Pomeranian basin (NW Poland) and its sedimentary evolution during Mississippian times

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GEOLOGICAL JOURNAL
Geol. J. 43: 123–150 (2008)
Published online in Wiley InterScience
(www.interscience.wiley.com) DOI: 10.1002/gj.1117

Pomeranian basin (NW Poland) and its sedimentary evolution during
Mississippian times
HANNA MATYJA*
Department of Regional Geology, Mineral Resources and Geophysics, Polish Geological Institute,
Warsaw, Poland

The Carboniferous sedimentary history of the Pomeranian Basin (NW Poland) begins with Hastarian open-marine carbonates
and is terminated with ?lower Asbian terrestrial deposits in the north-eastern part and, ?upper Asbian or Brigantian, open-marine
shales in the south-western part of the basin. The ?latest Viséan, Serpukhovian and early Bashkirian was a period of regional
non-deposition and erosion. In the Upper Bashkirian–Gzhelian strata, an alluvial depositional environment was recognized.
The Mississippian depositional history of the area has been punctuated by several, regional-scale events: (1) during the late
Famennian–early Tournaisian times anoxic conditions developed over the entire basin. The results of both conodont and
miospore studies show the presence of a stratigraphic gap within this sequence (which also show extremely reduced
thicknesses), that comprises the uppermost Famennian (Middle and Upper praesulcata conodont zones) and the lowermost
Hastarian (sulcata–sandbergi conodont zones). This stratigraphic gap probably resulted from some chemical and/or hydro-
dynamical factors rather than from any tectonic uplift; (2) volcanic activity on the nearby East European Craton (EEC), which
was the source of large amounts of detrital (volcaniclastic) material supplied to the Pomeranian Basin during the Early
crenulata–?early anchoralis-latus chrons (late Hastarian–early Ivorian), caused with time the gradual shallowing of the
sedimentary environment. This shallowing trend began in the Early typicus Chron (early Ivorian) and terminated with terrestrial
deposits in the early Asbian.
The sedimentary succession and specific phenomena recognized in this structurally unstable basin, displays a pattern partly
different from that observed in some areas in Europe. It would appear that other local factors, such as tectonic mobility of the
hinterland area (EEC) and the Pomeranian Basin floor, were the possible causes of observed variations and relative sea-level
changes. Copyright # 2008 John Wiley & Sons, Ltd.

Received 20 July 2007; accepted 7 March 2008

KEY WORDS stratigraphy; facies development; sedimentary evolution; Mississippian; Carboniferous; Pomeranian Basin; NW Poland

1. INTRODUCTION

Over 70 boreholes have penetrated Carboniferous deposits in the Western Pomerania area (NW Poland). Of these,
over 30 have been studied in detail (Muszyński et al. 1996; Matyja et al. 2000). The majority of the boreholes have
penetrated only part of the Carboniferous sequence, with ?part of the Brigantian, Serpukhovian and part of the
Baskhirian absent. However, there are some boreholes, none of which were fully cored, that have penetrated an
almost complete Tournaisian and Viséan succession. The north-easternmost part of Western Pomerania, extending
close to the Teisseyre-Tornquist Zone (TTZ) between Koszalin in the north-west and Chojnice in the south-east
(referred to as the Koszalin–Chojnice Zone), is characterized by a high degree of tectonic deformations (Figure 1),
as well as a good representation of Tournaisian and Viséan strata. The south-westernmost part of the area, extending

* Correspondence to: H. Matyja, Department of Regional Geology, Mineral Resources and Geophysics, Polish Geological Institute, Rakowiecka
4, PL 00-975 Warsaw, Poland. E-mail: hanna.matyja@pgi.gov.pl

124

                Copyright # 2008 John Wiley & Sons, Ltd.
                                                                                                                                                                                                                                        h. matyja

                                                           Figure 1. Location of some boreholes on the sub-Permian map of Western Pomerania—after Matyja (2006), simplified and modified; location of some deep crustal fractures and
                                                           important faults after Królikowski et al. (1999) and Dadlez (1997, 2000, 2006). TESZ ¼ Trans-European Suture Zone; DLF ¼ Dolsk Fault, SW boundary of TESZ (Dadlez 2006).

Geol. J. 43: 123–150 (2008)
            DOI: 10.1002/gj

sedimentary history of the pomeranian basin (nw poland) 125

between the Laska 2 borehole in the north-west and the Wilcze IG 1 borehole in the south-east (referred to as the
Laska–Czaplinek Zone), is more poorly explored: only a few boreholes with uppermost Tournaisian and Viséan
deposits were drilled, over a distance of more than 200 km.
The present-day distribution of the upper part of the Carboniferous (Pennsylvanian) succession, that is part of
the Westphalian and the Stephanian, is limited to the area between Sarbinowo in the east and Kamień Pomorski in
the west, and to the western part of the Polish sector of the Baltic Sea, as well as in the south-westernmost part of the
Western Pomeranian region (Figure 1).
One of the typical features of the Western Pomeranian region is the strong primary variation in the thicknesses of
Devonian and Carboniferous deposits. Incomplete Mississippian deposits are several hundred metres to 1600 m
thick near the edge of the East European Craton (EEC), but range between 1300 and 1800 m in the south-western
part of the study area. Incomplete Pennsylvanian deposits vary from 100 to 250 m in thickness, reaching
approximately 700 m and even 1200 m in the Baltic Sea offshore area. Analysis of facies and thickness distribution
clearly shows a variable subsidence of the basement in individual basin segments (Matyja 1993; Matyja et al. 1995;
Świdrowska and Hakenberg 1996; Matyja et al. 2000, figures 18 and 19). Although the multi-block structure of the
sub-Permian basement developed mainly during the Late Carboniferous, the cited data support the suggestion
presented many years ago that repeated reactivation of deep crustal fractures controlled the thickness distribution
and development of faults in the Palaeozoic sequences (Dadlez 1978, 2006). Their sedimentary activity during
Devonian and Carboniferous times affected both the facies distribution in the basin and the thickness of deposits in
individual basin segments (?sub-basins). However, borehole sections with relatively complete Carboniferous strata
are rare. Primary thickness was strongly reduced by syndepositional, post-Viséan and post-Carboniferous erosion,
which resulted both from uplifting movements of the individual tectonic blocks and pre-Zechstein peneplanation of
the area (Dadlez 1978; Matyja 1993; Matyja et al. 2000).

