The Or do vi cian rocks of Pobroszyn in the Łysogóry re gion of the Holy Cross Moun tains, Poland
Wiesław TRELA, Sylwester SALWA and Zbigniew SZCZEPANIK
Trela W., Salwa S. and Szczepanik Z. (2001) — The Or do vi cian rocks of Pobroszyn in the Łysogóry re gion of the Holy Cross Moun tains, Po land. Geol. Quart., 45 (2): 143–154. Warszawa.
In the vil lage of Pobroszyn near Opatów, a faulted sec tion of Or do vi cian de pos its rep re sented by up per Tremadoc clayey-silty lithofacies, up per Arenig car bon ate-phosphorite lithofacies and Up per Or do vi cian claystones with lime stone interbeds, were iden ti fied.
The up per Tremadoc is dated on ba sis of acritarch. This is the first time that up per Tremadoc de pos its have been doc u mented in the Łysogóry re gion. The late Arenig transgressive de pos its were prob a bly pre ceded by emer gence in the lat est Tremadoc and early Arenig.
The Or do vi cian rocks from Pobroszyn are in tensely tectonised. Two groups of faults, oblique and lon gi tu di nal, are dis tin guished. The first one strikes from 120–140°, and dip to NE at 40–45°, and the sec ond one that strikes 15–25° and dips 65–80° to E.
Wiesław Trela, Sylwester Salwa and Zbigniew Szczepanik, Holy Cross Mts. Branch, Pol ish Geo log i cal In sti tute, Zgoda 21, PL-25-953 Kielce, Po land, e-mail: trela@pgi.kielce.pl (re ceived: Au gust 26, 1999; ac cepted: Oc to ber 3, 2000).
Key words: Holy Cross Moun tains, Łysogóry re gion, Or do vi cian, lithofacies, acritarchs, tec ton ics.
INTRODUCTION
In the Łysogóry re gion of the Holy Cross Moun tains, Or do - vi cian rocks have been mainly iden ti fied in bore holes, as solid ex po sures are scarce.
In 1998 the au thors dug 3 pits at Pobroszyn, which ex posed al most the en tire Or do vi cian sec tion (Figs. 1, 2). The con tacts of the Or do vi cian de pos its with Cam brian and Si lu rian rocks, and the lith o logic units to gether with their con tacts, were iden ti fied.
The sedimentological in ves ti ga tions de scribed here were based on mac ro scopic ob ser va tions and ex am i na tions of 25 thin sec tions, mostly of lime stone and siltstone. The tec tonic stud ies in cluded mac ro scopic ob ser va tions of tec tonic mesostructures sup ported by strike and dip mea sure ments of bedding and tec tonic sur faces. Sam ples of clays and silts were sam pled and an a lyzed for acritarchs. A palynoflora from the Cam brian-Tremadoc rocks was de scribed and some of the acritarchs were iden ti fied.
HISTORY OF STUDIES AND GEOLOGICAL SETTING
The Or do vi cian de pos its of Pobroszyn were orig i nally de - scribed by Samsonowicz (1934). Tomczyk (1957), Czarnocki (1950), Tomczykowa (1968), Bednarczyk (1971, 1981), Kowalczewski et al. (1976) also com mented on the Or do vi cian rocks from this sec tion. Those stud ies were mainly fo cussed on the stra tig ra phy of the Pobroszyn sec tion and on the geo logical struc ture of the Opatów dis trict; nei ther sedimentological nor de tailed palaeontological stud ies were car ried out.
In the Łysogóry re gion of the Holy Cross Moun tains, con - tin u ous sed i men ta tion of dark “Dictyonema” clays was tak ing place from the Late Cam brian to the early Tremadoc (Tomczyk and Turnau-Morawska, 1967; Tomczykowa, 1968), though there is lit tle palaeontological ev i dence for the pres ence of Tremadoc sed i ments, for it is un cer tain that frag ments of dendroid graptolites are of Tremadoc taxa. Pre vi ous stud ies showed a strati graphi cal gap be tween the up per Tremadoc and up per Llanvirn de pos its in the Jeleniów IG 2 bore hole (Fig. 1).
