Geo log i cal Quar terly, 2017, 61 (3): 682–695 DOI: http://dx.doi.org/10.7306/gq.1369
En vi ron men tal stress in the north ern Tethys dur ing the Paleogene: a re view of foraminiferal and geo chem i cal re cords from the Pol ish Outer Carpathians
Barbara OLSZEWSKA1 and Andrzej SZYD£O1, *
1 Pol ish Geo log i cal In sti tute – Na tional Re search In sti tute, Carpathian Branch, Skrzatów 1, 31-560 Kraków, Po land
Olszewska, B., Szyd³o, A., 2017. En vi ron men tal stress in the north ern Tethys dur ing the Paleogene: a re view of foraminiferal and geo chem i cal re cords from the Pol ish Outer Carpathians. Geo log i cal Quar terly, 61 (3): 682–695, doi: 10.7306/gq.1369 Dur ing the Paleogene, the area of the north ern Tethys was con trolled by a tur bid ity sys tem stim u lated by di a strophic and geodynamic pro cesses. These fac tors con trib uted to the dis per sion and rapid ox y gen a tion of or ganic de bris. Its ac cu mu la - tion was a con se quence of stag nant bot tom wa ter con di tions that pe ri od i cally oc curred in the ba sin. In these pe ri ods, in tense de com po si tion in ten si fied by hy dro ther mal and diagenetic pro cesses was as so ci ated with ox y gen con sump tion and the re - lease of green house gases, which led to hypoxia and acid i fi ca tion. These phe nom ena in ten si fied by ther mal and den sity strat i fi ca tion had a ma jor im pact on the struc ture, evo lu tion and dis tri bu tion of biota. Stress as so ci ated with rap idly chang ing con di tions in duced by sed i men tary pro cess and upwelling re sulted in the dom i nance of forms that col o nized most sed i ments (Glomospira, Ammodiscus, Recurvoides, Rzehakina) and sur face wa ters (Guembelitria, Chiloguembelina, Globanomalina, Globigerina, Cassigerinella, Catapsydrax). At the time, foraminifera were lim ited to low-di ver si fied eutrophic as sem blages or were mainly re placed by si li ceous phytoplankton (radio lar ians and di a toms). Geo chem i cal data con firm that en vi ron men tal cri ses in the Paleogene ba sin took place un der chang ing ther mal con di tions that re flect global events (KTBE, PTME, EEOC and TTE). Ther mal stress fa vour ing the for ma tion of cer tain min er als or rocks oc ca sion ally oc curred dur ing the Paleocene to Eocene (sid er ite, phos phates) and dom i nated in the Early Oligocene (sil ica).
Key words: Outer Carpathians, Po land, Paleogene, foraminifera, geo chem is try.
INTRODUCTION
The Paleogene was a pe riod of ma jor changes in ocean cir - cu la tion and global cli mate, in duced by re or ga ni za tion of tec - tonic plates, ac com pa nied by in tense vol ca nic and di a strophic ac tiv i ties and sea level fluc tu a tions (Haq et al., 1988; Vogt, 1989). These ex ter nal fac tors in flu enced the ac cu mu la tion and pres er va tion of or ganic de bris in ma rine de pos its (Calvert and Pederson, 1992). Its de com po si tion as so ci ated with ox y gen con sump tion led to an oxia. The spread of these con di tions in the ba sin de pended not only on the wa ter tem per a ture and sa - lin ity, but also on the in ten sity of hy dro ther mal and diagenetic pro cesses (Brener, 1984; Tucker, 1991; Katz et al., 2001).
These pro cesses as so ci ated with the re lease of vol ca nic and biogenic gases and flu ids (CO2, NH3 and SiO2) also fa voured the for ma tion of min er als (phosphorite, sid er ite) which con trib - uted to cal cium uti li za tion and acid i fi ca tion (Zachos et al., 2005;
Wil liams et al., 2017).
Through most of the Paleogene, ox i da tive and geo chem i cal stress took place un der warm “green house” cli ma tic con di tions (Zachos et al., 2001; Pujalte et al., 2009). The warm ing trend
started at the Maastrichtian-Paleocene tran si tion and in ten si - fied at the Paleocene-Eocene Ther mal Max i mum (PETM), cul - mi nat ing in the Early Eocene (EECO) (Fig. 1). Af ter this cli ma tic op ti mum, short-term warm ing events oc curred un til the end of the Eocene (Bohaty and Zachos, 2003; Röhl et al., 2005;
Thomas et al., 2006; Luciani et al., 2016). Futher cli mate change oc curred close the Eocene/Oligocene bound ary. At that time the clo sure of the Tethys sea way (Ter mi nal Tethyan Event – TTE) and lim ited ma rine con nec tions be tween the In dian Ocean and the At lan tic led to per tur ba tions in the ocean cir cu la - tion and sea level fluc tu a tions which re sulted in a cool ing ef fect (Barron and Baldauf, 1989; Miller et al., 2009). How ever, this trend was in ter rupted by the warm ing ep i sode in the Late Oligocene ~26 Ma (Miller et al., 1987; Zachos et al., 2001; Villa and Persico, 2006; Pekar et al., 2006).
Un der these cli mate con di tions, en vi ron men tal stress af - fected the num ber and struc ture of the biota to a vari able de gree.
