Annales Societatis Geologorum Poloniae (2014), vol. 84: 81-112. SEDIMENTOLOGY OF THE “ORE-BEARING DOLOMITE” OF THE KRAKÓW-SILESIA REGION (MIDDLE TRIASSIC, SOUTHERN POLAND) Michał MATYSIK Institute of Geological Sciences, Jagiellonian University, Oleandry 2a, 30-063 Kraków, Poland, e-mail: ma4tys@interia.pl Present address: Natural History Museum of Denmark, University of Copenhagen, 0ster Voldgade 5-7, DK-1350 Copenhagen, Denmark Matysik, M., 2014. Sedimentology of the “ore-bearing dolomite” of the Kraków-Silesia region (Middle Triassic, southern Poland). Annales Societatis Geologorum Poloniae, 84: 81-112. Abstract: The depositional history and facies heterogeneity of the epigenetically dolomitized Middle Triassic carbonates of southern Poland are poorly recognized, and existing concepts of fluid circulation entirely overlook the primary lithology as a facior coniroliing fluid flow. This study reconitructs the consecuiive phases of Kraków-Silesia Sub-basin history in the Anisian and highlights their influence on the development of the so-called “ore-bearing dolomite”. Extensive fieldwork and microfacies analyses were carried out in order to decipher the original depositional fabric of the ore-bearing dolomites. As a rule, epigenetic dolomitization affected a horizon of porous strata, 35 m thick and resting directly on impermeable, wavy-nodular clay-rich calcilutites of the Gogolin Formation, which represent the interval of deepest and fully marine (offshore) sedimentation. The sedimentary succession of the porous strata is bipartite. The lower part (Olkusz Beds) is composed of Balanoglossites and Thalassinoides micritic firmgrounds and peloidal packstones-grainstones, representing shoreface-foreshore facies assemblages, whereas the upper part (Diplopora Beds) consists of dolocretes, rhizolites, cryptalgal laminites, pe- loidal packstones-grainstones and bioturbated fine-grained dolostones, formed in a sysiem of tidal flats and la- goons. These two parts are separated by a subaerial disconformity, which marks a sequence boundary. During emersion, the underlying deposits were subjected to meteoric diagenesis, which led to the development of moldic porosity. This combinaiion of depositional history and diagenetic alieration determined the routes of initial migration of dolomitizing solutions on the one hand, and the location of cavern formation on the other. Owing to progressive dissolution, small caverns were changed into large karstic forms, in which the ore minerals precipi- tated ultimately. These findings emphasize the importance of sedimentological analysis to the understanding of the evolution of the Kraków-Silesia ore province. Key words: ore-bearing dolomite, epigenetic dolomitization, lead-zinc mineralization, facies pattern, peritidal and subtidal facies, Middle Triassic, Muschelkalk, Upper Silesia, Poland. Manuscript received 24 February 2014, accepted 23 September 2014 INTRODUCTION The large lead-zinc deposits of the Kraków-Silesian ore district of southern Poland (Fig. 1) occuras kilometre-size tabular bodies, mainly within epigenetically dolomitized shallow-marine carbonates of the Lower Muschelkalk, mostly Anisian in age. Although the main phases of ore- mineral precipitation started long after dolomitization, the processes were genetically related to each other (e.g., Sass- Gustkiewicz and Dżułyński, 1998). Exteni ive investiga- tions of the ores and ore-bearing dolomite, initiated 60 years ago, were based on thousands of drill cores and kilometres of mine galieries. These studies yielded 200 publications, mostly about ore-body geometry (e.g., Górecka, 1970; Szu- warzyński, 1983, 1996), mineral paragenesis and texiures (e.g., Smolarska, 1968; Gruszczyk and Strzelska-Sma- kowska, 1978; Harańczyk, 1983; Górecka, 1996; Leach et al., 1996a), ore geochemistry (e.g., Harańczyk, 1965; Zart- man et al., 1979; Kozłowski et al., 1980; Leach et al., 1996b; Viets et al., 1996), horizontal and vertical range of dolomitization (Alexandrowicz and Alexandrowicz, 1960; Alexandrowicz, 1966, 1971, 1972), origin and migration of mineralizing and dolomitizing fluids (e.g., Pałys, 1967; Ko- złowski et al., 1980; Wodzicki, 1987; Górecka et al., 1996; Sass-Gustkiewicz and Dżułyński, 1998). Only a few papers deal with the reconstruction of the sedimentary environment and facies pattern of this part of the Germanic (European) Basin in Middle Triassic time (Pawłowska and Szuwa- 82 M. MATYSIK Fig. 1. Location of the study area. A. Palaeogeographic map of the Germanic Basin in the Middle Triassic. The Upper Silesia region (white rectangle) was situated close to the Tethys Ocean. Modified after Narkiewicz and Szulc (2004). B. Present outcrop distribution of the Middle Triassic (Muschelkalk) carbonates in the Kraków-Silesia (studied) region, and the position of the Kraków-Lubliniec Fault Zone and the Devonian islands in the subsurface. Simplified after Myszkowska (1992). land sea ocean main lineaments archipelago of Devonian islands approximate western limit of epigenetic dolomitization KLFZ - Kraków-Lubliniec (Hamburg) Fault Zone SMF - Silesian-Moravian Fault N’-Triassic North Jurassic Keuper . (Upper Triassic) Muschelkalk (Middle Triassic) I Buntsandstein I (Lower Triassic) Palaeozoic major faults approximate western limit of epigenetic dolomitization Kraków-Lubliniec Fault Zone Devonian islands (subcrop view) SEDIMENTOLOGY OF THE “ORE-BEARING DOLOMITE” 83 rzyński, 1979; Pawłowska, 1982, 1985; Wyczółkowski, 1982; Myszkowska, 1992). How ever, it should be stressed that the primary lithology was an important factor, control- ling the flow of the dolomitizing fluids in late (burial) diage- nesis and the emplacement of ore deposits in this horizon; for instance, the most ferruginous “ore-bearing dolomites” (called ankerites) are developed in the coarsest-grained pe- loidal grainstones (Śliwiński, 1962, 1964; Pomykała, 1975; M. Matysik, unpublished data, 2012), and major ore bodies occur just above the impermeable horizon of wavy-nodular clay-rich limestones (e.g., Gruszczyk, 1957; Śliwiński, 1962; Bogacz et al., 1970). Bogacz et al. (1975) are the only authors to suggest that the hydrothermal solutions rose on a broad front along the faulted and folded NE margin of the Kraków-Silesia region and migrated from there to the SE, guided by sedimentary interfaces and porous primary dolo- stones. In accordance with this important interpretation, the facies heterogeneity within the “ore-bearing dolomite” suc- cession should be investigated first, before any sound model of fluid circulation can be proposed. Another problem, arising from the insufficient recogni- tion of facies heterogeneity, is the ongoing confusion in the lithostratigraphic nomenclature. The “ore-bearing dolomite” interval is traditionally, but factitiously divided into three formations (informally also called “beds”, see Figs 2, 3): the Górażdże Formation, the Dziewko wice Formation and the Karchowice Formation. Their names were simply adopted by Siedlecki (1948) from the pioneer lithostratigraphic scheme of Assmann (1913, 1944), proposed for the undolo- mitized Muschelkalk succession, cropping out to the west of the Kraków-Silesia ore district. This scheme was copied, despite the marked lithofacies differences in the two areas. Although several authors highlighted the problem of misuse of these unit names (Gruszczyk, 1956; Śliwiński, 1966a), and Śliwiński (1961) even introduced the term “Olkusz Beds” for the “ore-bearing dolomite” succession, stratigra- phers and miners still apply the lithostratigraphic terms, which have no precise equivalents in the rock record of the Kraków-Silesia region. This paper presents a detailed (bed-by-bed) sedimento- logi cal analysis of the Lower Muschelkalk succession and its lateral variability within the Kraków-Silesia region. On the basis of this large database, this paper also reconstructs step by step the evolution of this part of the Germanic Basin in the Anisian and shows which particuiar events contiib- uted to the formation of the epigenetic “ore-bearing dolo- mite”. The subordinate goal of this paper is to organize the lithostratigraphic scheme of the “ore-bearing dolomite” su- ccession. SEDIMENTARY ENVIRONMENT OF THE EPIGENETICALLY DOLOMITIZED UPPER SILESIAN MUSCHELKALK CARBONATES: A BRIEF REVIEW OF THE LITERATURE In many eariier papers (e.g., Assmann, 1913, 1944; Siedlecki, 1948, 1952; Alexandrowicz and Alexandrowicz, 1960; Śliwiński, 1961, 1966a; Pastwa-Leszczyńska, 1962; Alexandrowicz, 1966, 1971, 1972), the sedimentary envi- ronment of the epigenetically dolomitized Triassic carbon- ates was not discussed at length, because lithostratigraphy was the main focus in those days. Later, Wyczółkowski (1971, 1982) succinctly described the influence of the pre- Triassic morphology on the sediment thicknesses and over- all facies disiribution in the Muschelkalk sea and also re- constructed the particular areas of the Kraków-Silesia re~ gion that were flooded during the sub se quent, transgressive pulses. Pawłowska and Szuwarzyński (1979) and Pawłow- ska (1982, 1985) characterized for the first time the lithofa- cies types, carbonate grains, porosity, diagenetic alterations and sedimentary environment. They concluded that the “ore- bearing dolomite” succession generally represents a tidal-flat environment, but the lower part of the succession (correspon- ding approximately to the Górażdże Formation) was formed in the subtidal zone and the upper part (approximately the un- differentiated Dziewkowice-Karchowice formations), in the inter- and supratidal zones. Subtidal conditions returned to the area during deposition of the oncolites that are widely re- garded as the bottom unit of the overiying Diplopora Beds (Fig. 3). A further attempt to reconstruct the evolution of the Kra- ków-Silesia region in the late Anisian was undertaken by Myszkowska (1992). On the basis of lithological similarities, this author correctly included the undifferentiated Dziewko- wice-Karchowice formations in the overlying Diplopora Beds and divided the latter into three distinct intervals representing different depositional settings. The lower complex (corre- sponding to the undifferentiated Dziewkowice-Karchowice formations) was built of carbonate mudstones, grapestones, peloidal packstones and microbial laminites with mudcracks and birdseyes, which repreiented low-energy, shaliow la- goons and temporarily emerged areas. The middle complex, composed of crinoidal and green algal dolostones as well as oolites and oncolites, was deposited in a shallow marine, hig- her-energy setting. The upper complex commenced with car- bonate muds, grapestones and peloidal packstones, formed in a calm, deeper environment, which upwards pass into oolites and microbial laminites, representing shallow agitated set- tings and emerged areas, respectively. Such a tripartite divi- sion of the Diplopora Beds is also used in the present study. However, several lithological feairres were not recognized by Myszkowska (1992). GEO LOG I CAL SET TING The term “Upper Silesia” refers herein to the entire area of southern Poiand, where Muschelkalk deposits crop out (Fig. 1A). Only in the