Geo log i cal Quar terly, 2016, 60 (2): 473–492 DOI: http://dx.doi.org/10.7306/gq.1290

The Stebnyk For ma tion (Mio cene) in the -Pokuttya and nappes of the Ukrai nian Carpathians: a re cord of en vi ron men tal change in the Carpathian Foredeep

Nestor OSZCZYPKO1, Alfred UCHMAN1, * and Ihor BUBNIAK2

1 Jagiellonian Uni ver sity, In sti tute of Geo log i cal Sci ences, Oleandry 2a, 30-063 Kraków, Po land 2 Ivan Franko Na tional Uni ver sity of , Geo log i cal Fac ulty, Hrushevskyi 4, 79005 Lviv,

Oszczypko, N., Uchman, A., Bubniak, I., 2016. The Stebnyk Forma tion (Mio cene) in the Boryslav-Pokuttya and Sambir nappes of the Ukrai nian Carpathians: a re cord of en vi ronmen tal change in the Carpathian Foredeep. Geolog i cal Quarterly , 60 (2): 473–492, doi: 10.7306/gq.1290

The late Early–Middle Mio cene Stebnyk Forma tion is a ~600–2000 m thick unit of the Boryslav-Pokuttya and Sambir nappes, which con tains a molasse suc ces sion of the Carpathian Foredeep in cor porated within the marginal part of the Outer East ern Carpathian accretionary wedge. In the val ley of the River, be tween and , the Stebnyk For ma tion over - lies the al lu vial fan de pos its of the Sloboda Con glom er ate and the deltaic depos its of the Dobrotiv Forma tion in the south, and the la goonal salty clays of the Vorotyshcha Forma tion in the north. The Stebnyk Forma tion is built of mainly rose, green- ish and grey calcar eous mudstones inter ca lated with sev eral vari able sand stone beds, in clud ing thick-bedded pack ages. The oc cur rence of tetrapod footprints and rain drop im prints, as well as the overall red-bed char ac ter reflect pre vail ing con ti - nental con di tions dur ing de posi tion of the forma tion, which is in terpreted as sed i ments of a delta plain with distributary chan - nels infilled with thick sand stone beds and as so ci ated with inter ca la tions of thin ner beds referred to channel lev ees and cre vasse splays. The upper part of the Stebnyk Forma tion con tains ma rine microfossils of the NN4 Zone, and lo cally of the NN5 Zone, corre spond ing to the Early Badenian trans gres sion in the re gion. On a regional scale, the Stebnyk For ma tion shows a polar ity of facies, with a large con tri bution of con glom erates and thick-bedded sand stones in the lower part in the north-west and fin ing to the south-east, with trans port from the west and north-west. The sedi ments ac cu mu lated in an elon - gated sub sid ing zone be tween the rising Carpathian orogen and the forebulge el eva tion of the foreland, in warm and semi-dry cli ma tic con di tions cor re spond ing roughly to the Mid dle Mio cene Cli ma tic Op ti mum. The ac cu mu la tion was bal - anced by a subsi dence caused by sink ing of the plat form slab and by sedi men tary load ing.

Key words: non-marine, delta plain, molasse, Mid dle Mio cene Cli ma tic Op ti mum, Carpathian Foredeep, Ukraine.

INTRODUCTION ever, its depositional palaeoenvironment has never been sub - ject to closer anal ysis. The aim of this pa per is: 1) to de scribe facies fea tures of the The Stebnyk For ma tion (Early–Middle Mio cene) is a char - Stebnyk For ma tion in the val ley of the Prut River, betw een ac ter is tic lithostratigraphic unit of the Boryslav-Pokuttya and Lanchyn and Deliatyn, as well as in the western bank of the Sambir nappes of the Outer East ern Carpathians in Ukraine. Bystrytsia Nadvirnanska River near (Fig. 1), and 2) to Ac cord ing to Tołwiński (1950), the Stebnyk For ma tion, be tween in ter pret the palaeoenvironmental con di tions of this for ma tion in Przemyśl (Po land) and in Ukraine (ca. 200 km) oc - the con text of the foredeep basin evo lu tion and with ref er ence curs in a belt up to 20 km wide; it be came abruptly narrow er to to pre vi ous pub li ca tions on the un der ly ing de pos its (Oszczypko the south-east, down to ~250 m at the Rybnytsia Val ley near et al., 2012, 2014). The best ex po sures, char ac ter ized by good . Its de pos its, dom i nated by var ie gated marly mudstones con ti nu ity and cov er ing al to gether the whole for ma tion, have in ter ca lated with sand stones, with sig nif i cant con tri bu tions of been se lected for these stud ies. Fur ther more, a review of re - con glom er ates in the west, typi cally as red beds, and showing search into the Stebnyk For ma tions is com piled, be cause of its ev i dence of ma rine in flu ence in its upper part, re cord a sig nif i - long and com plex his tory of study and dis persal in the lit er ature. cant change in depositional palaeoenvironment dur ing the fi nal stage of devel op ment of the In ner Carpathian Foredeep. How - GEOLOGICAL SETTING

Along the mar ginal part of the Ukrai nian Carpathians, a * Corresponding author, e-mail: [email protected] wide zone of folded Mio cene de pos its be longs to the Boryslav - Received: February 3, 2016; accepted April 2, 2016; first published -Pokuttya and Sambir nappes (Fig. 1B, C). The Boryslav - online: April 12, 2016 -Pokuttya Nappe, known also as the Mar ginal Fold Unit or the 474 Nestor Oszczypko, Alfred Uchman and Ihor Bubniak

Fig. 1. Lo ca tion maps A – posi tion of the study area in the Alpine-Carpathian system (after Picha, 1996, mod i fied by Oszczypko et al., 2006); B – tec tonic map of the Ukrai nian Carpathians (af ter Ślączka et al., 2006, sim pli fied); CF – Carpathian Foredeep, CZ – Chornohora Nappe, MA – Magura Nappe, MK – Marmarosh Klippen Zone, MR – Marmarosh Mas sif, PK – Pieniny Klippen Belt, RA – Rakhiv Nappe, TC – Trans-Carpathian Depres - sion, WH – Vihorlat-Gutin Vol ca nic Mas sif; C – geo log i cal map of Deliatyn-Lanchyn-Nadvirna area (after Matskiv et al., 2009, sim pli fied), showing lo ca tion of sec tion D and the study area; D – geo log i cal sketch-map along the Prut River show ing lo ca tion of the cross-sec tions 1–2, 3–4, and sec tions A–E (the map partly af ter Bujalski, 1938) The Stebnyk Formation (Miocene) in the Boryslav-Pokuttya and Sambir nappes of the Ukrainian Carpathians 475

Boryslav-Pokuttya Folds, is exposed in a nar row (up to 20 km) belt lo cated be tween the Skyba () and Sambir nappes. This nappe is traced from Roma nia in the SE up to the Pol ish bor der in the NW. It is built of a com plex set of super im - posed thrust sheets (Koltun et al., 2005). The Boryslav -Pokuttya Nappe, com posed of flysch and mo lasse de pos its, de scends be neath the fron tal Carpa thian overthrust of the Sambir Nappe, which com prises ex clu sively molasse de- pos its. Strata of the Boryslav-Pokuttya and Sambir nappes rep re sent the deformed part of the in ner Carpathian Foredeep, which is thrusted over the Mid dle Mio cene (Badenian and Sarma - tian) autochthonous de pos its of the Bilche - -Volytsia Zone rest ing di rectly on the foreland plat form base ment (Burov et al., 1978; Smirnov et al., 2000).

