Biostratigraphy and Palaeoenvironment of the Upper Cretaceous Flysch Sediments of the Mestia-Tianeti Zone of the Greater Caucasus Fold System

Scientific Annals, School of Geology, Aristotle University of Thessaloniki Thessaloniki Special volume 99 75-84 Proceedings of the XIX CBGA Congress, Thessaloniki, Greece 2010

BIOSTRATIGRAPHY AND PALAEOENVIRONMENT OF THE UPPER CRETACEOUS FLYSCH SEDIMENTS OF THE MESTIA-TIANETI ZONE OF THE GREATER CAUCASUS FOLD SYSTEM

Gavtadze T.1, Mikadze Kh.2 and Chkhaidze Z.1

1Department of Stratigraphy, Alexandre Janelidze Institute of Geology, 1/9 M.Alexidze st., 0171, Tbilisi, Georgia, [email protected] 2Institute of Paleobiology, Georgian National Museum, 4 Niagvris st., 0108, Tbilisi, Georgia, [email protected]

Abstract: Detailed study of the assemblage composition of calcareous plankton contents (calcareous nannofossil and planktonic foraminifera) of the Late Cretaceous sediments of the Zhinvali-Gombori subzone of the Mestia-Tianeti zone of the Greater Caucasus fold system (GCFS) has been carried out for the first time in this region to define biozonation (Fig. 1). Within the limits of the Cenomanian- Maastrichtian 9 small foraminiferal and 19 nannoplankton biostratigraphic units (zones and subzones) have been established. Here are specified volume and age of lithostratigraphic units (successions) composing the Upper Cretaceous of the Mestia-Tianeti zone of GCFS: the Ukughmarti succession – СС9 (Early Cenomanian); the Ananuri succession - СС9-СС11 (Early Cenomanian-Early Turonian); the Margalitisklde succession - СС12-СС13 and planktonic foraminifera zones Marginotruncana pseudolineiana-M. lapparenti and Marginotruncata sigali. (Late Turonian-Early Coniacian); the Eshmakishevi succession - СС14-CC19 (Late Coniacian-Early Campanian) and zones Archaeoglobigerina basquensis and Globotruncana arca (upper part of the succession); the Jorchi succession - СС20-СС25а (Middle Campanian-Lower Maastrichtian), in the sediments of СС22с is established the small foraminiferal zone Globotruncana ventricosa-Rugoglobigerina rugosa; the Sabue succession - СС25b-СС26 and foraminiferal zone Gansserina gansseri (Late Maastrichtian). The analysis of the Late Cretaceous nannoplankton association of the Zhinvali-Gombori subzone of the Mestia-Tianeti zone of GCFS has shown the existence of four sedimentary cycles: Cenomanian-Early Turonian, Middle Turonian-Early Campa- nian, Late Campanian-Early Maastrichtian and Late Maastrichtian. During Cenomanian-Early Turonian the region represented a basin of isolated and regressive sea in the southern part of moderate cold-water belt. Since Late Turonian border of warm- and moderate cold-water belts moved to north. Transgres- sion, started in Late Turonian, continued till Early Coniacian. In the middle of Early Coniacian sea shoaling is outlined. Sedimentation took place in a shallow and calm basin from Late Coniacian till the end of Santonian. Fact of sedimentation missins of the four nannoplanctonic zones СС19, СС20, СС21 and СС22a,b from the sections of the Zhinvali-Pkhoveli nappe and the analysis of the redeposited forms enablesenable to admit break in sedimentation caused by Early Campanian regression and Late Campa- nian transgression. The short-term Middle Maastrichtian regression was replaced by the Late Maastrich- tian transgression. Key words: Caucasus, Cretaceous, biostratigraphy, nannoplankton, small foraminifera, flysch

1. Introduction Studied by us the flysch deposits The Late Creta- cies. Due to considerable prevalence of "barren" ceous are spread in the junction area of two large (deprived of fossil fauna) rocks in these sediments, geotectonic structures - fold system of the Greater and also the extremely complicated tectonic struc- Caucasus and the Transcaucasian intermontane ture, the detailed stratigraphy of Mesozoic- area. Under the scheme of tectonic zoning of the Cenozoic rocks of the Mestia-Tianeti zone of the Caucasus (Gamkrelidze and Gamkrelidze, 1977) it GCFS still remains unsolved. Although the study enters into the Zhinvali-Gombori subzone of the of this region lasts for more than a century, its stra- Mestia-Tianeti zone of GCFS and is presented by tigraphic partition is restricted only to the lithostra- flysch, flyschoid, normal sea and olistostrome fa- tigraphic units (formation and sub-formation); their

Ψηφιακή Βιβλιοθήκη Θεόφραστος - Τμήμα Γεωλογίας. Α.Π.Θ.

