Lithology and sedimentation of Upper Jurassic massive limestones near Bolechowice, Kraków-Wieluń Upland, south Poland

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Annales Societatis Geologorum Poloniae (1996), vol. 66: 285 - 301.

LITHOLOGY AND SEDIMENTATION OF UPPER JURASSIC MASSIVE LIMESTONES NEAR BOLECHOWICE,

KRAKÓW-WIELUŃ UPLAND, SOUTH POLAND

Jacek MATYSZKIEWICZ & Marcin KRAJEWSKI

U niversity o f M in in g a n d M etallurgy; F aculty o f Geology, G eophysics a n d E nviro n m en ta l P rotection;

al. M ickiew icza 30, 30-059 Kraków, P o la n d

Matyszkiewicz, J. & Krajewski, M., 1996. Lithology and sedimentation o f Upper Jurassic massive limestones near Bolechowice, Kraków-Wieluń Upland, south Poland. Ann. Soc. Geol. Polon., 66: 285-301.

A bstract. The major constituent of Upper Jurassic limestones which build Brama Bolechowicka (Bolechowice Gate, a group o f valley-wall limestone rocks near Kraków) is massive limestone representing a complex of cyanobacterial-sponge carbonate buildups. Talus sediments o f the buildup are present as clastic limestones exposed in isolated crags. Apparent bedding planes visible in the massive limestones are dissolution-widened fractures, fault joints and gently inclined shearing fractures in fault-related flexures. Limestones exposed ESE from Brama Bolechowicka represent interbiohermal facies and clastic sediments of variable age and origin. The Jurassic strata exposed ESE from Brama Bolechowicka lie within a wide fault zone which separates the Ojców Block from the Krzeszowice Graben. The variable dipping directions of these strata are caused mainly by the presence of hinge faults within this fault zone.

A bstrakt. Zasadniczą część górnojurajskich wapieni tworzących Bramę Bolechowicką stanowi kompleks cyjanobakteryjno-gąbkowych budowli węglanowych wykształconych jako wapienie masywne. Osady talusa budowli są reprezentowane przez wapienie detrytyczne budujące pojedyncze skałki Bramy Bolechowickiej.

Powierzchnie nieciągłości w wapieniach masywnych są spękaniami ciosowymi, szczelinami uskokowymi i połogimi ścięciami tektonicznymi w obrębie fleksury przyuskokowej. Osady odsłaniające się na ESE od Bramy Bolechowickiej reprezentują facje międzybiohermalne oraz osady detrytyczne o zróżnicowanym wieku i genezie.

Występowanie na ESE od Bramy Bolechowickiej utworów jurajskich o zróżnicowanym wykształceniu, ale generalnie młodszych od facji obserwowanych w Dolinie Bolechowickiej ma przyczyny tektoniczne, a nie sedymentacyjne. Zmienne kierunki nachyleń tych utworów są spowodowane głównie obecnością uskoków zawiasowych w rozleglej strefie uskokowej oddzielającej płytę ojcowską od rowu krzeszowickiego.

Key words: carbonate buildups, microfacies, Upper Jurassic, Kraków region, Southern Poland Manuscript received 18 April 1996, accepted 30 August 1996

INTRODUCTION

S tructure and origin o f lim estone rocks on the K raków - W ieluń U pland attract th e attention o f geologists for m any years. The opinions on th ese topics w ere based on results o f sedim entological, m ineralogical, palaeontological and tec

tonic studies. The m odem research technique is a com bina

tion o f m ezoscopic observations and m icrofacies analysis.

W here structure o f the lim estones is indistinct, these tw o m ust be supported by m ezoscopic observations. U nbalanced adherence to only one o f these m ethods m ay lead to quite erroneous conclusions according to K utek e t al. (1977).

The Jurassic lim estone crags are a specific place for sedim entological studies; they often require rock-clim bing techniques for close inspection o f structures visible on ex posed rock surface and for sam pling. D etailed m ezoscopic

and m icrofacies investigations can not be replaced by obser

vation from a long distance; this provides inform ation only on relief w hich is controlled by com bination o f sedim en

tological, diagenetic, tectonic and clim atic factors.

In 1995, the second author (M . K .) collected sam ples along vertical lines on four c liff faces w ithin the rock group o f B ram a B olechow icka (B olechow ice G ate): F ilar P o k u t

ników and Zam arła T urnia on the w est slope o f the valley, F ilar W allischa and Ż ółta Ścianka on th e east slope. The sam ple collection w as accom panied by detailed observation and registration o f m ezoscopic sedim entary structures. The authors studied also the lithology o f sedim ents in th e other rocks o f the B olechow icka valley and in sm all quarries adja

cent to B ram a B olechow icka on its E SE side. M icrofacies analysis and interpretation w as p erform ed by the first author (J. M .)

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osady przedjurajskie p re -J u ra ssic strata Kelowej

Callovian G órna Jura

Upper Jurassic

Kreda Pliocen

Cre tace o u s 11111111 Pliocene

Paleógen uskoki pewne

Paleogene fa u lts certain

Miocen u sk o ki prawdop.

M iocene * fa u lts inferred

j granice geologiczne

— y geological boundaries nasunięcie karpackie Carpathian overthrust

^ opisywane odstoniecie described exposure Fig. 1 Location of the study area (after Rutkowski, 1989 and Gradziński, 1972, simplified)

History of investigations

T here are few papers on m ezoscopic and m icrofacies structure o f Jurassic ro ck y lim estones near K raków (D żu

łyński, 1952; B ukow y, 1960; G olonka & H aczew ski, 1971;

G łazek & W ierzbow ski, 1972; H offm ann & M atyszkie

w icz, 1989; M atyszkiew icz & Felisiak, 1992; M atysz

kiew icz, 1989, 1990, 1993, 1994, 1996). In the light o f these papers th e Jurassic lim estones are carbonate buildups w hose m ain constructors w ere sponges and cyanobacteria in broadly varying proportions and w hose degree o f rigid fram ew ork developm ent increases upsection. The buildups could coalesce during th eir grow th, and thus form extensive bioherm al com plexes rising above the surrounding sea floor.

Stratified lim estones w ith cherts originated on their slopes and in th e interbioherm al areas. B asinal facies in the form o f alternating m arls and platy lim estones w ere laid dow n in the deepest parts o f the basin, rem oved from the bioherm al com plexes (M ałecki, 1958; Felisiak, 1988; M atyszkiew icz, 1990).

T ypical for the for low er p art o f th e O xfordian sequence in th e K raków area are so called loose bioherm s (sensu T ram m er, 1989) built up m ainly o f siliceous sponges. In the M iddle O xfordian these bioherm s are replaced w ith sponge- cyanobacterial and cyanobacterial-sponge buildups (H o ff

m ann & M atyszkiew icz, 1989), locally developed in the

form o f so called p seu d o n o d u la r (zrostkow y) lim estones (D żułyński, 1952; G radziński, 1972; M atyszkiew icz, 1994).