It usu ally cre ated op por tu ni ties for the es tab lish ment and sur vival of new forms and fa voured op por tu nis tic spe cies of an i mals or plants that are adapted to ex ploit newly avail able hab i tats or re - sources and can be rec og nized as in di ca tors of eutrophic en vi - ron ments (Levinton, 1970; Dimichele et al., 1987; Frezza et al., 2005; Alegret et al., 2012). Foraminifera in clude taxa that tol er ate a wide range of en vi ron men tal con di tions. The dis tri bu tion of these or gan isms is de ter mined by ox y gen and food avail abil i ties (Gooday, 1990; Kuhnt et al., 1996; Stigter et al., 1998; Heinz et al., 2001; Alegret and Thomas, 2009, 2013; Arreguín-Rodríguez et al., 2013). The ex tinc tion of spe cial ized forms with mas sive
* Corresponding author, e-mail: andrzej.szydlo@pgi.gov.pl
Received: March 21, 2017; accepted: April, 18, 2017; first published online: July 28, 2017
and or na mented tests, which be long to k-strat e gists, and the ap - pear ance of low-ox y gen and acid i fi ca tion tol er ant dwarf r-strat e - gists can be iden ti fied as an ex am ple of adap tive ra di a tion as so - ci ated with dras tic eco log i cal changes that took place close to the Maastrichtian-Paleocene, Paleo cene-Eocene and Eocene- Oligo cene bound aries (MacLeod, 1993; Luciani et al., 2016). At the end of the Paleocene (~57 Ma), changes in hy dro ther mal ac - tiv ity and cir cu la tion in bot tom wa ters and at mo sphere, ac com - pa nied by global warm ing (green house ef fect), led to per tur ba - tions in ma rine en vi ron ments that re sulted in global an oxia (Rea et al., 1990; Ken nett and Stott, 1991; Stott, 1992; Speijer et al., 1997; Bains et al., 2000; Fig. 1). The PETM event (~55.5 Ma) is char ac ter ized by glob ally el e vated tem per a tures and ma jor bi otic changes on land and in the oceans, in clud ing the ex tinc tion of deep-wa ter ben thic foraminifera (Galeotti et al., 2004; Arreguín - -Rodríguez et al., 2013). At that time, ma rine plank ton and ter - res trial or gan isms were sig nif i cantly dif fer en ti ated, while nu mer - ous spe cies of flysch-type as sem blages be came ex tinct (Kaminski et al., 1995; Kelly et al., 1998; Kelly, 2002). Ben thic foraminiferal sur vived in ho mo ge neous eutrophic as sem blages in clud ing spe cies of the Glomospira (Biofaces B) biofacies (Kaminski, 2005; Arreguín-Rodríguez et al., 2013; Fig. 1). A de - cline of acarininids and foraminiferal benthos is par al leled by a marked in crease in car bon ate con tent of sed i ments. It sug gests that these in ter vals of car bon ate en rich ment, and its spe cific micro fauna, re flects stepwise en hanced car bon par tic i pa tion in ma rine en vi ron ments, in duced by in creas ing con cen tra tions of at mo sphe ric car bon di ox ide lead to an in crease in sea sur - face tem per a tures and in tense flu vial in put of or ganic-rich terrigenous ma te rial from the ad ja cent land un der hu mid cli mate con di tions at that time (Kelly, 2002; Giusberti et al., 2007;
Taucher et al., 2012). Among cal car e ous foraminifera, aer o bic and oligo tro phic as sem blages were both re placed by spe cies re - flect ing low ox y gen a tion and en riched with forms oc cur ring in en - vi ron ments that were pre vi ously lim ited to con ti nen tal shelf (Speijer et al., 1997).
Af ter the ther mal op ti mum, a cool ing trend be came wide - spread in the Late Paleogene. Rapid changes were sep a rated by in ter vals of more sta ble con di tions and oc ca sional warm ing pe ri ods (Berger, 1972; Barron and Baldauf, 1989). The ma jor cool ing in ter val in the Early-Mid dle Eocene and the ear li est Oligocene re flect the re ver sal of the cli mate trend seen dur ing the Early Paleogene. It re sulted from changes in ocean wa ter cir cu la tion and upwelling, which ini ti ated the pro cess of mov ing masses of cold wa ter to the sur face. Un der these set tings the ac tiv ity of si li ceous plank ton abruptly in creased (Fig. 1). The dom i nance of these forms was closely at trib uted to nat u ral pro - cesses (strat i fi ca tion and upwelling) which led to eutrophication.
Low-di ver sity or monospecific as sem blages can also be as so ci - ated with brack ish estuarine wa ters re flect ing river in flux (di a - toms) or mixed wa ters in the tidal zone (radio lar ians) (Bolto - vskoy et al., 2003; De Wever et al., 2003). In tense de com po si - tion of this biogenic and ter res trial plant ma te rial on the sea floor was as so ci ated with the con sump tion of ox y gen, which led to anoxic bot tom con di tions (Vetö, 1987). Poorly di verse epifauna and some shal low- or deep-wa ter infauna pre fer this hos tile en - vi ron ment in clud ing or ganic-rich sed i ment and cold sta ble bot - tom wa ters (Sen Gupta et al., 1993; Kaminski et al., 1995;
Kaminski et al., 1999; Nagy et al., 2009).
Changes in wa ter geo chem is try also re flect a cri sis in the ma rine en vi ron ment (Zachos et al., 2005). This is man i fested by en rich ment in trace el e ments and chem i cal com pounds re sult - ing from the de com po si tion of or ganic mat ter, ac tiv ity of or gan - isms, and the im pact of vol ca nic and cli mate fac tors. Oganic car bon and car bon and hy dro car bon biomarkers usu ally in di - cate in tense de com po si tion of land- and ma rine-de rived or - ganic mat ter ow ing to mi cro bial pro cesses on the sea floor (Lange et al., 2000). Un der these con di tions shaped by sub ma - rine vol ca nism, green house gases were re leased: car bon ate di - ox ide and meth ane (Vogt, 1989; Jar dine, 2011). An in crease in the con tent of these prod ucts usu ally re sults in both low-ox y gen con di tions in the ba sin and a warm ing ef fect on the sur round ing Fig. 1. Global oce anic palaeo geo graphi cal, palaeoenvironmental and palaeo bio logi cal events in the Lat est
Me so zoic and Ce no zoic with re spect to the geo chron ol ogy and sea level curve, re spec tively (Berggren et al., 1985; Haq et al., 1987; Aubry et al., 1988; Kuhnt et al., 1992; Erbacher et al., 1999; Kaminski et al., 1999;
Keller and Padro, 2004; Kaminski, 2005)
lands. These en vi ron men tal trends, which led to the elim i na tion of ma rine ben thic fauna and in tense veg e ta tion on land, were ev i denced by the pres ence of kaolinite (Thiry, 2000). Other clay min er als (mont mo ril lo nite), trace el e ments (Zn, V), and min eral rocks (phos phates) re flect the early diagenesis of sed i men tary and vol ca nic de pos its caused by the ac tiv ity of ma rine wa ter, chem i cal com pounds and green house gases re leased dur ing the de com po si tion of or ganic de bris and hy dro ther mal ac tiv ity (Compton et al., 2000; Maslennikov et al., 2012). These pro - cesses led to in tense ox y gen con sump tion. The ex tended an - oxia in strat i fied and cold wa ters fa voured the for ma tion of sid - er ite on con ti nen tal shelves (Berner, 1984; Tucker, 1991;
Melinte-Dobrinescu and Roban, 2011).
Fluc tu a tions in the ocean cir cu la tion, sea level, the car bon cy cle, and cli mate that con trib uted to sea sur face pro duc tiv ity or bot tom con di tions dur ing the Paleogene have been iden ti fied by the anal y sis ben thic and planktic foraminifers and geo chem i - cal in di ces from the flysch de pos its in the Outer Carpathian Ba - sin. In this mar ginal ba sin of the north ern Tethys, de po si tion of siliciclastic-car bon ate turbidities pre vailed. The flysch se ries dom i nated by sand stones in clude shales and lo cal marls that may re flect en vi ron men tal per tur ba tions as so ci ated with changes in wa ter cir cu la tion and geo chem is try. The wide - spread oc cur rence of these con di tions was in ten si fied by ther - mal and sa lin ity changes in the ba sin stud ied. The Paleogene flysch se ries from the Pol ish Outer Carpathians are ex am ined
in or der to un der stand en vi ron men tal stress and its ex ter nal set - tings. This anal y sis is based on orig i nal, ar chived and pub lished re sults to de ter mine whether it could oc cur un der the in flu ence of global and re gional fac tors.
