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The Berriasian Tirnovella occitanica Zone in the Area (Eastern )

Article in Moscow University Geology Bulletin · March 2019 DOI: 10.3103/S0145875219020029

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Baraboshkin Evgeny Arkadiev Vladimir Lomonosov Moscow State University Saint Petersburg State University

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The user has requested enhancement of the downloaded file. ISSN 0145-8752, Moscow University Geology Bulletin, 2019, Vol. 74, No. 2, pp. 143–153. © Allerton Press, Inc., 2019. Russian Text © The Author(s), 2019, published in Vestnik Moskovskogo Universiteta, Seriya 4: Geologiya, 2019, No. 1, pp. 26–37.

The Berriasian Tirnovella occitanica Zone in the Feodosia Area (Eastern Crimea) E. Yu. Baraboshkina, *, V. V. Arkadievb, **, A. Yu. Guzhikovc, ***, and E. E. Baraboshkind, **** aDepartment of Geology, Moscow State University, Moscow, 119234 bInstitute of Earth Sciences, St. Petersburg State University, St. Petersburg, 199034 Russia cDepartment of Geology, Saratov State University, Saratov, 410012 Russia dIntegrated Center for Hydrocarbon Recovery, Skolkovo Institute of Science and Technology, Moscow, 1212015 Russia *e-mail: [email protected] **e-mail: [email protected] ***e-mail: [email protected] ****e-mail: [email protected] Received May 21, 2018; revised May 21, 2018; accepted May 22, 2018

Abstract—The occurrence of the Tirnovella occitanica Ammonite Zone in the Berriasian section of Feodosia was confirmed here for the first time. The results of sedimentological, bio-, and magnetostratigraphic study of this interval are discussed.

Keywords: ammonites, Tirnovella occitanica, ichnofossils, Berriasian, biostratigraphy, magnetostratigraphy, petromagnetism, sedimentology, Feodosia, Eastern Crimea DOI: 10.3103/S0145875219020029

INTRODUCTION fore well exposed. The rocks are highly dislocated: the dip azimuth varies from 42° to 172°, the dip angle is In 1893 O.F. Retowski (Retowski, 1893) described from 10° to 50°. Ten units with an observed thickness numerous specimens of Hoplites occitanicus ammonites in the environs of Feodosia. However, the exact locality, of approximately 115 m (from bottom to top) are dis- as well as the stratigraphic position of this find, were tinguished in the section. All rocks are completely bio- unknown. T. N. Bogdanova, E.D. Kalacheva, and turbated and the primary structures are rarely pre- served. I.I. Sei [1999] described the genus Tirnovella occitanica (Pictet) and substantiated the occurrence of the Berri- Unit 1. Irregular alternation of completely biotur- asian Occitanica Zone in the Feodosia section based bated pale gray calcareous clays (up to 0.2–1.6 m; on the revision of Retowski’s collection; however, all Figs. 2, 3) and thick (up to 0.9 m) mudstone interbeds attempts to find Tirnovella occitanica in Eastern Crimea with aleuritic-size quartz admixture and tiny plant were unsuccessful. detritus (Fig. 2, 4). Mudstones are broken by numer- In the summer of 2016, E.Yu. Baraboshkin, ous thin cracks filled with block calcite. The unit con- E.E. Baraboshkin, T.A. Kulashova (Moscow State tains ichnofossils Alcyonidiopsis bavaricus Uchman University) and A.Yu. Guzhikov studied the section (figs. 2, 6), Chondrites isp., Planolites isp., Rhizocoral- of the Sultanovskaya Formation in the Zavodskaya lium commune Schmid (Fig. 2, 5); Thalassinoides sue- Balka quarry on the outskirts of the town of Feodosia vicus and partially pyritized wood residues. Ammo- (Figs. 1A, 1B). As a result, previously unknown strati- nites Euphylloceras sp., Ptychophylloceras sp. and rare graphic levels of the Sultanovskaya Formation charac- bivalves Nucula sp., Modiola sp. were found in the terized by ammonites were identified. Below, the lower part of the unit, and Tirnovella occitanica (Pic- description of the section along with its sedimentolog- tet) was found at the top of the thick mudstone bed ical (E.Yu. Baraboshkin and E.E. Baraboshkin) and (Fig. 3, 4–8), Protetragonites sp. and Berriasella priva- magnetostratigraphic (A.Yu. Guzhikov) interpreta- sensis (Pictet). The visible thickness is 5.2 m. tions, as well as the biostratigraphic substantiation of Unit 2. The frequent alternation of light gray bio- the Tirnovella occitanica Zone and its description turbated calcareous clays (0.4–1.4 m) and thin mud- (V.V. Arkadiev) are given. stone interbeds (0.1–0.3 m), similar to those described Structure of the section. The section is located on above. At the top are small pyrite nodules. The unit the southern side of the operating quarry and is there- contains abundant ichnofossils Chondrites isp., Plano-

143 144 BARABOSHKIN et al.

