Annales Societatis Geologorum Poloniae (1997), vol. 67: 45-55.
STROMATACTIS CAVITIES AND STROM AT ACTIS-LIKE CAVITIES IN THE UPPER JURASSIC CARBONATE BUILDUPS AT MŁYNKA
AND ZABIERZÓW (OXFORDIAN, SOUTHERN POLAND)
Jacek MATYSZKIEWICZ
U niversity o f M in in g a n d M etallurgy, F aculty o f Geology, G eophysics a n d E n viro n m en ta l P rotection;
al. M ickiew icza 30, 30-059 K raków , Poland. F ax: 0048 12 332936, e-m ail: ja m a t@ g eo l.a g h .e d u .p l Matyszkiewicz, J., 1997. Stromatactis cavities and stromatactis-like cavities in the Upper Jurassic carbonate buildups at Młynka and Zabierzów (Oxfordian, southern Poland). Ann. Soc. Geol. Polon., 67: 45-55.
Abstract: Stromatactis cavities (SCs) and stromatactis-like cavities (SICs) occur in Upper Jurassic carbonate buildups o f southern Poland. The carbonate buildups vary in the development o f their rigid framework. Internal erosion, resulting from various agents, is the process leading to the formation o f the SCs and SICs.
In carbonate buildups o f the cyanobacterial-sponge mud-mound type with weakly developed rigid framework, formation o f the SCs occurred in the subtidal zone, on the slope of a buildup, and was caused by partial winnowing o f unlithified sediment. This winnowing took place during early diagenesis and rapid tectonic uplifting move
ments, when water within large pore spaces and growth cavities was strongly turbulent due to submarine mass flows which resulted in the formation o f a network o f cavities.
In reef-like carbonate buildups o f the Tubiphytes-Teeî type with well developed rigid framework the internal erosion was caused by cavitation linked to intensive wave action in the intertidal zone. The rigid framework, where it was well developed, prevented the formation o f networked cavities permitting the development o f a single SICs only. Such process o f stromatactis formation occurred with a break after the growth of the Tubiphytes-Ke.f.
Precipitation o f sparry calcite cement took place at various stages of the diagenesis. In the SCs formed in the subtidal zone, on the slope of a cyanobacterial-sponge mud mound, the formation of the cements began under marine phreatic conditions and continued during late diagenesis in various environments. In the SICs originated in the intertidal zone in Tubiphytes-reef the early diagenetic cementation usually did not take place because the stromatactis were subaerially exposed soon after their formation. Some o f them were slightly restructured and got filled with cement as a result o f hydrothermal processes in Tertiary time.
Abstrakt: W górnojurajskich budowlach węglanowych południowej Polski występują kawerny stromatactis (SCs) i kawerny stromatactis sensu lato (SICs). Budowle te charakteryzują się zróżnicowanym rozwojem sztyw
nego szkieletu. Procesem odpowiedzialnym za tworzenie się SCs i SICs jest erozja wewnętrzna osadu wywołana różnymi czynnikami.
W budowlach węglanowych typu cyjanobakteryjno-gąbkowych kopców mułowych o słabo rozwiniętym szkielecie wewnętrznym tworzenie się SCs zachodziło na stoku budowli, w strefie sublitoralnej i było spowodo
wane wymywaniem części niezlityfikowanego osadu. Wymywanie to miało miejsce we wczesnej diagenezie, podczas gwałtownych, tektonicznych ruchów wznoszących, kiedy woda wypełniająca przestrzenie między- porowe i kawerny wzrostowe ulegała silnej turbulencji w wyniku oddziaływania spływu podmorskiego powo
dując powstanie systemu połączonych kawern.
W rafopodobnych budowlach węglanowych typu rafy tubiphytesowej o dobrze rozwiniętym szkielecie wew
nętrznym erozja wewnętrzna była spowodowana przez erozję kawitacyjną wywołaną oddziaływaniem intensyw
nego ruchu falowego w strefie międzypływowej. Dobrze rozwinięty sztywny szkielet zahamował rozwój sytemu połączanych kawern, co doprowadziło do utworzenia jedynie pojedynczych SICs. Tworzenie się SICs zachodziło w tym wypadku z hiatusem czasowym względem wzrostu rafy tubiphytesowej.