GEOLOGICAL AND SEDIMENTOLOGICAL REMARKS
En vi ron men tal changes in the north ern Tethyan Sea were ana lysed based on foraminiferal and geo chem i cal in dex from the Paleogene flysch se ries of the Pol ish Outer Carpathians (Fig. 2). Dur ing the Paleogene the study area was a mar ginal ba sin very sen si tive to rel a tive sea level changes. In this area, pres ently di vided into tec tonic zones, the sed i men tary sys tem dom i nated by tur bid ity cur rents was strongly con trolled by geodynamic pro cesses (Oszczypko, 2004; Jankowski, 2015).
Un der these set tings, turbiditic siliciclastic-car bon ate de - pos its formed (Koszarski et al., 1974; Œl¹czka and Kaminski, 1998). Those de pos ited un der low sed i men ta tion rate con di - tions re flected en vi ron men tal stress as so ci ated with abrupt changes in the wa ter cir cu la tion and chem is try. They are rep re - sented mainly by shales and oc ca sional marls with siderites, phos phates (Paleocene), tuffites (Paleocene-Eocene) and cherts (Lower Oligocene) and of ten oc cur within sand stone se -
684 Barbara Olszewska and Andrzej Szyd³o
Fig. 2. Lo ca tion of se lected out crops and bore holes on the back ground of tec tonic units of the Pol ish Outer Carpathians (mod i fied from ¯ytko et al., 1989; Oszczypko, 2006)
1 – Ustroñ (Istebna Fm.), 2–4 – vi cin ity of ¯ywiec Lake (Istebna Fm.; 2 – Ma³a Tresna, 3 – Oczków, 4 – Wilczy Jar), 5 – Istebna-Olza-Olecka re gion (Istebna Fm.), 6 – Kamesznica (Istebna Fm.), 7 – Kêty (Var ie gated Shales), 8 – Wadowice (Menilite Fm.), 9 – Leñcze (Menilite Fm.), 10 – Harbutowice (Menilite Fm.), 11 – Skawinki (Menilite Fm.), 12 – Myœlenice (Menilite Fm.), 13 – Stró¿e (Menilite Fm.), 14 – Mszana Górna (Menilite Fm.), 15 – Cieniawa (Menilie Fm.), 16 – Klêczany (Menilite Fm.), 17 – Tabaszowa (Istebna Fm.), 18 – Bieœnik (Var ie gated Shales), 19 – Maœlana Góra (Var ie gated Shales), 20 – Ropa, 21 – Magdalena (Menilite Fm.), 22 – G³adyszów (W¹tkowa Sand stones, G³adyszów Beds), 23 – Sêkówka (Var ie gated Shales, Magura Beds, Menilite Fm.), 24 – Dukla (Majdan Beds), 25 – Trzciana (var ie gated shales in Magura Beds), 26 – Wêglówka (var ie gated marly and shaly de pos its), 27 – Czarnorzeki (Istebna Fm.), 28 – Godowa (Krosno Fm.), 29 – Jasionów (Var ie gated Shales), 30 – Po³omia (Czudec Clays), 31 – Komañcza (Majdan Beds, Var ie gated Shales, Menilite Fm.), 32–34 – Cisna-Majdan-Solinka (Majdan Beds), 35–37 – Baligród-Bystre-Rabe (Menilite Fm., Krosno Fm., Istebna Fm.), 38 – Harta (Krosno Fm.), 39 – Hy¿ne (Var ie gated Shales, Hi ero glyphic Fm.), 40 – Bezmiechowa (Wêglówka Marls), 41 – Krêpak (Menilite Fm.), 42 – Leszczawa Górna (Menilite Fm.), 43 – Ropienka (Menilite Fm.), 44 – Cisowa (Menilite Fm.), 45 – Brzegi Dolne (Menilite Fm.), 46 – Hulskie (Krosno Fm.), 47 – Czarna Góra (Krosno Fm.)
ries in dif fer ent pro por tions and lo cally form in de pend ent lithofacies (e.g., Var ie gated Shale Fm., Wêglówka Marls; Fig.
3). Dur ing the Paleocene-Eocene, shales and marls dom i nated in the ex ter nal (Skole and Subsilesian units) and, lo cally, in the in ner (north ern part of the Magura Unit) zones of the Pol ish Outer Carpathians. In the Oligocene, shales (Menilite Fm.) be - came the dom i nant lithofacies (Koszarski et al., 1974; Malata, 1997; Œl¹czka and Kaminski, 1998; Fig. 3). Their dis tri bu tion was strongly con trolled by geotectonic and geodynamic pro - cesses. Un der these con di tions, the ba sin was fre quently di - vided into in ter con nected sub-bas ins (Ksi¹¿kiewicz, 1962;
Golonka et al., 2000; Jankowski, 2015). As a con se quence of this sub di vi sion, de pos its that pre vi ously ac cu mu lated in the same ba sin cur rently be long to dif fer ent tec tonic units. Their com par i son shows that only the Magura, Silesian and Skole sub-bas ins could be con sid ered as in de pend ent sed i men tary ar eas. While the Subsilesian and Silesian zones were closely re lated to each other, the Dukla Zone, which was a tran si tional area be tween the Silesian and the Magura zones, was in di vid u - al ized and trans formed dur ing the Paleogene (Cieszkowski, 2001; Oszczypko, 2004).
Per tur ba tions in ma rine eco sys tems, strongly de ter mined by tec tonic his tory and geo log i cal fac tors, also re flect ma jor palaeogeographic and bi otic events. These re la tions with re - spect to en vi ron men tal stress dur ing the Paleogene are dis - cussed in this study.
MATERIAL AND METHODS
The study is based on sam ples col lected from Paleogene de pos its of the Silesian, Subsilesian and Dukla units (Fig. 3). The re sults in clude also the data from the Magura and Skole se ries, which was partly pub lished by the pres ent au thors and oth ers.
Rock ma te rial was col lected dur ing geo log i cal map ping of the Pol ish Outer Carpathians on the scale of 1:50,000, and dur ing re search con ducted by the au thors. Most of the sam ples were taken from out crops, but some of them come from bore holes.