eastern part of Upper Silesia, called “the Kraków-Silesia region”, these deposits were affected by the epigenetic dolomitization and Pb-Zn mineralization. The western part, termed “the Opole region”, does not show such dolomitization and mineralization. Palaeogeography and tectonic framework In the Middle Triassic, the semi-closed Germanic Basin was situated at subtropical latitudes (Ziegler, 1990; Go- 84 M. MATYSIK limestones early diagenetic dolomites epigenetic dolomites (“ore-bearing dolomite") SUPRATIDAL FACIES cellular (de-)dolomites rhizolites dolocretes mudstones ferricretes INTERTIDAL FACIES cryptalgal laminites SUBTIDAL FACIES shoal sands (mostly grainstones-packstones) tempestites (mostly wackestones-packstones) wavy/nodular calcilutites and calcisiltites firmground omission surfaces (calcilutites) sponge biostromes (bindstones) sponge-coral bioherms (boundstones) COMPONENTS ooids oncoids peloids green algae intraclasts bioclasts (crinoids, bivalves, gastropods, brachiopods, forams) SEDIMENTOLOGY OF THE “ORE-BEARING DOLOMITE” 85 lonka, 2002; Scotese 2003). Communication with the Te- thys Ocean was provided by three fault-controlled seaways, called “gates” (Fig. 1A). This configuration determined the specific overall “Germanic facies” distribution throughout the basin with normal-marine settings prevailing near the gates, and more reitricted environments occurring in the central-to-marginal basin areas (Szulc, 2000). On a smaller scale, however, the basin was filled in a more complex and diverse way, reflecting the unpeneplained post-Variscan to- pography (Wyczółkowski, 1971, 1982) and syndepositional block tectonics (Szulc, 1989). The Upper Silesian Sub-ba- sin, located close to the Silesian-Moravian Gate, dipped to the west. The western part of it (the Opole region) was dom- inated by subtidal facies even during highstands (Szulc, 2000), whereas the eastern part (the Kraków-Silesia region) belonged temporarily to the inter- and supratidal zones (Pa- włowska and Szuwarzyński, 1979; Pawłowska, 1982, 1985; Myszkowska, 1992). The Małopolska Land bordered the Kraków-Silesia re- gion to the SE, but its shore facies is nowhere exposed. The Małopolska Land passed to the NW into an archipelago of several isolated, irregularly scattered, cliff-edged islands, made up of Devonian carbonates. These represent areas of Variscan upiift (Fig. 1B), characterized by differences in size and geometry (Śliwiński, 1966a; Wyczółkowski, 1971, 1982). Intensive erosion of the cliff walls produced a large amount of millimetre- to decimetre-size lithoclasts, most of which were deposited up to 50 m from the isiand margins (Alexandrowicz, 1971; Wyczółkowski, 1971, 1982). The islands formed an elongate belt, 30 by 15 km in size, stret- ching along the Kraków-Lubliniec Fault Zone (KLFZ). The KLFZ is regarded as the place of accretion of two different tectonostratigraphic units, called the Brunovistulikum Ter- rane and the Małopolska Terrane (Żaba, 1999; Buła et al., 2008). Although the accretion took place in the early Pala- eozoic, the KLFZ also was active later. The Variscan Oro- geny caused intense deformation of the KLFZ, including considerable vertical displacement of several tectonic blocks, namely the cliff isiands mentioned above (Śliwiński, 1966a; Wyczółkowski, 1971, 1982). The Mesozoic activity of the KLFZ resulted in synsedimentary tectonic deformation of the accumulated sediments (Szulc, 1989, 2000); seismic pump- ing of hydrothermal fluids also is assumed to have occurred (Heijlen et al., 2003). Stra tig ra phy The evolution of the Upper Silesian Sub-basin in the Mid- dle Triassic was strongly influenced by third-order sea-level fluctuations, superimposed on the differential basin morphol- ogy (Wyczółkowski, 1982; Szulc 2000). Whereas changes in accommodation space generated long-term vertical facies changes, the topography determined the lateral facies distri- bution in particular time intervals. Accordingly, the sedimen- tary succession of the Kraków-Silesia region differs mark edly from the succession of the Opole region. These differ- ences (and similarities) are summarized in Fig. 3. While sim- ple lithostratigraphic correlation cannot be applied, both suc- cessions are well correlated with each other and with the Te- thys domain by magnetostratigraphy (Nawrocki and Szulc, 2000), sequence stratigraphy (Szulc, 2000) as well as cono- dont, ammonoid and crinoid biostratigraphy (Assmann, 1944; Zawidzka, 1975; Hagdorn and Głuchowski, 1993; Kaim and Niedźwiedzki, 1999; Narkiewicz and Szulc, 2004). According to these data, the “ore-bearing dolomite” interval is Pelsonian-Illyrian (upper Anisian) in age (Fig. 3). Horizontal and vertical range of the ore-bearing dol omite The ore-bearing doiomite occupies an area of 50 by 30 km. It is delimited north-eastwards by the KLFZ, westwards by the dislocation running N-S near Blachówka, and south- wards by post-Triass ic eros ion (Fig. 1B; Assmann, 1926, 1944; Śliwiński, 1961). Stratigraphically, the stratiform body of ore-bearing doiomite, approximately 35 m thick, overlies the wavy-nodular clay-rich limestones of the Gogolin Forma- tion (Fig. 3), which formed an impermeable barrier to hydro- thermal fluid flow, migrating downward owing to gravitation (e.g., Bogacz et al., 1970). In contrast, the upper limit of epi- genetic dolomitization is discordant with the lithostratigra- phy and therefore it cannot be identified as one distinct sur- face of lithological change. All earlier authors misidentified the upper limit of dolomitization as the bottom of the Diplo- pora Beds, but in fact the attributes, characteristic for the ore-bearing dolomite (the colour range of oxidised iron, dolomitized texture and/or common dissolution vugs), dis- appear several metres above the bottom of the Diplopora Beds (Fig. 3). The ore-bearing dolomite contains metre- to kilometre- size reli cs of the primary facies of the Muschelkalk lime- stones (Bogacz et al., 1972; Sobczyński and Szuwarzyński, 1974; Mochnacka and Sass-Gustkiewicz, 1978), which can be studi ed today in only a few places. Furthermore, where major dislocations cross each other, the epigenetic dolomiti- zation affected also the Devonian to Jurassic strata (e.g., Ekiert, 1957; Gałkiewicz et al., 1960; Pałys, 1967; Górecka, 1993). For additional information on the dolomitization and mineralization processes in the region, interested readers are referred to the primary literaiure (e.g., Ekiert, 1957; Grusz- <------------------------------------------------------------------------------------------------------------------------------------------------ Fig. 3. Generalized stratigraphic section for the Lower-Middle Muchelkalk of Upper Silesia, showing thickness, overall lithological character, provisional formation names and range of epigenetic dolomitization. M. MU. - Middle Muschelkalk; D. B - Diplopora Beds; TST - transgressive systems tract; HST - highstand systems tract; MFZ - maximum flooding zone; SB - sequence boundary. Sequence stratigraphy framework after Szulc (2000), lithostratigraphy of the Opole region after Assmann (1913, 1944) with later formalization by Bodzioch (1997), Niedźwiedzki (2000) and Kowal-Linka (2008). 86 M. MATYSIK SEDIMENTOLOGY OF THE “ORE-BEARING DOLOMITE” 87 czyk, 1957; Gałkiewicz et al., 1960; Śliwiński, 1962, 1964; Harańczyk, 1965; Pałys, 1967; Smolarska, 1968; Górecka, 1970; Bogacz et al., 1970, 1972, 1975; Zartman et al., 1979; Gruszczyk and Strzelska-Smakowska, 1978; Kozłowski et al., 1980; Szuwarzyński, 1983, 1996; Harańczyk, 1983; Wo- dzicki, 1987; Górecka, 1996; Leach et al., 1996a, b; Viets et al., 1996; Sass-Gustkiewicz and Dżułyński, 1998; Heijlen et al., 2003; Coppola et al., 2009). MATERIALS AND METHODS Out of several tens of investigated outcrops, only the most interesting and complete sections were presented. These are outcrops, where the macrotextural features were affected by epigenetic dolomitization to only a minor extent, and con- sequently sedimentary strucńires or changes in grain size could be recognized. All sections, in which dolomitization obliterated sedimentary structures completely or made it im- possible to distinguish carbonate muds from grains, were ex- cluded. By court esy of the “Olkusz-Pomorzany” lead-zinc mine, three drill cores from the vicinity of the mine were ex- amined. Most of the core intervals were not slabbed, and therefore the measured lithostratigraphic logs may cont ain mistakes. For the GPS coordinates of each outcrop, see the Appendix. Field studies were completed with the analysis of about 900 polished slabs and 400 thin sections. It should be stre- ssed that much of the original rock microtexture had been destroyed as a reiult of epigenetic dolomitization, which significantly limited microfacies description and interpreta- tion. On the other hand, the ubiquitous silica nodules turned out to be a very useful tool in microfacies analysis, because silification prot ected the primary microtextures from epi- ge netic changes. The origin of the chert nodules was descri- bed in detail by Kwiatkowski (2005). For the most complete sections, exhibiting plenty of sedimentary structures, circular histograms (rose diagrams) were constructed to present the frequency distiibutions of inferred local directions of sediment transport (Potter and Pettijohn, 1963; Nemec, 1988). The histograms were cre- ated in the following way: 1) each layer, displaying unidi- rectional cross-bedding, was counted as one azimuth mea- surement (m1); 2) if the top of a layer was shaped by sym- metrical ripples or dunes (bidirectional sedimentary struc- tures), two az imuth measurements were counted (m1 and m2), both perpendicular to the orientation of ripple/dune crests (r1) but each the reverse of the other (m1 =r1+ 90° and m1 = r1 - 90°); 3) planar-bedding and hummocky cross-stratified beds were not counted. The histograms in- clude corrections suggested by Nemec (1988), namely that the area of each circular sector of the rose diagram, not the radius of the sector, is proportional to the class frequency (density). With respect to the geological terminology, “pelolite” is a carbonate rock composed predominantly of peloids (by analogy to oolite and oncolite), independently of whether it had been a limestone or early diagenetic dolomite, prior to epigenetic dolomitization. SED I MEN TARY SUC CES SION OF THE “ORE-BEARING DOLOMITE” The succession of the ore-bearing dolomite consists of four distinct lithostratigraphic intervals, representing differ- ent phases in the evoiution of the Kraków-Silesia Sub-ba- sin. Each interval displays lateral variation in thickness and sedimentary features (Figs 2, 3). These basic lithostratigra- phic units fulfill the recent definition of “Member” (see North American Commision on Stratigraphic Nomencla- ture, 2005; Narkiewicz, 2006). However the definition of formal divisions is beyond the scope of this paper. Unit 1 Unit 1 constitiites the lower half of the Olkusz Beds (sensu Śliwiński, 1961; Figs 2, 3). Lower boundary Unit 1 directly overlies the topmost part of the Gogolin Formation, composed of wavy-nodular clay-rich calcilutites with ubiquitous horizontal