The stratigraphy of the Oligocene-lower Miocene deposits of southern Ukraine

Chia sẻ: Tần Mộc Phong | Ngày: | Loại File: PDF | Số trang:38

Thêm vào BST

Báo xấu

15
lượt xem 2
download

Download Vui lòng tải xuống để xem tài liệu đầy đủ

Lithostratigraphic units (formation, strata, and beds) and regional stages of the Oligocene-lower Miocene succession of southern Ukraine are described based on the results of comprehensive lithological and paleontological data analysis. The historical perspective on the stratigraphical investigations of the Maikop Group in the Crimean and Kerch Peninsulas and their equivalents in the broader Peri-Black Sea Region were also integrated in this overview. Moreover, a correlation was established between the locally defined regional stages and specific stratigraphic horizons of southern Ukraine, the global Oligocene and Miocene stages (defined by the International Stratigraphic Chart), and the stages of the Eastern Paratethys.

Chủ đề:

Bình luận(0) Đăng nhập để gửi bình luận!

Lưu

Nội dung Text: The stratigraphy of the Oligocene-lower Miocene deposits of southern Ukraine

Turkish Journal of Earth Sciences Turkish J Earth Sci (2020) 29: 170-207 http://journals.tubitak.gov.tr/earth/ © TÜBİTAK Research Article doi:10.3906/yer-1905-24 The stratigraphy of the Oligocene-lower Miocene deposits of southern Ukraine Yuliia V. VERNYHOROVA*, Tamara S. RYABOKON Department of Stratigraphy and Paleontology of the Cenozoic Deposits, Institute of Geological Sciences, National Academy of Sciences of Ukraine, Kyiv, Ukraine Received: 31.05.2019 Accepted/Published Online: 07.10.2019 Final Version: 02.01.2020 Abstract: Lithostratigraphic units (formation, strata, and beds) and regional stages of the Oligocene-lower Miocene succession of southern Ukraine are described based on the results of comprehensive lithological and paleontological data analysis. The historical perspective on the stratigraphical investigations of the Maikop Group in the Crimean and Kerch Peninsulas and their equivalents in the broader Peri-Black Sea Region were also integrated in this overview. Moreover, a correlation was established between the locally defined regional stages and specific stratigraphic horizons of southern Ukraine, the global Oligocene and Miocene stages (defined by the International Stratigraphic Chart), and the stages of the Eastern Paratethys. The Planorbellian regional stage (early Rupelian) includes the Borysfen, Planorbella, Indol, and Eastern-Kerch Formations and Diurmen Beds. The Molochnian regional stage (late Rupelian) includes the Molochna and Azamat Formations and the Kop-Takil Strata. The Kerleutian regional stage (latest Rupelian-Chattian) includes the Kerleut, Sirohozy, Askaniia, and Hornostaivka Formations and the Chorelek and Clay Stratum. The Bathysiphonian regional horizon (Aquitanian–Burdigalian) includes the Arabatska, Alahol, Chornobaivka, and Mayachka Formations and the Karha Beds. This horizon is also considered as age-equivalent to the Caucasian, Sakaraulian, and Kotsakhurian regional stages of the lower Miocene in the Eastern Paratethys. The Oligocene-early Miocene age of all these lithostratigraphic units belonging to the megaregional Maikop Group is substantiated by paleontological data. This work represents the latest stratigraphic model of Oligocene-lower Miocene deposits in southern Ukraine as a part of the Eastern Paratethys Basin. Key words: Stratigraphy, lithostratigraphic units, Oligocene, lower Miocene, Maikop Group, southern Ukraine 1. Introduction use of lithological criteria for stratigraphic subdivision The Oligocene-lower Miocene deposits are widespread of these deposits, especially in geological mapping, was on the mainland of southern Ukraine and represented by severely hindered by the lithofacial monotony of these the Maikop Group succession on the Crimean and Kerch sediments, especially in the basinal segments. Stratigraphic Peninsulas and its age-equivalent rocks in the northern subdivision using biostratigraphy was, and still is, limited Peri-Black Sea Region. These sediments are mainly by the scarcity of both micro- and macrofossils. Moreover, sandy-clays rocks with negligible carbonate content, with many subsurface sections of the Maikop Group in the a typical thickness ranging from a few tens of meters region remain insufficiently studied in terms of detailed to 3100 m. Extensive work on these units began in the litho- and biostratigraphic work. All these challenges 1920s and 1940s in the Crimean and Kerch Peninsulas posed, and continue to pose, difficulties in identifying and and in the 1950s and 1960s in the broader northern Peri- defining proper lithostratigraphic units (i.e. formations, Black Sea Region. These investigations partly aimed at members, and strata) in the Oligocene-lower Miocene understanding of oil-gas potential of these deposits, but succession of southern Ukraine as reflected in the the potential for prospecting and exploration for some numerous and variable stratigraphic schemes published other minerals (e.g., manganese) was also considered. As during the last 50 years (e.g., Muratov, 1969; Teslenko, a result, the Ukrainian Geological Survey has accumulated 1984; Makarenko et al., 1987; UMSK, 1993). extensive material on the lithofacies and paleontological The creation of a modern stratigraphic scheme of the features of the Oligocene-lower Miocene units of southern Maikop Group in the broader region of southern Ukraine Ukraine. Unfortunately, no single full-scale survey of these requires the revision of all the available lithological and deposits has been carried out since the 1980s. Despite the paleontological features of the Oligocene-lower Miocene thorough and detailed studies of the Maikop Group, the deposits in the area. Moreover, the stages defined in * Correspondence: july.vern@gmail.com 170 This work is licensed under a Creative Commons Attribution 4.0 International License.
