The Tylawa Limestones – a regional marker horizon in the Lower Oligocene of the Paratethys: diagnostic characteristics from the type area

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Geo log i cal Quar terly, 2012, 56 (4): 833–844 DOI: http://dx.doi.org/10.7306/gq.1058

The Tylawa Lime stones – a re gional marker ho ri zon in the Lower Oligocene of the Paratethys: di ag nos tic char ac ter is tics from the type area

Agnieszka CIUREJ and Grzegorz HACZEWSKI

Ciurej A. and Haczewski G. (2012) – The Tylawa Lime stones – a re gional marker ho ri zon in the Lower Oligocene of the Paratethys: di - ag nos tic char ac ter is tics from the type area. Geol. Quart., 56 (4): 833–844, doi: 10.7306/gq.1058

Three units of lam i nated coccolith lime stone are used as re gional chronohorizons in the Oligocene of the Outer Carpathians. Two of them – the Tylawa Lime stones and the Jasło Lime stone – dis play a sim i lar type of lam i na tion and their dis crim i na tion is in some cases prob - lem atic. We pro vide a de tailed mesoscopic and mi cro scopic lithological de scrip tion of the Tylawa Lime stones from the type lo cal ity at Tylawa and from Rudawka Rymanowska – the best ex po sure in the Pol ish Carpathians. The finely lam i nated lime stone lay ers are up to 5.5 cm thick and are dis persed through a sec tion more than 100 m thick. They are grouped in clus ters. They dif fer from the youn ger Jasło Lime stone in: (1) an ab sence of foraminifers, (2) a mass oc cur rence of Reticulofenestra ornata Müller, (3) the pres ence of voids af ter pennate di a toms, (4) dark laminae which are more pro nounced than in the Jasło Lime stone.

Agnieszka Ciurej, In sti tute of Geo log i cal Sci ences, Pol ish Acad emy of Sci ences, Senacka 1, 31-002 Kraków, Po land, e-mail:

ndciurej@cyf-kr.edu.pl; Grzegorz Haczewski, Ped a gog i cal Uni ver sity of Kraków, Podchorążych 2, 30-084, Kraków, Po land, e-mail:

grzehacz@up.krakow.pl (re ceived: April 26, 2012; ac cepted: May 20, 2012; first pub lished on line: No vem ber 15, 2012).

Key words: Tylawa Lime stones, Outer Carpathians, coccolith lime stone, chronohorizons, Oligocene.

INTRODUCTION

The Oligocene–Lower Mio cene de pos its of the Outer Carpathians are up to ca. 2 km thick and make up as much as a half of the en tire Up per Ju ras sic through Lower Mio cene suc - ces sion of the Outer Carpathian fold-and-thrust belt. These synorogenic de pos its were laid down in a ba sin whose com mu - ni ca tion with the open ocean be came re stricted in the Early Oligocene (Oszczypko, 2004). The Oligocene se quence con - sists of a va ri ety of diachronous and lat er ally vari able fa cies, from or ganic-rich black shales to coarse-grained grav ity-driven mass-flow de pos its. The se quence is poor in stratigraphically use ful fos sils and the pres ence of many en demic forms pre - cludes pre cise biostratigraphic cor re la tion with the co eval strata of the open ocean. This is why thin in ter ca la tions of pe - lagic coccolith lime stone, con cen trated in dis tinct isochronous ho ri zons, have been ex ten sively used as re gional strati graphic mark ers be tween var i ous tec tonic units and fa cies since the mid dle of the 20th cen tury (see Jucha, 1957; Jucha and Kotlarczyk, 1958; Ślączka, 1959a, b; Koszarski and Żytko, 1961; Jucha, 1969; Haczewski, 1984, 1989; Melinte, 2005;

Kotlarczyk et al., 2006). Three of these ho ri zons (Tylawa, Jasło

and Zagórz ho ri zons) have been rec og nized and mapped along nearly the whole length of the Carpathians, while a few oth ers have been dis tin guished and named lo cally.

