The Successi O N of Frasnian Conodont Assemblages in the Type Sections of the Southern Timan-Pechora Province (Russia)
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Bollettino delia Società Paleontologica Italiana Modena, Novembre 1999 The Successi o n of Frasnian Conodont Assemblages in the Type Sections of the Southern Timan-Pechora Province (Russia) Nonna S. 0VNATANOVA Alexei V. KuzMIN V.V. MENNER All-Russian Research Geologica! Institute of Geology and Oil Prospecting Institute (VNIGNI) Development of Combustible Fuel KEYWORDS- Conodonts, Biostratigraphy, Late Devonian, Timan-Pechora Basin, Russia ABSTRACT- A succession of 11 conodont assemblages, covering the entire interval of the Frasnian Stage, Upper Devonian, is established according to re{erence sectiom of Southern Timan (northeastern East European Piat{òrm). The conodont assemblages are correlated with the regional stages. 'rhe Lower Frasnian assembiages characterize shallow-water Lithofacies andare base d on the evolution o{Ancyrodella andPolygnathus. The Middle and Upper Frasnian assembiages are established in the sections ofslope and basinallithofacies, with palmatolepids prevaiiing. The leve!s of the greatest changes of conodont assembiages are determined. Problems, arising in correiating the Timan-Pechora succession with the Standard Frasnian conodont Zonation, as well as with the Montagne No ire zonation, are discussed. RIASSUNTO- [La successione delle associazioni a conodonti frasniani nelle sezioni tipo della parte meridionale della Privincia del Timan-Pechora (Russia)] -Nelle sezioni di riferimento del Timan meridionale (parte nord-orientale delia Piattaforma dell'Est europeo) viene individuata una successione di undici associazioni a conodonti, che coprono l'intero Frasniano, Devoniano superiore. Tali associazioni sono correlate con le unità cronostratigrafiche regionali. Le associazioni dei Frasniano inferiore sono tipiche di ambienti di acqua bassa e sono basate sull'evoluzione dei generi Ancyrodella e Polygnathus. Le associazioni del Frasniano medio e superiore sono invece di ambiente di scarpata o di bacino, con una prevalenza di palmatolepidi. Sono stati individuati i Livelli corrispondenti alle maggiori variazioni nelle associazioni a co nodo nti. Véngono discussi i problemi legati al tentativo di correlare La successione del Timan-Pechora con La Biozonatura Standard del Frasniano e con La biozonatura delia Montagne No ire. INTRODUCTION Pechora conodont assemblages with the standard Frasnian Zonation was not always possible. It was The Timan-Pechora (TP) Basin occupies the necessary to develop a detailed stratigraphic succession northeastern margin of the East European Platform. It of local Frasnian conodont assemblages, assigned to is located between the Timan Ridge and the Urals. the regional stratigraphic chart, and to correlate these Various Frasnian lithofacies are developed here: terri- with the current zonal scales. This paper deals with the genous and carbonate-day deposits of shallow-water stratigraphic succession of conodont assemblages in shelf, reefs, banks, sediments of deeper intra - shelf sections of mosdy deep-water deposits (Palmatolepis basins - bituminous thin-bedded carbonate and biofacies), except for the lowermost beds of the Frasnian siliceous-carbonate rocks of "domanikoid" type, day Stage, where it is represented only by the polygnathid and carbonate sequences of shallow