Sam pled rocks were dis in te grated by boil ing and freez ing at the lab o ra tory of the PGI-NRI Carpathian Branch in Kraków. The micropalaeontological anal y sis and pho to graphic doc u men ta tion of se lected ma te rial (63 mm) was per formed us ing a ste reo scopic op ti cal mi cro scope (Zeiss Ste reo Dis cov ery.V12). The col lected microfossils are de scribed with spe cial fo cus on the re la tion ship be tween test mor phol ogy and liv ing or feed ing strat egy, eco log i - cal pref er ences and fos sil iza tion po ten tial (Jones and Charnock, 1985; Corliss, 1985, 1991; Bernhard, 1986; Corliss and Chen, 1988; Nagy et al., 1995; Kaminski and Kuhnt, 1995). These re - sults are com pared with palaeogeographic events shaped by sea level and ox y gen a tion changes in ma rine en vi ron ments.
Micropalaeontological data are dis cussed with re spect to wa ter geo chem is try and cli mate fluc tu a tions doc u mented by geo chem - i cal in di ces, in clud ing trace el e ments and min er als and chem i cal com pounds pre served in shales. These data are cor re lated with sed i men tary pro cesses and bi otic events re flect ing en vi ron men - tal cri ses dur ing the Paleogene. Changes in the di ver sity and num ber of foraminifera ob served by the au thors are re ported with re spect to both other microfossils (radio lar ians, di a toms, al - gae) and geo chem i cal data that are part of ar chived and pub - lished stud ies (Wieser and Gucwa, 1977, 1980; Muszyñski et al., 1979; Gucwa and Œl¹czka, 1980; Olszewska, 1984, 1985;
Gucwa, 1990; Gucwa and Poprawa, 1996; Dziubiñska and Narêbski, 2004; Bieñkowska-Wasiluk, 2010; Zieliñska, 2010,
2017; Garecka, 2012; Salata and Uchman, 2012, 2013; Szyd³o and Olszewska, 2012; Œl¹czka et al., 2014; Dziadzio et al., 2016). The re sults com piled by au thors are pre sented against the geo chron ol ogy and the strati graphic po si tion of the stud ied de pos its (Fig. 4).
MICROPALAEONTOLOGICAL AND GEOCHEMICAL DATA
In the Paleogene flysch se ries, en vi ron men tal stress and its ex ter nal set tings are mainly ev i denced by foraminiferal and geo chem i cal data. The most wide spread fos sil group is the ag - glu ti nated and cal car e ous ben thic foraminifera that are closely re lated to the sed i ment and ma rine wa ters, and re flect depo - sitional con di tions and their du ra tion. Ag glu ti nated foraminifers, as the most nu mer ous group in the study area, in clude mainly autochthonous forms with tests ce mented by sil ica and some - times cal cium car bon ate. Planktic and cal car e ous ben thic forms oc cur only in parts of the stud ied de pos its that ac cu mu - lated dur ing some in ter vals of the Paleogene. These forms are more nu mer ous in the Paleogene Subsilesian se ries and the Up per Eocene-Oligocene de pos its of other tec tonic zones (Huss, 1957; Jurkiewicz, 1967; Jednorowska, 1975; Olsze - wska, 1980; Morgiel and Olszewska, 1978, 1981; Morgiel and Szymakowska, 1978; Olszewska et al., 1996; Olszewska, 1997b). Due to the high fos sil iza tion po ten tial, foraminifera are used for palaeo eco logi cal and biostra tigraphical re search in the Pol ish Outer Carpathians (Geroch et al., 1967; Ksi¹¿kiewicz, 1975; Geroch and Nowak, 1984; Olsze wska, 1985, 1997a;
Geroch and Koszarski, 1988; Fig. 3). The char ac ter is tics of this group with re spect to other microfossils (radio lar ians, di a toms and al gae) and geo chem i cal data are dis cussed in this chap ter.
PALEOCENE
In the Paleocene dark shales of the Istebna (Silesian Unit) and Majdan Beds (Dukla Unit), siderites and ag glu ti nated fora - minifera ce mented by sil ica are found. Spe cies be long ing to the gen era: Glomospira (G. charoides, G. diffundens, G. gordialis), Glomospirella (Gl. grzybowskii) and Rzehakina (Rz. epigona, Rz. fissistomata, Rz. sim plex) are re cov ered from all study ar - eas west of the So³a River and near the Dunajec River and east of it (Fig. 2). Rep re sen ta tives of the gen era Haplophragmoides (H. horrides, H. mjatlukae, H. stomatus), Recurvoides (R. nu - cle o lus, R. walteri) and Recurvoidella (Re. lamella) are found mainly in lo cal i ties sit u ated in the east ern part of the Pol ish Outer Carpathians. They are oc ca sion ally ac com pa nied by ag - glu ti nated foraminifera of the gen era Kalamopsis, Ammo dis - cus, Caudammina, Trochamminoides, Saccammina, Reophax and Bolivinopsis (Fig. 4). Some of these gen era are also re - ported from var ie gated shales of the Istebna For ma tion. Other si li ceous and cal car e ous microfossils also spo rad i cally oc cur in these se ries. The for mer are rep re sented by radio lar ians and di - a toms dis persed in the stud ied de pos its or are pres ent at the top of them, while cal car e ous foraminifera oc ca sion ally oc cur in muddy flows and shales. The ap pear ance of cal car e ous forms, which was re ported from the vi cin ity of ¯ywiec Lake (Nescieruk and Szyd³o, 2003), was also con firmed in the Krosno re gion (Figs. 2 and 4). Sin gle spec i mens of cal car e ous ben thic (Nutta - lides trumpyi, Gyroidinoides nitidus) and planktic spe cies (Eoglo bigerina trivialis, Subbotina triloculinoides, Chiloguem -
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pseudobulloides) are char ac ter is tic for these as sem blages.
Rarely, they con tain Planorotalites pseudo menardii and Acarinina mcanai that in di cate the up per part of the Paleocene (Fig. 4). Or ganic de bris also ac cu mu lated in mudstones and mudstone-sandy se ries of the Istebna For ma tion (Zieliñska, 2010, 2017). This abun dant and usu ally dis persed ma te rial of ter res trial or i gin co-ex ists with very rare dinocysts in sam ples from the vi cin ity of Kamesznica (Szyd³o et al., 2015a, b).
Sim i lar ag glu ti nated as sem blages with Rzehakina were also doc u mented in other tec tonic units of the Pol ish Outer Carpa - thians (Jurkiewicz, 1967; Jednorowska, 1975; Olsze wska et al., 1996). It was con firmed by the au thors in the Subsilesian (Wêglówka Marls), Dukla (Majdan Beds) and Ma gura se ries (Var ie gated Shales) (Fig. 4). More over, foramini feral and radio - larian plank ton found in the Istebna For ma tion was also de - scribed in var ie gated de pos its of the Subsilesian (Huss, 1957;
Jedno rowska, 1975; Olszewska, 1980; Waœkowska -Oliwa, 2005, 2008) and Dukla units (Olszewska, 1980). How ever, they usu ally con tain nu mer ous planktic foraminifera. These forms, be long ing mainly to the gen era Globoconusa (Glc. daubjer - gensis), Preamurica (Pr. ucinata), Morozovella (M. angu lata), Eoglo bigerina (E. fringa), Subbotina (S. trilo culi noides), Para - subbotina (P. pseudobulloides) and Chiloguem belina (Ch.
morsei, Ch. crinita), some times co-ex ist with cal car e ous ben thic taxa (Nutta lides, Anomalina) (Fig. 4). In ad di tion, spec i mens of Guembelitria are oc ca sion ally found in shales ac com pa nied with the Inocera mian sand stones of the Skole Unit at the Cre ta - ceous/Paleogene bound ary (Gasiñski and Uch man, 2011).