(b) Azov Sea m STAGE ZONE SUBZONE UNIT POLA- RITY 100 Val. 10 12/52 Feodosia 70 B. callisto

Sudak

Sevastopol Feodosia Nasypnoe Black Black Sea Sea 60 Zavodskaya Balka quarry (a) 2.6 km Riasanites crassicostatum

Sample Kr16-11/3 Sample Kr16-12/28 -12/28 Amphibole 1% Pyrite 1%

ms mica–

% % smectite 2% 3 2

50 % e e 2%

9 t t i iit %

a r t 0

c Zeolite 1% e c 1

i

d e i a

m c Siderite 3% Siderite

S mmect i o r S m d o y r ms mica– Chlorite 3% d Zeolite 1% HHydromic y smectite 6% HHydromica 10% Chlorite 2%

Calcite 58% Quartz 21% Calcite 42% Fauriella boissieriFauriella Plagioclase 6% Plagioc Quartz 29%

40 lase 3% lase (c) BERRIASIAN

4 123 67

30 euthymi Neocosmoceras 5 (d) 89

K, Jn, Jrs, K/Jrs, –5 –4 D, deg I, deg 10 , SI units 10–3 A/m Q A/m 10 m/A 0 100 200 300 –50 0 50 10 20 40 60 0 10 20 0 0.5 1.0 1.5 0 3 6 0 2 4 6 Paleomagnetic Paleomagnetic samples 3114/16 20 3114/15 3114/14 3114/13 3092/12 3092/11 3092/9, 10 3092/8 3092/7

3092/6 10 3114/5A 3092/5 3092/4 3114/3B Tirnovella occitanica Tirnovella 3114/3A 3092/3 3114/2C

123456789 3114/2B -11/5 3114/2A -11/3 3092/2 0 3092/1

Fig. 1. The Berriasian section in the Zavodskaya Balka section (Feodosia): а, locality scheme; b, structure of the section; c, composition of the clayey fraction of samples of Kr16-11/3 (Tirnovella occitanica Zone) and Kr16-11/3 (Fauriella boissieri Zone); d, magnetostratigraphic section of Tirnovella occitanica Zone: 1, grainstones, 2, mudstones, 3, calcareous clays, 4, Tirn- ovella occitanica, 5, finds of other ammonites, 6, pyrite nodules, 7, numbers of samples for X-ray phase analysis, 8–9, geomag- netic polarity: 8, normal (а, reliable; b, proposed), 9, reverse (a, reliable; b, proposed).

MOSCOW UNIVERSITY GEOLOGY BULLETIN Vol. 74 No. 2 2019 THE BERRIASIAN TIRNOVELLA OCCITANICA ZONE 145

QrQr ExEx ShSh F Q A ExEx

Q P A 1 ShSh 500500 m 2

C B

Q

500500 m 500500 m 3 4

5675 6 7

Fig. 2. 1, a view of the southwestern side of the quarry, arrow shows the bed with Tirnovella occitanica; thin-sections of represen- tative rocks: 2, thin section Kr16-12, grain–rudstone of mixed composition, parallel nicols; 3, thin section Kr16-11-3, calcareous clay, parallel nicols; 4, thin section Kr16-11-5, clayey mudstone, parallel nicols; letter designations: А, algae remains; В, biotur- bation; С, small phytodetritus; Ex, extraclasts; Р, peloids; Q, quartz; Qr, quartzite; Sh, schist; some ichnofossils: 5, Rhizocoral- lium commune Schmid, 1876 and Chondrites isp., Sample 127/11, 6, Alcyonidiopsis bavaricus Uchman, 1999, Sample 127/7; 7, Thalassinoides isp., Sample 127/13. Collections and images of E.Yu. Baraboshkin and E.E. Baraboshkin, 2015–2016. Scale bar, 1 cm. The collection is stored in the Earth Science Museum (MSU), no. 127. lites isp., Thalassinoides isp. In the upper part of the Unit 3. Dark gray bioturbated calcareous clays unit is a hiatus of undefined scale. The proposed (2.5–3 m) with small pyrite nodules at the top and thickness is 24–25 m. bottom of the unit. Clays alternate with rare interbeds

MOSCOW UNIVERSITY GEOLOGY BULLETIN Vol. 74 No. 2 2019 146 BARABOSHKIN et al.

