Benthic foraminiferal morphogroups from the Paleocene of the coastal part of East Stara Planina Mts.

GEOLOGICA BALCANICA, 35, 3 4, Sofia, Dec. 2006, p. 41 48. Benthic foraminiferal morphogroups from the Paleocene of the coastal part of East Stara Planina Mts. Boris Valchev University of Mining and Geology St. Ivan Rilski, 1700 Sofia, e-mail: b_valchev@mgu.bg (Submitted: 13.10.2006; accepted for publication: 18.12.2006) Á. Âúë åâ Áåíòîñíûå ôîðàìèíèôåðîâûå ìîðôîãðóïïû Ïàëåîöåíîâîé ñåðèè ïðèìîðñêîé àñòè Âîñòî íîé Ñòàðîé ïëàíèíû. Äâåíàäöàòü ìîðôîãðóïï âûäåëåííû â ðåçóëüòàòå èññëåäîâàíèÿ áåíòîñíûõ ôîðàìèíèôåðîâûõ àñîöèàöèé Ïàëåîöåíîâîé ñåðèè ïðèìîðñêîé àñòè Âîñòî íîé Ñòàðîé ïëàíèíû. Îíè äåôèíèðîâàíû íà îñíîâàíèè ôîðìû ðàêîâèíû è ñïîñîáà íàâèâàíèÿ. Ìîðôîãðóïïû áûâàþò: îêðóãëåííàÿ ñïèðàëüíî-êîíè åñêàÿ, ïëîñêî-âûïóêëàÿ ñïèðàëüíî-êîíè åñêàÿ, äâóÿêîâûïóêëàÿ ñïèðàëüíî-êîíè åñêàÿ, ìèëèîëèäîîáðàçíàÿ, îêðóãëåííàÿ ñïèðàëüíî-ïëîñêîñòíàÿ, ëèíçîâèäíàÿ, ñïëîùåííàÿ îâîèäíàÿ, çàîñòðëííàÿ è öèëèíäðè åñêàÿ, øàðîâèäíàÿ, ñïëîùåííàÿ çàîñòðëííàÿ, òðóá àòàÿ, íåïðàâèëüíî çàâèòàÿ è õåòåðîìîðôíàÿ. Îïèñàííûå ðàíøå Áåëåíñêèå è Ôëèøåâèå àñîöèàöèè îòëè àþòñÿ äîìèíèðóþùåé ìîðôîëîãèåé ðàêîâèíû. Â Áåëåíñêîì òèïå àñîöèàöèè íå íàáëþäååòñÿ ñòðîãî äîìèíèðóþùàÿ ìîðôîãðóïïà, ïîêà Ôëèøêèé òèï àñîöèàöèè ëòêî äîìèíèðîâàíû äâóõ ìîðôîãðóïï. Äâà òèïà àñîöèàöèé äîìèíèðîâàííû ìîðôîãðóïàìè, õàðàêòåðíûå äëÿ ãëóáîêîâîäíûå óñëîâèÿ. Abstract. Twelve morphogroups were defined on the basis of test shape and nature of test coiling as a result of the investigation of the Paleocene benthic foraminifera from the coastal part of East Stara Planina. The morphogroups are rounded trochospiral (RT), plano-convex trochospiral (PT), biconvex trochospiral (BT), milioline (M), rounded planispiral (RP), lenticular (L), flattened ovoid (FO), tapered and cylindrical (T/C), spherical (S), flattened tapered (FT), tubeshaped (T), streptospiral and heteromorphous (S/H). The previously described Byala-type and Flysh-type assemblages differ from each other by the predominant test morphology. There is no strongly dominating morphogroup in the Byala-type, while the Flysh-type is strongly dominated by two morphogroups. Both Byala-type and Flysh-type are dominated by morphogroups typical for deep sea conditions. Valchev, B. 2006. Benthic foraminiferal morphogroups from the Paleocene of the coastal part of East Stara Planina Mts. Geologica Balc., 35, 3 4; 41 48. Key words: benthic foraminifera, morphogroups, Paleocene, East Stara Planina. Introduction During the last four decades of the 20 th century benthic foraminifers have turned into one of the most useful fossil groups for interpretation of ancient marine environment. There are a lot of publications numerous articles and several monographs (see Boltovskoy et al., 1991; Murray, 1991) concerning the relations between morphological variation in benthic foraminiferal test and environmental parameters. The majority of these 5 Geologica Balcanica, 3 4/2006 studies recorded mainly the depth influence, while parameters like temperature, salinity, oxygen levels, carbonate dissolution, substrate, nutrition, dissolved oxygen, illumination, pollution, were less intensively investigated (Boltovskoy et al., 1991). It is widely known that benthic foraminifera exhibit a great variety of test shapes and modes of coiling and the main goal of some studies from the last three decades was to elucidate if the benthic foraminiferal morphotypes vary with water depth changes (Cham- 41

ney, 1976; Severin, 1983; Corliss, 1985; Jones, Charnock, 1985; Bernhard, 1986; Corliss, Chen, 1988). Severin (1983) described six morphogroups from Texas coastal plain. He noted that elongate-flattened, biconvex-keeled, and tapered forms show an increase in their relative abundance with increasing water depth, while the plano-convex morphogroup abundance decrease from shallow to deep water. The straight-cylindrical forms are most abundant in bays, and the rounded planispiral group does not show any trend with depth increase. Corliss (1985) published a study on living forms revealing that test morphology is related to microhabitats. Corliss, Chen (1988) provided data about depth distribution of nine benthic morphogroups from Norwegian Sea. Tapered/cylindrical morphogroup has