The lime stones oc cur as millimetric to decimetric lay ers of coccolith lime stone. In most sec tions they are split by clastic de pos its that are usu ally much thicker than the lime stone them selves. Cor re la tion of laminae in the Jasło Lime stone has shown that the clastic rocks rep re sent event de pos its, and the lam i nated lime stone rep re sents the bulk of the geo log i cal time dur ing which the lime stone unit was laid down (Haczewski, 1989). The laminae in the Jasło Lime stone and Zagórz Lime - stone have been cor re lated across the ma jor tec tonic units and fa cies zones of the Outer Carpathians over dis tances up to 550 km. Be cause of this the lime stone ho ri zons have been ac - cepted as chronohorizons (sensu Racki and Narkiewicz, 2006). Some gen eral mesoscopic char ac ter is tics help dis tin - guish the lime stones from the three ma jor ho ri zons. These char ac ter is tics in clude: type of lam i na tion, abun dance of fish re mains, and pres ence of plank tonic foraminifers. There are, how ever, many lo cal i ties where iden ti fi ca tion of “Jasło-like”

lime stones is un cer tain (e.g., Koráb and Kotlarczyk, 1977).

This is be cause of: (1) heavy al ter ation of lime stone by sili ci - fi ca tion, dolomitization, weath er ing, or tec tonic frac tur ing,

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(2) sub stan tial clastic ad mix ture in the lime stone that ob scures the iden tity of laminae, (3) the lime stone lay ers be ing too thin to study their lam i na tion or fau nal con tent, and (4) the pres - ence of lime stone lay ers not be long ing to the pre vi ously de - fined ho ri zons. The cor re la tion of laminae in the Jasło and Zagórz lime stones helps to over come dif fi culty (1) in many cases, even when lime stone frag ments are found loose (Haczewski, 1984, 1989). Clastic ad mix ture may re sult in un - even thick en ing and loss of def i ni tion of in di vid ual laminae, mak ing them use less for cor re la tion.

The Tylawa Lime stones seem to be in volved in most of the doubt ful cases. Even if fine, reg u lar lam i na tion, abun dance of fish and the lack of plank tonic foraminifers are valid dis tinc tive char ac ter is tics in clas si cal good ex po sures of typ i cal Tylawa Lime stones, the lack of fish re mains or foraminifers may re flect a for tu itously bar ren frag ment of else where fossiliferous rock at lo cal i ties where only thin lime stone lay ers, or small loose frag ments of weath ered lime stone are pres ent.

We pro vide here a de tailed de scrip tion of the struc ture of the Tylawa Lime stones as seen mesoscopically as well as in op ti cal and elec tron mi cro scope images, with the aim of pro - vid ing better cri te ria for their iden ti fi ca tion. We use ma te rial from the orig i nal lo cal ity at Tylawa and from the best ex po sure at Rudawka Rymanowska.

CONCEPT OF THE TYLAWA LIMESTONES Thin lay ers of coccolith lime stone in the Carpathian Flysch have been first no ticed and re ported by Uhlig (1882) near Jasło in a sand stone-and-shale turbidite se quence of the Krosno Beds. He soon found sim i lar lime stones around Bochnia within dark bi tu mi nous shales of Menilite type (Uhlig, 1884). He re - ferred to them as “...those char ac ter is tic, fish-bear ing cal car e - ous shales from Jasło”. This is the first use of the coccolith lime stones in the Carpathian Oligocene as a re gional marker be tween var i ous fa cies.