Fig. 1. Geological map of the studied region age has been defined by scanty faunistic data and Cretaceous sediments of the Zhinvali-Gombori on the basis of their stratigraphic position. That’s subzone of the Mestia-Tianeti zone GCFS, and for why the question of age and volume of these for- specifying the volume and age of the formations, mations are still in dispute for some researches. in the facies of Sadzeguri-Shakhveli and Zhinvali- The first data concerning the stratigraphy of these Pkhoveli nappes the sections of the Ksani and sediments were published by Rengarten (1924) and Aragvi river basins (the rivers Aleura, Sakanaphe, Vassoevich (1933). Later on, they developed the Arkala, Didi Jakha, Patara Jakha; near the villages stratigraphic schemes being substantially specified Sadzeguri, Korinta, Ananuri, Muguda, Avenisi, by several generations of researchers: Vassoevich Pavleuri) have been studied. (1941), Tsagareli (1954), Mrevlishvili (1957), The researches were based on the extensive ma- Adamia (1958), Kandelaki (1975), Leonov terial collected by the authors during the field (1975,1981), Gamkrelidze and Gamkrelidze works (2007-2009). More than 700 samples in to- (1977), Gambashidze (1970, 1981, 1991), Gamkre- tal were obtained from the 11 layer-by-layer stu- lidze et al. (1985), Giorgobiani and Zakaraia died sections of the Late Cretaceous and the bor- (1980) et al., who made a valuable contribution to dering sediments. The sampling interval ranged study of geological structure of the region. range from 0.3m to 5.0m. Nannoplankton and 2. Materials and methods small foraminifera were studied from the same samples. For the detailed stratigraphic division of the Upper

Ψηφιακή Βιβλιοθήκη Θεόφραστος - Τμήμα Γεωλογίας. Α.Π.Θ. Samples for the calcareous nannofossils were -СС9с. As for H.albiensis, its joint occurrence processed in the laboratory of the Institute of Ge- with above noted species, as in subsequent zones ology of Georgia. Suspension slides were prepared with M. decoratus and Q. Gartneri, indicate its using a standard method of decantation and they secondary occurrence in corresponding deposits. were studied under the light microscope Amplival, The Ananuri formation conformably rests on top of at 1200x magnification. the Ukughmarti formation in all the studied sec- Biostratigraphic data were correlated with the tions. It is distinctly divided into three parts. The standard nannoplankton “CC” zones by Sissingh Lower Ananuri sub succession is built up of silici- (1977) and Perch-Nielsen (1985). fied aleurolites, fine-grained sandstones, sandy limestones, clay marls, lenses of black flint and si- The samples for foraminiferal analysis were derite concretions. Gambashidze (1970) in the treated in the laboratory and washed with glacial section of the village Muguda in the sediments of acetic acid and copper vitriol. the sub-formation, has defined the Early Cenoma- 3. Results nian microfauna Thalmaninella appenninica (Renz.), Rotalipora cushmani cushmani (Morr.), The Upper Cretaceous flysch in the Mestia-Tianeti Reophax minuta (Tapp.), Anomalina brotzeni Kell. zone GCFS starts with the Ukughmarti formation. It continues the succession of underlying Navtisk- According to nannoplankton these deposits corres- hevi suite without visible unconformity. But in pond to upper part of the subzone СС9с and lower some areas its transgressive position is observed. part of the zone СС10 ( FO Microrhabdulus deco- The suite is represented by polymictic. This forma- rates to FO Quadrum gartneri). tion was first described by Vassoevich (1933); it is The Middle Ananuri sub-formation is distin- represented by polymictic sandstones, marls, clay guished by its black color and is presented by shales, argillites, sandy limestones and lenses of black flints, silicified sandstones, silicites and con- polymictic gravelstones and breccia-conglomerates cretions of black flint. It corresponds to the upper (in the lower part of the formation). The rocks con- part of the zone СС10. tain a considerable admixture of pyroclastic material. The Upper Ananuri sub-formation is more light co- loured. It is built by silicified sandy limestones, The identification of the belemnite species Neohi- sandy marls, marls, limestones, siliceous rocks and bolites ulthimus d'Orb., Inocerames Inoceramus tuffs. Due to its stratigraphic position and to solita- crippsi Mant., I. cf. cuneiformis Orb. and rare ry findings of the Early Turonian Inoceramus la- small foraminiferas Anomalina cenomanica Brotz., biatus Schloth. and Globotruncana inflata Bolli in Hedbergella planispira (Tapp.), Thalmanninella the upper part of the record, some researchers evoluta Sig., T. appeninnica Renz. previous re- attribute the lower sub-formation to the Late Ce- searchers (Rengarten,1941; Tsagareli,1954; Gam- nomanian, and the middle and the upper sub- bashidze, 1981) took the suite into Early Cenoma- formation - to the Early Turonian (Gambashidze nian. Data got by studying nannoplankton proved 1984; Kandelaki 1975;). According to other scien- this decision. tists only the upper part of the record can be consi- Ukugmarti formation contains association of nan- dered as Early Turonian (Vassoevich 1933; Tsaga- nofossils that is characteristic for the zone of Eif- reli 1954; Adamia 1958, et al.). fellithus turriseiffelii (Fig.2). Because of C. kenne- According to our data, lower parts of Upper Ana- dy’s absence in the association (marking species of nuri subsuite belong to Late Cenomanian zone the upper subzone of Eiffellithus turriseiffelii’s СС10, and the other part – to the zone СС11 (FO zone) and continuous occurrence of H.albiensis Quadrum gartneri to FO Lucianorhabdus male- (according to its disappearing the lower subzone of formis ) of Early Turonian. In Upper Ananuri suite the zone is determined) up to the layers of the zone sediments, according to foraminifera the zone Whi- СС11, dividing of Eiffellithus turriseiffelii zone in- teinella archaeocretacea is established. Besides to subzones failed. Though existence of Corolli- the index-species, here are recorded W. brittonen- thion exiguum, Quadrum intermedium and Diloma sis (Leoblich et Tappan), W. baltica Dauglas et galei (species appearing in Cenomanian) in the Rankin, W. aprica (Leoblich et Tappan), Dicari- layers of Ukugmarti formation allow us to time the nella imbricate (Mornad) D. hagni (Scheib.), formation to the upper- Early Cenomanian subzone Praeglobotruncana helvatica (Bolli), Heterohelix