The term pseudonodular lim estone is used to described lim estone com posed o f sm all (up to 5 cm ) subangular n o d ules. The nodules have diffuse boundaries and are densely packed; they also stand out during w eath erin g and easily fall out from w eathered rock, w hen struck w ith a ham m er. In the U pper O xfordian the dom inating types are already cyano

bacterial-sponge buildups (M atyszkiew icz, 1989) and cya- nobacterial buildups o f the T ubiphytes r e e f ty p e (M atysz

kiew icz & Felisiak, 1992). A cco rd in g to M atyszkiew icz (1994, 1996) th e evolution o f the Jurassic carbonate build

ups in the K raków area w as co ntrolled by progressive shal

low ing during O xfordian, recorded in the w hole belt o f epi

continental seas fram ing the T ethys O cean from the north (Leinfelder, 1993).

O ne m ajor period o f b ioherm destruction, clearly m arked in the Jurassic sequence o f th e K raków area (M a

łecki, 1958; G łazek & W ierzbow ski, 1972; M atyszkiew icz, 1994, 1996), took p lace probably at th e end o f O xfordian (?beginning o f K im m eridgian). Its possible equivalent is the upper m arly horizon (B urzew ski, 1969) found in boreholes in th e N id a D epression area (Fig. 1). R edeposited sedim ents are com m on also in the M iddle O xfordian sedim ents ex

posed in the quarry in M łynka and its close vicinity. It is not clear if these sedim ents represent a regional stage o f bio

herm destruction or are a local p h enom enon rela ted to the

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UPPER JURASSIC LIM ESTON ES N E A R BOLECHOW ICE

287

existence o f a synsedim entary fault in this area (M atyszkie- w icz, 1993; W ieczorek & K robicki, 1994).

The Jurassic sedim ents o f the K raków area w ere the subject o f num erous tectonic studies (D żułyński, 1953; M a

łecki, 1958; B ogacz, 1967; G radziński, 1962, 1972; K roko

w ski, 1984; R utkow ski, 1986; F elisiak, 1988). The results o f these studies indicate th a t ap art from num erous faults the lim estones are cut by several system s o f jo in ts, and fault zones in the northern m argin o f the K rzeszow ice G raben are accom panied by so called low -angle shears, related to n ear

fault flexures (K rokow ski, 1984).

Inclined surfaces m acroscopically discernible in the Ju

rassic lim estones near K rak ó w have been a subject o f p ro longed discussion. T h eir origin w as attributed to tectonics (D żułyński, 1953; G radziński, 1972; K rokow ski, 1984; R ut

kow ski, 1986), deposition (M ałecki, 1956; B ukow y, 1960;

G radziński, 1972; R utkow ski, 1986; Felisiak, 1983, 1988;

M atyszkiew icz & Felisiak, 1992) or deposition and diagene

sis (D żułyński, 1952; G radziński, 1972; M atyszkiew icz, 1989). D istinction betw een jo in ts and bedding planes is easy in bedded lim estones (G radziński, 1972, p. 293) w hile in m assive lim estones it requires detailed studies o f m icrofacies or analysis o f tectonic m ezostructures. The use o f m e- zoscopic observations alone m ay result in confusion o f jo in ts and low -angle shearing planes w idened by solution w ith bedding planes. A m ong m any sites w here the inclined surfaces are observed, only tw o exposures have detailed microfacies evidence - those in P iekary (M atyszkiew icz, 1989), w here the inclined surfaces are due to differential com paction o f m assive and bedded lim estones and in M ydl- niki (R utkow ski, 1986; M atyszkiew icz & Felisiak, 1992) w here th eir n ature is depositional.

M icrofacies have been n o t hitherto studied in the rocks th at m ake up B ram a B olechow icka. T ectonics o f the SW part o f th e K raków -W ieluń U pland, including the area o f B olechow ice, w as studied in detail by K rokow ski (1984).

B asing on the study o f m esostructures, he concluded that the lim estones are cut by several jo in t system s and that they are deform ed by flexures. T he flexures occu r along th e w hole northern m argin o f the K rzeszow ice G raben for w hich w ide fault zones are characteristic (B ogacz, 1967; K rokow ski, 1984). D iscontinuity surfaces inclined tow ard ESE are, ac

cording to K rokow ski (1984) low -angle shearing planes in clined at about 30-40° “ caused by flexural bending o f strata in vicinity o f m ajor faults” (K rokow ski, 1984, p. 92). The flexural deform ations are also visible in the B olechow icka valley (K rokow ski, 1984, p. 83).

T he lithology o f the lim estones in B ram a B olechow icka and directly east o f it w as recen tly discussed by K oszarski (1995) w ho included the lim estones to the upper part o f the U pper O xfordian (K oszarski, 1995, p. 11), estim ated their position above the base o f th e Jurassic at about 170-290 m (K oszarski, 1995, p. 11), and considered these lim estones to be redeposited sedim ents. T he inclined surfaces in the lim e

stones o f B ram a B olechow icka are, according to this author, o f depositional origin, “sole surfaces o f strata are erosional”

(ibidem , p. 15), and “ individual bedding surfaces continue tow ards N and N W w hich is visible in another rocks o f B ram a B olechow icka and B olechow icka valley” (ibidem , p.

15). Sedim ents exposed on the slope ad jacen t to B ram a B olechow icka on ESE w ere described by him as transgres- sively overlying “turbidites and d eb rites-ca lciru d ites, grad

ing into calcarenites” (ibidem , p. 15), inclined to SE near B ram a B olechow icka and “in the east m argin o f the next eastw ard valley in B olechow ice” are “ steeply inclined to W and N W ” (ibidem , p. 15). “ Slides on p lastically deform ed thin lenses o f chert” should o ccur in th e sedim ents inclined to SE (ibidem , p. 15), allegedly indicating tran sp o rt o f m a te

rial to SES, as w ell as “postdepositional initial slum ping re

locations, indicating m ovem ent o f p ackets deform ed in this w ay to S and SE” (ibidem , p. 15). T hicknesses o f beds are claim ed to decrease upsection, and to be on average about 1 m in its m iddle part. D escribing th e sedim ents in sm all, iso

lated quarries ESE o f B ram a B olechow icka, K oszarski de

scribes their relative age using th e term s “o lder” and

“younger”, w hich enables him to correlate sedim ents situ

ated on the slope at various elevations and inclined in vari

ous directions and to conclude th a t th e y build one “great de

positional syncline” (ibidem , p. 16) w hose inclinations are related to “deposition by m ud flow s on a steeply inclined r e e f slope, intensely aggraded by sedim ents (prograding)”

(ibidem , p. 16). The m assive lim estones in B ram a B olecho

w ick a are, according to him “th e older part o f the sedim ent sequence prograding on th e slope o f this syncline” (ibidem , p. 16). B asing on these observations, K oszarski (1995) de

term ines the m inim um range o f se a b ottom elevation at 80 m.