Wytrącanie cementu węglanowego miało miejsce w różnych stadiach diagenezy. W SCs powstałych w subli- torale, na stoku cyjanobakteryjno-gąbkowego kopca mułowego tworzenie się cementów rozpoczęło się w mors
kich warunkach freatycznych i było kontynuowane podczas późnej diagenezy w różnych środowiskach. W SICs powstających w strefie międzypływowej, w rafie tubiphytesowej wczesnodiagenetyczna cementacja nie miała zwykle miejsca na skutek ich wynurzenia niedługo po utworzeniu. Część SICs została przemodelowana i wypeł
niona cementami krystalizującymi z roztworów hydrotermalnych w trzeciorzędzie.
Key words: stromatactis, carbonate buildup, Upper Jurassic, Kraków region, Southern Poland.
Manuscript received 3 March 1996, accepted 2 April 1997
46
J. MATYSZKIEWICZINTRODUCTION AND GEOLOGICAL SETTING
The term strom atactis denotes “ a spar netw ork, w hose elem ents have flat to undulose sm ooth low er surfaces and digitate u pper surfaces, m ade up principally o f isopachous crusts o f centripetal cem ent and em bedded in finely crystal
line lim estone” (B ourque & B oulvain, 1993, p. 608). T hese sparry m asses are m ostly cem ent-filled upper parts o f cavi
ties, usually about 1 to 3 cm thick (B athurst, 1959; 1982).
T he sm ooth base o f the strom atactis is m ostly developed on internal sedim ent.
C em entation and filling w ith internal sedim ent occur usually w ith a tim e hiatus after the form ation o f th e cavities, and in som e cases m ay n o t occur a t all. T he cem ent and in
ternal sedim ent filling th e cavities m ay also be leached or w ashed out. T aking this into account, tw o new term s are proposed (Tab. 1): ‘strom atactis ca v ities’ (SC s) and ‘stro- m atactis-like ca v ities’ (SICs).
S trom atactis are observed m ainly in carbonate buildups o f the m ud-m ound type o r on th eir flanks (Pratt, 1995). The strom atactis occur m ostly in deep-w ater carbonate buildups, but they are also know n from shallow -w ater deposits (M ac
D onald e t al., 1994; S tenzel & Jam es, 1995). It seem s that one term ‘stro m atactis’ denotes structures w ith different ori
gins. T he hitherto existing opinions on the origin o f strom a
tactis m ay be divided in tw o m ajor groups. The first one in
cludes th o se w hich link strom atactis w ith organic structures or their diagenesis (D upont, 1881, 1882; Low enstam , 1950;
Bathurst, 1959; P hilcox, 1963; Textoris & Carozzi, 1964;
Shinn, 1968; B echstädt, 1974; C oron & Textoris, 1974;
B ourque & G ignac, 1983; Tsien, 1985; B eaucham p, 1989;
B ourque & B oulvain, 1993; Flajs & H üssner, 1993, H ussner et al., 1995). T he second group are those w hich ascribe vari
ous p hysical processes as fundam ental in the form ation o f strom atactis (S chw arzacher, 1961; Lees, 1964;K ukal, 1971;
H eckel, 1972; Ross et al., 1975; Logan & Sem eniuk, 1976;
B athurst, 1982; Pratt, 1982, 1995; W allace, 1987; M atysz-
Table 1
P roposed term inology
Stromatactis
“a spar network, whose elements have flat to undulose smooth lower surfaces and digitate upper surfaces, made up principally of isopachous crusts and centripetal cement and embebdded in finely crystalline limestone” (after Bourque & Boulvain, 1993)
Stromatactis cavities (SCs)
a cavity network, whose surfaces are digitate, as a whole or partly filled with spar cements and/or internal sediment, embedded in finely crystalline limestone
Stromatactis-like cavities (SICs)
isolated cavities, whose upper surfaces are digitate, as a whole or partly filled with spar cements and/or internal sediments, embedded in finely crystalline limestone
Fig. 1. Location of the Mlynka and Zabierzów quarries in the Cracow region
kiew icz, 1993; M acD onald e t a i , 1994).
The U pper Jurassic (O x fo rd ian -?K im m erid g ia n ) depo
sits in the vicinity o f C racow represent probably tw o indis
tin c t shallow ing sequences (M atyszkiew icz, 1994, 1996).
Each o f them begins w ith condensed deposits and platy lim estones, w hich locally contain m arly intercalations and isolated sm all bioherm s. A bove, in both sequences, dom i
nate strongly differentiated ca rbonate buildups w ith their flank beds and bedded facies. E ach sequence is topped with subm arine m ass flow deposits, w hich also m ay be locally observed in the w hole profile.