The Uhlig’s term “Kalkschiefer von Jasło”, af ter trans la tion to Pol ish and leav ing out the “Kalk” part, has turned into “łupki jasielskie” (Jasło Shales) and was used for whit ish-weath er ing platy lime stones found at var i ous lo cal i ties. The find ing that the lime stones are ex ten sive re gional chronohorizons, among the fa cies units ear lier con sid ered as time-units, be came a ma jor break-through in the stra tig ra phy of the Outer Carpathians (Shakyn, 1958; Jucha and Kotlarczyk, 1958; Koszarski and Żytko, 1959). Three sep a rate ho ri zons of “Jasło Shales” were traced over large ar eas. Jucha (1957) com piled in for ma tion on the spa tial and strati graphic dis tri bu tion of the lime stones and no ticed that strata re sem bling the “Jasło shales” oc cur also in the lower part of the Oligocene se quence in the in ner part of the Silesian Unit (at Rudawka Rymanowska). Ślączka (1959a, b) found these lime stones in the outer part of the Dukla Unit and de scribed them as finely lam i nated lime stones sim i lar to the Jasło Shales. He also no ticed that the Jasło Shales proper, sit u - ated higher in the strati graphic se quence, are rich in globigerinids. In his mono graph on the Dukla Unit, Ślączka (1971) con firmed the per sis tent strati graphic po si tion of the

“Tylawa Shales” in the fron tal part of the Dukla Nappe.

Stud ies on the abun dant fish fauna in the Tylawa Lime - stones re vealed that this, in the nar row strati graphic in ter val en com pass ing the Tylawa Lime stones, is clearly dis tinct from fish as sem blages be low and above (Jerzmańska and Kotlarczyk, 1968, 1981; Kotlarczyk et al., 2006).

Jucha (1969) in tro duced the name “łupki tylawskie”

(Tylawa Shales) for the old est ho ri zon, af ter the clas si cal lo cal - ity in the Dukla Unit. Many map ping ge ol o gists (in clud ing A.

Ślączka, pers. comm. to GH, 1998) sug gested that the Tylawa Shales oc cur as sev eral sep a rate lime stone ho ri zons, stratigraphically close to one an other. The fine, dis tinct lam i na - tion in the Tylawa Lime stones has not been con vinc ingly cor re - lated over dis tances greater than ca. 20 km and the Tylawa Lime stones seem to rep re sent re cur rent ep i sodes of coccolith lime stone de po si tion. That is why Haczewski (1989, pp.

442–443), pre sent ing a typology and no men cla tur al scheme for the three ma jor chronohorizons of coccolith lime stone, named the Tylawa Lime stones in plu ral, in con trast with sin gu lar names for the Jasło Lime stone and Zagórz Lime stone. The Tylawa Lime stones in their type area oc cur as millimetric to centimetric lay ers of coccolith lime stone with a to tal thick ness up to ca. 50 cm and are of ten grouped in clus ters of closely spaced lay ers, all en closed in a se quence of host sed i ments up to ca. 100 m thick.

Sim i lar lam i nated lime stones have been found at a sim i lar strati graphic po si tion in other ar eas of the Silesian Unit, in the Subsilesian and Skole units, and re ferred to the Tylawa Lime - stones ho ri zon (Koszarski and Żytko, 1959; Jucha, 1969;

Kotlarczyk, 1977, 1988; Kotlarczyk et al., 2006). The Tylawa Lime stones oc cur in the lower part of the Menilite Beds in nannoplankton zone NP 23 of Mar tini (1971) (see Krhovský, 1981). The dis tinc tive fish as sem blage was used to de fine biozone IPM2 in the ichthyofaunal suc ces sion (Jerzmańska and Kotlarczyk, 1968, 1981; Kotlarczyk et al., 2006). Equiv a lents of the Tylawa Lime stones have been rec og nized in the Al pine fore land ba sin in Aus tria (Müller and Blaschke, 1971; Schulz et al., 2005), in the Outer Carpathians from the Czech Re pub lic, through Po land, Slovakia and Ukraine to Ro ma nia (Kotlarczyk, 1961; Koráb and Kotlarczyk, 1977; Haczewski, 1989; Krhovský et al., 1992; Melinte, 2005; Melinte- Dobrinescu and Brustur, 2008). Their rec og ni tion was based on the pres ence of lam i nated lime stones in the lower part of the Oligocene suc ces sion, and was sup ported by data from fish, nannoplankton or both (see ref er ences above). Nannoplankton is usu ally pre ferred to fish as a means of rapid biostratigra - phical di ag no sis, but dis in te gra tion of the Tylawa Lime stones for nannoplankton anal y sis usu ally re sults in sam ples de scribed as bar ren of coccolithophores (see Ciurej, 2009).