GEOLOGICAL SETTING AND REMARKS ON STRATIGRAPHY

The K raków region is situated in th e southern part o f the K raków -W ieluń U pland (Fig. 1). T he Jurassic sedim ents in this southern part differ m arkedly from those in o ther areas (Kutek, 1994). The differences consist in m uch low er thick

ness o f preserved Jurassic sedim ents (up to ca. 300 m in the eastern part and m uch less in the w est), incom pleteness o f the section as com pared to the areas on the north and east, and clear lithological differences. T he reason for the dis

tinctiveness o f this area w as its n eg ligible subsidence in Ju

rassic tim e, caused b y the presence o f low -density granitoid m asses in the basem ent (K utek, 1994). T he lack o f com pen

sation o f sedim ent accum ulation b y subsidence (Kutek, 1994, p. 213; M atyszkiew icz, 1994, p. 428) caused th at the K raków region existed in Jurassic tim e as a distinct raised elem ent, especially favourable for th e developm ent o f car

bonate buildups. The analysis o f lithology o f Jurassic lim e

stones in the K raków area requires thus a special caution in adaptation o f m odels created for o ther areas. T his applies especially to such a discussion o f th e basin depth an d b o t

tom relief w hich assum es a p ersistent inclination tow ards the T ethys ocean in the w hole area o f th e P olish fragm ent o f the sh e lf (see M atyja & W ierzbow ski, 1996).

U pper Jurassic sedim ents near K raków are represented by th e O xfordian stage. T he presence o f K im m eridgian sedim ents has been n o t p alaeontologically p roven (G łazek

& W ierzbow ski, 1972), though it can n o t be com pletely

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® , .PIĘTROWA TURNICZKA" (T)„PO PR ZEC ZN A GRZĘDA"

Fig. 2 Location sketch o f Brama Bolechowicka and its vicin

ity. The western part and rock names after Baran & Opozda ( 1985)

ruled out (B ukow y, 1957, 1962; M atyszkiew icz, 1996).

B iostratigraphical zonation o f the higher part o f the Jurassic sedim ents is difficult b ecause o f the paucity o f am m onites in the m assive lim estones. T he attribution to an am m onite zone is based on a few exposures w here am m onites w ere found and w hose elevation above the top o f the D ogger is known.

A ssum ing th at the thicknesses o f the M alm sedim ents in te c tonic depressions and neighbouring horsts are sim ilar (R ut

kow ski, 1986) it m ay be accepted that the exposures w hich occur at the sam e or sim ilar elevation over the top o f the D ogger belong to the sam e am m onite zone. This m ethod lacks precision in the Jurassic sedim ents o f the K raków re

gion w hich feature m arked variations in p alaeo relief and n u m erous faults. M oreover, the thickness o f Jurassic on the O jców block is m uch low er than in the K rzeszow ice G raben (R utkow ski, 1986).

T he rock pylons o f B ram a B olechow icka are situated w ithin the area o f the northern m argin o f the K rzeszow ice G raben, adjacent to a m ajo r fault zone. The faults in this zone are related to E arly P aleogene fault m ovem ents. They w ere created probably still before E ocene and w ere sub

sequently rejuvenated in M iocene tim e (Rutkow ski, 1989, in press). T he com plex structure o f the fault-adjoining zone is dem onstrated by the p resence o f tectonic en échelon faults found at th e northern m argin o f the K rzeszow ice G raben east and w est o f the B olechow ice valley (Fig. 1). A ccording to B ogacz (1967), the m ain fault w hich separates the O jców block from the K rzeszow ice G raben is a com posite fault, com posed o f m any sm aller successively dow nthrow n blocks w hich com pose a tectonic m egabreccia. The am ount o f displacem ent along any given block m ay vary due to the hinge geom etry o f m any faults (Bogacz, 1967, p. 54).

The rock pylons o f B ram a B olechow icka are situated p robably about 100 m above the bottom o f the Jurassic. This estim ate is based on data from boreholes m ade in the sixties on the O jców U pland: K -2, K -2a, K -3, K -4 and K -6, situ

ated about 2 km w est o f B ram a B olechow icka, near K am io- w ice and from borehole B ębło, situated about 6 km to the north. T he total preserved thickness o f Jurassic does not ex

ceed 91 m in any o f these boreholes. In boreholes situated in the K rzeszow ice G raben, K-5 in K am io w ice and B -l (about 0.5 km south o f K obylany), the preserv ed thicknesses o f the Jurassic equal 225 and 240 m, respectively.

The lack o f am m onites has hitherto p recluded precise determ ination o f the age o f th e pylons o f B ram a B olecho

w icka and the exposures ESE o f it. T he accepted estim ate o f the elevation o f the pylons above th e bottom o f th e Jurassic seem s to indicate to a higher part o f the M iddle O xfordian.

Methods

The basic m ethods applied w ere m ezoscopic observa

tions and m icrofacies analysis. D etailed sam pling along ver

tical sections o f Filar W allischa, Ż ółta Ścianka, F ilar P o k u t

ników and Z am arła Turnia, m ade w hile descending on a rope along the cliffs, provided 59 oriented sam ples (Fig. 3).

The sam ples w ere cut and polished, 29 vertically oriented large-size thin sections w ere m ade from the sam ples. D e

tailed observations o f sedim entary structures w ere m ade w hile descending the cliffs o f F ilar A bazego, P iętrow a T ur

niczka and P oprzeczna G rzęda. A dditional sam ples, col

lected from selected sites in B o lechow icka valley, w ere used to m ake polished sections and 7 thin sections.

G eopetal structures in Filar Pokutników w ere used to determ ine approxim ate position o f horizontal plane during deposition and its present inclination. B ecause the sam ples were oriented only vertically, and their horizontal orienta

tion w as only approxim ate, it w as accepted that the post-depositional tilt o f the rock is indicated by th e greatest angle o f inclination o f geopetal structures observed in thin sections, and repeats at least three tim es in the sam e thin section, in order to elim inate casual m easurem ents.

Frequencies o f occurrence o f all com ponents w ere de

term ined in each thin section b y sem iquantitative m ethod.

The frequency o f occurrence o f each m icrofacies o f D un

ham (1962) was determ ined in each thin section and pol

ished section (T able 1).

D etailed sam pling w as also done in the exposures situ

ated on the slope ESE o f B ram a B olechow icka. P olished sections w ere m ade o f all 20 sam ples taken there and 5 ori

ented thin sections for the sakes o f com parison. T he loca

tions o f these exposures are show n on a m ap w hich also show s the southern p art o f the B olechow icka v alley (Fig. 2).

MEZOSCOPIC AND MICROFACIES CHARACTERISTICS OF LIMESTONES

IN THE AREA OF BRAMA BOLECHOWICKA

Brama Bolechowicka

The m ain lithological types are present in th e lim estone rocks w hich m ake up B ram a B olechow icka: m assive lim e

stone and clastic lim estone. M ost rocks, except for the southernm ost ones on the eastern slope - F ilar W allischa and P iętrow a T urniczka - are built o f light-coloured m as

sive lim estone in various shades o f colour, strongly lithified.