trace fossil Rhizocorallium isp., infilled with coproiites (Fig. 4A). These calcilutites in places are interbedded with centimetre-thick bioclastic wackestones- packstones and hummocky cross-stratified calcisiltites. Description Unit 1 is predominantly composed of medium-bedded (10-30 cm), red-brown-grey cavernous dolosiltites with ir- regularly disseminated spots, which exhibit fine-crystalline texture in thin sections (Figs 2, 4B-D). The primary litholo- gical features of these deposits are well preserved in several sections, which escaped the epigenetic dolomitization. <-------------------------------------------------------------------------------------------------------------------------------- Fig. 4. Main lithological features of Unit 1. A. General view of the transition from the wavy-nodular clay-rich calcilutites (the upper- most part of the Gogolin Formation) to the medium-bedded firmgrounds of Unit 1. Imielin - “PPKMiL” Quarry. B. Vertical outcrop view of cavernous spotty dolostone. Black arrow points at flat silica nodule. Imielin - “PPKMiL” Quarry. C. Vertically oriented slab of cavern- ous spotty dolostone. Note that coarse-grained infilling of burrows was dissolved, which resulted in development of vugs. Dąbrowa Górnicza - “Ząbkowice” Quarry. D. Microphotograph of C, illustrating fine-crystalline texture. E. Vertical outcrop view of undolomi- tized firmground horizon with burrows ?Balanoglossites. Note the parallel lamination preserved in some places (white arrow). Płaza - “GiGa” Quarry. F. Vertically oriented slab of two firmground horizons, separated by ?tempestitic pelolite. Lower firmground horizon is reworked to form a conglomerate. White arrows indicate diagenetic haloes formed around burrows (due to mucus-impregnation). Note that only the coarse-grained infilling of the burrows was ahered (recolouration and crysial change) during epigenetic dolomitization, whereas the fine-grained sediment around burrows did not undergo epigenetic changes. Imielin - “PPKMiL” Quarry. 88 M. MATYSIK Fig. 5. Main lithological features of Unit 1. A. Vertical outcrop view of several firmground horizons (firm.; spotty dolostones with some caverns) sandwiched in between pelolites (pel.). Some pelolites display hummocky cross-stratification (black arrow). White arrows indicate hummocks. Pogorzyce - “Żelatowa” Quarry. B. Vertical outcrop view of silicified (on right side) and unsilicified (on left side) fine-grained peloidal packstone-grainstone. Imielin - abandoned quarry. C. Photomicrograph of pelolite, showing coarse-crystalline microtexture enclosing the crinoid ossicle (white arrow). Note that the ossicle margins were dissolved and replaced by dolomite crystals. X nicols. Pogorzyce - “Żelatowa” Quarry. D. Vertical outcrop view of undolomitized peloidal grainstone, displaying moldic porosity and containing sporadic bivalves. Olkusz Stary - abandoned quarry. E-H. Photomicrographs of D. E. Peloidal grainstone with rounded micritic intraclast. Many peloids are dissolved. F. Foram test. G. Cross-section of green algae. H. Peloid with thin ooidal cortex. SEDIMENTOLOGY OF THE “ORE-BEARING DOLOMITE” 89 Fig. 6. Sedimentary structures of Unit 1. A. Vertical outcrop view of large-scale hummocks. Dąbrowa Górnicza - “Ząbkowice” Quarry. B. Vertical outcrop view of dolomitized hummocky cross-stratified pelolite, overiain by firmground. Note several truncated low-angle laminae sets diagnostic of hummocky cross-stratification. Dąbrowa Górnicza - “Ząbkowice” Quarry. C-D. Vertical outcrop views of several dolomitized large-scale cross-stratified peloidal dunes, sandwiching firmgrounds. Note laterally discontinuous firm- ground horizon (white arrows) and resultant amalgamation of two dunes. Dąbrowa Górnicza - “Ząbkowice” Quarry. E. Vertical outcrop view of undolomitized pelolite, displaying high-angle (tabuiar) cross-bedding with tangential reiationship to the basal surface. Olkusz Stary - abandoned quarry. F. Vertically oriented slab of undolomitized laminated fine-grained pelolite. Lamination is slightly disturbed by bioturbation. Płaza - “GiGa” Quarry. 90 M. MATYSIK SEDIMENTOLOGY OF THE “ORE-BEARING DOLOMITE” 91 These are dark grey laminated unfossiliferous calcilutites, with burrows Balanoglossites and Thalassinoides (firm- ground omission surfaces). Parallel lamination was often obliterated by bioturbation (Fig. 4E). The burrows are com- monly surrounded by a black diagenetic halo, which gradu- ally fades away from the burrow wall (Fig. 4F). The bur- rows are infilled either with fecal pellets or yellow detrital sediment, composed of micrite, peloids and sporadic disar- ticulated bivalves. Blocky calcite crysialiized in remnant open voids of burrows. The firmgrounds were sometimes destroyed by submarine erosion to form conglomerates with subrounded pebbles (Fig. 4F). The firmgrounds are iniercai ated with medium-bedded pelolites. Epigenetically dolomitized pelolites are red-brown in colour and display medium- to coarse-crystalline micro- textiire (Fig. 5A-C). They coniain disarticulated crinoids and steinkerns of bivalves and gastropods. Undolomitized pelolites permit more detailed description. These are white calcisiltites and fine- to medium-grained calcarenites (ter- med “crysial” by Siedlecki, 1948; 1952), usually packsto- nes-grainstones and rarely wackestones (Fig. 5D, E). Their main con stitu ents are moderately rounded and sorted pelo- ids, some of which have very thin ooidal cortex (Fig. 5H). Crinoids, bivalves, brachiopods, gastropods, green algae, forams and grey flat micritic pebbles were identified as ac- cessory components (Fig. 5E-G). Many peloids and bio- clasts, except for crinoids, are dissolved (moldic porosity). Whether dolomitized or not, pelolites have clearly visi - ble sedimentary structures and they form single beds or amal- gamated packages. Single pelolitic beds reach up to 50 cm in thickness (mostly 10-30 cm), whereas the amalgamated pe- lolitic packages have usually 0.5-1 m thickness (with a mini- mum of 10 cm and a maximum of 2 m). Both display various sedimentary structures: planar and low-angle lamination, hu- mmocky cross-stratification with hummocks up to 5 m across, tabular cross-bedding, symmetrical ripples 20-40 cm long and 3-8 cm high, as well as dunes 0.6-10 m long and 5-30 cm high (Fig. 6A-E). The ripple and dune crests run generally NE-SW, while the cross-laminae dip dominantly in two op- posite directions: fromN to W and from S to E (Fig. 2). Ver- tical burrows occasionally cut the pelolites, especially where they directly underiie firmgrounds with intensive bioturba- tion (Fig. 6F). The thickness and abundance of pelolites increase stra- tigraphically upwards. This feature is most clearly visible at Imielin (Fig. 2). Lateral variability The firmgrounds that predominate in Unit 1 locally give way to nodular calcilutites-calcisiltites with unidentifiable horizontal trace fossils (Płaza, Olkusz Stary; Fig. 7A), or to flaser-laminated dolosiltites (Bukowno; Fig. 7B). In the vi- cinity of the Devonian islands, the firmgrounds are partially replaced by vertebrate-bearing dolocretes, rhizolites and poorly sorted cliff-breccias to cliff-dolosiltites (Jaroszo- wiec, Nowa Wioska; Fig. 7C-E), or by cavernous unfossili- ferous wavy- to planar-bedded dolostones (Nowa Wioska; Fig. 7F). The latter are made up of alternating 1-cm-thick layers of grey dolosiltite and yeliow peloidal dolarenite, which are frequently affected by bioturbation and occasion- ally cut by erosional channels (1 m wide and 30 cm deep). The pelolites are also characterized by a marked lateral variability. In the most western sections (Tarnowskie Góry), the pelolites constitute only sporadic intercalations within succession of dolomitized firmgrounds, at least 32 m thick, and cortam significant amounts of disarticulated crinoids (Fig. 7G, H). Similarly, the pelolites are almost absent from the easternmost sections, located within the archipelago of Devonian islands (Nowa Wioska, Jaroszowiec). At Imielin, in contrast, the pelolites form exceptionally thick grainstone bodies (up to 2 m in thickness), displaying trough cross-bed- ding. They are sometimes peneirated by vertical, straight or U-shaped burrows, resembling Skolithos isp. and Arenico- lites isp., respectively. The lack of pelolites in the vicinity of the “Olkusz-Pomorzany” Mine should be attributed to the limited possibilities for observation in drill cores, rather than to any real absence of pelolites. The thickness of Unit 1 is laterally variable. In most sections it ranges from 10 to 15 m. However, at Dąbrowa Górnicza it barely reaches 7 m, while at Imielin it is almost 20 m thick, and at Tarnowskie Góry at least 32 m (Fig. 3). Interpretation The lateral variability of Unit 1 described above (Fig. 2) indicates that the Kraków-Silesia Sub-basin was bathyme- trically differentiated in the time interval discussed. Appa- rently, the proximal zone was esiabiished near the archipel- ago of Devonian islands, the medial zone occupied the broad central part of the Sub-basin, and the distal zone occurred at the western flank of the Sub-basin. The proximal zone apparently was dominated by sedi- mentation in a tidal flat system, encompassing salt marshes and emerged areas. This is evidenced by rhizolites and dolo- cretes, respectively. Locally occuring wavy- to planar-bed- ded dolostones, composed of alternating layers of dolosil- <---------------------------------------------------------------------------------------------------------------------------------------- Fig. 7. Regional lithological changes within Unit 1. A. Vertical outcrop view of nodular calcisiltites. Olkusz Stary - abandoned quarry. B. Vertically oriented slab of flaser-laminated dolostone. Bukowno - “Olkusz-Pomorzany” Mine. C. Vertical outcrop view of a rhizolite with small straight root casts. Jaroszowiec - “Stare Gliny” Quarry. D. Vertically oriented slab of noduiar dolocrete, coniaining black lithoclasts of Devonian dolostones. Jaroszowiec - “Stare Gliny” Quarry. E. Close view of nodular dolocrete, containing a bone fragment. F. Vertical outcrop view of wavy- to planar-bedded dolostones. Some bedsets were extensively bioturbated. Nowa Wioska - “PROMAG” Quarry. G. Vertically oriented slab of dolomitized pelolite, coniaining abundant crinoid ossicles. Tarnowskie Góry - “Blachówka” Quarry. H. Detail of G. Crinoid columns and ossicles, extracted from the rock. They are indicative of the late Anisian (Illyrian) silesiacus Biozone. 