In the late Llanvirn, car bon ates, known from bore holes
Bukowiany IG 1a and Jeleniów IG 2, pre dom i nated (Tomczyk and Turnau-Morawska, 1967; Tomczykowa, 1968;
Bednarczyk, 1971, 1981; Kowalczewski, 1972, 1994;
Kowalczewski and Wróblewski, 1971, 1974). In the Caradoc, trans gres sion of the Nematograptus gracilis Zone, dark grey claystones were de pos ited (Tomczyk and Turnau-Morawska, 1967; Tomczykowa, 1968; Deczkowski and Tomczyk, 1969).
In the late Ashgill, a low ered sea level was marked by the de po - si tion of lime stones, sand stones and siltstones in many sec tions in the Łysogóry re gion (Czarnocki, 1950; Kielan, 1956, 1959;
Tomczykowa, 1968; Deczkowski and Tomczyk, 1969).
LITHOFACIES AND DESCRIPTION OF THE POBROSZYN SECTION
Or do vi cian rocks crop out in the vil lage of Pobroszyn, 4 km east of Opatów, in the Opatówka River val ley (Fig. 1). These rocks are faulted against Cam brian rocks de vel oped as var ie - gated siltstones with red dish and brown ish-grey thin- and me - dium-bed ded quartzitic sand stones. The bot tom sur faces of
these sand stones con tain many traces of the tri lo bite ichnogenera Cruziana and Rusophycus (Pl. I, Fig. 3). The top of the Or do vi cian suc ces sion is faulted against brown-grey Si - lu rian shaley claystones. The ex posed Or do vi cian sec tion in - cludes the fol low ing lithofacies:
Clayey-silty lithofacies. This is about 14.0 m thick (Fig. 2;
pack ages A and C — Fig. 3; Pl. I, Fig. 1) en com pass ing dark grey claystones with thin-bed ded siltstones and fine-grained sand stones ce mented by sil ica (re sem bling quartzitic arenites).
At the top these claystones are ol ive, be com ing rusty-yel low and po rous within a 30-cm zone close to the con tact with over - ly ing rocks de vel oped in a car bon ate-phosphorite lithofacies.
This change of col our is con nected with an in crease in po ros ity and fis sure spac ing. In the up per por tion of this sec tion, an in - crease in sil ica-ce mented siltstone and sand stone interbeds was noted. Some of these are len tic u lar re sem bling ero sional chan - nels. Within this fa cies, infaulted grey cal car e ous sand stones with phos phate brachi o pod shells oc cur (Samsonowicz, 1934).
The thick ness of these sand stones is about 0.8 m (pack age B — Fig. 3; Pl. I, Fig. 2).
Car bon ate-phosphorite lithofacies. De pos its of this lithofacies dated by cono donts on the up per Arenig (Dzik,
Fig. 1. Lo ca tion map of the Pobroszyn sec tion: A — Lo ca tion of the Holy Cross Moun tains in Po land; B — Palaeozoic block bound aries in the Holy Cross Moun tains and lo ca tion of the Pobroszyn sec tion; C — Geo log i cal struc ture of the area of Pobroszyn (ac cord ing to Kowalczewski et al., 1976, mod i fied) 1 — faults: a — con firmed, b — in ferred; 2 — Permo-Mesozoic, 3 — De vo nian, 4 — Or do vi cian and Si lu rian, 5 — Cam brian
1999) are about 3.6 m thick (pack age D — Fig. 3; Pl. I, Fig. 1) in clud ing:
— 20-cm bed of grey-green lime stone with peb bles of 0.2–3 cm in di am e ter (Pl. II, Figs. 2, 3). The peb bles con sist of black claystone, siltstone (ce mented by sil ica), phosphorite, fine-grained sand stone (ce mented by phos phate), quartz, and fer ric (he ma tite) amor phous con cen tra tions and grains. The peb bles are ir reg u larly scat tered in a groundmass; in some places form con cre tions. This bed in cludes ero sional sur faces im preg nated with fer ric min er als. Most of the inter gra nu lar spaces and peb bles are en crusted with iron com pounds.