BORYSLAV-POKUTTYA NAPPE

This nappe is sub di vided into the Deliatyn and Runhury Sloboda sub-nappes (Kulchytsky et al., 1997; Matskiv et al., 2009). The Deliatyn Sub - -nappe is com posed of Cre ta ceous–Lower Mio - cene flysch, which is sim i lar to that of the Skyba Nappe. The youngest Lower Mio cene flysch suc - ces sion be longs to the Polanytsia For ma tion, which is over lain by the Vorotyshcha For ma tion (NN3–?NN4 Zone; An dre yeva-Grigorovich et al., 2008a). The Voro tyshcha For ma tion, up to 700 m thick, com posed of grey mudstones-siltstones in- ter ca lated with coarse -grained sand stones and con glom er ates, con tains large blocks of im pure ha - lite and anhydrite (Tołwiński, 1950; Gurzhyi, 1969; Andreyeva-Gri gorovich et al., 2008a). Lo cally, the mid dle and up per parts of the Voro tyshcha For ma - tion are replaced by the Sloboda Con glom er ate and Dobro tiv For ma tion (Oszczypko et al., 2012, 2014 and ref er ences therein; Fig. 2). The Deliatyn Sub-nappe, overthrusted upon the Runhury Sloboda Sub-nappe, is built mainly of de pos its of the Sloboda Con glom er ate (Oszczy pko et al., 2012), Dobrotiv For ma tion (Oszczypko et al., 2014) and the Stebnyk For ma tion (this pa per). Sev - eral bore holes showed that the Sloboda Con glom - Fig. 2. Lithostratigraphic scheme of the Boryslav-Pokuttya and Sambir er ate is un der lain by the Vorotyshcha For ma tion, nappes in the study area (based on Oszczypko et al., 2014, sup ple mented) which over lies flysch de pos its of the up per part of Sd – Sadzhavka Sand stone the Menilite and Polanytsia for ma tions, rep re sen - ted mainly by olistoliths, olistostromes, and olisto- plaques (Kolodiy et al., 2004). In the south ern limb of the Runhury Sloboda Anticline, the Andreyeva-Grigorovich et al., 1995, 1997, 2008a, b). On the Sloboda Con glom er ate is un der lain by the Menilite For ma tion north ern limb of the Runhury Sloboda Anticline, at Jabloniv, (Oligocene), and in its north ern limb by salt clays of the Voro - gypsum-bear ing beds up to 100 m thick are sand wiched be - tyshcha For ma tion (Tołwiński, 1950). The Sloboda Con glom er - tween the Sloboda and Dobrotiv for ma tions (Tołwiń ski, 1950). ate con tains ex otic blocks, boul ders and cob bles of Up per Pro - A fun da men tally dif fer ent strati graphic scheme of the tero zoic–Lower Pa leo zoic green phyllite, black schist, dolo mite, Boryslav-Pokuttya Nappe was pro posed by Smirnov (2003). In Ju ras sic white lime stone and rare, flysch-de rived olistoliths and his in ter pre ta tion, the Boryslav-Pokuttya suc ces sion be gins olistostromes (Fedushchak, 1962; Oszczypko et al., 2012). The with the up per part of the Menilite For ma tion (Eggerian), which thick ness of the Sloboda Con glom er ate in creases from is fol lowed by the Polanytsia For ma tion (Eggenburgian) with the 450–500 m in the Nadvirna area up to 1400 m at Runhury Rushor Con glom er ate at its base, and is ter mi nated by the Sloboda. The Sloboda Con glom er ate passes into the mud - Vorotyshcha For ma tion (Ottnangian) with the Con - stones, siltstones and sand stones of the ?Ottnangian Dobrotiv glom er ate at its base. In this in ter pre ta tion, the Mio cene de pos - For ma tion, which is up to 800 m thick. This for ma tion is fol lowed its of the Sambir Nappe begin with the Sloboda Con glom er ate by the Stebnyk For ma tion (Karpatian–Lower Bade nian; see (Eggerian), which is fol lowed by the Dobrotiv For ma tion 476 Nestor Oszczypko, Alfred Uchman and Ihor Bubniak

(Eggen burgian/Ottnangian). These de pos its pass upw ards into The over ly ing Balych For ma tion passes upw ards into the the un di vided Kalush suc ces sion, which is up to 2000 m thick For ma tion (Andreyeva-Grigorovich et al., 1997). (Ottnangian–Mid dle Badenian). Its lower part is com posed of In the Kalush area, the Stebnyk and Balych for ma tions are un di - the Stebnyk fa cies (rose and var ie gated, marly mudstones and vided and they pass up wards into the Bohorodchany Forma - sand stones) fol lowed by grey and “blue de pos its” of the Balych tion, which is com posed of 100–250 m thick, grey marly mud - fa cies. This suc ces sion is ter mi nated by the Kalush salts and stones and sand stones. They contain rich Badenian plank tonic gyp sum de pos its. foraminifera and cal car e ous nannoplankton of the NN5 Zone (Andreyeva-Grigorovich and Kulchytsky, 1985; Andreyeva- -Grigorovich et al., 2003). In the Kalush area, the undi vided SAMBIR NAPPE Stebnyk and Balych for ma tions are fol lowed by salt depos its of the Kalush For ma tion. This for ma tion is con tem po ra ne ous with The Sambir Nappe, up to 24 km wide and com posed of sev - the Wieliczka (Po land) and Tyras evaporitic for ma tions (Bilche - eral thrust-sheets (Fig. 1), is cor re lated with the Sub-Carpathian -Volytsia Zone, Ukraine) be long ing to the NN5/NN6 zones Unit in Ro ma nia and the Stebnik Unit in SE Po land (Oszczypko (Andreyeva-Gri gorovich et al., 2003; Fig. 2). et al., 2006, 2008). This unit is thrusted over the Badenian - Near , in the NW part of Sambir Nappe, the youn- -Sarmatian de pos its of the outer Carpathian Foredeep (Kolodiy gest de pos its be long ing to the Kosiv (Up per Badenian) and et al., 2004). The Sambir Nappe succes sion is com posed (Sarmatian) for ma tions have been doc umented. The mainly of a thick suc ces sion of the “lower” Mio cene molasse of Dashava suc ces sion (Berezhnytsia For ma tion af ter Hnylko, the Stebnyk and Balych for ma tions. The lithostratigraphy of its 2014) is ter mi nated by the Radych Con glom er ate, which con - basal part is still un der dis cus sion. Sev eral au thors (Koltun et tains flysch clasts. The age of these depos its is dated to the al., 2005; Andreyeva-Grigorovich et al., 2008b and ref er ences NN6–NN9 zones (Andreyeva-Grigorovich et al., 2008a). therein) re gard the Vorotyshcha For ma tion as the old est di vi - sion of the Sambir Nappe suc ces sion. This opin ion is sup ported by data from bore holes, e.g. 1 near Nadvirna, and Urych PREVIOUS WORK 6 (NE of the Boryslav), where the Vorotyshcha For ma tion was pen e trated (Andreyeva-Gri gorovich et al., 1997, 2008a). Paul and Tietze (1877: p. 68) men tioned red clays as so ci ated Coarse clastic depos its of the Sloboda Con glom er ate and the with salt clays betw een Nadvirna and Deliatyn, which have also mudstone-sand stone Dobrotiv Formation oc cur in this unit in a been called “red clays” (Zuber, 1882), “red shales” (Zuber, 1888, re sid ual form. In the Prut Val ley, the last large ex po sures of the 1915; Cizancourt, 1925; Bruderer, 1926), “shales with lay- Sloboda Con glom er ate and Dobrotiv For ma tion are pres ent be - ers/beds of sand stones” (Zuber, 1882, 1883; Świderski, 1925), tween the Oslava and the Chorna rivers, which are the red “septarian beds” and “rose marls” (Jabłoński, 1923), “Mio- right-side trib u tar ies of the Prut River. An expo sure of the lat est cene red shales” (Jabłoński and Weigner, 1925) or “var ie gated for ma tion sev eral tens of metres long is also known from the marls” (Bujalski, 1930). Tołwiński (1927) dis tin guished them as Prut River banks close to the Lanchyn bridge (Figs. 1 and 3A, the Stebnyk Beds, but he used also the term “rose marls” or “var- see also Bujalski, 1934; Andre yeva-Grigorovich et al., 2008a; ie gated marls” (see also Tołwiński, 1937). Kha dykin and Shakin Oszczypko et al., 2012, 2014). (1976) used the name Stebnyk For ma tion and this name was The Dobrotiv For ma tion is fol lowed by varie gated marls, used in the later lit er ature. The Stebnyk For ma tion was char ac - mudstones and sand stones of the Stebnyk For ma tion (Karpa - ter ized by almost all the Pol ish and Ukrai nian ge ol ogists working tian–Mid dle Badenian; Andreyeva-Grigorovich et al., 2008a). in the study region (e.g., Zuber, 1888, 1915, 1918; Teisse yre, 1927; Bujalski, 1930, 1934, 1938; Tołwiński, 1950; Vialov, 1951, 1960, 1965, 1966; Gurzhyi, 1969 and ref er ences therein), who fo cused mainly on its strati graphic po si tion, li thol ogy and palaeontological features. In Ro ma nia, the Ste bnyk Forma tion coun ter parts are known in the Mar ginal Fold Unit and the Sub-Carpathian Unit as the Hirja and the Magiresti beds, re spec - tively (Micu, 1982). The Stebnyk For ma tion is dis tin guished also in SE Po land (un der the name Stebnik Beds) in the pro lon gation of the Sambir Nappe, which is called here the Stebnik Unit (Głowacki et al., 1966; Ney, 1968; Ney et al., 1974; Garecka and Olszewska, 1997; Olszewska, 1999 and ref er ences therein). The most de tailed descrip tions of the Stebnyk For ma tion are given by Teisseyre (1927), Tołwiński (1927, 1950), Bujalski (1934), Vialov (1965), Gurzhyi (1969), and Khruschov and Kompanets (1988). Vialov (1965) pro posed that the transi tion be tween the Dobrotiv and the Stebnyk for ma tions is grad ual and the bound ary is conven tion ally proposed at the base of the first “rose marls”, while the bound ary betw een the Stebnyk For- ma tion and the over lying Balych For ma tion at Sadzhavka in the Prut Val ley is at the base of a 40 m thick suc ces sion com posed Fig. 3. Views of expo sures of the Stebnyk For ma tion of poorly ce mented, mas sive sand stone beds (up to 5 m thick) in ter ca lated with grey, green-grey and rose calcar eous mud - A – expo sures along the Prut River be tween Dobrotiv and Lanchyn stones, dis tin guished as the Sadzhavka Sand stone (Berlya- (sec tion B); view down the river; B – large expo sure along the left vskiy in Vialov, 1951, 1965). Vialov (1965) re garded these bank of the Bystrytsia Nadvirnanska River at Nadvirna (sec tion D); sand stones as the “northern fa cies” of the up per part of the in verted beds in an antiformal syncline; mea sured sec tion E in di - cated by a series of bars Stebnyk For ma tion, and Gurzhyi (1969) as the up per part of the The Stebnyk Formation (Miocene) in the Boryslav-Pokuttya and Sambir nappes of the Ukrainian Carpathians 477