2. REGIONAL STRUCTURAL GEOLOGY

During the Devonian and Carboniferous times, the Pomeranian Basin was situated within the Trans-European
Suture Zone (TESZ), between the stable EEC and the Variscan-influenced areas to the south-west. The deep crustal
fracture—the Teisseyre-Tornquist Zone (TTZ), marks the profound crustal boundary between the EEC and the
typical TESZ crust. The north-eastern part of the TTZ coincides more or less (Figure 1) with the north-eastern
extent of deformed Lower Palaeozoic strata (Caledonian Deformation Front—CDF), with the present-day
north-eastern erosional margin of Devonian and Carboniferous deposits, and with the Koszalin–Chojnice Fault
Zone that has been repeatedly reactivated during the Permian–Mesozoic evolution of the Polish Basin and during
the Late Cretaceous–Palaeocene inversion of the Mid-Polish Trough (Dadlez 2006). The Koszalin–Chojnice Zone
was interpreted by some authors as a crustal fragment detached from the northern margin of Gondwana and
subsequently docked alongside Baltica during the Early Palaeozoic (e.g. Franke 1995). Following the studies
presented by Krzemiński and Poprawa (2006), and Poprawa et al. (2006), its Early Palaeozoic history seems to be
connected with the East European Craton (Baltica), as it was suggested earlier by Dadlez (Dadlez et al. 1994;
Dadlez 2000).
The SW boundary of TESZ, marked by the Dolsk Fault (Figure 1—the inset map), across which the consolidated
crustal layer is replaced by a crystalline Variscan upper crust, is evident only on two deep seismic profiles, LT-7 and
P4, and the deformation front of the Variscan Externides (VDF) is located some 100 km north-eastwards of the
Dolsk Fault within the confines of the TESZ crust (Dadlez 2006).
Significant lateral changes and thickness of the crystalline crust as well as differences in the composition of its
sedimentary cover were noted on the individual crustal blocks within the TESZ, that is on the Pomeranian,
Kuiavian and Holy Cross Mts. segments. These changes in the crustal configuration appear to be controlled by deep
crustal fractures, such as the Koronowo–Margonin or Włocławek–Konin faults (Dadlez 1997, 2000; see also
Figure 1) or the Poznań–Bydgoszcz–Toruń tectonic Zone that separates the Pomeranian and the Kuiavian segments

126 h. matyja

(Dadlez 2006). Whether these faults separated individual terranes or individual blocks of the same terrane is
unknown (Dadlez 2006).
The deep seismic profiles performed within the TESZ indicate that this specific mosaic of crystalline crustal
blocks is covered to a depth of 7–8 km (Guterch et al. 1994; Grad et al. 1999) by a Palaeozoic sedimentary
succession. None of the boreholes drilled in the Western Pomerania region (located on the Pomeranian segment)
reached the TESZ crystalline crust and the oldest identified sedimentary rocks belong to the Ordovician, to the
upper part of the Llanvirnian and to the Caradocian British Series (Podhalańska and Modliński 2006).
The present-day, north-eastern erosional margin of Devonian and Carboniferous strata appears to be controlled
by a fault or a set of faults (Figure 1). Most probably, these sediments originally extended far onto the EEC (Matyja
1993, 1997; Lipiec and Matyja 1998). The extent of Devonian and Carboniferous epicontinental basins to the
south-west is approximately coincident with the VDF (Dadlez 1997).

3. LITHOSTRATIGRAPHY AND DEPOSITIONAL ENVIRONMENTS OF THE CARBONIFEROUS
SUCCESSION

The first attempt to present the arrangement of the Carboniferous lithological units and their general depositional
environments was made by Dadlez (1978). Subsequently, Żelichowski (1983, 1995) revised Dadlez’s
lithostratigraphical scheme and subdivided the Carboniferous strata into several informal units referred to as
‘complexes’. Lipiec (in Lipiec and Matyja 1998; Lipiec 1999) modified the subdivisions of Żelichowski in the
Tournaisian and Viséan sections.
Recently, some modifications, concerning the hierarchy and a more detailed assessment of the Mississippian
lithostratigraphic units have been proposed, based on new analytical data (Matyja et al. 2000; Matyja 2006). The
characteristics of the Carboniferous lithostratigraphic units and the pattern of their spatial and temporal
relationships presented here include these modifications (Figure 2).
The Western Pomeranian region consisted of two parts (?sub-regions) during its Devonian and Lower to Middle
Mississippian history: a north-eastern and a south-western one. They corresponded to two very roughly defined
facies zones, a relatively shallower water facies in the north-east and a deeper water facies in the south-west
(Matyja 2006). Their mutual relationships follow the natural depositional dip in the Pomeranian sedimentary basin.
However, the precise delimitation of a boundary between these sub-regions within the basin, in order to reflect
facies differences during its Devonian and Carboniferous history, would be highly hypothetical due to the
incompleteness of the available data.

3.1. The north-eastern part
This part of Western Pomerania coincides with a relatively narrow area extending between Sarbinowo in the
north-west and Brda, Rzeczenica and Wierzchowo in the south-east, to the south-west of the Koszalin–Chojnice
Fault Zone (Figure 1). Six lithostratigraphic formations have been established here in the Mississippian succession
(Figure 2), the oldest one, the Sa˛polno Calcareous Shale Fornation (85–600 m), belonging partly to the Famennian
and partly to the Tournaisian.
The Famennian part of the Sa˛polno Calcareous Shale Formation consists of dark fossiliferous marly limestones
(with crinoids, Palaeosiphonocladales algae, calcareous and encrusting foraminifers, benthic ostracods, rare
brachiopods and laminar stromatoporoids) in the shallower part of the basin and dark fossiliferous marls (with
ammonoids, entomozoacean ostracods, conodonts, trilobites, bivalves, gastropods, brachiopods and solitary corals)
in the deeper part of the basin (Matyja 1993; Matyja and Stempień-Sałek 1994).
The Devonian/Carboniferous passage interval is marked by black anoxic shales which show a general absence of
fossils.
The Tournaisian part of the Formation consists mainly of black, often fine-laminated clayey deposits (Figure 2),
in which macrofaunal remains are relatively rare, as well as dark marly limestones and marls containing rare

sedimentary history of the pomeranian basin (nw poland) 127

Figure 2. Lithostratigraphic units and the pattern of their spatial and temporal relationships, Western Pomerania.

goniatites, trilobites, brachiopods and bivalves (Korejwo 1993). Microorganisms are represented by conodonts,
miospores and ostracods (Matyja et al. 2000).
The Tournaisian part of the Sa˛polno Calcareous Shale Formation is a succession of open-marine carbonate and
clayey deposits, formed well below wave base, under conditions of oxygen deficiency. The Formation reflects the
distal outer ramp phase of sedimentation and was probably widespread throughout the whole Pomeranian area as
indicated by its depositional setting (Matyja 2006).
The Trzebiechowo Marl Formation (600 m) is composed mainly of marls and marly limestones (Figure 2). The
fauna is represented by brachiopods, echinoderms, bryozoans, bivalves and gastropods. Microorganisms such as
ostracods, miospores, conodonts and foraminifers have also been encountered. Interbedded fine- to coarse sand-size,
often graded, packstones and grainstones have been noted. Allochthonous grains include ooids, intraclasts, and
bioclasts of a shallow-water fauna, derived from the foreslope of a carbonate platform, which was situated probably
to the east or north-east. The grainstone beds thin out and become finer towards the SW, to the centre of the basin.
Subordinately, occur fine-grained quartz and arkosic sandstones composed of volcaniclastic detritus.
The Trzebiechowo Marl Formation is the lateral equivalent of the Tournaisian part of the Sa˛polno Calcareous
Shale Formation, and is known only from a part of the Pomerania area, close to the Brda, Biały Bór, Bielica and
Rzeczenica sections (Matyja et al. 2000). Marls and limestones of the Trzebiechowo Marl Formation reflect the
outer/middle ramp phase of sedimentation.
The Gozd Arkose Formation (70–370 m) comprises grey and pink fine- to very coarse-grained arkosic sandstones
(volcaniclastic sandstones in Muszyński et al. 1996), locally calcareous (Figure 2). The observed sedimentary
structures reflect the shallowing upward succession (Muszyński et al. 1996). The composition of the volcaniclastic
sandstones does not change much through the succession (Muszyński et al. 1996) and there is no lateral variation in
their composition along strike (Muszyński 1976; Krzemiński 1999). Poorly- to moderately-sorted dark grey and