— 20-cm bed of red lime stones with low-an gle cross-bed - ding, synsedimentary faults and small ero sional chan nels (Pl.
II, Fig. 3).
— 20-cm bed of car bon ate-phosphorite rock show ing a clot ted-grainy struc ture com posed of intraclasts up to 4 cm in di am e ter, cri noid de tri tus (Pl. II, Fig. 4) and phosphorite ooids.
The intraclasts con sist of lime stones with peb bles and dark phosphorite rock.
— 3-m thick pack age of green-grey lime stones and marly claystone with nu mer ous spher i cal and discoidal phosphorite con cre tions (Pl. III, Fig. 2). The rounded con cre tions are about 0.5–4.0 cm in di am e ter, whereas the discoidal ones vary from 2 to 10 cm in di am e ter (Pl. III, Figs. 3, 4). These de pos its con tain dark grey and black phosphorite rock interbeds 5–15 cm thick, and show hor i zon tal lam i na tion (Pl. III, Fig. 1), as well as ev i -
dence of ero sion and re work ing marked by grey-brown small intraclasts reach ing 0.5 cm in di am e ter.
At the bot tom of the lime stone bed with peb bles, cal cite lay ers vary ing from 0.2 to 2.0 cm in thick ness oc cur (Pl. III, Figs. 1, 2); on be com ing thin ner they as sume lens-shaped forms. They con sist two lay ers of cal cite crys tals. The thin ner one is com posed of small, iso met ric crys tals about 0.1–0.3 mm in di am e ter, and the other con sists of co lum nar crys tals 0.5–1.0 mm long. Some of these lay ers are sep a rated by 1-mm thick micrite and microsparite laminae. The cal cite lay ers re - sem ble microstalactite druse and crust (Thrailkill, 1976; Folk and Assereto, 1976; Esteban and Klappa, 1983; Vera et al., 1988).
Within the peb bly lime stone thin (0.2–1.0 cm thick), in dis - tinctly lam i nated, brown-rusty overgrowths im preg nated with iron oc cur (Pl. II, Figs. 1, 2). They show traces of me chan i cal dis rup tion and ero sion, dis solv ing and re newed pre cip i ta tion.
Small hol lows are infilled with lithoclasts, phos phate-fer ric ooids and pisoids, and other grains. These sur faces look like caliche (James, 1972; Read, 1974; Har ri son, 1977; Har ri son and Steinen, 1978; Esteban and Klappa, 1983; Peryt, 1984).
Grey claystone lithofacies. De pos its of this fa cies are about 15 m thick and strongly tec toni cally de formed (pack age E — Fig. 3), which makes any sedimentological anal y sis dif fi - cult. These rocks are dark grey with an ol ive and brown tint. At the bot tom, a 1-m thick pack age of infaulted black claystones oc cur. They con tain nu mer ous siltstone interbeds reach ing
Fig. 2. Scheme of field works at Pobroszyn
1 — faults, 2 — bound aries of lithological suc ces sions, 3 — lithological com plexes, 4 — strikes and dips, 5 — field data
2 cm in thick ness; but their re la tion ships are hard to de ter mine due to tec tonic mod i fi ca tion. The de pos its are gently hor i zon - tally lam i nated. In this por tion of the sec tion, scarce thin interbeds of lydite, phosphorite-fer ric rock and si der it ic lime -
stone up to 5 cm thick oc cur. At the top a 10-cm grey lime stone bed is pres ent.
PALYNOLOGICAL STUDIES
In Pobroszyn sec tion pre lim i nary palynological (acritarch) anal y ses were car ried on the clayey-silty lithofacies (pack ages A and C), as well as of the dark grey Or do vi cian (Figs. 2, 3) claystone (pack age E — Fig. 3).
