Trace fossils from the Lower Ciechocinek Formation, SW 89

Trace fossils from the Lower Jurassic Ciechocinek F ormation, SW Poland

Paulina LEONOWICZ

Institute of Geology, University of Warsaw, ul. ˚wirki i Wigury 93, PL-02089 Warszawa, Poland; e-mail: [email protected]

Key -words: trace fossils, fine-grained clastics, brackish environment, Lower Jurassic, Cz´stochowa-Wieluƒ region.

ABSTRACT: -silt deposits of the Lower Jurassic Ciechocinek Formation from the Cz´stochowa-Wieluƒ region are characterized by a low diversity ichnofossil association, which includes the ichnogenera , Palaeophycus , Helminthopsis , Gyrochorte , Protovirgularia and Spongeliomorpha as well as some unidentified pascichnia. This association points to deposition in a low-energy brackish environment with poorly oxygenated sediments. Changes of seafloor oxygenation, influenced by periodical bottom currents, resulted in various bioturbation intensities, which range from none to high.

INTRODUCTION and Leonowicz 2002) and geochemical study of siderites (Leonowicz 2007). In the absence of body During the the territory of Poland fossils, trace fossils are the most useful tool in was situated in a marginal part of the extensive, environmental interpretations. They are quite epicontinental Central European Basin (Fig. 1: A), common in the Ciechocinek Formation and include which was particularly sensitive to sea-level Diplocraterion parallelum Torell as well as fluctuations, causing frequent displacements of the some other non-identified fodinichnia, repichnia, shoreline and changes of sedimentary environment. domichnia and cubichnia (Pieƒkowski 1988, 2004). The Ciechocinek Formation marks the maximum However, more detailed analysis of the ichnofossil extent of marine sedimentation in Poland, related association was not carried out till now. by Dadlez (1969) and Pieƒkowski (2004) to the The purpose of this paper is to analyse the trace Early transgression, which is recorded in fossil association from the Ciechocinek Formation the whole Central European Sea. Fauna in these deposits in the Cz´stochowa – Wielu ƒ region deposits is uncommon and of low diversity. It (Fig. 1: B) in order to determine bottom conditions includes phyllopods, , scarce foraminifers in the sedimentary basin. Observations of the type and occasional fragments of bivalves, gastropods and distribution of trace fossils were made in and fish teeth (Kopik and Marcinkiewicz 1997; successions cropping out in two -pits, which Kopik 1998). The lack of typical marine fauna belong to the “Cerpol-Koz∏owice” Enterprise and indicates that the transgression did not cause the “Boroszów” Brickyard, as well as during development of normal-marine conditions in the examination of cores from 16 boreholes drilled by Polish Basin. Such a conclusion is also confirmed by the Polish Geological Institute. Fresh, unpolished analysis of the dinoflagellate assemblage (Barski surfaces of rocks were observed. In order to reco- 90 Volumina Jurassica, Volumen VI

B A WIERUSZÓW

WIELU¡

0 500 km 36 1 12 inferred maximum range PRASZKA of the Lower Jurassic deposits location of the studied area 41 Upper Jurassic 40 16 Kozłowice 49 15 KRZEPICE Middle Jurassic KLUCZBORK Boroszów 50 KŁOBUCK Lower Jurassic 2 Przystajƒ OLESNO 21 20 46 45 3 outcrops 25 boreholes CZ¢STOCHOWA profiles presented 0 10 20 km on Fig. 4