12a2b3

5a 5b

4b 4a 1 cm

6b 6a

7a 7b 8

Fig. 3. Berriasella privasensis (Pictet): 1, Sample no. 6/130, lateral view; 2, Sample no. 7/130: 2а, lateral view, 2b, ventral view; 3, Sample no. 8/130: 3а, lateral view, 3b, ventral view; Tirnovella occitanica (Pictet): 4, Sample no. 2/130: 4а, lateral view, 4b, ven- tral view; 5, Sample no. 3/130: 5а, lateral view, 5b, ventral view; 6, Sample no. 5/130: 6а, lateral view, 6b, ventral view; 7, Sample no. 1/130: 7а, lateral view, 7b, ventral view; 8, Sample no. 4/130, lateral view; all samples are from Eastern Crimea, Feodosia, Zavodskaya Balka quarry, Berriasian, occitanica zone. Magnification, 1×.

MOSCOW UNIVERSITY GEOLOGY BULLETIN Vol. 74 No. 2 2019 THE BERRIASIAN TIRNOVELLA OCCITANICA ZONE 147 of light gray mudstones (0.25–0.3 m) and contain the cyclic change in the carbonate content. The ichno- same ichnofossil assemblage, as well as pyritized wood complex described in the section indicates that it residues. The thickness is 8 m. belongs the Cruziana ichnofacies of the open shelf Unit 4. Dark gray bioturbated calcareous clays with (Baraboshkin et al., 2016) and the predominance of var- small pyrite nodules at the top and bottom of the unit. ious “worms” (sipunculidus, polychaetes, etc.) among Ichnofossils such as Chondrites isp., Planolites isp., the macro- and meiobenthos of crustaceans. Thalassinoides isp. are common in the unit. The Finely dispersed phytodetritus and large plant frag- ammonites Ptychophylloceras sp., Protetragonites sp. ments are found in significant quantities. The role of and Neolissoceras sp. occur. In addition, finds of Chondrites increases upwards, which probably indi- Euthymiceras euthymi (Pictet), Fauriella cf. boissieri cates an increase in the level of disoxia in the sedi- (Pictet), Malbosiceras malbosi (Pictet) are noted (Ark- ment. This is directly confirmed by the appearance of adiev et al., 2010, 2015). The thickness is 8 m. pyrite nodules and a decrease in the number of ostra- Unit 5, similar to Unit 2. The thickness is 6.2 m. cods (Arkadiev et al., 2015) and is indirectly con- Unit 6. Alternation of dark gray bioturbated calcar- firmed by a change in the color of clays to dark gray. eous clays (0.2–0.3 m) and thick (0.4–1 m) mudstones. The composition of the fine fraction of rocks was The unit contains ichnofossils Chondrites isp., Plano- studied in two samples from the lower and middle lites isp., and Thalassinoides isp.; there are ammonites parts of the section (Cr16-11/3 and Cr16-12/28, zones of Euthymiceras sp. and “Berriasella” sp. ind. In the Occitanica and Boissieri, respectively) using X-ray upper part of the unit. The thickness is 8.4 m. phase analysis. According to the results, these zones Unit 7, similar to Unit 3. The thickness is 4.8 m. are similar (Fig. 1 B). The carbonate rocks (42–58%) are Unit 8, similar to Unit 6. The thickness is 2 m. composed mainly of hydromica (9–10%), mixed-layer Unit 9, similar to Unit 3. Rocks are intensively bio- minerals with packages of mica and smectite (2–6%) turbated by Chondrites isp.; At the bottom there are and chlorite (2–3%). There is a significant proportion abundant ammonites Riasanites crassicostatum of quartz admixture (21–29%) that is visible under a (Kvant. et Lys.), Riasanites sp. and remains of bivalves microscope (Fig. 2, 3, 4). Plagioclase and zeolites (Arkadiev et al., 2010, 2015). Thickness 40 m. occur in both samples; in sample Cr16-12/28 horn- Unit 10 blende (1%) is found. The joint occurrence of chlorite, is similar to the previous unit; however, hornblende, and zeolites may be due to their volcano- mudstone interbeds are even more rare. The unit, genic origin due to the precipitation of volcanic ash. which composes the roof of the quarry, is intensely The presence of volcanogenic material is confirmed deformed. Due to this, its structure is not quite clear. by the presence of superparamagnetic magnetite (Ark- The bottom of unit 10 is quite remarkable. It is drawn adiev et al., 2010; Guzhikov et al., 2014), as character- at the erosion base of a single 20-cm-thick debrite, istic of volcanic ash. The latter was originated appar- which is represented by poorly sorted grain-rudstone of ently from the Transcaucasian Region, which was mixed carbonate–terrigenous composition (Fig. 2, 2) characterized by volcanic activity at this period. consisting of angular grains of quartz, quartzites, crys- talline schists and shallow-water carbonate grains: The occurrence of the debrites in the upper part of extraclasts with remains of benthic foraminifera, echi- the section deserves special attention. The composi- noderms, calcareous algae, peloids and ooids. In the tion of the debris (including the presence of green section of debrite are mudstone intraclasts, which are algae and ooids) indicates the erosion of shallow-water concentrated in the lower and upper parts of the unit. carbonates and basement rocks or the redeposition of Berriasella callisto (d’Orb.) was found. This find products of their erosion (for example, conglomerates allowed us to distinguish the B. callisto subzone in the that occur in the sections of Mt. Agarmysh in the uppermost part of the Berriasian (Arkadiev et al., area). The age of this interval of the sec- 2017) for the first time. The visible thickness is more tion was assumed to be Valanginian (Arkadiev et al., than 9 m. 2010, 2015); however, the find of Berriasella callisto in Sedimentary conditions. The nature of the studied debrites that lie somewhat higher stratigraphically section, the intensity of bioturbation, and the complex more likely indicates their Late Berriasian age (Arka- of ichnofossils are very similar to those in the upper diev et al., 2017). This event corresponds to the phase part of the Lower Berriasian Feodosia marls, which of deformation in the central and southwestern parts are exposed at the St. Elias and Feodosia capes (Bara- of the Crimea (including in the Agarmysh area) pre- boshkin et al., 2016; Guzhikov et al., 2012). The fine- liminarily at the Berriasian–Valanginian boundary grained composition of the deposits, their complete (Baraboshkin, 2016). Due to this, the Late Berriasian bioturbation, and the absence of primary structures age is quite evident. suggest a moderate sedimentation rate under pelagic Thus, the deposits of Tirnovella occitanica Zone conditions. The offshore remoteness is also confirmed and the younger intervals of the Zavodskaya Balka by the occurrence of dinocyst assemblages (Arkadiev section were formed under deep-shelf conditions, at a et al., 2015). Along with this, the proportion of the clay distance from the marginal parts of the basin with an component increases from bottom to top, as well as a increasing level of disoxia, and against the background