Neither the Cam brian sed i ments nor the dark grey claystone lithofacies (E) contained any iden ti fi able or ganic re - mains. Scarce carbonized de tri tus indicates that the lack of acritarchs in these rocks is due to ther mal deg ra da tion.
In the clayey-silty lithofacies (pack ages A and C), a rich al - though dam aged palynoflora was found. Most of the sam ples de rived from com plexes A and C con tain poorly pre served spe - cif i cally, un iden ti fi able acritarchs; forms of char ac ter is tic diacriodal sym me try (Diacromorphitae), those with a large po - lar opening (“galeate”), and ra di ally sym met ri cal forms pre vail here (Polygonium). Sim i lar as sem blages oc cur in up per most Cam brian and Tremadoc sed i ments world wide (Vanguestaine, 1974; Mar tin and Dean, 1981, 1988; Vanguestaine and Van Looy, 1983; Welsch, 1986; Di Mila et al., 1989; Volkova, 1990; Mar tin, 1992).
Spec i mens iden ti fi able to spe cies level were found only in one sam ple from the up per por tion of pack age C (Fig. 3; Pl.
IV). The fol low ing spe cies were doc u mented:
Acanthodiacrodium sp., ?Caldariola sp., ?Cymatiosphaera sp., Cymatiogalea sp., Cymatiogalea polygonophora Górka, Dasydiacrodium sp., Ladogiella sp., Lophodiacrodium sp., Arbusculidium sp., Arbusculidium destombesii Denuff, Stelliferidium cf. modestum (Górka), Stelliferidium sp., Vulcanisphaera sp. and Peteinosphaeridium sp. This as sem - blage dif fers from the up per most Cam brian microflora, known from the Wilków IG 1 bore hole and the Mąchocice (Szczepanik, un pub lished). There are con sid er ably fewer forms of diacrioidal sym me try (Acanthodiacrodium, Dasydiacrodium), and far more acritarchs of the gen era Polygonium, Cymatiogalea, Stelliferidium and Multiplicisphaeridium. The spe cies Cymatiogalea polygonophora Górka, Stelliferidium cf. modestum (Górka), and the other acritarch gen era Caldariola and Peteinosphaeridium may in di cate up per Tremadoc or per haps Tremadoc/Arenig bound ary rocks. The tax o nomic com po si - tion of this as sem blage is sim i lar to the late Tremadoc and Tremadoc/Arenig as sem blage in the Bardo Syncline (Górka, 1969, 1990; Szczepanik, 1997b). It should be stressed here that acritarchs were found only in the higher (more north ern) part of pack age C (Fig. 3). It can not be ex cluded that the south ern part, tec toni cally con tacted with Cam brian rocks, may be older.
Col ours of acritarchs from lithofacies A and C are gen er ally black, in places dark brown, in di cat ing palaeotemperatures above 100°C. A high de gree of ther mal al ter ation is typ i cal for Lower Palaeozoic microflora of the Łysogóry re gion (Szczepanik, 1977a). The co eval rock suc ces sions from the Bardo Syncline and from the re main ing ar eas of the Kielce re - gion pos sess well-preserved acritarch as sem blages show ing no
Fig. 3. Or do vi cian sec tion stud ied at Pobroszyn
1 — tec tonic contacts, 2 — quartzitic sand stones, 3 — lime stones, 4 — cal - car e ous sandstones, 5 — lime stones with peb bles, 6 — siltstones, 7 — claystones, 8 — phosphorite con cre tions, 9 — lo ca tions of identifiable acritarchs, 10 — lith o logic sam ples placed in the plates, A–E — lithofacies pack ages
ther mal al ter ation (Szczepanik, 1997a, b). Even at Ublinek, lo - cated only 5 km south from Pobroszyn, the microflora as cribed to the Cam brian/Tremadoc bound ary shows a very low de gree of ther mal al ter ation.
STRATIGRAPHY
The pres ence of Tremadoc acritarchs in clayey-siltstone lithofacies of pack age C, and their po si tion above Cam brian quartzitic rocks and be low a car bon ate-phosphorite Arenig suc ces sion (Dzik, 1999), in di cates a chronostratigraphic po si - tion sim i lar to that of the Klonówka Shale For ma tion (Orłowski, 1975).