Fig. 1. Location of the studied area : A – Polish Basin as a part of the Central European Basin in the Early Jurassic time (after Pieƒkowski 2004); B – location of studied profiles on a geological sketch-map of the Cz´stochowa-Wieluƒ region. gnize the fabric of massive deposits, thin sections, gellate cysts, the deposits of the Ciechocinek made from well consolidated and Formation were dated to the Margaritatus – , were examined under the microscope. Tenuicostatum zones (Barski and Leonowicz 2002). Pieƒkowski (2004) placed it within the Lower Toarcian, on the basis of sequence stratigraphy GEOLOGICAL SETTING correlation and the results of macrospore analysis by Marcinkiewicz (1957, 1960, 1964, 1971). He noted The Ciechocinek Formation represents a mud- there one find of Diplocraterion (Nowa WieÊ 12 silt succession (Fig. 2) consisting of poorly borehole) and some, locally common, non-identified consolidated, grey, olive and willow-green mud- trace fossils of fodinichnia and repichnia. stones and siltstones with lenses and subordinate intercalations of and (Teofilak- Maliszewska 1967, 1968; Leonowicz 2005). Up to several centimeter thick lenses and intercalations of siderite as well as small siderite and pyrite concretions are common. In all types of deposits fine plant detritus as well as larger, several centimeter long wood fragments occur. In the area studied the Ciechocinek Formation overlies -mud deposits of the Blanowice Formation and is overlain by the similarly developed Borucice Formation (Fig. 3), both of alluvial and lacustrine origin (Pieƒkowski 2004). Depending on the section, boundaries between 5 cm formations are distinct, confined by erosional Fig. 2. Deposits of the Ciechocinek Formation from the Koz∏owice surfaces or gradual, marking continuous changes clay-pit: intercalations of massive , lenticular-bedded muds and of sedimentary environment. Based on dinofla- interlaid mud-sand heteroliths. Trace fossils from the Lower Jurassic Ciechocinek Formation, SW Poland 91

ICHNOLOGY OF THE CIECHOCINEK FORMATION Palaeophycus is less common than Planolites in deposits of the Ciechocinek Formation; however, Trace fossil association is not diverse and in the Koz∏owice outcrop numerous specimens includes Planolites , Palaeophycus , Helmintho- occur. It is interpreted as the result of passive filling psis , Gyrochorte , Protovirgularia and Spon- of burrows (Pemberton and Frey 1982). geliomorpha as well as many small, undetermined It is a facies-crossing, eurybathic form, known from trace fossils, most probably of the pascichnia deep-marine flysch and brackish-marine deposits category. Trace fossils are preserved in mud-silt as well as from the fresh-water environments deposits as endichnia and in lenses as hypichnia. Thicker, poorly consolidated sandy Chrono- layers are devoid of bioturbational structures. Lithostratigraphy stratigraphy Wr´czyca 3 c i e

l Lower s d Planolites isp. (Fig. 5: A-F) s [m] a d KoÊcielisko Beds i r u

M J DESCRIPTION : Unlined and unbranched, r

e Połomia Borucice

straight, curved or tortuous trace fossils, p

p Beds Formation cylindrical or elliptical in cross-section, usually U n a from fraction to 2 mm in diameter, variably oriented i c r to the bedding. Less common are thicker forms, a o r T reaching up to 7 mm in diameter, usually horizontal e Ciechocinek w

o Formation or subhorizontal and gently curved. Filling of L burrows is structureless, differing in grain size and/or colour from the host rock, locally pyritized. r

Planolites is preserved as full relief in mud-silt e p n p a i deposits or on sole surfaces of sandstones. U c h i c s REMARKS: The size and curvature suggest that a Blanowice s

b 100

a Formation s r most of the specimens observed should be assigned n r u e e i J l to Planolites montanus Richter (Fig. 5: C, D, F). w P r o L Larger forms may belong to Planolites e w beverleyensis Billings (Fig. 5: E). Planolites is o L r e

common in all types of the Ciechocinek Formation n p a

p ? i r deposit. It is referred to vermiform deposit-feeders, U Zagaje Fm. u mainly , producing active backfilling m e r e n i