S edim entary structures are in m ost cases poorly discernible

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U PPER JURASSIC LIM ESTONES N EA R BOLECHOW ICE

289

Fig. 3 S am p le locations on slopes o f B o lech o w ick a valley, a - on F ilar P o k u tn ik ó w , w est slope, h eig h t o f ro ck - 35 m; b - on F ilar W allisch a, e as t slope. F ilar A b a ze g o (FA ) is separated from F ilar W allisch a (F W ) by a fa u lt plan e w id en ed b y d isso lu tio n (b lac k arrow ).

T he w h ite arro w po in ts an e a sily accessib le place on FA w here stro m ato litic stru ctu res can b e o b se rv ed in situ. H eig h t o f F W - 20 m; c - on Z am arła T u rn ia, w est slope, h eig h t o f rock a bout 30 m; d - on Ż ó łta Ścianka, east slope, h eig h t o f rock 15 m

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internal sediment cement osad wewnętrzny n ici

Fig. 4 Determination o f the angle o f deflection of rock from its original horizontal position indicated by geopetal structures. The angle of dip of internal sediment - a equals the angle of deflection of the rock from the original vertical. Only a section parallel to the plane a shows the true inclination of the top of internal sediment in the geopetal structure. The visible angle is lower in every other section. In an extreme case, in a section perpendicular to the plane a, the top of internal sediment will be seen horizontal

m ezoscopically. W ell discernible strom atolitic structures are w ell visible in low er, easily accessible part o f Filar A bazego; they occur also in th e higher parts o f the c liff (Fig. 3b).

N um erous surfaces o f discontinuity are visible in m as

sive lim estones, especially in the southern part o f the valley (Figs. 5, 6, 12). T hese surfaces m ay be divided into tw o types. The first includes steep, locally vertical surfaces, es

pecially w ell visible in the rocks on the w estern slope o f the valley. T he second type are gently inclined surfaces, in

clined to ESE or SE, visible in the w estern slope on Filar P okutników and Z am arła T urnia as well as in the eastern slope on Poprzeczna G rzęda. The dip o f these surfaces is greatest in the southernm ost part o f the valley and it g radu

ally decreases northw ards. The values o f dip m easured at the base o f F ilar Pokutników are 42-55° and at the base o f Zam arła T u rn ia 40°. T he relationship betw een the disconti

nuity surfaces and sedim entary structures could not be de

term ined because o f poor visibility o f structures in the m as

sive lim estone.

F ilar W allischa and the low er part o f Piętrow a T ur

niczka are built o f clastic lim estone w hich includes individ

ual thin (about 0.1 m ) beds, som e o f them w ith sharp boundaries, built o f w ell sorted grains up to 3 mm in diam e-

Fig. 6 View of the western slope o f Bolechowicka valley (after Baran & Opozda, 1985; slightly modified and simplified)

ter. T hey are inclined to SE at an angle o f about 25°. N o transition was observed betw een th e m assive and clastic lim estones. P iętrow a T urniczka is an isolated crag and Filar W allischa is separated by a vertical, fissure, w idened by dis

solution from Filar A bazego built o f m assive lim estone (Fig.

3b).

Biolithite is the dom inant m icrofacies in the m assive lim estone that builds the m ajor part o f B ram a B olecho

w icka, w ackestone is subordinate (T able 1; Figs. 7, 8).

Fauna observed in thin sections consists m ainly o f calcified siliceous sponges and th eir spicules, encrusting and benthic foram inifers, serpulids, bryozoans and echinoderm s. The m ain rock-form ing elem ent are cyanobacterial structures in the form o f crusts, strom atolites and throm bolites (cf. M a

tyszkiew icz, 1994; D rom art et al., 1994). W ackestone con

sists m ostly o f peloids, sm all tuberoids and oncoids. C om m on transitions from w ackestone to cyanobacterial biolithites are visible in thin sections. L ow density o f sam pling does not perm it to attem pt a detailed analysis o f the v ariab il

ity o f fauna in the vertical sections o f the buildups.

N um erous grow th cavities and burrow s are visible in the biolithite. M ost o f them have geopetal fillings w hich perm it to determ ine the position o f original horizontal plane.

The angle o f inclination o f geopetal infillings in sam ple 17 taken from Filar Pokutników is about 30° (Fig. 9), and this value (the greatest in the studied thin sections) w as accepted as the value o f postdepositional tilt (see Fig. 4). N o signifi

cant differences w ere found betw een the m icrofacies o f the parts o f rock separated by discontinuity surfaces (sam ple pairs 5-6 and 14-15 in F ilar Pokutników , 10-11 in Z am arła Turnia).

F ilar W allischa and the low er part o f P iętrow a T urniczka differ in th eir m icrofacies from other sam pled rocks (T able 1; Fig. 10).

The clastic lim estone consists o f m icritic packstone and - especially in th e low er part o f the exposure - grainstone. T he grains include n u m erous Tubiphytes, m icritized ooids, frag

m ents o f calcareous sponges and num erous brachiopods, bryozoans, tuberoids and intraclasts. Sorting and roundness are variable.

N on-sorted sedim ent, lacking directional sedi-

.POPRZECZNA G R ZĘ D A"

FILA R ABAZEGO'

„Ż Ó Ł T A Ś C IA N K A "

Fig. 5 View of the eastern slope of Bolechowicka valley (after Baran &

Opozda, 1985; slightly modified and simplified)

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U PPER JUR ASSIC LIM ESTON ES N E A R BOLECHOW ICE

291

Fig. 7 M icro facies in F ilar Pokutników , a - cy an o b acterial-sp o n g e biolithite. C y an o b acterial stru ctu res - th ro m b o lites (T) and stro m ato lites (S t) o v erg ro w in g a calcified siliceous sponge encrusted by serpulids (S). F ilar P oku tn ik ó w ; th in sectio n , sam p le no. 6; b - cy an o b acterial-sp o n g e bio lith ite. S ed im en t b o und by cy an o b acterial structures - crusts (C) and stro m ato lites (St) w as su b je ct to early lith ificatio n w hich en ab led th e d e v elo p m en t o f a rigid fram ew ork. T he p resen ce o f the rig id fram e w o rk is d o c u m e n ted b y g ro w th cavities (G c) w h o se w alls are e n cru ste d b y serp u lid s (S) and n um erous borings (B ) in the sed im en t filled w ith in tern al sedim ent. C a lcified siliceous sponge (S p) visib le in the u p p e r part. F ilar P o kutników ; th in section; sam ple no. 10; c - cy an o b acterial-sp o n g e bio lith ite w ith n u m ero u s c o lu m n a r stro m ato lites (St). C alcified siliceous sponge (Sp) in the u pper right. F ilar P o kutników ; th in sectio n ; sam ple no. 8; d - sp o n g e-cy an o b acterial bio lith ite. C alc ified siliceo u s sponges (S p) in the low er and u p p er part; betw een th em n u m ero u s cy an o b acterial stru ctu res - th ro m b o lites (T ) an d cru sts (C). A b oring (B ) filled w ith internal sed im en t is v isib le in the sp o n g e a t the bottom . F ilar P oku tn ik ó w ; th in section; sa m p le no. 3