The pres ence of lower Tremadoc claystones in sec tions Jeleniów IG 2 and Brzezinki IG 1 (Tomczyk and Turnau-Morawska, 1967; Tomczykowa, 1968) and late Tremadoc acritarchs in the Pobroszyn section may in di cate con tin u ous sed i men ta tion in the Łysogóry re gion span ning the Cam brian to late Tremadoc interval. It can not be ex cluded though that there were sep a rate trans gres sions in the Late Cam - brian and Tremadoc.
It should be noted that the acritarch spe cies Vulcanisphaera frequens (Górka), Cymatiogalea nebulosa (Denuff) and Peteinosphaeridium trifurcatum (Eisenack), de scribed by M.
Moczydłowska in the Wiśniówka quarry (Moczydłowska in:
Kowalczewski et al., 1986), seem to in di cate an youn ger age than the early Tremadoc. The spe cies men tioned are also known from the up per Tremadoc Zbilutka Siltstone and Chalcedonite Mem ber (Górka, 1969). They may hold the same strati graphic po si tion as microflora from an in di vid ual sam ple found at the top of pack age C at Pobroszyn. Both at Wiśniówka and Pobroszyn, a tec tonic con tact be tween the clayey-silty sed i ments and the Mid dle and Up per Cam brian quartzitic com plexes was re corded. It can not di rectly be con - firmed that there is a con tin u ous sed i men tary se quence span - ning Up per Cam brian to Tremadoc de pos its, as is typ i cal for the Klonówka Shale For ma tion (Orłowski, 1975). The brachi o - pods found within cal car e ous sand stones (pack age B — Fig. 3) also sug gest the pres ence of up per Tremadoc de pos its (Bednarczyk, pers. comm.).
The pres ence of lower Tremadoc rocks in the Łysogóry re - gion of the Holy Cross Moun tains is doc u mented only by dendroid graptolites de scribed as Dictyonema sp. by Tomczykowa (1968); their strati graphic sig nif i cance is ques - tion able be cause this ge nus spans the Cam brian to the Car bon - if er ous, and these spec i mens need fur ther study. In the Brzezinki IG 1 bore hole, be low a depth (79.0 m) where a frag - ment of Dictyonema was found, graptolites of the ge nus Bryograptus (depth 87.2–88.9 m) oc cur, which may in di cate at least an up per Tremadoc age for this suc ces sion (Czarnocki and Dembowska, 1950 in: Tomczykowa, 1968).
There is no cer tain ev i dence that sed i men ta tion was con tin - u ous be tween the Cam brian and Tremadoc. The Tremadoc sed i ments (at Wiśniówka and Pobroszyn) may rep re sent the up per por tion of this stage, hold ing the same strati graphic po si - tion as in the Kielce re gion. In the car bon ate-phosphorite lithofacies of the Pobroszyn sec tion, Dzik (1999) iden ti fied late
Arenig (up per most Volkhov and Kunda) cono donts. The de - pos its of this lithofacies show con sid er able sim i lar ity to up per Llanvirn car bon ate rocks from the Jeleniów IG 2 and
Bukowiany IG 1a bore holes (Tomczyk and
Turnau-Morawska, 1967; Bednarczyk, 1971; Kowalczewski and Wróblewski, 1971, 1974; Kowalczewski et al., 1976) where they over lie Tremadoc claystones. These rocks were as - signed to the Bukowiany Lime stone For ma tion (up per Llanvirn) (Bednarczyk, 1981).
The sim i lar ity of lith o logical sec tions at Pobroszyn and Bukowiany sug gests that cono donts from con tacts be tween Tremadoc claystones and car bon ate deposits should be re ex - am ined, to en ables precise age de ter mi na tion of these sed i - ments, par tic u larly as closely lo cated lithologically sim i lar sec tions, have yielded dif fer ent biostratigraphical ages.
