FACIES CONTROL ON THE COMPOSITION OF SERPUKHOVIAN AND EARLY BASHKIRIAN FORAMINIFERAL ASSEMBLAGES IN THE MIDDLE TIEN-SHAN MOUNTAINS. CENTRAL ASIA OLGA ORLOV-LABKOVSKY Received January 1, 2002; accepted March I t, 2A03 Ke1 zaords: Facìes, Foraminifera, statistics, mid-Carboniferous, Tien-Shan, Central Asia. Absrract. Serpukhovian-lower Bashkirian deposits are widely developed in the Middle Tien-Shan Mountains of Uzbekistan and ad- jacent countrìes of Central Asia. These deposits formed in a sedimen- tary basin exhibiting four distinctive facies that differ in foraminiferal diversity and population densit,v. The facies types, named for mountain ranges containing representàtive sections, are called 1) Talassìc, for inner shelf, shallow- water marine carbonates; 2) Ugamic, for carbonaceous deposits accumulating on an open, shallow-water, outer carbonate shelf platform; 3) Karzhantauìc, for interbedded volcaniclastics and shallow- water marine carbonates deposìted on a eroded surface; and 4) Paltauic, for basinal beds containing thin-bedded, graded and lamìnated organic limestones and interbedded turbidites. A statistical program (Sorenson's Coefficients of Species Similarity) was used to compare assemblages ìn eight foraminiferal zones from coeval fades across the basin. Highest similarity coefficients occur in the early Serpukhovian and are prob- ably related to a marine transgression that flooded the basin. Regres- sion and volcaniclastic sedimentation account for lower coefficients in the remainder of the Serpukhovian. Increased foraminiferal diversity and abundance in the earliest Bashkirian were probably caused by the opening of new connections to adjacent Paleotethyan basins only to be followed by more restricted environmental conditions and lower simi- larity coefficients later in the early Bashkirian. Riasswnto. Successioni di età Serpukhoviana-Bashkiriana inferiore sono molto diffuse nelle montagne del Tien-Shan centrale in Uzbekisran e nelle regioni adiacenti dell'Asia centrale. Esse si sono formate in un bacino sedimentario in cui è possibile individuare quattro associazioni di facies sulla base della diversità nei foraminiferi e la densità delle loro popolazioni. Le associazioni di otto zone a foraminiferi sono stare confrontate tra di loro mediante un programma statistico (coefficiente di similarità specifica di Sorenson). Le maggiori similarità si rrovano nel Serpukhoviano inferiore e sono probabilmente collegate alla trasgressione marina che interessò il bacino. La successiva regressione e sedimentazione vulcanoclastica spie- gano le basse similarità per il resto del Serpukhoviano. La ripresa della diversità ed abbondanza in foraminiferi nel successivo Bashkiriano basale furono probabilmente dovute all'apertura di nuove connessioni con l'adia- cente Paleotetide. Tuttavia gìà durante il Bashkiriano inferiore condizioni più confinate produssero più bassì coefficienti dì similarità. Introduction Serpukhovian - lower Bashkirian deposits are wide- ly developed in the Middle Tien-Shan of Uzbekistan and adjacent countries (Fig. 1). They are part of a continu- ous marine carbonate sequence, over 1200-m thick that sras formed in different areas on a carbonate shelf in Serpukhovian - early Bashkirian time. Regional strato- types (type sections) of the Lower Carboniferous and the lower Bashkirian are concentrated in the western part of mountain ranges between the Chatkal and Talass Ala- tau mountains, including the Mashatian, Keltimashatian and Koikebiltaustian substages of the Serpukhovian and the Seslavian and Uzunbulakian substages of the lower Bashkirian (Fig.2). The foraminiferal assemblage zones, established for these substages (Orlova 1994; Orlov-Lab- kovsky 