Or ganic mat ter is usu ally ox i dized in var ie gated de pos its.
How ever, shaly marls of the Subsilesian Unit (Bezmiechowa) lo cally con tain or ganic mat ter of ma rine or i gin (Szyd³o et al., 2015b), while the var ie gated shales of the Skole Unit con tain phos phates and lenses of black clayey and muddy flows which also oc cur in the Babica Clays (Franus and Rajchel, 2002;
Szyd³o et al., 2014; Fig. 4). Pyritization pro cess was ob served in these se ries (Szyd³o et al., 2014).
EOCENE
Ho mo ge neous ag glu ti nated foraminiferal as sem blages con tain ing Glomospira spe cies (G. charoides, G. gordialis), and as so ci a tions with Saccamminoides (Sa. carpathicus) are char - ac ter is tic for the Early Eocene (Jurkiewicz, 1967). This micro - fauna is known from shales of var ie gated colours (var ie gated shales) which are ac com pa nied by the Ciê¿kowice (Silesian Unit), the Magura (Magura Unit) and the Hi ero glyphic sand - stones (Dukla and Skole units) or form sep a rate litho - stratigraphic units (Var ie gated Shales) in the Subsilesian zone (Olszewska, 1973, 1980; Waœkowska, 2008, 2015; Fig. 2).
Over most of the study area the Eocene shales con tain Bolivinopsis spectabilis and, lo cally, Ammodiscus latus, which pe ri od i cally oc cur in high num ber (Fig. 4). Var ie gated shales of the Skole Unit were de pos ited in the Paleocene-Eocene. They con tain radio lar ians, tuffites, spe cific min er als: mont mo ril lo nite and kaolinite (Fig. 4), Mn and Fe ox ide mi cro-con cre tions, and Mn, Fe, Mg and Ca ox ides and car bon ate con cre tions (Muszyñski et al., 1979; B¹k et al., 1997; Franus and Rajchel, 2002). Changes in plank ton were also ini ti ated at that time. This bi otic pro cess con tin ued to the Mid dle Eocene and was as so ci - ated with the oc cur rence of Morozovella (M. marginodentata), Acarinina (A. spinoinflata, A. bulbrooki), Turborotalia (T.
frontosa) and Hantenkina spe cies, which were de scribed from sam ples col lected by the pres ent au thors (Fig. 4) and oth ers
(Nowak, 1954; Gasiñski, 1978). Some of them were found in black clays that oc ca sion ally oc cur in the Skole se ries (Hi ero - glyphic For ma tion). Ben thic taxa of the ge nus Reticulo phra - gmium (Ret. amplectens, Ret. rotundidorsatum), some times oc cur ring in low-di ver sity as sem blages (Jurkiewicz, 1967), were en coun tered in the Mid dle and Up per Eocene var ie gated shales of the Subsilesian (Kêty bore hole) and Dukla units (Komañcza; Olszewska, 1973; Fig. 4). Radiolarian ho ri zons in the Eocene var ie gated shales are usu ally as so ci ated with pyritization (B¹k and Barwicz-Piskorz, 2006).
OLIGOCENE
The next change among planktic foraminifera is ob served at the Eocene/Oligocene bound ary in most ar eas of the Pol ish Outer Carpathians (Olszewska, 1985). Mas sive and or na mented forms dis ap peared at that time. Thick-walled taxa of Globi - gerapsis in dex, Gs. coccoensis, Turbolotaria cerroazu lensis and Glb. amplipertura were re placed by small-sized spec i mens with spinose and thin-walled tests and glob u lar cham bers (Globi - gerina praebulloides, Glb. occlusa, Glb. ouachitaensis, Cassi - gerinella chipolensis, Glb. officinalis and Tenuitellinata livero - vskae), and oth ers hav ing partly cov ered ap er ture and an ad di - tional cham ber or ap er tures. Forms be long ing to Catapsydrax (C. dissimilis, C. unicavus), Globo rotaloides (Glo. suteri), Subbotina (S. droogeri), Globoquadrina (Gq. selli) oc cur both in the ex ter nal (Skole) and in ter nal (Magura) units (Fig. 4). They are ac com pa nied in the Menilite Beds by other forms be long ing to Globanomalina and Chilo guembelina, which are known from the Late Eocene var ie gated shales (Olszewska, 1973, 1985; Fig. 4).
The Eocene-Oligocene bound ary co in cides with al most to tal dis - ap pear ance of ag glu ti nated taxa that were re placed by cal car e - ous ben thic forms of the gen era Bolivina, Chilostomella, Allomorphina, Nonionella, Globo bulimina, Fur sen koina, Cau ca - sina, Virgulina and Virgu linella (Olszewska, 1985) found in the Dukla, Silesian and Magura units (Fig. 4). Benthos with pyritized tests is rep re sented by the ge nus Cibicides. These forms oc cur in or ganic -rich Menilite Shales that were wide spread in the Outer Carpathians dur ing the Oligocene (Olsze wska, 1985). Re mains of di a toms and fish are also found in these shales. Af ter the Early Oligocene dom i nance of cal car e ous benthos oc cur ring in ho mo - ge neous as sem blages, planktic foraminifera be came more nu - mer ous in the Late Oligocene. In shales of the Krosno sand - stones, as sem blages with ben thic and planktic op por tu nis tic forms (Globigerina officinalis, Glb. oua chitensis, Glb. praebullo - ides) were re placed by an as so ci a tion com posed of Tenuite - llinata angustiumbilicata, Te. cipero ensis and Te. post cretacea.
This type of micro fauna was found in mud flows (Fig. 4).
The Menilite Shales also in clude many trace and min eral el - e ments: Ni, Cr, Mn, Mo, Zn, V, Cu and SiO2. Among clay min er - als, mont mo ril lo nite pre vails (Wieser and Gucwa, 1977; Gucwa and Wieser, 1980; ten Ha ven et al., 1993; Gucwa and Poprawa, 1996). Some poarts of the Menilite Shales are pre dom i nantly of bi otic or i gin. More ex ter nal zones (Skole, Subsilesian, and Silesian units) abound in V and Mo, while the en rich ment in Cu is char ac ter is tic of the in ter nal part of the Pol ish Outer Carpathians (Gucwa and Œl¹czka, 1980; Gucwa, 1990; Fig. 4).