Eustatic changes of the sea level inferred in the Or do vi cian, and the com mon oc cur rence of car bon ate-phosphorite lithofacies, point to two in de pend ent transgressive ep i sodes which left very sim i lar sed i ments.
In the high est lime stone interbed, placed at the top of the clayey suc ces sion (pack age E, Fig. 3) and prob a bly as signed to the Jeleniów Claystone For ma tion (Caradoc) (Bednarczyk, 1981), Dzik (1999) iden ti fied cono donts span ning the lat est Caradoc to Ashgill. The pres ence of lower Caradoc de pos its in the Pobroszyn sec tion was sup ported by the graptolite taxa:
Climacograptus sp. and Diplograptus cf. multidens Elles et Wood (Samsonowicz, 1934; Tomczyk, 1957; Tomczykowa, 1968). The lime stone interbeds ob served at the top of this sec - tion are lithologically sim i lar to car bon ate de pos its from the Wilków IG 1 bore hole (Deczkowski and Tomczyk, 1969) as - cribed to the Wólka Siltstone For ma tion (Ashgill) (Bednarczyk, 1981).
SEDIMENTARY ENVIRONMENTS
Sedimentological stud ies and re con struc tions of sed i men - tary en vi ron ments are hard to carry out be cause of tec tonic de - for ma tion of the Tremadoc and Up per Or do vi cian de pos its in this sec tion, and so at ten tion is fo cussed on the Arenig rocks and on their con tact with the un der ly ing Tremadoc rocks. At the Cam brian/early Tremadoc bound ary of the Łysogóry re - gion, sed i men ta tion oc curred be low wave base, in a deep shelf set ting (Tomczyk and Turnau-Morawska, 1967; Studencki, 1994). Lithological de vel op ment of up per Tremadoc sed i ments at Pobroszyn sug gests calm con di tions that fa voured the ac cu - mu la tion of clays. In di vid ual thin lay ers and lenses of siltstones and fine-grained sand stones were prob a bly linked to short and sud den storm ep i sodes.
The Tremadoc and up per Arenig de pos its of the sec tion de - scribed re veal an ero sional sur face, prob a bly re lated to the Ceratopyge (CRE) global re gres sive event (Erdtmann, 1986).
Around Pobroszyn this in di cates emer gence and ero sion at the late Tremadoc/early Arenig bound ary. Weathering pro cesses in ten si fied lead ing to an in crease of rock po ros ity and the ox i - da tion of fer ric min er als. The oc cur rence of microstalactite cal - cite overgrowths at the bot tom of the peb bly lime stones have an im por tant sig nif i cance in the anal y sis of the Or do vi cian ba sin
1. Ex posed Or do vi cian sec tion at Pobroszyn with marked pack ages: C — top of clayey-silty lithofacies, up per Tremadoc, D — car bon ate-phosphorite lithofacies, up per Arenig, E — bot tom of grey claystone lithofacies, Caradoc?. 2. Top sur face of cal car e ous sand stones with phos phate brachi o pods, pack - age B, up per Tremadoc, Fig. 3 — sam ple no. 2. 3. Traces of tri lo bite spe cies Cruziana and Rusophycus on bot tom sur faces of sand stones, Cam brian, Fig. 3
— sam ple no. 1. Scale bar — 1 cm
PLATE I
1, 2. Peb bly lime stone; cal cite lay ers and lenses be low; thin dis con tin u ous micritic overgrowths above; bot tom of pack age D, up per Arenig, Fig. 3 — sam - ple no. 3. 3. Brown-red lime stone bed with low an gle cross-bed ding and small synsedimentary faults; bot tom of pack age D, 20 cm from pack age base, above peb bly lime stone, up per Arenig, Fig. 3 — sam ple no. 4. 4. Dark grey phosphorite rock with lime stone intraclasts, peb bles and cri noids. Scale bar — 1 cm
PLATE II
1. Grey lime stone, hor i zon tally lam i nated, with a dark phosphorite rock interbed, pack age D, 2.0 m from pack age base, up per Arenig, Fig. 3 — sam ple no.
