GeolCarp_Vol56_No2_155

GEOLOGICA CARPATHICA, APRIL 2005, 56, 2, 155167

www.geologicacarpathica.sk

Palynology of the Eocene-Oligocene transition in the marginal

zone of the Magura Nappe at Folusz (Western Carpathians,

Poland)

PRZEMYS£AW GEDL

and STANIS£AW LESZCZYÑSKI

Institute of Geological Sciences, Polish Academy of Sciences, Senacka 1, 31-002 Kraków, Poland; ndgedl@cyf-kr.edu.pl

Institute of Geological Sciences, Jagiellonian University, Oleandry 2a, 30-063 Kraków, Poland

(Manuscript received July 10, 2003; accepted in revised form June 16, 2004)

Abstract: Palynological investigations of the deep-marine Upper EoceneLower Oligocene, mainly turbiditic and

hemipelagic sediments exposed at Folusz (Siary Zone of Magura Nappe, Polish part of the Western Carpathians), re-

vealed a prevalence of land plant remains in the palynofacies. Dinoflagellate cysts are the most frequent among marine

palynomorphs. A Priabonian age is found in the lower part of the Szymbark Shale; a Rupelian age is determined for the

investigated part of the Magura Beds. Dinoflagellate cyst distribution shows no major changes, contrary to an outstand-

ing change recorded in the coeval sediments from other parts of the Polish Carpathians. This implies different

paleoenvironmental conditions in the northern part of the Magura Basin during the latest Eocene and Early Oligocene.

Occurrence of high-latitude dinoflagellate cysts in the lowermost part of the section may be related to a drop of temperature

in the surface waters of the sedimentary basin during the Late Eocene. Dinoflagellate cysts, whose motile stages are thought

to have inhabited near-shore waters, are frequent in turbidites, whereas the hemipelagic/pelagic sediments usually contain

more numerous oceanic specimens. Recycled dinoflagellate cysts occur more frequently in turbidite sediments.

Key words: Carpathians, Eocene-Oligocene transition, Magura Nappe, paleoenvironment, biostratigraphy, flysch deposits,

dinocysts.

Introduction

The Eocene-Oligocene transition in the northern part of the

Magura Nappe (Siary Zone sensu Koszarski et al. 1974) of the

Polish Carpathians is represented by a rock succession differ-

ent from coeval successions of the other parts of the Polish

Outer Carpathians. Except for some localities in the eastern

sector of the Siary Zone, the succession consists mainly of

thick-bedded (0.5 to a few meters) turbidites with variable

sandstone to shale ratio, distinguished as the Magura Beds

(Szajnocha 1895; widziñski 1934). In some places, in the

marginal part of the eastern sector of the Siary Zone, including

the Folusz area (Fig. 1), the Priabonian consists nearly exclu-

sively of fine-grained sediments of turbiditic and hemipelagic

origin, distinguished by Kopciowski (1996) as the Szymbark

Shale and included in the Zembrzyce Shale by Oszczypko-

Clowes (2001). Age-assessments based on foraminifers indi-

cate that the lower boundary of typical Magura Beds (see

Ksi¹¿kiewicz 1974) is here located close to the Eocene-Oli-

gocene boundary (Blaicher & Sikora 1963; Sikora 1970;

Leszczyñski & Malata 2002). At the same time, in the major

part of the inner zones of the Magura Nappe, this succession is

restricted to the Eocene (Oszczypko-Clowes 2001).

In the other parts of the Polish Outer Carpathians, the

Eocene-Oligocene transition is represented by a several meters

thick package of Globigerina-rich marlstones, distinguished

as the Sub-Menilite Globigerina Marl (Koszarski & Wieser

1960). The lower part of the overlying unit, known as the Me-

nilite Beds, is dominated by black, organic-rich fine-grained

sediments. Similar sediments are also known from some areas

in the southernmost part of the Magura Nappe. The package of

marls rich in Globigerina is distinguished there as the Le-

luchów Marl Member, whereas the unit corresponding to the

Menilite Beds is called the Smereczek Shale Member (Birken-

majer & Oszczypko 1989). The so developed Eocene-Oli-

gocene transition displays a major turnover in microfossil as-

semblages. Rich and diversified Late Eocene foraminifers,

calcareous nannoplankton and dinoflagellate cyst assemblages

become significantly impoverished in the earliest Oligocene

(e.g. Olszewska 1984, 1985; Van Couvering et al. 1981; Gedl

1999). Analysis of organic-walled dinoflagellate cysts (hereaf-

ter dinocysts) from these sediments implies that significant pa-

leogeographical and paleoenvironmental changes occurred,

including a drop in sea surface temperature and salinity de-

crease within the photic zone. This paper aims at describing

and interpreting the palynological record of the Eocene-Oli-

gocene transition in one section from the northern part of the

Magura Nappe, outstanding for its distinctive lithological de-

velopment. Interpretation of the results is compared with the

results of palynological studies of coeval sediments character-

ized by a markedly different development.