92 M. MATYSIK Fig. 8. Main lithological feato'es of Unit 2. A. Bedding plane view of dolomitized coarse-grained peloidal grainstone. Bukowno - “Olkusz-Pomorzany” Mine. B. Bedding plane view of dolomitized pelolite, contaming steinkerns of large gastropods. Imielin - “PPKMiL” Quarry. C. Vertical outcrop view of dolomitized pelolite, comprising voids after dissolved bivalve shells, aligned parallel to bedding planes and oriented convex-up. Nowa Wioska - “GZD” Quarry. D. Photomicrograph of pelolite, showing partially recrystallized microtexture of peloidal grainstone. Peloids are well rounded and moderately sorted. Pogorzyce - “Żelatowa” Quarry. E. Photomicro- graph of silicified ooidal grainstone. Imielin - “PPKMiL” Quarry. F. Vertical outcrop view of large sparse cavernous vugs, developed within dolomitized fine-grained pelolite. Nowa Wioska - “GZD” Quarry. SEDIMENTOLOGY OF THE “ORE-BEARING DOLOMITE” 93 tites and dolarenites, 1 cm thick, are very similar to wavy-, flaser- and lenticular-bedded deposits of tidal origin (e.g., Reineck and Singh, 1980; Demicco, 1983; Pratt and James, 1986) and are there fore interpreted as intertidal deposits. This interpretation is further supported by the lack of skele- tal fossils and the presence of abundant burrows, probably created as shelter during the ebb tide. Owing to intensive cliff erosion, the close proximity of the islands is indicated by millimetre- to decimetre-sized lithoclasts of Devonian dolostone, accumul ated as poorly sorted breccias, dolare- nites and dolosiltites. It is clear that vertebrates inhabited this environment, since vertebrate bones were found both in cave-filling sediments (Lis and Wójcik, 1960) and in facies, formed adjacent to cliffs. In the medial zone, including most of the sec tions stud- ied, much of the sedimentation occurred under open-marine low-energy conditions, as indi-ated by the predominant firmground facies. The homogenously laminated structore of the firmgrounds, lacking internal erosional surfaces, im- plies that the carbonate mud was deposited from suspension as single events, presumably after storms (Matysik, 2010). Subsequent development of a firmground omission surface required a prolonged time span in the absence of sedimenta- tion. Firmgrounds are also known to occur in other regions of the Germanic Basin, such as the Holy Cross Mountains, Poland (Kaźmierczak and Pszczółkowski, 1969), the Opole region, Poland (Bodzioch, 1989; Szulc, 2000; Matysik, 2010), and Thuringia, Germany (Knaust, 1998; Bertling, 1999). The pelolitic intercalactions beiween firmgrounds seem to have been mainly of storm origin, because: 1) most occur as single beds within an overall mud-dominated inter- val; and 2) some exhibit the hummocky cross-stratification, diagnostic oftempestites (Fig. 2; Harms etal., 1975; Kreisa, 1981; Walker, 1982; Aigner, 1985; Duke, 1985). Those pe- lolites, which also form single beds, but display tabuiar cross-bedding or dunes, must have been deposited by unidi- rectional, relatively strong, but short-lived currents. Thick amalgamated packages of pelolites (known e.g., from Imie- lin), characterized by various large-scale sedimentary struc- tures, including trough cross-beds, were apparently formed at depths above the normal wave-base. The medial zone generally represents the lower shoreface, affected by unidi- rectional currents, locally evolving into high-energy shoals. The composition of the pelolites suggests that the material came from two different sources. While crinoids, brachio- pods and forams may be considered as an autochtonous, open- marine fauna reworked by storms, the bulk of the coarse- grained material, including peloids, gastropods, green algae and bivalves, must have been delivered from shallower areas of carbonate production, situated certainly eastwards or for- ming local short-term highs, such as at the Imielin site. The general increase in thickness and abundance of pelolite inter- calations within the succession indicates the gradual shallo- wing of the medial zone through time. The disial zone is also interpreted as representing the lower shoreface, although it was separated considerably from the influx of shoal material. Rare pelolite intercaia- tions, rich in disarticulated crinoids and lacking other skele- tal fossils, confirm the presence of more open-marine condi- tions, in comparison with the medial zone (Fig. 2). Unit 2 Unit 2 constitotes the upper half of the Olkusz Beds (sensu Śliwiński, 1961; Figs 2, 3). Description Undolomitized deposits of Unit 2 were not exposed in any of the outcrops investigated. This unit is predominantly composed of beige-red-brown, medium- to coarse-grained pelolites, grainstones-packstones (Figs 2, 8A). In addition to, dominant peloids, disarticulated crinoids, and numerous bi- valves and gastropods occur (Fig. 8B). The (pre-existing) shells are commonly oriented parallel to the bedding, con- vex-up and are mostly dissolved, giving rise to moldic po- rosity (Fig. 8C). In thin sections, the pelolites exhibit me- dium- to coarse-crystalline microtexture. However, occa- sionally the size, shape and arrangement of peloids are recog- nizable, where epigenetic dolomitization affected only the peloids and not the cements or interparticle pores (Fig. 8D). In such cases, the peloids are usually well rounded and mod- erately to well sorted. Observations of the silica nodules un- der the microscope revealed numerous ooids (Fig. 8E), which imply that at least part of the dolomitized peloids had well- developed ooidal cortices, prior to burial diagenesis. The pelolites comprise rare cavernous vugs (sensu Lucia, 1983), which reach 50 cm in size (Fig. 8F). The pelolites (and oolites) form amalgamated packages, several metres thick. Each package shows complex sedi - mentary structures: planar bedding, low- and high-angle (tabular) cross-bedding, trough cross-bedding, herringbone cross-bedding, symmetrical and asymmetrical ripples with small-scale cross-bedding (20-40 cm long and 3-6 cm high), and rare dunes (0.4-5 m long and 10-20 cm high; Fig. 9A-D). The cross-laminae dip dominantly in two oppo- site directions: from N to W and from S to E; however, some bedsets are locally inclined to the NE or SW (Fig. 2). The ripple and dune crests are generally oriented NE-SW. The pelolitic-oolitic pack ages are rarely int erc al ated with beige-red-brown inten-ively bioturbated dolosiltites and fine-grained dolarenites, which range in thickness from 10 to 50 cm (sporadically up to 1 m; Fig. 9E). Unit 2 (and the Olkusz Beds) terminates with a regional disconformity, which marks the Sequence Boundary, de - fined by Szulc (2000). Near the Devonian islands, this boundary is very clearly vis ible as an erosional discon for- mity overiain by onlapping peritidal facies, whereas to - wards the central part of the Kraków-Silesia region, the con- tact is more conformable and hence the sequence boundary is less evident. The exposure of the underlying strata to a meteoric diagenetic environment resulted in the leaching of high-Mg calcite and aragonite, and the resultant develop- ment of non-touching moldic pores (sensu Lucia, 1983; Fig. 5D, E). Moldic porosity was also recognized in the oncoi- dal-peloidal limestones of the Górażdże Formation (Szulc, 1999), which constitutes the stratigraphic equivalent in the Opole region (Fig. 3). The disconformity (sequence bound- ary) probably corresponds to the “erosional surface” recog- nized by Pawłowska and Szuwarzyński (1979) as occurring over the entire area of the currently closed “Trzebionka” lead-zinc mine, in the uppermost part of their unit 5. 94 M. MATYSIK SEDIMENTOLOGY OF THE “ORE-BEARING DOLOMITE” 95 Lateral variability Unit 2 is relatively uniform on a regional scale (Fig. 2), so the only minor local differences need to be emphasized. In the surroundings of the archipelago, Unit 2 is completely devoid of bioturbated fine-grained deposits, which in most sections constitute 10-50 cm thick iniercaiations of peloli- tes. In the vicinity of the “Olkusz-Pomorzany” Mine, in turn, these bioturbated deposits form unusually thick pack- ages (1-2.5 m in thickness), but this may arise from mis- takes made in describing the unslabbed drill cores. Pelolites, occuring in close proximity to the Devonian islands (up to 200 m from the cliff walls) at Nowa Wioska, are usually finer-grained than in the other sections. The sed- iments, situated more than 200 m away from the cliff walls, are dominated by coarse-grained pelolites, often displaying large-scale high-angle cross-bedding and thick laterally- accreted bedsets (Fig. 10A, B). In addition, they comprise well-rounded, cross-laminated pelolitic intraclasts (pebbles to boulders), derived from the underlying lithified pelolites (Fig. 10C). The thickness of Unit 2 is between 6 m (at Jaroszowiec) and 12 m (at Nowa Wioska; Fig. 2). These two sections were located close to two separate Devonian islands, indi- cating the strong influence of local subsidence and/or synse- dimentary tectonics on sedimentary thicknesses. Interpretation The general scarcity of fine-grained sediments and the dominance of pelolites, displaying various large-scale sedi- mentary structures, indicate sedimentation above the normal wave-base. The calcareous sands were predominantly depos- ited by unidirectional strong currents in the upper shoreface setting, as indicated by common trough and tabuiar cross- bedding (e.g., Reading, 1978). After deposition, however, the sand must have been affected by waves, because many rip- ples and dunes have symmetrical shapes. Herringbone cross- bedding within some bedsets indicates deposition from re- versing currents of equal intensity, which implies a tidal ori- gin. The development of ooids also required a contribution of tidal currents (Rankey et al., 2006; Reeder and Rankey, 2009; Rankey and Reeder, 2010, 2011). Planar bedding, typi- cal of upper plane bed conditions, indicates temporary sedi- men-ation in the foreshore (e.g., Reading, 1978). The con- vex-up orientation of shells confirms the high-energy regime; shells deposited from suspension are typically oriented con- vex-down (e.g., Clifton, 1971), but they invert to a more hy- drodynamic ally stable convex-up position, when subjected to current or wave activity (e.g., Brenchley and Newall, 1970). Moreover, low diversity of benthos, represented chiefly by bivalves and gasiropods, also should be attributed to sub - strate unstability, rather than to elevated salinity or oxygen deficiency, because the presence of crinoids indicates nor- mal-marine conditions. In periods of greater substrate stabil- ity, the sandy bottom was uttensively colonized by infauna. Lithification of the carbonate sands was locally rapid, since pebbles to boulders of cross-laminated pelolites were found to be incorporated into younger peloidal sands at Nowa Wioska. However, the overall lack of intraclasts excludes early marine cementation as a common phenomenon. Unit 2 is interpreted to have been a limestone before the epigenetic dolomitization, because: 1) all lithological and sedimeniary features of these deposits attest to a high-en- ergy environment, eliminating the conditions of stagnation and elevated salinity that are responsible for the generation of evaporitive pore fluids and contemporaneous dolomitiza- tion of sediment (Warren, 2000); and 2) it is likely that any hypothetical meteoric waters or hypersaline seawater, infil- trating downward from the regional expo -ure surface or onlapping the peritidal areas, also would have penetiated further down through the limestones of Unit 1. This was not the case, because Unit 1 displays no epigenetic alteration. Unit 3 Unit 3 overiies the regional disconformity mentioned above (Figs 10B, 11A, B), which is regarded as the sequen- ce boundary (Szulc, 2000). The unit approximately corre- sponds to the “lower