8. 2. Grey-green marly claystone with phosphorite con cre tion, pack age D, up per Arenig, Fig. 3 — sam ple no. 6. 3, 4. Phosphorite con cre tions; pack age D, up per Arenig, Fig. 3 — sam ple no. 7. Scale bar — 1 cm
PLATE III
1, 2. Stelliferidium cf. modestum (Górka). 3, 4. Arbusculidium destombesii Denuff. 5. Priscotheca sp. 6. Cymatiogalea sp. 7, 8, 12. Acanthodiacrodium sp.
9. Cymatiogalea cf. cristata (Downie). 10. Vulcanisphaera cf. nebulosa Denuff. 11. Vulcanisphaera sp. 13. Cymatiogalea cf. polygonophora Górka. 14, 15. Cymatiogalea polygonophora Górka. 16. Peteinosphaeridium sp. 17. Stelliferidium sp. 18. ?Coryphidium sp. 19. Stellechinatium sp. 20.
Dasydiacrodium longicornutum Górka. 21, 22, 23. Caldariola sp. 24. ?Caldariola sp. Dif fer ent scale
PLATE IV
in the Łysogóry re gion. Both the pres ent and an cient microstalactite druse and crusts oc cur in a supratidal zone or in the higher part of the intertidal zone (Purser, 1969; Purser and Loreau, 1973; Scholle and Kins man, 1974; Peryt and Wag ner, 1981; Shinn, 1983; Peryt, 1984). Thus, the lower part of this peb bly lime stone was prob a bly de pos ited within an eu- or even supralittoral (supratidal) zone, dur ing ma rine trans gres sion over a pre vi ously emer gent area. The ap pear ance of open ma - rine cono donts (Dzik, 1999) in the over ly ing bed of the peb bly lime stone might have re sulted from open ma rine wa ters in flow with strong tides or cur rents (e.g. upwellings). Fur ther more the caliche-like sur face in di cates a tem po rarily emer gence as so ci - ated with lo ca tion in the intertidal zone. Storm waves or tides eroded lithoclasts from the un der ly ing Cam brian and Tremadoc de pos its. Strong tur bu lence con tin ued dur ing ac cu - mu la tion of sed i ments di rectly over ly ing the peb bly lime stone, as ev i denced by lime stone intraclasts with peb bles, ero sional chan nels and sur faces, as well as by a cha otic dis tri bu tion of phosphorite ooids and cri noid de tri tus.
In the Łysogóry re gion the emer gence that took place at the Tremadoc/Arenig bound ary is cor re lated with a pre-Arenig re - gional sed i men tary dis con ti nu ity in north east ern Po land (Modliński, 1973, 1982; Szymański, 1973, 1984; Znosko and Chlebowski, 1976).
The up per part of car bon ate-phosphorite lithofacies shows a sea level rise and calm de po si tion of clays be low a nor mal wave base. Pe ri odic in creases in en vi ron men tal tur bu lence, ero sion and redeposition of sed i ment took place. In di vid ual lime stones and car bon ate-phosphorite beds re veal fea tures of sed i ments ac cu mu lated by cur rents (Wil son, 1975; Flügel, 1982; Scholle et al., 1983; Aigner, 1984, 1985; Jones and Desrochers, 1992), and seem to be a re cord of at ten u ated dis tal storm cur rents.
The pres ence of claystones, lime stones and phosphorite rocks gen er ally formed in an sublittoral en vi ron ment, above a thin layer of su pra- and eulittoral sed i ments, in di cates marine trans gres sion in the late Arenig.
TECTONICS
In the sec tion ex am ined, the an gle of dip var ies across 30 m from 30 to 80°NNE, and is associated with fault ing. The faults are grouped in two oblique and one lon gi tu di nal sets.