Section location and stratigraphy

A 114 m thick succession representing the Szymbark Shale

and the lower part of the Magura Beds, exposed in the bed of

K³opotnica Stream in the village of Folusz was selected for the

PALYNOLOGY OF THE EOCENE-OLIGOCENE TRANSITION OF THE MAGURA NAPPE 157

Fig. 2. Vertical lithofacies logs and lithostratigraphy of the studied

section at Folusz, and sample locations (cf. Leszczyñski & Malata

2002).

Eocene-Oligocene boundary (33.7 Ma according to Berggren

et al. 1995). In the upper part of this unit, Blaicher & Sikora

(1963) found a foraminiferal assemblage corresponding to that

recorded in the Sub-Menilite Globigerina Marl (upper part of

Upper Eocene) of the outer flysch nappes. These authors

called this interval Marls with Globigerina (cf. Sikora

1970). The calcareous nannoplankton Zone NP1920 (Martini

1971) was recognized in the lower part of the Szymbark

Shale, and Zone NP21 in its upper part, ca. 11 m above the

base of the unit in Oszczypko-Clowes (2001), or 17.0 m in

Leszczyñski & Malata (2002).

The overlying 33 m thick succession is built of thin to thick-

bedded fine to very coarse-grained sandstones, chaotic sandy-

mudstones and thick to thin layers of calcareous to non-calcar-

eous mudstones (Fig. 2). This unit is called here the

Zembrzyce Beds, and considered to be the basal part of the

Magura Beds. Calcareous nannoplankton investigations indi-

cate that the entire unit is enclosed within Zone NP21.

Very thick-bedded coarse- to fine-grained sandstones and

granule-conglomerates dominate in the remaining part of the

section (Fig. 2). This part of the section is considered as the

W¹tkowa Sandstone sensu Koszarski (1976). It represents the

higher part of the Magura Beds. The base of calcareous nanno-

plankton Zone NP22 was identified in the top part of the sec-

tion (Oszczypko-Clowes 2001).

Materials

Twenty-one samples from surface outcrops in the

K³opotnica Stream were investigated in this study. These sam-

ples were selected from those taken earlier for other sedimen-

tological and stratigraphical investigations (Leszczyñski &

Malata 2002).

Eleven samples (Fl1Fl25) represent the Szymbark Shale,

seven samples (Fl30Fl37) were taken from the Zembrzyce

Beds, and three (Fl40Fl42) from the W¹tkowa Sandstone

(Fig. 2). All samples except for the Fl30 and Fl35 were taken

from muddy to clayey shales. Their location in the sequence

as well as foraminiferal content and composition suggest

Legend to the Fig. 2.

158 GEDL and LESZCZYÑSKI

hemipelagic and/or turbiditic origin (Table 1;

Leszczyñski & Malata 2002). The samples

Fl30 and Fl35 were taken from a chaotic

sandy-mudstone breccia. This is a sediment

consisting of a sandy calcareous mudstone

(marlstone) matrix with quartz grains as much

as 7 mm in cross-section and chaotically dis-

tributed dark green, brownish and grey, sharp-

edged mudstone chips and larger clasts. These

features indicate deposition by debris flow

mechanisms.

Methods

The samples were processed following

standard palynological procedure, including

38% hydrochloric acid (HCl) treatment, 40%

hydrofluoric acid (HF) treatment, heavy liq-

uid (ZnCl

+HCl; density 2.0 g/cm

) separa-

tion, ultrasound for 1015 sec., and sieving at

15 µm on a nylon mesh. The samples were

processed in the Micropaleontological Labo-

ratory of the Institute of Geological Sciences,

Polish Academy of Sciences, Kraków. The

quantity of rock processed varied from 20 to

30 g. Two microscope slides were made from

each sample using glycerine jelly as a mount-

ing medium. The rock samples, palynological

residues and slides are stored in the collection

of the Institute of Geological Sciences, Polish

Academy of Sciences, Kraków.

