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).