(Pemberton and Frey 1982). Planolites is a facies- w S o crossing, eurybathic form, known from shallow L hiatus

marine and deep-marine flysch deposits as well as r e p n

e.g. p from fresh-water environments ( Ksià˝kiewicz a i U g

1977; Pieƒkowski 1985; Bjerstedt 1987; Beynon and n ? a t

r Zagaje Fm. t

Pemberton 1992; Pemberton and Wightman 1992; e e w H

Buatois and Mángano 1998; Fürsich 1998). o L c i

Palaeophycus isp. (Fig. 5: G) s 150 s Rhaetian Wielichowo Beds a

i m sf

r st sm DESCRIPTION : Straight or gently curved, T thin intercalations predominantly horizontally oriented, unbranched, gravel smooth or rarely faintly ornamented cylindrical of silt (-stone) and mud (-stone) trace fossils up to 10 mm in diameter, slightly sand (-stone) flattened in cross-section. Filling structureless, silt (-stone) grain size: m - mud, m sf st - silt, s - sand st sm of the same lithology as the host rock. Preserved mud (-stone) (f - fine, m - medium) on sole surfaces of sandstones. REMARKS: The lack of thick lining and distinct Fig. 3. Lithostratigraphy of the Lower Jurassic in the Cracow-Silesian region (after Kopik 1998; Pieƒkowski 2004; Deczkowski and Daniec ornamentation suggests that most of the specimens 1981) and the representative lithological profile of the borehole observed represent Palaeophycus tubularis Hall. Wr´czyca 3 (after Leonowicz 2007). 92 Volumina Jurassica, Volumen VI

priapulids. Helminthopsis is a facies- Planolites Nowa WieÊ 12 crossing, eurybathic form, known from Palaeophycus [m] 0 Helminthopsis deep-marine flysch to brackish-marine n o i

t Gyrochorte deposits as well as from the fresh-water a

m Protovirgularia environments ( e.g. Ksià˝kiewicz 1977; r o F

Spongeliomorpha Bjerstedt 1987; Beynon and Pemberton e c i Diplocraterion c 1992; Buatois and Mángano 1998). u

r data after Pieƒkowski o

B (2004) Gyrochorte isp. (Fig. 6: E, F)

Kozłowice DESCRIPTION : Winding, horizontal, [m] 0 double ridge separated by a median groove. The surface of ridges is smooth

n or has an indistinct, plaited structure, o i

t 50

a composed of biserially arranged, m r obliquely aligned pads of sediment. o 20 F

k The ridges are curved or gently e n

i ?

c meandering; they do not branch and o h

c often cross themselves. The width e i

C of trace fossils changes along their axis

m s and generally does not exceed 4 mm. Gyrochorte is preserved as epirelief in gravel and sandstones and mudstones. rock fragments REMARKS: Only single specimens sand (-stones) were observed in the Koz∏owice outcrop . silt (-stones) m

F and Nowa WieÊ 12 borehole. Gyrochorte

and mud (-stones) e

c 100 i is interpreted as a result of active lenticular bedding w

o digging in sediment of deposit-feeding n a l wavy bedding

B worm-like animal, probably an annelid grain size: m - mud, (Heinberg 1973; Gibert and Benner m st s m st s st - silt, s - sand 2002). The trace maker was probably an Fig. 4. Distribution of trace fossils in two representative sections of the Ciecho - opportunistic animal, colonizing newly cinek F m. S implified lithostratigraphical division is marked, in which the Ciechocinek deposited storm sediment. Gyrochorte Fm. includes deposits originated in transitional marine/continental environments. is known from nearshore and shallow marine environments, marking a broad (e.g. Ksià˝kiewicz 1977; Pieƒkowski 1985; Bjerstedt range of environmental conditions from hyper- 1987; Beynon and Pemberton 1992; Pemberton and saline to hyposaline ( e.g. Hallam 1970; Heinberg Wightman 1992; Buatois and Mángano 1998). 1973; Heinberg and Birkelund 1984; Fürsich 1998; Gibert and Benner 2002). Helminthopsis isp. (Fig. 6: A, B) Protovirgularia isp. (Fig. 6: C) DESCRIPTION : Simple, unbranched, horizontal cylinders, 2 mm in diameter, slightly flattened in DESCRIPTION : Small, straight, horizontal, cross-section, sinuous or irregularly meandering. bilobate trace fossil, about 3 mm wide, comprising Filling is structureless and of the same lithology two symmetric, obliquely striated belts separated as the host rock. They occur on sole surfaces of by an indistinct median ridge. Preserved on sole sandstones or on parting planes in muds. surface of a small sandstone lens. REMARKS: Only a few specimens were obser- REMARKS: Only one specimen was found in ved in the Koz∏owice outcrop. It is interpreted as the Koz∏owice outcrop. Protovirgularia is a a grazing trail (Pemberton et al. 2001) or feeding repichnion form, ascribed to the activity of bivalves, burrow (Wetzel and Bromley 1996), produced at which crawled by the rhythmic action of a foot shallow depth in sediment by polychaetes and (Seilacher and Seilacher 1994). It is known from Trace fossils from the Lower Jurassic Ciechocinek Formation, SW Poland 93