MOSCOW UNIVERSITY GEOLOGY BULLETIN Vol. 74 No. 2 2019 148 BARABOSHKIN et al. of the input of ash material. Such a course of sedimen- subsequent measurements of the natural residual mag- tation was disturbed by the landslide of the debris flow netization (Jn). The laboratory petromagnetic and due to deformations at the Berriasian–Valanginian magneto-mineralogical studies included study of boundary. magnetic susceptibility (K), its anisotropy (AMS), and Biostratigraphy. The upper (Upper Berriasian– magnetic saturation experiments with subsequent Valanginian) part of the Sultanovskaya Formation of determinations of residual saturation magnetization the Zavodskaya Balka section has been studied in (Jrs) and remanent coercivity (Hcr), as well as differen- detail. As a result, it was possible to obtain detailed tial thermomagnetic analysis (DTM). bio- and magnetostratigraphic characteristics (Arka- The Königsberger parameter (factor Q) and the K/Jrs diev et al., 2010; 2015, 2017; Guzhikov et al., 2014). The ratio were calculated. The Jn parameter was measured data on the lower part of the section were fragmentary on a JR-6 spinner magnetometer and K was measured and incomplete. Ammonites of Dalmasiceras sp. were on a MFK-1FB multifrequency kappabridge. A TAF-2 found at the base of the section by V.V. Druchits. They fraction thermoanalyzer of fractions was used for characterize the middle levels of the Berriasian (Occi- DTMA. The component analysis was performed using tanica zone) (Arkadiev et al., 2012). At the bottom of the Remasoft 3.0 software and the AMS analysis was the section, T.N. Bogdanova found Retowskiceras performed using Anisoft 4.2 software. retowskyi Kvant. (Bogdanova et al., 1984), which made it Results of magnetostratigraphic studies. According possible to distinguish beds with Tirnovella occitanica to the petromagnetic and magnetomineralogical fea- and Retowskiceras retowskyi and the Dalmasiceras tauri- tures, the studied rock samples are similar to the pre- cum subzone in the Berriasian Stage section of the East- viously studied Upper Berriasian clays in the same ern Crimea (Arkadiev et al., 2012). quarry (Arkadiev et al., 2010; 2015; Guzhikov et al., New finds described below confirm the previous –5 2014): the average K values are 38 × 10 SI units, Jn conclusions. Among the ammonites that were found –3 (Fig. 3, 4, 7) are large forms (70–80 mm, in diameter) was 6.5 × 10 А/m, and Jrs was 2.3 А/m. Despite the ascribed to Tirnovella occitanica (Pictet). The preser- substantial variations in the petromagnetic parameters vation degree of ammonites and their dimensions sug- of the studied samples, there are no evident regulari- gest that the specimens of Hoplites occitanicus col- ties in their distribution throughout the section were lected by O.F. Retowski in the vicinity of Feodosia also revealed (Fig. 1). The same situation is characteristic originate from the area of modern Zavodskaya Balka. of the previously studied overlying deposits. The main Together with Tirnovella occitanica, specimens of Ber- mineral carrier of the natural magnetization is magne- tite, which is identified based on a decrease in magne- riasella privasensis (Pictet) were found (Fig. 3, 1–3). ° This ammonite assemblage characterizes the Occitan- tization at the Curie temperature of magnetite (578 С) ica Zone. It should be noted that all the boundaries of and the occurrence of a magnetically soft phase (Hcr = ammonite zones and subzones in this section were 38–44 mT), as is typical of thinly dispersed magnetite. conditionally distinguished, as the distribution of The magnetic susceptibility anisotropy (AMS) pattern zonal forms has not yet been determined throughout is similar to the typical sedimentary magnetic struc- the section. ture, where the short axes of magnetic ellipsoids (K3) are oriented vertically and projections of long and In addition, microfaunistic and palynological data average axes (K1 and K2, correspondingly) are at the were obtained for the newly discovered levels of the sec- edge of the stereogram. In this case, however, a dis- tion, which we plan to report in the next publication. tinct K1 ordering in the NW–SE direction is observed The magnetostratigraphy of the Upper Berriasian (Fig. 4А). Similar magnetic structures of clays caused (Boissieri Zone) and Berriasian–Valanginian bound- by collisional compression were described not only in ary intervals of the Zavodskaya Balka section, were the Zavodskaya Balka section, but also in other areas previously reported in (Arkadiev et al., 2010; 2015, of the Crimean mountains (Bagaeva and Guzhikov, 2017; Guzhikov et al., 2014). The paleomagnetic data 2014). Diagrams of the parameters L = K1/K2 and on the Mid-Berriasian interval of the section (Occi- F = K2/K3 (K2 are the middle axes of magnetic ellip- tanica Zone) that were obtained for the first time in soids) indicate the flattened shape of magnetic parti- 2016–2017 are presented below. cles (Fig. 4А), which is probably connected with the The method of magnetostratigraphic studies. The development of aggregates of submicron-size magne- oriented rock samples were collected at the 21st level tite grains on flakes of clayey minerals. (preliminarily every 1 m) in the lower part of the sec- We applied the methods that were previously used tion (units 1–2, Fig. 1). Each sample was subsequently for the interpretation of collections of Upper Berria- cut into 2–3 cubic samples with 2 cm edges. sian deposits from the Zavodskaya Balka section To distinguish the magnetization components, the (Arkadiev et al., 2010; 2015; Guzhikov et al., 2014): samples from each level were subjected to magnetic methods of paleomagnetic measurements, component cleaning with an alternating field in an LDA-3 AF unit analysis, and magnetopolar interpretation of results, (in the range from 5 to 50–80 mT) and temperature in including the substantiation of the ancient origin of Jn. an Aparin furnace (from 100° to 500–550°C) with As in the previous studies, the preference during the