bathymetric range 0 2500 m, as it is abundant in the upper 1000 m. Flattened tapered shapes are low abundant and they occurre in the upper 500 m. Rounded planispiral tests show depth distribution between 20 and 3000 m, but their maximum abundance is in the interval 500 1000 m. As a whole spherical morphotype is low abundant and it was found in depths 200 1600 m. Flattened ovoid forms are widely distributed (50 3200 m), with maximum percent abundance between 700 and 1500 m. Planoconvex trochospiral morphogroup occurres between 0 and 4000 m, but it shows two peaks of abundance between 200 and 500 m, and in the interval 1500 2500 m. Biconvex trochospiral morphogroup was recorded in depths from 0 to 4000 m, with maximum abundance between 1500 and 4000 m. Milioline forms show gradual increase from 100 to 3200 m, but as a whole they are low abundant. Rounded trochospiral morphogroup ranges from 0 to 4000 m, but with low abundance presence in the whole depth interval. In Bulgaria benthic foraminifers have been used for taxonomical and biostratigraphical purposes only (see Valchev, 2003b). Therefore the present article aims to do the first step to an overall paleoecological reconstruction investigating the test morphology, dividing morphogroups amongst the Paleocene assemblages from the coastal part of East Stara Planina and providing bathymetrical interpretation. This area is of great interest for Bulgarian stratigraphy, because here Òðèôîíîâà (1960) first proved the presence of Paleocene sediments in Bulgaria. The location of the studied sections and discussion about the biostratigraphical framework were given by Valchev (2003c). Description of the morphogroups The foraminiferal tests are classified herewith into morphological groups (morphogroups or morphotypes) on the basis of (1) test shape and (2) the nature of test coiling (i. e. chamber addition). The investigation of the foraminiferal test morphology from the studied area allowed me to define 12 morphogroups (see Appendix): 1) Rounded trochospiral morphogroup (RT) includes tests with trochospiral mode of coiling and broadly rounded periphery (Plate I, Figs. 1-5). 2) Plano-convex trochospiral morphogroup (PT) is represented by trochospiral tests with flat spiral side and narrowly rounded to sharp periphery (Plate I, Figs. 6-11). 3) Biconvex trochospiral morphogroup (BT) includes tests with trochospiral mode of coiling and biconvex morphology, characterized by sharply angled to narrowly rounded periphery (Plate I, Figs. 12-17). 4) Milioline morphogroup (M) is flattened with elliptical outline resembling milioline chamber arrangement (Plate II, Fig. 1). 5) Rounded planispiral morphogroup (RP) includes compact tests with planispirally arranged chambers and broadly rounded periphery (Plate II, Figs. 2-4). 6) Lenticular morphogroup (L) has biconvex morphology with sharply angled or keeled periphery (Plate II, Figs. 5, 6). 7) Flattened ovoid morphogroup (FO) includes single-chambered hyaline forms with ovoid outline and keeled periphery (Plate II, Fig. 7). 8) Tapered and cylindrical morphogroup (T/C) is represented by forms with round, oval or triangular cross section, with parallel or subparallel sides (Plate II, Figs. 8-13). Rectilinear and straight uniserial, biserial and triserial tests are included in this morphogroup. 9) Spherical morphogroup (S) includes unilocular and inflated planispiral or trochospiral multilocular tests (Plate II, Figs. 14-18). 10) Flattened tapered morphogroup (FT) is ovate to compressed in cross section, with parallel to subparallel sides (Plate III, Figs. 1-6). This group includes uniserial, biserial and palmate tests. 11) Tube-shaped morphogroup (T) has simple morphology straight or curved single tubes, flattened or with round cross section, are included in the morphogroup (Plate III, Figs. 7-9). All of them are with agglutinated wall. 12) Streptospiral and heteromorphous morphogroup (S/H) includes mainly agglutinated forms with irregular coiling or showing two or more types of chamber arrangement (Plate III, Figs. 10-13). For evaluation of the paleoecological importance of the morphogroups they are going to be compared to modern ones from Norwegian Sea and Texas coastal plain. Results Paleocene benthic foraminiferal assemblages from the studied area have already been divided into two types Byala-type and Flysh-type (Valchev, 2003a, 2004) differing from each other by their taxonomical composition and structure. Here the morphological varieties in the two types of assemblages are going to be described separately. 42