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Fig. 8 M icro facies in Ż ó łta Ś cian k a and Z am arła T urnia, a - sp o n g e-cy an o b acterial biolithite. C a lc ifie d silic eo u s sponge (Sp) d isp lay in g an extensive b o rin g (B ) w ith the shell o f th e b oring o rganism p reserv ed and g eopetal filling. T h ro m b o lite s p ro fu se ly encrusted w ith fo ram in ifers are g ro w in g on the siliceo u s sponge. T he arro w indicates the p resen t positio n o f top. Ż ó łta Ś cianka; th in sectio n ; sam ple no. 10; b - cy an o b acterial-sp o n g e b iolithite. C alcified siliceo u s sponge (Sp) w ith ob literated internal stru ctu re, o v erg ro w n w ith c y an o b acterial crusts (C ) and stro m ato lites (St). B oring (B ) v isible in the sponge is filled w ith internal sedim ent. Z am arła T u rn ia; thin section; sam p le no. 2; c - c y an o b acte ria l-sp o n g e bio lith ite (in the low er and up p er p art) w ith a lay er o f w ack e sto n e (left) p assin g to m icritic g rain sto n e (right). N u m e ro u s initial c ru sts (C ) v isib le in the w ackestone. T h ro m b o lite (T) a t the bo tto m , c alcified siliceo u s sponge (Sp) w ith ob literated internal structure, at th e top. Ż ó łta Ścianka; th in section; sam ple no. 12; d - c y an o b a cte ria l bou n d sto n e, locally w ack esto n e. C y an o b acterial stru ctu res: stro m ato lites (St) and cru sts (C ) stab ilizin g so called p e lo id sand. Z a m arła T u rn ia; th in section;

sam p le no. 7

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U PPER JURASSIC LIM ESTON ES N E A R BOLECHOW ICE

293

m entary structures predom inates. Som e sam ples include cyanobacterial crusts, som e o f them w ith distinct borings.

G eopetal fillings are sporadic. The basic differences in com position o f constituents in com parison to the m assive lim e

stone consist in the com m on presence o f oncoids, m icritized ooids and Tubiphytes, a slightly greater am ount o f calcare

ous sponges and gastropods, the appearance o f oysters and a m arked decrease in the n u m b e r o f siliceous sponges.

Exposures ESE o f Brama Bolechowicka

T he exposures in sm all quarries situated ESE o f the py lons o f B ram a B olechow icka are situated at various eleva

tions on the slope falling tow ards th e village o f B olechow ice (Fig. 2). D istinct terraces are m arked in the slope. T hey are inclined in various directions, som e diagonally to the slope.

D etailed investigations w ere m ade in three quarries (Fig. 2:

A, B, C).

A n exposure about 7.5 m high, situated directly behind the last houses o f the v illage (Fig. 2: A; Fig. 11) reveals bedded lim estones. The section starts w ith a 3.5 m thick com plex o f strongly lithified cream coloured bedded w ackestone-floatstone. T hickness o f beds increases from 0.15 m at the bottom to 0.5 m at the top. Lenses o f chert, up to 0.1 m thick, and occasionally slightly bent upw ards or dow n

w ards, occur locally at the layer boundaries. Isolated chert nodules up to 0.15 m in diam eter occur also w ithin the beds.

The m icritic m atrix includes abundant fauna represented by centim etric fragm ents o f siliceous sponges, corals, and echi- noid spines, brachiopods and echinoderm plates. The low est beds include num erous T ubiphytes and cyanobacterial coat

ings encrusted by foram inifers. The rock does not display directional structures, and th e grains em bedded in the m i

critic m atrix are not sorted.

T he w ackestone is overlain by w eathered m arl 0.1 m thick, overlain in turn by 2.8 m thick com plex o f bedded clastic lim estones (floatstone-rudstone), separated by tw o intercalations o f marl, 0.1 m thick. T he beds are 0.3-0.8 m thick, and the grain size attains 5 cm. T he sedim ent is poorly sorted. D iscernible fauna includes poorly preserved am m on

ites, siliceous and calcareous sponges, echinoderm s and bra

chiopods. B ioclasts are p reserved com plete or in large frag

m ents. L ocally, horizontal arrangem ent o f elongated b io clasts and inverted grading are discernible w ithin the beds.

D isplacem ents o f som e p o rtions o f sedim ent along arcuate surfaces are visible in clastic lim estones (Fig. 11). A ttitude o f the beds, m easured at th e top o f the highest b ed is 350/12 N E. T he section term inates w ith an irregular block, about 1 m in diam eter, in w hich clastic lim estone passes laterally into w ackestone in the direction perpendicular to the w all o f the exposure, tow ards NE.

A bout 5 m N E from th e described outcrop, at the level o f its top there is an exposure about 1 m w ide and about 1.5 m high (Fig. 2: B), o f fractured bedded w ackestone with bedding attitude 358/10 E. The bed thicknesses are about 0.5 m thick at the bottom an d they decrease to about 5 cm in the m iddle part o f the outcrop, and again increase to about 0.2 m.

A nother outcrop (Fig. 2: C) is situated in the w est slope

4 m m

Fig. 9 Sample no. 17 from Filar Pokutników, in which the inclination o f internal sediment in geopetal structures (arrows) was measured. The top o f internal sedim ent is parallel in all fillings, w hich excludes randomness. Black arrow indicates the original position o f the top. The present position o f the bottom-top direc

tion is parallel to the longer side o f the photo. Thin section

o f the valley parallel to B o lechow icka valley, and lying about 500 m east o f it. A scarp about 20 m long and about 3 m high exposes several isolated rocks built m ostly o f in

distinctly bedded w ackestone. O nly th e w esternm ost rock includes in the w ackestone a set o f tw o layers o f m icritic clastic lim estone, 0.2 m and 0.1 m thick, thinning out east

w ards to zero over the distance o f one m etre. G rain diam e

ters in these beds attain about 1 m m . The beds o f m icritic clastic lim estone are inclined to N W or W, but strike and dip could n o t be m easured.

M oreover, directly east o f the eastern p ylon o f B ram a B olechow icka and on the w hole slope north o f the village o f B olechow ice there occur scattered exposures o f non-bedded or indistinctly bedded w ackestone and clastic lim estones o f variable dips.

DISCUSSION

The rocks sam pled in the sections o f F ilar P okutników , Z am arła T urnia and Ż ółta Ścianka, as w ell as other rocks in the valley except for Filar W allischa and P iętrow a T u r

niczka consist o f biolithites (Table 1; Figs. 7, 8). T he m ain com ponents o f the biolithites are calcified siliceous sponges

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Fig. 10 M icro facies in F ilar W allischa. a - w ackestone, locally w ith g rain s ex ceed in g 2 m m in d iam eter (flo atsto n e); locally packstone.