MOSCOW UNIVERSITY GEOLOGY BULLETIN Vol. 74 No. 2 2019 THE BERRIASIAN TIRNOVELLA OCCITANICA ZONE 149

N TILT CORR (a) N = 18 L 1.106

270 90

1.000 1.106 F

180 N N Up (b) TILT CORR

–3 Jn/Jnmax Jn/Jnmax = 8.84e A/m 1 Sample 3092/01

W E W E W E

Scale interval = 1.50e–3 A/m 0 10 20 30 40 50 60 70 SDown S N N Up TILT CORR –3 180 Jn/Jnmax Jn/Jnmax = 3.65e A/m 1 Sample 3114/05A

W E W E W E

Scale interval = 666e–6 A/m 0 10 20 30 40 50 60 70

SDown 1 S 2 N N 3 (c) GEO TILT CORR 4 N = 31 N = 31 5 D = 135.7° D = 148.2° 6 ° I = –31.9 I = –48.0° 7 k = 4.99 k = 6.21 α = 12.9° α ° 95 95 = 11.3 8 270 90 270 90 9 10 11 12

13 180 180 Fig. 4. The results of petromagnetic and paleomagnetic analyses: а, anisotropy of magnetic susceptibility in the stratigraphic (TILT CORR) system of coordinates; b, typical materials of the component analysis (left to right): stereoprojections of changes in Jn directions during the alternating field demagnetization, Zijderveld diagrams (in stratigraphic coordinate system), demagnetization plots of samples; c, ChRM stereoprojections in geographical (GEO) and stratigraphic systems of coordinates and statistical distribution parameters ChRM: N, a number of samples in the sampling; Dср., Iср, average paleomagnetic declination and inclination, respectively; k, accuracy; α95, radius of confidence ellipse of a mean paleomagnetic vector. 1–3, projections of long (К1), average (К2) and short (К3) axes of mag- netic ellipsoids, correspondingly; 4–6, projections of average directions K1, К2 and K3, correspondingly; 7, confidence ellipses; 8, sche- matic forms of magnetic particles (arrangement of points in the upper part of the L–F diagram indicates elongated form, and in the lower part, flat form); 9, 10, ChRM projections of lower and upper hemispheres, correspondingly; 11, ChRM projections, which were used to calculate the paleomagnetic statistics; 12, projection of the ChRM mean direction and confidence ellipse; 13, ChRM projections, excluded from the paleomagnetic analysis.

MOSCOW UNIVERSITY GEOLOGY BULLETIN Vol. 74 No. 2 2019 150 BARABOSHKIN et al. laboratory studies was given to magnetic cleaning with Magneto-stratigraphic correlation. On the Geo- an alternating magnetic field. The representative magnetic Polarity Timescale (GPTS) (Ogg et al., results of the component analysis are represented in 2016) the Occitanica Zone is characterized predomi- Fig. 4B. In general, the magnetization components are nantly by reverse polarity, which is complicated in the well preserved: the maximum declination angle is less upper part of the zone by the normal-polarity M17n then 10–15°. Most of the samples have a two-com- chron (Fig. 5). Due to this, when correlating the ponent composition. The high-coercitivity charac- GPTS data, the reversed magnetozone can be theoret- teristic magnetization component (ChRM) direction ically identified as a fragment of the M17r chron or as mainly corresponds to reverse (R) polarity of the a fragment of the M16r chron, whose lower half char- geomagnetic field (Figs. 1; 4B, 4C). The sole excep- acterizes the upper part of the Occitanica Zone. In the tion is Sample 3092-5 from the level where the last case, the thickness of the M16r chron analog is ChRM direction with declination (D) and inclina- abnormally high (40 m at a minimum) in comparison tion (I), characteristic of the normal sign of polarity with analogs of other chrons previously distinguished (N) was recorded (Figs. 1, 4B, 4C). During the statis- in the Zavodskaya Balka section (Arkadiev et al., 2010, tical analysis of the R components, vectors with posi- 2015, 2017; Guzhikov et al., 2014) (Fig. 5). Consider- tive and flat (approximately zero degree) inclinations ing that the lower boundary of the R-zone was not dis- were not used. However, even without these the tinguished and the fact that this zone is complicated by ChRM distributions are