Jurassic Ostracods of the European Part of the Former Soviet Union: Research Challenges and Successes
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ssic Ostracods of the European Part of the Former Soviet Union: Research Challenges and Successes E. M. Tesakovaa, b, * a
Department of Geology, Lomonosov Moscow State University, Moscow, Russia bGeological Institute, Russian Academy of Sciences, Moscow, Russia *e-mail: [email protected] Received October 9, 2019; revised October 10, 2019; accepted October 10, 2019
Abstract—Interest in the Mesozoic ostracods of the Russian Plate first emerged in the 1930s due to industrialscale oil and gas prospecting. This article provides informative summaries of all significant publications of the past century devoted to the Middle and Upper Jurassic ostracods of the Russian Plate and its framing: the Dnieper–Donets Depression, the northwestern sink of Donbass, Moscow, Ukraine, Pechora, and Volga– Ural syneclises, and the Crimean–Caucasian and Central Asian regions. The history of research on Jurassic ostracods in the European part of the former Soviet Union is divided into three periods, each of which is of particular importance and meets the specific requirements of its time. Keywords: history of science, ostracods, the Jurassic, Russian platform DOI: 10.1134/S207908642004009X
INTRODUCTION Industrial-scale oil and gas prospecting in the European part of the former Soviet Union is fraught with certain difficulties, since strata that are potentially productive for hydrocarbon extraction lie at different depths within the sediment cover of the Russian Plate (RP), i.e., they are located in a closed area, and drilling is needed to reach them. It is necessary to determine the geological time and paleoecological conditions of their formation as accurately and reliably as possible in order to distinguish and delineate these sedimentary bodies. Ammonites, a group of cephalopod mollusks, represent the most accurate biological chronometer that can be used to distinguish between the time intervals of minimal possible duration in the Mesozoic sedimentary rocks. The most reliable and detailed scale (the ammonite standard) based on ammonite evolution was developed for the Jurassic RP; virtually all problems of applied geology can be solved with this scale. However, this method has its drawbacks, because ammonite shells are most often found in open geological sections (in quarries, ravines, and coastal cliffs) and are much less likely to be present in borehole cores. The dating of core samples from different depths is associated with the analysis of small samples of material; therefore, the development of other scales parallel to the ammonite standard is necessary. These scales should be developed for microscopic organisms that are abundant and often present throughout the borehole section. The study of fossil ostracods, micro-
scopic benthic crustaceans, is of particular interest, since their ability to resettle and migrate was very limited due to the lack of planktonic larvae (the absence of the planktonic stage in the life cycle of ostracods). This feature, combined with extremely high sensitivity to environmental changes, makes ostraco
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