Middle Oxfordian–Lower Kimmeridgian Calcareous Nannoplankton and Foraminifers in Ivanovo Oblast, European Part of Russia M
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ISSN 0869-5938, Stratigraphy and Geological Correlation, 2018, Vol. 26, No. 7, pp. 771–782. © Pleiades Publishing, Ltd., 2018. Middle Oxfordian–Lower Kimmeridgian Calcareous Nannoplankton and Foraminifers in Ivanovo Oblast, European Part of Russia M. A. Ustinova* Geological Institute, Russian Academy of Sciences, Pyzhevskii per. 7, Moscow, 119017 Russia *e-mail: [email protected] Received April 6, 2017; in final form, September 12, 2017 Abstract⎯Middle Oxfordian–lower Kimmeridgian calcareous nannoplankton and foraminifers were first studied from the core log of the well drilled in Ivanovo oblast. Nannoplankton is well preserved; in total, nearly 25 species were identified. Zone NJ15 was distinguished on the basis of nannoplankton. Coccoliths of representatives of the genus Watznaueria, which are mostly cospomopolitan species, are dominant quantita- tively. A sharp prevalence of W. britannica coccoliths indicates unstable habitat conditions in near-surface waters and their mesotrophy. Foraminifers typical of the Opthalmidium strumosum–Lenticulina brestica and Lenticulina kuznetsovae–Epistomina praetatariensis zones were studied as accompanying microfauna for substantiation of the age of country deposits. Keywords: Jurassic system, calcareous nannoplankton, foraminifers, Oxfordian, lower Kimmeridgian, Iva- novo oblast DOI: 10.1134/S0869593818070055 INTRODUCTION MATERIALS AND METHODS The material for research works was the core of The Upper Jurassic calcareous nannoplankton of Well 1, collected by A.G. Olfer’ev in the early 2000s the Russian Plate is still poorly studied. Some data on and later provided to the author by A.G. Alekseev the nannoplankton from the middle Oxfordian–lower (Moscow State University). Kimmeridgian substages of the Gorodishche section In total, we studied 12 samples weighing 20–30 g (Ulyanovsk Volga Region) were presented by Nikifor- each, collected with an interval of 1.0 m from the ova (1986) and Cooper (1987). In this section, Bown Jurassic part of the core section of Well 1. Well-pre- et al. (1988) distinguished stratotypes of Zones NJ16– served nannoplankton and foraminifers occur in all NJ17. Later, the data on nannoplankton distribution samples. Coccolithophora were extracted with a stan- in the Volgian deposits of this region (Gorodishche dard procedure (Bown and Cooper, 1998). They were and Kashpir sections) were supplemented in the fol- studied under a BiOptik light polarized microscope at lowing works (Kessels et al., 2003; Ruffel et al., 2002). ×1000 magnification in the laboratory of biostratigra- phy and paleogeography of the oceans of the Geolog- The Oxfordian nannoplankton in the European part ical Institute of the Russian Academy of Sciences. of Russia was studied to a lesser extent. Matveev pub- Images were taken using a light microscope (crossed lished data on nannoplankton from the lower Oxford- nicols) and MV 2300 Vega Tescan electron scanning ian interval in the Dubki section (Saratov Volga microscope at the Geological Institute of the Russian Region) and the middle–upper Oxfordian section in Academy of Sciences. The relative amount of nanno- the Ioda River (Yaroslavl oblast) (Kiselev et al., 2013; plankton was determined in the following way: Matveev, 2007, 2009). The author studied nanno- much, 5–15 specimens per one field of vision; fre- plankton from the Oxfordian deposits uncovered by quent, 1–4 specimens per field of vision; rare, wells in the city of Moscow (Ustinova, 2009; Ustinova 2‒5 specimens per 2–5 fields of vision; little, 1 speci- men per more than 10 fields of vision. The relative and Radugina, 2004). The calcareous nannoplankton amount of species throughout the entire specimen (a in Ivanovo oblast was not studied previously. There are cover glass 4 cm2) was estimated under a light micro- no data published on the Kimmeridgian–Oxfordian scope. Foraminifers occur in samples in a small foraminifers of the given area, while in adjacent areas amount, which is due to a small weight of samples. (first of all in Kostroma oblast) foraminifers of this age However, their species composition made it possible are well studied. This work aims to fill this gap. to distinguish zones and to clarify the age, earlier 771 772 USTINOVA established by Olfer’ev, which subdivided the section RESULTS into formations on the basis of the lithological features of deposits. Nannoplankton. Throughout the section, there are Biscutum dubium (Noël), Cretarhabdus conicus Bram- lett et Martini, Cyclagelosphaera margerelii Noёl, CHARACTERISTICS OF THE SECTION С. tubulata (Grün et Zweili), Ethmorhabdus gallicus Noël, Hexapodorhabdus cuvilleri Noël, Polypodorhab- Well no. 1 was drilled near a farm in the