shelflateral growth. biofacies. T o study this, the sections ofboreholes (l 003, The Frasnian conodont assemblages are represented by 1B, 3B, 2023, 2068) and ourcrops (in the Ukhta, shallow-water - polygnathid - and deep-water (slope Yarega, Chur', Domanik, Lyaiol, and Vezha-Vozh and depression facies) - palmatolepid- biofacies. The rivers) in the Ukhta Region, Southern Timan, were standard Frasnian conodont zonation (Ziegler, 1962, chosen (Text-fig. 1). These include the stratotypes of 1971) has been used in the region (Ovnatanova, 1978; most of rhe Timan Frasnian regional stages. Consi- Ovnatanova & Kononova, 1984; Khalymbadzha, derable parts of the sections are composed of basinal 1981; Ovnatanova & Kuzmin, 1991; Menner et al., (domanikoid) facies rocks with rich conodont 1992, Khruscheva & Kuzmin, 1996) fora long time, assemblages. The uppermost Frasnian Stage is with inconsiderable changes in the lower Frasnian, represented all over the Ukhta region by shallow-water where the local zones, Ancyrodella rotundiloba (= Lower sulphate-clay-carbonate deposits with scarce conodonts asymmetrica) and Polygnathus timanicus (= Middle + (Polygnathus biofacies). To characterize the succession Upper asymmetrica), were established. Those, who use of conodont assemblages in this interval, the data on the revised version of the zonation (Ziegler & Sandberg, conodonts from slope and basinal facies deposits, 1991), encounter difficulties that are due to the exposed in boreholes of the adjacent Tebuk-Viss peculiari ti es of facies of the section in the lower Frasnian Region, which is situated 60 km northeast of the town Stage, as well as to the diagnosis and range of the zonal ofUkhta, were used. species, Palmatolepis hassi Muller & Muller, Pa. jamieae Thus, a succession of conodont assemblages, Ziegler & Sandberg. Direct correlation of Timan - covering the entire Frasnian Stage (TP-1-XI), correlated 350 NS. OVNATANOVA, A. V KUZMIN, VV MENNER fs Geologica! boundary 1356 Outcrop o 3B Well sections t>.d Quarry Outcrop of reef massifs --1-- Axis of the Ukhta anticline 03-f-tm2 Upper Timan member 03-f-ujr Ust -yarega formation 0 3-f-dm Domanik formation 03-f-vt Vetlasyan formation 03-f-src Syrachoy fm 03-f-uk Ukhta fm 03-f-11 Lyaiol fm 0 3-fm1-izh lzhma fm 03-f-sd Sedyu fm 03-f-ev2 Upper Evlanovian Reef massifs 03-f-dom-ev, Domanik - Lower Evlanovian 0 3-f-src-ev, Syrachoy - Lower Evlanovian 1 -13 - Outcrop, quarries of Domanik formation O 2 4km with Conodont dates near Ukhta town '---L..-..1 Texr-fìg. l - The geologica! map of che Ukhra Region. Inset map shows location of Ukhra city as well as Bagan and Tebuk-Vis regio ns. Timan and Ust-Yarega formations ourcrops a t che area of che Vodny Setdement - Yarega River. Outcrops A, B, C(= 18, 13A, and 14 in Yudina & Moskalenko, 1997); Outcrop A(= 18) -righe bank of che Ukhra River, 0.3 km below che Neft iol' Creek mourh; Ourcrop B (= 13A)- righe bank of che Ukhra River, 0.8 km below che Polovinnyi Iol' Creek mourh; Outcrop C(= 14) -righe bank of che Ukhra River, 0.5 km above che Yarega River mourh; Ourcrop D (= 16k in Yarskov & Kuzmin, 1992) -righe bank of che Yarega River, righe triburary of che Ukhra River, at 3.3 km from the mourh; Ourcrop E(= 16 in Yudina & Moskalenko, 1994)- Vodny Serdement area, righe bank of che Yarega River, righe rributary of che Ukhra River, at 3.0 km from che mouth; 1-13 - che srudied by conodonts outcrops and quarries