characterized by a significant a fault zone, the thickness of the proposed analog of spread (Fig. 4C). The low paleomagnetic accuracies, the M16r chron must be higher. Even proceeding from along with values Q < 1 can be considered as indirect the minimum estimate (40 m) the sedimentation rate evidence of the orientation nature of magnetization. It of clays, defined as the ratio of the R-zone thickness to is probable that a low value of accuracy (6.2) is also the M16r chron duration (0.58 Ma) (Ogg et al., 2016) due to other factors, such as uncontrolled displace- is 69 m/Ma. The sedimentation rates previously calcu- ments of rocks along the sliding planes, which are lated for analogs of the M16n and M15r chrons (whose numerous in the section, or intraformation viscoplas- boundaries were distinguished in the section) are tic deformations of clays. 26.6–29.5 m/Ma (Guzhikov et al., 2014). Taking the Nevertheless, the inversion test is positive at the rather uniform structure of the Berriasian section into “C” level according to the classification from account, an increase in the sedimentation rate by sev- (McFadden and McElhinny, 1990): the angle between eral times during the M16r chron is improbable. the vectors is 9.5° and the critical angle is 13.8°. The If we suggest that the sedimentation rates in the data were compared with the previously obtained Middle and Late Berriasian were comparable, then ChRM, which corresponds to the normal polarity in the division of the R-zone thickness (21 m) by the sed- the sample with the minimum average sizes of ferro- imentation rate (26.6–29.5 m/Ma) gives the duration magnetic grains from the overlying part of the section of the accumulation of the studied interval as 0.71– (Guzhikov et al., 2014). 0.79 Ma, which is nearly half of the duration of the The fold test was carried out in two variants M17r chron (1.44 Ma). Considering that the Middle (McFadden, 1990). The first test (Fold1) provided no Berriasian interval in the Zavodskaya Balka section correct results; however, the second test (Fold2) was not studied in full volume, this estimate correlate allowed us to distinguish the pre-fold component at well with the GPTS data, where the Occitanica Zone the confidence level p = 0.05. This is different from the occupies ~70% of the duration of the M17r chron (Fig. 5). previously obtained results of testing the paleomag- From the comparison of the GPTS data one can netic data on the Upper Berriasian interval of the sec- conclude that: tion, which were incorrect or, in the case of sampling —The studied deposits with reverse polarity corre- with minimum average sizes of ferromagnetic grains, spond to the lower and middle intervals of the Occi- indicated the post-fold age of magnetization (Guzhi- tanica Zone (the M17r chron); kov et al., 2014). —The age analogs of the upper part of the Occitanica The positive results of the inversion and fold tests Zone (the M17n chron) are not found in the are important arguments in favor of the primary Zavodskaya Balka section (it is probable that this nature of magnetization. interval is missing due to a fault zone). In the paleomagnetic column of the generalized Paleontological description. To describe the speci- Zavodskaya Balka section the single reversed magne- mens, the standard terminology and measurements of tozone with a visible thickness of ~21 m corresponds shells given in (Arkadiev et al., 2012) were used. The to the studied interval of the section (Fig. 5). The collection (no. 130) is stored in the Earth Science information of the single normal-polarity sample was Museum (MSU). not taken into consideration, since it is necessary to Subfamily Olcostephanaceae Pavlov, 1892 have data from three samples at a minimum to sub- stantiate and distinguish a magnetozone (Khramov Family Neocomitidae Salfeld, 1921 and Sholpo, 1997). Subfamily Berriasellinae Spath, 1922