Stebnyk For ma tion. Dif fer ent thick nesses of the for ma tion are bar ite and glauconite can be pres ent (Koltun in Vialov, 1965). re ported in the lit er a ture: 1000–1500 m (Tołwński, 1927), Teisseyre (1939) noticed phyllite grains in the sand stones. 600–2000 m (Gurzhyi, 1969), 500–1000 (Hnylko, 2004), up to Coarse sand stones con tain up to 30–40% lithic grains, in ter - 1200 m in SE Po land (Ney et al., 1974), or 800–1200 m in the preted as ev i dence of short trans por ta tion. The ce ment can Boryslav-Pokuttya Nappe and 500–1000 m in the Sambir con sti tute 10–50% of the rock; it can be cal car eous-clayey (up Nappe (Andreyeva-Grigorovich at al., 2011). to 40–45% CaCO3) to noncalcareous clayey (Gurzhyi, 1969). In the study area, Cizancourt (1925) dis tin guished three fa - The Stebnyk For ma tion con tains some in ter ca la tions of cies types in the Stebnyk For ma tion (his “red shales”): dacite tuffites, the thick ness of which oscil late from 10 to 25 cm – the Strutyn type: brick-col oured or choc olate-r ed marls, in the Nadvirna sec tion (Gurzhyi, 1969). At Seredniy Maydan rich in mica, with in ter ca la tions of grey-greenish sand - near Lanchyn these rocks (Bujalski, 1934, 1938) are 8–10 m stones and “traces” of gypsum; thick (Vialov, 1965). Two beds of dacite tuffite at Krasna, 3.5 km – the Nadvirna type: micaceous, vine-red shales in ter ca - NE of Dobrotiv (Kamieński, 1936) reach 20 m and 40–45 m in lated with cross-bed ded, micaceous sand stones, which thick ness (Vialov, 1965). The sand stones of the Stebnyk For- are 10–50 cm thick; ma tion (e.g., at Deliatyn, Nadvirna and Lanchyn) are known – the Petranka type: 20–100 cm thick beds of sandy, from the pres ence of cop per min er ali sa tion (that at Nadvirna micaceous, red-greenish or rose marls, with com mon was known al ready to Paul and Tietze, 1877, and to Zuber, green ish spots, gyp sum crys tals, lo cally with in ter ca la - 1882, 1885, 1888, 1915), which may cor re spond to layers rich tions of cross-bedded sand stones. in plant de tri tus (Gurzhyi, 1969). Vialov (1965) and Gurzhyi (1969) noticed a lat eral fa cies Var ie gated mudstones in the up per part of the Stebnyk For- change in the Stebnyk For ma tion more widely, with a sig nif i cant ma tion con tain foraminifers of the Porosonanion insignis Zone con tri bu tion of con glom er ates (Vyrva River facies, ac cord ing to (Vialov, 1965; Pishvanova, 1969) and other Mio cene taxa (Gło- Vialov, 1965) and thick-bed ded sand stones in the north-west, wacki et al., 1966) which, together with nannoplankton, point to which be came thin ner and rarer to ward the south-east, and with the Late Karpatian–Early Badenian (NN4 Zone; Andre yeva- a tran si tion to more clayey fa cies with more fre quent oc cur - -Grigorovich et al., 1997) and lo cally to the Mid dle Badenian rences of gypsum, with salt lenses (e.g., the pot ash salts at (NN5 Zone), sug gest ing a diachronous boundary with the over - Kalush), and fi nally with the salty shale “blue (Lanchyn) fa cies” ly ing Balych For ma tion (Andreyeva-Grigorovich et al., 2008a). fur ther in this di rec tion, sim i lar to the salt-bear ing Vorotyshcha Lat eral tran si tion be tween these for ma tions had been sug - For ma tion. Zuber (1883) had re ported that the red shales are gested al ready by Bujalski (1930) who placed the Balych For- partly re placed by grey green shales to the south-east. Vialov ma tion within the up per part of the Stebnyk For ma tion. Fora - (1965) and Gurzhyi (1969) con sid ered the Dubnik Con glom er - minifers (see also Głowacki et al., 1966; Łuczkow ska in Ney, ate in the Stebnik Unit in SE Po land as the lowest part of the 1968) and nannoplankton of the NN4 Zone have also been Stebnyk For ma tion. Con glom er ates are known from the lower found in the up per part of the Stebnyk For ma tion in the Stebnik part of the Stebnyk For ma tion from bore holes south of Unit in SE Po land (Garecka and Olszewska, 1997). In the mid - Przemyśl in SW Po land (Gło wacki et al., 1966). In the bore - dle part of the for ma tion, al gae (Characea) and ostracods holes -1 and Chyzhky-1 (both very close to the (Loxoconcha dromax Liventul) oc cur; sponge spicules, Pol ish bor der), a thick con glom er ate (255 m and 550–600 m, radiolaria or echinoid spines, which can be found in some ho ri - re spec tively) oc curs at the base of the Stebnyk For ma tion, with zons, are prob a bly re de pos ited (Vialov, 1965; Gło wacki et al., thin ner pack ages of con glom er ates higher in the for ma tion 1966). In some borehole, Gurzhyi (1969) re ported a few centi - (Gurzhyi, 1969; Burov et al., 1976; Khadykin and Shakin, metre-thick lime stone in ter ca la tions, which con tain frag ments 1976). The con glom er ates con tain ma te rial both from the plat - of foraminifers, radiolaria, cri noids, and sponge spicules. form (mainly phyllites) and from the flysch of the Carpathians. Sev eral au thors re ported sed i men tary struc tures and other The fa cies changes are re lated to changes in palaeo - sed i men tary fea tures in the Stebnyk For ma tion, which were morphology (Vialov, 1965). These views must be cor rected ac - sum ma rized by Vialov (1965), Gurzhyi (1969) and Khrushchov cord ing to newer strati graphic re searches (Andreyeva- and Kompanets (1988). They in clude cross-bed ding (no ticed -Grigorovich et al., 2003, 2008a, 2011), which shows that the al ready by Cizancourt, 1925), the len tic u lar char ac ter of some pot ash salts at Kalush are dis tinctly youn ger (Up per Badenian, sand stone beds (1.5–2.0 m long, 15–20 cm thick; Vialov, 1965), NN6 Zone) than the Stebnyk For ma tion. Also, Garlicki (1973) amal gam ation of beds, the pres ence of rip ple marks, mud - did not find any salt de pos its in the Stebnyk For ma tion south of cracks, rain drop im prints, sand dykes and con cre tions (small Przemyśl in SE Po land. Ac cord ing to Ney (1968) and Ney et al. cal car e ous con cre tions of septarian type – see Tołwiński, 1927; (1974), the Stebnik Beds (= Stebnyk For ma tion) in SE Po land cal car eous con cre tions up to 0.5 m across – see Gurzhyi, are up to 1200 m thick; in the lower part (500 m), they com- 1969). Khrushchov and Kompanets (1988) dis tin guished four posed mostly of sandstones, com monly cross-lam i nated, with dif fer ent fa cies re ferred to the Stebnyk For ma tion and re ferred many lithic grains, and lenses of conglom er ates, in ter ca lated them to dif fer ent deltaic and ma rine en vi ron ments. with grey, rose of brown mudstones, while the up per part is The Stebnyk For ma tion is known from ver te brate trace fos - dom i nated by rose and brown-rose mudstones, with in ter ca la - sils sum ma rized in Vialov (1966 and ref er ences therein) and tions of sand stone and fine con glo m er ate. Kulchytsky and Kulchytsky (1980). Hizhniakov (1954) rec og - The most de tailed lithological char ac ter is tics of the Stebnyk nized two ar tio dac tyl mam mal foot prints as cribed to the For ma tion were given by Gurzhyi (1969). Ac cord ing to this au - Ovinae and Susidae at Nadvirna. Vialov (1966) de ter mined thor, the Stebnyk For ma tion mudstones, mostly paral lel lam i - one of them as Pecoripeda (Ovipeda) djali Vialov. Vialov (1965) noticed foot prints and trackways of ar tio dac tyl mam - nated, con tain (mean) 15–20% CaCO3, and were de pos ited in a shal low la goon, with pe ri odic pre cip i ta tion of gyp sum and po - mals and foot prints of large birds in the lower part of the tas sium salt lenses at Kalush, Morschyn, Lanchyn and Utoropy. Stebnyk For ma tion in the Prut Val ley section, and in the under - Fine- and medium-grained sandstones contain up to 80–85% ly ing Dobrotiv For ma tion. Vialov (1965, 1966) also re ported of quartz, with mus co vite and cal cite, and rarely pyroclastic Skolithos, in ter preted as a shal low ma rine trace (Vialov, grains (Gurzhyi, 1969). More over, do lo mite, gyp sum (also in 1965). Among bird foot prints, Vialov (1960, 1966) de ter mined veins, see Zuber, 1882, 1888; Cizancourt, 1925), celestine, Avipeda phoenix Vialov, Avipeda sirin Vialov (both also in 478 Nestor Oszczypko, Alfred Uchman and Ihor Bubniak