1.999), are correlated with Urals-Russian Platform {oraminiferal zones in Table 1. Basin from the Chatkal to Talass Alatau ranses and in the Karzhantau Range exposes four distinct facles types. These are the Talassic (shallow-water carbonate sediments), Ugamic (an open shallow sea accumulation of carbonaceous sediments) , Karzhantauic (a volcanogenic - terrigenous shelf sequence with interbedded shallow- water carbonates) and Paltauic (carbonaceous - terrig- enous sediments of the basin) facies-types of sections. The foraminifers in each facies differ in species and ge- neric diversity and density of populations. Materials and method The means used to correlate facies to foraminife- ral associations include determining the characteristic or dominant species, and the areal distribution of the fauna Department of Zoology, Tel-Aviv University, Tel-Aviv 69978,Israel, olgaorl@post.tau.ac.il Euroasiatic Scheme in Urals and Russian Plat- form (Kagamonov & Donakova 1990) itratigraphical Scheme in the Middle Tien-Shan (Orlova, 1994, 1995) il a Brachiopods Foramìnifers Conodonts Ammonoids E a a ! o tr é-,- î; € :l Choristile.s bísu lcati/òrmís Chu'islile.s k,shemischensis Meekella eximia Pseudosta/fèl la oraegorsbi Idiognothodu.s s íttuostt,s Bilinguites - CanceÌloceras +l: ìÈitr;ì Pseutlostal/èÌla antiqu0 ii È{ qkt \ :ì< iù= È (n F::s \€ : !ì SÈ ì*:ì I {r -qs .tí |pirifer hisulccttus oroducttts roductifbrmìs Plectostulfel lct longísarla Plecto,stoffellu .otundu '). noduliferus 'd. cotugalus Reticuloceras - Ba,\hkorÍocerqs Plectosta//èlÌct iakhensis Plectostaf/el Ia vqrvartensls I a 5 Ls. vcntri- z F p ct) - c a I F' = c Beleutella mugna Plectostaf/èlla korsdklensis G. po,stbilineatus Fayettevìllect Delepinoceras )lectostc(fella miro tbtusa Eostallèlla Lffke.\tanica Gnathodus bilinedtus bollandensis s =î ;triatlera qngusl0 Eo,sìgmoilina explicota LoebÌichiq ninima - Plectostqf/èllu. orimilivcr +. È.ò ! I -'< 'F = Latíproducftrs re(le.tlrilr,\ Neoarchaedísctrs regularís Biseriellu purva Z a jig0nîoprodLtcÎus lrgqnleus Enclolhyranopsís c ra.\,so Parugnaîhodus nodosus H.vpergonialiles Ferganoceras f''i =:È ìi:l 188 O. C)rlov Labkouley and its ecological features (Rauzer-Chernousova 1960' 1967; Fomina 1969). The database consists of 1663 specimens (303 spe- cies). In order to evaluate the similarity of foraminiferal associations within the same facies or between differ- ent facies for each foraminiferal zone, we used quantita- tive Sorenson's Coefficients of Species Similarity - CSS (Odum 1971; Southwood 1928). Among the ten studied sections, five were representative; therefore, the coeffi- cients were calculated only for these sections: Koikebil- tau and Mashat (Talassic FT), Akkuiluk (Ugamic FT), llya - 60l7 (Karzhantauic FT) and Paltau (Paltauic FT) (Fig. 2). The Sorenson's Coefficients of Species Similarity is calculated with the followine formula: Tab. 1 - Comparison of Serpukhovian and Bashkìrian faunal zones between the Mìddle Tìen-Shan and Ur:l' - Ru..i:n Pl:rform (modified after Orlova 1994, 1995). css:2cl(A+B) where "C" is the number of species common to two sec- tions in a foraminiferal. zone, and "A' and "8" are the total number of species in each section within the fo- raminiferal zone. This index is designed to equal 1 (or i 00%) in cases of complete faunal similarity and O (or 0%) if the sites have no species in common. One of the great advantag- es of this method is its simplicity. The index is particu- larly useful for evaluating the similarity of two species lists (Magurran 1988). It has been applied, for example, in analysis of the biogeography of Devonian rugose cor- als (Naimark et al. 1998), and of the paleobiogeographic affiliation of Carboniferous faunas of the Qaidam Basin, China (Li 8*. Zhang 1999). r \ t Baikinsít0 100 ?0s 30G km KAU,A,KHS?