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2 Annales Societatis Geologorum Poloniae

2 2021

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New dimorphic species of the genus Rollierites Jeannet from southern Poland

Jain Sreepat, Mazur Marek

Annales Societatis Geologorum Poloniae

2021

Vol. 91, No. 4

405--418

A new ammonite assemblage from the lower beds of the Ogrodzieniec Quarry (southern Poland), the only Callovian section in the middle part of the Polish Jura Chain, is described. It includes the presence of Kosmoceras rotundum (Quenstedt), followed by the first example of co-occurring micro- and macroconchs in the genus Rollierites (R. biplicatum sp. n.) and above it, the association of Euaspidoceras sp. and Peltoceratoides (Parawedekindia) gerberi Prieser. Both R. biplicatum sp. n. (m and M; microconch and macroconch) and K. rotundum are assigned to the late Callovian Lamberti Zone. P. (P.) gerberi characterizes the early Oxfordian Cordatum Zone. This is the first record of the genus Rollierites from Poland. This study extends the upper age limit of the middle Callovian Rollierites up to the late Callovian Lamberti Zone. On the basis of morphological and stratigraphical data, it is tentatively proposed that the origin of the early–middle Oxfordian Tornquistes may be in the middle–late Callovian Rollierites, rather than the previously proposed late Callovian Pachyceras. However, this is speculation, as the present data set is insufficient.

Callovian and Kimmeridgian fossils and stratigraphy of the Blue Nile Basin (central western Ethiopia)

Jain Sreepat, Schmerold Roland

Annales Societatis Geologorum Poloniae

2021

Vol. 91, No. 3

287--307

A refined, stratigraphic and biostratigraphic framework for Ethiopia has a strong bearing on the Jurassic sedimentary evolution, not only for the Horn of Africa, but also for the North African region. The present contribution provides an updated Callovian-Kimmeridgian stratigraphy and biostratigraphy, on the basis of the occurrences of age-diagnostic ammonites from Dejen (Blue Nile Basin; central western Ethiopia). Here, the late Callovian (Lamberti Zone) ammonite Pachyceras cf. lalandeanum (d'Orbigny) is associated with the nautiloid Paracenoceras cf. giganteum (d'Orbigny). The early Kimmeridgian Orthosphinctes aff. tiziani (Oppel) is associated with the nautiloids Paracenoceras cf. kumagunense (Waagen) and P. cf. ennianus (Dacqué) and a large gastropod Purpuroidea gigas (Étallon). The previously recorded middle Callovian ammonite Erymnoceras cf. coronatum (Bruguiere) is associated with the now recorded P. gigas (Étallon). Additionally, the age of the Antalo Limestone Fm is also reassessed on the basis of the ammonite records from the three basins - Ogaden, Blue Nile and Mekele. The Ogaden Basin strata span from the late Callovian to the late Tithonian (from ammonite records), the Blue Nile Basin from the early Callovian to the late Tithonian (calcareous nannofossils) and the Mekele Basin from the uppermost middle Oxfordian to the early Kimmeridgian (ammonite records). However, the upper age assignments should be considered tentative, as much of the previously recorded Oxfordian-Kimmeridgian ammonite fauna needs taxonomic re-evaluation and precise resampling. Contextually, it should be mentioned that in all the three sedimentary basins, the top part of the Antalo Limestone Fm did not yield any ammonites.