Pos si ble an a logues of the Tylawa Lime stones have been de scribed from the suc ces sions in other parts of Paratethys Ba sin, east of the Carpathian area, mainly in the Cau ca sian re - gion (Nagymarosy and Voronina, 1992; Muzylev et al., 1992). Pub lished de scrip tions seem to sug gest that the num - ber and thick ness of the lam i nated lime stone lay ers in crease to the south and south-east. The lithological de scrip tions pro - vided in this pa per may be used to eval u ate the sim i lar ity of these de pos its to the Tylawa Lime stones. Be sides the lithological sim i lar i ties, the na ture of the fish as sem blage typ i - cal of the IPM2 zone of Kotlarczyk et al. (2006) should be

834 Agnieszka Ciurej and Grzegorz Haczewski

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con sid ered a re quired di ag nos tic fea ture of any pos si ble equiv a lents of the Tylawa Lime stones.

METHODS

Sec tions with the Tylawa Lime stones have been logged in the field at a scale of 1:10. Ori ented (top-and-bot tom) sam ples were taken from the com plete thick ness of the Tylawa Lime - stones and from the di rectly ad ja cent host strata of each lime - stone layer. The lime stone sam ples were cut per pen dic u lar to strat i fi ca tion and pho to graphed in uni form light ing con di tions.

The pho to graphs were dig i tally as sem bled into a con tin u ous se quence of the lam i nated lime stones from each lo cal ity, re pro - duced at the same scale.

Mesoscopic lithological de scrip tion of the lime stones was made milli metre by milli metre from the bot tom to the top of each sec tion on the cut and pol ished sur faces of the lime stone lay ers. Mi cro scopic ex am i na tion was made on stan dard un cov - ered petrographic thin sec tions cut per pen dic u lar to lam i na tion and di ag o nally, at an an gle of 50° to lam i na tion in or der to better sep a rate var i ous lev els within the laminae. The thin sec - tions were stud ied with an Olym pus SZX9 (trans mit ted light) po lar iz ing mi cro scope with a dig i tal cam era (Olym pus U-TVO.5XC-2) steered by a com puter us ing Anal y sis soft ware and us ing a scan ning elec tron mi cro scope (SEM), us ing var i - ous modes of ob ser va tion: charge con trast im ag ing (CCI) and back-scat tered elec trons (BSE). More tech ni cal de tails are given in Ciurej (2010). The SEM–CCI method al lows study of an a tom i cal de tails of cal car e ous nannofossils in strongly ce - mented sam ples that were re garded as bar ren of nannoplankton af ter stan dard sep a ra tion treat ment for cal car e ous nannofossils (Ciurej, 2009).

DETAILS OF THE TYLAWA SECTION

The Tylawa lo cal ity is gen er ally ac cepted (Jucha, 1969;

Ślączka, 1973a, 1977) as the type lo cal ity of the Tylawa Lime - stones. The ex po sure lies in the east ern part of the Pol ish Carpathians, on the right bank of the Jasiołka River, ca. 1 km east of the in ter na tional road E371 be tween Svidnik (Slovakia) and Dukla (Fig. 1). The lower part of the Menilite Beds of the Dukla Unit, ex posed there, in cludes, from bot tom to top: the Mszanka Sand stones, the Sub-Cergowa Marls (equiv a lent to the Dynów Marls) and the Cergowa Beds. The Cergowa Beds are bi par tite in this sec tion, with the lower di vi sion of the thick- and thin-bed ded Cergowa Sand stones over lain by the Cergowa Shales – marly, grey to brown ish shales rhyth mi cally al ter nat -