of rh e Domanik Formation near che rown of Ukhra. Ourcrop l (= outcrop 7 in Yudina & Moskalenko, 1994) - che lefr bank of che Chur' River, rributary of che Ukhra River, immediarely above che new highway bridge; Ourcrop 2 (= 15b in Bogoslovskyi, 1969)- che Chur' River, righe bank, ar 5.5 km above che highway bridge; Ourcrop 3 (= 15c in Bogoslovskyi, 1969)- che Chur' River, righe bank, at 2-3 km above che bridge; Outcrop 4 (= 28) -che Chur' River mourh, lefr bank; Outcrop 5- "Bogarskogo" quarry; Outcrop 6- che quarry at che old road ro che Chur'River; Outcrop 9 (= outcrop 39 in Bogoslovskyi, 1969) -lefr bank of che Ukhra River, at 500m below che Krokhal' Creek mourh; Ourcrop lO - lefr bank of che Domanik River, tributary of che Ukhra River, quarry, 0.5 km from the mourh; Ourcrop 11 (= 21 in Yudina & Moskalenko, 1994)- righe bank of che Domanik River, 0.5 km from che mourh; Ourcrop 12 -lefr bank of che Ukhra River, at che hospiral of Shudayag Serdement; Ourcrop 13 - road and warer inrake cuts above Shudayag Serdement, lefr bank of che Ukhra River. FRASNIAN CONODONTS FROM EASTERN RUSSIA 351 with local and regional units of the TP Basin, was sections studied in this paper, is shown in the legend developed. W e consider this a preliminary stage in the to Text-fìg. l. development of a local conodont zonation . Moreover, Seven regional stages are distinguished in the TP an attempt was made to preliminarily correlate the local Frasnian deposits (upwards): Timanian, Sargaevian, assemblages with the standard Frasnian zonations: Domanikian, Vetlasyanian, Sirachoyian, Evlanovian, former (Ziegler, 1962, 1971) and revised (Ziegler & and Livnyian. In the shallow-water facies sections, the Sandberg, 1990), and with the Montagne Noire Sargaevian Regional Stage is correlated with the Ust'- zonations (Klapper, 1989; Klapper & Foster, 1993). Yarega Formation, the Evlanovian and Livnyian Regional Stages - with the Ukhta Formation. In the slope and basinal facies deposits, the Vetlasyanian, STRATIGRAPHIC SETTING Sirachoyian, and lower Evlanovian Regional Stages are correlated with the Lyaiol Formation, the middle The Frasnian stratigraphy of Southern Timan is Evlanovian stage - with the Sed'yu Formation. discussed in a number of publications (Lyashenko, 1956; Fokin, 1977; Kushnareva & Raskatova, 1980; Khalymbadzha, 1981; Menner et al., 1992; Ovnata- CONODONT FAUNA nova, 1978; Ovnatanova & Kuzmin, 1991; Kuzmin, 1995, 1998; Kuzmin & Ovnatanova, 1989). Severa! The Timan an d Ust'-Yarega Formations (Timanian most important Frasnian outcrops of the Ukhta and Sargaevian Regional Stages) in the Ukhta Region Frasnian deposits are described in the Guide (Yudina are composed of the shallow-water facies deposits - & Moskalenko, 1997). Their correlation with the siltstone and day with rare limestone beds, containing Cl) ·;;, '§ ·;:"' Cl) " "' Cl) Gi >o "i :l E u; C> u E o 1: Cl) ,., Cl) ·=1ii o Cl) "'o 'C Outcrop E Outcrop l .c C'· 'ti " "' o - < :Iii :E :E :E :E :E Il. Il. Il. Il. Il. Il. Il. i: Il."' --'--'---" < < < .2 ..Q) l 1ii .c . E Q. o E Q) o - 52{- - - Q) - - - c. l c. ::l 2-:-:-. - l-----ì- Outcrop D Q) v E"' 'ti "' 'C Outcrop C i- : -_ .• iii 1ii ::l .. 12-14 Q) il' 10-!J o ...J 4-5 2-3 l - - - Outcrop B - --. 4 -----·- - - ..Q) 1: c. 3 =·=·-· • c. 1-2 --::-:- "'E ::l i= Outcrop A - 01 Eh 15:94 mc - B3 Text-fig. 2 - Distribution of key Conodont species in che Timan and Ust - Yarega Formation sections.