complex” of the Diplopora Beds sensu Myszkowska (1992; Figs 2, 3). Description The most characteristic lithofacies of Unit 3 are yellow cryptalgal laminites (planar stromatolites; Fig. 2). They are composed of alternating millimetre-thick laminae of micro- bial and detrital origins. The microbial laminae display dense aphanitic (minor clotted-micropeloidal) microfabric, whereas the detrital laminae are composed of silt- to mud- size lime particles (Fig. 11C, D). The lamination is more-or- less straight and parall el to the bedding planes. However, layers of laminae are often truncated and discordantly capped by other stromatolitic layers. In some cases, the lamination is barely seen, owing to a reduced contiibution of microbial mats. Laminitic layers are commonly torn up into intra- clasts, which may be incorporated into the successive lami- nations or form conglomerates and breccias (Fig. 11C). Flat and rounded intraclasts may be imbricated (Fig. 11E). The cryptalgal laminites occa-ionally coniain fenestral pores, sheet cracks and mudcracks (Fig. 11F), but this facies is ge- nerally non-porous. Small gasiropods can be found within the laminations. <------------------------------------------------------------------------------------------------------------------------------------ Fig. 9. Sedimentary structures of Unit 2. A. Vertical outcrop view of tabular cross-bedded pelolites alternated by planar-bedded ones. Pogorzyce - “Żelatowa” Quarry. B. Vertical outcrop view of small-scale cross-bedded pelolites, sandwiched between fair-weather fine-grained epigenetic dolostones (black arrows), capped by planar-bedded, coarse-grained pelolite. Imielin - abandoned quarry. C. Ver- tical outcrop view of symmetrical pelolitic dunes (white arrows). Nowa Wioska - “GZD” Quarry. D. Vertical outcrop view of trough cross-bedded, coarse-grained pelolite. Imielin - abandoned quarry. E. Vertical outcrop view of planar-bedded, coarse-grained pelolite. Distinct bioturbation in the upper part. Pogorzyce - “Żelatowa” Quarry. 96 M. MATYSIK Fig. 10. Sedimentary structures of Unit 2. Nowa Wioska - “GZD” Quarry. A. Vertical outcrop view of high-angle cross-stratification with tangential reiationship to the basal surface. Hammer for scale is 30 cm long. B. Vertical outcrop view of laterally accreting large-scale pelolitic bedsets, truncated during emersion and capped by peritidal facies. C. Vertical outcrop view of cross-stratified, coarse-grained pelolites containing numerous reworked pelolite intraclasts. White arrow points at 40 cm long cross-laminated intraclast of pelolite, black arrows point at smaller ones. Hammer for scale is 30 cm long. SEDIMENTOLOGY OF THE “ORE-BEARING DOLOMITE” 97 Dolocretes, rhizolites and mudstones are also indicative of Unit 3 (Fig. 2). The dolocretes, yeliow-orange-green- grey dolosiltites, create centimetre- to decimetre-thick crusts, resting usually on top of irregular subaerially weath- ered surfaces (Fig. 12A). Most dolocretes show noduiar fabric, composed of microspar (Fig. 12B). Some dolocretes are structureless (mass ive) and cont ain peloids of dense aphanitic automicrite, embedded within allomicrite or mi- crospar (Fig. 12C). The dolocretes are sporadically rewor- ked to form breccias. The rhizolites, on the other hand, are beige-green massive dolosiltites with centimetre-long verti- cal, straight or bifurcating root casts (Fig. 12D). The amount of root casts usually increases upward within a rhi- zolite layer and consequently its topmost part contains a complex network of filiform voids. Root peneiration never exceeds 15 cm depth. The rhizolites may contain single centi- metre-sized lenses of sulphates (Fig. 12E, F). In turn, the mudstones are green and laminated. They form centi- metre-thick layers, capping irregular, subaerially weathered surfaces. In thin sections, one can observe rounded quartz grains and muscovite plateiets, scattered in carbonate mud (Fig. 12G, H). The layers of cryptalgal laminites, dolocretes, rhizolites and mudstones are horizontally discontinuous on a local scale (within one outcrop) and all these lithofacies can pass laterally into each other. They form decimetre- to metre- thick packages, which pinch out laterally on a regional scale (tens of kilometres), but in places on a local scale, as well. The lateral persistence of lithofacies and the high-frequency cyclicity will be discussed in a separate paper. The packages of cryptalgal laminites, dolocretes, rhizo- lites and mudstones are intercalated with decimetre- to me- tre-thick packages of bioturbated dolosiltites and/or pelo- lites (Fig. 3). The bioturbated dolosiltites are yeliow-or- ange-grey cavernous, unfossiliferous rocks with irr egul ar spots, atthough some bedsets include Thalassinoides isp., instead of irreguiar spots (Fig. 13A, B). Under the micro- scope, one can sometimes recognize micrite and microspar, but usually the microfabric is epigenetically dolomitized. On the other hand, the pelolites are yellow-orange-grey do- losiltites and fine- to medium-grained dolarenites, grainsto- nes-packstones, which usually display medium- to coarse- crystalline microtexture (Fig. 13C). Locally, flat and well- rounded lithoclasts of cryptalgal laminites are embedded, especially at the contacts with the underlying laminites. Green algae are most common amongst the scarce skeletal fossils (Fig. 13D). The pelolites show various, albeit rare, sedimentary structures: planar bedding, low- and high-an- gle cross-bedding, trough cross-bedding as well as dunes 0.5-1.5 m long and 5-10 cm high (Figs 2, 13E). Sedimen- tary structures are in places disturbed by burrows Thalassi- noides. Lateral variability As described above, Unit 3 is made up of packages of cryptalgal laminites, dolocretes, rhizolites and mudstones, alternating with packages of pelolites and bioturbated dolo- siltites. The thickness of the former packages usually does not exceed 1 m in most sections. It reaches only 20 cm in Li- biąż and Jaroszowiec, and 1-3 m at Nowa Wioska (Fig. 2). Furthemore, at Nowa Wioska, these packages are occasion- ally cut by tidal channels, reaching 20 m in width and 3 m in depth. The pelolites, filling the channels, accreted trans- versely with respect to the main direction of tidal-channel propagation and sometimes contain angular lithoclasts of dolosiltites, dolocretes and Devonian dolostones (Fig. 13G). The pelolites at Libiąż comprise abundant flat and roun- ded lithoclasts, aligned more-or-less parallel to the bedding planes (Fig. 13F). The lithoclasts are composed of micro- spar, and contain rare forams. This kind of deposit has not been found in situ at Libiąż, so the lithoclasts must have been transported from outside. The thickness of Unit 3, reaching 10-14 m in most sec- tions, is reduced to 5-7 m at Dąbrowa Górnicza, Bukowno and Jaroszowiec (Fig. 2). These three sections were situated close to two Devonian isiands and experienced a simiiar evolution, controlled by local subsidence. Unit 3 pinches out to the west and is totally absent at Tarnowskie Góry. Interpretation The dolocretes and mudstones are interpreted as having formed in the supratidal zone, on emerged banks and peri- pheral plains of tidal flats. Dolocretes are a widely accepted indii ator of semi-arid and arid conditions (Esteban and Klappa, 1983). However, the scarcity of evaporites seems to exclude intense evaporation in this case. The rhizolites also could have been formed in permanently emerged areas, but they may represent intertidal salt marshes, as well (Shinn et al., 1969). Only small plants grew in these areas, as indi- cated by the small size of the root casts. This may be due to a relatively arid climate and/or substrate instability (e.g., due to the ac tiv ity of tidal currents). The cryptalgal laminites formed in the intertidal zone of tidal flats, as a consequence of the trapping of carbonate mud by microbial mats (Ginsburg, 1960; Fischer, 1964; Kendall and Skipwith, 1968; Shinn et al., 1969; Hardie, 1977; Kinsman and Park, 1976; Shinn, 1983; Alsharhan and Kendall, 2003; Rankey and Berkeley, 2012). The mud was apparently deposited from suspension in a relatively calm environment, as evidenced by the straight laminations. Lack of bioclasts and coarse sediment may reflect a larger dis- tance to the subtidal zones and/or limited storm-generated transport (e.g., Pratt and James, 1986). However, the area was not completely separated from high-energy processes. Tidal currents were most likely responsible for truncation of the laminite layers and for pro duc ing intraclasts. Lo cally, intense reworking resulted in decimetre-thick breccias and conglomerates (e.g., at Nowa Wioska). The non-porous fab- ric of the cryptalgal laminites indicates that the deposit was regularly flooded, without prolonged desiccation; otherwise this facies would comprise abundant mudcracks, sheet cracks or fenestral pores (e.g., Fischer, 1964; Shinn, 1968), which is not the case. The gastropods, found within lamini- tes, are interpreted as in situ accumulations of mat-grazing organisms. The bioturbated dolostones are inierpreted as shaliow subtidal sediments, deposited in areas protected from vigor- ous tidal currents. The thinner units of bioturbated dolosto- nes might have been formed in ephemeral tidal ponds (e.g., Shinn et al., 1969; Rankey and Berkeiey, 2012), whereas 98 M. MATYSIK SEDIMENTOLOGY OF THE “ORE-BEARING DOLOMITE” 99 the thicker ones were more likely to have been deposited in lagoons and embayments (e.g., Kendall and Skipwith, 1969; Purser and Ev -ns, 1973; Alsharhan and Kend-ll, 2003). The absence of skeletal fossils indicates restricted life conditions with probably elevated salinity, however, al- lowing pervasive bioturbation. Thalassinoides isp. indicates good oxygenation of the deposit (e.g., Rhoads, 1975; Sav- rda and Bottjer, 1986; Savrda, 2007). The pelolites are interpreted as representing the shallow subtidal zone, as well. Some of the peloids were transported into high-energy conditions (bars or shoals), as indicated by occasional current cross-bedding. However, most of the pe- loids were accumulated in relatively tranquil, albeit gener- ally mud-free areas. The overall paucity of skeleial fossils again seems to reflect elevated salinity. The cyclic alternation of supra-intertidal facies and shallow subtidal facies proves that Unit 3 represents a tidal flat system, which periodically experienced longer periods of submersion. The frequency of these changes vari ed be- tween the sites (depending on the relative distance to the open sea in the west and differring subsidence rates), indi- cated by regionally variable thicknesses of the lithofacies packages (Fig. 2). The surroundings of Nowa Wioska ap- parently were occupied by tidal flats for a relatively long time, because here the packages of supra-intertidal facies commonly reach 1-3 m in thickness. In conirast, the other areas underwent geomorphic changes more frequently, re- corded as thinner and more frequent intercalations of differ- ent peritidal facies. All tidal flats showed a distinct morpho- logical differentiation and encompassed co-existing cyano- bacterial mat flats, salt marshes and