In the cyanobacterial-sponge buildup at M lynka quarry near C racow (Fig. 1) strom atactis (m ore precisely; strom a
tactis cavities - SCs) w ere observed and interpreted as a constructional grow th-fram ew ork cavity system m odified by w innow ing o f lim e m ud by tu rb u len t w ater (M atyszkie
w icz, 1993). A proposed m odel o f SCs developm ent refers to cyanobacterial-sponge m ud m ounds w ith incipient but differentiated rigid fram ew ork (reticulate and lam inar fram ew ork; sensu Pratt, 1982). T he buildups o f this type, visible at M łynka, developed m ainly in th e m iddle and late M iddle O xfordian below w ave base at a m oderate depth.
E ven if this process could operate during early diagenesis in w eakly or m oderately lithified sedim ent, its role in th e for
m ation o f SCs in strongly lithified sedim ents is rath er d oubt
ful. O bservations o f sedim entary structures o ccurring in an
other exposure, at Z abierzów (Fig. 1), in a carbonate b u ild
up o f the T u biphytes-rzef type w ith a w ell developed rigid fram ew ork, have lead to expansion o f th e pro p o sed m odel and its linking w ith th at p articular ty p e o f carbonate buildup.
Methods
T he m ain research m ethods included field observations and m icrofacies analysis and w ere supported by the follow ing techniques. P olished thin section w ere studied using a
STROMATACTIS CAVITIES IN UPPER JURASSIC BUILDUPS 4 7
C am bridge Im age T echnology Ltd. C old C athode Lum ino- scope M K -III-8300 operating under 15-18 kV beam energy, 400 m A beam current, w ith a variable beam diam eter. Trace elem ents analyses w ere conducted using electron m icro
p robe A R L SEQ M at 15 nA beam energy and at 20 kV, w ith the beam diam eter o f ab o u t 1 m m . D etection lim its are for Mn 140 ppm , for M g 360 ppm , for Fe 190 ppm , and for S 160 ppm . A nalyses o f carbon and oxygen stable isotopes w ere carried out at Institut fur M ineralogie der U niversität E rlangen-N üm berg by D r. M . Joachim ski.
MEZOSCOPIC OBSERVATIONS
S trom atactis cavities (SC s) at M łynka (Tab. 2) are no longer visible because o f th e progress in quarrying. A t the end o f 1980s the SCs occurred w ithin the flank beds o f a large cy an obacterial-sponge m ud m ound (H offm ann & M a
tyszkiew icz, 1989; M atyszkiew icz, 1993), intersected by a vertical neptunian dykes. T he SCs at the M łynka quarry w ere visible in a 1.5 m th ic k zone in the upperm ost part o f slope sedim ents o f th e cyanobacterial-sponge m ud m ound.
T he p reserved part o f th is carbonate buildup, determ ined previously as the low er-m iddle M iddle O xfordian (P licati- lis-T ra n sversa riu m Z ones; H offm ann & M atyszkiew icz,
1989), m ay be slightly younger, representing the u pper M id
dle O xfordian (B ifurcatus Z one) also (B. A. M atyja; pers.
com m ., 1995).
C alcified siliceous sponges together w ith cyanobacte- rial crusts build initial rigid-fram ew ork o f the m ud m ound (cf. M atyszkiew icz, 1994; M atyszkiew icz & K rajew ski, 1996). Incipient fragm ents o f lam inar fram ew ork occur at
T a b le 2 M ezoscopic com parison o f strom atactis cavities from
cy an obacterial-sponge buildup and strom atactis-like cavities w ithin Tubiphytes-re e f
Stromatactis cavities Stromatactis-like cavities Type o f carbonate
buildup
Cyanobacterial-
sponge mud mound Tubiphytes reef
Locality Młynka quarry Zabierzów quarry
Rigid framework incipient laminar
and reticulate well-grown Stratigraphie
position Middle Oxfordian Upper Oxfordian Colour o f the
limestone light light, locally dark
Filling cement and
internal sediment
usually internal sediment (light limestone); cement and internal sediment (dark limestone)
Fig. 2. The SICs in the light variety of the Tubiphytes-reef at Zabierzów
th e slope o f the carbonate buildup w hereas the centre o f the buildup consists o f a reticulate fram ew ork (M atyszkiew icz, 1993; cf. Pratt, 1982). The SCs w ere observed in light, m as
sive lim estone. T hey are up to one cm high, som e centim e
tres w idth, and filled in th eir upper parts w ith cem ent and in the low er parts w ith internal sedim ent.