VERNYHOROVA and RYABOKON / Turkish J Earth Sci southern Ukraine need to be correlated with the regional 3. Data stages of the Eastern Paratethys, including the nearby This overview is largely based on the results obtained Ciscaucasian region. by the authors in the framework of the scientific project “Creation and modernization of the stratigraphic schemes 2. Geological setting of the Phanerozoic deposits of Ukraine” carried out In a geographic sense, the study area is located on the by the Institute of Geological Sciences of the National mainland of southern Ukraine within the northern Peri- Academy of Sciences of Ukraine between 2008 and 2012. Black Sea Region and the Crimean and Kerch Peninsulas During this project, the authors developed and refined the (Figure 1). In geologic terms, it is situated in the southern stratigraphic scheme of Paleogene and Neogene deposits part of the East-European Platform, the Scythian Plate, of the broader southern Ukraine, including those of the the Southern Crimean Orogene, and the western part Crimean and Kerch Peninsulas, the northern Peri-Black of the Indol-Kuban Trough. During the Maikop epoch Sea Region, and adjacent parts of the Ukrainian Shield (Oligocene to early Miocene), sedimentation occurred in and Azov Massif (Figure 1). Geological data obtained by a shallow-water (northern Peri-Black Sea Region) and a the authors in the process of scientific support of other deeper-water (Crimean and Kerch Peninsulas) segment of projects, such as the geological mapping of the territory the broad Scythian Sea, located on the northern shelf of the of Ukraine, were also used. These included the results of Eastern Paratethys (e.g., Popov et al., 2009). To the north biostratigraphic investigation and the structure-facial of the Parpach Ridge and the east of Kerch Peninsula deep zonation of Paleogene and Neogene deposits of the Maikop depocenters developed with sediment thicknesses territory of sheets L-36-XI, L-36-XII, L-37-VIII (in the of more than 3000 m. northern Peri-Black Sea Region), L-36-XXVIII (the Alma There are two main tectonic reasons for these observed Depression on the Crimean Peninsula), L-36-XXX, L-36- dramatic Maikop thickness changes across our study area. XXIV, L-37-XIX, and L-37-XXV (the Kerch Peninsula) On the one hand, the Maikop succession appears to be a (e.g., Vernyhorova, 2014, 2015, 2016; Zernyetskiy et al., passive infill in the subbasins formed during the Eocene 2015; Ryabokon, 2016; Vernyhorova and Ryabokon, 2018). inversion along the entire northern perimeter of the Black This study is the result of comprehensive data analysis Sea (e.g., Khriachtchevskaia et al., 2010). On the other and integration of litho- and biostratigraphic data of the hand, especially in the SE part of our study area towards the Maikop deposits in the Crimean and Kerch Peninsulas and Indolo-Kuban Basin, active tectonic subsidence occurred their correlative units in the broader southern Ukraine during the deposition of the Maikop sediments in the collected for more than a century. In our studies, we foredeep of the already active Great Caucasus thrust-fold followed the stratigraphic classification and nomenclature belt (e.g., Vincent et al., 2007). of the Stratigraphic Code of Ukraine (Gozhyk, 2012). Figure 1. Location map of the studied areas in broader southern Ukraine. Note location of stratigraphic correlation transect shown in Figure 2. 171
VERNYHOROVA and RYABOKON / Turkish J Earth Sci 4. Results and discussion frequency, and nature of interbedding with clay rocks In the following subsections we briefly summarize the penetrating into deep boreholes (e.g., Gozhyk et al., 2006a). main characteristics of the Maikop Group in our study However, the stratigraphic correlation of these subgroups area. For a more in-depth and historical perspective on the to the regional stages of the Oligocene-lower Miocene evolution of stratigraphic schemes in southern Ukraine in southern Ukraine or to the stages of the International the reader is referred to the work of Vernyhorova and Stratigraphic Chart (ISC) remains conditional. Ryabokon (2018). The thickness of the Maikop Group in southern 4.1. Lithostratigraphic units of the Oligocene-lower Mio- Ukraine reaches 3100 m. Generally, the Maikop Group cene of southern Ukraine transgressively overlies the underlying Eocene deposits The Maikop Group was described for the first time by and it is covered by Neogene and sometimes Quaternary K.I. Bohdanovich, I.M. Hubkin, K.A. Prokopov, and sediments. S.I. Charnotskiy (quoted by Borissjak, 1937) as a “Maikop 4.1.1. Oligocene, Rupelian Stage, Planorbellian regional oil-bearing series”, which is “conformably covered by stage of southern Ukraine the Second Mediterranean stage and underlain by 4.1.1.1. Planorbella Formation Foraminifera beds” (translation from Russian; Gubkin, The name of this formation comes from the gastropod 1912, p. 1). It is named after the city of Maikop in the Russian genus Planorbella frequently found in it (Teslenko, Caucasus (Likharev, 1956; Vereschagin, 1982). In the first 1984). V.V. Menner and Z.L. Maimin (Maimin, 1951) stratigraphic dictionary of the former Soviet Union, the distinguished the deposits with Planorbella as the Indol Maikop Group was uniquely defined as “clay and sandy- (Planorbella) horizon in the lower part of the Maikop clay body of rocks, lying between the Foraminifera beds Formation of the Crimea. D.Ye. Makarenko (Syabryai, (Eocene) and the Tarkhan horizon of Andrusov (beds with 1963) described beds with Planorbella of the Crimea as a Pecten denudatus)” (see Borissjak, 1937, p. 124). formation. The Planorbella Formation is a type formation The Maikop Group in the general southern region of of the Planorbellian stage and it is widespread in the the former Soviet Union is classically divided into three Crimean Plain and the general northwestern shelf of the parts, namely lower, middle, and upper, but “in different Black Sea. Type section: Well 246-k (590–634 m), drilled areas in different ways” (Vereschagin, 1982, p. 272). on the Artemovskoe (Karlovskoe) uplift at the Tarkhankut In the Crimea-Caucasus region (as part of the Eastern Peninsula of the Crimea (Pechenkina, 1971; Makarenko et Paratethys), the Maikop Group traditionally has different al., 1987; Figure 4). Reference section: Well 2 (59.5–192 stratigraphic schemes in many areas, with subdivision to m), drilled near Kocherhino village of the Bakhchisaray various formations (Vereschagin, 