Kulchytsky and Kulchytsky, 1980), and Avipeda filiportatis ski, 1927; Bujalski, 1938), Świderski (1925) noticed that the Vialov. Mam mal foot prints include Pecoripeda (Ovipeda) djali “salt clays” come out from un der “red shales and sand stones”. Vialov, Pecoripeda sp. 1 (Vialov, 1966), forms simi lar to Ac cord ing to Tołwiński (1950), some salt brine springs in the Bestiopeda sanguinolenia Vialov, Pecoripeda (Gazellipeda) area may also point to a shal low oc cur rence of salt clays of the gazella Vialov (Kulchytsky and Kulchytsky, 1980). The lat est Vorotyshcha For ma tion. Hnylko (2001, 2012, 2014; see also cited au thors de scribed also a frag ment of jaw of a mam mal Vashchenko and Hnylko, 2003) dis tin guished the Lanchyn belong ing to the Bovidae and de ter mined it as Hippidea parva Olistostrome sur rounded by the Stebnyk For ma tion. Ac cord ing Kulchytsky. Also a frag ment of jaw of Hypsodontus (Bovidae) to this au thor, the Mid dle Mio cene Lanchyn Olistostrome be - was found in the lower part of the Stebnyk For ma tion at longs to the Balych For ma tion, de vel oped at the front of the Yabloniv (Kulchitsky and Smirnov, 1996). Boryslav-Pokuttya Nappe. Ear lier, from the same lo cal ity (a The litho- and biostratigraphy of the Stebnyk For ma tion in sec tion close to the cable bridge at Dobrotiv), the salt-bear ing the Prut Val ley (Dobrotiv, Lanchyn) has been studied by Andre - depos its have been de scribed as the Vorotyshcha Olistostrome yeva-Grigorovich et al. (2008a, b, 2011), who rec ognized cal - in cluded in the up per part of the Stebnyk For ma tion (Andre - car e ous nannoplankton zone NN4 (Karpatian) in the Boryslav yeva-Grigorovich et al., 2008a). suc ces sion and NN4 (Karpatian) and NN5 (Early Badenian) zones in the Dobrotiv sec tion (Sambir suc ces sion), in the lower and up per parts of the for ma tion, respec tively (Fig. 2). These SECTIONS STUDIED au thors re ported in ter ca la tions of thick-bed ded sand stones (1.5–2.0 m) with large-scale trough cross-bed ding in the lower part of the Stebnyk For ma tion, which shows palaeotransport The stud ied sec tions A–C, E of the Stebnyk For ma tion are from the WNW (290–300°). Andreyeva-Grigorovich et al. lo cated in the Prut Val ley (Fig. 1D), be tween the vil lages of (2011), based on cal car eous nannoplankton and pelagic fora - Dobrotiv and Lanchyn, where al most con tin u ous ex po sures minifers, in tro duced a new Neo gene strati graphic scheme for are pres ent over a dis tance of sev eral kilo metres along the the Ukrai nian Carpathians and its foredeep. In this in ter pre ta - river banks (Fig. 3A). These expo sures dis play folded Mio- tion, the bound aries of al most all for ma tions were rec ognized cene de pos its of the Boryslav-Pokuttya and Sambir nappes as diachronous. This in ter pre ta tion was fol lowed by Kulyanda (see Oszczypko et al., 2012, 2014). However, the boundary and Hnylko (2012) who stud ied foraminifers from the Boryslav - be tween the Boryslav-Pokuttya and Sambir nappes is un clear, -Pokuttya and Sambir suc ces sions near Dobromyl, close to the because it is marked in side of the Stebnyk For ma tion in the Ukrai nian/Pol ish bound ary. In their opin ion, the youngest part of north ern limb of the Runhury Sloboda Anticline, ca. 1 km be - the Vorotyshcha For ma tion be longs to the Karpatian, while the low in flow of the Oslava River (Fig. 1C; see geo log i cal maps by bound aries be tween the Vorotyshcha and Stebnyk for ma tions Jankowski et al., 2007; Matskiv et al., 2009; Hnylko, 2012) are diachronous. with out any clear ev i dence. Ad di tion ally, the Stebnyk Forma - Tołwiński (1950) re ported salt diapirs cross ing the Stebnyk tion was stud ied in the Nadvirna area in the sec tion D For ma tion, ac com panied by salt brine springs, e.g. at Lanchyn. (Boryslav-Pokuttya Nappe; Fig. 3B). Ac cord ing to Hnylko Be tween Dobrotiv and Lanchyn (see also Zuber, 1888; Tołwiń - (2012, 2014), the Lanchyn Olistostrom e is lo cated be tween

Fig. 4. Geolog i cal cross-section 1–2 along the Prut River betw een Dobrotiv and Lanchyn, and geo log i cal cross-sec tion 3–4 through the Stebnyk For ma tion close to the ca ble bridge on the Prut River near Dobrotiv The Stebnyk Formation (Miocene) in the Boryslav-Pokuttya and Sambir nappes of the Ukrainian Carpathians 479

Fig. 5. Sed i men tary log of the lower part of the Stebnyk For ma tion along the Prut River (section A) and a de tailed sec tion of its up per part 480 Nestor Oszczypko, Alfred Uchman and Ihor Bubniak

Fig. 6. Sed i men tary logs of the Stebnyk For ma tion in sec tions B–E

VoF – Vorotyshcha For ma tion, SlCg – Sloboda Con glom er ate, DoF – Dobrotiv For ma tion; for other ex pla na tions see Fig ure 5 the Boryslav-Pokuttya and Sambir nappes. In the Prut River This syncline is clearly asymmet ri cal and sec ondarily folded val ley, the Stebnyk For ma tion fills the Dobrotiv Syncline, (Fig. 4). On the northern limb of the anticline, the Stebnyk For- which is about 3 km across, lo cated be tween the Runhur ma tion crops out in a ca. 900 m wide belt (sec tion A). Sed i - Sloboda Anticline of the Boryslav-Pokuttya Nappe to the south men tary logs of the sec tions are shown in Fig ures 5 and 6, and and the Lanchyn Anticline of the Sambir Nappe to the north. their facies fea tures in Fig ures 7–10. The Stebnyk Formation (Miocene) in the Boryslav-Pokuttya and Sambir nappes of the Ukrainian Carpathians 481

Fig. 7. Facies of the Stebnyk For ma tion A – amal gam ated thick sandstone beds (chan nel fa cies) in terca lated with pack ages of thin sand stone beds and mudstones (levee and cre vasse splay facies), sec tion A, the mea sure ment stick is 1 m long; B – a pack age of thin sand stone beds and in ter- ca lated mudstones (levee and cre vasse splay facies) be tween thick sand stone beds (chan nel fa cies), in verted po si tion, hummocky sur face of the bed in the middle (h), sec tion A; C – large-scale cross-bedding in a thick sand stone bed (chan nel fa - cies), in verted po si tion, sec tion D; D – par al lel-lam i nated thick sand stone bed, sec tion C; E – pinch ing out, thick, cross-bed ded sand stone above var ie gated mudstones and siltstones, sec tion E; F – thin-bed ded sand stones (levee and crevasse fa cies) in ter- ca lated with red, grey and dark grey mudstones, sec tion E

SECTION A bridge at Dobrotiv (N48°32’38.6’’; E24°43’51.6’’). In the lower part of this for ma tion (Fig. 4), at a dis tance of ~500 m, beds dip This sec tion be gins at the sed i men tary boundary betw een to NE un der an an gle of ~45°, while in the up per part, at a dis - the Dobrotiv and Stebnyk for ma tions (N48°32’26.4’’; E24°43’ tance of ~400 m, the beds are rotated to the sub-ver ti cal po si - 09.4’’) (Oszczypko et al., 2014: fig. 4) and ends on the southern tion and dip to the NW in an over turned po si tion. The hinge of a bound ary fault of the “Lanchyn Olistostrome” be neath the cable nar row syncline is lo cated close to the cable bridge at Dobrotiv 482 Nestor Oszczypko, Alfred Uchman and Ihor Bubniak

Fig. 8. Some facies features of the Stebnyk For ma tion A – cross-rip pled lam i nation in a sand stone bed, with mud intraclasts in the lower part, section E; B – amal gam ated, cross-bed - ded sand stone, in verted po si tion, sec tion A; C – cav erns af ter mudstone intraclasts in a thick sand stone beds, sec tion A; D – thin beds of sand stone and siltstone (levee and cre vasse splay facies) above dark grey mudstones (organic-rich delta plain fa cies), sec tion E; E – rip ple-marks on the sur face of a sand stone bed, sec tion E; F – red and greenish cal car eous mudstone and siltstones (delta plain fa cies), sec tion E