A B C

1 cm

D

1 mm 1 mm 1 cm E F G

1 cm 1 cm 1 cm

Fig. 5. Trace fossils from the Ciechocinek Formation : A-F – Planolites : A – small tunnel filled with a coarser material in a sideritic silty , microphotograph, crossed nicols; B – small tunnel filled with a darker material in a sideritic mudstone, microphotograph, one nicol; C – Planolites montanus preserved on a sole surface of sandstone lens; D – tunnels of Planolites montanus filled with a darker material in a massive ; E – Planolites beverleyensis filled with fine-grained sandstone and preserved as endichnia in a mud; F – cross-section of thin Planolites montanus filled with a light grey, fine sand; G – Palaeophycus tubularis (arrows) preserved on a sole surface of sandstone lens. A-C, E, G – Koz∏owice outcrop; D – Wichrów 50 borehole; F – Przystajƒ 25 borehole. both marine and fresh-water deposits ( e.g. Goldring REMARKS: Spongeliomorpha was found only et al. 2005; Uchman 1998). in the Koz∏owice outcrop, in the lower part of the succession, where it occurs in two highly Spongeliomorpha isp. (Fig. 6: D, G, H) bioturbated horizons (Fig. 6: D), each of them a few centimetres thick. Spongeliomorpha is interpre- DESCRIPTION : Horizontal and subhorizontal, ted as the domicile of crustaceans – crabs and branching tunnels, up to 25 mm thick, cylindrical shrimps (Frey et al. 1984) – which dig in a firm, or elliptical in cross-section, displaying elongated semiconsolidated substrate. Such behaviour striation on exterior of burrow casts. Branches are is typical of the Glossifungites ichnofacies. Y-shaped, usually enlarged at points of bifurcation. The striation consists of casts of scratch marks, Striation approximately longitudinal, only on produced by locomotory organs of the tracemaking the side surfaces oblique. Burrows are filled with animals. Spongeliomorpha is a facies-crossing fine-grained, light grey sand, commonly pyritized. form, noted from shallow and deep-marine deposits They occur mainly as endichnia in dark grey as well as from the fresh-water environments (Frey mudstones; only one problematic specimen et al. 1984; Frey and Pemberton 1984; Buatois and occurred on the sole surface of sandstone. Mángano 1998; Uchman 1998). 94 Volumina Jurassica, Volumen VI

A B C

S?

He

1 cm 2 cm 0,5 cm

E D 2 cm F

1 cm 1 cm

5 cm G 0,5 cm H

Fig. 6. Trace fossils from the Ciechocinek Formation : A – Helminthopsis on a parting plane in mudstone; B – Helminthopsis (He) and Spongeliomorpha? (S?) on a sole surface of sandstone bed; C – small Protovirgularia on a sole surface of a sandstone lens; D – two highly biotur - bated horizons with Spongeliomorpha burrows from the Koz∏owice outcrop; E, F – Gyrochorte on the upper surfaces of sandstones; G, H – Spongeliomorpha : G – close-up view of tunnel filling; H – scratch marks (detail from G). A-E, G, H – Koz∏owice outcrop; F – Nowa WieÊ 12 borehole.