ÀN Almaq. Carboniferows foraminiferal assemblages from C entral Asia t89 Fig. 1 - Location of studied Serpukhovian/Bashkirìan sections, Mid- dle Tien-Shan: Talassìc FT: 1 - Mashat, 2 - Koikebiltau, 3 - Djianisusai; Ugamic FT: 4 - Akkuiluk, 5 Yakhak; Pal- tauic FT: 6. Paltau; Karzhantavic FT Z River Uya - 60//, 8 - River Uya - 61/8,9 - River Uya - 69/9,10 - River Dje- girgen. FT - facies types. Facies types Marine sedimentation began around the Devonian - Carboniferous boundary in Middle Tien-Shan and persisted into the Serpukhovian and early Bashkirian (Fig. 3). Dif- ferences in lithological sequences testify to differences in topographic relief, tectonic movements and sedimentation within the basin (Osipova et. al.1971,; Fomina 1969). Talassic type The Talassic type contains shallow-water carbonate sediments from an inner marine shelf (Koikebiltau and Mashat sections). The Serpukhovian inter-val is character- izedby high-energy, near-shore to offshore facies, con- sisting of light gray, thick-bedded, ooid, crinoidal, algal - foraminiferal and brachiopodal limestone banks. These beds formed shoals. During the early Bashkirian near-shore, moderately agitated shallow- water environments prevailed, forming graiz, bedded, fine-grained and nodular limestone to ooid, algal - foraminiferal limestone Chert concretions abound at the top of sequence. Foraminifers such as Endothyranopsis, Omphalotis, Glo- boendothyra, Forshia, Eostffilla (Ikensieformis) and oth- ers represent eurobiontic and stenobiontic populations. The most diverse and highest density populations are ob- served in this facies. Ugamic type Tl"' I r^^*:^ *'^: is open, shallow marine carbonate sediment and represents accumulation on an outer car- bonate shelf platform (Akkuiluk and Yakhak sections). The carbonates are typically gray, bedded, fine-grained limestone. Continuous sedimentation and a relatively con- stant stratal thickness characterize the sequence. Shoal and intershoal sediments as well as up ro 1 m thick lens- es of calcareous breccia also occur. Chert, both concre- tions and bedded, appears in the middle part of the sec- tion. Fossils include conodonts and foraminifers as well as rare brachiopods. The foraminiferal association is characterized by a gradual increase in diversity during the Serpukhovian and into the lower Bashkirian. The high species diversity of the foraminifers contrasts with the low abundance of specimens except in offshore, shallow-water shoals that have high population density and species diversity. The population density increases from the bottom to the top of the sequence. Karzhantauic type The Karzhantauic type is a volcaniclastic and shal- low marine carbonate sequence, deposited in the Karzhan- tau Range ({Jya and Djegirgen River Basins). Serpukho- vian strata consist of massive-bedded tuffaceous con- glomerate and tuffaceous sandstone which are replaced westward by finer-grained terrigenous and detrital lime- stone. Continuous beds of limestone occur at the top. Foraminiferal diversity and abundance are high. Bashkirian, tuffaceous sandstone passes to the west into detrital foraminiferal limestone and interstratified tuff to the east. Upward, strata of trachytic tuffaceous conglomerate, foraminiferal sandstone and fossiliferous sandy limestone occur. The foraminifers have low diver- sity, but a high population density. Talas,t Alatau @ *Pn* c i.