1982, p. 272). district, Crimea (Figures 4 and 5). The Maikop Group in southern Ukraine has various The Planorbella Formation is composed of clay marine facies sediments, mainly sandy-argillaceous and rocks. It is divided into two members, mainly based on typically noncalcareous deposits, which were deposited their respective foraminifera assemblages. The Lower between the top Eocene and the Tarkhanian regional Planorbella Member comprises gray, dark-gray, sometimes stage of the middle Miocene. The Maikop Group in brownish-gray and greenish-gray clays with thin-layered, southern Ukraine is also traditionally subdivided into irregularly calcareous and noncalcareous intervals. The Lower, Middle, and Upper subgroups (Teslenko, 1984). Lower Member has a thickness of 80–100 m, sometimes Chronostratigraphically, the Lower Maikop subgroup up to 150 m. On the NE Crimean Plain the Lower Member corresponds to the Planorbellian and Molochnian regional consists of clayey sandy aleurolite deposits, with thickness stages, the Middle Maikop subgroup corresponds to the of up to 20–40 m. In SW Crimea, in the Crimean foothills, Kerleutian regional stage of southern Ukraine, and the the Lower Planorbella Member consists of alternating Upper Maikop subgroup corresponds to the Caucasian, clays (thickness of 0.5–1 m) and aleurolites (thickness 0.3– Sakaraulian, and Kotsakhurian regional stages of the 0.4 m), characteristic for the upper part of the Kyzyldzar Eastern Paratethys. The latter subgroup is also described as strata (Zernyetskiy et al., 2015). The Upper Planorbella the Bathysiphonian regional horizon (Figure 2). It should Member consists of gray, dark-gray, and brownish-gray be emphasized that subgroups of the Maikop Group laminated clays with siderite intercalations. The thickness in southern Ukraine differ in their stratigraphic extent of this member varies from 100–150 m to 230–250 m. from the lower, middle, and upper Maikop of northern In SW Crimea, in the Crimean foothills, the Upper Ciscaucasia and are not equivalent in age (Figure 3). Planorbella Member is known as the Zubakino beds. In In the Azov-Black Sea region, in the absence of that area the beds comprise dark-gray, greenish-gray, paleontological information, the Maikop Group is divided brownish-gray clays, noncalcareous, silty, sometimes with into three subgroups based on the presence or absence of interbeds of glauconitic sand and gravel (Syabryai, 1963; layers of sandstones and siltstones, their relative thickness, Nemkov et Shutskaya, 1971). The average thickness of the 172
VERNYHOROVA and RYABOKON / Turkish J Earth Sci NORTHERN PERI-BLACK SEA REGION Figure 2. Chronostratigraphic summary of the Oligocene-lower Miocene succession in southern Ukraine. For an approximate location see Figure 1. Zubakino beds is 10–15 m. The Planorbella Formation and bones, sponge spicules, and fish otoliths are also noted conformably and transgressively overlies the Eocene for the formation. Alma Formation (Bogayets et al., 1972), but with some The biostratigraphy of the Lower Planorbella Member erosional stratigraphic gaps on the basin margins. In turn, (e.g., Shvemberger, 1967; Muratov, 1969; Pechenkina, the Planorbella Formation is conformably overlain by 1971; Bogayets et al., 1972; Nosovskiy et al., 1984; Kraeva the Azamat Formation of the Molochnian regional stage and Lulyeva, 1985; Ivanova, 2003; Bogdanovich, 2005; (Figure 2). Anistratenko et al., 2012) includes benthic foraminifera The typical biostratigraphic spectrum of the assemblages of zone “Lenticulina” herrmanni, beds with Planorbella Formation (Muratov, 1969; Bogayets et al., Bolivina mississippiensis and beds with Ammomarginulina, 1972; Nosovskiy et al., 1984; Figure 6) includes a mollusk Haplophragmoides deformabilis; a plankton foraminifera assemblage with Nucula compta Goldf., Astarte kickxi association with dominating Globigerina officinalis (Subb.) Nyst., Pleurotoma selysii Koen., Thiasira unicarinata Nyst., among Tenuitella Liverovskayae (N.Byk.), T. khadumica Cystodaria angusta Nyst & West., and others, characteristic (N.Byk.), T. denseconnexa (Subb.), Turborotalia for the Rupelian of Western Europe, the Khadumian ampliapertura (Bolli), Globigerina praebulloides Blow, horizon of northern Ciscaucasia, and the Borysfen Pheudohastigerina micra (Cole), and Dipsidripella ex gr. Formation of the northern Peri-Black Sea Region (Popov danvillensis (Howe et Wallace); the NP 21 zone; and a et al., 1993, 2009), as well as radiolarian Cenosphaera spore and pollen assemblage with dominating pollen of almaensis Moksjak. Accumulations of pteropods (better Pinaceae (Picea sp., Tsuga sp.) and Taxodiaceae (Taxodium known in the literature as Planorbella), fish scales, teeth distichformis, Sequoia sempervirifirmis, Glyptostrobus sp.). 173
VERNYHOROVA and RYABOKON / Turkish J Earth Sci Figure 3. Comparison of the division of the Maikop Group into separate units in southern Ukraine and Ciscaucasia in terms of the Eastern Paratethys stages (Vernyhorova and Ryabokon, 2018 with corrections). The biostratigraphy of the Upper Planorbella Member and increasing numbers and diversity of Pinus, Quercus, (e.g., Shvemberger, 1967; Muratov, 1969; Pechenkina, Juglans, and Carya. 1971; Bogayets et al., 1972; Kraeva and, Lulyeva, The Rupelian age of the Planorbella Formation 1976, 1985; Nosovskiy et al., 1984; Ivanova, 2003; was established based on mollusks, foraminifera, and Bogdanovich, 2005; Anistratenko et al., 2012) includes calcareous nannofossils. This formation is correlated with the Rupelian benthic foraminifera provincial zone the Borysfen Formation of the northern Peri-Black Sea Spiroplectammina oligocenica; the Oligocene association Region, the Indol Formation on the east of the Crimean of plankton foraminifera Globigerina ouachitaensis Plain, and the Eastern-Kerch Formation of the Kerch ouachitaensis (Howe & Wall.), G. officinalis Subb., Peninsula (Figure 2). G. praebulloides leroy Blow & Banner, G. ciperoensis Bolli, Turborotalia ampliapertura (Bolli), Tenuitella 4.1.1.2. Borysfen Formation angustiumbilicata (Bolli), Chiloguembelina gracillima The formation was identified first by M.F. Nosovkiy (Andreae), and others; the NP 22 zone; and a spore and (Nosovskiy and Savenko, 1963). The name is taken after pollen assemblage with reducing pollen of Taxodiaceae Borysfen, the ancient name of the River Dnieper (Dnipro). 174