Ψηφιακή Βιβλιοθήκη Θεόφραστος - Τμήμα Γεωλογίας. Α.Π.Θ. Fig. 2. Biostratigraphy of the Late Cretaceous flysch sediments of the Zhinvali- Gombori subzone. moremani (Cush.), H. reussi(Cush.), Hedbergella ture of the formation marls and limestones predo- delrionensis (Carsey). H. planispira(Tappan). On minate, whereas clay shales and sandy limestones the basis of all above noted, we assume that forma- are subordinate components. The succession in tion of Middle Ananuri sub-formation took place places shows coarse-clastic rocks passing in as- (together with bottom part of Upper Ananuri suite) cending section into alternation of limestones and by the end of Late Cenomanian, and the main part marls. In the majority of sections, the succession of Upper Ananuri sub-formation – in Early Turo- conformably rests the upper band of the Ananuri nian. formation. In some places, especially in the south- The Margalitisklde formation is characterized by ern facies zones, transgressive bedding is ob- red colorcoloring and carbonaceous. In the struc- served. Varentsov (1950), based on finding of In-

Ψηφιακή Βιβλιοθήκη Θεόφραστος - Τμήμα Γεωλογίας. Α.Π.Θ. oceramus brongniarti Mant. I. inconstans Woods According to our data Eshmakiskhevi suite en- in the Ksani river-gorge has considered the forma- volves nannoplankton zones СС14 (FO M. decus- tion as Upper Turonian. The same opinion share sata to FO Reinhardtites anthophorus), CC15 (FO Vassoevich (1933) and Kandelaki (1975). Howev- R. Anthophorus to FO L. сayeuxii),CC16 (FO L. er, some scientists due to the replacement of red cayeuxii to FO C.obscurus),CC17(FO C.obscurus limestones of the Margalitisklde formation by of li- to FO B. parca), CC18 ( FO B. parca to LO M. thographic limestones of the Eshmakiskhevi for- furcatus), CC19 (LO M. furcatus to FO C.aculeus) mation in the Ksani and Aragvi river-gorges and is dated as Late Coniacian-Early Campanian. (where the thickness of the formation considerably Small foraminiferas were found on the second part decreases) specify the changes of age boundaries of the suite. of red limestones and date it as Early Turonian In the sediments, corresponding to zone CC16, on (Rengarten 1929; Tsagareli 1954;). According to the basis of small foraminiferas were detrmined Gambashidze (1981), it corresponds to the Late zones Archaeoglobigerina basquensis and Contu- Turonian and Coniacian. sotruncana fornicata (Late santonian). For the first Observations showed that Margalitisklde forma- zone are characterized A. cretacea (d’Orb.), Whi- tion includes nannoplankton zones CC12 (FO Lu- teinella baltica Dougl. et Ran., Hedbergella pla- cianorhabdus maleformis to FO Martasterithes nispira (Tapp.), Valvulineria lenticulata (Reuss), furcatus) and CC13 (FO Martasterithes furcatus Verneulina muensteri Reuss, Gavelinella pertusa to FO M.decussata). The zone (СС12) by the (Mors.), Stensioina granulate (Olb.), S. exsculpta planktonic foraminifers corresponds to a zone (Reuss). A. cretacea (d’Orb.), Whiteinella baltica Marginotruncata pseudolineiana-M. lapparenti, Dougl. et Ran., Hedbergella planispira (Tapp.), where for the first time occurred the double-keel Valvulineria lenticulata (Reuss), Verneulina mu- forms of the genus Marginotruncana. The given ensteri Reuss, Gavelinella pertusa (Mors.), Sten- foraminifer zone is dated as the Late Turonian. sioina granulate (Olb.), S. exsculpta (Reuss). From According to small foraminifera in sediments of the second zone are met Gontusotruncana fornica- the zone СС13 was determined zone of Margino- tea (Plum.), G. arcaformis Masl., Globotruncana truncata sigali. Some explorers (Burnett 1998; bulloides Mart., G. linneiana (d’Orb.), Praebuli- Lees 2002; Hradeska at al. 1999.) have dated the mina reussi (Mor.), Eponides concinna Brotz., Ci- zone СС13 as the Middle Turonian-Early Conia- bicides ribbingi Brotz., Reussela praecursor cian. As well, as in the lowermost layers zone Knips. СС13 by foraminifera were found typical Conia- In layers corresponding to the nannoplankton cian Marginotruncata marginata, (Reuss), M. si- zones СС17 and СС18, by planktonic foraminifera gali (Reichel), Dicarinella concavata etc. we refer the zone Globotruncana arca (Early Campanian) the zone СС13 to the Early Coniacian. Thereby, is established; it comprises Rugoglobigerina kelleri Margalitisklde suite is dated as late Turonian-Early (Subb.), Archaeoglobigerina cretacea (d’Orb.), Coniacian. Globorotalites micheliana (d‘Orb.), Cibicides The Eshmakiskhevi formation conformably over- beaumontianus (d’Orb.), Stensioina exculpta gra- lies the sediments of the Margalitisklde formation cilis Brotz., Valvulineria lenticulata (Reuss), Boli- and it is presented by rhythmical alternation of li- vinoides strigillatus (Champ.). thographic limestones, marls and shales. The Jorchi formation is built up by medium- Here, are observed the interlayers of sandy slates layered arenaceous limestones alternating with vio- which in places pass into the coarse-grained sand- let, red, green and greenish-grey marls and marly stones and microconglomerates. The age of the shales. This formation has been allocated by Vas- formation varies. Some scientists refer that the soevich (1941), who attributed the Jorchi forma- formation is of Upper Turonian-Early Senonian tion to the Lower Campanian based on the pres- age (Rengarten 1929; Tsagareli 1954); Others, re- ence of the Inoceramus ex. gr.balticus Bochm. and late it to the Coniacian-Santonian (Vassoevich I. balticus Bochm. at the boundary of the layers of 1933; Kandelaki 1975). Varentsov (1950), based the Jorchi and Eshmakiskhevi formation. Tsagareli on the findings of Inoceramus undulate plicatus (1954) regards it as Santonian-Lower Campanian; Roem in the Ksani river-gorge, dates it as Conia- Kandelaki (1975) and Gambashidze (1981), based cian and finally Gambashidze (1981) considers it on the presence of small benthic foraminifera Boli- of the Santonian age. vinoides decoratus (Jons.), Boliniva incrassate