T he O xfordian strata exposed at Z abierzów represent the upperm ost part o f the Jurassic deposits in the C racow area, and belong probably to the U pper O xfordian (Bimmci- m atum /P lanula Z ones). A t Z abierzów quarry the SICs occur on the upperm ost bench, in m assive, light b u t sporadically dark, highly porous lim estone (Tab. 2; Fig. 2). T he organic form s recognizable m acroscopically include m o stly Tubi
p h ytes and strom atolites, accom panied by brachiopods (m ainly Terebratulina substriata S chlotheim and Sellithyris engeli (R ollier) - pers. com m . M. K robicki, 1995), crabs, fragm ents o f bivalves, sm all gastropods, siliceous and cal
careous sponges, ju v e n ile am m onites and polychaetes. The dom inant role o f Tubiphytes and th e presence o f num erous growth cavities allow to classify this lim estone as a so- called T u biphytes-reef (cf. P o m oni-P apaioannou et al., 1989; M atyszkiew icz & Felisiak, 1992) w ith w ell-grow n rigid fram ew ork.
The SICs observed in the light lim estone at Z abierzów are usually n o t filled w ith cem ent. O nly on the w alls o f larger cavities thin cem ent rim s are occasionally present.
T he SICs are spread som e centim eters apart. T hey are on av
erage about 2 cm high and som e centim etre w ide. T ypical features o f these cavities include uneven, digitate ro o f and sm ooth bottom . M acroscopically distinguishable com po
nents o f th e internal sedim ent include T ubiphytes and frag
m ented polychaetes cf. Terebella sp. Som e o f the cavities are filled w ith soft, light-greenish or y ellow ish clay w hich does not contain m icrofauna and p robably represents T erti
ary karst deposits (Felisiak, 1992).
The SICs m ay also be observed in the dark lim estone w hich occurs now only in the rubble. T he lim estone w as ob
served in situ in the 1950s by D żułyński & Ż abiński (1954).
T he biota w hich m ay be m acroscopically discernible are the sam e as in the light lim estone. T he dark colour grades lo
cally, on the distance o f 1-2 m m , into the typical cream y one. The form s and sizes o f SICs are sim ilar as in those in
4 8 J. MATYSZKIEWICZ
the light lim estone. The essential difference consists in the filling o f cavities above the internal sedim ent w ith dark-grey cem ent.
MICROSCOPE OBSERVATIONS
T he SCs from cyanobacterial-sponge m ud m ound at M łynka occur in the cyanobacterial-sponge crust, strom ato- lite/throm bolite boundstone and in tuberolitic/peloid w acke- stone (Fig. 3; M atyszkiew icz, 1993). The upper parts o f SCs are filled w ith several types o f cem ent (Tab. 3). The w alls are lined b y thin granular isopachous o r radiaxial (fibrous and bladed) cem ents (Fig. 4). The fibrous and bladed rad ia
xial cem ents occur in optical continuity. The pore space are filled w ith blocky granular cem ent, but the centres o f largest cavities are filled w ith p oikilotopic cem ent. The radiaxial and blocky cem ents are generally inclusion-rich. O nly large crystals o f the p oikilotopic cem ent do not contain inclu
sions. Internal sedim ent w ith in the SCs is com posed o f p e
loid w ackestone, but the up p erm o st parts o f the internal sed
im ent consist locally o f p eloidal packstone w ith blocky ce
m ent.
The Tubiphytes-Tzei w ith SICs at Z abierzów is devel
oped as boundstone or locally as nest-filling grainstone. Its m ain com ponents are m o stly irregular Tubiphytes w ith thick outer crust, single-envelope oncoids and peloids, w hich m ay also be observed in lam inated strom atolites. Fauna is abun
dant and represented by fragm ents o f bivalves, echinoids, brachiopods, calcified fragm ents o f siliceous sponges, cal
careous sponges, bryozoans, foram inifers, polychaetes, fine gastropods an d juv en ile am m onites. M ost grains are covered w ith rim s o f isopachous g ranular cem ent or radiaxial fibrous and radiaxial bladed cem ent. The centres o f sm all cavities (up to 5 m m ) in boundstone and voids in grainstone are filled w ith blocky granular and poikilotopic cem ent. The ra
diaxial and blocky cem ents are inclusion-rich.