128 h. matyja

black fragments (clasts) of acidic volcanic rocks, crystaloclasts of sanidine and quartz, and numerous
pseudomorphs after volcanic glass predominate throughout; lava clasts are, in most cases, very fine-grained,
aphanitic or contain spherulites after volcanic glass (Muszyński et al. 1996). At or near the base of some sandstone
beds, shale and siltstone clasts have been noted. Subordinately, occur interbeds of tuffites, claystones, marls and
oolitic limestones.
This very characteristic unit is noted throughout the north-eastern part of the Pomerania area, from Grzybowo in
the west, eastwards through Sarbinowo, Drzewiany to Wierzchowo (Figure 1; see also Matyja et al. 2000, figures 18
and 19). The Gozd Arkose Formation reflects Tournaisian volcanic activity episodes, related to intraplate
volcanism, supplying material to the marine Pomeranian Basin, probably through immature river and deltaic
systems from the north or north-east. It is still an open question where the intracratonic source of volcaniclastic
material was located (see section 5).
The Kurowo Oolite Formation (35–160 m) includes thickly-bedded, well-sorted, light-grey and pink, mostly
coarse-grained oolite and ooid-skeletal limestones (grainstones) (Figure 2) and, subordinately, ooid-skeletal
grainstones with intraclasts, ooid-peloid grainstones, peloid grainstones and aggregate-grain grainstones.
Small-scale cross-bedding is observed.
Marls, thin layers of black shales and calcareous claystones, and arkosic sandstones occur subordinately. The
ooid-skeletal limestones contain echinoderms, brachiopods, bivalves, corals, bryozoans, calcareous algae, benthic
ostracods, conodonts, miospores and foraminifers.
This unit has been identified in the north-eastern part of the Pomerania area: between Daszewo, Chmielno and
Wierzchowo sections, as well as between Kurowo, Drzewiany and Brda (Figure 1; see also Matyja et al. 2000,
figures 18 and 19).
The presence of well-sorted ooid-skeletal grainstones (with multiple-coated large ooids ranging commonly from
0.5 to 1.5 mm in diameter and worn skeletal particles), together with often observed cross-bedding, points to the
high-energy and very shallow-water barrier/shoal environment. Thus, carbonates of the Kurowo Oolite Formation
reflect the rimmed carbonate shelf phase of sedimentation.
The Grzybowo Calcareous Shale Formation (70–280 m) is composed mainly of black shales, calcareous
claystones and marls (Figure 2). Thin beds of primary or early diagenetic dolomite and anhydrite, as well as nodules
of anhydrite have been noted (Muszyński 1976, 1979). Arkosic sandstones, oolitic limestones and coquinas occur
subordinately. Thin-shelled bivalves, gastropods and rare brachiopods have been recognized, as well as
microorganisms represented by benthic ostracods, rare conodonts, miospores, and small encrusting tube-like
fossils, formerly assigned to ‘vermetid gastropods’, now included within a separate molluscan group—the
Microconchida (see Flügel 2004).
This unit has been recorded in the north-eastern part of the Pomeranian area: between the Grzybowo, Niekłonice,
Biesiekierz, Daszewo, Kłanino and Kurowo sections (Figure 1; see also Matyja et al. 2000, figures 18 and 19).
Low-diversity biota, the presence of fine-grained sediments and evaporites point to a protected, seasonally
restricted lagoon environment, behind barrier(s). Thus, the Grzybowo Calcareous Shale Formation reflects also the
rimmed carbonate shelf phase of sedimentation.
The Drzewiany Quartz Sandstone Formation (400 m) is the uppermost Mississippian lithostratigraphic unit
recorded in the north-eastern part of the area. It contains white and red, fine-grained quartz sandstones, variegated
siltstones and claystones, locally calcareous (Figure 2). Thin beds of primary or early diagenetic dolomites and
anhydrites, as well as anhydrite nodules and palaeosol horizons have been noted (Muszyński 1976). The rare fauna
is limited to a few beds of tempestite origin, and is represented by thin-shelled bivalves, ostracods, brachiopods and
crinoids. Rare goniatites were also reported from these storm-layers in the upper part of the Formation (Korejwo
1993). Ooids have been observed in some coquina layers (Lipiec 1999).
The Drzewiany Quartz Sandstone Formation is well-known from the north-eastern part of the Western
Pomeranian area (cf. Matyja et al. 2000, figures 18 and 19). The Formation was also found in two wells (Okonek-1
and Lipka-1) in the south-western part of the area (Turnau et al. 2005). The top of the Drzewiany Quartz Sandstone
Formation is erosional throughout the area. The Formation reflects the marginal marine and coastal phase of
siliciclastic sedimentation.

sedimentary history of the pomeranian basin (nw poland) 129

The ?Wolin Formation (>100 m): the present-day distribution of Pennsylvanian deposits in the north-eastern part
of the area is limited to the environs of Koszalin. They are represented by fine-grained quartz sandstones and
claystones (Figure 2). Sparse palynological data of Turnau (1978) suggest that these deposits can be assigned to the
Westphalian ?B (Bashkirian) and probably belong to the Wolin Formation sensu Żelichowski (1983) or to its lateral
equivalent.