VERNYHOROVA and RYABOKON / Turkish J Earth Sci Figure 4. Geological profile from the northwestern shelf of the Black Sea to the foothills of the Crimea Mountains. The Borysfen Formation is widespread in the northern Formation consists of three beds, namely an under-ore bed, Peri-Black Sea Region and in the adjacent part of the manganese ore bed, and supra-ore bed. Here the thickness Ukrainian Shield and Near-Azov Massif. Type section: of the formation is about 15–20 m or more. In the northern Well-1 Stepnoe (331–439 m), drilled near the Nyzhni Peri-Black Sea Region the Borysfen Formation is divided Sirohozy locality of the Kherson region (Vereschagin, 1982; into two members. The Lower Borysfen Member consists Ryabokon, 2016; Figure 7). Reference section: Well 6-k of greenish-gray, gray silty sandy rocks with clay interbeds. (271.5–380 m) drilled near the Nyzhni Sirohozy locality of The thickness of the Lower Member is up to 50–60 m. In the Kherson region (Veselov et al., 1968; Ryabokon, 2016; the west of the region the Lower Member is composed of Figure 8). fine-grained sands and sandstones, with a thickness ranging The Borysfen Formation comprises greenish-gray, from 30–40 m to 90 m. The Lower Member in the south dark-gray (with a greenish tint due to glauconite content) of the northern Peri-Black Sea Region comprises dark-gray, silty clayey rocks (Figures 9 and 10). The thickness of the greenish-gray clays, noncalcareous and sometimes silty, formation is up to 270 m, but decreasing to the north to which are similar to the clays of the Planorbella Formation less than 70 m. In the south of the Ukrainian Shield, of the Crimean Plain. Here the thickness of the Lower within the Nikopol Manganese Ore basin, the Borysfen Member is up to 120 m. The Upper Borysfen Member is 175
VERNYHOROVA and RYABOKON / Turkish J Earth Sci Figure 5. Section of Well-2, Kochergino village of the Bakhchisaray district in Crimea (compiled based on Kraeva, 1972; Andreeva- Grigorovitch, 1980; Nosovskiy et al., 1984; Kraeva and Lulyeva, 1985; unpublished materials of Ye.Ya. Kraeva and M.F. Nosovskiy). composed of greenish-gray and dark-gray clays and in compta Goldf., Pterolucina batalpaschinica (Korob.), the upper part of the section sandy and silty clays. In the Scalaricardita tuberculata (Munst.); lower Oligocene south the thickness of the Upper Member is up to 200 m. ostracods association Disopontocypris oligocaenica (Zal.), The Borysfen Formation conformably overlies the Eocene Cuneocythere marginata (Bosq.), Cytherella beyrichi Alma, Barmashovo, and Shabo Formations in the northern (Reuss), Lineocypris majkopiensis Sсher.; diatoms of Peri-Black Sea Region. However, the formation has a Oligocene zone Pyxilla reticulata; and two spore and pollen disconformity with the top of the middle and upper Eocene assemblages, namely a lower complex with Taxodium successions on the basin margins. The formation is overlain distichiformis and upper one with Taxodium distichiformis, conformably by the Molochna Formation (Figure 2). Carya ovataeformis, and Quercus memoranda. The biostratigraphy of the Borysfen Formation (see The Rupelian age of the Borysfen Formation was references in Ryabokon, 2016; Figure 11) is characterized established based on mollusks, the zonal association by benthic foraminifera of the Rupelian provincial zone of plankton and benthic foraminifera, calcareous Spiroplectammina oligocenica of the Eastern Paratethys; nannofossils, dinoflagellate cysts, ostracods, and spore Rupelian association of plankton foraminifera Globigerina and pollen assemblages (Figures 2 and 8). The formation officinalis Subb., G. ouachitaensis ouachitaensis (Howe corresponds to the Planorbellian stage of southern Ukraine & Wall.), G. ouachitaensis gnaucki (Blow & Bann.), (Figure 2). G. cipepoensis Bolli, T. angustiumbilicata (Bolli), and 4.1.1.3. Indol Formation others; dinoflagellate cysts associations of Rupelian zones The name is taken from the Mokryi Indol River in Phthanоperidinium amoenum/Wetzeliella symmetrica the Crimean Peninsula (Maimin, 1951). Menner et al. and Wetzeliella gochtii; the NP 22 zone; Rupelian (1947) distinguished these deposits as clays with casts of assemblage of mollusks with Nucula (Lamellinucula) Planorbella sp. in the Mokryi Indol River section. Based on 176
VERNYHOROVA and RYABOKON / Turkish J Earth Sci Figure 6. Biostratigraphic subdivision of the Oligocene-lower Miocene deposits of the Crimean Peninsula. the study of the mollusk assemblage of these clays, Maimin Nuculana perovalis (Koen.), Bathiarca saxonica Koen., and Korobkov (1946) concluded that these deposits are Corbula conglobata Koen., Dacridium pygmeum Phill., analogous to the Khadum beds of the Ciscaucasia and Abra bosqueti Semp., Pleurotoma odontella Edw., and the Kharkov stage of the Ukraine. The Indol Formation Pl. laticlavia Beyrich. (Maimin and Korobkov, 1946; is widespread on the eastern Crimean Plain and adjacent Maimin, 1951); Oligocene plankton foraminifera part of the Crimean foothills. Type section: outcrop on the Globigerina officinalis Subb., G. praebulloides Blow., Mokryi Indol River (Maimin, 1951; Syabryai, 1963). G. praemicra Bolli, Tenuitella brevispira (Subb.), and The Indol Formation comprises gray, dark-gray, T. munda (Jenkins), T. angustiumbilicata (Bolli) and sometimes brown sandy clays, with thin interbeds of benthic foraminifera Haplophragmoides rotundidorsatus sands, aleurolites, and siderites. The formation thickness (Hantk.), Cyclammina constrictimargo (R.E. & K.C. varies from 80–100 m to 350 m. The Indol Formation Stewart), Spiroplectammina oligocenica J.Nikitina, conformably overlies the upper Eocene Alma Formation Caucasina schischkinskayae (Samoil.), Uvigerinella but it has an erosional disconformity with the underlying californica Cushm., and others (unpublished data, middle Eocene or upper Paleocene units on relatively L.M. Holubnichaia and L.G. Mintuzova); also known are uplifted areas in the basin. The upper boundary of the radiolarians, fish remains, and pteropods. formation is marked by the appearance of calcareous clays A Rupelian age was assigned to the Indol Formation with ostracods of the Azamat Formation. based on its mollusk and foraminifera content (Figures The biostratigraphy of the Indol Formation (Figure 2, 6, 8, and 12). The formation corresponds to the 6) includes the Rupelian mollusk assemblage of Planorbellian stage of southern Ukraine (Figure 2). 177