All dinocysts were counted from one of two

slides. The second slide was scanned for addi-

tional dinocyst taxa. Slides were examined

under the transmitted light microscope Carl

Zeiss Axiolab. Microphotographs were taken

with the Sony DSC-S75 camera and Zeiss

Plan-Neofluar 100 ×/1.30 Oil Pol objective.

Results

All samples contain organic particles of a

diameter greater than 15 µm. The majority of

these particles represent land plant remains.

They include cuticle with variously preserved

tissue structures, dark brown equidimensional

particles with slightly transparent edges and

opaque, small-sized, woody particles. Sporo-

morphs (mostly the bisaccate pollen grains)

occur subordinately. Amorphous organic mat-

ter occurs in trace amounts only.

Marine palynomorphs, rarely exceeding 1

2 % of the palynofacies, are represented pri-

marily by dinocysts (Figs. 3, 4). Acritarchs

and foraminiferal linings occur occasionally.

The highest amount of dinocysts, reaching

8 % of the palynofacies, is recorded in sam-

Fig. 3. Range chart of dinocysts from Folusz section. Line widths reflect number of

specimens counted. Continued on the page 159.

PALYNOLOGY OF THE EOCENE-OLIGOCENE TRANSITION OF THE MAGURA NAPPE 159

ples Fl4 and Fl7, representing the Szymbark

Shale. Samples Fl34 and Fl41 (the Zembrzyce

Beds and the W¹tkowa Sandstone respectively)

do not contain dinocysts or contain only a few in-

determinable specimens. Acritarchs occur mainly

in the lower part of the Szymbark Shale (samples

Fl1Fl7), being the most frequent in sample Fl4.

They represent morphotypes of Veryhachium af-

finity. Microforaminifers (mainly trochospiral

and planispiral morphotypes) are very rare within

the whole section except for the sample Fl4

where they are relatively frequent.

The dinocyst distribution shows distinct rela-

tion to the sediment origin (Fig. 5). Samples tak-

en from turbidites and mud-flow deposits (Ta-

ble 1) are either devoid of oceanic dinocysts (e.g.

Impagidinium spp.; see e.g. Dale 1996), or they

occur there as single specimens only. Specimens

of Impagidinium (Fig. 4.3,6,8,13) are much more

frequent in samples representing hemipelagites

(Table 1). In these samples, Impagidinium consti-

tutes up to 30 % of all dinocysts (sample Fl22).

The samples taken from turbidites, in turn, con-

tain high numbers of Homotryblium spp., a genus

related by several authors to inshore, lagoonal

settings (e.g. Brinkhuis 1994).

Dinocyst stratigraphy of the Folusz section

The occurrence of calcareous foraminifers and

nannoplankton in the studied succession mainly

in resedimented deposits (see Leszczyñski &

Malata 2002) hampers a precise interpretation of

stratigraphy based on these fossils. Recycling

also concerns dinocysts as has been shown in

these investigations. However, dinocysts also oc-

cur in background sediments (hemipelagites)

where they appear to be synsedimentary. Re-

working makes particularly tentative the identifi-

cation of biozones or events defined according to

the highest occurrences of fossils, for example the

NP21 and the NP22 Calcareous Nannoplankton

Zones of Martini (1971).

Location of the Eocene-Oligocene boundary in

the investigated section has not been precisely es-

tablished during this study. The Early Oligocene

has been definitely determined for the section di-

vision located above sample Fl24 (the topmost

part of the Szymbark Shale) where Areoligera?

semicirculata (Fig. 4.2) has its lowest occurrence

(Fig. 6). This species is known to have its first ap-

pearance in the earliest Oligocene (e.g. Morgen-

roth 1966; Brinkhuis 1994), Rupelian (Stover &

Hardenbol 1993; Stover et al. 1996) or Chattian

(Powell 1992). This agrees with the age

32.8±1.3 Ma, obtained by Van Couvering et al.

(1981) from radiometric dating of the tuffite

found approximately 7 m below the sample Fl24.

The age of the Magura Beds, overlying the Szym-

160 GEDL and LESZCZYÑSKI

Sand fraction

Foraminifera number

Sample

No.

