Late Turonian and Coniacian according to study of palynomorphs in the borehole V 800 Střeleč (Jizera Development, Bohemian Cretaceous Basin)


Marcela Svobodová

Geoscience Research Reports 44, 2011 (GRR for 2010), pages 120–127
Map sheets: Sobotka (03-34)

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Borehole V 800 Střelec was drilled in the area of the UNESCO Geopark "Bohemian Paradise" across the Turonian/Coniacian boundary and reached the lithostratigraphic boundary of the Teplice and Jizera formations. Based on the palynomorph content in pelitic sediments, Late Turonian age is based on the presence angiosperm pollen Plicapollis sp., Minorpollis sp., Trudopollis sp., Complexiopollis sp. Coniacian age is evidenced by the presence of angiosperm pollen of the Normapolles group - Oculopollis sp., Emscheripollis sp. And dinoflagellate cyst Apteodinium deflandrei, Gradual deepening in lower part of the borehole (Late Turonian) is documented by higher dinoflagellate cyst diversity, presence of chorate, neritic types, i.e. Oligosphaeridium complex, Surculosphaeridium longifurcatum and outer neritic type, i.e., Chlamydophorella. The sediments in the upper part of the borehole (Coniacian) deposited in shallower marine environment than in lower part of the borehole (higher percentage of proximate dinocyst Chatangiella, Isabelidinium, Xenascus, Odontochitina as well as foraminiferal linings and acantomorph acritarchs). The preservation of palynomorph assemblage depends on the amount of amorphous organic matter and pyrite, especially in pelagic facies of the Teplice Formation. Material for palynological study was sampled during geological mapping (03-342 Rovensko pod Troskami) from the borehole V 800 Střeleč.