Ψηφιακή Βιβλιοθήκη Θεόφραστος - Τμήμα Γεωλογίας. Α.Π.Θ. Reuss stratigraphically positioned the formation to and foraminifers association of the Zhinvali- the Campanian. Gombori subzone of the Mestia-Tianeti zone of We determined Nannoplanktonic zones in Jorchi GCFS has shown the existence of four sedimentary suite: CC20 (FO C. aculeus to FO U. sissinghii), cycles: Cenomanian-Early Turonian, Middle Turo- CC21 (FO U. sissinghii to FO U. trifidus), CC22 nian-Early Campanian, Late Campanian-Early (FO U. trifidus to LO E. eximius), CC23(LO Maastrichtian and Late Maastrichtian (Fig. 3). E.eximius to LO U. trifidus), CC24(LO U. trifidus On the territory of Georgia contained in the Late to LO R. levis) and subzone lower part of the zone Albian pool there were is established some large CC25a (LO R. levis to FO L. quadrates). From sites of a land, where the Cenomanian sediments above, age of Jorchi suite is defined as Middle with the washout rest on the underlying formations Campanian-Early Maastrichtian. (Gambashidze, 1981). By foraminifers in the sediments, corresponding to The beginning of the first cycle gets the better of nanoplanktonic subzone СС22с the Late Campa- Early Senomanian transgression. All is a situation nian zone Globotruncana ventricosa- the calm course of sedimentation at the end of the Rugoglobigerina rugosa is established. Besides the Albian was disturbed by pulses of the Austrian index-species here are registered Globotruncana phase of orogeny and senomanian transgression stuartiformis (Dalb.), Heterohelix pulchera took place against the background of tectonic mo- (Brotz.), Bolivinoides culverensis Barr., B. Pustu- viments. On existence of a land before Senoma- lata Reuss, Cibicides beaumontianus (d’Orb.), nian indicates secondary occurrence of Hayesites Stensioina pommerana Brotz., Osancularia cirdie- albiensis (which existed from the end of Aptian up riana (d’Orb.). to Early Albian). Presence of this species in sediments of Ukugmarti and Ananuri formation, it is The Sabue formation is bedded transgressively on different horizons of Jorchi suite. It is represented explained with, that couldhave been deposited in by alternation of medium- and thick-layered limes- Senomanian only after land emergence in Late Al- tones, arenaceous limestones, marls, marl shale bian. and clay shales. Here are observed interlayers of Nannoplanktonic complexes are represented even- microconglomerates, fine-pebbly conglomerates, ly as by deep-water- so shallow–water species in gravelstones, breccias and sandstones. the sediments of Ukugmarti and Lower Ananuri The presence of large benthic foraminifera - Orbi- formations, indicating near shore basin. Starting toides apiculata (Schlumb.), O. media (d’Arch.), from Middle Ananuri subformation, quantity of O.soti (Schlumb.), Lepidorbitoides minor deep-water species sharply reduces in nannofacci- (Schlumb.), etc., small benthic foraminifera - lies’ association, and till the end of Upper Ananuri Pseudotextularia elegans Rz., Racemiguembelina subformation shallow-water nannoplanktonic varians ( Rz.) and ammonites - Hauriceras sulca- forms dominate in succession. This is also proved tum (Kner.) attribute a Maastrichtian age the Sabue by complexes of foraminiferas (Hedbergella, Whi- formation. teinella, Dicarinella). On the basis of our data in Sabue formation sedi- May consider that the scales of Cenomanian trans- ments is established the planktonic foraminiferal gression weren`t great. For the benefit of this as- zone Gansserina gansseri. Besides the index- sumption there is a fact that in spite of transgres- species here are registered Rugoglobigerina ma- sive Basin of Cenomanian sea of Zhinval-Gombori crocephala Bronn., R. hexacameratta Bronn., R. formation still remained isolated. There of given pennyi Bronn. evidence specific character of nannoplankton association in these sediments. The Cenomanian-Early In the sediments of the Sabue succession the oc- Turonian (the Ukughmarti and Ananuri forma- currence of the species Lithraphidites quadratus, tions) by complex are characterized by the mixed Micula murus and Micula prinsii, has enabled to complexes of warm- (Watznaueria barnese, allocate here the same named, which correspond W.ovata, W. biporta, Eprolithиs moratus, Ruciano- biostratigraphic units applicable to those in Sis- lithus irregularis, Quadrum intermedium) and singh’s (1977) zones - CC25b, CC25c and CC26. cold-water forms (Stradneria crenulata, Tranoli- 4. Discussion thus phacelosus, Lithraphidites carniolensis, Pla- cozygus fibuliformis, Broinsonia matalosa, B. sig- The analysis of the Late Cretaceous nannoplankton nata, Glaukolithus diplogramus, Eiffellithus

Ψηφιακή Βιβλιοθήκη Θεόφραστος - Τμήμα Γεωλογίας. Α.Π.Θ. Fig. 3. Litho- and Biostratigraphical correlation for the Late Cretaceous sediments of the Sadzeguri-Shakhvetili and Zhinvali-Pkhoveli nappes of the Zhinvali-Gombori subzone. 1. Limestones; 2. Sandy limestones; 3. Lithographic limestones; 4. Sand- stones; 5. Polymictic sandstones; 6. Silicified sandstones; 7. Marls; 8. Marly shales; 9. Clay shales; 10. Gravelstones; 11. Microconglomerates; 12. Breccia- conglomerates; 13. Siliceous rocks; 14. Black flint; 15. Tuffs. turriseiffelii, Microstaurus chiastius, Zeugrhabdo- Margalitisklde formation sediments are characteri- tus bicrescenticus, Prediscosphaera columnata), side by rich nannofocillies. In the association of though the last ones exceed both in species and the zone Lucianorhabdus maleformis (CC12) took quantitative respect. On this ground we can assume place abrupt renewal of species. Besides the new that by that time the region was located on the bor- species: Lucianorhabdus maleformis, Placozygus der of warm and reasonably cold waters. Fibuliformis, Eprolithus aff. Rarus, Helicolihus anceps, Acuturris scouts, there are also species in The second cycle starts with Late Turonian trans- common for the end of the Early and the beginning gression and coinsides with the pick of maximal of Late Cretaceous: Loxolithus armilla, Chiastozy- eustatic transgression (UZA 2.5) (Haq et al., 1987). gus anceps, Nannoconus regularis, N.elongata,