Fig. 1. Morphogroup maximum abundance in the Byala-type assemblages Byala-type assemblages All 12 morphogroups are present in this type (Fig. 1). As could be seen there is no strongly dominating morphogroup. The most numerous is the group of tapered and cylindrical tests (T/C morphogroup) which shows almost uniform maximum percent distribution in the whole Paleocene section. Its maximum relative abundance is in P1c (up to 43.5%), P4 (up to 42.8%), and P2 Zone (up to 42.7%). It is due to the presence of the main contributors to Byalatype: Bulimina trinitatensis Cushman & Jarvis, Bannerella retusa (Cushman), Marssonella indentata Cushman & Jarvis, M. oxycona (Reuss), Clavulinoides asperus (Cushman), C. trilaterus (Cushman), Pseudoclavulina globulifera (ten Dam & Sigal), Nodosaria limbata d Orbigny, Pyramidulina velascoensis (Cushman), Gaudryina pyramidata Cushman, Pseudonodosaria manifesta (Reuss). Another five morphogroups are amongst the dominating types. Biconvex trochospiral (BT) tests reach their maximum abundance in P1c (up to 47.2%) and P1b Zone (up to 38.2%). Their main representatives are Nuttalides trumpyi (Nuttal), Oridorsalis megastomus (Grzibowski), Osangularia velacoensis (Cushman), Oridorsalis lotus (Schwager), Anomalinoides acutus (Plummer), A. danicus (Brotzen). Tube-shaped (T) specimens represented by Bathysiphon discreta (Brady) and Rhizammina indivisa Brady, dominate in P1b Zone (up to 38.4%). Rounded trochospiral morphotype (RT) reach its relative maximum in P5 Zone (up to 20.9%) due to Gavelinella beccariiformis (White) occurrence, while the plano-convex trochospiral tests (PT) are well presented in P4 Zone (up to 28.5%). They include species like Heterolepa grimsdalei (Nuttal), H. perlucida (Nuttal), Cibicidoides dayi (White), Gyroidinoides girardanus (Reuss), G. globosus (Hagenow). Spherical morphotype (S) are amongst the dominating groups in P1b (up to 25.0%) and P5 Zone (up to 20.5%). They are represented by S. placenta (Grzybowski) and Reussoolina apiculata (Reuss). The other six morphogroups are subsidiary elements of the assemblage composition and they show some fluctuations in their percent abundance. Amongst them rounded planispiral (RP), streptospiral and heteromorphous (S/H), flattened tapered (FT) and lenticular (L) morphogroups are relatively abundant. It is due to the species Cribrostomoides trinitatensis Cushman & Jarvis (RP), Repmanina charoides (Jones & Parker) (S/H), Aragonia velascoensis (Cushman), Spiroplectinella dentata (Alth), Astacolus gladius (Philippi) (FT), Lenticulina pseudomamilligera (Plummer), L. inornata (d Orbigny) (L), which are amongst the main contributors to Byala-type. Flattened ovoid morphogroup (FO) is not of importance while the milioline one (M) is present by single specimens in P4 Zone only. 43

PLATE I Rounded trochospiral morphogroup (PT): 1, 2 Quadrimorphina allomorphinoides (Reuss), Byala Formation, Koundilaki Cheshme Valley, Paleocene, Sample Ê -1, 1 spiral view, 2 umbilical view, SEMx110. 3 5 Gavelinella beccariiformis (White), Byala Formation, Byala River Valley, Paleocene, Sample ÁÐ-7, 3 umbilical view, 4 spiral view; SEMx85; 5 apertural view, SEMx60. Plano-convex trochospiral morphogroup (PT): 6 8 Gyroidinoides girardanus (Reuss), Byala Formation, Borehole Ñ-28, 15.00 m, Middle Paleocene, P2 Zone, Sample Ñ-28-1, 6 umbilical view, 7 apertural view SEMx42.6, 8 Byala River Valley, Paleocene, Sample ÁÐ-6; spiral view, SEMx48.6. 9 11 Cibicidoides dayi (White), Byala Formation, Section Byala 2b, Lower Paleocene, NP3 Zone, Sample Á2b-17, 9 spiral view; 10 umbilical view, SEMx57, 11 Byala River Valley, Paleocene, Sample ÁÐ-6, apertural view, SEMx48.6. Biconvex trochospiral morphogroup (BT): 12 14Oridorsalis megastomus (Grzibowski), Byala Formation, Borehole Ñ-30, 107.90 m, Upper Paleocene, P5 Zone, Sample Ñ- 30-19, 12 umbilical view, 13 spiral view, SEMx75, 14 Byala River Valley, Paleocene, Sample ÁÐ-6, apertural view, SEMx110. 