The Tylawa Limestones – a regional marker horizon in the Lower Oligocene of the Paratethys: diagnostic characteristics from the type area 835

Fig. 1. Lo ca tion of study area

A – sim pli fied geo log i cal map of the Outer Carpathians with the lo ca tion of the study area: C. F. – Carpathian Foredeep, I. C. – In ner Carpathians, P. B. – Pan nonian Ba sin, PKB – Pieniny Klippen Belt, T. B. – Transylvanian Ba sin, V. B. – Vi enna Ba sin; B – sim pli fied geo log i cal map of the Pol ish part of the Outer Carpathians (af ter Książkiewicz, 1972) with lo ca tion of the sec tions stud ied; C – de tailed lo ca tion of Tylawa sec tion; D – de tailed lo ca tion of the Rudawka Rymanowska sec tion

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ing with thin- and me dium-bed ded grey micaceous cal car e ous sand stones. The fa cies of the Cergowa Shales lat er ally re places the Menilite-type dark, or ganic-rich si li ceous shales. The Tylawa Lime stones are interlayered within the Cergowa Shales (Jucha, 1969; Ślączka, 1973a).

De tailed ex am i na tion of the 115.3 m thick sec tion has re - vealed a to tal of 18 cm of the Tylawa Lime stones in 12 lay ers.

The thin lime stone lay ers are grouped in three clus ters (Figs. 2 and 3). The two higher clus ters, sep a rated from one an other by ca. 40 m, are most likely those de scribed by Jucha (1969) and Ślączka (1973a). Geo graph ical co or di nates (in WGS 84) of the ex po sure of the high est clus ter were de ter mined us ing a hand-held GPS re ceiver as: N49°28’18.3” and E21°43’21.3”.

The third clus ter of lime stone lay ers, not de scribed ear lier, is ex posed 65 m be low the mid dle clus ter at: N49°28’17.1” and E21°43’28.62”. All lime stone lay ers dis play char ac ter is tic submillimetric to millimetric lam i na tion con sist ing of al ter na - tions of light and dark laminae, though at some lev els the mesoscopic vis i bil ity of laminae is ob scured on weath ered sur - faces. The se quences of laminae dif fer slightly be tween and within the clus ters in the thick nesses and pro por tions of the light and dark com po nents.

The low est clus ter con sists of two lay ers of lam i nated lime - stone (Figs. 2 and 3). The lower layer (6 mm thick) is poorly dis cern ible against the en com pass ing black mudstone (TYL 2/07; Fig. 3). It con sists of a bun dle of thin laminae with a pre dom i nant dark com po nent. The other layer lies 10 cm higher and dis plays dis tinct lam i na tion (TYL 3/07; Fig. 3).

Laminae of marly claystone are pres ent among the bun dles of lime stone lamina cou plets. This layer is un der lain, with a sharp bound ary, by non-lam i nated lime stone and passes grad u ally up wards into pelletal marly claystone.

The mid dle clus ter con sists of two lay ers of lam i nated lime stone within a suc ces sion dom i nated by shales and mudstones (Figs. 2 and 3). The lower layer con sists of three bun dles of lime stone lamina cou plets sep a rated by grey marly mudstone. Lam i na tion in the lime stones within this layer is poorly vis i ble (TYL 5A/07; Fig. 3). The higher layer also com - prises three bun dles of eas ily dis cern ible lime stone lamina cou - plets sep a rated by grey marly mudstone (TYL 5/07; Fig. 3).

This layer is un der lain by grey claystone and over lain by dark-grey mudstone.