Sediment

colour

Reaction

with

HCl

Bed

thickness

[cm]

CaCO

[%]

TOC

[%]

Detritus

Agglut.

Calc.

Sediment

origin

Fl1

dark brown

3.0

Hemipelagite?

Fl2

green

8.0

Hemipelagite?

Fl4

brown-grey

5.0

17.70

0.46

0.175

572

3256

Turbidite

Fl7

brown

16.0

21.98

0.50

Hemipelagite?

Fl12

green

15.0

0.42

0.18

678

Hemipelagite

Fl15

green

1.0

3208

128

Hemipelagite?

Fl16

beige

2.0

10.25

0.30

504

Hemipelagite?

Fl17

dark brown

0.7

1.17

1.74

200

Hemipelagite?

Fl20

brown

27.0

18.67

0.55

Turbidite

Fl22

beige and green

30.0

6.17

0.28

1132

Hemipelagite?

Fl24

grey-green

>20

~5.0

1190

Turbidite/Hemipelagite

Fl25

dark brown

7.0

0.33

3.20

9.5

Turbidite

Fl30

green/dark grey

75.0

~12.0

400

20868

Mud-flow deposit

Fl32

green/dark grey

, (+)

40.0

Turbidite/Hemipelagite

Fl33

grey

10.0

Hemipelagite?

Fl34

dark brown

19.0

Turbidite

Fl35

grey/green

75.0

~15.0

Mud-flow deposit

Fl36

grey-green

, (+)

22.0

Turbidite/Hemipelagite

Fl37

grey

10.0

Turbidite

Fl40

grey-green

7.0

Turbidite?

Fl41

black

7.0

Hemipelagite?

Fl42

grey

6.0

Turbidite?

Number of foraminiferal specimens calculated for 200 g of dry rock. See Fig. 2 for sample location. Explanation of symbols: + effervescent

reaction with diluted HCl; (+) weak effervescence; lack of effervescence; tr <0.1 %; s several grains; nd not determined.

Table 1: Selected sedimentological and geochemical features of the sampled sediments.

bark Shale, can be estimated on the basis of superposition

only. No typical Oligocene dinocysts like Wetzeliella gochtii,

Areoligera? semicirculata or Chiropteridium lobospinosum

have been found here. The lack of the latter mentioned species

may suggest an age not younger than NP23. Powell (1992)

and Wilpshaar et al. (1996) recorded the lowest occurrence of

Chiropteridium lobospinosum within this zone. This species

was found in the Polish Carpathians in the Lower Oligocene

of the Podhale Flysch (Gedl 2000) and in the Oligocene Kros-

no Beds, whereas it was not found so far in the lowermost Oli-

gocene in the Menilite Beds (P. Gedl unpubl.).

Other dinocyst events, which may point at the Oligocene

age, are rather disputable. One specimen of Wetzeliella gochtii

(Fig. 4.20) has been found in sample Fl20 (Fig. 6). The lowest

occurrence of this species is often accepted as an indicator of

the Lower Oligocene (e.g. Costa & Downie 1976; Gruas-Cav-

agnetto & Barbin 1988), although some authors claimed that

this species appeared in the Late Eocene (Châteauneuf 1980;

El-Beialy 1988). In the Polish Carpathians, specimens of Wet-

zeliella gochtii have been found in higher part of the Sub-Me-

nilite Globigerina Marl at Krosno and Znamirowice (Bujak in

Van Couvering 1981) or its equivalent at Leluchów (Gedl

2004). In the latter case, the lowest occurrence of Wetzeliella

gochtii comes from a sample where Areosphaeridium dikty-

oplokum has its highest occurrence.

The lowest occurrence of Reticulatosphaera actinocoronata

(Fig. 4.15), a species believed to have appeared for the first

time in the Oligocene in the middle latitudes (e.g. Manum et

al. 1989), was recorded in the Priabonian part of the Szymbark

Shale (sample Fl4). On the other hand, Brinkhuis (1994) dem-

onstrated the first appearance of this species in central and

northern Italy in the Late Eocene (basal part of the NP21

Zone). An even younger first appearance, early Late Eocene,

was recorded by Coccioni et al. (2000) in central Italy. This

event was correlated with subChron16n and calcareous nan-

noplankton Zone NP19/20. The lowest occurrence of Reticu-

latosphaera actinocoronata in the Folusz section can also be

correlated with the Zone NP19/20 since this species occurs to-

gether with Areosphaeridium michoudii.