15 17 Rotalia hermi Hillebrandt, 1962, Byala Formation, Byala River Valley, Paleocene, Sample ÁÐ-6, 15 umbilical view, 16 spiral view; SEMx75; 17 apertural view; SEMx110. PLATE II Milioline morphogroup (M): 1 Rzehakina epigona (Rzehak), Emine Formation, Section Kochan, Middle Paleocene, P3 Zone, Sample Å-Ê-7, SEMx50.5. Rounded planispiral morphogroup (RP): 2 Ammodiscus glabratus Cushman & Jarvis, Byala Formation, Borehole Ñ-30, 86.30 m, Upper Paleocene, P4 Zone, Sample Ñ-30-8, SEMx37.4. 3 Pullenia quinqueloba (Reuss), Byala Formation, Borehole Ñ-30, 86.30 m, Upper Paleocene, P4 Zone, Sample Ñ-30-8, SEMx65.5. 4 Trochamminoides proteus (Karrer, 1866), Byala Formation, Borehole Ñ-29, 395.20 m, Upper Paleocene, P4 Zone, Sample Ñ-29-7; SEMx37.4. Lenticular morphogroup (L): 5 Lenticulina inornata (d Orbigny, 1846), Byala Formation, Borehole Ñ-28, 16.00 m, Middle Paleocene, P2 Zone, Sample Ñ- 28-2; SEMx156. 6 Lenticulina turbinata (Plummer), Byala Formation, Borehole Ñ-25, 26.40 m, Lower Paleocene, P1b Zone, Sample Ñ-25-3, SEMx178. Flattened ovoid morphogroup (FO): 7 Palliolatella crebra (Mathes), Byala Formation, Borehole Ñ-30, 83.90 m, Upper Paleocene, P4 Zone, Sample Ñ-30-6, SEMx50. Tapered and cylindrical morphogroup (T/C): 8 Dorothia fallax Hagn, Emine Formation, Section Kochan, Middle Paleocene, P3 Zone, Sample Å-Ê-6, SEMx42.6. 9 Gaudryina cretacea (Karrer), Byala Formation, Byala River Valley, Paleocene, Sample ÁÐ-6, SEMx42.6. 10 Clavulinoides trilaterus (Cushman), Byala Formation, Byala River Valley, Paleocene, Sample ÁÐ-6, SEMx60. 11 Dentalina longicostata (Cushman and Jarvis), Byala Formation, Byala River Valley, Paleocene, Sample ÁÐ-6, SEMx48.6. 12 Praeglobobulimina pyrula (d Orbigny, 1846), Byala Formation, Borehole Ñ-29, 440.30 m, Upper Paleocene, P5 Zone, Sample Ñ-29-11; SEMx63. 13 Siphonodosaria adolphina (d Orbigny), Byala Formation, Borehole Ñ-30, 83.90 m, Upper Paleocene, P4 Zone, Sample Ñ- 30-6, SEMx48.6. Spherical morphogroup (S): 14 Psammosphaera sp. 2, Byala Formation, Borehole Ñ-29, 365.90 m, Middle Paleocene, P3 Zone, Sample Ñ-29-5, SEMx40.8. 15 Saccammina placenta (Grzybowski), Emine Formation, Section Kochan, Middle Paleocene, P3 Zone, Sample Å-Ê-9, SEMx46.4. 16 Pygmaeoseistron oxystomum Reuss, Byala Formation, Section Byala 2c, Lower Paleocene, NP1 Zone, Sample Á2ñ-4, SEMx55. 17 Reussoolina globosa (Montagu, 1803), Byala Formation, Section Byala 1, Lower Paleocene, NP3 Zone, Sample Á1-10; SEMx65.5. 18 Pullenia coryelli White, 1928, Byala Formation, Section Byala 1, Lower Paleocene, NP4 Zone, Sample Á1-10; SEMx65.5. 44

PLATE I

PLATE II

PLATE III

PLATE III Flattened tapered morphogroup (FT): 1 Hormosina velascoensis (Cushman, 1926), Emine Formation, Paleocene, Sample Å-1316, SEMx48.6. 2 Spiroplectinella dentata (Alth), Byala Formation, Borehole Ñ-30, 99.50 m, Upper Paleocene, P5 Zone, Sample Ñ-30-14, SEMx40.8. 3 Frondicularia jarvisi Cushman, Byala Formation, Koundilaki Cheshme Valley, Paleocene, Sample Ê -1, SEMx60. 4 Bolivina midwayensis Cushman, 1936, Byala Formation, Section Byala 2b, Lower Paleocene, NP1 Zone, Sample Á2b-7, SEMx50.5. 5 Aragonia velascoensis (Cushman, 1925), Byala Formation, Section Byala 1, Lower Paleocene, NP4 Zone, Sample Á1-12, SEMx71.5. 6 Neoflabellina rugosa (d Orbigny, 1840), Byala Formation, Byala River valley, Paleocene, Sample ÁÐ-7, SEMx143. Tube-shaped morphogroup (T): 7 Bathysiphon discreta (Brady), Byala Formation, Section Byala 2b, Lower Paleocene, NP3 Zone, Sample Á2b-16, SEMx63. 8 Rhizammina indivisa Brady, 1884, Emine Formation, Section Kochan, Lower Paleocene, P1c Zone, Sample Å-Ê-3, SEMx42.6. 9 Kalamopsis grzybowskii (Dylazanka), Byala Formation, Section Byala 2b, Lower Paleocene, NP3 Zone, Sample Á2b-16, SEMx63. Streptospiral and heteromorphous morphogroup (S/H): 10 Glomospira irregularis (Grzybowski), Byala Formation, Borehole Ñ-29, 420.60 m, Upper Paleocene, P4 Zone, Sample Ñ- 29-8, SEMx50.5. 11 Repmanina charoides (Jones&Parker, 1860), Byala Formation, Borehole Ñ-30, 83.90 m, Upper Paleocene, P4 Zone, Sample Ñ-30-6, SEMx50.5; 12 Lituotuba lituiformis Brady, Emine Formation, Section Kochan, Lower Paleocene, P1c Zone, Sample Å-Ê-5, SEMx57.5. 13 Saraceneria hantkeni (Cushman, 1933), Byala Formation, Section Byala 2c, Lower Paleocene, NP1 Zone, Sample Á-2ñ-4, lateral view, SEMx106.