(Figs. 1D and 3). Sec tion A and other sec tions can be subdi - cross-lam i nated sand stone (palaeotransport from 270°), is vided into units char ac ter ized by the same lithological fea tures. com posed of thick pack ages (up to 25 m thick) of red and grey The sec tion (Fig. 5) begins with red-dom i nated and dark cal car e ous mudstones and shales in ter ca lated with five, grey mudstones, partly with shale part ings (Unit A, 40 m thick), 1.2–2.0 m thick sandstone beds, which dis play large-scale with a few inter ca la tions of me dium- to thick-bed ded, cross - cross- and par al lel-bed ding (palaeotransport from 270–310°). -lam i nated sand stone, lo cally con tain ing the trace fos sil Above, a ~90 m thick suc ces sion (Unit D) be gins with red and Skolithos isp. The in cli nation of the cross-laminae points to grey mudstones and shales fol lowed by a 3 m thick bed of me - palaeotransport from 260–270°. Higher up, ~180 m thick red dium-grained sand stone with par al lel and cross-bed ding. The and grey shales pre vail (Unit B), with rare in ter ca la tions of lat est Unit E (160 m thick) be gins with a 5 m thick bed of amal - thin-to me dium-bed ded sand stone. The next in ter val, 160 m gam ated sand stones, in ter ca lated with pack ages of thin sand - thick (Unit C), begin ning with a 1.5 m thick bed of par al lel and stone beds and mudstones (Fig. 7A, B). At the top of the sand - The Stebnyk Formation (Miocene) in the Boryslav-Pokuttya and Sambir nappes of the Ukrainian Carpathians 483

Fig. 9. Some sedi men tary , diagenetic and biogenic fea tures of the Stebnyk For ma tion A – spotty root structures (r) in red and greenish cal car eous mudstone and siltstones (delta plain fa cies), sec tion E; B – cal car e - ous con cre tions (c) in in ter ca la tions of cal car e ous mudstones, siltstones and thin-bedded sand stones, sec tion E; C – ferruginous rings around root struc tures in a muddy sandstone, sec tion C; D – casts of mudcracks and rain drop im prints, sec tion C; E – lower bedding sur face cov ered by flute casts crossed by mudcracks, sec tion D; F – parting sand stone sur face cross-cut by the trace fos sil Skolithos isp., sec tion C

stone, we found a level with muddy clasts and mam mal foot - SECTION B prints. This bed is fol lowed by a succes sion of red and grey mudstones and shales, with amal gam ated, cross-bed ded Sec tion B (Figs. 1D and 6) is lo cated be tween two re verse sand stones, in an in verted po si tion (Fig. 8B) and with cav i ties faults; the north ern bound ary fault of the “Lanchyn Olisto - af ter mudstone intraclasts in thick sand stone beds (Fig. 8C). strome” (N48°32’38.6’’; E24°43’51.6’’) and the other re verse The up per most part of the sec tion A, has been mea sured “bed fault (N48°32’54’’; E24°44’26.9’’; Fig. 1D) which sep arates the by bed” (located be tween N48°32’ 31.5’’; E24°43’40.5’’ and west-dip ping beds (in over turned po si tion) of the Stebnyk For- N48°32’33.6’’; E24°43’46.2’’) and is shown in Fig ure 5. The to - ma tion from the east-dip ping (nor mal po si tion) beds of this for - tal thick ness of the Stebnyk For ma tion sec tion A is ~640 m. ma tion in sec tion C (Fig. 4). Beds of the Stebnyk For ma tion in 484 Nestor Oszczypko, Alfred Uchman and Ihor Bubniak

Fig. 10. Some diagenetic and biogenic fea tures of the Stebnyk For ma tion A – pseudo morphs af ter ?gypsum crystals on a sand stone bed sur face, sec tion E; B – pseudo morphs af ter ?gypsum crystals (mainly upper left side) and microbially in duced struc tures (m) on a sand stone bed sur face, sec tion B; C – pseudo morphs af ter ?gypsum crystals on a sand stone bed sur face, sec tion B; D – a vein of honey-col oured gyp sum (g) in a sand stone and siltstone, section C sec tion B dip steeply (45–50°) to the west, in an over turned and rain prints (Fig. 9D) fol lowed by two thick-bedded posi tion. The to tal thick ness of the sec tion is up to 500 m. (~50 cm) sand stones. The to tal thick ness of the sec tion B at - The first 100 m thick por tion of the sec tion (lower Unit A; tains 500 m. Fig. 6), is dom i nated by red mudstones and shales with crys - tals of gypsum and salt on part ing sur faces (Fig. 10B, C). The mudstones are in ter ca lated with three me dium beds of SECTION C fine-grained sand stone at the base and one thick bed of muscovitic sand stone at the top of Unit A. This unit contains Sec tion C is fol lowed along the river for 1.2 km. It be gins also two dis turbed beds, up to 10 m thick, with blocks of sand- from the foot bridge across the Prut River at Lanchyn stone (Fig. 11C) and gypsum in fis sures. The next 40 m thick (N48°33’01.5’’; E24°45’15.5’’) and it con tin ues up to a re verse por tion (Unit B) is com posed of dark grey mudstones. The fault (N48°32’54’’; E24°44’26.9’’) sep arat ing sec tions C and B. mudstones are in ter ca lated with two beds (up to 0.5 thick The sec tion, 320 m thick, is built of gently folded beds of the each) of fine- to medium-grained sandstone. The upper 10 m Stebnyk For ma tion in a nor mal po si tion (Fig. 4). Ac cord ing to thick part of this por tion is com posed of lam i nated mudstone Oszczypko et al. (2014), this sec tion is lo cated in the south ern with in ter ca la tions of four, me dium-bed ded, par al lel-lam i nated limb of the Lanchyn Anticline, with a transi tion from the up per - and amal gam ated sand stone beds (Fig. 7D). This unit is fol - most part of the Vorotyshcha For ma tion through the Sloboda lowed by 85 m of red shales (Unit C) with two beds of amal - Con glom er ate and the Dobrotiv For ma tion, strongly re duced gam ated, fine-grained, thick-bedded sand stone, with fis sures in thick ness, fol lowed by the lower part of the Stebnyk (Fig. 6) filled with pink and honey-col oured gypsum (Fig. 10D). The of the Sambir Nappe. next por tion (Unit D) is 20 m thick and com posed of dark grey In this sec tion, the Stebnyk For ma tion is com posed of var ie - mud flow depos its with gypsum. The higher Unit E (120 m gated mudstones, red and dark grey, with a pre dom i nance of thick) is com posed of red mudstones with thin in ter ca la tions of red mudstones. The var ie gated mudstones are in ter ca lated fine-grained sand stone with dis persed salt and gypsum crys- with me dium-bed ded, cross-lam i nated sand stones (20–30 cm tals. The sec tion B is ter mi nated by ~ca.130 m thick suc ces - thick), which in di cate palaeotransport from the north-west. Spo - sion (Unit F) of red and dark grey mudstone with mudcracks rad i cally, in the up per and lower part of the sec tion, thick beds of The Stebnyk Formation (Miocene) in the Boryslav-Pokuttya and Sambir nappes of the Ukrainian Carpathians 485

fine-to me dium-grained, par al lel- to cross-bedded sand stone oc cur (Fig. 7D). The cross-bed ding in di cates palaeoflow from the north-west. Thin ner, muddy sand stone beds show mud - cracks and rain drop im prints and rarely ferruginous rings around root struc tures (Fig. 9C).

SECTION D

De pos its of sec tion D are vis i ble in a large ex po sure over a dis tance of ~1300 m in cliffs up to ~100 m high along the left bank of the Bystrytsia Nadvirnanska River at Nadvirna (Fig. 3B; from N48°39’10.7’’; E24°34’49.1’’ and N48°39’06.0’’; E24°34’ 21.5’’). Beds dip to the north are over turned (antiformal syn- cline, see Vialov, 1965). The ex po sure prob a bly rep re sents the mid dle part (rich in thick-bed ded sand stones) of the Stebnyk For ma tion of the Boryslav-Pokuttya Nappe. The mea sured part of the ex posure (ca. 64 m thick) is lo cated in its top o graph i cally lower part, which was stratigraphically measur able in the up per (younger) part of the suc ces sion (Fig. 3B). Af ter ro ta tion of the mea sured sec tion to the nor mal po si tion, the sec tion be gins with amal gam ated, very thick-bed ded (10.2 m) sand stone (N48°39’07.2’’; E24°34’29.2’’, 429 m a.s.l.), which is over lain by two sand stone beds (1.2 and 0.6 m thick), fol lowed by ~9 m thick pack age of red and grey mudstones and shales, with a 30 cm thick sand stone bed at the top (Fig. 6). The next in ter val, 10 m thick, is com posed of var ie gated mudstones with an in ter ca la tion of bright, 17 cm thick tuffite, which is cov ered by a 60 cm thick sand stone bed at the top. Stratigraphically above are var ie gated mudstones, 1.8 m thick, with a 60 cm thick, fine- to me dium-grained sandstone at the top, fol lowed by the next var ie gated mudstone pack age, 10.8 m thick, over lain by a 40 cm thick sand stone bed. Higher up, a 10 m thick por tion of the sec tion is com posed of red-brick and grey-greenish mudstones with in ter ca la tions of thin-bed ded sand stone (1–2 cm thick; Fig. 9E). Above, ~5 m of var ie gated mudstones with three tuffite lay - ers, respec tively 3.5 cm, 9 cm (both rose in col our), and 11 cm (grey-green ish) thick are pres ent (N48°39’06.9’’; E24°34’26.0’’). This tuffite-bear ing part is over lain by an amalgam ated sand - stone bed, which is ~5 m thick (N48°39’07.0’’; E24°34’34.0’’). The mea sured part of the sec tion is ter mi nated by a 40 cm thick, cross-bedded sand stone bed with a wavy top. An other 5 m thick sand stone bed oc curs in the north ern part of the ex posure (N48°39’08.5’’; E24°34’38.0’’).