The high est clus ter con sists of eight thin lay ers of lam i - nated lime stone al ter nat ing with non-lam i nated lime stones, mudstones, shales and sand stone (Figs. 2 and 3). Lam i na tion in the two low est lime stone lay ers of this clus ter (TYL 7/07 and TYL 8/07; Fig. 3) is poorly dis cern ible mesoscopically and has a darker hue than the higher lay ers.

DETAILS OF THE RUDAWKA RYMANOWSKA SECTION

The sec tion with the Tylawa Lime stones at Rudawka Rymanowska is sit u ated in the Iwonicz Zdrój anticline in the south ern (in ner) zone of the Silesian Unit in the east ern part of the Pol ish Outer Carpathians, ca. 25 km SE from Krosno, in the

Fig. 2. Lithological col umn of the Tylawa Lime stones at Tylawa as logged in 2007 with po si tion of sam ples re ferred to in this pa per

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The Tylawa Limestones – a regional marker horizon in the Lower Oligocene of the Paratethys: diagnostic characteristics from the type area837

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Wisłok River bed (Fig. 1). The Tylawa Lime stones are ex posed there twice, dis placed by a lon gi tu di nal fault, in ex po sures sep - a rated by ca. 750 m, in a gently dip ping se quence of the Menilite Beds. The num ber and qual ity of the ex po sures at Rudawka Rymanowska vary through time as a re sult of floods and hu man in ter ven tion (see Ślączka, 1973b; Haczewski, 1989; Ślączka and Kaminski, 1998; Bieńkowska, 2004; Ciurej, 2009). The lime stones in both groups of ex po sures oc cur ca. 20 m above the top of the Cergowa Sand stones, in a suc ces - sion of dark, non-cal car e ous or ganic-rich shale with cherts and lime stones of Dynów Marl-type. Haczewski (1989) cor re lated laminae in the Tylawa Lime stones on both sides of the fault and dem on strated that at least some lay ers of the dark shale are dis - con tin u ous lat er ally and that centimetric se quences of lam i - nated lime stones dis ap pear over a dis tance of only 750 m.

Bieńkowska (2004) stud ied the fish fauna from three lo ca tions at Rudawka Rymanowska, on both sides of the fault.

The de scrip tion be low is based on the ex po sure on the north ern side of the fault (ar row in Fig. 1D: N49°31’11.4”, E21°55’50.9”). A nearly com plete sec tion was sur veyed, 18.6 m long (Fig. 4). The sec tion in cludes 18 lay ers of the Tylawa Lime stones with a to tal thick ness of 38.7 cm. Seven of these are thin ner than 1 cm and the thick est is 5.5 cm thick.

Most lay ers are clearly dis tin guish able mesoscopically among the host de pos its; only the thin nest lay ers, con sist ing of few lamina cou plets, are less dis tinct (Fig. 5). The char ac ter is tics of lam i na tion are sim i lar to those at Tylawa.

Thin in ter ca la tions within the lam i nated lime stone lay ers are sim i lar to those at Tylawa but more nu mer ous. They in - clude laminae of mudstone, claystone and micritic lime stone.

Some lam i nated lime stone lay ers un der lain by black mudstone have grad ual tran si tions at their base, via the ap pear ance of in - di vid ual white laminae which in crease up wards in thick ness and den sity (RR 1/07, RR 9/06, RR 6A, RR 5/06; Fig. 5). Some lime stone lay ers over lain by sand stones dis play, at their tops, struc tures at trib ut able to ero sion dur ing sand de po si tion (RR 2/07 and RR 8/06; Fig. 5).

HOST DEPOSITS OF THE TYLAWA LIMESTONES AT TYLAWA AND RUDAWKA RYMANOWSKA The lay ers of the Tylawa Lime stones are in ter ca lated with var i ous de pos its that change along the sec tions (Figs. 2–5).

These in clude: thin- and me dium-bed ded grey, micaceous, cal - car e ous sand stones, which may be very fine-grained and fine-grained, less fre quently me dium-grained. The sand stone lay ers dis play hor i zon tal, wavy, and cross-lam i na tion, rarely con vo luted lam i na tion, cor re spond ing to Tc–d Bouma di vi sions.