Fig. 2. Morphogroup maximum abundance in the Flysh-type assemblages Flysh-type assemblages These type benthic assemblages are composed of 11 morphogroups (Fig. 2). Two of them dominate strongly the assemblage structure. Tube-shaped forms (T) shows stable occurrence along the whole Paleocene section with exception of NP8 Zone. Their maximum percent abundance is in the Middle Paleocene interval (up to 94.2%) due to Bathysiphon microrhaphidus Samuel mass occurrence. Other important T- forms are Bathysiphon discreta (Brady), Bathysiphon sp., Rhizammina indivisa Brady. Spherical morphotype (S) demonstrates sharp increase from Lower to Upper Paleocene and it reches its maximum percent abundante in NP8 Zone (up to 96.2%). It is due mainly to Saccammina placenta (Grzybowski) mass occurrence in this interval, while the other important S-form Psammosphaera sp. 1 shows almost constant distribution. Another four morphogroups are present along the whole Paleocene section. The most abundant amongst them is flattened tapered morphotype (FT), which shows constant percent occurrence (up to 16.4%) in the Lower-Middle Paleocene and decrease slightly in the Upper Paleocene levels. Hormosina velascoensis (Cushman) and Hyperammina dilatata Grzybowski occur in the whole Paleocene interval, Reophax duplex Grzybowski is present mainly in Middle Paleocene levels, while Astacolus gladius (Philippi) was established only in Lower Paleocene. Biconvex trochospiral (BT) and rounded planispiral (RP) morphotypes show similar distribution. They are well presented in Lower-Middle Paleocene (BT up to 11.2%, RP up to 12.2%) and decrease in Upper Paleocene. Trochammina deformis Grzybowski (Lower-Upper Paleocene) and Oridorsalis megastomus (Grzybowski) (Lower Paleocene) are the main BT forms, while Trochamminoides coronatus (Brady) and Chilostomelloides sp. represents RP morphotype. Streptospiral and heteromorphous forms (S/H) are more abundant in the Middle Paleocene (up to 10.1%). They are present by Paratrochamminoides irregularis White and Glomospira irregularis (Grzybowski). The other five morphogroups occur mainly in the Lower Paleocene and rarely in the Middle Paleocene. Plano-convex trochospiral (PT) and lenticular (L) forms are restricted in the Lower Paleocene, rounded trochospiral (RT) continue in the Middle Paleocene. All three groups show low percent abundance. Tapered and cylindrical morphotype (T/ C) is relatively abundant in the Lower Paleocene (up to 10.0%), but in the Middle-Upper Paleocene it occur as single specimens only. Milioline forms (M) were found only in the Middle Paleocene as single specimens. 45

Discussion As may be seen hereabove the two types of assemblages differ from each other by the predominant test morphology. The Byala-type assemblages are morphologically more diverse (6 dominating groups). The most numerous group (T/C) is abundant in depths above 1000 m (middle bathyal levels) in the modern seas. The next two morphotypes (BT and T) are abundant in deeper levels (middle-lower bathyal to abyssal), but they occur above 1000 m as minor contributors. PT-morphogroup shows high abundance in the upper bathyal (200 500 m), while in the middle bathyal it is not important element. RT and S-morphogroups are not reliable components, because of their low abundance in all bathymetrical levels. Additional evidence could provide some of the subsidiaries RP-morphogroup, which lower limit is 1000 m and FT-morphogroup, which occurres above 500 m (with low abundance). These data let us to conclude that our Byala-type assemblages lived in upper to middle bathyal conditions. The two dominating groups in our Flysh-type assemblages (the T-morphogroup and major part of S- morphogroup) are composed of benthics typical for the Upper Cretaceous-Paleogene Flysh-type (A-type) foraminiferal assemblages of the Tethys region, occurring in depths 700 4000 