_bnd_bulgaria.pdf
The Lower Cretaceous Series in Krayshte area (SW Bulgaria) is represented by siliciclastic sediments, referred to the Kostel Formation. The latter consists of two members: Bobovo Mb and Gorochevtsi Mb. The Lower Cretaceous rocks are building up the upper part of the Gorochevtsi Mb only. The present study covers the Upper Tithonian — Lower Berriasian interval of the Gorochevtsi Mb in the section cropping out between Polyana hamlet (ex-Tyutyundzhiiska) of Kosacha village and Kopanitsa, Pernik District (SW Bulgaria). The biostratigraphic interpretations are based on ammonite and calcareous nannofossils finds. The recorded ammonite fauna indicates or proves the occurrence of several ammonite zones. In the Upper Tithonian, Micracanthoceras microcantum Zone (with Paraulacosphinctes transitorius Subzone in its upper part) is indicated and Durangites Zone is distinguished (with Durangites singularis, Durangites cf. vulgaris, Durangites aff. astillerensis, Protacanthodiscus cf. andreaei, Protacanthodiscus sp.). In the basal Berriasian, Berriasella jacobi Zone is evidenced (comprising Berriasella jacobi, Subapinites aff. aristidis, Delphinella janus, Fauriella shipkovensis, Berriasella sp.). The Durangites Zone is detected for the first time in Bulgaria, which provokes a necessary revision of the ammonite criteria for drawing Jurassic-Cretaceous boundary in Bulgaria. The problem is pending long ago in Bulgarian stratigraphic practice, especially after the results of detailed micropaleontological studies across the J-K boundary interval (Lakova et al., 1997; 1999). Here we suggest in Bulgaria to draw this boundary at the top of Durangites Zone and at the base of Berriasella Jacobi Zone. In this way, it will match the worldwide accepted agreement/criteria and will tie up to the position already recognized by microfauna and nannoflora (Lakova, 1993; Lakova et al., 1997; 1999).
Middle Jurassic - Lower Cretaceous ammonites & aptychi
|
| |
| |