VERNYHOROVA and RYABOKON / Turkish J Earth Sci Figure 7. Section of Stepnoe-1 well drilled near the Nyzhni Sirohozy locality of Kherson region (composed based on Kraeva, 1973; Kraeva and Yartseva, 1973; materials of Ye.Ya. Kraeva, M.V. Yartseva, and M.F. Nosovskiy; and our own materials of geological mapping of the L-36-XI “Vesele” sheet). 4.1.1.4. Eastern-Kerch Formation deep-water deposits of the Kerch Peninsula and it is The name is taken after the area of distribution in the widespread not only onshore but locally also on the nearby eastern Kerch Peninsula (Vernyhorova and Ryabokon, Kerch Shelf (Figure 12). Type section: Well Kolodiazna-1 2018). The formation is composed of the Planorbellian (2920–3373 m), drilled near the Marfovka locality of the 178
VERNYHOROVA and RYABOKON / Turkish J Earth Sci Figure 8. Geological profile from the northern Peri-Black Sea Region to the Crimean Plain. Lenino district, Kerch Peninsula. Reference sections: Well Korenkivska-1 (3904–4853 m), drilled on the Cape Kop-Talile and Well Batalna-1 (2600–3180 m), drilled to the NE of the Primorskoe village on the Kerch Peninsula (Vernyhorova and Ryabokon, 2018; Figure 12). The formation comprises dark-gray, black, brownish- gray argillites, argillite-like clays, noncalcareous, irregularly silty, with rare very thin interbeds of light-gray aleurolites, with thin interbeds of siderites. The Eastern- Kerch Formation is subdivided into two members. The Lower Member is represented by the irregular alternation of argillite-like clays, thin layers of aleurolite and quartzy, glauconite-quartz sandstones. The Upper Member is composed of dark-gray and black argillites, argillite-like clays, with rare, very thin interbeds of light-gray aleurolites. The Eastern-Kerch Formation has a thickness of up to 700–915 m but to the west it decreases to 350–450 m. Figure 9. The Borysfen Formation in the eastern part of northern The Eastern-Kerch Formation has an overall transgressive Peri-Black Sea Region, Well 9, Tymoshivka village (141–183 m). character, with erosion at its base on the basin perimeter with respect to the underlying Eocene sediments. The formation has a conformable, gradual transition to the 179
VERNYHOROVA and RYABOKON / Turkish J Earth Sci Figure 10. Section of Well 9, Tymoshivka village of the Mykhailivka district of the Zaporizhzhia region (composed based on our own materials of geological mapping of the sheet L-36-XII “Melitopol”). overlying Kop-Takil Strata and the Azamat Formation The Rupelian age of the Eastern-Kerch Formation is (Figure 2). proven by foraminifera (Figures 2 and 13). The formation The biostratigraphy of the Eastern-Kerch Formation corresponds to the Planorbellian stage of southern (see references in Vernyhorova and Ryabokon, 2018; Ukraine. Figure 13) includes an Oligocene plankton foraminifera 4.1.1.5. Diurmen Beds assemblage with Globigerina officinalis; benthic The name is taken from Diurmen Mountain on the Kerch foraminifera association with Caucasina schischkinskayae Peninsula and it was V.V. Menner (Maimin, 1951) who (Sam.) and Bolivina mississippiensis Cushm.; Paleogene first described these deposits as the Diurmen Beds as part dinoflagellate cysts Deflandrea phosphoritica Eis. and of the Khadumian horizon of the Maikop Formation in the Wetzeliella articulata Wetz., identified in the Upper SW Kerch Peninsula. The Diurmen Beds can be found in Member on the Near-Kerch shelf of the Black sea; and two isolated sections on the anticlinal limbs in the central part Early Oligocene spore and pollen assemblages, namely of the Kerch Peninsula (Figure 12). Type section: outcrop a lower one with Taxodiaceae – Fagaceae – Palmae and of the Cape Karanhat on the south of Kerch Peninsula upper one with Pinaceae – Betulaceae – Juglandaceae. (Maimin, 1951). From the Upper Member of the Eastern-Kerch Formation The Diurmen Beds are composed of alternation of only rare plankton foraminifera Turborotalia permicra gray, brownish-gray silty clays, sandstones, and aleurolites. (Blow & Banner) and Globigerina ex gr. trefa (N.Byk.) (? The thickness of the clay beds is from 2 m to 12–25 m. Tenuitella munda (Jenkins)) are known. The sandstones are quartz-rich, feldspathic, rarely with 180
VERNYHOROVA and RYABOKON / Turkish J Earth Sci Figure 11. Biostratigraphic subdivision of the Oligocene-lower Miocene deposits of the northern Peri-Black Sea Region in southern Ukraine. glauconite, fine-grained, inequigranular, occasionally adolphina (Orb.), Dentalina multilineata Born., Nodosaria conglomeratic, obliquely laminated, with ripple marks calomorpha Reuss, Cibicidina amphisyliensis (Andr.), and plant detritus. The thicknesses of the sandstone layers Caucasina sp., Uvigerinella californica parva Cushm. and aleurolites range from 0.3 m to 2–3 m and more. For & Kleinp., Caucasina schischkinskayae (Sam.), Bolivina the Diurmen Beds on the peninsula, alternating clays and compta carinata Chal., B. bottgeri maraginica Chal., rare sandstones, with a thickness of 3–10 m to 20–30 m, are planktonic foraminifera Globigerina officinalis Subb., very characteristic. The formation thickness varies from Turborotalia permicra (Blow & Banner), and Tenuitella 60–80 m to 110–240 m. The Diurmen Beds Formation has angustiumbilicata (Bolli); and calcareous nannofossils of an erosional contact with the underlying Eocene and older zone NP 21 (Figures 2 and 13). sediments. Upward in the section and along the strike, The early Rupelian age of the Diurmen Beds is these beds are gradually replaced by the clay rocks of the constrained by foraminifera and calcareous nannofossil East Kerch Formation. data. The beds correspond to the lower part of the Fossils in the Diurmen Beds are rare (see references in Planorbellian of southern Ukraine (Figure 2). Vernyhorova and Ryabokon, 2018). Based on the studies 4.1.2. Oligocene, Rupelian Stage. Molochnian regional of V.F. Kozyreva, E.Ya. Kraeva, and L.M. Holubnichaia, stage of southern Ukraine the Diurmen Beds are characterized by the benthic 4.1.2.1. Molochna Formation foraminifera assemblage of Hyperammina sp., Dorothia The name is taken from the Molochna River in the east sp., Glomospira corona Cushm. & Jarv., Siphonodosaria of the northern Peri-Black Sea Region (Zosimovich et 181
VERNYHOROVA and RYABOKON / Turkish J Earth Sci Figure 12. Geological profile from the Chonhar Peninsula to the Kerch Peninsula. 182