m (Gradstein, Berggren, 1981; Miller et all, 1982, Berggren, 1984), which corresponds to middle bathyal-abyssal realm. The bathymetrical range of some of the subsidiary elements (FT and RP-morphogroups) in modern environments is relatively broad (from upper shelf to middle bathyal), but with low abundance, therefore they are not reliable contributors. On the other hand, the depth distribution of another two subsidiary groups could give us more precise information. BT-morphotype dominates in depths bellow 1500 m, while S/H-morphotype is composed mainly of Flysh-type (A-type) forms occurring bellow 700 m. All these facts lead us to the conclusion that our Flysh-type assemblages lived in middle-lower bathyal to abyssal conditions. Conclusions As a result of the morphotype analyses of the Paleocene benthic foraminiferal assemblages from the coastal part of East Stara Planina the following conclusions could be made: 1) The previously described Byala-type and Flysh-type assemblages differ from each other by the predominant test morphology. There is no strongly dominating morphogroup in the Byala-type, while the Flysh-type is strongly dominated by two morphogroups. 2) Both Byala-type and Flysh-type are dominated by morphogroups typical for deep sea conditions. The predominant morphotypes in the Byala-type could be referred to upper to middle bathyal environment, while the Flysh-type main contributors limit its bathymetric range within middle-lower bathyal to abyssal conditions. 3) The present investigation confirms that the morphogroup analyses provide us quick and easy approach for paleobathymetrical reconstructions, because of the independence of morphogroups of species level taxonomy, as well as the differences between researchers. APPENDIX: Benthic foraminiferal morphogroups Rounded trochospiral (RT): Recurvoides imperfectus (Hanzlikova) Recurvoides sp. Valvulineria alpina Hillebrandt Allomorphina paleocenica Cushman Quadrimorphina allomorphinoides (Reuss) Q. cretacea (Reuss) Gavelinella beccariiformis (White) Plano-convex trochospiral (PT): Cibicidoides dayi (White) Cibicides megaloperfpratus Said & Kenawy C. simplex Brotzen Heterolepa grimsdalei (Nuttal) H. perlucida (Nuttal) Gyroidinoides girardanus (Reuss) G. globosus (Hagenow) G. octocameratus (Cushman & Hanna) Karreria fallax Rzehak Biconvex trochospiral (BT): Trochammina deformis Grzybowski T. globigeriniformis (Parker and Jones) T. quadriloba (Grzybowski) T. ruthvenmurrayi Cushman and Renz Nuttalides trumpyi (Nuttal) Nuttalides sp. Alabamina midwayensis Brotzen Osangularia florealis (White) O. plummerae Brotzen O. velacoensis (Cushman) Oridorsalis lotus (Schwager) O. megastomus (Grzibowski) O. umbonatus (Reuss) O. whitei (Hillebrandt) Anomalinoides acutus (Plummer) A. danicus (Brotzen) A. praeacutus (Vassilenko) A. welleri (Plummer) Rotalia hermi Hillebrandt Milioline (M): Rzehakina epigona (Rzehak) Rounded planispiral (RP): Ammodiscus cretaceus (Reuss) A. glabratus Cushman & Jarvis A. peruvianus Berry Cribrostomoides trinitatensis Cushman & Jarvis Haplophragmoides kirki Wickended H. porrectus Maslakova H. retroseptus (Grzybowski) 46

H. suborbicularis (Grzybowski) H. walteri (Grzybowski) Trochamminoides coronatus (Brady) T. proteus (Karrer) Budashevaella trinitatensis (Cushman & Renz) Cyclammina sp. 1 Cyclammina sp. 2 Nonion havanenså Cushman & Bermudez Pullenia jarvisi Cushman P. quinqueloba (Reuss) Chilostomelloides sp. Lenticular (L): Lenticulina clypeiformis (d Orbigny) L. cultrata (Montfort) L. degolyeri (Plummer) L. disca (Brotzen) L. inornata (d Orbigny) L. macrodisca (Reuss) L. ovalis (Reuss) L. pseudomamilligera (Plummer) L. turbinata (Plummer) L. velascoensis White L. vortex (Fichtel&Moll) L. wilcoxensis (Cushman&Ponton) Flattened ovoid (FO): Palliolatella crebra (Mathes) P. orbignyana Seguenza Tapered and cylindrical T/C): Hyperammina elongata Brady Reophax