emerged areas, as evi- denced by supra- and intertidal lithofacies passing laterally into one another. Locally, the tidal flats were cut by tidal channels. Carbonate mud was deposited in protected, shal- low subtidal areas (ephemeral tidal ponds, and lagoons or embayments of longer existence), whereas peloidal sands characterized high-energy settings (bars or banks). By analogy to many Phanerozoic successions (e.g., Fi- scher, 1964; Pratt and James, 1986; Adams and Grotzinger, 1996; Bädenas et al., 2010) and modern sedimentary analo- gues (e.g., Illing et al., 1965; McKenzie, 1981; Shinn, 1983), the supra- and intertidal facies of Unit 3 are inierpreted as early diagenetic dolostone, which subiequently underwent epigenetic dolomitization. The subtidal fac ies might have been a limestone; however, it is more likely that they were dolomitized in their early diagenetic history by continenial groundwater or hypersaline seawater, percolating downward from prograding supra- and intertidal areas (Warren, 2000). Unit 4 Unit 4 approximately corresponds to the “middle com- plex” of the Diplopora Beds sensu Myszkowska (1992; Figs 2, 3). Description In many sections, the upper limit of epigenetic dolomi- tization occurs within Unit 4 and therefore its lower part is characterized by orange colours and crysialiine microtex- ture, whereas the upper part has yellow colours and preser- ved the original microtexture much better (although altered by early diagenesis). Notwithstanding these differences, Unit 4 is predominantly composed of medium- to thickly- bedded (10-100 cm) pelolites, grainstones-packstones (Fig. 2). These are fine- to coarse-grained dolarenites and sporadically dolosiltites, some of which coniain disarticu- lated crinoids, bivalves, gasiropods and green algae (Fig. 14A-C). Peloids are mostly well rounded and moderately sorted. The pelolite beds hardly ever display internal cross- bedding (trough cross-bedding, herringbone cross-bedding, planar bedding). However, the tops may be shaped in the form of symmetrical ripples (10-20 cm long and 3-5 cm high) or dunes (0.4-1.5 m long and 5-10 cm high; Fig. 14D, E). The crestlines of ripples and dunes run generally NE- SW (Fig. 2). Locally, the pelolites comprise a well-devel- oped network of burrows Balanoglossites or Thalassinoi- des, which may completely alter the sedimeniary fabrics (Fig. 14F, G). Decimetre- to metre-thick packages of pelo- lites are intercalated with bioturbated dolosiltites, which of- ten cont ain cavernous vugs and the ichnofacies mentioned above. Lateral variability Unit 4 is relatively uniform on a regional scale. It has a thickness of 9-12 m, except at Pogorzyce, where it reaches 15 m (Fig. 2). The bioturbated dolosiltites, constituting sub- ordinate intercalations of thick pelolitic packages in most sections, form units 1.5-2.5 m thick at Dąbrowa Górnicza and Bukowno. Upper boundary Unit 4 is overlain by an oncolitic package 5-10 m thick and regarded as a correlation horizon across the entire Kra- ków-Silesia region (Alexandrowicz, 1971; Bilan and Go- lonka, 1972). At Nowa Wioska and Libiąż, however, Diplo- pora (green algal) grainstones occur in-tead of oncolites (Fig. 2). <-------------------------------------------------------------------------------------------------------------------------------------- Fig. 11. Main lithological feaUjres of Unit 3. A. General view of subaerially exposed upper shoreface-foreshore facies of Unit 2, onlapped by peritidal facies of Unit 3. The disappearance of the inter- and supratidal facies in the succession marks the lower boundary of Unit 4. Nowa Wioska - “GZD” Quarry. B. General view of the peritidal facies capping the subtle platform topography. Nowa Wioska - “GZD” Quarry. C-F. Intertidal facies of Unit 3. C. Vertically oriented slab of reworked cryptalgal laminite (upper part) capping laminite in place. Nowa Wioska - “GZD” Quarry. D. Photomicrograph of cryptalgal laminite: darker microbial laminae alternate with more trans- parent detrital ones. Bolęcin - “Skała Bolęcka” Quarry. E. Vertical outcrop view of imbricated intraclasts (white arrow) within cryptalgal laminite. “Libiąż” Quarry. F. Bedding plane view of mudcracks developed within cryptalgal laminite. Hammer for scale is 30 cm long. Pogorzyce - “Żelatowa” Quarry. 100 M. MATYSIK SEDIMENTOLOGY OF THE “ORE-BEARING DOLOMITE” 101 Interpretation The overall predominance of pelolites over fine-grained sediments indicates that sedimentation took place in a shal- low-marine environment, in which the energy was high enough to winnow calcareous mud to more quiescent zones of the basin and produce grain-supported textures. Because current cross-bedding is uncommon in these deposits, wave action is considered to have been the principal factor in- volved in removing the mud. Relatively abundant symmet- rical ripples and dunes corroborate this interpretation. It is likely, therefore, that the area was protected from the influ- ence of strong currents, but was subjected to wave activity. Common green algae confirm the transparency of the water column and at least periodic stability of the substrate. The crinoids indicate normal marine conditions. Although peloidal sedimentation dominated in the Kra- ków-Silesia region, mud sedimentation was locally of great importance (at Bukowno and Dąbrowa Górnicza). The completely bioturbated nature of these muds and the occu- rence of Thalassinoides isp. indicates good oxygenation of the deposits (e.g., Rhoads, 1975; Savrda and Bottjer, 1986; Savrda, 2007). The upper part of Unit 4, not affected by the epigenetic dolomitization, is characterized by a relatively stable MgO content (19-21%), as compared to the typical “ore-bearing dolomites” (Śliwiński, 1966b). A simiiar stability of MgO content is also characteristic of the Röt dolostones and the Middle Muschelkalk dolostones, widely regarded as early diagenetic dolomites (e.g., Śliwiński, 1966b). Unit 4 is therefore interpreted to have been a limestone which firstly underwent the early diagenetic dolomitization, and then its lower part was replaced by the epigenetic dol omite. The most probable mechanism of the early dolomitization was the reflux of Mg-rich brines from the shallower parts of the platform (Warren, 2000). LONG-TERM EVOLUTION OF THE KRAKÓW-SILESIA SUB-BASIN The long-term facies succession of the Kraków-Silesia Sub-basin reflects third-order transgressive-regressive pul- ses, which strongly conirolled both depth (energy regime) and siliciclastic input (Szulc, 2000). The topmost part of the Gogolin Formation, composed mainly of the wavy-nodular, clay-rich Rhizocorallium-bearing calcilutites, represents sedimentation in fully marine conditions, under a signif- cant influx of terrigenous material and at depths below the storm wave-base (offshore). Sporadic intercalations of bio- clastic wackestones-packstones and hummocky cross-strati- fied calcisiltites re -ulted from severe storms, rather than high-frequency sea-level fluctuations (Matysik, 2012). The disappearance of these strata indicates major chan- ges in sedimeniation style within the Kraków-Silesia Sub- basin. First of all, the Sub-basin became isolated from terri- genous influx, as shown by the total absence of siliciclastics within Unit 1. This implies that the broad areas of the neigh- bouring Małopolska Massif became flooded. The cessation of terrigenous input was not synchronous, but migrated dia- chronously from the SW to NE: the wavy-nodular, clay-rich limestones disappear first in the western- and southernmost sections (Tarnowskie Góry and Imielin, respectively), and only later in the eastern sections (Dąbrowa Górnicza, Bu- kowno; Fig. 2). Secondly, the general sedimentation charac- ter changed from rel-tively con-tant to highly epiiodic, since the uniform wavy-nodular Rhizocorallium-bearing limestones were replaced by Balanoglossites and Thalassi- noides firmgrounds. In addition, the bioclast-dominated tempestites were totally replaced by peloid-dominated ones, containing only subordinate amount of skeletal fossils. This change suggests massive redistribution of peloids from the adjacent shallow-water sources, which might have been caused by a significant expansion of “carbonate factories”, probably due to the widespread flooding of land areas. On the basis of these considerations, the boundary between the Gogolin Formation and Olkusz Beds is regarded herein as the Maximum Flooding Surface (MFS). The Olkusz Beds, overlying the MFS, displays a shoal- ing-upward trend, the transition from lower shoreface facies (Unit 1) via upper shoreface-foreshore facies (Unit 2) to the final emersion. Such a regressive trend is typical of high- stand system tracts (e.g., Catuneanu et al., 2010). Unit 1 it- self also shows a shallowing-upward tendency, expressed by the increasing thickness and abundance of pelolitic inter- caiations within the firmground suc-es-ion. Some areas, such as the Imielin site, already rose above the normal wave base during this time, evidenced by 2 m thick pelolitic pack- ages that exhibit various high-energy sedimentary structu- res including herringbone cross-bedding. As a result of the progressive filling of the sub-basin (and possible a third-or- der eustatic sea-level drop), the whole Kraków-Silesia re- gion finally rose up to and above the normal wave base and consequently sedimentation of high-energy peloidal-ooidal sands (Unit 2) commenced. The maj or unknown is how many peloids had been ooids, prior to the epigenetic dolo- mitization. On the basis of microscopic observations of the silica nodules, some pelolites clearly contain abundant ooids and should be classified therefore as oolites (Fig. 8E). In addition, the pelolites that display only partially obliter- ated microtexture are composed of well rounded, well <----------------------------------------------------------------------------------------------------------------------------- Fig. 12. Supratidal facies of Unit 3. A. Bedding plane view of dolocrete crust. Dąbrowa Górnicza - “Ząbkowice” Quarry. B. Vertically oriented slab of nodular dolocrete. “Libiąż” Quarry. C. Vertically oriented slab of structureless dolocrete, containing automicritic peloids and lithoclasts (white arrows). “Libiąż” Quarry. D. Vertically oriented slab of a rhizolite with small vertical root casts. “Libiąż” Quarry. E. Vertically oriented slab of nodular evaporite occuring within a rhizolite layer. Nowa Wioska - “GZD” Quarry. F. Photomicrograph of E, showing sulphate crystals. G. Vertical outcrop view of two greenish mudstone layers, separating whitish fine-grained pelolites. Nowa Wioska - “GZD” Quarry. H. Photomicrograph of G, illustrating quartz grains (white arrow) scattered in carbonate matrix 102 M. MATYSIK SEDIMENTOLOGY OF THE “ORE-BEARING DOLOMITE” 103 sorted peloids (Fig. 8D), which resemble the Recent ooids forming in the tidal deltas and banks of the Bahamas (Ran- key et al., 2006; Reeder and Rankey, 2009; Rankey and Reeder, 2010, 2011). It is possible that most of the pelolites discussed were originally oolites. If this were to be the case, the waiers of the Kraków-Silesian Sub-ba-in must have been oversaturated with respect to carbonate