The oblique faults of the first set dip to wards 120–140°, whereas the fault sur faces 40–50°NE, re spec tively. These faults are of strike-slip char ac ter with a small overthrust com - po nent towards the west. This array also in cludes the fault that sep a rates Or do vi cian rocks on the east ern side from Cam brian rocks to the west, pre sum ably clos ing the Pobroszyn el e ment from the west. This is also ev i denced by flex ure in quartz ite beds on the west ern side, in which strike changes from 73 to 97° at the fault drag. These beds were partly boudinaged and in ten sily fractured; shales from the east ern side of the fault change their colour from dark grey to brown-grey due to scat - tered hae ma tite. This min eral forms spher i cal septaria up to 2 cm in di am e ter. Hae ma tite oc curs along 4 m of the fault, within a half-metre zone of al tered shales.
The oblique faults of the sec ond set have strikes of 15–25°
and steep dips of 65–80°E. This set shows ev i dence of strike-slip mo tion. Alteration zones along these faults are only 10–15 cm thick bleached and shat tered. One such oblique fault was seen to pass into a lon gi tu di nal overthrust.
The strikes of the oblique faults are in ac cor dance with di - rec tions ob served by Studencki (1985) in Jeleniów range of Holy Cross Mts., i.e. the first or der set of faults is su pe rior in re - la tion to the sec ond one. Tran si tion from the oblique to lon gi tu - di nal faults seems to be com mon phe nom e non within the ex posed rocks, re lat ing to both sets of the oblique faults.
Proven lon gi tu di nal faults are strike-faults (95–110°) and are usu ally placed at sharp bound aries of me chan i cally dif fer ent rocks, i.e. car bon ate-fer ric rocks and shales. Most of the bound - aries in the suc ces sions ex am ined are tec tonic, and are ac com pa - nied by al tered zones. They can be dis tin guished within shales as bleached and shat tered zones up to 0.7 m thick. Within two lime - stone beds (com plex E), which crop out in the pit ex am ined, boudinage oc curs as a re sult of overthrust move ment.
CONCLUSIONS
In the vil lage of Pobroszyn near Opatów, a faulted sec tion of Or do vi cian rocks over ly ing Up per Cam brian quartzitic siltstones and sand stones oc curs, dip ping at 30 to 80° to the NNE.
The Or do vi cian at Pobroszyn in cludes dark grey clayey-silty lithofacies (pack ages A and C) 14.0 m thick, dated as Tremadoc by acritarchs. Near the mid dle part of these pack ages, infaulted grey sandy lime stones with brachi o pods (pack age B) oc cur.
Higher in the sec tion, a 3.6-m thick car bon ate-phosphorite lithofacies as signed by cono donts to the up per Arenig (Volkhov) oc curs (Dzik, 1999). The Up per Or do vi cian sec tion is com pleted by a 15-m thick dark grey claystone lithofacies, in places with thin lydite, siltstone and grey lime stone interbeds. In the high est lime stone bed, cono donts doc u ment ing the Caradoc and Ashgill oc cur (Dzik, 1999).
At the late Tremadoc/early Arenig bound ary, emer gence took place. Marine trans gres sion in the late Arenig is marked by lit to ral to supralittoral deposits over lain by sublittoral deposits.
The faulted Or do vi cian sec tion at Pobroszyn in cludes Tremadoc clayey-siltstone lithofacies, Arenig car bon - ate-phosphorite lithofacies and Up per Or do vi cian dark grey claystone lithofacies. The up per most Arenig sed i ments of the Łysogóry re gion, de scribed by Dzik (1999), are a newly-discovered el e ment of Or do vi cian sed i men ta tion in the north ern part of the Holy Cross Moun tains. A thin de posit of lit to ral to supralittoral char ac ter formed af ter the ba sin had emerged or shallowed in the Pobroszyn area in the late Tremadoc and early Arenig. Over lying sublittoral sed i ments are an ev i dence of late Arenig ma rine trans gres sion pre vi ously un known in the Łysogóry re gion.
The faults form two oblique fault sets: the first strikes 120–140° and dips 40–55°NE and the other strikes 15–25° and dips 65–80°E, and there is also an oblique fault set (strike 95–110°) of overthrust char ac ter.
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