Ψηφιακή Βιβλιοθήκη Θεόφραστος - Τμήμα Γεωλογίας. Α.Π.Θ. Zeugrhabdotus burvellensis, Gartnerago chiasta, iplanarius trifidus (CC22с). Extended, in conse- etc., however in the sediments of the previous quence of rising, land around cordilleras, after successions they are absent. Hence, there appears submersion of Zhinval-Gombori subzone, again possibility to assume the existence of the isolated was covered by the sea, causing a break in sedi- basin and increasing regression during the Ceno- mentation and fall-out of the nannoplancton zones manian-Early Turonian sea. Transgression in the СС19, СС20, СС21 and СС22a,b from the sec- beginning of the Middle Turonian provided the tions. connection of the given basin with the open sea, The Late Campanian transgression is related to the being favorable for the migration of the above beginning of the third sedimentation cycle. Here mentioned species. Apparently, the transgression Jorchi formation is mainly represented by marly continued during the Early Coniacian as well. limestones and marly sandstones. Nannoplanktonic From the migrated species in the sediments of the zones, singled out here, and also associations of fo- zone Martasterithes furcatus (CC13) have already raminiferas are mainly planktonogenic. In sedi- been fixed the species preferring deep water condi- ments, relevant to the zone CC22c warm-water tions: Broinsonia enormis, Tranolithus gabalus, taxons Uniplanarius, Ceratolithoides, Watznaue- Gartnerago segmentatum, etc. There appear new ria, Micula, Marthasterites, Globotruncana stuar- forms: Marthasterites furcatus, M. inconspicuous, tiformis, Globotruncana ventricosa dominate, in- M. crassus, Micula swastika, Lithastrinus septena- dicating the relationship of the basin with the rius - species preferring warm climate. It points to Tethys. the northward advance of the boundary between According to nannoplankton, Jorchi formation is the warm- and moderately cold belts. From the relevant to the zones CC22c, CC23, CC24 and second half of the zone the amount and variety of CC25a in all studied successions. The last general- nannofossils sharply reduced. Many transient spe- ly, especially in the limits of Zhinval-Pkhoveli cies disappeared. In the corresponding sediments sheet, is either missing or is met just in lower lay- of the Margalitisklde formation already appeared ers. Transgressive Sabue formation, in the given coarse-grained sandstones. That points to the successions, starts with the subzone CC25в (the shoaling of the basin, apparently caused by the be- fourth sedimentation cycle). Exception represent ginning of eustatic regression, both of UZA3 su- just some areas in the River Ksani basin, where percycle and UZA3.1. cycle (Haq et al., 1987). Sabue formation starts with the zone CC25c. Ab- In the association of the zone (СС14) sharply de- sence of CC25a and CC25b in the upper part of the creases quantity of the species preferring deep wa- subzone, before Maastrichtian transgression, prob- ter conditions: Watznaueria, Eiffellithus, Cyclage- ably was related to the Late Laramian rising and losphaera, Stradneria, etc. Begin to dominate the erosion. This is well manifested in the sediments of shallow water forms: Quadrum, Micula, Marthas- Sabue formation, represented by coarse-grained terites, Rucianolithus, Eprolithus, Microrhabdulus, material. etc. Such parity proceeds up to the Early Campa- Thus on the basis of the detailed analysis calca- nian indicating the existence of a shallow, calm sea reous nannofossil and planktonic foraminifera all basin during the deposition of the Eshmakiskhevi standard zones (СС) of the Late Cretaceous are formation; the succession is represented by the identified junction in connection adjournment of monotonous strata of lithographic limestones with the Zhinvali-Gombori subzone of the Mestia- interlayers of grey and variegated marls. However, Tianeti zones of the Greater Caucasus fold system at the end of the formation dominate granular, are- (GCFS) are established all standard zones (СС) of naceous limestones with interlayers of microgrey- the Late Cretaceous. It has allowed to specify an wacke carbonate sandstones. Retreat of the sea is age range, volume and capacity lithostratigraphic well expressed. Here, the formation is terminated units, composing the Upper Cretaceous of the by the nannoplankton zone -СС18 and without vis- Mestia-Tianeti zones. The recovered of the mainly ible unconformity is overlapped by the subzone paleoclimatic and paleogeographic the moments of СС22c of the Jorchi formation. The uninterrupted the Late Cretaceous in this part GCFS. sedimentation of the succession is observed in the sections of the Zhinvali-Pkhoveli nappe (rivers 5. Conclusions Ksani, Arkala, etc.), the layers of the zone СС18 Thus, based on the detailed analysis of nannofos- are replaced by the upper subzone of the zone Un- sils and planktonic foraminifera in the sediments of