3.2. The south-western part
In the south-western part of the study area the distribution of Mississippian strata is not as well-documented as in
the north-eastern part. The lowermost strata representing the uppermost Tournaisian and Viséan have been
penetrated by only 12 boreholes. In spite of the few data points, the Mississippian is shown to have a wide
distribution, from the Laska-2 well in the north-west to the Zabartowo and Lipka wells in the south-east (see
Figure 1). The Mississippian succession of the south-western part of the study area is tripartite.
The complete Łobżonka Shale Formation (550 m) remains undrilled in the entire Pomeranian area. Most
probably, however, it is underlain by the Sa˛polno Calcareous Shale Formation (Figure 2; see also Matyja 2006). The
known part of the Łobżonka Shale Formation is predominately composed of black claystones, dark grey mudstones
and grey quartz sandstones. In the lowermost known part of the Formation, however, Żelichowski and Łoszewska
(in Żelichowski 1987), and Lipiec (1999) noted the presence of thin interbeds of calcareous clayey mudstones,
wackestones and skeletal floatstones, containing sparse foraminifers, brachiopods, goniatites and redeposited
ooids, indicating that this part of the succession was probably related to the distal part of a rimmed carbonate shelf
environment (Lipiec 1997, 1999).
The Formation was encountered only in a few boreholes (Moracz IG-1, Czaplinek IG-1, Okonek-1, Lipka-1,
Zabartowo-1, Zabartowo-2, Wilcze IG-1), but originally was probably widespread throughout the whole
south-western Pomerania area, as indicated by its depositional setting. This unit contains basinal, prodeltaic and
deltaic slope deposits (Lipiec 1997, 1999).
The Czaplinek Limestone Formation (400 m) is composed of a variety of carbonate lithofacies including
skeletal grainstones (algal, crinoidal, and bryozoan microfacies), oolitic grainstones, poorly winnowed grainstones,
and occasional micrites (Figure 2). Microfacies analysis (Lipiec 1997, 1999) indicates the presence of a full range
of carbonate shelf facies environments, including (1) a lagoon represented by skeletal wackestones with sponge
spicules and algae, peloidal wackestones, aggregate-grain wackestones and packstones, (2) extensive shallows and
barriers represented by oolitic and skeletal grainstones, (3) an open shelf characterized by poorly-washed
grainstones, packstones, skeletal wackestones with echinoderms, foraminifers, cryptostome and trepostome
bryozoans, algae with the dominant species of Kamaenella, as well as (4) a carbonate platform margin environment
with skeletal floatstones, packstones and wackestones.
The extent of the Czaplinek Formation, encountered only in the Czaplinek IG-1, IG-2, Piaski PIG-2, Moracz
IG-1 and Laska-2 wells, is not as widespread. This Formation was deposited on a rimmed carbonate shelf (Lipiec
1999).
Nadarzyce Shale Formation (300 m): the carbonate shelf deposits are overlain by a series of grey claystones
representing the Nadarzyce Shale Formation (Figure 2). Bioturbations, siderite concentrations and surfaces coated
with floral detritus are observed here, as well as carbonate interbeds of toe-of-slope facies (Lipiec 1997, 1999),
which contain rare foraminifers (Żelichowski 1987; Lipiec 1999).
The Formation is encountered only in three borehole sections (Moracz IG-1, Błotno-3 and Czaplinek IG-1), but
was probably widespread throughout the entire south-western Pomerania area, as indicated by its depositional
setting. The top of the Nadarzyce Shale Formation is erosional. This unit contains outer shelf siliciclastic sediments
(Lipiec 1997, 1999).
Due to sparse borehole evidence little information can be provided on the real spatial extent of the Pennsylvanian
deposits. Three lithostratigraphic units were recognized in this part of the succession.
Wolin Formation (40–280 m): grey and dark grey claystones and mudstones comprise the major part of the
Formation (Figure 2). Thin coal seams and lenses, as well as Stigmaria roots and plant fragments are noted.

130                                                h. matyja

Thick-bedded, grey, fine- to medium-grained quartz sandstones with cross-stratification and flaser lamination occur
subordinately. Several fining-upward cycles were observed. This part of the Carboniferous succession was related
to a fluvial depositional system, characterized here by a meandering river floodplain and channel environments.
However, according to Waksmundzka, and Waksmundzka and Żelichowski (unpublished data), a paralic
environment cannot be excluded as the depositional site of some possible carbonate rocks (recognized only in
geophysical logs), as was suggested by Żelichowski (1987).
   Rega Formation (50–170 m): the present-day distribution of the Rega Formation is limited to the area between
Trzebiatów and Kamień Pomorski (Figure 1). The Rega Formation conformably overlies the Wolin Formation; its
top, however, is erosional. Coarse-grained sandstones, often cross-stratified, dominate the major part of the
Formation (Figure 2). Shale and siltstone clasts are noted at or near the base of some sandstone beds. Thin-bedded
mudstones and claystones with plant fragments occur subordinately. The succession has also been related to a
fluvial depositional system with a meandering river channel and floodplain environments (unpublished data,
Waksmundzka, Waksmundzka and Żelichowski).
   Dziwna Formation (70–250 m): this unit is separated from the Rega Formation by an erosional gap (Żelichowski
1987), and is characterized by the presence of mudstones and claystones, with interbeds of sandstones and
conglomerates (Figure 2). The beds are characterized by a brownish colour which is in clear contrast to the Rega
Formation. Clasts of volcanic rocks, rhyolites and dacites have been observed in the sandstones (unpublished data,
Waksmundzka and Żelichowski). No sedimentological analysis has so far been presented for these deposits.
Waksmundzka (unpublished data), based only on very fragmentary core material, pointed out that the unit
comprises well-organized fining-upward cycles. This feature suggests that the origin of this unit could have been
linked, similarly, as in the case of the underlying Rega and Wolin formations, with a widely understood fluvial
environment.

            4. BIOSTRATIGRAPHY AND AGE OF THE LITHOSTRATIGRAPHICAL UNITS

4.1. The north-eastern part
Early biostratigraphic investigations of the Carboniferous deposits in the Koszalin–Chojnice area were focused on
macro- and micro-fauna (Błaszyk and Natusiewicz 1973; Korejwo 1976, 1979), as well as palynomorphs (Turnau
1978, 1979). Some opinions on the age assignments, expressed in the earliest papers, were revised later (Matyja and
Turnau 1989; Żbikowska 1992; Avchimovitch et al. 1993; Korejwo 1993; Matyja 1993, 1997; Matyja and
Stempień-Sałek 1994). Clayton and Turnau (1990) correlated the local miospore zones of Turnau (1978, 1979) with
those of Western Europe.
   More recently, there has been a significant inflow of new microfossil data on the biostratigraphy. Matyja et al.
(2000) presented and discussed the results of new conodont (Matyja) and ostracod (Żbikowska) biostratigraphic
data, whereas the miospore analysis was based here (Turnau) on the re-examination of previous sample material
interpreted earlier by Turnau (1978, 1979), Avchimovitch and Turnau (1994) and Stempień-Sałek (in Matyja and
Stempień-Sałek 1994). Because the faunal and palynological samples were collected from the same boreholes, it
was possible, for the first time in this area, to calibrate the applied conodont, ostracod and miospore zonation
schemes. Detailed conodont, miospore and ostracod analyses permitted to distinguish the following (Figure 3; see
also Matyja 1993; Matyja et al. 2000):
 (i) Five standard Tournaisian conodont zones: sandbergi (upper part), Lower crenulata, isosticha–Upper
     crenulata, Lower and Upper typicus. Unfortunately, conodonts younger than the typicus Zone have not
     been encountered in the north-eastern part of the Pomeranian area due to palaeoecological reasons.
(ii) Nine local Tournaisian and Viséan miospore zones and subzones: Convolutispora major (Ma1–Ma4),
     Prolycospora claytonii (Cl1–Cl2), Lycospora pusilla (Pu), Schulzospora campyloptera (Ca) and Dictyotri-
     letes pactilis (Pa).