The age of the lower part of the Szymbark Shale (below the

sample Fl7) is Late Eocene (Priabonian). This is shown by the

co-occurrence of dinocyst species Areosphaeridium diktyoplo-

kum (Fig. 4.11), Areosphaeridium michoudii (Fig. 4.10) and

Rhombodinium perforatum (Fig. 4.24) in this interval (Fig. 6).

The last appearance of Areosphaeridium diktyoplokum, which

has the highest consistent occurrence in sample Fl7 (Fig. 6),

was commonly believed to have taken place at the Eocene-

Oligocene boundary (e.g. Biffi & Manum 1988; Stover et al.

1996), although some authors also found it in the Lower Oli-

gocene (e.g. Maier 1959; Benedek 1986). Brinkhuis (1994)

demonstrated the Early Oligocene last appearance of this spe-

cies in Italy (for discussion see also Berggren et al. 1995 and

Brinkhuis & Visscher 1995). Areosphaeridium michoudii has

its highest known occurrence at the top of the NP18 Zone in

the North Sea (Bujak & Mudge 1994). However, distribution

of this species in the flysch Carpathians suggests its highest

occurrence within the NP19-20 Zone (lower part of the Sub-

Menilite Globigerina Marl; P. Gedl unpubl.). The highest con-

sistent occurrence of Areosphaeridium michoudii in the stud-

ied section is recorded in sample Fl12, which is located higher

than the highest consistent occurrence of Areosphaeridium

diktyoplokum (sample Fl7). A Priabonian age of the lower part

of the Szymbark Shale in the Folusz section is also indicated

by the presence of Rhombodinium perforatum. This species

PALYNOLOGY OF THE EOCENE-OLIGOCENE TRANSITION OF THE MAGURA NAPPE 163

age of the lower part of the Szymbark Shale up to the sample

Fl7 (basal 8 meters of the section). Foraminifers interpreted by

Malata (in Leszczyñski & Malata 2002) indicate a Late

Eocene age up to the sample Fl22. The assemblage from sam-

ples Fl18Fl22 indicates an age close to the Eocene-Oli-

gocene boundary. This means that the lowest occurrence of

Wetzeliella gochtii, found in sample Fl20, is in the uppermost

Eocene. Moreover, this implies that Wetzeliella gochtii in the

Carpathian Flysch Basin appeared for the first time in the lat-

est Eocene. Van Mourik & Brinkhuis (2000) noted a Late

Eocene first appearance of this species from a low-latitude set-

ting in the Atlantic Ocean. These records suggest diachronous

first appearance of Wetzeliella gochtii, starting from low lati-

tudes.

Calcareous nannoplankton, in turn, was interpreted by Osz-

czypko-Clowes (2001) to indicate the middle Priabonian, cor-

responding to the Zone NP1920, for the ca. 11 m thick, basal

part of the Szymbark Shale (i.e. approximately up to the posi-

tion of our sample Fl12). Upper Priabonian to lower Rupelian,

corresponding to the Zone NP21, was suggested there for the

overlying part of the section, which according to the lithos-

tratigraphy used in this paper, embraces the higher part of the

Szymbark Shale and majority of the Zembrzyce Beds. Inter-

pretations of calcareous nannoplankton by Oszczypko-Clowes

(in Leszczyñski & Malata 2002) suggest a middle Priabonian

age for the Szymbark Shale up to the sample Fl18, found at

least up to ca. 17 m above the lower boundary of the unit.

Dinocysts indicate the Lower Oligocene (Rupelian) in the

section above sample Fl24. The age based on foraminifers

from sample Fl24 was interpreted as undivided Priabonian-

Rupelian. The lowest occurrence of Early Oligocene foramini-

fers was identified first in the sample Fl30 (mud-flow deposits

containing a rich dinocyst assemblage interpreted as recycled

Eocene). This sample is located in the lower part of the Zem-

brzyce Beds. A higher part of the lower Rupelian, correspond-

ing to the Zone NP22, was identified with calcareous nanno-

plankton in the topmost part of the Zembrzyce Beds and in the

remaining part of the section (Oszczypko-Clowes 2001; note:

the position of the NP21 has been erroneously indicated there

in fig. 44). Noteworthy, the chronostratigraphy of the succes-

sion in question as interpreted by Oszczypko-Clowes (2001)

on the basis of calcareous nannoplankton data, suggests that

nearly exclusively synsedimentary nannoplankton occurs in

the resedimented deposits. This is difficult to comprehend,

particularly in typical Magura Beds, which show features in-

dicative of intensive, large-scale resedimentation.