* Chirehik 15 S l$km Ch*tka 190 O. Orlov-Lableot,sky F;- ) - a^"'.1..;^- ^h."r of the main sections for the various facies and formations in the Serpukhovian / Bashkirian sections in the Middlel !b'_ Tien-Shan. Paltauic type The Paltauic type includes basinal carbonaceous- terrigenous sediments, characterized by thin-bedded, graded and laminated organic limestone with turbidite interbeds (Paltau section). The limestone contains admix- tures of sand and clay in the middle of the section. The sequence terminates with a limestone conglomerate and calcareous shale. The foraminiferal assemblage is charac- terizedby a gradual but insignificant increase in diversity and has a moderate population density. Foraminifers in- ch)de B is eriella p arua (N.Tchernysheva), N eoarchaedis cus regwlaris (Suleimanov) and M onotaxinoides priscus (Brazh- nikova & Yarzeva). Some species, such as Ompbalotis om- phalota (Rauzer-Chernousova Er Reitlinger) and Eostffil- la ihensis Vissarionova have thick shells and show traces of transportation. They appear in the late Visean, but disappear in the early Serpukhovian. Other fossils, such as conodonts, ammonoids, algae (Koninleopora) and bra- chiopods are also present but not abundant. Facies associations and similarity of foraminiferal zones Seroukhovian - lower Bashkirian foraminifers are moderately to highly abundant and highly diverse (from 40 to 160 species) depending on depositional environ- ments within the basins. Assemblages within foraminif- eral zones I - VIII (Fig. 3) show a gradual change in eostaffellid species and genera and other taxa. The number of species and genera found from the late Visean is sharp- Iy reduced. The Serpukhovian is characterized not only by the evolution of the family Eostaffellidae, but also by the appearance of sma1l foraminiferal genera such as Rec- toendotbyra, B iseriella, Globivaktulina, M onotaxinoides, representatives of the family Asteroarchaediscidae and others. The Sorenson's Coefficients of Species Similarity (CSS) values for foraminiferal zones I-VIII are presented in Table 2.They are based on comparisons between sec- tions in the same facies IKM in Table 2\ and from differ- ent facies (KA through PU in Table 2). In order to interpret the significance of the coef- ficient values, I separated them into five categories (Fig. 4): highest CSS at 85 -100 %; high CSS at 70 -85 "/"; moderately high at 55-70 "/". moderate ar 40- 55 o,o afld low at 25 -40%.The highest CSS records are from zones I (75% of total records) andII (25%); the high CSS are from zones II (20%),III (10%), ry (10%), VI (30%) and VII (30%); the moderately high CSS are from zones III Tr I (1 È ,J) -È {t} \ Facics typr' Talassic Ugamic Paltauic Karzhantauic ÀN scctiorr Koikebiltau Mashaf Akkuiluk Paltau Uya (60/7) g, U} d N f d v) lX - Pseudostaffella pruegorsnyai F lL : :\ a F. .J) Limcstonc n:edium and drin bedded at botlÒm" lìne grairred. ngdular arrd deirital rvith chelt concretioix. Limestone mediurr bedded finc grained nodular and detrilal with shells. alsal- fbraninilì:rs. ioids che{ rùncretiÒns. OE !:4 à Limestone drin and medium bedded. nodular Jine and micro grained ciayeyìnarly dehita liilltl F I : E Tmchyardesite rvith tuflaceous sandstone and sandstone YlIl - PseudosralJùlla 0t1tiqu0 YII - Pltctostqffelkt fongi''culu - P I e ctostaJfè I la ronmdo rIrgsionc lhrtk- I LLftilii tr 8"di -imeslone mediunr :edded, dotrital. ilgaf lìlraminifcral. roclular fine grained lith concretions md intcrlaycrs of :Ììen Tu{lrceous sandsto ne with limestone sandy. detritàI, furaninìfèru|, nodular, ooids ard iúerlayen of trachye Vl - Plectostufftlla .j nklrnsis - Pleuostof: .fèllu ,-onuriansis Z O f Trl ,"/) 6'a =-u a Y - Plectosnlfltlla karsaklensis 1l llfit E. t! G z J Tuffaccous cong- lonìemle and lnÈ Iàceous sandstone with Iinrestone sandy, defitàI, lbraminilèral, nodular and r:oids and thin bedrled with cnrsion sur- faces- Foraninifirs brachiopo85-100 <40>55 .25>40 categorÈ C arb oniferous