More over, hy dro car bon biomarkers, in clud ing norhopa nes/ho - pa nes, isoprenoids, diasteranes and oleananes, have been doc u mented in the Meniliite shales of the Silesian and Magura units. Hopane and sterane biomarkers have also been doc u - mented in the Up per Eocene green shales of the Silesian Unit (Sêkówka), which un der lie the Menilite Shales For ma tion in - clud ing si li ceous marls (Dziadzio et al., 2016).
688 Barbara Olszewska and Andrzej Szyd³o
CHANGES IN DEPOSITIONAL ENVIRONMENTS
The si li ceous-car bon ate flysch de po si tion heavily in flu enced the ma rine biota and pres er va tion of or ganic de bris. Hemipelagic de po si tion which pre vailed in the Subsilesian Zone and in part of the Magura and Skole zones was fre quently in ter rupted by the abrupt sup ply of coarse-grained terrigenous ma te rial in the Silesian and Dukla zones (Leœniak et al., 2001; Strzeboñski, 2015; Fig. 3). This pro cess, con trolled by tur bid ity cur rents, usu - ally led to me chan i cal de struc tion of biogenic ma te rial that was strongly re worked and rap idly ox i dized on the seafloor. Its de -
com po si tion dur ing long pe ri ods of low tec tonic ac tiv ity and lim - ited wa ter cir cu la tion con trib uted to ox y gen con sump tion and the re lease of green house gases (CO2, CH4) (Fig. 5). This pro cess, as so ci ated with the ac tiv ity of an aer o bic bac te ria and shaped by sub ma rine vol ca nism (tuffites), led to an oxia un der hu mid warm con di tions (kaolinite). This phe nom e non spread at dif fer ent range and time in the Outer Carpathian Ba sin. Dur ing pro gres - sive an oxia, foraminifera mi grate to the sed i ment and wa ter sur - face. Their dis tri bu tion on the sea floor re lated to life po si tion, their feed ing strat egy and test struc ture, and ox y gen avail abil ity (Jones and Charnock, 1985; Bernhard, 1986; Nagy et al., 1995;
Kaminski and Kuhnt, 1995; Kaminski, 2012). In strat i fied and tur - bid wa ters, ag glu ti nated and cal car e ous benthics oc curred as
Fig. 5. Hy po thet i cal di a gram il lus trat ing the ac tiv ity of ma rine mi cro or gan isms and a change in wa ter chem is try un der en vi ron men tal and cli ma tic con di tions: A – Paleocene-Eocene warm ing,
B – Oligocene cool ing (Praetorius et al., 2015, mod i fied)
690 Barbara Olszewska and Andrzej Szyd³o
epi- and infauna rep re sent ing de tri tus, de posit and bac te ria feed - ers. Dur ing pe ri ods of to tal an oxia in the bot tom wa ters the foraminiferal benthos was elim i nated, while shal low-dwell ing si li - ceous (radio lar ians, di a toms) and cal car e ous plank ton (foram - inifera) dom i nated in the sur face wa ters (Fig. 5).
In the Paleocene and Eocene, ac tive epifauna (Rzehakina, Ammodiscus) col o nized most sed i ments from coarse- to very fine-grained fa cies, at tach ing to the sub strate. It seems that be - cause of liv ing strat egy and en vi ron men tal pref er ences this small in vo lute epifauna and shal low-wa ter ovate infauna (Glomospira and Caudammina) were better adapted to the fre quently and rap idly chang ing en vi ron ments shaped by turbiditic de po si tion.
More over, as sem blages dom i nated by spe cies of the ge nus Glomospira (G. charoides, G. gordialis, G. diffundens) oc cur ring un der lower ox y gen a tion also ex isted in dysoxic wa ters dur ing the for ma tion of var ie gated shales es pe cially in the Early Paleocene and Early Eocene (Fig. 5A). This bi otic ep i sode oc - curs across most of the Pol ish Outer Carpathians. The last pe - riod was also doc u mented in the sur face wa ters by the radiolarian bloom in the Skole Zone (B¹k et al., 1997). The infauna with coarse-grained tests ce mented by si li ceous (Karre - rulina, Gerochammina) and cal car e ous ma te rial (Remesella) also ex isted in more de tri tal sed i ment close to the CCD un der pro gres sive ox y gen a tion, which was in duced by an in creased ac tiv ity of bot tom cur rents. In ad di tion, deep infaunal forms of the ge nus Bolivinopsis, re flect ing cool, tur bid and poorly ox y gen ated bot tom wa ters in clud ing pe lagic sub strates with high or ganic mat ter con tent (Kaminski, 1984), also oc cur in var ie gated shales.
The Paleocene-Eocene shales also con tain spec i mens of shal - low (Recurvoides) and mo bile infauna (Haplophragmoides) which, along with spe cies of Bolivinopsis and Ammodiscus, of ten oc cur in eutrophic as sem blages sensu Haig (1979). This trend is es pe cially char ac ter is tic for the lower/mid dle part of the Eocene (Kaminski, 2005). Usu ally op por tu nis tic ben thic taxa (Glomo - spira, Caudammina, Recurvoides, Haplophragmoides) which were re garded as forms of the flysch-type by Gradstein and Berggren (1981) highly con trib ute to the foraminiferal as sem - blages from hab i tats that ex pe ri ence pe ri odic an oxia (Kaminski et al., 1995; Figs. 1 and 4).This phe nom e non was also ob served in the sur face wa ters, as doc u mented by dwarfed forms of the Globigerina group and Chiloguembelina and Guembelitria taxa (Figs. 1, 4 and 5). This plank ton tol er ates nu tri ent-rich and anoxic wa ters that were partly in fil trated by green house gases and toxic com pounds trans ported from the bot tom wa ter dur ing in tense upwelling in the Paleocene. Es pe cially most of ben thic and planktic forms were elim i nated just af ter the KTBE event in the ear li est Paleocene (Keller and Benjamini, 1991; Keller and Pardo, 2004). At that time, per tur ba tion in sea level and wa ter cir - cu la tion led to the ex ten sion of an oxia and acid i fi ca tion in parts of the ba sin. The for ma tion of iron com pounds (siderites) and phos - phates in ten si fied the pro cess as so ci ated with in tense con sump - tion of ox y gen, which led to the mass ex tinc tions and may con - firm the in flu ence of sub ma rine vol ca nism (Berner, 1984; Keller, 1989; Tucker, 1991). The con di tions shaped by di a strophic and hy dro ther mal pro cesses were also ob served dur ing the Paleo - cene-Eocene (Oszczypko, 2004; Waœkowska et al., 2014;
Janko wski, 2015). Re placed cal car e ous planktic and ben thic foraminifera and phytoplankton (red al gae) de scribed by the au - thors and Leszczyñski et al. (2012) in the Silesian se ries (Istebna shales) re flect ma jor rel a tive sea level changes in the Late Paleocene. This pro cess in flu enced the wa ter cir cu la tion and ox - y gen avail abil ity. Planktic mas sive and or na mented spe cies of Morozovella and Acarinina were elim i nated, while mono-spe cies as sem blages with semi-infaunal forms of Glomospira charoides and G. gordialis dom i nated un der eutrophic con di tions (Figs. 1 and 4). Dur ing ex tend ing the pe ri ods of ox y gen de fi ciency
(hypoxia), planktic com mu ni ties were dom i nated by radio lar ians in the Early and Mid dle Eocene (B¹k et al., 1997). These bi otic events may cor re late with upwelling and pe ri odic cool ing. Un der these con di tions, early diagenesis (phos phates) took place in strat i fied wa ters un der the in flu ence of vol ca nic flu ids and gases.