Recycling of dinocysts

Recycling of dinocysts appears to have occurred in the stud-

ied sediments on a much larger scale than in coeval sediments

in other parts of the flysch Carpathians. Pre-Eocene dinocysts

are infrequent, represented mainly by single specimens. The

oldest are Middle Jurassic species, represented by Ctenido-

Fig. 7. Bio- and chronostratigraphic interpretation of studied section.

164 GEDL and LESZCZYÑSKI

dinium ornatum-C. combazii, Nannoceratopsis gracilis and

Nannoceratopsis dictyambonis. They were found in the lower-

most part of the Szymbark Shale (samples Fl2 and Fl4) and in

the Zembrzyce Beds (samples Fl32 and Fl37). One Early Cre-

taceous (Pseudoceratium pelliferum) and rare Late Cretaceous

dinocysts (e.g. Chatangiella ditissima, Trigonopyxidia ginel-

la) were found mainly in the Szymbark Shale. One specimen

of Late Paleocene-Early Eocene Apectodinium quinquelatum

was found in the Zembrzyce Beds (sample Fl37).

The Eocene taxa dominate among the dinocysts believed to

be recycled. The most frequent are the Late Eocene species

found in the Lower Oligocene part of the section. Mud-flow

deposits (samples Fl30 and Fl35) and associated deposits

(sample Fl36) exposed in the basal part of the Zembrzyce

Beds contain numerous specimens of Areosphaeridium mi-

choudii, Areosphaeridium diktyoplokum and Cordosphaeri-

dium funiculatum. Their presence indicates that these deposits

represent Upper or Middle Eocene sediments recycled during

the Early Oligocene. Several Middle Eocene species were

found in the Upper Eocene part of the section (e.g. Diphyes

pseudoficusoides), while a single specimen of Early-Middle

Eocene Eatonicysta ursulea was found in the Oligocene part

of the Szymbark Shale.

There is no difference in the state of preservation between

the forms treated as recycled or the in situ ones. That is why it

is difficult to distinguish whether a given species with known

early Late Eocene top-range (e.g. Areosphaeridium michou-

dii) is recycled or not in the higher part of the Upper Eocene of

the studied section.

Paleoenvironment

The paleoenvironmental conditions in the northern part of

the Magura Basin during the Late Eocene and Early Oligocene

were reconstructed earlier mainly on the basis of lithofacies

distribution and foraminiferal associations (e.g. Ksi¹¿kiewicz

Ed. 1962; Sikora 1970; Bromowicz 1992; Leszczyñski &

Malata 2002). The shape of the basin, its bathymetry and bot-

tom life conditions were the most essential in these interpreta-

tions. The palynological, and particularly dinocyst data pre-

sented in this paper, supply new information about paleo-

environmental conditions in this part of the Magura Basin.

A characteristic feature of the Eocene-Oligocene transition

in the Polish Outer Carpathians is a significant change of the

dinocyst assemblage. Diversified Late Eocene dinocyst as-

semblages disappeared during the earliest Oligocene or they

were replaced by Peridinioid-dominated assemblages repre-

sented mainly by Deflandrea (Fig. 4.19) and Wetzeliella

(Fig. 4.20). At the same time, a considerable increase of land-

derived elements of palynofacies and amorphous organic mat-

ter is recorded (Gedl 1999). These changes have been record-

ed from several sections within the Silesian, Dukla and Skole

tectonic units, and from a single section (Leluchów) within the

southernmost zone of the Magura Nappe. The changes were

interpreted as a result of eutrophication of the surface waters

caused by fresh water influx into the Carpathian Flysch Basin

(Gedl 1999) and appearance of disoxic/anoxic bottom condi-

tions during sedimentation of the Early Oligocene Menilite

Beds (or their equivalents).

The changes that took place during the Eocene-Oligocene

transition in the northern part of the Magura Basin seem to dif-

fer from those in other parts of the Carpathian Flysch Basin.

No such prominent change in the dinocyst assemblages, com-

parable to that known from coeval sediments of the other parts

of the Outer Carpathians, was noted in the studied material.