village of dus escaigii Noёl, Staurolithites quadriarculla (Noël) Ovechkino (Vichuga district, Ivanovo oblast) in the Wilcoxon, 1972, Stradnerlithus geometricus (Górka) watershed, 14 km to the west of the settlement of Bown et Cooper, Stephanolithion bigotii bigotii Deflan- Staraya Vichuga (Fig. 1). The absolute mark of the well dre, Zeugrhabdotus erectus (Deflandre in Deflandre et head is 145.0 m. The description of the section and col- Fert), Z. fissus Grün et Zweili, Watznaueria barnesae lection of samples were performed by A.G. Olfer’ev. (Black), W. britannica (Stradner) Reinhardt, W. fos- The upper 12.1 m interval (Beds 1–4) is composed of sacincta (Black) Bown in Bown et Cooper, and W. aff. Quaternary loams. manivitae Bukry. The Oxfordian part of the section is Bed 5. Interval 12.1–21.4 m. Aleurite is coarse, characterized by the occurrence of Axopodorhabdus dark gray, clayey, micaceous, with thin subhorizontal cylindratus (Noёl) Wise et Wind, Lotharingius cruci- intercalations of light aleurite, platy. Bed 5 can be centralis (Medd) Grün et Zweili, Lotharingius sp., attributed most likely to the upper Hauterivian Podorhabdus grassei Noël and Retecapsa cf. R. schizo- Savel’evo Formation (Olfer’ev, 2013). brachiata (Gartner) Grün in Grün et Allemann, Stau- Bed 6. Interval 21.4–23.6 m. Clay is dark gray, cal- rolithites stradneri (Rood et al.), and Anfractus harri- careous, ductile, lumpy, with clay-type phosphorite sonii Medd (Plates I, II). In the Kimmeridgian inter- concretions up to 2 cm in diameter. val, Staurolithites lumina Bown and Axopodorhabdus rahla (Noёl) Grün et Zweili occur as single specimens Bed 7. Interval 23.6–28.0 m. Clay is dark gray, (Fig. 2, Plate I). lighter compared to the overlying bed, calcareous, indistinctly laminated and lumpy. The contact with The above-described complex can be attributed to the underlying bed is distinct. Beds 6 and 7 can be Zone NJ15 Cyclagelosphaera margerelii in the Boreal attributed to the Makar’evo Formation, covering the Realm (Bown and Cooper, 1998), covering the inter- uppermost part of the upper Oxfordian–lower Kim- val from the upper part of the lower Oxfordian meridgian (Unifitsirovannaya…, 2012). (ammonite Cordatum Zone) to the terminal part of the upper Kimmeridgian (ammonite Autissiodorensis Bed 8. Interval 28.0–29.3 m. Clay is gray, thinly Zone) (Bown and Cooper, 1998; Bown et al., 1988). aleuritic, indistinctly platy, with ferruginous oolites, The stratotype of this zone was distinguished in the with fine shell detritus. This bed is attributed by section of a well drilled in Denver, southeastern Olfer’ev to the Moscovian Formation, but in other England. This zone is also distributed in southern areas of the Moscow syneclise within this formation, England and northern France (Bown et al., 1988). It is ferruginous oolites have not been found (Unifitsiro- characterized by the occurrence of Watznaueria bri- vannaya …, 2012). The lower contact is distinct. The tannica (dominant species), Axopodorhabdus cylindra- similar section was described by A.P. Ivanov in 1910 tus, Biscutum dubium, Cyclagelosphaera margerelii, near the villages of Pushkino and Ivannikovo (Kost- Ethmorhabdus gallicus, Polypodorhabdus escaigii, roma oblast) (Starodubtseva and Mitta, 2012). Stephanolithion bigotii bigotii, Staurolithites stradneri, Bed 9. Interval 29.3–34.0 m. Clay is gray with and Zeugrhabdotus erectus. In terms of distribution of brownish tint, insignificantly micaceous, with ochre- Lotharingius crucicentralis in the core section, the colored spots and stains, with concretions of solid occurrence of the lower subzone NJ15а is proposed, oolitic marl. At the base is an intercalation of ferrugi- while the upper subzone NJ15b cannot be reliably nous glauconitic sand with abundant ferruginous identified (Bown and Cooper, 1998). Stratotypes of oolites. The lower contact is distinct. This bed is the subzones NJ15a and NJ15b are located in Ober- attributed by A.G. Olfer’ev to the Velikodvorskaya langheim, southwestern Germany (Bown et al., 1988). Formation of the middle Callovian. According to the published data, the subzone NJ15a Bed 10. This interval, revealed by A.G. Olfer’ev, is occurs in England, northeastern France, Spain, and missing in the lithological description of the well. Clay Switzerland (Colombie et al., 2014; Lees et al., 2004). is aleuritic, reddish brown with beige tint and thin blu- Within the Russian plate, the subzone NJ15a can be ish gray stains, with calcareous nodules up to 1 cm in distinguished in several wells drilled in the city of Mos- diameter. In the lower part of the bed is coarse clayey cow (Ustinova and Radugina, 2004). However, in aleurite. This bed is attributed to the Yur’evetskaya other wells from this region, this zone cannot be dis- Formation of the Sludkinsky Horizon of the Olenek tinguished with confidence (Ustinova,