Ψηφιακή Βιβλιοθήκη Θεόφραστος - Τμήμα Γεωλογίας. Α.Π.Θ. the Zhinvali-Gombori subzone of the Mestia- forms enables to admit break in sedimentation Tianeti zone GCFS, all standard Late Cretaceous caused by Early Campanian regression and Late zones (СС) are established. It has allowed updating Campanian transgression. At the end of the Middle of age range, volume and thickness of lithostrati- Maastrichtian took place a short-term regression graphic units composing the Upper Cretaceous of that was replaced by the Late Maastrichtian trans- the Mestia-Tianeti zone. Sedimentation of the gression. Ukughmarti formation took place in the Early Ce- nomanian, in the upper part of the zone Eiffellithus Acknowledgements turriseiffelii (СС9). The Ananuri formation covers Our special gratitude to Dr David Zakaraia for the period from Early Cenomanian (upper part) to great help in obtaining the material and planning Early Turonian and corresponds to the zones СС9- the routes during the field works. We should also СС11. The Margalitisklde formation is dated as like to thank Dr Laura Popkhadze for participation Late Turonian-Early Coniacian; it corresponds to in field activities, Mrs. Medea Gasviani for her the zones СС12-СС13 by nannoplankton and to help during the laboratory works. Marginotruncana pseudolineiana-M. lapparenti and Marginotruncata sigali by planktonic forami- References nifera. The Eshmakishevi formation covers nan- Adamia Sh.A., 1958. Materials on Geological Structure noplankton zones СС14-CC19 and is dated as Late of the Greater Caucasus Piedmonts between the Pata- Coniacian-Early Campanian. ra Liakhvi River Basin and the Meridian of the Town Dusheti. “Metsniereba”, Tbilisi, 34p. (in Russian). In the upper part of the succession by foraminifers Burnett J.A., 1998. Upper Cretaceous. In: Calcareous are established the zones Archaeoglobigerina bas- Nannofossil Biostratigraphy (ed. Bown P.R.). British quensis and Globotruncana arca. The Jorchi suc- Micropaleontological Society publication Series. cession corresponds to the Middle Campanian- Chapman et Hall.Kluwer Academic Publishers, Lon- Lower Maastrichtian zones СС20-СС25а. By fo- don, 132-199. raminifers in the sediments of the subzone СС22с Gambashidze R.A., 1970. To the Stratigraphy of the Up- is established the zone Globotruncana ventricosa- per Cretaceous Sediments of the Liakhvi-Aragvi In- terfluve. Bulletin of the Academy of Sciences of Rugoglobigerina rugosa. The Sabue succession Georgian SSR, vol.70, issue 2, Tbilisi, 369-372 (in corresponds to the zones Lithraphidites quadratus, Russian with English abstract). Micula murus and Micula prinsii - their total vo- Gambashidze R., 1981. History of Geological Evolution lume is synchronous to that of СС25b-СС26 and is of Georgia in the Late Cretaceous. Proceedings of dated as Late Maastrichtian. By foraminifers in Geological Institute of the Acad. Sci. of GSSR, new them the zone Gansserina gansseri is established. series, issue 82 Tbilisi, 110p. (in Russian). Gambashidze R.A., 1991. Stratigraphy and Correlation of For this part of GCFS are reconstructed the main the Upper Cretaceous Sediments of the Assa, Kambi- paleoclimate and paleogeographic events of the leevka and Aragvi River Basins. In: Geological Struc- Late Cretaceous. Here has been established the ex- ture of the Assa-Aragvi Intersection of the Greater istence of four sedimentary cycles: Cenomanian- Caucasus. Proceedings, new series, issue 102, “Mets- Lower Turonian, Middle Turonian-Early Campa- niereba, Tbilisi, 8-10 (in Russian with English ab- nian, Late Campanian-Early Maastrichtian and stract). Late Maastrichtian. In the Cenomanian-Early Tu- Gamkrelidze P.D. and Gamkrelidze I.P., 1977. Tectonic ronian there was a basin of isolated, regressive sea Nappes of the Southern Slope of the Greater Cauca- in the southern part of the moderately cold-water sus. Proceedings of Geological Institute of the Acad. Sci. of GSSR, new series, issue 57, 81p. (in Russian). belt. From the Late Turonian the boundary be- Gamkrelidze I.P., Giorgobiani T.V., Basheleishvili L.V. tween the warm- and moderately cold-water belts and Zakaraia D.P., 1985. Experimental Modeling of moved to the north. Transgression that started in the Transformed Fold Systems of Some Zones of the the Late Turonian lasted till the Early Coniacian. Caucasus. Bulletin of the Academy of Sciences of In the middle part of the Early Coniacian is out- Georgian SSR, vol. 120, issue 2, 337-340 (in Russian lined shoaling of the basin. From the Late Conia- with English abstract) cian to the end of the Santonian sedimentation took Giorgobiani T.V. and Zakaraia D.P., 1980. On the Zo- place in the shallow, calm marine basin. The omis- nality of the Fold System of the Northwest Caucasus. sion of the nannoplankton СС19, СС20, СС21 and Bulletin of the Academy of Sciences of Georgian СС22a, b zones from the sections of the Zhinvali- SSR, vol. 100, issue 2, 357-360 (in Russian with Eng- lish abstract). Pkhoveli nappe and the analysis of the redeposited Haq B.U., Hardenbol J. and Vail P.R., 1987. Chronology