VERNYHOROVA and RYABOKON / Turkish J Earth Sci Figure 13. Biostratigraphic subdivision of the Oligocene-lower Miocene deposits of the Kerch Peninsula. al., 1963). M.M. Kliushnikov (1952) was the first who The biostratigraphy of the Molochna Formation (see described the member of calcareous clays with ostracods references in Ryabokon, 2016) (Figure 11) includes the in the Molochna River basin. M.F. Nosovskiy (Zosimovich Oligocene assemblage of brackish mollusks Ergenika et al., 1963) distinguished these deposits as the Molochna cimlanica (Zhizh.) Popov, Janschinella garetzkii Merkl., and Beds. The Molochna Formation is widespread in the J. vinogrodskii Merkl.; ostracod association of the Rupelian northern Peri-Black Sea Region and adjacent part of interregional zone Disopontocypris oligocaenica of the Eastern the Near-Azov Massif and is the type formation of the Paratethys; endemic calcareous nannofossils association with Molochnian regional stage of southern Ukraine (Figure mass occurrence of Reticulofenestra ornata, Transversopontis 7). Type section: Well-1 Stepnoe (315.5–331.3 m) drilled fibula, nonnumerous Braarudosphaera bigelowi, Orthozugus near the Nyzhni Sirohozy locality of Kherson region aureus, and very rare Sphenolithus distentus, which (Vereschagin, 1982; Ryabokon, 2016). Reference section: corresponds to the NP 23 nanozone; dinoflagellate cysts Well 6-k (271.25–256.4 m) drilled at the Nyzhni Sirohozy association of beds with Hystrichokolpoma spp. considered locality of Kherson region (Veselov et al., 1968; Figure 8). as part of the Rupelian zone Wetzeliella gochtii; and spore The Molochna Formation comprises light-gray and and pollen assemblage of beds with Pinus cristata, Quercus greenish-gray silty clays with ostracods. To the south its porrectus, and Juglans compacta. thickness increases from 3–10 m to 40 m (Figures 10 and The Rupelian age of the Molochna Formation was 14). The Molochna Formation conformably overlies the determined by mollusks, ostracods of zone Disopontocypris Borysfen Formation and it is overlain by the Sirohozy oligocaenica, NP 23 Sphenolithus predistentus zone, and the Formation (Figure 2). dinocysts zone Wetzeliella gochtii (Figures 2 and 11). 183
VERNYHOROVA and RYABOKON / Turkish J Earth Sci The biostratigraphy of the Azamat Formation (see references in Vernyhorova and Ryabokon, 2018; Figures 6 and 13) includes the ostracod assemblage of the Rupelian interregional zone Disopontocypris oligocaenica; calcareous nannofossils association of beds with Reticulofenestra ornata, corresponding to the NP 23 zone; mollusks Ergenica cimlanica (Zhizh.), Hydrobia sp., Cardium sp., and Corbula sp.; and Tsymlan spore and pollen assemblage. The Rupelian age of the Azamat Formation is proven by the ostracod assemblage of zone Disopontocypris oligocaenica and the NP 23 zone (Figures 2, 6, and 13). The formation corresponds to the Molochnian stage of southern Ukraine (Figure 8). 4.1.2.3. Kop-Takil Strata Figure 14. The Molochna Formation in the eastern part of the The name is taken after Cape Kop-Takil located on the northern Peri-Black Sea Region, Well 9, Tymoshivka village SE Kerch Peninsula (Vernyhorova and Ryabokon, 2018). (134–141 m). The formation is composed of Molochnian deep-water deposits located on the eastern part of the Kerch Peninsula and locally on the peri-Kerch shelf of the Black Sea. Type 4.1.2.2. Azamat Formation section: Well Korenkivska-1 (3487–3904 m) drilled on The name is taken from the Azamat ravine near the the Cape Kop-Takil (Vernyhorova and Ryabokon, 2018; village of Azamat (now Malinovka village) in the Figure 12). Belohorsk district, Crimea. Maimin (1951) was the first The Kop-Takil Strata comprises gray, dark-gray, who distinguished the Azamat (Ostracoda) horizon in black argillites, argillitic clays, noncalcareous, sometimes the lower part of the Maikop Formation of the Crimea. with slightly calcareous intervals, with thin to very thin M.F. Nosovskiy (Grossgeym and Korobkov, 1975) aleurolite interbeds. The lower and upper boundaries of the proposed to merge the Molochna horizon deposits in Kop-Takil Strata are conjectural (Figure 2). The thickness the Crimea with the Azamat Formation. The Azamat of the Kop-Takil Strata is up to 400–540 m or more. Formation is widespread on the Crimean Peninsula, the Paleontological data on the Kop-Takil Strata are NW shelf of the Black Sea, and the central part of the too poor to assign a reliable age for this unit. Only Kerch Peninsula (Figures 4 and 12). Type section: outcrop sporadic pollen Acer sp., Alnus sp., Corylus sp., Ulmus of the Azamat ravine on the Kuchuk-Karasu River near sp., and Ephedra sp. and tests of benthic foraminifera Malynivka village of Belohorsk district, Crimea (Maimin, Ammonia becarii (L.), Quinqueloculina sp., Nonion sp., 1951; Syabryai, 1963). Reference section: outcrop of Cape gastropods, and ostracods were observed in these deposits Karanhat on the south of Kerch Peninsula (Maimin, 1951; (Vernyhorova and Ryabokon, 2018). Syabryai, 1963). Based on the stratigraphic position in the section of The Azamat Formation comprises light-gray, the Kerch Peninsula, the Kop-Takil Strata is correlated provisionally with the Molochnian stage of southern greenish-gray, yellowish-brown calcareous clays, Ukraine (Figures 2 and 12). aleurolites and argillitic clays with thin siderite interbeds. There are interlayers of clays with ostracods. To the east 4.1.3. Rupelian–Chattian Stages, Kerleutian regional of the Kerch Peninsula, clays become darker gray, weakly stage of southern Ukraine calcareous in character with thin interbeds of sandstones 4.1.3.1. Kerleut Formation and aleurolites. In the NE part of the Crimean Plain the The name is taken after the ancient village of Kerleut on clays are sandier. The thickness of the Azamat Formation the Kerch Peninsula (Maimin, 1951). These deposits were varies from 40–50 m to 80–100 m in the Crimean Plain, first described by V.V. Menner in 1933 as the Kerleut increasing in the basinal areas to 200–300 m. In the Kerch horizon of the middle part of the Maikop Formation in the Peninsula it is up to 380–410 m. The lower boundary of Kerch Peninsula (Maimin, 1951). The Kerleut Formation the Azamat Formation with the Planorbella, Indol, and is widespread on the Crimean Plain, the NW shelf of the Eastern-Kerch Formations is transitional and it is marked Black Sea, and the central part of the Kerch Peninsula and by increasing carbonate content and by the appearance of it is a type formation of the Kerleutian regional stage of ostracods. The formation is conformably overlain by the southern Ukraine. Type section: Well 15-r (740–1203 m) noncalcareous clays of the Kerleut Formation (Figure 2). drilled in the Kerleut area (Vernyhorova and Ryabokon, 184