foramintferal as s emblages from C entral Asia REFERENCES t93 Bensh F.R., Nigmadzanov I.M. & Iskandarkhodgaev T.A. (1998) - Stratigraphy of the Middle Tien-Shan. In: Geolog, ancl Useful Minerals of Uzbekistan. Nauka (FAN):95 -123. Tashkent (in Russian). Fomina E.Y. (1969) - The peculiarities of assemblages of fo- raminifers in varied facial deposits in Tarussian and Ste- shevian seas of Moscovian S1'ncline. Voprosiì Micropal- eontologii, 11: 18-34, Moskva (in Russian). Kagarmonov A. Kh. E Donakova L.M. (eds.) (199A) - Kamaen- niugolnaya sistema (Carboniferous System). In: Resheni- j a M ezbo e domst oenno go regionalnogo stratigraphicgeskogo sooeshanija pct srednemu í verhnemu paleozou Russleoi Plat- formi (Leningrad, 198B).95 pp., Leningrad (in Russian). Li Shou Jun & Zhang Hong. (1999) - Paleobiogeographic af- filiation of Carboniferous faunas of the Qaidam Basin, China. Acta Micropal. Sinica, 16 (2), 18i-189, Nanking (in Chinese with English abstract). Magurran A.E. (1988) - Ecological diversity and its measure- ment. Princeton Unioersity Press, New Jersey: 11.1 p., Princeton. Naimark E.B., Ulitina L.M. E Markov A. V (1998) - Quantita- tive analysis of the biogeography of Devonran rugoses. Paleontol. Zburnal. (6): 16-23, Moskva (in Russian). Nemirovskaya T.I. Ec Nigmadzanov I.M. (1994) - The Mid- Carboniferous event. Cour. Forsch. Inst. Sencleenberg, 68: 319-335, Frankfurt. Nikolaeva S.V & Nigmadzanov I.M. (1991) - New data about the age of the Khodzhirbulakskoj suite in connectlon with problems of the Lower and Middle Carboniferous boundary. B ul. Moskooskogo obshestva ispitatelei prirody. Otd. geol., t.65, n.1: 128, Moskva. (in Russian) Odum E. P. (1971) - Fundamentals of Ecology. 'MB. Saunders Company. 574 pp., Philadelphia. Orlova O.B. (1994) - The Serpukhovian and Bashkirian Stages of the Middle Tien-Shan. Recent data on the Paleozoic biostratigraphy of the Russian platform and folded areas of the Urals and Tien-Shan. VNIGNI; 58-59, Moskva lin Russian). Orlova O.B. (1995) - Stratigraphy and Foraminifera of mar- ginal deposits of the Lower and Middle Carboniferous of a *estern pan of rhe Charkal-Talass Mountain sys- rem. Srrmmarv of Ph D. Tashkent State Uniaersin.2S nn., Tashkent. (in Russian with English abstract). Orlov- Labkovsky O. (1999) - The Serpukhovian Stage in the Middle Tien-Shan Mountains (Uzbekistan and adjacent countries). Abstract. XIV Intern. Congr. Carbon. Permi- an,: IQ/, Lalgary. Orlov- Labkovsky ó. lzoor; - The Serpukhovian Stage in the Middle Tien-Shan Mountains (Uzbekistan and adjacent countries). In L. V Hills, C.M. Henderson, & E.W Bam- ber (Eds.) - Carboniferous and Permian of the Vorld. XIV Intern. Congr. Carbon. Permian. Mem. 19: 796- 801, Calgary. Osipova A.I., Hecker R.Th. & Belskaya T.N. (1971) - Peculiari- ties of distribution and changes of fauna in Late Visean and Early Namurian epicontinental seas of the Russian platf orm. Trw dii Pa le on o I o gi ch e s/eo go I n s tituta. I 3 0. I z d.a- telstto Akademii Naule:279-293, Moskva (in Russian). Rauzer-Chernousova D.M. (1960) - The criterion of the geo- graphical area in the systematics of Foramintlera. Pre- quaterndry micropal. Problem 6: 23-3L, Moskva (in Rus- sian). Rauzer-Chernousova D:M. {1962) - About zones of common and regional stratigraphical scales. Izvestiya,4N SSSR, Geologiya,T:1A4 - 118, Moskva (in Russian). Sergunkova O.I. (1989) - Cyclicity of the sedimentary accumu- lation of the Lower Carboniferous in the Chatkal -Ta- lass Basin in the Middle Tien-Shan (based on the analy- sis of brachiopods). In: Biostratigraphycal Researcbes in Uzbeleistan; 4-17 pp., Tashkent (in Russian) Southwood T.R.E. (1978) - Ecological methods. Chapman & Hall. A Halsted Press. 524 pp., London.