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Ammonite stratigraphy and organic matter of the Pałuki Fm.n(Upper Kimmeridgian–Lower Tithonian) from the central-eastern part of the Łódź Synclinorium (Central Poland)

Wierzbowski Andrzej, Wierzbowski Hubert

Volumina Jurassica

2019

Vol. 17, no. 1

49--80

The ammonite biostratigraphy as well as the organic matter content, its type and maturity of the Pałuki Formation, belonging to the fine, siliciclastic Kimmeridge Clay type facies, were investigated in five deep boreholes from the central-eastern part of the Łódź Synclinorium in Central Poland. The studied deposits are assigned to the Eudoxus and Autissiodorensis zones of the Upper Kimmeridgian as well as the Klimovi, Sokolovi, Pseudoscythica and Puschi (=Tenuicostata) zones of the Lower Tithonian (“Lower Volgian”). The Pałuki Formation shows in its lower and middle parts average TOC concentrations of ca. 2.5 wt.% and prominent, restricted increases in organic matter content, which are found in the mid-Eudoxus Zone, the lowermost part of the Autisiodorensis Zone, and at the Sokolovi–Pseudoscythica zone boundary. These stratigraphical intervals correlate well with rich in organic matter levels present in the Kimmeridge Clay Formation of NW Europe. The periodic expansions of Submediterranean and Subboreal-Boreal ammonites corresponded mostly to the transgressive phases, often correlated with a higher content of organic matter. The development of special morphologies of ammonites, such as the small-sized, nectopelagic forms of Nannocardioceras in the Late Kimmeridgian, has also been related to the deposition of shales rich in organic matter during the transgression maxima. The organic matter present in the Pałuki Formation mostly consists of Type II kerogen and is immature or early mature with respect to hydrocarbon generation, which is in agreement with previously published data. Evaluation of the new and published geochemical, lithological and structural data from the Pałuki Formation in the central-eastern part of the Łódź Synclinorium shows that these deposits could not have been a considerable source of crude oil or gas.

New data on ammonites and stratigraphy of the uppermost Kimmeridgian – lowermost Volgian of the Middle Volga region (Russia)

Mitta V., Scherzinger A.

Volumina Jurassica

2006

Vol. 4, no. 1

191-192

New collections at the boundary of the Kimmeridgian and Volgian from the Volgian Stage lectostratotype section nearby Gorodishche (central Russia) make it possible to give a general view on the stratigraphic distribution of some of the important ammonite taxa. For the first time Sutneria eumela (d’Orbigny) and Sutneria subeumela Schneid from the Upper Kimmeridgian are illustrated, and Aulacostephanus volongensis Khudyaev is recognized. The latter is the macroconch of Aulacostephanus undorae (Pavlow). These discoveries indicate the chronostratigraphic correlation between the Eudoxus and Fallax zones of the Russian Platform and the Pseudomutabilis and Beckeri zones of the Submediterranean region. “Discosphinctoides” subborealis Kutek & Zeiss is placed in the genus Sarmatisphinctes Kutek & Zeiss and “Glochiceras (Paralingulaticeras)” efimovi Rogov belongs to a new ammonite genus. In the beginning of the Volgian a strong faunal provincialism has been perceptible which makes correlations with areas outside the Russian Plate and Central Poland more difficult. The lowermost part of the Lower Volgian (Klimovi Zone) seems to be time equivalent at least in part, if not wholly, of the Upper Kimmeridgian. Because of different interpretation of the Autissiodorensis Zone Ziegler 1962 in the localities of West Europe and the Russian Platform we give the priority to the term Fallax Zone Ilovaisky 1941. The name “Autissiodorensis Subzone” does not seem the best choice for the lowermost Subzone of the Fallax Zone of the Russian Kimmeridgian. Up to now no figured specimen of A. autissiodorensis from the Russian Platform has been indicated. According to our opinion the best index fossil for the base of the Fallax Zone in the area of study seems to be Amoeboceras volgae (Pavlow), and we recommend using the term Volgae Subzone in future. More information about results of our study are given in Scherzinger and Mitta (in press).