and strongly agitated (e.g., due to the daily activity of tidal currents) to produce ooids (Rankey and Reeder, 2009; Duguid et al., 2010). Such an interpretation is further corroborated by the presence of herringbone cross-bedding, indicative oftidally influenced settings. Sedimentation of the Olkusz Beds was terminated by the emersion event. Its imprint on the underlying strata can- not be restored in detail because of the pervasive epigenetic dolomitization. Nevertheless, exposure to a meteoric-diage- netic environment certainly led to the leaching of aragonitic or high-Mg calcitic grains (peloids, ooids and bioclasts ex- cept for crinoids), as evidenced by the ubiquitous moldic porosity (Fig. 5D). It is noreworthy that the moldic pores (clearly visible both macro- and microscopically) are pre- served only in the undolomitized deposits of the Olkusz Beds. This proves that the dolomitization process was re- sponsible for the infilling of the pores by cement. The pores generally disappear near the lower boundary of the Olkusz Beds, indicating exposure of the entire formation and a sea-level drop of about 20-25 m. However, the possibility of a larger-scale regression cannot be excluded, and the lack of the diagnostic moldic pores within the underlying Gogolin Formation may have arisen from its difierent li- thology (wavy-nodular clay-rich calcilutites and occasional bioclastic tempestites), which was much less susceptible to meteoric dissolution. The emersion event discussed was ap- parently too short to produce an extreme karstic topography or even small-scale karst feaiures. In addition, limited an- nual precipitation typical of subtropical latitudes did not fa- vour iniense karstification (James and Choquette, 1988; Wright and Smart, 1994). Only at Nowa Wioska, peritidal facies transgressed onto a system of low-relief (1-3 m high and up to hundreds of metres across) morphologic depres- sions and elevations (Fig. 11 A, B). No lag deposits, con- taining fragments of reworked basement, have been found, which argues against the complete erosion of the hypotireti- cal, pre-existing karstified sediments. The regional disconformity, marking the sequence boundary, is capped by peritidal facies (Unit 3 of the Diplo- pora Beds), which represent a tidal flat-lagoonal system es- tablished during the initial phase of transgression (Figs 10B, 11A, B). This system included a belt of channelized supra- tidal plains and banks, cyano-bacierial mat flats, salt mar- shes and possibly tidal ponds, which was flanked seawards (westwards) by a belt of low-energy mud-dominated la- goons and embayments, separated from each other and shel- tered from the open sea by high-energy peloidal bars and shoals. As a result of high-frequency changes in accommo- dation space (whatever its origin), both belts migrated later- ally and consequently encroached upon one another. This produced metre-scale cyclicity, clearly observable in verti- cal profiles (Figs 2, 11A). Despite the similarities, each lo- cality displayed some sedimentological differences, for ex- ample, contiasts in thicknesses of the supra-intertidal and subtidal packages (Fig. 2), or the occurrence of additional lithofacies or grain types (Fig. 13F). The overall lack of evaporites in the sysiem may reflect relatively humid cli- mates, resulting from a monsoonal influence (e.g., Parrish and Peterson, 1988; Kutzbach and Gallimore, 1989; Van der Zwaan and Spaak, 1992; Parrish, 1993), or the prox im- ity of the Tethys Ocean. Nevertheiess, the common devel- opment of dolocrete crusts implies at least temporary semi- arid conditions (Esteban and Klappa, 1983). As a consequence of the progressive transgression, the tidal flat system became ultimately submerged and the Sub- basin entered into a shallow subtidal zone, dominated by the accumulation of peloidal sands (Unit 4). The high-energy regime of this time controlled the overall paucity of carbon- ate mud. Apparently, the mud was removed to the basinal areas by wave action, as indicated by the general absence of current cross-bedding. The transparent waters and periodi- cally stable substrate enhanced massive growth of fragi le green algae requiring light. The period of maximum flooding in the third-order transgressive-re gressive pulse discussed seems to be ex- pressed in the deposition of oncoidal and green algal sands, widely distributed across the Kraków-Silesia Sub-basin (Bi- lan and Golonka, 1972; Alexandrowicz, 1971; Myszkow- ska, 1992; this study). These strata are capped by about 25 m of peritidal facies (Fig. 3), which correspond to the “up- per complex” of Myszkowska (1992). Important information regarding the palaeogeography and evoiution of the Kraków-Silesian Sub-basin was ob - tained from the analysis of the sedimentary structures. In- spection of the circular histograms revealed that for most sections the azimuth pattern is bipolar, with both modes more-or-less equally rep-e- ented, which indicates a tidal and/or wave origin (Fig. 15). Furthermore, in the sections located outside the archipelago of the Devonian islands, the <--------------------------------------------------------------------------------------------------------------------------------------- Fig. 13. Subtidal facies of Unit 3. A. Vertical outcrop view of spotted cavernous dolostone. Note that cavernous vugs are chiefly devel- oped within dark grey irreguiar spots. Nowa Wioska - “GZD” Quarry. B. Vertical outcrop view of Thalassinoides-bearing dolosiltite. Nowa Wioska - “GZD” Quarry. C. Photomicrograph of pelolite, showing dolomitized microtexture of peloidal packstone. Despite crystal growth, particular peloids are still visible. Pogorzyce - “Żelatowa” Quarry. D. Vertical outcrop view of algal debris. White arrows point at well preserved tubes of green algae. “Libiąż” Quarry. E. Vertical outcrop view of trough cross-bedded, coarse-grained pelolite. Nowa Wioska - “GZD” Quarry. F. Vertically oriented slab of fine-grained pelolite, containing flat and rounded microsparite intraclasts (black arrows) and pelolitic intraclasts (white arrow). “Libiąż” Quarry. G. Vertical outcrop view of tidal channel, filled by peloidal sands and cutting various peritidal facies. Nowa Wioska - “TRIBAG” Quarry 104 M. MATYSIK SEDIMENTOLOGY OF THE “ORE-BEARING DOLOMITE” 105 sediment was clearly transported in a NW-SE direction, which seems to re flect the regional palaeocurrent pattern, controlled by the orientation of the palaeoshoreline. In the sections situated within the archipelago, in turn, the local di- rections of sediment transport diverge from the anticipated general one and tend to follow the geometry and orientation of the adjacent Devonian islands. It is also noteworthy that the majority of ripples and dunes over the entire area display different types of cross-bedding, resulting from unidirec- tional current flow, but they have a symmetrical shape, cre- ated by the oscillatory motion of bottom waters. This sug- gests that the sedimentary structtures, formed in the initial stage as a response to current flow, were commonly remo- delled in the final stage by waves. REMARKS ON THE EPIGENETIC DOLOMITIZATION PROCESS IN THE KRAKÓW-SILESIA ORE PROVINCE From comparisons of the undolomitized and “early do- lomitic” lithologies with their epigenetically dolomitized counterparts (especially in Unit 1), it may be concluded that the migrating dolomitizing fluids caused three main chan- ges in the original rock fabric: colour change, replacement by growing dolomite crystals, and the creation of porosity. On a regional scale, the degree of alteration depended on the dist ance to the main zones of fluid flow, the fault zones (Bogacz et al., 1970; Gałkiewicz, 1971; Kibitlewski and Górecka, 1988; Górecka, 1993; Kibitlewski, 1993). On a lo- cal scale, it depended on the depositional facies of particular lithologies, which in turn strongly controlled their porosity and permeability. In other words, in the same area, the pro- cess of epigenetic dolomitization modified different litholo- gies in different ways. With respect to the intensity and type of change, the lithologies de scribed may be grouped into three general categories: 1) cryptalgal laminites and emer- sion-related deposits; 2) coarse-grained deposits (mostly pelolites); and 3) bioturbated fine-grained deposits (mostly firmgrounds). The cryptalgal laminites and emersion-related deposits The cryptalgal laminites and emersion-related deposits, characieri stic of Unit 3 and inierpreted as early diagenetic dolomites prior to burial diagenesis, were afiected by the epigenetic changes only locally and to a minor ext ent. In most sections, the original light colours (yellow, beige, or- ange, grey and green) are preserved, the fine texture is not dolomitized at all, and only sporadic and scattered small vugs are present. In sections situated close to the maj or faults (e.g., at Libiąż), the cryptalgal laminites have oran- geish colours and indistinct biolamination; however, they are still less altered than the other deposits at the same loca- tion. The overall lack of alteration indicates that the strati- graphic ho ri zons, composed of the cryptalgal laminites and emersion-related deposits, were not used as major routes of bed-parallel migration by the fluids causing burial dolomiti- zation. The coarse-grained deposits The coarse-grained deposits are epigenetically dolomi- tized in most sections. The original white-grey pelolitic limestones with ubiquituous moldic porosity and frequent skel etal fos sils (Unit 1 and Unit 2), and yellow-orange-grey pelolitic ?early diagenetic dolostones with scarce fosiils (Unit 3 and Unit 4) were alt ered into beige-orange-red- brown epigenetic dolomites, displaying medium- to coarse- crysialiine microtexture and coniaining steinkerns of mol- lusks as well as occasional cavernous vugs, up to 50 cm across. Among the several types of change, dolomitization is the most obvious. In the maj ority of cases, it is not mani- fested macroscopically and accordingly sedimentary struc- tures or individual grains can be easily distinguished. In- stead, the process is visible under the microscope as a ho- mogenous mass of dolomite crystals (Fig. 5C).In rare cases, where dolomitization was not very advanced, the dolomite crystals replaced exclusively peloids, without affecting the cements and interparticle pores (Fig. 8D). This clearly shows that the development of a crystalline microtexture started inside the grains, whereas the cements or interpar- ticle pores were involved only at the end. According to Heijlen et al. (2003), the dolomitization process occurred in two separate stages: 1) the precipitation of iron-poor dolo- mite crystals (dolomite generation I); and 2) the crystalliza- tion of iron-rich dolomite rims (dolomite generation II) around the doiomite crysials of generation I. The presence of iron-rich dolomite rims also explains the typical colours of the ore-bearing dolomite. Although doiomite cements fill many moldic pores, many of the biomolds remained open (Fig. 8B, C) and some of them were even enlarged during the dolomitization pro- cess to form larger vugs (Fig. 16A). The origin of the large (50 cm across) cavernous vugs is problematic. They occur sporadically and without any particular pattern of distribu- tion (Fig. 8F). <----------------------------------------------------------------------------------------------------------------------------------- Fig. 14. Main lithological features of Unit 4. A. Bedding plane view of coarse-grained peloidal packstone with sparse crinoid ossicles (white arrow). Pogorzyce - “Żelatowa” Quarry. B. Photomicrograph of A, showing well rounded and poorly sorted peloids. Note the be- ginning dolomitization of the texture. C. Bedding plane view of fine-grained peloidal packstone, containing frequent green algae (white arrows) and rare gastropods (black arrows). Nowa Wioska - “GZD” Quarry. D. Bedding plane view of symmetrical ripples. Dąbrowa Górnicza - “Ząbkowice” Quarry. E. Vertical outcrop view of medium-grained peloidal packstone, displaying herringbone cross-bedding. White arrows indicate direction of sediment transport. Pogorzyce - “Żelatowa” Quarry. F. Polished slab along bedding plane (bp) and cross-section (cs), illustrating dense network of the trace fossil Balanoglossites in three-dimensional view. “Libiąż” Quarry. G. Vertically oriented slab of planar-bedded fine-grained peloidal packstone containing Balanoglossites. Note that burrows form several well-devel- oped horizons (black arrows), which are connected and cut by sporadic vertical canals. “Libiąż” Quarry. 