However, this may result from increased reworking, especially

in the turbidites. A change in the quality of the dinocyst as-

semblages is recorded when hemipelagic samples exclusively

are taken into account. Among the samples treated as hemipe-

lagic Lower Oligocene sediments (Table 1), two (Fl32 and

Fl41) are devoid of dinocysts or contain very infrequent ones.

This may result from the appearance of paleoenvironmental

conditions within the photic zone, which were inconvenient

for dinoflagellates. Noteworthy, palynofacies implies land

proximity of the sedimentary area.

Paleogeography: The location of the Siary Zone in margin-

al part of the Magura Nappe together with lithofacies distribu-

tion and paleocurrent directions were long ago interpreted as

indicative of location of this zone close to the northern margin

of the Magura Basin (e.g. Ksi¹¿kiewicz Ed. 1962). However,

the presence of Impagidinium spp. in hemipelagites indicates

an offshore setting of the sedimentary area of the studied de-

posits. The lack or infrequent occurrence of this genus in tur-

bidites, where near-shore species prevail, indicates resedimen-

tation of turbidites from inshore areas bordered by a landmass.

Presence of a land on this side of the Magura Basin is suggest-

ed by the mass occurrence of land plant remains, which domi-

nate the turbidite palynofacies. The domination of terrestrial

elements (phytoclasts and sporomorphs) may result from a

strong runoff, although scarcity of Peridiniales suggests no

freshwater influx into this part of the Magura Basin (cf. e.g.

Biffi & Grignani 1983). Phytoclasts and sporomorphs could

also be recycled from older sediments as it is supported by the

presence of recycled dinocysts, obviously derived from older

sediments.

A ridge, suggested by Ksi¹¿kiewicz (1956), called the Sile-

sian cordillera (Fig. 8), is generally accepted as the northern

border of the Magura Basin. It remains an open question

whether it was a land or a submerged ridge. Nemèok et al.

(2000) proposed a different paleogeographical setting for the

Magura Basin, with the Bohemian Massif as its northern bor-

der. The palynological analysis does not solve the question

whether the Bohemian Massif or Silesian cordillera was the

northern margin of the Magura Basin, but in the latter case, at

least some parts of this ridge, at least for some time, must have

formed islands covered by vegetation.

A different paleogeographic location is identified for the

southernmost part of the Magura Basin during the Late

Eocene-Early Oligocene. Late Eocene dinocysts (numerous

Impagidinium and Nematosphaeropsis spp.; see Dale 1996)

from coeval deposits at Leluchów (Krynica Zone) imply a

depositional setting located far from the seashore (Gedl 2004).

The change in the Leluchów dinocyst assemblages and pa-

lynofacies close to the Eocene-Oligocene boundary (estab-

lished on the basis of the highest occurrence of Areosphaeri-

dium diktyoplokum) is similar to that known from the outer

nappes of the Carpathians. The low-salinity dinocysts (mainly

Deflandrea spp.) dominate in the lowermost Oligocene of Le-

PALYNOLOGY OF THE EOCENE-OLIGOCENE TRANSITION OF THE MAGURA NAPPE 165

luchów, and disappear higher up the section. These conclu-

sions imply major regional differences between northern and

southern margins of the Magura Basin during the Late Eocene

and Early Oligocene.

Sea surface temperature: Dinoflagellates, that is inhabit-

ants of the photic zone, as well as their cysts serve as a tenable

indicator of the sea surface temperature. The Eocene-Oli-

gocene transition is known as a time of marked global cooling

(e.g. Pomerol & Premoli Silva 1986). Brinkhuis (1994), who

traced the records of high latitude dinocyst species within the

Eocene-Oligocene boundary interval in Mediterranean, recog-

nized sea surface temperature fluctuations. For this reason he

used several, both inshore and offshore species, whereas

Zevenboom (1995) argued that only oceanic taxa are suitable

for proper estimation of the sea surface temperature. Three

species of oceanic dinocysts found in the Folusz section are

treated as high latitude ones. These are Impagidinium velorum

(Fig. 4.6), Impagidinium pallidum (Fig. 4.13) and Gelatia in-

flata (Fig. 4.16) described for the first time by Bujak (1984)

from the Bering Sea. These species have been found in the

lower part of the Szymbark Shale. Their presence may reflect

a cooling phase in the Late Eocene, which caused a drop in sea

surface temperature during sedimentation of the lower part of

the Szymbark Shale. This event seems to correspond to that

documented in coeval sediments of the other parts of the Car-

pathians where high latitude dinocysts Impagidinium velorum,

Impagidinium pallidum and Gelatia inflata have been found

as well (Gedl unpubl.).