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Geomagnetic Polarity Generalized magnetostratigraphic Berriasian section Timescale (GPTS) Zavodskaya Balka (Feodosia) (Arkadiev et al., 2010, (Ogg et al., 2016) 2015, 2017; Guzhikov et al., 2014; this work) Stage Zone

Ma Zone Magneto- Stage polar chron Subzone Polarity

139 Thickness, m Magnetochron M14 M14r callisto Berriasella Valanginian pertransiens 140 “Thurmanniceras” M15 M15n Riasanites crassicostatum Riasanites M15r

141 boissieri

Subthurmannia M16 M16n

142 M16n. 1r “Feodosiya” Fauriella boissieri Fauriella Fauriella cf. boissieri cf. Fauriella euthymi Neocosmoceras malbosi Malbosiceras

143 occitanica M16r

Subthurmannia M17 euthymi Neocosmoceras

m 20 144 Berriasian Berriasian jacobi M18 21 ?M17r 86 10 Berriasella Berriasella Tirnovella occitanica Tirnovella privasensis Berriasella Trnovella occitanica

145 0 12 3 4

Fig. 5. Magnetostratigraphic comparison of the generalized Berriasian section Zavodskaya Balka with the geomagnetic polarity scale (Ogg et al., 2016): 1, no data; 2, finds of ammonites; lines of magnetostratigraphic correlations: 3, the most probable, 4,theoretically possible.

Genus Tirnovella Nikolov, 1966 1867. Ammonites occitanicus: Pictet, p. 81, Plate 16, Fig. 1. Tirnovella occitanica (Pictet, 1867) 2004. Tirnovella occitanica: Ettachfini, p. 105, Fig. 2. Figs. 4–8. Plate 2, Fig. 3.