Copyright # 2008 John Wiley & Sons, Ltd.                                                Geol. J. 43: 123–150 (2008)
                                                                                                    DOI: 10.1002/gj

sedimentary history of the pomeranian basin (nw poland)                                                     131

Figure 3. Mississippian chronostratigraphy and its correlation with regional stages and substages (after Davydov et al. 2004; Heckel 2004) and
‘standard’ conodont, entomozoid, and foraminiferal zones, as well as with local Pomeranian miospore zones and benthic ostracod assemblages/
                         subassemblages; identified zones/assemblages in Western Pomerania are shaded in grey.

(iii) Three Tournaisian, local benthic ostracod assemblages and two sub-assemblages: Pseudoleperditia venulosa
      (Vn1–Vn2), Cribroconcha postfoveata–Marginia tschigovae (P–T) and Glyptopleura ruegensis–Carbonita
      fabulina (R–F).
(iv) Probably the uppermost part of the entomozoid zone Richterina latior.

   Rare foraminifers characteristic of the Cf1b-g and Cf2 zones (sensu Conil et al. 1991) have also been found in
some sections (Lipiec 1999, unpublished data, Tomaś and Matyja). Revision of the biostratigraphy of the key
sections in Belgium and France (Poty et al. 2006), modify former biostratigraphic interpretations of Conil et al.
(1991). The foraminiferal Zone Cf1b-g and Zone Cf2 of Conil et al. (1991) fall in the Mississippian Foraminiferal
Zones MFZ3, MFZ 4 and MFZ5 of Poty et al. (2006; Figure 3).
   The Famennian part of the Sa˛polno Calcareous Shale Formation represented by marly limestones and marls is
dated as the Upper expansa–Lower praesulcata conodont zones (Matyja 1993). This series is overlain by anoxic
black shales, exceeding several dozen centimetres up to several metres in thickness, which show a general absence
of fossils. The black shales are overlain by series of claystones, marls and marly limestones, which corresponds to

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the upper part of the sandbergi conodont Zone at the base of the series, and the top of the Formation is dated in most
of the wells as uppermost Hastarian, isosticha–Upper crenulata conodont Zone. In some sections, however, the
range of the Formation reaches as high as the upper Tournaisian, probably into the Ivorian typicus conodont Zone
(Matyja 1993; Matyja et al. 2000, figures 18 and 19).
   The results of both conodont and miospore studies (see details in Matyja (1993), Matyja and Stempień-Sałek
(1994) and Matyja et al. (2000) suggest the presence, on a regional scale, of a stratigraphic gap within this black
shale sequence that comprises the uppermost Famennian (Middle and Upper praesulcata conodont zones) and the
lowermost Hastarian (the sulcata, duplicata, and the lower part of the sandbergi conodont zones; Figure 3). A
similar stratigraphic gap is also indicated by the miospore data, as the equivalents of the western European
miospore zones lepidophyta–explanatus (LE), lepidophyta–nitidus (LN), and verrucosus–incohatus (VI) Zone are
missing. The presence of the goniatite Pseudoarietites dorsoplanus dorsoplanus Schmidt (¼Paprothites
dorsoplanus (Schmidt) in the Grzybowo-1 and Wierzchowo-10 wells (Korejwo 1993; see also Matyja et al. 2000,
figure 18), which is the index taxon for the Paprothites dorsoplanus Zone correlated with the Upper duplicata
conodont Zone (Korn 2006), suggest that the gap could be smaller and limited to the Middle–Upper praesulcata
zones and probably to the Carboniferous sulcata and Lower duplicata zones.
   Apart from the question of the range of the gap, it is clear, however, that the uppermost Famennian–lowermost
Tournaisian deposits show extremely reduced thicknesses, not exceeding several metres (Matyja et al. 2000,
figures 18 and 19).
   The Trzebiechowo Marl Formation is known only from the south-eastern part of the area. The oldest part of the
Trzebiechowo Marl Formation corresponds to the uppermost part of lower Tournaisian (sandbergi conodont Zone),
and the top of the Formation—to the upper Tournaisian (probably typicus conodont Zone) (Matyja et al. 2000,
figure 18). The Formation is roughly the time equivalent of the Carboniferous part of the Sa˛polno Calcareous Shale,
Gozd Arkose Sandstone, Kurowo Oolite and Grzybowo Calcareous Shale formations (Figure 2).
   Over the entire Koszalin–Chojnice area, except for its south-easternmost part, the limestones and shales of the
Sa˛polno Calcareous Shale Formation are overlain by coarse-grained volcaniclastic sediments of the Gozd Arkose
Formation. The lower part of the Formation belongs to the Lower crenulata conodont Zone (¼lower part of
the middle Tournaisian) and the Formation reaches as high as the Lower typicus conodont Zone (¼upper part of the
middle and lower part of the upper Tournaisian (Matyja et al. 2000, figure 18).
   The Kurowo Oolite Formation corresponds to the upper Tournaisian, to the typicus conodont Zone (Matyja et al.
2000).
   The Grzybowo Calcareous Shale Formation corresponds to the upper Tournaisian, to the typicus conodont Zone.
The Kurowo Oolite Formation and the Grzybowo Calcareous Shale Formation are roughly time equivalents
(Matyja et al. 2000).
   The Drzewiany Quartz Sandstone Formation was deposited on the oolite limestones of the Kurowo Formation
and calcareous claystones of the Grzybowo Formation. Significant microfauna is lacking in the Formation. Only in
the Ustronie IG-1 well section has the presence of abundant and low diversity ostracod assemblage been noted, that
are, Paraparchites rarus Tschigova, Paraparchites nicklesi (Ulrich), Glyptolichwinella spiralis (Jones and Kirkby),
Glyptopleura minima Gorak, Cavellina insignita Gorak, Tulenia indubia Tschigova, Joungiella sp. and
?Kloedenella sp. (Woszczyńska in Żelichowski et al. 1986). Żbikowska (unpublished data, see Turnau et al. 2005)
determined also several representatives of an ostracod fauna, that are, Glyptopleura ruegensis Blumenstengel,
Sansabella sp., Cavellina sp. and Chamishaella sp., and concluded that the fauna is Tournaisian or lower Viséan. In
most sections, the preserved part of the Formation represents the uppermost Tournaisian (upper part of the
Ivorian ¼ Upper Prolycospora claytonii local miospore Zone) and lower or locally middle Viséan (Chadian,
Arundian and Holkerian ¼ Lycospora pusilla local miospore Zone) (Turnau in Matyja et al. 2000). Only in one case
(Sarbinowo-1 well) the lower part of the upper Viséan (Asbian ¼ Schulzospora campyloptera (Ca) and
Dictyotriletes pactilis (Pa) local miospore zones) has been identified (Turnau in Matyja et al. 2000). The base of the
local Dictyotriletes pactilis Zone is considered as not older than the upper part of the western European
Schulzospora campyloptera–Perotriletes tessellatus (TC) Zone, and the base of the western European Tripartites
vetustus–Rotaspora fracta (VF) Zone (see Somerville 2008, figure 1; Figure 3) corresponds to a level within the Pa

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local Zone (Turnau in Matyja et al. 2000, figure 9). Korejwo (1993) noted the presence of Goniatites crenistria
Phillips and Prolecanites cf. serpentinus (Phillips) from some storm-layers in the Sarbinowo-1 well (see also
Matyja et al. 2000, figure 19). The first species is the index taxon for the Goniatites crenistria Zone (see Korn 2006,
figure 1), which corresponds to a level within the Asbian (Somerville 2008, figure 1). Thus, the Drzewiany Quartz
Sandstone Formation spans the uppermost Tournaisian (uppermost Ivorian) and much of the Viséan, including
Chadian, Arundian, Holkerian and the lower part of the Asbian (Figures 2 and 3). However, the top of the
Drzewiany Quartz Sandstone Formation is marked in all wells by an unconformity (Figure 2).