VERNYHOROVA and RYABOKON / Turkish J Earth Sci Figure 15. Section of Well 1, Vladislavovka village of the Kirov district, Crimea (compiled after data of V.F. Kozyreva, 1949). 185
VERNYHOROVA and RYABOKON / Turkish J Earth Sci the Crimean Plain the thickness of the Lower Member is 100–130 m, increasing to 200–250 m to the east. In the Kerch Peninsula the typical thickness of the Lower Kerleut Member is up to 340–600 m, in some places even up to 700–810 m. The Upper Kerleut Member comprises silty clays with frequent beds of sandy clays or clayey sands, occasionally with interbeds of quartz-rich, glauconitic, fine-grained to medium-grained sandstones. The thickness of the sandy beds ranges from 0.5 m to 3 m. The Upper Kerleut Member has a thickness of up to 450–650 m in the Kerch Peninsula, increasing to 820–1200 m in local basins. In the Crimean Plain the thickness is up to 400–450 m. The lower boundary of the Kerleut Formation with the Azamat Formation is a conformable one and it is marked by the disappearance of Figure 16. The lower member of the Kerleut Formation on the calcareous lithologies and ostracods. The upper boundary southern part of the Kerch Peninsula, in the western part of Cape with the Arabatska Formation is more transitional. In the Chauda (Akbulat Oba structure). Kerch Peninsula it is defined by changing the foraminiferal assemblage with Haplophragmoides kerleuticus Kozir. to an assemblage with H. periferoexcavatus Subb. and 2018). Reference section: Well 1-r (1080–1300 m) Caucasinella elongata (Orb.) of the Upper Maikop. drilled on the Vladislavovka area in the Kerch Peninsula The biostratigraphic character of Lower Kerleut (Vernyhorova and Ryabokon, 2018; Figure 15). Member of the Kerleut Formation (see references in The Kerleut Formation comprises gray, dark-gray with Vernyhorova and Ryabokon, 2018; Figure 13) includes brownish tint clays, noncalcareous, with silty or sandy numerous fish remains and also sponge spicules and intervals, very thin interbeds of gray aleurolite or fine- radiolarians; a lower Oligocene dinoflagellate cysts grained sands, interbeds and nodules of siderites (Figures association with Wetzeliella symmetrica Weil., W. articulata 16 and 17). Thickness of the Kerleut Formation in the (Wetzel) Eis., W. gochtii Costa & Dow., Rhombodinium Kerch Peninsula is up to 860–1100 m, in places even up draco Gocht, R. longimanum Vozzh., Hystrichokolpoma to 1500 m. salacia Eaton, Melitasphaeridium asterium (Eaton) Bujak, The Kerleut Formation is divided into two members. and Phthanoperidinium amoenum Drugg & Loeblich Jr. The boundary between the Lower and Upper members The Upper Kerleut Member is characterized by benthic is defined by the appearance of the foraminifera with foraminifera beds with Haplophragmoides kerleuticus Haplophragmoides kerleuticus Kozir. The Lower Kerleut Kosir. and beds with Spiroplectammina caucasica Djan., Member is composed of clays, sometimes with silty or Uvigerinella californica Cushm., and Bolivina goudkoffi sandy intervals and siderites nodules (Maimin, 1951). In Rankin in the Kerch Peninsula; beds with S. caucasica Figure 17. The upper member of the Kerleut Formation on Cape Chauda of the Kerch Peninsula. 186
VERNYHOROVA and RYABOKON / Turkish J Earth Sci (232.7–315.5 m) drilled near Nyzhni Sirohozy locality of the Kherson region (Vereschagin, 1982; Ryabokon, 2016; Figure 7). Reference section: Well 6-k (182.7–256.4 m) drilled near Nyzhni Sirohozy locality of Kherson region (Veselov et al., 1968; Ryabokon, 2016; Figure 8). The Sirohozy Formation comprises gray, light-gray clayey silty sandy rocks with thicknesses of up to 100 m (Figures 10 and 18). To the south the formation becomes clayey and its thickness increases up to 220 m. On the basin perimeters the formation has more sands and silts with glauconite with a thickness between 2–10 m and 40– 60 m. The Sirohozy Formation conformably overlies the Molochna Formation (Figure 2). The upper boundary with the Askaniia Formation is transitional and it is defined by the appearance of a normal salinity mollusk assemblage Figure 18. The Sirohozy Formation in the eastern part of the and the foraminifera association of the Sphaeroidina northern Peri-Black Sea Region, Well 9, Tymoshivka village variabilis zone. (109–134 m). The biostratigraphy of the Sirohozy Formation (see references in Ryabokon, 2016; Figure 11) includes an Oligocene mollusk assemblage with Lenticorbula sokolovi Djan., U. californica Cushm., and B. goudkoffi Rankin, (Karl.); an ostracod association similar to that of the beds with Cribrononion onerosum (Bogd.), Nonion Molochna Formation (in the lower part of the Sirohozy polymorphus Bogd., and Globulina gibba Orb., and beds Formation section); a dinoflagellate cysts assemblage of with Spiroplectammina terekensis Bogd. and U. californica the Oligocene zone DP 14 Chiropteridium galea; and a Cushman in the Indol area of the Crimean Plain; beds spore and pollen assemblage of beds with Pinus cristata, with S. terekensis Bogd., U. californica Cushm., and Quercus porrectus, and Juglans compacta. C. schischkinskayae (Sam.) in the NE part of the Crimean Based on its stratigraphic position in the section and Plain; occasional Oligocene plankton foraminifera such also proven by mollusks, dinoflagellate cysts, ostracods, as Globigerina ciperoensis Bolli, G. cf. officinalis Subb., spores, and pollen, the Sirohozy Formation is dated as late and Dipsidripellа ex gr. danvillensis Howe & Wall., known Rupelian–early Chattian in age and it corresponds to the from beds with S. caucasica Djan., S. terekensis Bogd., and lower part of the Kerleutian stage of southern Ukraine B. goudkoffi Rankin in the Kerch Peninsula; an Oligocene (Figures 2 and 8). dinoflagellate cysts association, corresponding to the 4.1.3.3. Askaniia Formation middle part of zone DP14 Chiropteridium galea; a Middle The name is derived from the Askaniia-Nova locality of Maikop spore and pollen assemblage; and an Oligocene the Kherson region (Veselov and Nosovskiy, 1962). These mollusk such as Nucula compta Goldf. authors distinguished these deposits as the Askaniia beds A late Rupelian–Chattian age was assigned to the Kerleut by finding a stenohaline mollusk assemblage in the Upper Formation based on the dinoflagellate cysts, plankton and Oligocene section of the northern Peri-Black Sea Region. benthic foraminifera, and spore and pollen assemblages The Askaniia Formation is widespread in the northern (Figures 2 and 13). The Chattian age of the Upper Kerleut Peri-Black Sea Region and it can be found locally in the Member is proven by the dinocysts assemblage zone Syvash region of the Crimean Plain (Figure 8). Type DP 14 Chiropteridium galea and planktonic foraminifera. section: Well-1 Stepnoe (164.7–232.7 m) drilled near the The Kerleut Formation is correlated with the Sirohozy, Nyzhni Sirohozy locality of Kherson region (Vereschagin, Askaniia, and Hornostaivka Formations of the northern 1982; Ryabokon, 2016; Figure 7). Reference sections: Well Peri-Black Sea Region (Figures 2, 8, and 12). 