In the Ciechocinek Formation many other, are less common and are concentrated in non-identified pascichnial traces fossils occur. the lower half of succession (Fig. 4). In many They were observed on sole surfaces of sandstones intervals, diminution of ichnofossil size, common as well as in thin sections from sideritic mudstones for Planolites , is a characteristic feature. In these and siltstones. parts of succession, which are devoid of other trace fossils, Planolites is often less than 1 mm thick. CHARACTERISTICS OF ICHNOFOSSIL The degree of bioturbation ranges usually from ASSOCIATION low to moderate (BI = 1-3 in the scale after Taylor and Goldring 1993) (Fig. 7), the bedding boundaries The trace fossil association from the Ciecho- are distinct and primary sedimentary structures cinek Formation is of low diversity and dominated well preserved. In such deposits intensively by simple forms of non-specialized deposit-feeders. or completely bioturbated (Fig. 7: D) intercalations The most common is Planolites isp., which occurs occur as well as layers devoid of bioturba- in almost whole succession, accompanied by some tional structures, with undisturbed lamination non-identified pascichnia. In some cores Planolites (Fig. 7: A). is the only ichnofossil observed. Other trace fossils Trace fossils from the Lower Jurassic Ciechocinek Formation, SW Poland 95

PALAEOENVIRONMENTAL INTERPRETATION increased water salinity, resulting from the transgression. Noteworthy is the presence of two The trace fossil association, restricted to a few highly bioturbated horizons with Spongelio- facies-crossing ichnotaxa, does not bring morpha in the Koz∏owice outcrop (Fig. 4). substantial information about the salinity of basin The occurrence of trace fossils characteristic water. The finding of Diplocraterion (Pieƒkowski of the Glossifungites ichnofacies marks an episode 1988, 2004) and Gyrochorte as well as the lack of of firmground formation, which is usually ichnofossils characteristic only of fresh-water associated with reduced sediment input and deposits, such as Scoyenia or traces of insect erosional exhumation of compacted substrate activity, point to the marine character of the water. (Pemberton et al. 2001). Therefore, horizons with Other features, such as the lack of shelled Spongeliomorpha could point to a transgressional organisms, reduced diversity of the ichnofossil impulse following a short episode of regression. association with simultaneous high population The same episode could be marked by a thin layer density, largely consisting of the single ichnogenus of coarse grained sandstone and gravel, occurring (Planolites ), the prevalence of infauna producing in the lower part of the Nowa WieÊ 12 borehole simple structures, as well as frequent size (Fig. 4). However, such a regional event should reduction, are characteristic of a brackish water be pronounced throughout the basin, whereas environments (Howard and Frey 1973; Pemberton other profiles are devoid of convincing evidence of and Wightman 1992; Pemberton et al. 2001). sea level change. Thus, it is more likely that In the lower half of the succession the ichno- the firmground formation and the short- fossil association is more diverse and includes lived supply of coarser material in sections Diplocraterion parallelum and Gyrochorte mentioned was linked with local changes of bottom (Fig. 4). It can be inferred that these deposits mark circulation.

A C

1 cm 0,5 cm

B D

2 cm 0,5 cm

Fig. 7. Bioturbation degrees in the Ciechocinek Formation deposits : A – non-bioturbated mud with undisturbed lamination; B – sparsely bioturbated mud; C – moderately bioturbated massive siltstone; D – completely bioturbated clayey silt; microphotograph of massive deposit devoid of macroscopically detectable bioturbational structures (one nicol). All photographs show cross-sections of beds. A, B, D – Koz∏owice outcrop; C - Wichrów 50 borehole. 96 Volumina Jurassica, Volumen VI