4.2. The south-western part
It is rather difficult to determine precisely the age of particular lithostratigraphic units in the Laska–Czaplinek
Zone, and particularly, the mutual spatial relationships in the uppermost Tournaisian and Viséan between the
deposits of this area and the north-eastern region.
   Data on the biostratigraphy of the Łobżonka Shale Formation is sparse. The presence of rare foraminifers in the
lower part of the Formation, including Endothyra sp., Palaeotextularia sp. and Parathurammina suleimanovi
Lipina (Soboń-Podgórska 1982) and Forschiella cf. prisca Mikhailov, Eoparastaffella simplex (Vdovenko),
Endothyra phrissa (Zeller), Pseudolituotubella sp., and Tetrataxis sp. (Lipiec 1999), suggests a stratigraphical
position not below the Cf3 Zone of Conil et al. (1991) and MFZ6 of Poty et al. (2006), but at the same time not
above the lower Viséan (Lipiec 1999). Żelichowski (1987) found here a fragment of ?Pericyclus sp. Recent results
of miospore analysis (Turnau et al. 2005) suggest that the known, penetrated part of the Formation can be assigned
probably to the lowermost part of the Lycospora pusilla local miospore Zone (Turnau in Matyja et al. 2000, figure
9), which is correlated with part of the Lycospora pusilla (Pu) Zone of Clayton et al. (1977). Based on these data,
and taking into account the biostratigraphic results coming from the horizon above (the Czaplinek Limestone
Formation), it might be suggested that the known part of the Łobżonka Shale Formation should be referred to the
?uppermost Ivorian, and to the Chadian–?lowermost Arundian (Figures 2 and 3).
   Czaplinek Limestone Formation: relatively rich foraminifers were found in some sections, where they characterize
Eoparastaffella (Cf4g-d), Koskinotextularia–Pojarkovella nibelis (Cf5) and Neoarchaediscus (Cf6a-b)
foraminiferal zones and subzones of Conil et al. (1991) (Lipiec 1999). The co-occurrence of Eostaffella,
Eoparastaffella, Archaediscus (involutus stage), Uralodiscus, Planoarchaediscus, Glomodiscus in the Czaplinek
IG-1 section points to the Arundian, Cf4g-d subzones; the presence of Lituotubella and the lack of younger taxa in
the Piaski PIG-2 well point to the Holkerian, Cf5 Zone; in the Moracz IG-1 section, the Cf5 Zone can be
distinguished based on the presence of Endothyra phrissa, and the subzones Cf6a-b (lower part of the Asbian)—
based on the presence of Archaediscus (angulatus stage) and Endothyra spira and the lack of younger taxa (Lipiec,
1999). The foraminiferal sub-zones Cf4g-d, Zone Cf5 and Cf6a-b subzones of Conil et al. (1991) fall in zones MFZ
11, MFZ 12 and MFZ13 of Poty et al. (2006). The Czaplinek Limestone Formation should be referred to the
Arundian, Holkerian and part of the Asbian (Figures 2 and 3).
   Nadarzyce Shale Formation: biostratigraphic data from this unit are sparse and equivocal. Lipiec (1999) found
here only some representatives of the foraminifer genus Tetrataxis. Żelichowski (1987) suggested that the
Nadarzyce Shale Formation should be referred to the upper Viséan–lower Namurian, taking into account the
presence of rare foraminifers e.g. Endothyra sp. encountered in the basal parts of the Formation by
Soboń-Podgórska (1982), and miospores which were of Namurian age in the opinion of Górecka et al. (1982) and
Górecka and Parka (1987). Unfortunately, this miospore assemblage is dominated by long-lived species and genera.
There are no representatives of the genus Tripartites and the species Reticulatisporites carnosus (Knox) Neves, as
well as Bellisporites nitidus (Horst) Sullivan, that are stratigraphically important taxa for the Brigantian and
Pendleian (¼VF and NC miospores zones of Clayton et al. 1977). Taking into account the biostratigraphic results
coming from the horizon below (the Czaplinek Limestone Formation), it might be only suggested a stratigraphical
position not below the upper Asbian for the base of the Nadarzyce Shale Formation (Figures 2 and 3). The top of the

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Formation is marked by an unconformity. This equivocal biostratigraphical data suggests that a verification of the
age of the Formation is urgently needed.
   The top of the Viséan (part of the Drzewiany and Nadarzyce formations) is marked in all wells by an
unconformity. Locally, the Viséan sediments, and often also older deposits, have been removed by post-Viséan
uplift and erosion, which probably occurred during the Serpukhovian and in the beginning of the Bashkirian (see
Figure 2). Dating of the lithostratigraphic units of the Pennsylvanian is equivocal in the geological literature
(cf. Dybova-Jachowicz and Pokorski 1984; Kmiecik 1995, 1997), hence the temporal relationships between these
units presented here may be affected by a significant error.
   The Wolin Formation spans the ?uppermost part of the Westphalian A, Westphalian B and maybe also the
lowermost part of the Westphalian C (Bashkirian–lower Moscovian?) and represents the uppermost part of the
Radiizonates aligerens (RA) Zone and the Microreticulatisporites nobilis–Florinites junior (NJ) Zone (Kmiecik
1995; see also Figure 4).
   The Rega Formation spans the Westphalian C and D and probably part of the Stephanian (Moscovian–lower
Kasimovian?) and represents the Torispora securis–Torispora laevigata (SL) Zone, Thymospora obscura–
Thymospora thiessenii (OT) Zone and possibly also the Angulisporites splendidus–Lycospora trileta (ST) Zone
(Kmiecik 1995; see also Figure 4).
   The precise stratigraphic range of the Dziwna Formation is doubtful, owing to the scarcity of material. A sparse
miospore assemblage, representing probably part of the Thymospora obscura–Thymospora thiessenii (OT) Zone,
as well as the Angulisporites splendidus–Lycospora trileta (ST) and Prolycospora novicus–Prolycospora

Figure 4. Pennsylvanian chronostratigraphy and its correlation with regional stages and substages (Davydov et al. 2004; Heckel 2004) and
                             miospore zonation; identified zones in Western Pomerania are shaded in grey.

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sedimentary history of the pomeranian basin (nw poland) 135

bharadwaji–Crassispora major (NBM) zones, has been assigned to the Stephanian-Autunian (Kasimovian–
Gzhelian?) (Kmiecik 1995; see also Figure 4).