The shales in this sec tion are grey, rarely dark brown, marly.

Non-lam i nated lime stones of Dynów Marl-type (lime stone is the main li thol ogy of the lithostratigraphic unit de scribed as the Dynów Marls by Kotlarczyk and Leśniak, 1990) are pres ent in this sec tion as micritic and marly lime stones, of yel low or brown hue and grey bands on freshly bro ken sur faces. Cur - rent-lam i na tion and gra da tion, vis i ble as grad ual col our change, are lo cally pres ent in the lime stones. Centi metre-scale si lici fied zones are pres ent within the lime stones at some lev els in the form of lenses, nodes, di ag o nal veins and meshworks.

Fig. 4. Lithological col umn of the Tylawa Lime stones at Rudawka Rymanowska as logged in 2006 and 2007

with po si tion of sam ples re ferred to in this pa per Ex pla na tions as in Fig ure 2

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The Tylawa Limestones – a regional marker horizon in the Lower Oligocene of the Paratethys: diagnostic characteristics from the type area839

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840Agnieszka Ciurej and Grzegorz Haczewski .

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Fig. 6. Thin sec tions of Tylawa Lime stones from Tylawa

A, B – lower clus ter (TYL 3/07); C, D – mid dle clus ter (TYL 5/07); E, F, G – up per clus ter (TYL 9A/07). Thick light laminae com posed of coccolithophores (Fig. 7) are sep a rated by thin ner dark laminae, com posed of de tri tal ma te rial (Fig. 8). All laminae are lat er ally con tin u ous and have undulose bound aries. Dis tinct pelletal struc tures com posed of coccolithophores are pres ent in all light laminae. Their size, shapes, and dis tri bu tion vary within in di vid ual laminae. Op ti cal mi cro scope: 1N – plane po lar ized lightl, XN – crossed polars. X,Y, Z – po si tion of light laminae and pel lets en larged in Fig ure 7

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On weath ered sur faces the lime stones are char ac ter is ti cally whit ish to light-grey. The Dynów Marl-type lime stone lay ers are from a few milli metres to a few tens of centi metres thick.

Their bound aries with the en com pass ing de pos its are sharp and dis tinct. The sec tion stud ied in cludes also black and dark-brown cherts up to 20 cm thick and grey, black, less fre - quently green and grey-green marly and car bon ate-free claystones and mudstones.

MICROSCOPIC CHARACTERISTICS OF THE TYLAWA LIMESTONES

When ex am ined in thin sec tion us ing an op ti cal mi cro - scope, the Tylawa Lime stones dis play very thin lam i na tion com posed of al ter nat ing light and dark laminae (Fig. 6). The light laminae, 20–300 mm, ex cep tion ally up to 600 mm, in thick ness, have a struc ture de scribed as micronodular lam i -

Fig. 7. SEM–CCI im ages from thin sec tions, show ing coccolithophore re mains in light laminae in var i ous states of pres er va tion A – mas sive ac cu mu la tion of well-pre served coccospheres; B, C, D – var i ous frag mented coccospheres and coccoliths. Note the minimal al ter ation by dis - so lu tion, over growth or com pac tion; signs of ad vanced diagenesis are seen only lo cally (lower right of D); E – as so ci a tion of var i ous frag ments of coccoliths and in tact coccospheres (up per right part) within laminae. Alteration by dis so lu tion, over growth or com pac tion is seen only lo cally (lower and mid dle part). Ar rows in C and E mark bound aries of pel lets. Po si tions of A, B, C shown in Fig ure 6A: X – C, Y – B, Z – A. D – sam ple TYL 8/07; E – sam ple TYL 9B/07

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nated (Haczewski, 1989), with ovoidal pel lets, av er ag ing 50 x 150 mm in size, ar ranged in hor i zon tal laminae. The pel lets are in ter preted as fae cal pel lets of zoo plank ton (see Haczewski, 1989; Ciurej, 2009). The laminae dif fer in pel let size, shape and pack ing. These dif fer ences re sult in fluc tu at ing thick nesses of the laminae and in the na ture of their bound aries – more or less undulose, and more or less sharp.