In the upper half of the succession, the diversity Lower Cretaceous Grand Rapids Formation, which of the trace fossil suite is lower, and almost only was interpreted as reflecting reducing or anoxic Planolites occurs. In the uppermost part of the conditions developed in a restricted setting succession the phyllopod Estheria sp., typical (Beynon and Pemberton 1992). The prevalence of of brackish environments, also occurs (Wr´czyca 3 reducing conditions in sediments analyzed and Przystajƒ 20 boreholes). These deposits marks is advocated by the presence of early diagenetic a falling in salinity related to regression. pyrite as well as the common siderite minera- The ichnofossil association does not contain lization in muds (Leonowicz 2005). In places where ichnotaxa diagnostic of Seilacher’s ichnofacies; the bottom water was stagnant and sediment however, it reveals many similarities to the enriched in organic matter, anoxic conditions could Cruziana ichnofacies (Seilacher 1967). The muddy- develop, resulting in non-bioturbated levels. silty character of the deposits, dominance Episodes of bottom current activity could improve of deposit-feeders, occurrence of pascichnia, oxygenation of the sea-floor and lead to formation domichnia and repichnia structures as well as the of highly bioturbated levels. prevalence of horizontal and subhorizontal orientations of burrows – these features are typical of the Cruziana ichnofacies, known from , SUMMARY , , tidal flat and continental shelf deposits (Seilacher 1967; Frey and Pemberton 1984). • The mud-silt deposits of the Ciechocinek Forma- Generally, it points to shallow marine, moderate to tion contain a low diversity trace fossil low-energy environments, situated between the association, which includes Planolites , Palaeo- fair-weather and storm wave base. phycus , Helminthopsis , Gyrochorte , Proto- The predominant low to moderate density of virgularia and Spongeliomorpha as well trace fossils indicates that conditions in the bottom as many small, unidentified pascichnia. The sediment were generally moderately favourable for occurrence of marine trace fossils Diplocra- benthic fauna, due to the lowered water salinity terion and Gyrochorte indicates that this suite and possibly low oxygenation of sediment. represents an impoverished marine association. Bottom conditions changed irregularly from place •The diversity of the ichnofossil association and to place and from time to time resulting in the the intensity of bioturbation were affected by the formation of strongly bioturbated and non- salinity of basin water and oxygenation of bioturbated intercalations. Apart from salinity, bottom sediment. Benthic food availability was benthic life is influenced by a number of factors, not decisive, as deposits of the Ciechocinek from which the most important is oxygenation of Formation are generally rich in organic matter. the seafloor and benthic food availability. • Low-salinity water resulted in a decrease in trace As deposits of the Ciechocinek Formation are fossil diversity, represented mainly by simple generally rich in organic matter, fluctuation of burrows of non-specialized deposit-feeders. seafloor oxygenation was the most probable reason These are, however, quite abundant in some for changeable conditions. Deposition of the parts of the succession. The highest salinity and Ciechocinek Formation originated predominantly the maximum of fall into as a result of quiet deposition from suspension, the lower half of the succession. interrupted periodically by storm-generated • The degree of bioturbation depended, most pro- offshore currents as well as long-lasting turbidity bably, on the oxygenation of the seafloor, which currents of low density, linked with seasonal changed with time, resulting in intercalations of changes in river discharge and displacements of high and low bioturbated deposits with non- river mouths (Leonowicz 2002). In such conditions bioturbated muds. The bottom sediment was the bottom water, as well as the organic-rich bottom mainly poorly oxygenated due to the low energy sediment, could stay poorly oxygenated, and the of sedimentary environment and the high benthic animal community was restricted to taxa content of organic matter. Episodes of increased adapted to inhabit oxygen-depleted environments. oxygenation are related to the activity of bottom Deposits with the low diversity Planolites currents generated by storms, seasonal changes association, characterized by reduced burrow size, in river discharge and displacements of river resemble partly the Planolites association from the mouths. Trace fossils from the Lower Jurassic Ciechocinek Formation, SW Poland 97

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