SECTION E

Sec tion E is located in the south ern limb of the Runhury Sloboda Anticline (Boryslav-Pokuttya Nappe; Fig. 1D), along the Prut River, near Zariche (GPS co or di nates: from N48°32.074’’; E24°40.030’’ to N48°32.004’’; E24°39.256’’). This sec tion is rep re sen ta tive of the transi tion from the up per - most part of the Dobrotiv For ma tion to the Stebnyk For ma tion (Fig. 6; see also Oszczypko et al., 2014). Sec tion E be gins with a ~42 m thick unit of grey siltstones and mudstones with spo radic in ter ca la tions of thin bed ded sand stone (Figs. 6 and 8A). The top of this unit dis plays grey Fig. 11. Sedi men tary features of the diapir at Lanchyn siltstones with cal car e ous con cre tions and thin-bed ded sand - A – grey mudstones with lenses of gypsum, Vorotyshcha Forma tion; stones with mud cracks, rain drop im prints, root struc tures (Fig. B – de formed, partly imbricated frag ments of a thick sand stone bed, 9A) and con cre tions (Fig. 9B). The next in ter val, ~50 m thick, Stebnyk Forma tion, side of the struc ture; C – an iso lated block of is dom i nated by grey, dark grey and reddish mudstones with sand stone within de formed strata of the Stebnyk Forma tion very rare in ter ca la tions of thin-bed ded sand stone (Figs. 7E, F 486 Nestor Oszczypko, Alfred Uchman and Ihor Bubniak and 8D), some with rip ple marks (Fig. 8E). Above, grey, dark ous lo cally with transi tions to marls. Lo cally, small crys tals of grey and red mudstones, ~30 m thick, are exposed. The last gypsum or their pseudo morphs can be observed. This fa cies in ter val (~30 m thick) dis plays grey and red dish mudstones con tains in ter ca la tions of vari able sand stones or dark grey with thick-bed ded sand stones at the top, The Stebnyk Forma - mudstones, which are as cribed to other lithofacies. This fa cies tion is at least 170 m thick in sec tion E. cor re sponds to the Strutyn type distin guished by Cizancourt (1925). Dark grey mudstones (Figs. 7F and 8D). Dark grey cal- LITHOFACIES car eous mudstones are rare, though lo cally present as pack - ages up to a few metres thick sandwiched be tween the var ie - gated mud stones and siltstones. They are mostly massive and The Stebnyk For ma tion dis plays char ac ter is tic lithofacies, can be in ter ca lated with thin- to me dium-grained muddy sand- which are char ac ter ized by a certain set of sed i men tary fea - stones. tures (Figs. 5–10). They al low in ter pre ta tion of their re spec tive depositional palaeoenvironments. Thick-, medium- to thin-bedded sandstone s (Figs. 7A, DISCUSSION C–E and 8B). The sand stones are fine- to coarse-grained. Some beds are rich in muddy matrix. The thick beds can dis - play large-scale cross-bed ding or hor i zon tal lam i na tion. THE “LANCHYN OLISTOSTROME” – A DIAPIR FOLD Cross-lam i nated sets can be sep arated by amal gam ation sur - OR A TECTONIC WINDOW? faces. In thin ner beds, rip ple-lam i nation is com mon. Some beds are rich in mud intraclasts (Fig. 8C). This fa cies form Ac cord ing to Hnylko et al. (2012, 2014; see also Hnylko, pack ages, which start with the thick est sand stone bed. Above, 2001), the Stebnyk For ma tion of the Boryslav-Pokuttya Nappe thin ner sand stone beds in ter ca lated with mudstones and (Outer Carpathians) in the Prut River con tacts with the Lanchyn siltstones, usu ally rose in col our, are pres ent. The pack ages Olistostrome of the Sambir Nappe (Carpathian Foredeep). In are from 0.5 to 5 m thick. Many beds of all thick nesses change this in ter pre ta tion, the Lanchyn Olistostrome, up to 1 km thick, their thick ness and pinch out. The thin ner beds can dis play com posed of the Stebnyk For ma tion de pos its, is in cor po rated mudcracks. Sur faces of some beds dis play variable pseudo - into the Balych For ma tion (Badenian) of the Sambir Nappe. morphs af ter gypsum crystals (Fig. 10A–C). Many fis sures Based on our field ob ser va tions, a re-in ter pre ta tion of the cross ing sand stone beds and mudstones in all fa cies are filled “cha otic” de pos its as cribed to the “Lanchyn Olistostrome” be - with gypsum (Fig. 10D). tween Lanchyn and Dobrotiv is pro posed, as fol lows: Thin- and medium-be dded sandstone s (Figs. 7B, F and 1. The depos its re garded by Hnylko (2010, 2012, 2014) as 8A, D, F). The sand stones are fine- to me dium-grained, rip - the “Lanchyn Olistostrome” are lo cated in the Prut River, be - ple-lam i nated, rarely hor i zon tally or sub-hor i zon tally lam i - tween the stud ied sec tions A and B of the Stebnyk For ma tion nated, usually with sharp bases and gradational tops, centi - (Figs. 1D and 4). The south ern bound ary betw een the “cha otic metre- to decimetre-thick. Rarely, flute casts can be ob served depos its” and sec tion A is located along the left river bank, ca. at their base, showing uni di rec tional, erosional flow (Fig. 9E). 50 m be neath the Dobrotiv ca ble bridge, where sub-ver ti cal The sand stone beds are tab ular or pinch out on the scale of SW-dipping, strongly brecciated, dark grey salt clays (Fig. 11A) expo sures (up to a few, or a few tens of metres); some may with gypsum as well as blocks of “Sloboda-type” con glom er ate dis play hummocky tops (Fig. 7B). Some of the beds dis play and thick-bedded sand stones, as so ci ated with rose marly mud- mudcracks (Fig. 9D, E), raindrop im prints and im print casts stones of the Stebnyk For ma tion, are exposed (Fig. 11B, C). (Fig. 9D), mud intraclasts, rip ple-marks (Fig. 8E). Lo cally, root Such “cha otic” de pos its, 350–400 m thick, can be traced struc tures can be marked by ferruginized haloes (Fig. 9C). downriver for a dis tance of about 500 m. These de pos its also This fa cies cor re sponds to the Nadvirna type distin guished by con tact with the Stebnyk For ma tion of sec tion B along a reverse Cizancourt (1925). fault. The same de pos its were ob served on the right river bank, Var ie gated mudstones and siltstones (Figs. 8F and 9A, beneath the cable bridge (Fig. 4). In this case, the salt clay brec - B). Bed ded, rose, red dish, green ish or light grey varie gated cia of Vorotyshcha type, incor po rated into the folded de pos its of marly mudstones are the most eye-catch ing, dom i nant and the Stebnyk For ma tion, reached only 15 m in thick ness. basic li thol ogy, present through the whole sec tion of the 2. The salt clay breccia de scribed was consid ered pre vi - Stebnyk For ma tion. In ter ca la tions of siltstone show ing the ously as the Vorotyshcha Olistostrome (Andreyeva-Grigorovich same colours and other features are less com mon. Most of the et al., 2008a). The “Lanchyn Olistostrome” does not oc cur mudstone is rose, with grad ual tran si tion to other colours. Lo - within the Balych For ma tion, but is over lain by the Stebnyk For- cally, dif fuse en claves of some colours form spots against a ma tion. back ground of other colours. Some of these can be in ter - 3. It is dif fi cult to explain how the Lanchyn olistostrome has preted as root struc tures (Fig. 9A). At some ho ri zons cal car e - been devel oped in such rel atively shal low-water or even con ti - ous con cre tions are pres ent (Fig. 9B). The rose mudstones nental (al lu vial plain; see the next chap ter) de pos its of the can form about 10 m thick pack ages in ter ca lated with pack - Stebnyk For ma tion environment. ages a few metres thick of light grey or green ish mudstones 4. For a proper in ter pre ta tion of the cha otic de pos its of the (e.g., lower part of sec tion A). Centi metre- to decimetre-thick “Lanchyn Olistostrome” in the sec tion stud ied, the fol low ing bedding is lo cally easily visi ble, lo cally marked by subtle points may be con sid ered: changes of grain size. Pinch ing out of siltstone beds is lo cally a – the tri par tite di vi sion of the Vorotyshcha For ma tion pres ent. In some beds, hor i zon tal lam i na tion is eas ily vis i ble, in cludes the up per and lower salt clays, sep arated by but in oth ers the mudstones seem to mas sive. The lam i nation Sloboda-type con glom er ates (Vialov, 1965; Gurzhyi, is par al lel or subparallel, and lo cally can be disturbed plas tic - 1969; Andreyeva-Grigorovich et al., 1997). Such an as - ally or inter rupted by bioturbational struc tures. The con tent of so ci ation of salt clays and con glom er ates is nothing cal cium car bon ate fluc tu ates, some mudstones be ing cal car e - strange; The Stebnyk Formation (Miocene) in the Boryslav-Pokuttya and Sambir nappes of the Ukrainian Carpathians 487