6-k (157.7–182.7 m) drilled near the Nyzhni Sirohozy 4.1.3.2. Sirohozy Formation locality of Kherson region (Veselov et al., 1968; Ryabokon, The name is taken after the Nyzhni Sirohozy locality of 2016), Well-1 (411–539 m) drilled near the Svobodnyi the Kherson region (Nosovskiy, 1970). Nosovskiy (1962) Port village of the Kherson region (Kraeva et al., 1966). distinguished these deposits as beds with Corbula fauna The Askaniia Formation comprises gray, greenish-gray overlying the beds with Ostracoda (Nosovskiy and silty clays, sometimes sandy, with clayey silt (aleurolite) Savenko, 1963). The Sirohozy Formation is widespread in intervals (Figures 10 and 19). The thickness of the Askaniia the northern Peri-Black Sea Region and also in the adjacent Formation varies from 20–95 m to 160 m and increases up parts of the Azov Massif. Type section: Well-1 Stepnoe to 240 m in the south. The lower boundary of the Askaniia 187
VERNYHOROVA and RYABOKON / Turkish J Earth Sci 4.1.3.4. Hornostaivka Formation The name is taken from the Hornostaivka locality of the Kherson region (Nosovskiy and Pasichnyi, 1965). The formation was first distinguished by Nosovskiy and Pasichnyi (1965) as silty-clay rocks overlying the Askaniia clays in the Maikop section of the northern Peri-Black Sea Region. The Hornostaivka Formation is widespread on the southern part of our study area and it can be found locally in the Syvash region of the Crimean Plain as well (Figure 8). A type section for this formation has not been specified to date. The Hornostaivka Formation comprises greenish- gray noncalcareous silty clays, clayey silts, and sands. In the deepest part of the Peri-Black Sea Region basin the lower part of the formation is composed of sandy Figure 19. The Askaniia Formation in the eastern part of the silty clays. The upper part of the formation consists of northern Peri-Black Sea Region, Well 9, Tymoshivka village (99–110 m). aleurolites and sandstones with silty clay intervals. To the north these deposits pass into quartz and glauconitic- quartz sandstones and aleurolites, while the lower part of the formation consists of silty clays with sandstone and Formation with the Sirohozy Formation is marked by the aleurolite interbeds. The thickness of the Hornostaivka appearance of a stenohaline mollusk assemblage and the Formation in the northern Peri-Black Sea Region is up to foraminifera association of zone Sphaeroinina variabilis. 140 m and in the Crimean Plain it increases to 350–400 m. The upper boundary with the Hornostaivka Formation is The lower boundary of the Hornostaivka Formation with defined by the appearance of a “nonionids” foraminifera the Askaniia Formation is defined by the appearance of assemblage. On the basin perimeter, the Askaniia a “nonionids” foraminifera assemblage. The boundary of Formation is disconformably overlain by the Mayachka the Hornostaivka Formation with the Chornobaivka and Formation and younger Miocene sediments (Figure 2). Arabatska Formation is defined using foraminifera (Figure The biostratigraphy of the Askaniia Formation (see 20). references in Ryabokon, 2016) (Figure 11) includes The biostratigraphy of the Hornostaivka Formation a Chattian mollusk assemblage with Plagiocardium (see references in Ryabokon, 2016; Figure 11) includes a abundans Liv and Chlamys bifida (Munst.); upper dinoflagellate cysts association of beds with Homotryblium Oligocene benthic foraminifera provincial zone floripes of Oligocene zone DP 14 Chiropteridium galea. Sphaeroidina variabilis; Oligocene ostracod assemblage The lower part of the formation is characterized by with Cytherella beyrichi (Reuss), C. gracilis Lnkl., a benthic foraminiferal assemblage with Cibicidoides and Disopontocypris oligocenica Zal.; dinoflagellate ornatus (Bogd.) and Cribrononion onerosum (Bogd.), cysts association of subzone Rhombodinium draco of better known as a “nonionid complex”. In the south, the Oligocene zone DP 14 Chiropteridium galea, correlating uppermost part of the formation is characterized by beds with Spiroplectammina caucasica Djan. and Uvigerinella with dinoflagellate zone D15c of the Chattian Stage of californica Cushm. The lower part of the formation is also northwestern Europe; association of Oligocene plankton characterized by a mollusk assemblage with Cerastoderma foraminifera Globigerina praebulloides praebulloides Blow, prigorovskii (Bog.), Plagiocardium abundans (Liv.), and G. praebulloides leroyi Blow & Bann., G. ciperoensis Bolli, Corbula helmerseni (Iljina), known from the upper part G. ouachitaensis gnaucki (Blow & Bann.), G. ouachitaensis of the Kalmykian regiostage of the Eastern Paratethys; ouachitaensis (Howe & Wall.), G. senilis Bandy, Tenuitella association of ostracods Pontocypris brevis Lnkl., angustiumbilicata (Bolli), and Globigerinella obesa (Bolli); Pterygocythereis jonesii (Baird.), P. fimbriata fimbriata and a spore and pollen assemblage with dominating (Munst.), Cytheridea pernota Oertli & Keij., Trachyleberis Taxodiaceae, Pinus, and less numerous Tsuga, Picea, variatuberosa Sher., and Echinocythereis hirstula (Lnkl.), Cedrus, Sciadopitys, and Podocarpus. most of which are known from the Chattian Stage of The Chattian age of the Askaniia Formation is proven the Western Europe; and a spore and pollen assemblage by dinoflagellate cysts, foraminifera, and mollusks (Figures similar to that of the Askaniia Formation. 2 and 8). The formation corresponds to the Kerleutian The Chattian age of the Hornostaivka Formation of the stage of southern Ukraine. northern Peri-Black Sea Region is proven by dinoflagellate 188
VERNYHOROVA and RYABOKON / Turkish J Earth Sci Figure 20. Section of Well 692 and 697 on the Chonhar Peninsula (compiled based on Didkovskiy and Kulichenko, 1975; Kraeva and Lulyeva, 1985; Nosovskiy, 1992; Nosovskiy, 1993b; materials of M.F. Nosovskiy and Ye.Ya. Kraeva). 189