It was as so ci ated with ox y gen and cal cium con sump tion. Af ter this ther mal min i mum, epifaunal forms of the ge nus Rethiculo - phragmium be came nu mer ous and oc curred in ho mo ge neous eutrophic as sem blages in the Mid dle and Late Eocene (Fig. 4).
The pe ri ods of an oxia as so ci ated with a de crease in sed i men ta - tion rate and cool ing ef fect at the be gin ning of the Paleocene and the Eocene (PETM, EEOC) were in ter rupted by in tense sup plies of coarse-grained ma te rial. Ini tially, this pro cess led to short-term ox y gen a tion dur ing the for ma tion of sand stone bod ies in the Subsilesian, Silesian, and Dukla zones (Fig. 3). Dysoxic con di - tions spread grad u ally into the in ter nal and ex ter nal zones of the Outer Carpathian Ba sin (Hi ero glyphic and Magura sand stones) dur ing the Eocene (Fig. 3). It seems that deep and shal low infauna (Bolivinopsis, Recurvoides, Haplo phragmoides, Glomo - spira), usu ally ex ist ing in dark shales un der low ox y gen a tion con - di tions, sur vived pe ri ods of deoxygenation dur ing the for ma tion of var ie gated shales in the early part of the Paleogene. The in ten - sity of this trend is also ev i denced by oligotrophic as so ci a tions with Nuttalides truempyi in the Late Paleocene (Figs. 1 and 4).
More over, as sem blages with thick, coarsely ag glu ti nated spe - cies of Saccamminoides re flect pe ri ods of sup ply of coarse grained ma te rial in the Early Eocene. It has been found in pe lagic and hemipelagic sed i ments of nu tri ent-rich en vi ron ments close to or be low the CCD (Waœkowska, 2008, 2014a). In the Early/Mid dle and Late Eocene, ben thic en vi ron ments were in - hab ited by as sem blages dom i nated by shal low infaunal spe cies of Reticulophragmium, which be came more di verse at the end of these pe ri ods. This micro fauna, ac com pa nied by Nothia excelsa and Ammolagena clavata, is found in var ie gated and green shales which formed in ter ca la tions within the Hi ero glyphic sand - stones, and in thick com plexes in most parts of the Pol ish Outer Carpathians (Jurkiewicz, 1967; Waœkowska, 2014a, b, 2015). In the Late Eocene, radio lar ians of var ie gated shales de crease in num ber (Barwicz-Piskorz and Rajchel, 2012).
Cli mate changes were ini ti ated dur ing the for ma tion of the Globigerina Marls at the Eocene/Oligocene bound ary. It was as so ci ated with a palaeogeographic re or ga ni za tion and chan - ges in ocean cir cu la tion (TTE), which re sulted in the re ac ti va - tion of vol ca nism, sea level fluc tu a tions and a lim ited deep-wa - ter cir cu la tion. Un der these con di tions, forms char ac ter is tic for eutrophic con di tions (Globanomalina and Chiloguembelina) oc - curred at this bound ary. Af ter this ep i sode, a cool ing trend in - ten si fied in the Early Oligocene. The Menilite Shales in clude si - li ceous nod ules (cherts) con tain ing poorly di ver si fied as sem - blages with cal car e ous ben thic forms that re flect shelf en vi ron - ments (Olszewska, 1984). The re place ment of the orig i nal fos sil ma te rial by py rite is char ac ter is tic for this as sem blage. Spe cies be long ing to the ge nus Bolivina pre fer a shal low, infaunal microhabitat, and dom i nate in un sta ble sed i men tary en vi ron - ments rich in or ganic mat ter. The other deep and in ter me di ate infauna of the gen era Chilostomella, Nonionella, Globobulimina and Uvigerina in di cate ox y gen de fi ciency in the bot tom wa ter (Boersma, 1986; Corliss and Chen, 1988; Kaiho, 1994;
Jorissen et al., 1995; Pérez et al., 2001; Hess and Jorissen, 2009). These infaunal and epifaunal forms (Cibicides) with unornamented and smooth tests of ten oc curred in ho mo ge - neous eutrophic as sem blages (Jorissen et al., 1995; Van der Zwaan et al., 1999; Fontanier et al., 2007). The scar city or lack of benthos and the dom i nance of si li ceous and or ganic phyto - plankton may re flect pe ri odic de creases in sa lin ity. In lim ited parts of the ba sin the in flux of land-de rived or ganic mat ter and
river wa ters cre ated low-sa lin ity sur face zones col o nized by brown al gae, cyanobacteria (Zn, Cu, dinor-hopanes) and di a - toms (V, isoprenoids) dur ing the Oligocene cool ing (ten Ha ven et al., 1993; Köster et al., 1998; Fig. 5B). Sim i larly to the pre vi - ous ep i sodes, pe ri ods of an oxia and acid i fi ca tion were in ter - rupted by di a strophic pro cesses that led to the re ac ti va tion of wa ter cir cu la tion and deoxygenation by an in tense sup ply of terrigenous ma te rial (Krosno sand stones). Ini tially, this pro cess af fected sur face wa ter while the sea-floor con di tions were still re stric tive. The Krosno Beds con tain pyritized tests of op por tu - nis tic plank ton and epifaunal benthos that oc cur in the shaly in - ter ca la tions of the Krosno sand stones. More over, rep re sen ta - tives of stressed en vi ron ments (Globigerina, Cassigerinella, Chiloguembelina and Globanomalina), be long ing to the sur - face-dwell ing group and typ i cal of cooler wa ter con di tions dur - ing the Early Oligocene, were re placed by thermophile fora - miniferal plank ton that re flect the short-term warm ing at the end of the Paleogene (Olszewska, 1984; Spezzaferri and Premoli Silva, 1991; Spezzaferri and Spiegler, 2005; Olszewska and Malata, 2006).