b – in the study area, the dis tri bution of the Sloboda Con - Einsele, 2000). Kulchytsky and Kulchytsky (1980) who re ported glom er ate and the Dobrotiv For ma tion is discon tin u ous tetrapod foot prints at lev els lo cated 20–30 m, 100–150 m and (e.g., in the Lanchyn sec tion) and the salt clays with gyp- 280–340 m above the base of the for ma tion in the Deliatyn sum of the Vorotyshcha For ma tion can oc cur di rectly area, con cluded that the de po si tion of the Dobrotiv and Stebnyk un der the Stebnyk For ma tion; for ma tions took place in a change able shal low-water ba sin with c – in sev eral sec tions of the re gion stud ied, Tołwiński many shoals, bar ri ers and is lands, and that the ba sin was sur - (1950) de scribed ver ti cal, di rect, tec tonic con tacts of salt rounded by an allu vial plain with plants and ani mals typ i cal of a clays (Vorotyshcha For ma tion) with pink marls of the dry sa van nah. Khrushchov and Kompanets (1988) dis tin - Stebnyk For ma tion (e.g., in the Runhury Sloboda and guished four facies in the Stebnyk For ma tion: Jabloniv anticlines); Świderski (1925) con cluded that the – deltaic fa cies, which are mostly sandy; salt clays come out from under the Stebnyk For ma tion – near-shore fa cies – mostly mudstones and sand stones, (his red shales and sand stones); – shal low-ma rine fa cies – mostly mudstones and sand - d – the above-men tioned data clearly suggest that this stones; struc ture could be a salt-clay diapir fold, ac com pa nied – ma rine de pos its – mostly mudstones and sand stones by salt brine springs, among oth ers at Lanchyn and at with ero sive bases. nearby Vyżhny Maydan and Molodiatyn (Bujalski, 1938; Fol low ing their de scrip tions, the first facies was not found in Tołwiński, 1950). the sec tions stud ied. The in ter pre ta tions of fa cies 2–4 can not 5. Sum ma riz ing, we find that the “Lanchyn Olistostrome” be ac cepted. The authors cited found rain drop im prints and (Figs. 1D, 3 and 4) lo cated near the Dobrotiv ca ble bridge, may mudcracks in them, and their sed i men tary fea tures are dif fer ent be a diapir built of the Vorotyshcha For ma tion, which pierces from stan dard nearshore and shal low-ma rine fa cies (e.g., the Stebnyk For ma tion in the south ern limb of the Lanchyn Einsele, 2000). Anticline. Con sid er ations re gard ing the palaeoenvironment of the de - 6. The tec tonic or i gin of the “Lanchyn Olistostrome” is also pos its stud ied should in clude the con text of the whole Stebnyk sug gested by its con tacts with over turned de pos its of the For ma tion, which rep re sents a large depositional sys tem in a Stebnyk For ma tion in sec tions A and B. In our opin ion, this cer tain geotectonic set ting of the Carpathian Foredeep. In the “olistostrome” dis plays features of a “flower struc ture” kind com - Ukrai nian Carpathians, the for ma tion oc curs in a nar row belt. posed of tec toni cally deformed de pos its, but it does not dis play Gągała et al. (2012) es ti mated the width of the “Stebnyk Basin” any feature of a synsedimentary olistostrome. at about 70 km at the me rid ian of Przemyśl. Very likely, this 7. An other pos si ble expla nation is that this is a tec tonic win - width reached up to 100 km some tens of kilo metres to the east, dow of the salt de pos its of the Stebnyk For ma tion of the Sambir but it is unclear whether the Stebnyk For ma tion oc cu pied the Nappe, nev er the less of a diapir character. whole width of the basin rep re sented by the Boryslav-Pokuttya 8. We do not ques tion the pres ence of olistostrome de pos its and the Sambir nappes. The belt of the Stebnyk For ma tion out side of the study area. stretches along the Carpathian front from SE to at least the Ukrai nian-Ro ma nian bor der, for at least 300 km (Fig. 12). Ney (1968) and Ney et al. (1974) pos tu lated de po si tion of the DEPOSITIONAL SYSTEM AND ENVIRONMENT Stebnyk For ma tion in the gut ter-like ba sin de vel oped in front of the overthrusting Carpathian orogen. Ac cord ing to the lit er a ture The depositional en vi ron ment of the Stebnyk For ma tion re - (e.g., Vialov, 1965; Gurzhyi, 1969; Ney et al., 1974), the belt of mains poorly deter mined. Tołwiński (1950) re garded that the Stebnyk For ma tion is char ac ter ized by a distinct polar ity of fa - suc ces sion of the Dobrotiv and the Stebnyk for ma tions re flects cies, with a high con tri bu tion of conglom er ates and thick-bed - de po si tion in a deep en ing ba sin with in creas ing dis tance from ded sand stones, es pe cially in the lower part of the for ma tion, the shore. Vialov (1960) sug gested that the en vi ron ment of the dis ap pear ance of con glom er ates and fin ing of the suc ces sion Stebnyk For ma tion was char ac ter ized by wide beaches and fur ther to the SE, which is seen very well in the study area. A re - very shallow water, with frequent mi gra tions of the shore line, duc tion in gen eral thick ness of the for ma tion to the SE is also but Tkachenko (1961) pos tu lated a fully ma rine en vi ron ment re - pos si ble; it at tains 1200 m in SE Po land (Ney et al., 1974), and ferred to a trans gres sion, and par tial re stric tion of the basin dur - lo cally 2000 m in the west ern part of Ukraine (Gurzhyi, 1969), ing sed i men ta tion of the mid dle part of the for ma tion. Vialov and 600 m in sec tion A (this study). The for ma tion was de pos - (1965) noted that the pres ence of tetrapod foot prints, mud - ited over 1.2 m.y. (Andreyeva-Grigorovich et al., 2008a). This cracks and rain drop im prints dem on strates subaerial con di - gives a very high accu mu la tion rate of 50–167 cm/Ky. Most of tions at some ho ri zons. Głowacki et al. (1966) sug gested a la - the thicker sand stone beds in the study area show ero sive goonal en vi ron ment for the salt-bear ing for ma tions of the re - bases and in clude intraclasts and cross-bed ding. The sand was gion, and Gurzhyi (1969) pro posed the same envi ron ment for trans ported by water flow ing from the west and north-west as the Stebnyk For ma tion and stated that its clastic ma te rial de - shown by incli nation of cross-laminae in sev eral beds of the rived from flat and hilly shores. Vialov et al. (1981) re garded sec tions studied and by the orien ta tion of flute casts in some con glom er ates of the Stebnyk For ma tion as a mar ginal fa cies, beds. No ev i dence of wave ac tion or tides was ob served. The which tran sit to sand stone and mudstone fa cies to wards the in - con glom er ates of the for ma tion (west ern part) con tain ma te rial ner parts of the ba sin. The pres ence of ma rine foraminifers and from the fore land (mostly phyllites) and from the Carpathian cal car e ous nannoplankton, at least in the up per part of the for - flysch. Coarse-grained sand stones contains many lithic grains ma tion (see previ ous work) shows ma rine in flu ence, though the that in di cate short trans port (Gurzhyi, 1969). com mon oc cur rence of tetrapod foot prints, mudcracks and All these data sug gest that the depositional system (or a rain drop im prints, the ab sence of marine macro- and system tract) was trans ported mostly from the west and north - microfossils in most of the de pos its, and the over all “red beds” west, with clastic ma te rial de riv ing from the ris ing Carpathian char ac ter of the Stebnyk For ma tion chal lenges the sug ges tion orogenic belt and from the fore land forebulge, which con fined of a pre vail ing ma rine en vi ron ment, in clud ing a la goonal en vi - the depositional belt of the Stebnyk For ma tion from both sides. ron ment, for which con glom er ates are atyp i cal sed i ments (e.g., The con glom er ates might have been de pos ited as al lu vial fans 488 Nestor Oszczypko, Alfred Uchman and Ihor Bubniak