In the light lim estone at Z abierzów the SICs are usually not filled w ith cem ent. O nly sporadically a thin (up to 0.2
F ig. 3. T h e SC s in th e c y an o b a cterial-sp o n g e build u p at M łynka. Sp - calcified silice o u s sponges. T he u p p er parts o f SCs are filled w ith cem ents. T h e internal sed im en t (is), filling the low er parts o f the SC s, is clearly seen. T h in section, nicols p arallel, scale bar 4 mm
F ig. 4. T h e SC s in the c y a n o b a cte ria l-sp o n g e m u d -m o u n d at M łynka. T he r o o f p art o f the SC s is filled w ith rad iax ial (rc) and blocky calcite (be) cem ents. T h e internal se d im e n t (pelo id al w ack esto n e (is) is distin ctly lighter th an th e su rro u n d in g host-rock.
T ubiphytes (T), w h ich are rare at M ły n k a, to g eth e r w ith other cy an o b acteria l stru ctu res locally form frag m e n ts o f th e rigid fram ew o rk resistan t to internal ero sio n . T h in sectio n , nico ls p aral
lel, scale bar 0.2 m m
m m ) rim o f the isopachous g ranular cem ent lines the w alls o f cavities (Fig. 5). This rim is som etim es th ick er at the ro o f o f a SICs and reaches 0.4 m m in w idth. Sm all SICs, som e m illim eters across, are occasionally com pletely filled w ith blocky granular and poikilotopic cem ents w ith o u t in clu sions. Internal sedim ent filling the low er parts o f large cav i
ties is represented by grainstone w ith collapse features or by packstone-w ackestone.
The dark lim estone at Z ab ierzó w is sim ilarly devel
oped. The differences are related to th e cem ent w ithin the SICs. It is com posed o f crystals approx. 0.3 to 0.4 m m across, w hich are inclusion-rich and contain dark intercrys- talline insertions. In polarized light these crystals form a m osaic. W ithin this cem ent there are em bedded single, an
gular rock fragm ents (Fig. 6), derived from the lim estone adjacent to the cavities. The cem en t locally disturbs the flat surface o f the internal sedim ent (Fig. 6). T he roofs o f SICs are m ore sm ooth than in the light lim estone. The described cem ent m ay be observed only in large cavities, but sm aller (up to 1 m m w ide) fractures branching from th e SICs are som etim es filled w ith blocky g ranular and poikilotopic ce
m ents w ithout inclusions (Fig. 7).
STROMATACTIS CAVITIES IN UPPER JURASSIC BUILDUPS 49
F ig . 5. T h e SIC in the T u b ip h ytes-\'ceï at Z ab ierzó w (the light lim estone). O n ly the w alls o f the SIC are lined w ith a thin rim o f the iso p ach o u s g ran u lar cem en t (arrow ). T h in section, nicols crossed, scale bar 2 m m
C a th o d o lu m in e sc e n c e
T he cem ents filling SCs in cyanobacterial-sponge buildup show differentiated lum inescence (Tab. 3): radia- xial cem ent is non-lum inescent, and the rem aining ones show lum inescence from dull- to m edium orange. The m ost contrasting lum inescence effects are those betw een the blocky granular cem ent and the poikilotopic w ithout inclu
sion one.
A ll the observed cem ents w ithin the SICs from Tubi- p h y te s-re e f at Z abierzów show lim inescence (Tab. 4). The internal texture o f the clasts is better visible under the lumi- noscope. T he clasts o f sedim ent em bedded in the cem ent filling the SICs in the dark lim estone w ere subject to m ore detailed analyses. T hey reveal distinct traces o f dissolution along th eir edges. The traves o f dissolution also occur along the borders o f cavities filled w ith a late cement.