5. EVOLUTION OF DEPOSITIONAL ENVIRONMENTS

According to the palaeoclimatic reconstruction by Witzke and Heckel (1988) and Witzke (1990) northern Europe,
as part of the Laurussia continent, was located during the Mississippian times in the vicinity of the southern
palaeotropic (10–208S). The widespread occurrence of evaporites and marine oolites provide proof for such a
setting (see Bless et al. 1984; Witzke 1990, figures 6 and 7).
The major palaeogeographic elements that affected the Devonian and Early Carboniferous sedimentary
evolution of the Pomeranian Basin were land areas representing uplifted parts of the East European Craton: the
Fennoscandian High extending in the north, outside the territory of Poland, and the Mazury–Belarus High, situated
in the east (Ziegler 1990; see also Figure 1). The sedimentary evolution and lithofacies pattern in the Devonian and
Mississippian Pomeranian Basin followed these main structural outlines and was generally associated with a
gradual northward and eastward expansion of the marine basin, towards the East European Craton. The TTZ and its
transverse segmentation also played an important role in the lithofacies distribution. Basing on repeated conformity
of the position of lithofacies belts or sedimentary environments, as well as zones of great thickness gradient, the
existence of N–S and W–E-trending synsedimentary faults in the basement of the upper Palaeozoic cover has been
suggested (Dadlez 1978, 2006; see also Matyja et al. 1995), whereas the evidence was supplied by Świdrowska and
Hakenberg (1996).
The reconstruction of the Mississippian evolution of depositional environments was possible due to studies
performed by Matyja et al. (1995) Lipiec (1997, 1999), Matyja (1997), Lipiec and Matyja (1998) and Matyja
(2006). As a result of the detailed biostratigraphic investigations of Turnau (1978, 1979), Lipiec (1999) and Matyja
et al. (2000), it has been possible to illustrate several successive Early Carboniferous evolutionary stages of the
Pomeranian Basin, although most of the geological data used in the spatial and temporal reconstructions of the
facies and sedimentary environment pattern originates mainly from a relatively narrow belt of deposits extending
NW–SE between Koszalin–Kołobrzeg–Kamień Pomorski and Toruń–Bydgoszcz (see Figures 1, 5–8 and 10–12).
Due to the scarcity of analytical data for the Pennsylvanian period (cf. Żelichowski 1983, 1987, 1995 and
unpublished data of Waksmundzka and Żelichowski), the Late Carboniferous history is much more difficult to
reconstruct.
Phases of deposition, non-deposition, erosion and uplift were interpreted from the distribution of the
stratigraphic units, the presence of regional and local unconformities, and the reconstruction of depositional
environments. The results are presented below following the recent Carboniferous (Figures 3 and 4) stratigraphic
schemes (Heckel 2004; see also Davydov et al. 2004 and Menning et al. 2006).
The lateral relationships of the lithofacies during the latest Famennian, Tournaisian and Viséan are portrayed on
several maps (Figures 5–8 and 10–12), showing relatively short time-intervals, selected to depict the most
significant environmental changes, which were controlled mainly by relative sea-level changes caused by tectonic
mobility of the hinterland area and the basin floor, as well as by volcanic activity on the nearby land.

5.1. Late Famennian–Hastarian (Late expansa–?early sandbergi chrons): outer ramp phase of sedimentation
(Figures 5 and 6)
At the end of the Devonian, beginning with the Late expansa Chron, a subtidal environment became prevalent over
the whole Pomeranian area. It later persisted up to the early Tournaisian. Two lithofacies types have been
recognized to represent this interval: fossiliferous marly limestones in the shallower part of the basin to the north
and fossiliferous marls with interbeds of organodetrital limestones in the deeper part of the basin to the south
(Figure 5).

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Figure 5. Lithofacies pattern for the late Famennian (Late expansa–Early praesulcata conodont chrons) in Western Pomerania. Key as for
                                                                Figure 2.

  However, in the ?Middle praesulcata Chron, anoxic conditions developed over the entire basin or much of its
area, which persisted up to the Hastarian, to the ?early sandbergi conodont Chron (see Section 4—‘Biostratigraphy
and age of the lithostratigraphical units’). These uppermost Famennian–lowermost Tournaisian black clayey
deposits (Figure 6) are reduced to several dozen centimetres (minimum) up to several metres (maximum) in

Figure 6. Lithofacies pattern for the late Famennian–Hastarian (Middle praesulcata–?early sandbergi conodont chrons) in Western Pomerania.
                                                            Key as for Figure 2.

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sedimentary history of the pomeranian basin (nw poland) 137

thickness. The only physical manifestation of some sedimentological disturbances within the monotonous and
practically unfossiliferous shale deposits of almost pelagic nature is the presence of pyrite, as well as the occurrence
of rich organic matter. No surface with peculiar microrelief, which might be evidence of corrosion, have been
found. Moreover, there is no evidence of any pre-sandbergi abrasion affecting the Famennian and Tournaisian
deposits observed in some sections in southern Poland (Szulczewski 1973, 1978; Bełka 1985). Presumably, this
stratigraphic gap resulted from some chemical or hydrodynamical factors rather than from any tectonic uplift.
It was probably a submarine nondeposition gap which was an effect of a strong decrease or even cessation of
lime-mud production for a long time. If this is the case, however, the absence of conodonts of two Devonian and two
Carboniferous zones (see ‘Biostratigraphy and age of the lithostratigraphical units’ section; Figure 3) is hard to
explain. One would expect, rather, an increased abundance of conodonts as a consequence of the low accumulation
rate. One explanation is that conodonts and other faunal remains could have been mechanically washed out, or,
which is more probable, unfavourable changes in water chemistry and/or water stratification might have led to a
long-term stress and retreat of all faunal groups from the Pomeranian sedimentary basin.
The beginning of the observed event in the Pomeranian Basin (Middle praesulcata Chron) most probably
coincides with the anoxic black shale event which affected many places worldwide, known as the late Famennian
Hangenberg Event (House 1985, 2002), which was probably responsible for a decline and extinction of many
faunal groups at the end of the Devonian. It is noteworthy, however, that anoxic conditions persisted in the
Pomeranian Basin up to the Hastarian (to the ?early sandbergi conodont Chron), that is, a much longer interval than
is suggested for the Hangenberg Event. The attention was drawn to the fact, however, that much of the events may
have a complex history and are phased (Barnes et al. 1996; Walliser 1996; House 2002). Thus, it is questionable
whether the recognized event in the Pomeranian Basin was only connected with the Hangenberg Event, which
possibly was more complex and multi-phased as is suggested, or it was a serious of regionally limited,
post-Hangenberg events. It seems that more high-resolution data is required for this event, like magnetosuscept-
ibility and geochemical signatures.