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Table 1. Dimensions (mm) and ratios (%) the synonymics. Specimens from the Zavodskaya Spec. ID L H W L H/L W/L L /L Balka section are most similar to specimens from u u Tunisia (Maalaoui and Zargouni, 2016, p. 53, text- 4/130 53 25 ? 14 47 ? 26 Fig. 6, figs. 5, 6). The studied species is different from the 3/130 54 27 9 13.5 50 17 25 similar species Tirnovella subalpina (Mazenot, 1939, p. 216, Plate 34, figs. 1a, 1b, 1c; Plate 35, figs. 2a, 2b, 2c) 2/130 81? 35 15 26? 42? 19? 32? by its less evolute shell with higher whorl sections, less 1/130 94? 42? 17? 25? 45? 18? 27? rough ribbing and poorly defined near-umbilical D, maximum diameter of a shell; H, whorl height; W, whorl tubercles. width; Du, umbilical diameter. Remarks. All Crimean samples of Tirnovella occi- tanica are attributed by West European researchers to the species Pseudoneocomites retowskyi (Sarasin and 2012. Tirnovella occitanica (with synonimic): Arka- Schöndelmayer) (Frau et al., 2016). The main differ- diev et al., p. 157, Plate 9, figs. 1, 2. ence between P. retowskyi and T. occitanica is an 2016. Subthurmannia occitanica: Maalaoui, Zargouni, absence of umbilical tubercles at all stages of ontogen- p. 53, text-Fig. 6, figs. 5, 6. esis. However, T.N. Bogdanova noted the occurrence Holotype. Specimen, presented in (Pictet, 1867, of tubercles on Crimean specimens from Retowski’s Plate 16, Fig. 1); Southeastern France, Berriasian, collection stored in the Chernyshev Central Scientific described in (Le Hégarat, 1973, p. 186). Research Geological Survey Museum (TsNIGR Shape. Shells discoidal, involute, with high whorls Museum) (Bogdanova et al., 1999). In (Frau et al., increasing rapidly in height. Lateral sides are very 2016) two incomplete specimens without tubercles weakly convex. The ventral side is narrow, rounded, were presented. Due to this, it is difficult to attribute with smoothed median band. The umbilicus is narrow, the specimens to a definite species. small, with low walls. The umbilical bend is sharp, Distribution. Berriasian, Occitanica Zone in stepwise, umbilical wall is steep. Crimean Mountains, southeastern France, Bulgaria, The adult specimens, at a diameter (D) of 80 mm, are Northern Caucasus (?), Yemen, Morocco, and Tunisia. somewhat uncoiled and show an increase in the umbili- Material. Five specimens (no. 1-5/130) from the cal diameter and the height of the umbilical wall. Zavodskaya Balka quarry in the vicinity of Feodosia Sculpture. The lateral sides of the inner whorls are town. covered with very thin and dense ribbing. Ribs develop from the umbilical bend, where they occur as bundles CONCLUSIONS of two or three branches. Some ribs are repeatedly branching in the middle of the lateral sides or some- The following results were obtained these studies: what higher. Ribs spread from the umbilical edges (1) previously unknown intervals of the Berriasian bending slightly forward. In the upper third of the lat- section on the outskirts of the town of Feodosia region eral sides the ribs are S-shaped. Such ribbing is pre- were studied; (2) the ammonite Tirnovella occitanica served preliminarily to D = 50 mm. At a higher diam- Zone was substantiated; (3) the Occitanica Zone of eter the ribbing in the middle part of lateral sides the Zavodskaya Balka section corresponds to the begins to become smoother. The bases of ribs at the interval of reverse polarity of the M17 chron (M17r); umbilical bend look like small tubercles. In the lower analogs of the upper zone (M17n) of direct polarity third of the lateral side of specimen no. 1/130 weakly were not revealed, which may be due to a hiatus in the definable enlarged ribs–folds spread from the tuber- section; (4) the sedimentation conditions in the Mid- cles and disappear in the middle part. Ribbing is pre- dle–Late Berriasian, corresponding to deep shelf con- served in the upper third of lateral sides, where there ditions and Cruziana ichnofacies and (5) the presence are abundant short small ribs, which curve forward of ash material in Berriasian deposits were revealed. and spread to the ventral side, where they are inter- rupted by poorly defined smooth median line. At a similar diameter of approximately 70 mm, the ribbing ACKNOWLEDGMENTS on the lateral sides becomes less pronounced in spec. We are grateful to T.A. Kulashova (MSU. Moscow) for no 1/130 than that in spec. no. 2/130 (Table 1). assistance in collection of faunistic remains and to Comparison. The described specimens from the V.L. Kosorukov (MSU, Moscow) for performing the X-ray Zavodskaya Balka section are most similar to specimens analysis. described by O. Retowski no. 41/10916 (Retowski, 1893, Plate 3, Fig. 9) and no. 39/10916 (Retowski, 1893, Plate 3, Fig. 8). Specimens of Tirnovella occitanica FUNDING drawn by T. Nikolov (Nikolov, 1982, Plate 83, figs. 1, 2; This work was supported by the Russian Foundation for Plate 85, Fig. 4) are characterized, in our opinion, by Basic Research (projects nos. 16-05-00207а and 13-05- somewhat rougher ribbing and were not included in 00745а).

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