R an d o m ly distrib u ted sh ells o f brach io p o d s, b ryozoan fragm ents, tuberoids, intraclasts, on co id s and Tubiphytes are reco g n izab le am o n g the grains. P o o r sorting and ro u n d in g o f larg er grains is noticeable. F ilar W allischa; th in section; sam ple no. 10; b - g rain sto n e. N o te p o o r sorting an d ro u n d in g and th e lack o f c arb o n ate m ud. F ilar W allischa; th in section; sam p le no. 15; c - w ack esto n e (in th e low er right) passin g to pack sto n e w ith p o o rly sorted grains. F ilar W allischa; th in section; sam ple no. 13; d - pack sto n e, locally w ackestone. P oorly sorted g rain s include n u m ero u s tuberoids, intraclasts and sm all oncoids. F ilar W allischa; th in section; sam p le no. 12; e - w a ck e sto n e (at u p p er rig h t) passin g to p ack sto n e w ith n u m ero u s Tubiphytes. F ilar W allischa; thin section; sam ple no. 5

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UPPER JURASSIC LIM ESTON ES N E A R BOLECHOW ICE

295 Table 1

M icrofacies observed in thin sections and polished sections m ade from sam ples collected in D olina B olechow icka.

Sam ples num bers sam e as in Fig. 3

Filar Pokutników

Filar Wallischa

Zamarła Turnia

Żółta Ścianka

sample próba boundstone biolityt packstone ziamitmikrytowy wackestone waka wapienna

1

B B

2 ■

3 ■

4

B B

5

B B

6 ■

7

B B

8

B B

9 ■

10 ■

11 ■

12

B B

13 ■

14

B B

15

B B

16

E B

17

B B

sample próba boundstone biolityt grainstone ziamit packstone ziamitmikrytowy wackestone waka wapienna

1

B E B

2

E E

3 ■

4

B B

5

B B

6

B B

7

B B

8 E

B

9

B B

10

B B

11

B B

12

B E B

13

B B

14

B B

15

B B

1 ■

2

B B

3

B B

4

B B

5 ■

6

E B B

7

B B

8

B B

9 ■

10

E E

11

B B

12

B B

13

B B

14 ■

1 B B

2 B œ

3

B B

4

B B

5 ■

6 ■

7

B B

8

B B

9

E E

10 B B 11

^■

12 E B B

13

B B

B - 25% area of thin-section or polished slab U - 50% area of thin-section or polished slab Q| - 75% area of thin-section or polished slab

■ -100% area of thin-section or polished slab

and cyanobacterial structures o f throm bolites and strom a

tolites type. T he results o f the m icrofacies studies allow to conclude th a t m ajor part o f m assive lim estones o f B ram a B olechow icka are developed as cyanobacterial-sponge buildups w ith w ell developed rigid fram ew ork, proved by num erous grow th cavities and lithophag borings in sponge m um m ies and cyanobacterial structures. Such sedim ents are typical o f the Late Jurassic sh e lf seas bordering the Tethys ocean from the north (L einfelder, 1993; M atyszkiew icz, 1994; D rom art et a l., 1994).

The cyanobacterial-sponge buildups in B olechow icka valley are intergrow n and th e y form a large bioherm al co m plex. Its integral part are also those parts o f m assive lim e

stone w hich are developed as w ackestones and m icritic grainstones (Fig. 8d). T his observation corresponds w ell w ith the observations by K och et al. (1994) and Schaller and

K och (1996), according to w hom the m ajor part o f som e Jurassic bioherm al com plexes in southern G erm any (Schw äbischen A lb) is form ed o f so called pelo id sands (peloid - lith o c la s t- ooid sand facies).

B iolithites o f B olechow icka v alley include distinctly less fossils in com parison w ith buildups described from the highest part o f the section (M atyszkiew icz & Felisiak, 1992). The absence o f calcareous algae, thick-shelled b i

valves and gastropods, as w ell as paucity o f Tubiphytes and calcareous sponges indicate deposition w ell below the w ave base.

The original position o f horizontal plane, restored from the analysis o f geopetal infillings in F ilar P okutników is in

clined about 30° to the actual horizon (Fig. 9). It is possible, how ever, that this tilt angle m ay be greater (Fig. 4). The lack o f m arked differences in lithology betw een the rocks sepa

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W P s E **I * « - ;**

^{_____ : _}

F ig .ll Exposure o f w ackestone and clastic sediments on the slope ESE o f Brama B olechow icka (point A in Fig. 2). A fissure filled with weathered marl (black arrow) separates indistinctly bedded wackestone with cherts (below the fissure) from clastic limestones (floatstone-rudstone) alternating w ith marls (above).

Lateral m ovem ents o f sedim ent along arcuate surfaces (white ar

rows) in the clastic limestone are related to slumping disturbances.

Sim ilar disturbances are not observed in wackestone

Fig. 12 Southern part o f B olechow icka valley; w est slope. Filar Pokutników (FP) lies w ithin the zone o f near-fault flexure, which passes southward into brittle deformation. Steep, nearly vertical surfaces on FP are joints (white arrows). Rocks south o f FP are probably separated by fault-plane fissures. The discontinuity sur

faces on FP, sloping southward (black arrows) are low-angle tectonic shears

rated by discontinuity surfaces in F ilar Pokutników and Z am arła T urnia indicate tectonic origin o f these surfaces.

The presen t angles o f dip o f the discontinuity surfaces are the sum o f their prim ary inclination and rotation o f lim e

stone blocks in the vicinity o f faults; the rotation probably occurred during reactivation o f faults.

T he vertical or steeply inclined discontinuity surfaces cutting through the lim estones (Fig. 12) are probably jo in ts belonging to several jo in t system s (see K rokow ski, 1984).

N um erous vertical fractures in the rocks o f the southernm ost parts o f the valley are probably fault planes w idened by karst processes (Fig. 3b), related to the w ide zone o f faults w hich separates the O jców B lock from the K rzeszow ice G raben. A part o f these faults used pre-existing jo in t sys

tem s (cf. G radziński, 1962, p. 479). A different origin have the discontinuity surfaces dipping gently to the south (Fig.

12). A fter th e reduction o f their dip (55°) m easured at the base o f F ilar Pokutników by the angle equal to the inclina

tion o f geopetal structures in sam ple 17, i.e. by 30°, w e ob tain 25° as the angle o f th eir original dip. This dip is sim ilar to dips o f gentle shearing planes in fault-adjacent flexures in the zone o f the northern m argin o f the K rzeszow ice G raben (K rokow ski, 1984). P artial dissolution o f these fractures is due to k arst processes.

The structure o f F ilar W allischa and o f the low er p art o f P iętrow a T urniczka is m arkedly different from that o f the other rocks in B o lechow icka valley. The latter are built m ostly o f fine-grained clastic lim estone (Table 1; Fig. 10).