pilulifer Brady Gaudryina aissana ten Dam & Sigal G. cretacea (Karrer) G. pyramidata Cushman Arenobulimina dorbignyi (Reuss) Remesella varians (Glaessner) Bannerella retusa (Cushman) Dorothia beloides Hillebrandt D. cubensis Cushman & Bermudez D. fallax Hagn D. pupa (Gümbel) Marssonella indentata Cushman & Jarvis M. oxycona (Reuss) Karreriella conversa (Grzybowski) K. horida Mjatliuk Bigenerina sp.? Textularia plummerae Lalicker Textularia sp. Clavulinoides amorphus (Cushman) C. asperus(cushman)? C. paleocenicus (Tjalsma & Lohman) C. trilaterus(cushman) Clavulinoides sp. Pseudoclavulina globulifera (ten Dam & Sigal) Dentalina acuta d Orbigny D. alternata (Jones) D. longicostata (Cushman and Jarvis) Dentalinoides approximata (Reuss) D. colei (Cushman&Dusenbery) D. fallax (Franke) Grigelis pyrula longicostata Cushman Laevidentalina communis (d Orbigny) L. eocenica (Cushman) L. glaessneri (Ten Dam) L. laticolis (Grzybowski) L. megalopolitana (Reuss) L. mucronata Neugeboren Nodosaria aspera Reuss N. concinna Reuss N. ewaldi Reuss N. guttifera (d Orbigny)? N. hispida (Soldani) N. limbata d Orbigny N. longiscata d Orbigny N. praegnans (Reuss) N. radicula (Linne) N. soluta (Reuss) Pseudonodosaria caudigera (Schwager) P. cylindracea (Reuss) P. manifesta (Reuss) P. parallela (Marson) Pyramidulina latejugata (Gümbel) P. raphanistrum (Linné) P. raphanus (Linné) P. tenuicostata (Cushman and Bermudez) P. tutkowskii (Kaptarenko) P. velascoensis (Cushman) Marginulinopsis jacksonensis (Cushman & Applin) Hemirobulina pediformis (Bornemann) Marginulina apiculata Reuss M. hamulus Chapman M. hirsuta d Orbigny M. obliqua (d Orbigny) M. oblonga Kaptarenko M. similis d Orbigny Marginulina sp. Vaginulinopsis earlandi (Plummer) V. longiformis (Plummer) V. midwayana (Fox & Ross) V. pedum (d Orbigny) Guttulina communis d Orbigny G. lidiae Vassilenko Pyrulinoides cylindroides (Roemer) Glandulina laevigata d Orbigny Bulimina midwayensis Cushman & Parker B. paleocenica Brotzen Bulimina trinitatensis Cushman & Jarvis Globobulimina suteri (Cushman & Renz) Praeglobobulimina pyrula (d Orbigny) Quadratobuliminella beaumonti (Cushman & Renz) Fursenkoina sp. Ellipsoglandulina chilostoma (Rzehak) E. manifesta Franke Ellipsopolymorphina velascoensis (Cushman) Nodosarella hedbergi Cushman & Renz N. cf. paleocenica Cushman & Todd N. tuberosa (Gumbel) Nodosarella sp. Pleurostomella eocaena Gumbel P. kugleri Cushman & Renz P. paleocenica Cushman P. subnodosa (Guppy) Nodogenerina emaciata (Reuss) Orthomorphina rohri (Cushman & Stralnforth) Siphonodosaria adolphina (d Orbigny) S. paleocenica (Cushman & Todd) Siphonodosaria sp. Allomorphina conica Cushmsn and Todd Spherical (S): Psammosphaera sp. 1 Psammosphaera sp. 2 Saccammina complanata (Franke) S. placenta (Grzybowski) Hyalinonetrion clavatum (d Orbigny) Lagena costata (Williamson) L. sulcata (Walker & Jakob) L. sulcata apiculata Cushman Pygmaeoseistron hispidum (Reuss) P. laevis (Montagu) P. oxystomum Reuss Reussoolina apiculata (Reuss) R. emaciata (Reuss) R. globosa (Montagu) Globulina gibba d Orbigny Guttulina ipatovcevi Vassilenko G. irregularis (d Orbigny) Ramulina globulifera Brady 47

Favulina hexagona (Williamson) Ållipsoidina ellipsoidås ellipsoidås Seguenza Å. ellipsoidås oblonga Seguenza Pullenia coryelli White Flattened tapered (FT): Hyperammina dilatata Grzybowski Reophax duplex Grzybowski Reophax splendidus Grzybowski Subreophax pseudoscalara (Samuel) Subreophax scalaria (Grzybowski) Hormosina ovuloides (Grzybowski) H. ovulum ovulum (Grzybowski) H. velascoensis (Cushman) Spiroplectammina excolata (Cushman) S. spectabilis (Grzybowski) Spiroplectinella dentata (Alth) Vulvulina mexicana Nuttal Frondicularia jarvisi Cushman Frondicularia sp. 1 Frondicularia sp. 2 Neoflabellina jarvisi (Cushman) N. reticulata (Reuss) N. rugosa (d Orbigny) N. semireticulata (Cushman & Jarvis) Astacolus cymboides (d