Anal y sis by SEM, in CCI mode, re vealed that coccolitho - phore skel e tons are the main com po nent of the light laminae (Fig. 7). Nearly all the coccolithophore skel e tal ma te rial is packed in pel lets. The cal car e ous nannofossils are rep re sented by a low-di ver sity as sem blage dom i nated by Reticulofenestra ornata Müller (see Ciurej, 2009). Pres er va tion of the cocco - lithophore ma te rial is very good in most of the laminae stud ied.

There is lit tle in di ca tion of dis so lu tion or sec ond ary over - growth and of me chan i cal frag men ta tion by com pac tion. A strik ingly large part of the cocccolithophore ma te rial is pre - served as in tact coccospheres (Fig. 7A). The scarce ma trix in the light laminae con sists of clay min er als, car bon ate grains, py rite and or ganic mat ter and it is pres ent within pel lets as well as be tween them.

The typ i cal dark laminae are thin ner than the light ones, be - tween 3 and 30 mm in most cases, ex cep tion ally up to 100 mm (Fig. 6). About half of the dark laminae are thin ner than 10 mm.

Anal y sis of the laminae by SEM us ing BSE mode re veals that they are com posed of clay min er als (most likely kaolinite and illite), quartz, feld spars, car bon ate min er als (cal cite, an ker ite, sid er ite, and do lo mite), py rite, phos pho rus de bris (fish de bris)

and or ganic mat ter (Fig. 8). Ghosts of pennate di a toms are pres - ent as de formed voids and in dis tinct im prints (see Ciurej, 2009).

CONCLUSIONS

Iden ti fi ca tion of the Tylawa Lime stones on the grounds of their mesoscopic li thol ogy may be prob lem atic be cause of vari - a tion in con trast and col our of laminae. Mi cro scopic ex am i na - tion by op ti cal mi cro scope and SEM pro vides more lithological and micropaleontological di ag nos tic cri te ria that may be sum - ma rized as fol lows:

– ab sence of foraminifers,

– mass oc cur rences of Reticulofenestra ornata Müller, – voids af ter pennate di a toms,

– dark laminae that are more dis tinct and in di vid ual in nature than in the Jasło Lime stone.

Ac knowl edge ments. This study was partly fi nanced by the Min is try of Sci ence and Higher Ed u ca tion (MNiSW) grant 18.18.140.652 to GH and by the Na tional Sci ence Cen tre (NCN) grant 2011/01/D/ST10/04617 to AC. The mi cro scopic study was done by AC within a PhD pro ject su per vised by GH.

The gen eral de scrip tion and in ter pre ta tion has been writ ten by both au thors. We ap pre ci ate help ful re views by M. Melinte- Do brinescu and H. M. Schulz and the re vi sion of the Eng lish text by J. Zalasiewicz..

W

Tm P

P

P Tm

Tm

Tm Tm

Tm

Tm P

P P

A B

Fig. 8. SEM–BSE im ages from thin sec tions, show ing com po nents within dark laminae

A – as so ci a tion of var i ous amounts of de tri tal ma te rial (clay min er als, quartz, feld spars), py rite, car bon ate grains and or ganic mat ter; note the dif fer ence in size of de tri tal ma te rial; B – pre dom i nance of py rite and fin est de tri tal ma te rial (clay min er als, quartz, feld spars); Tm – de tri tal ma te rial (clay min er als, quartz, feld spars); P – py rite; W – car bon ate grains; out lines – or ganic mat ter. A – sam ple TYL 8/07; B – sam ple TYL 9B/07

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