A part o f its com ponents, i. e. Tubiphytes, m icritized ooids and calcareous sponges o ccur only sporadically in the cyanobacterial-sponge buildups form ing B ram a B olechow ic

ka. Instead, these constituents are com m on in the buildups situated about 150-200 m above the bottom o f the Jurassic and form ed in m uch shallow er sea, w ithin the reach o f the w ave base (M atyszkiew icz & Felisiak, 1992; M atyszkie

w icz, 1996). The occurrence o f cyanobacterial crusts, bor

ings in these crusts and p revalent lack o f sorting and direc

tional structures in the grainstones indicates discontinuous deposition. F ilar W allischa and th e low er p art o f P ię-trow a T urniczka probably represent deposit o f a talus o f a carbon

ate buildup, accum ulated m ostly w hen th e buildup attained the stage o f a T ubiphytes re e f and reached th e zone o f the w ave base. The vertical variability o f the buildup confirm s the distinct shallow ing trend observed during the O xfordian and noted w ithin the w hole area o f the northern sh e lf o f the T ethys ocean (Leinfelder, 1993; L einfelder et al., 1994).

T his trend is especially w ell m arked in th e K raków region because deposition w as not fully com pensated by subsi

dence (Kutek, 1994; M atyszkiew icz, 1994).

D eposition o f the talus sedim ents w as discontinuous and lim ited to the vicinity o f th e carbonate buildup. The sedim ent originated from the destruction o f the buildup was tem porarily laid dow n at its base. D uring the break in the debris supply cyanobacterial crusts covered th e sedim ent surface, stabilizing it and form ing initial rigid fram ew ork.

Poor sorting and rounding o f grains in the clastic lim estones indicate their short transport distance. W ell sorted and rounded sedim ent is present only in P iętrow a T urniczka in thin layers o f diffuse boundaries. T hese layers p robably rep

resent storm sedim ents, laid dow n on a flat, gently inclined bottom . It seem s that the present dip o f the talus sedim ents is m ainly o f tectonic origin. F ilar W allischa and th e low er part o f Piętrow a T urniczka are situated in the sam e distance from the fault zone that separates the O jców B lock from the K rzeszow ice G raben as the m assive lim estones in w hich the flexural deform ation w as ascertained. W e m ay thus suppose th at the clastic lim estones w ere also tectonically disturbed.

Flexural deform ations in hom ogenous m assive lim estones certainly passed southw ards to brittle deform ation, espe

cially at the contact o f tw o lithological varieties. The dis-

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U PPER JURASSIC LIM ESTON ES N E A R BOLECHOW ICE

297

RÓW K R Z E S Z O W I C K I K R Z E S Z O W I C E G R A B E N (RKl

wapien skalisty i uławicony wcip i t-:i i e ziarniste massive and bedded limestone grained limestone fle k s u ra przydyslokacyjna

near fa u lt flexsure

ścięcia połogie s lig h tly inclined shear surfaces

Fig. 13 Interpretation of the structure in the area of Brama Bolechowicka by the present author (A) and Koszarski (1995) (B). A - tectonic blocks in the fault zone which separates Ojców Block (PO) from the Krzeszowice Graben (RK) (without giving account to later differential erosion of Jurassic sediments in PO and RK, and without Quaternary sediments). Near-fault flexure passes southward into discontinuous deformation. The vertical displacement on the main fault consists of displacements on numerous secondary faults, some of which are hinge faults. This results in the occurrence on the slope o f sediments from the younger part of the section, not preserved on PO and dipping in various directions, and of a fault-related megabreccia (for the sakes of clarity not shown on the drawing). Correlation of sediments in isolated outcrops on the slope and estimates of palaeorelief depth are impossible without precise stratigraphical markers

tin c t fracture betw een F ilar W allischa and F ilar A bazego, i.e. at the contact o f the clastic lim estone w ith the m assive lim estone is probably a fau lt fracture w idened by karst dis

solution (Fig. 3b).

The southeastw ard dip o f th e talus sedim ents is pro b ably caused by one o f secondary hinge faults w hose p res

ence in the fault zones o f th e northern m argin o f K rzeszo

w ice G raben w as show n by B ogacz (1967, p. 54). The pres

ence o f hinge faults in th e area o f B olechow ice is also indi

cated by th e presence o f several distinct, flat terraces m ar

ked in th e slope ESE o f B ram a B olechow icka and differen

tiation o f bed dips observed in num erous isolated locations.

The sedim ents exposed on the slope ESE o f B ram a B olechow icka are developed as bedded or non-bedded w ackestone and clastic lim estones. It seem s that the bedded, m ostly, thin-bedded, w ackestone w ith num erous flattened lenses o f chert on bedding planes represents interbioherm al facies, and its non-bedded variety corresponds to peripheral parts o f bioherm s (see M atyszkiew icz, 1989). Interbioher

m al facies form ed on slopes o f the buildups and in depres

sions betw een them , so th a t deposition in situ prevailed du r

ing the initial stage o f the buildup developm ent. A t this stage thick-bedded lim estones w ith cherts originated, w hose m i

crofacies are sim ilar to those o f the m assive lim estone (M atyszkiew icz, 1989). Such sedim ents are not exposed in the area under discussion.

D uring the growth o f the buildup, w hen th e b ottom re

lie f increased, the sedim ent laid dow n in th e interbioherm al depressions w as enriched in carbonate debris and m ud trans

ported from the higher parts o f the buildup. M uch m ore fre

quent supply o f allochem ic com ponents w as reflected in de

creasing thickness o f beds. R egular distribution o f the flat cherts w hich are related to bedding planes points to the lack o f postdepositional deform ations in the w ackestones. Spo

radically observed gentle bending o f the chert lenses are probably o f diagenetic origin. T he occurrence o f Tubiphytes and single corals suggests that these sedim ents are n o t co e

val with the preserved parts o f cyanobacterial-sponge buildups in B ram a B olechow icka and th at they represent in

terbioherm al facies o f buildups developed as Tubiphytes reefs.

C lastic lim estones have various origins. In the greatest o f the described outcrops (Fig. 2: A; Fig. 1) clastic lim e

stones (floatstone-rudstone) intercalated w ith m arls overlie w ackestones. Lateral transition o f clastic lim estones into w ackestones is present in the u pper part o f the outcrop. The presence o f inverse grading in the clastic lim estones indi

cates th at they m ay be turbidites or tem pestites filling an erosional channel elongated in N W -S E direction. N um erous deform ations visible in these sedim ents (Fig. 11) indicate their partial redeposition in a subm arine slum p. T he lack o f clear palaeotransport indices does not p erm it unam biguous

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determ ination o f the position o f the source area. It seem s, how ever, th at these sedim ents represent the m ain phase o f the carbonate buildup destruction, w hich took place at the latest O xfordian (? earliest K im m eridgian) (G łazek & W ier

zbow ski, 1972; M atyszkiew icz, 1994, 1996).