106 M. MATYSIK Fig. 15. Azimuths of sediment transport plotted in circular histograms. The model rose diagram is given at the bottom right of the figure. Azimuth measurements for each section are depicted in Fig. 2. Note that the NW-SE direction of sediment transport predominates in most outcrops, but was modified to roughly N-S and E-W directions by the elongated, NE-SW-striking Devonian horst, which divides the “GZD” Quarry in Nowa Wioska (and the Triassic carbonates) into two parts The bioturbated fine-grained deposits The bioturbated fine-grained deposits are dolomitized in most sections and occur as orange-red-brown cavernous dolosiltites with irregular spots, exhibiting a fine-crystalline microtexture. These dolomites replaced the orig inal dark grey laminated unfossiliferous calcilutites with common burrows Balanoglossites and Thalassinoides, infilled with yellow detrital sediment and blocky calcite (Unit 1), and yeliow-grey unfossiliferous, ?early diagenetic dololutites, locally containing Thalassinoides isp. (belonging to Unit 3 and Unit 4). Some layers are only partially altered, i.e. the coarse-grained infilling of the burrows was replaced and re- coloured without changing the surrounding dark grey fine sediment (Fig. 4F). This phenomenon shows that the dolo- mitizing fluids initially migrated laterally via the complex network of burrows, from which they could have spread out to penetrate the surrounding fine deposit. Apart from the obvious colour change and dolomitiza- tion, visible both macro- and microscopically (Fig. 16B, C), two other types of aheration are con-picuous, when the undolomitized bioturbated fine-grained deposits are com- pared with the epigenetically dolomitized ones. Firstly, the network of more-or-less reguiar burrows was replaced by irregularly spotted macrofabric (Figs 4B, C, 5A, 13A). This change presumably resulted from a selective dolomitization of bioturbated muddy deposit. To prevent the collapse of the burrows, ichnofauna impregnated their walls using organic mucus, which changed the chemistry of the muddy deposit around each burrow and resulted in the formation of distinct diagenetic haioes (Fig. 4F; Myrow, 1995; Bertling, 1999). The hydrothermal fluids, penetrating such a substrate long after lithification and reacted in a different way with its bio- chemically altered parts, causing a selective colour change and the development of the irregular spots. The second change is that the original non-porous fabric was replaced by vugs of different sizes. This change might have resulted from the dissolution of the blocky calcite and coarse- grained sediment, filling the burrows (Figs 4C, 16D). The dissolution process might have been already initiated during the emersion of the Olkusz Beds. However, according to Mochnacka and Sass-Gustkiewicz (1981), the bulk of dis- so lution was strictly as so ci ated with the epigenetic dolomi- tization. How ever, there are reports from other areas, where large vugs were created during the dolomitization process itself without any indication of dissolution (Lapponi et al., 2014, with further references). SEDIMENTOLOGY OF THE “ORE-BEARING DOLOMITE” 107 Fig. 16. Modification of original rock textures by epigenetic dolomitization. A. Vertical outcrop view of cavernous fabric, developed in pelolite. Note that some cavernous vugs still have the shape of bivalves (black arrow) and gastropods (white arrow). Unit 2, Nowa Wioska - “GZD” Quarry. B. Vertical outcrop view of limestone-dolostone boundary. Note distinct colour alteration and coarsening of primary micritic deposit. Unit 1, Pogorzyce - “Żelatowa” Quarry. C. Vertical outcrop view of the gradual transition from the primary grey calcilutite and hummocky cross-stratified calcisiltite to secondary orangeish coloured dolosiltite. Unit 1, Pogorzyce - “Żelatowa” Quarry. D. Vertical outcrop view of dolomitized ?Thalassinoides-bearing firmground with partially dissolved coarse-grained infills ofburrows. Unit 1, Imielin - „PPKMiL” Quarry. CONCLUSIONS 1. The name “ore-bearing dolomite” is a mining term which should no longer be used as a formal lithostratigra- phic term, because epigenetic dolomitization affected vari- ous lithostratigraphic units of the Middle Triassic succes- sion in southern Poland, and these units can be easily recog- nized from lithological criteria, as demonstrated in this study. These units represent consecutive evolutionary phases of the Kraków-Silesia Sub-basin (basically the tran- sition from a regressive state, through emersion to a transgressive state). As an informal term “ore bearing dolo- mite”, if used, should be put in inverted commas. 2. The lowermost Unit 1 is made up of Balanoglossi- tes and Thalassinoides micritic firmgrounds, intercalated mainly with tempestitic pelolites, which were formed on the lower shoreface. The overiying Unit 2 is dominated by cross-stratified pelolites with an unknown amount of now recrystallized ooids, representing the upper shoreface and foreshore. Subsequent emersion terminated sedimentation in the region. Unit 3, capping the regional disconformity, consists of several metre-scale peritidal cycles that are com- posed of supratidal dolocretes, rhizolites and mudstones, intertidal cryptalgal laminites, and subtidal pelolites and bioturbated fine-grained dolostones. These lithofacies rep- resent a tidal flat-lagoon system. The disappearance of su- 108 M. MATYSIK pra- and intertidal facies, resulting from a continuing trans- gression, marks the basal parts of Unit 4. 3. The depositional and diagenetic history of the Kra- ków-Silesia Sub-basin in the Anisian determined the subse- quent development of the entire ore disirict. The clay-rich carbonate muds at the base created an impermable barrier and concentrated fluids in an interval of overlying strata, ap- proximately 35 m thick. These strata were predominantly composed of porous carbonate grainstones-packstones and bioturbated mudstones (mostly firmgrounds). Even the bio- turbated mudstones coniained coarser sediment, the infil- ling material of the burrows Balanoglossites and Thalassi- noides networks. Owing to the third-order regression, part of these deposits was subj ected to subaerial exposure and met eoric diagenesis, which resulted in the development of moldic porosity. This combination of primary lithological feaiures and diagenetic aheration favoured, during burial, the migration of dolomitizing soiutions and further aher- ation to a poiential host rock. Subsequently, the dolomiti- zing fluids spread laterally via porous horizons, such as pelolite packages or networks of burrows, which resulted in the distinct epigenetic aheration of the primary deposits. The dissolution of blocky calcite and the coarse-grained in- filling of burrows, but also the enlargement of biomoldic pores, led to the formation of a massively cavernous fabric, which probably owing to further dissolution was ultimately changed into large karstic forms that host economically im- portant ore bodies. In conclusion, the presence and distribu- tion of porous horizons in the “ore-bearing dolomite” suc- cession was a major lithologic control on the circulation of dolomitizing fluids in the host rock. 4. This study fills a gap in knowledge of the evolution of the Kraków-Silesia region before the epigenetic dolomi- tization and explains why ores and ore-bearing dolomites developed within these particular rocks. However, more de- tailed laboratory analysis is necessary to supplement the data and conclusions presented. The author hopes this study will initiate new investigations on the origin of Polish lead- zinc deposits that will pay more attention to the stratigra- phy, composition and history of the hosting strata. Acknowledgements Firstly, I would like to thank Joachim Szulc (Jagiellonian University, Kraków, Poland) for fruitful discussions on different aspects of sedimentology. I am indebted to Alfred Uchman and Stanisław Leszczyński (Jagiellonian University, Kraków, Poland) for consultations about trace fossils and sedimentary structures, re- spectively, and to Ioan Bucur (Babes-Bolyai University, Cluj-Na- poca, Romania) and Hans Hagdorn (Muschelkalkmuseum, Ingel- fingen, Germany) for the determination of green algae and crinoid taxa, respectively. Radosław Makuła is gratefully acknowledged for as-istance with climbing during the exploration of some quarry walls. 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[In Polish, with English sum- mary.] Appendix GPS coordinates of all outcrops presented in this study (in alpha- betical order): Bolęcin - “Skała Bolęcka” abandoned quarry (50°06'55.12"N; 19°27'45.35"E); Bukowno - „Olkusz-Pomorzany” lead-zinc active mine (50°18'02.95"N; 19°30'05.34"E); Dąbrowa Górnicza - “Ząbkowice” active quarry (50°22'19.75"N; 19°17'54.98"E); Imielin - abandoned quarry (50°08'52.43"N; 19°12'13.67"E); Imielin - “PPKMiL” active quarry (50°09'15.68"N; 19°11'42.80"E); Jaroszowiec - “Stare Gliny” active quarry (50°21'05.62"N; 19°35'22.45"E); Kąty Chrzanowskie - abandoned quarry (50°09'07.00"N; 19°22'27.55"E); Libiąż - active quarry (50°06'51.28"N; 19°20'04.35"E); Libiąż - Moczydło - “LiBet” abandoned quarry (50°05'18.67"N; 19°18'55.84"e); Nowa Wioska - “GZD” active quarry (50°30'01.82"N; 19°12'40.37"E); Nowa Wioska - “PROMAG” active quarry (50°30'35.20"N; 19°14'02.17"E); Nowa Wioska - “TRIBAG” active quarry (50°30'05.32"N; 19°14'16.36"E); Olkusz Stary - abandoned quarry (50°17'22.53"N; 19°31'08.96"E); Płaza - abandoned pit in forest (50°06'58.46"N; 19°26'32.26"E); Płaza - “GiGa” active quarry (50°06'24.36"N; 19°26'18.85"E); Pogorzyce - “Żelatowa” active quarry (50°06'42.08"N; 19°23'37.56"E); Tarnowskie Góry - “Blachówka” abandoned quarry (50°24'25.04"N; 18°51'10.83"E).