DISCUSSION
Ox y gen de fi ciency and acid i fi ca tion, con trolled by di a - strophic and hy dro ther mal pro cesses, af fected the ben thic and planktic biota dur ing the Paleogene. The stud ied micro - fauna tol er ates siliciclastic in flux caused by dras tic sea level changes dur ing pe ri odic ma rine floodings. Un der con di tions of hu mid warm (Paleocene-Eocene) or cold (Oligocene) cli - mate, in tense con ti nen tal run off led to pro gres sive acid i fi ca - tion and hypoxia of strat i fied wa ters in which sparse, poorly di ver si fied foraminiferal as sem blages were dom i nated by epifauna (Nagy et al., 2009) and some infauna. These de tri - tus and ac tive de posit feed ers re late to the flysch as sem - blages with Rzehakina and Glomo spira -Ammodiscus (Bio - facies B) and Recurvoides as sem bla ges oc cur ring un der eutrophic con di tions (Haig, 1979; Kaminski et al., 1999) (Figs. 1, 4 and 5). The spe cies that tol er ate chang ing ox y gen con di tions also oc cur in var ie gated shales. Un der con di tions of re duced clastic sup ply, the gen era Nothia and Ammo - lagena pro lif er ated. They are char ac ter is tic for more ox y gen - ated bot tom en vi ron ments close to the CCD (Kaminski and Geroch, 1992; Alve et al., 2011; Waœkowska, 2014b). Fre - quent sup plies of coarse-grained terrigenous ma te rial con - trolled by tur bid ity cur rents con trib uted to the re newal of bot - tom wa ters in which op por tu nis tic forms were re placed by oligotrophic taxa. These con di tions dras ti cally changed in the Late Paleocene and Early Oligocene. It was as so ci ated with the re or ga ni za tion of the ba sin and rel a tive sea level fluc tu a - tions in duced by di a strophic and geodynamic pro cesses.
These pro cesses are doc u mented by cal car e ous planktic and ben thic forms, some with pyritized tests. Changes in the plank ton pop u la tions were clo sely as so ci ated with in tense upwelling and acid i fi ca tion. This pro cess was closely as so ci - ated with hy dro ther mal and diage netic pro cesses and bi otic de com po si tion of ma rine and land -driven plant or ganic mat - ter, as ev i denced by hy dro car bon biomarkers (Lange et al., 2000). In strat i fied nu tri ent-rich wa ters in fil trated by prod ucts of hy dro ther mal and dia genetic pro cesses (gases and liq - uids), ex tended an oxia led to the grad ual elim i na tion of the biota in clud ing benthos (fora minifera, bi valves), nekton (fish) and plank ton (brown al gae, cyano bacte ria, di a toms). These anoxic con di tions oc curred in a semi-iso lated sea in hab ited
by en demic biota (Olszewska, 1984; Kotlarczyk and Uch - man, 2012; Studencka et al., 2016; Fig. 5B).
The sup plies of or ganic car bon, iron, phos pho rus and sul - phur fa voured the for ma tion of siderites, phos phates and sil ica.
This pro cess was as so ci ated with in tense ox y gen and cal cium con sump tion and con trib uted to an oxia and acid i fi ca tion. These phe nom ena co in cided with both the bloom of si li ceous phytoplankton (radio lar ians and di a toms) and per tur ba tions in cal car e ous zoo plank ton (foraminifers). Radio lar ians were dis - persed by tur bid ity cur rents in the Paleocene and ac cu mu lated by sus pen sion in the Early Eocene, while di a toms be came nu - mer ous dur ing the hemipelagic de po si tion in the Late Paleo - cene and Early Oligocene. These bi otic events re flect ing eutro - phic con di tions usu ally co in cided with a de crease in the size and di ver sity of op por tu nis tic planktic foraminifera.
CONCLUSIONS
With re spect to the geo chem i cal in dex the Paleogene fora - minifera re flect en vi ron men tal per tur ba tions in the var i ous sta - ges due to the na ture of depositional set tings and palaeo - geographic po si tion of the stud ied ba sin. In this area, lo cated in the north ern Tethys, hab i tats were closely con trolled by a tur - bid ity sys tem stim u lated by di a strophic and geodynamic pro - cesses. These fac tors in flu enced the struc ture, evo lu tion and dis tri bu tion of biotopes, and diagenetic and fos sil iza tion pro - cesses. Microfossils, es pe cially cal car e ous forms are poorly pre served or min er al ized un der un fa vour able con di tions. Ac cu - mu la tion of or ganic mat ter was a con se quence of stag nant bot - tom wa ter con di tions in the ba sin. Its de com po si tion, in ten si fied by hy dro ther mal and diagenetic pro cesses, lead to pe ri odic an - oxia and acid i fi ca tion in the wa ters strat i fied due to tem per a ture and den sity dif fer ences.
Stress as so ci ated with rap idly chang ing ox y gen con di tions in duced by sed i men tary pro cesses and upwelling re sulted in the dom i nance of op por tu nis tic benthos and plank ton. At that time, ag glu ti nated and some cal car e ous forms were lim ited to eutrophic as sem blages dom i nated by in di vid ual spe cies rep re - sent ing surficial epifauna and semi-infauna (Glomospira, Ammo discus, Recurvoides and Rzehakina) and planktic shal - low-ma rine dwell ers (Guembelitria, Chiloguembelina, Globano - malina, Globigerina, Cassigerinella and Catapsydrax), or they were re placed by phytoplankton (cyanobacteria, al gae, radio - lar ians and di a toms). The re sults dis cussed with re spect to geo - chem i cal data con firm the im pact of en vi ron men tal stress on the ma rine life in the Paleogene ba sin and its re la tion ship with global events (KTBE, PTME, EEOC and TTE). Pe ri ods of abrupt changes in tem per a ture, ox y gen con tent, and wa ter cir - cu la tion that re sulted in the for ma tion of sid er ite, phos phates and sil ica oc curred oc ca sion ally un der con di tions of warm and hu mid cli mate dur ing the Paleocene-Eocene. Si li ceous min er - als and hy dro car bon com pounds be came dom i nant dur ing the Oligocene cool ing, which was in ter rupted by warm ing ep i sodes at the end of this in ter val.
Ac knowl edge ments. We thank M. Kaminski and other anon y mous re view ers for their con struc tive com ments on the manu script. We are grate ful to L. Jankowski, R. Kopciowski, T. Malata, P. Nescieruk (Carpathian Branch of the Pol ish Geo - log i cal In sti tute – Na tional Re search In sti tute) and P. Strze boñski (AGH Uni ver sity of Sci ence and Tech nol ogy) for their help dur ing field work and col lec tion of some sam ples. The re search was fi - nan cially sup ported by the PGI-NRI stat u tory funds.
692 Barbara Olszewska and Andrzej Szyd³o
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