A t another locality (Fig. 2: C) individual beds o f mi- critic clastic lim estones (w ackestone-floatstone) w hich oc

cur w ithin the w ackestones w edge out over a short distance.

Such interfingering o f facies suggests th at the m icritic clas

tic lim estones belong to a talus o f a carbonate buildup, form ed already during th e b u ild u p ’s growth.

It seem s thus that th e exposures situated ESE o f B ram a B olechow icka lie w ithin various tectonic blocks w ithin a fault zone. The occurrence there o f deposits generally y o unger than those exposed in B olechow icka valley is due to tectonic not sedim entary causes. The thickness o f p re served U pper Jurassic sedim ents w ithin the O jców B lock is by m ore than 100 m low er than beneath the bottom o f the K rzeszow ice G raben, because o f erosion. W e m ay thus as

sum e th at the preserved thicknesses o f U pper Jurassic in low ered tectonic blocks w ithin the fault zone increase to w ards the K rzeszow ice G raben, and that top parts o f these blocks contain progressively younger deposits, not pre

served on th e O jców B lock (Fig. 13a).

C orrelation o f sedim ents in isolated exposures o f vari

ous lithology and dip w as m ade by K oszarski (1995) b y as

sum ing (i) the presence o f only one, m ajor fault w hich sepa

rates the O jców Block from the K rzeszow ice G raben and (ii) an a p rio r i determ ination o f age relationships betw een sedim ents in isolated outcrops. The first assum ption p erm it

ted K oszarski (1995) to trea t th e slope north o f B olechow ice village as an incom pletely exposed w all o f an outcrop in w hich all observed dips are o f depositional origin (Fig.

13B). T he consequence o f this assum ption w as purely geo

m etrical connection o f inclined deposits o f various facies from selected outcrops into one depositional syncline (Fig.

13B).

The com plex pattern o f facies relationships in sedi

m ents from isolated outcrops situated on the slope ESE o f B ram a B olechow icka is m ostly the result o f the presence o f hinge faults and o f a m egabreccia zone in the fault zone w hich separates the O jców B lock from the K rzeszow ice G raben (Fig. 13 A). The v ariability o f angles and directions o f dip, im possibility o f stratigraphical correlation in isolated outcrops, and, first o f all, th e com plete lack o f data on facies o f U pper Jurassic deposits in the K rzeszow ice G raben di

rectly south o f B ram a B olechow icka, rule out the possibility o f restoring the positions o f bioherm s, interbioherm al and basinal zones in this area. E stim ates o f p alaeo relief eleva

tions based on the presence o f inclined discontinuity sur

faces in the carbonate buildups in the area o f B ram a B olechow icka (K oszarski, 1995) are devoid o f any support

ing evidence, sim ilarly as th e hypothesis on the p redom i

n ance o f clastic lim estones, not supported by facts.

Acknowledgements

The authors thank the reviewer Professor R. Gradziński for his insightful and helpful review, Professor S. Dżułyński and

Professor J. Rutkowski for discussion and generous help, Profes

sor B. A. Matyja and Docent T. Merta for discussion in the field, Dr T. Leśniak for providing access to the manuscript of the geo

logical map of the vicinity of Bolechowice, Dr I. Felisiak for numerous inspiring discussions and Mrs M. Kuśmierek for draw

ing the figures. The study was supported within the project AGH no. 11. 140. 54.

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Streszczenie

LITOLOGIA I SEDYM ENTACJA GÓRNO- JURAJSKICH W APIENI SKALISTYCH W REJONIE BRAMY BOLECHOW ICKIEJ NA WYŻYNIE KRAKOW SKO-W IELUŃSKIEJ

J a c e k M atyszkiew icz & M arcin K rajew ski

Rejon Krakowa jest położony w południowej części Wyżyny Krakowsko-Wieluńskiej (Fig. 1) cechującej się wyraźną odręb

nością w wykształceniu osadów jurajskich (Kutek, 1994). Odręb

ność ta wyraża się znacznie mniejszą miąższością zachowanych osadów jury (do około 300 m w części wschodniej i znacznie mniejszej w części zachodniej) i ich niekompletnością w stosunku do obszarów położonych na N i E oraz wyraźnymi różnicami w litologii. Przyczyną wyjątkowości obszaru krakowskiego była jego nieznaczna subsydencja w jurze, uwarunkowana występowa

niem w podłożu ciał granitoidów o niskiej gęstości (Kutek, 1994).

Niekompensowanie sedymentacji przez subsydencję (Kutek, 1994; p. 213; Matyszkiewicz, 1994; p. 428) spowodowało, że region krakowski istniał w jurze jako wyraźny element wynie

siony, szczególnie predystynowany do rozwoju budowli węgla

nowych. Analiza wykształcenia litologicznego wapieni jurajskich w okolicy Krakowa wymaga zatem szczególnej staranności i os

trożności w adaptacji modeli opracowanych dla innych obszarów.

Dotyczy to szczególnie rozważań o konfiguracji i głębokości zbiornika jurajskiego zakładających dla całego polskiego frag

mentu szelfu występowanie stałego nachylenia ku Tetydzie (por.

Matyja & Wierzbowski, 1996).

Osady górnojurajskie w okolicy Krakowa są reprezentowane przez utwory oksfordu. Obecność osadów kimerydu nie została na tym terenie udokumentowana paleontologicznie (Głazek & Wierz

bowski, 1972), choć nie można jej całkowicie wykluczyć (Buko

wy. 1962; Matyszkiewicz, 1996). Rozpoziomowanie biostraty- graficzne wyższej części utworów jurajskich jest utrudnione ze względu na ubóstwo amonitów w wapieniach skalistych.

Wykształcenie wapieni w Bramie Bolechowickiej i bezpo

średnio na E od niej było ostatnio przedmiotem rozważań Koszar- skiego (1995), który zaliczył je do wyższej części górnego oks

fordu (/. c.; p. 11), określił ich położenie nad spągiem osadów jury naokoło 170-290 m (/. c.; p. 11) i uznał je za osady redeponowane.

Nachylone powierzchnie w wapieniach tworzących Bramę Bole- chowicką mają zdaniem Koszarskiego (1995) genezę sedymen

tacyjną; “spągowe powierzchnie lawie są erozyjne” (/. c. ; p. 15), a

“poszczególne powierzchnie uławicenia kontynuują się ku N i NW, co widać w dalszych skałach Bramy i Doliny Bolecho

wickiej” (/. c.; p. 15). Osady występujące na zboczu bezpośrednio na ESE od Bramy Bolechowickiej zostały określone przez Koszar

skiego (1995) jako przekracząjąco zalegające “turbidyty i debryty -kalcyrudyty, gradacyjnie przechodzące w kalkarenity” (/. c.; p.

Lithology and sedimentation of Upper Jurassic massive limestones near Bolechowice, Kraków-Wieluń Upland, south Poland