Orbigny) A. gibbus (d Orbigny) A. gladius (Philippi) Bolivina midwayensis Cushman Bolivinoides delicatulus Cushman Aragonia velascoensis (Cushman) Tube-shaped (T): Bathysiphon discreta (Brady) B. microrhaphidus Samuel Bathysiphon sp. Rhizammina indivisa Brady Dendrophrya excelsa Grzybowski Hyperammyna subnodosiformis Grzybowski Kalamopsis grzybowskii (Dylazanka) Streptospiral and heteromorphous (S/H): Glomospira gordialis (Jones & Parker) G. irregularis (Grzybowski) Glomospirella diffundens (Cushman & Renz) G. gorayskii (Grzybowski) G. serpens (Grzybowski) Repmanina charoides (Jones & Parker) Lituotuba lituiformis Brady Paratrochamminoides irregularis White Trochamminoides dubius (Grzybowski) Ammobaculites sp. Ammosphaeroidina pseudopauciloculata (Mjatliuk) Saracenaria arcuata (d Orbigny) S. hantkeni Cushman References Berggren, W. A., 1984. Cenozoic Deep Water Benthic Foraminifera: a review of major developments since Benthonics 75. In: Oertli, H. J., (ed.), Benthos 83, Second International Symposium on Benthic Foraminifera (Pau, 1983), 41 43. Bernhard, J, M. 1986. Characteristic assemblages and morphologies of benthic foraminifera from anoxic, organic-rich deposits: Jurassic to Holocene. J. For. Res., 16, 207 215. Boltovskoy, E., Scott, D. B., Medioli, F. S. 1991. Morphological variations of benthonic foraminiferal tests in respons to changes ecological parameters: a review. J. Paleont., 65, 2, 175 184. Chamney, T. P. 1976. Foraminiferal morphogroup symbol for paleoenvironmental interpretation of drill cutting samples: Arctic America, Albian continental margin. Marine Sediments, Sp. publ., 1B, 585 624. Corliss, B. H. 1985. Microhabitats of benthic foraminifera within deep-sea sediments. Nature, 314, 435 438. Corliss, B. H., Chen, C. 1988. Morphotype patterns of Norwegian Sea deep-sea benthic foraminifera and ecological implications. Geology, 16, 8, 716 719. Gradstein, F. M., Berggren, W. A. 1981. Flysh-type agglutinated foraminifera and the Maestrichtian to Paleogene history of the Labrador and North Seas. Mar. Micropaleont., 6, 211 268. Jones, R. W., Charnock, M. A. 1985. Morphogroups of agglutinated foraminifera. Their life positions and feeding habits and potential applicability in (paleo)ecological studies. Rev. Paleobiol., 4, 311 7320. Juranov, S. 1983. Planctonic foraminiferal zonation of the Paleocene and the Lower Eocene in part of East Balkan Mountains. Geol. Balc., 13, 2, 59 73. Miller, K. G., Gradstein, F. M., Berggren, W. A. 1982. Late Cretaceous to Early Tertiary agglutinated foraminifera in the Labrador Sea. Micropaleont., 28, 1, 1 30. Murray, J. W. 1991. Ecology and Paleoecology of Benthic Foraminifera. Longman Scientific & Technical., 397p. Severin, K. P. 1983. Test morphology of benthic foraminifera as a discriminator of biofacies. Mar. Micropaleont., 8, 65 76. Sinnyovsky, D. 2004. Nannofossil subdivision and stratigraphic range of the Emine Flysh Formation in East Balkan, East Bulgaria. Ann. UMG, 47, Part I Geol. & Geophys., 131 137. Valchev, B. 2003a. Two Types of Paleocene Benthic Foraminiferal assemblages from the coastal Part of east Stara Planina. C. R. de l Acad. bulg. Sci, 56, 3, 43 47. Valchev, B. 2003b. On the potential of Small Benthic Foraminifera as Paleoecological Indicators: Recent Advances. Ann. UMG, 46, Part I Geol. & Geophys., 189 194. Valchev, B. 2003c. Biostratigraphy of the Paleocene of the Coastal Part of East Stara Planina based on Small Benthic Foraminifera. Geol. Balc., 33, 1 2, 47 59. Valchev, B. 2004. Paleocene Benthic Foraminiferal Assemblages from the Coastal Part of East Stara Planina. Ãîä. ÑÓ, Ãåîë.-ãåîãð. ô-ò, 96, êí. 1 Ãåîëîãèÿ, 5 19. Äæóðàíîâ, Ñ. 1994. Ïàëåîöåíñêè ïëàíêòîííè ôîðàìèíèôåðè îò òèïîâàòà îáëàñò íà Åìèíñêà ôëèøêà ñâèòà. Ïàëåîíò. ñòðàòèãð. è ëèòîë., 30, 1 30. Òðèôîíîâà, Å. 1960. Âúðõó ïðèñúñòâèåòî íà ïàëåîöåí â Èçòî íà Áúëãàðèÿ. Ãîä. Óïð. ãåîë. ïðîó â., 10, 155 162. 48