Ψηφιακή Βιβλιοθήκη Θεόφραστος - Τμήμα Γεωλογίας. Α.Π.Θ. of Fluctuating Sea Levels Since the Triassic. Science, Perch-Nielsen K., 1985. Mesozoic Calcareous Nannofos- 235, 1156-1167. sils. In: Plankton Stratigraphy. Cambridge University Hradeka L., Lobitzer H., Ottner F., Sachsenhofer R.F., Press, Cambridge, 329-426. Siegel-Farkas A., Svabenicka L. and Zorn I., 1999. Rengarten V.P., 1932. Geological Sketch of the Georgian Biostratigraphy and Palaeoenvironment of the Marly Military Road Region. Proceedings of All-Union So- Marine Transgression of WeiSSßenbachalm Lower ciety for Geological Prospecting, issue 148, 70p. (in Gosau-Subgroup (Upper Turonian-Lower Santonian Russian) Grabenbach-Formation, Northern Calcareous Alps, Rengarten V.P., 1940. Facies of the Cretaceous Deposits Styria). Abhandlungen Der Geologischen Bundesans- of the Caucasus. Transactions of the 17-th Session of talt, ISSN 0378-0864, ISBN 3-85316-007-7, Band Geological Congress, vol.5, 484p. (in Russian) 56/2, 475-517, Wien (in English with German ab- Sissingh W., 1977. Biostratigraphy of Cretaceous Calca- stract). reous Nannoplankton. Geologie en Mijnbouw, 57, Kandelaki D.N., 1975. History of Geological Evolution 433-440. of the Greater Caucasus Piedmonts (Liakhvi and Iori Tsagareli A.L., 1954. Upper Cretaceous of Georgia. Pro- Interfluve). Author’s abstract of Ph.D. thesis, “Mets- ceedings of Geological Institute of the Academy of niereba”, Tbilisi, 31p. (in Russian). Sciences of Georgian SSR, Monograph #5, Tbilisi, Lees J.A., 2002. Calcareous Nannofossil Biogeography 464p. (in Russian). Illustrates Palaeoclimate Change in the Late Creta- Varentsov M.I., 1950. Geological Structure of the West- ceous Indian Ocean. Cretaceous Research 23, Pub- ern Part of Kura Depression. Academy of Sciences of lished by Elsevier Science Ltd 537-634 the USSR, M-L, 258p. (in Russian). Leonov M.L., 1975. Wild Flysch of the Alpine Region. Vassoevich N.B., 1933. Some Results of Geological In- “Nauka”, Moscow, 138p. (in Russian). vestigations in the Mountainous Kakheti (1928-1932), Leonov M.L., 1981. Olistostromes in the Structures of “Gostexizdat”, Tiflis, 74p. (in Russian). Fold Areas. “Nauka”, Moscow, 171p. (in Russian). Vassoevich N.B., 1941. Geological Sketch of the North- Mrevlishvili N.I., 1957. Geological Structure of Foothills western Part of Kakheti and Eastern Part of Ertso- of the Greater Caucasus and the Dusheti Region. Pro- Tianeti District. G.P.K. of “Gruzneft”, 310p. (in Rus- ceedings of Geological Institute of the Acad. Sci. of sian). GSSR, geological series, vol. X(XV), 139-147 (in Russian).

Ψηφιακή Βιβλιοθήκη Θεόφραστος - Τμήμα Γεωλογίας. Α.Π.Θ.