5.2. Hastarian (late sandbergi–isosticha–Late crenulata chrons): outer/middle/ramp phase of
sedimentation (Figure 7); volcanic activity on the nearby land
At the end of the early Tournaisian (end of sandbergi conodont Chron) and during the middle Tournaisian, the
northern part of the area was dominated by marl and limestone lithofacies, whereas to the south, marly claystone
lithofacies developed, indicating environments related to a carbonate ramp. A narrow belt of relatively
shallow-marine carbonate sedimentation developed in the south-eastern part of the basin, close to the vicinity of the
Brda and Wierzchowo boreholes (Figure 7).
A new, additional source area of siliciclastic material for the Pomeranian Basin appeared in the middle
Tournaisian. It was accompanied by increased tectonic and volcanic activity on the nearby land (the uplifted East
European Craton). Through the entire middle and much of the late Tournaisian, eroded lava sheets, as well as
pyroclastic volcanic material were the source of large amounts of detrital material transported probably through
immature river and deltaic systems to the south-west?, to the marine basin (see Figure 7), and deposited as arkosic
sandstones (the Gozd Arkose Formation). An increased input of terrigenous (volcaniclastic) material, irregularly
distributed within the marine basin, probably triggered off some development of shoals on the sea bottom and
caused with time the gradual shallowing of the sedimentary environment. The observed sedimentary structures
within the succession reflect the shallowing-upward trend.

5.3. Ivorian (typicus–?early anchoralis-latus chrons): the rimmed carbonate shelf phase of
sedimentation (Figure 8); volcanic activity on the nearby land
The next stage of the basin evolution is marked by the development of a high-energy shallow-water shoal/barrier,
composed of arkosic (volcaniclastic) sandstones (the deposits of the Gozd Arkose Formation) and ooid grainstones
(the deposits of the Kurowo Oolite Formation), which created the rimmed shelf depositional system. This barrier/
shoal system extends as far south as the Wierzchowo–Brda line (see Figure 8), and separated the back-barrier

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Figure 7. Lithofacies pattern for the Hastarian (sandbergi–isosticha–Late crenulata conodont chrons) in Western Pomerania. Key as for
                                                                 Figure 2.

lagoonal environment in the north and north-east (the deposits of the Grzybowo Calcareous Shale Formation) from
a relatively shallow, but open-marine environment, extending to the south (the deposits of the Trzebiechowo Marl
Formation).
   Behind the barrier/shoal system, a very characteristic microfacies of lime mudstones with ostracods, thin-shelled
bivalves and gastropods, microbial laminites, oolitic and peloid packstones and grainstones, and calcisphere

Figure 8. Lithofacies pattern for the Ivorian (typicus–?early anchoralis-latus conodont chrons) in Western Pomerania. Key as for Figure 2.

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sedimentary history of the pomeranian basin (nw poland) 139

wackestones have been recognized. Rare conodonts and miospores have also been noted. Small encrusting
tube-like fossils, formerly assigned to ‘vermetid gastropods’, now included within a separate molluscan group—
the Microconchida (see Flügel 2004) were found within microbial laminites. Erect and gregarious forms of
microconchids were frame-builders in peritidal schizohaline lagoonal settings (Burchette and Riding 1977). Thin
beds of primary or early diagenetic dolomite and anhydrite (Muszyński 1976, 1979), as well as nodules of anhydrite
have been noted. Low-diversity biota, the presence of fine-grained sediments and evaporites point to a protected and
restricted lagoonal environment behind barrier/shoal. Thus, the Grzybowo Calcareous Shale Formation reflects
also the rimmed carbonate shelf phase of sedimentation.
The presence of evaporites and marine oolites points to an semi-arid or arid palaeoclimate during the late
Tournaisian (late Ivorian) time, which is in agreement with known palaeogeographical and palaeoclimatical
reconstruction for this part of Europe (see Witzke and Heckel 1988; Witzke 1990; Ziegler 1990, figure 14; Gursky
2006, figures 2 and 3a). Courceyan evaporites as thick sequences of dolomite and anhydrite (the Middleton Dale
Anhydrite and the Hathern Anhydrite Series) have been described from shallow-marine carbonate sequences in
the East Midlands (UK) (Strank 1987). Hypersaline lagoon environment with ubiquitous evidence for evaporites
were recognized in the early Courceyan succession in South Wales and western England (Burchette 1987). Late
Tournaisian carbonates and evaporites were also deposited in the Wexford Basin in south-eastern Ireland (Nagy
et al. 2005b).
Volcaniclastic sediments were initially (late Hastarian) deposited in the sedimentary environments of a relatively
deeper shelf (Figure 7). During the Ivorian the deposition occurred also within the inner shelf and in near-shore
environments (Figure 8). It is certain that the volcanism was characterized by homogeneity and relative stability,
and the material must have been derived from domes and surface lava flows of alkali rhyolite and trachyte
composition, and that the transport distance of the eroded material was short (Muszyński et al. 1996).
The arkose sandstone series in the Pomeranian Basin shows systematic changes in bed thickness and coarseness
of volcaniclastic material across the basin. Near the TTZ (between Niekłonice, Dygowo, Biesiekierz, Żeleźno,
Kłanino, Gozd, Grzybnica and Chmielno—see Figure 1), thick beds and a coarse-grained fraction are found in the
succession. These thin out and become finer rapidly towards the SW, to the centre of the basin (cf. Figures 7 and 8).
Thus, it seems that the source of volcaniclastic material should be located farther to the north-east or to the east of
the present-day extent of the Gozd Arkose Formation (Figure 9). Unfortunately, to the north-east of the investigated
area, among the wells which penetrated the crystalline basement there is no evidence of intrusive rocks (Figure 9—
Słupsk IG-1, Żarnowiec IG-1, Hel IG-1, Gdańsk IG-1 boreholes).
Three mafic-alkaline intrusive bodies located at the EEC (in NE Poland), Tajno, Ełk, and Pisz (Figure 9), have
been dated recently with the U-Pb SHRIMP method. The obtained U-Pb results of 333.0 18 Ma (Tajno), 347.7
7 Ma (Ełk) and 345.5 5 Ma (Pisz) have shown a consistent Early Carboniferous age (see Menning et al. 2006) of
platform mafic–alkaline magmatic activity (Krzemińska et al. 2006). Unfortunately, they could not be regarded as a
source area for the Gozd Arkose Formation, because of important differences in petrographical and geochemical
characteristic between all intrusive bodies and the Formation (Personal communication, Krzemińska, 2007).
The Mława microsyenite intrusive body, which was penetrated by the Gradzanowo-2, Konopki Wielkie-1 and
Ciechanów boreholes (Figure 9) could be possibly regarded as a source area. The K-Ar method pointed to a Late
Palaeozoic age of the microsyenites (Konopki Wielkie 1–305.0 Ma, Ciechanów 1– 295 Ma) (Kubicki and Ryka
1982). Unfortunately, there is no new geochronolgical results to discuss the problem of the closure temperatures for
different minerals and different isotopic systems used in previous age determinations of the Mława intrusive body.
In summary, therefore, where was the location for the intracratonic source of volcaniclastic material deposited as
the Gozd Arkose Formation? Unfortunately, it is still an open question!

5.4. Late Ivorian–?early Arundian: siliciclastic, marginal marine (north-eastern part) and delta front
(south-western part) phase of sedimentation (Figure 10)
In the late Ivorian (?end of the anchoralis-latus conodont Chron), the volcanic activity ceased. Mature fine-grained
quartz sandstones and siltstones were deposited at that time in the north-eastern part of the area, indicating

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