Fig. 12. Palaeogeographic scheme of the Karpatian–Early Badenian in the study re gion (based on Oszczypko and Oszczypko-Clowes, 2003; Oszczypko et al., 2006, 2012, sup ple mented)

and fan-del tas, as for the older Sloboda Con glom er ate in the they were not found in the sec tions stud ied. It is also pos si ble study area (see Oszczypko et al., 2012), or in braided rivers. that delta front depos its were not de vel oped, as in the under ly- Fur ther to the south-east, as in the study area, the system be - ing Dobrotiv For ma tion in ter preted as a mud-dom i nated came more dis tal with a transi tion to a delta plain, which was depositional system (see Oszczypko et al., 2014). This is a fea - cross-cut by river chan nels. In mi grat ing chan nels, the thicker ture of type C shallow -water del tas dom i nated by fluvial pro - sand stone beds were depos ited. The thin ner sand stone beds cesses, where the very shallow water in the water ba sin does can be re lated to channel lev ees and cre vasse splays. The ba - not al low devel op ment of typi cal mouth bars; in stead, gently in- sic facies, i.e. the red mudstones, were de pos ited on the delta clined (a few degrees) beds are de pos ited (Postma, 1990). plain. Ma rine in gres sions to the delta plain took place as the up - Such beds are dif fi cult to rec ognize even if they are traced for per part of the for ma tion was de pos ited (as indi cated by Mio - sev eral tens of metres, as in the scale of most ex po sures in the cene ma rine microfossils), which is over lain and partly lat er ally study area. Also deltaic sed i ments that ac cu mu lated in shal low re placed by the ma rine Balych For ma tion, but no clear sed i - lakes, with very limited ac com mo da tion space, do not form typi - men tary fea tures of ma rine sed i men ta tion have been en coun - cal thick ening-up pack ages of beds (Tye and Coleman, 1989). tered in the Stebnyk For ma tion. Vialov (1966) con sid ered that Gen eral fin ing of the suc ces sion up the Stebnyk For ma tion, the pres ence of Skolithos is some ex po sures of the Stebnyk which is very clear in SE Po land (Ney et al., 1974) and the tran - For ma tion is ev i dence of a ma rine en vi ron ment, but this trace si tion to the ma rine Balych For ma tion show an over all retrogra - fos sil is known also from flu vial set tings (e.g., Buatois and dation of the depositional system. Mángano, 2007). That a high rate of ac cu mu la tion was com pensated by The weak part of this in ter pre ta tion is the ab sence of delta sub si dence had al ready been noticed by Tołwiński (1950). front de pos its, with typ i cal thick en ing-up pack ages and large - Flex ural mod el ling of the Pol ish and Ukrai nian Carpathian -scale cross-bedding with foreset units. These may be far ther to orogen (Royden and Burchfiel, 1989; Krzywiec and Jochym, the south-east or in the over lying Balych For ma tion, but no in - 1997) sug gests that deeper crustal pro cesses and as so ci ated ves ti gations have been made that could prove or dis prove this subsurface loads are respon si ble for the pres ent-day flexural hy poth e sis. Maybe the sand stone-dom i nated deltaic fa cies in bending of the fore land lithospheric plate (see also Kováč et 0.5–16 m thick pack ages dis tin guished by Khrushchov and al., 1998; Oszczypko et al., 2006 and ref er ences therein). Dur - Kompanets (1988) in deed rep re sent a delta front fa cies, but ing the Ottnangian–Karpatian, the rate of subsi dence at the The Stebnyk Formation (Miocene) in the Boryslav-Pokuttya and Sambir nappes of the Ukrainian Carpathians 489 front of the Ukrai nian Outer Carpathians may have reached at vel opment of such fauna due to con ti nental or hypersaline least 2000 m/m.y. (Oszczypko, 1998) and it was com pensated con di tions, the in crease in the tem per a ture noted prob a bly by sedi ment in put, in clud ing of those belong ing to the Stebnyk touched also the east ern part of the Carpathian Foredeep and For ma tion. in flu enced sed i men ta tion of the Stebnyk For ma tion. Lower On set of coarser sed i men ta tion of the lower part of the tem per a tures ob tained on the ba sis of ox y gen iso topes from Stebnyk For ma tion, es pecially in the north-west of its bryozoan skel etons, mainly for the Vi enna Ba sin and the west - depositional area, may have been caused by a low er ing of the ern part of the Carpathian Foredeep, and re lated to upwelling base level. An about 30 m drop in sea level around the (Key et al., 2013) may rather re flect lo cal con di tions. Con tin u - Burdigalian-Langhian bound ary, before the Mid dle Mio cene Cli - ous Late Paleogene–Neo gene aridification of the cli mate, ma tic Op ti mum, has been pos tu lated (Hilgen et al., 2012). How - known from the Eur asian in te rior and from the North ern Hemi - ever, some geotectonic pro cesses in the foredeep de vel op - sphere in gen eral, was related to global cool ing and its conse - ment may have been the dom i nant fac tor, such as the intra - quences (Tang and Ding, 2013). However, this trend var ied lo - -Burdigalian fold ing and up lift of the Outer Carpathians re lated cally in space and time (Eronen et al., 2012). For in stance, co - to the north-eastwards trans la tion of the Alcapa and Tisza - eval sec tions from Bul garia, lo cated roughly 500 km to -Dacia microplates, in re sponse to the roll-back of the south-east from the study area, do not show any palaeo- Carpathian subduction slab (Zoetemeijer et al., 1999; Ziegler et botanical ev i dence of arid cli mate (Ivanov et al., 2012). How - al., 2002; Rasser et al., 2008). ever, it can not be ex cluded that the cli mate of the east ern part of the Carpathian Foredeep, by its lo ca tion, was more influ - enced by this aridification than in the other parts of the PALAEOCLIMATIC ASPECTS Paratethys.

The red bed char ac ter of the de pos its of the Stebnyk For- ma tion, the pres ence of evaporitic min er als and the com mon CONCLUSIONS mudcracks sug gest fre quent drying of the sedi ment sur face and gen er ally a hot cli mate fa vour ing evap o ra tion. The de pos - its of zones NN4–NN5 (sedi men ta tion of the Stebnyk Forma - The Mio cene Stebnyk For ma tion (Karpatian–Mid dle Bade - tion cor re sponds to the upper part of the NN4 – lower part of nian) is a ~600–2000 m thick unit of the Boryslav -Pokuttya and the NN5 zones; Fig. 2) show evaporitic fa cies only in the east - Sambir nappes. It con tains con glom er ates and thick -bed ded ern part of the Carpathian Foredeep, not in its west ern part or sand stones in the lower part in the north-w est. In the up per in the Cen tral Paratethys (see Kováč et al., 2003). Such con di - part and in the entire sec tion fur ther to the south-east, it is tions show a clima tic change with respect to the un der lying dom i nated by var ie gated cal car e ous mud stones and Dobrotiv For ma tion, the depos its of which are gen er ally grey, siltstones in ter ca lated with sand stones as in the study area in with no mudcracks even in ho ri zons with tetrapod foot prints the val ley of the Prut River, betw een Deliatyn and Lanchyn. (Oszczypko et al., 2014), ex cept for the up per most part of the These de pos its rep re sent mostly a delta plain fa cies, where for ma tion, where Vialov (1965) noted some mudcracks. This mudstones were de pos ited in the interchannel ar eas, thick change cor re sponds well to the global trend, but with some re - sand stone beds in the distributary chan nels and thin ner sand - gional dif fer ences. Gen er ally, the in ter val be tween 17 and stone beds in channel lev ees and cre vasse splays. In the up - 15 Ma (16.5–14 Ma – upper most Karpatian–Early Badenian – per part of the for ma tion, marine in gres sions are marked by an sed i men ta tion of the Stebnyk and the Balych for ma tions; see oc cur rence of marine microfossils (NN4 and lo cally NN5 Andreyeva-Grigorovich et al., 2008a; Fig. 2) is re ferred to the zones). Sed i ments of the Stebnyk For ma tion ac cu mu lated at Mid dle Mio cene Cli ma tic Op ti mum char ac ter ized by global rates of 50–167 cm/kyr in a nar row and long (at least 300 km) warmth, a high con tent of CO2 in the at mo sphere, and a sig nif - de pres sion be tween the ris ing Carpathian orogen and the i cant de crease in the size of the Ant arc tic icecap (Fos ter et al., forebulge el e va tion of the Eu ro pean Plat form fore land, in 2012). Kroh (2007) stud ied Mio cene echinoids and as so ci ated warm and semi-dry cli ma tic con di tions (~Mid dle Mio cene Cli - echinoderm faunas from the Paratethys in the con text of the ma tic Op ti mum). The ac cu mu la tion was com pen sated by sub - cli mate. He con cluded that the tem per ature rose from the si dence in the de vel op ing Carpathian Foredeep. The so-called Karpatian to the Early Badenian opti mum up to trop i cal lev els “Lanchyn olistostrome” is rather a diapir that as cended from (sea sur face tem per atures 16–17°C dur ing win ter and up un der the Stebnyk For ma tion. 28°C dur ing sum mer) for the Cen tral Paratethys; how ever, he sug gested that the Carpathian Foredeep part still re mained in Ac knowl edge ments. Field re searches have been sup - the tem per ate cli mate zone, with the res er va tion that the fau - ported by the Jagiellonian Uni ver sity (DS funds). A. Wysocka nal dif fer ences be tween these re gions may have been influ - (War saw, Po land) and O. Hnylko (Lviv, Ukraine) pro vided crit i - enced by isola tion. Tak ing in ac count that the de pos its of the cal re viewer com ments, which are partly used in the im proved Stebnyk For ma tion and co eval strata are not suit able for de - ver sion of the text. 490 Nestor Oszczypko, Alfred Uchman and Ihor Bubniak

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