Bottom water oxygenation: Analysis of trace-fossil and

benthic foraminiferal assemblages from the Siary Zone indi-

cate poorly oxic to slightly dysoxic conditions prevailing in

the bottom waters during the Late Eocene and Early Oli-

gocene (Leszczyñski & Malata 2002). This interpretation is

supported by the results of our study. The studied sediments

contain only occasional traces of amorphous organic matter,

which is usually associated with anoxic environments (e.g.

Batten 1996). This feature highly contrasts with high content

of amorphous organic matter in the Lower Oligocene Menilite

Beds and its equivalents in the other parts of the flysch Car-

pathians (Gedl unpubl.). A better ventilation of the sea floor in

the northern part of the Magura Basin during the Early Oli-

Fig. 8. Schematic paleogeographic map of Alpine and peri-Alpine

part of Europe during Eocene-Oligocene transition (based on Rögl

1999, modified by S. Leszczyñski). Probable location of investi-

gated section arrowed.

gocene might have been caused by intensified water circula-

tion resulting from a high frequency of large-scale resedimen-

tation events (Leszczyñski 2001).

Conclusions

1. Dinocysts indicate that the lower part of the Szymbark

Shale in the Folusz section (up to the sample Fl7) represents

the Upper Eocene (Priabonian). This interpretation is based on

continuous presence of Areosphaeridium michoudii, Areo-

sphaeridium diktyoplokum and Rhombodinium perforatum.

Several species characteristic for the Middle Eocene (e.g.

Heterelaucacysta porosa, Diphyes pseudoficusoides) that oc-

cur in this part of the section are recycled. The uppermost part

of the Szymbark Shale, located above the sample Fl24, and

the overlying Magura Beds represent the Lower Oligocene.

This interpretation is based on the lowest occurrence of Areo-

ligera? semicirculata in the sample Fl24. Wetzeliella gochtii, a

typical Oligocene species in north-western Europe, has the

lowest occurrence in the studied section in sample Fl20, dated

by foraminifers as Priabonian. Another Oligocene species, Re-

ticulatosphaera actinocoronata, has its lowest occurrence in

the basal part of the section, dated by other dinocysts, fora-

minifers and calcareous nannoplankton as Priabonian.

2. Two dinocyst assemblages differing in origin occur in the

fine-grained sediments of the entire section. Sediments recog-

nized as redeposited contain frequent near-shore dinocysts. In

contrast, the fine-grained sediments interpreted as background

deposits always contain specimens of oceanic dinocyst genus

Impagidinium.

3. No apparent change in quality of dinocyst assemblages is

observed in the studied section between the Late Eocene and

Early Oligocene assemblages. This contrasts with substantial

changes in dinocyst assemblages in coeval sediments of the

other parts of the Polish Carpathians. This difference implies

various paleoenvironmental conditions, including nutrient

availability and salinity level in the photic zone of the north-

ern part of the Magura Basin. However, increased dinocyst re-

cycling observed in the Folusz section may significantly mask

the true conditions. Two Lower Oligocene hemipelagic sam-

ples containing poor dinocyst assemblages appear to reflect

inconvenient paleoenvironmental conditions in the photic

zone.

4. The appearance of high-latitude Impagidinium velorum,

Impagidinium pallidum and Gelatia inflata in the Upper

Eocene of the investigated deposits is interpreted as resulting

from a drop of sea surface temperature in the Magura Basin

during the latest Eocene. This event, which is also recorded in

coeval sediments of the other parts of the Polish Carpathians,

seems to be of regional significance and appear to correspond

to the global cooling recorded across the Eocene-Oligocene

boundary.

Acknowledgments: We thank H. Brinkhuis, J. P. Bujak and J.

Soták for their critical remarks that improved the manuscript

greatly. The Folusz section was described and sampled by

Stanis³aw Leszczyñski in the frame of the project financed by

the State Committee for Scientific Research (Komitet Badañ

166 GEDL and LESZCZYÑSKI

Naukowych) research Grant No. 6 P04D 021 16. Palynologi-

cal study was done by Przemys³aw Gedl as a part of the State

Committee for Scientific Research (Komitet Badañ Nauko-

wych) research Grant No. 6P04D 042 15.

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