F ig. 6. T h e SIC in the T u b ip h y te s -K c f at Z ab ierzó w (the dark lim estone). T h e arrow sh o w s th e d irec tio n o f the roof. T he top o f the SIC is locally oval. O n e g e n era tio n o f th e cem en t w ith n u m er
ous in tercry stallin e in se rtio n s is visible. T h e cem en t encloses clasts d eriv ed from the a d ja c e n t host-rock. T he internal sedim ent (is) is d istin c tly d istu rb ed b y the cem ent. T h in section, nicols parallel, scale bar 3 mm
F ig. 7. T h e SIC in the T u b ip h y te s-v se i at Z ab ierzó w (the dark lim estone). In the p a rt o f the SIC clo se to the roof, thin fractures b ran ch in g from the cav ity are filled w ith the tran s p are n t blocky cem en t (be). T h e m ajo r p a it o f th e SIC is filled w ith th e late cem en t (lc) co n ta in in g n u m ero u s in te rcry sta llin e insertions. O n the w alls o f the SIC are locally p re serv e d relicts o f th e isop ach o u s gran u lar cem en t (arrow ). T hin section, n ico ls p arallel, scale bar 1 m m
ISOTOPE AND OTHER GEOCHEMICAL DATA
Isotope and geochem ical investigations o f cem ents fill
ing SCs w ithin cyanobacterial-sponge buildup at M łynka w ere carried out on th e bulk sam ple because o f problem s w ith cem ent separation. As the cem ents w ere taken from the central parts o f a large SCs it is assum ed that they represent m ostly the blocky granular and poikilotopic cem ents. Iso-
T a b le 3 A sum m ary o f cem ents in the strom atactis cavities from
cyanobacterial-sponge m ud m ound at M lynka
Cement Habits Size Inclusions Lumine
scence Remarks isopachous
granular
crusts on wall
up to 0.1
mm absent medium
orange radiaxial
fibrous
radial, fibrous crusts
up to 0.8
min dusty absent
radiaxial bladed
radial, bladed crusts
up to 0.8
nun dusty absent
in optical continuity with the radiaxial fibrous cement blocky
granular
equant to inequant
up to 1
mm dusty dull
orange poikilotopic equant to
inequant
up to 1.2 mm
rare or absent
medium ornage' blocky
within internal sediment
equant to inequant
up to 0.3
mm absent medium
orange
7 — Annales..
50
J. MATYSZKIEWICZTable 4
A sum m ary o f cem ents in the strom atactis-like cavities from T ubiphytes-re e f at Zabierzów
Cement Habits Size Inclusions Lumine
scence Remarks isopachous
granular
crusts on wall
up to 0.4
mm absent medium
orange blocky
granular equant up to 0.5 mm
rare to absent
medium orange poikilotopic equant to
inequant
up to 2.5
mm absent medium
orange late cement equant 0.4-0.5
mm dusty yellow-
orange
poikilotopic equant to inequant
up to 1.2 mm
rare or absent
medium ornage
only in dark limestone blocky
within internal sediment
equant to inequant
up to 0.2
mm absent medium
orange
topic investigations o f cem en t w ithin the SICs from Tubi- p h y te s-re e f at Z abierzów w ere carried out on the late cem ent from the dark lim estone. T he rem aining isotope determ ina
tions w ere carried out on th e m atrix o f the cyanobacterial- sponge buildup from M łynka and the dark lim estone from T ubiphytes-re e f at Z abierzów (Tab. 5).
The results are p resented in Figure 8 against the curve designating average S '^ C and 5 IS0 values for brachiopods from central Poland (H offm an et al, 1992; P isera et al.,
1992). T he stratigraphie position o f the studied sam ples are approxim ate. The 8 80 values in th e cem ents from cyano
bacterial-sponge buildup at M łynka and T u b ip h yte s-xœ î at Z abierzów are significantly low er than respective values for the m atrix, and are particularly low in the cem ents from Zabierzów . T he 8*'"’C values for the m atrix from both locali
ties and for th e cem ents from the SCs at M łynka are com pa
rable, and th e y are slightly higher than those for the cem ents w ithin the SICs from dark type o f lim estones at Zabierzów .
Trace elem ent analyses show that the M n content o f the late cem en t in T ubip h ytes-reef from Z abierzów averages 506 ppm , w hereas in the cem ents from cyanobacterial-
S 13C 5180
Fig. 8. 5 I3C and Sl80 data measured in cements of the SCs, SICs and matrix of limestones at Mlynka and Zabierzów. The
Il 18
curve illustrating the variability of S C and 8 O during the Oxfordian and Early Kimmeridgian contains data obtained for brachiopod shells from central Poland (Hoffman et al., 1992). Z - approx. stratigraphie position o f Zabierzôw-quarry, M - strati
graphie position of Mlynka-quarry
Table 5
Results o f trace elem ent analysis and isotopic com position o f cem ents in strom atactis cavities from cyanobacterial- sponge m ud m ound at M łynka an d strom atactis-like cavi
ties w ithin Tubiphytes-re e f (dark lim estone) at Z abierzów
S tro m atactis cav ities S tro m atactis-lik e cav ities Type o f
carbonate buildup and locality
Cyanobacterial-sponge mud mound
Mlynka
Tubiphytes-reef (dark limestone)
Zabierzów
Type of cement
Radiaxial (fibrous and
bladed), blocky and poikilotopic cements
n= 6
Matrix n= 1 2
Late cement 11=6
Matrix 11=8
Mn 280±140
(110-560)
280±30 (130-400)
506±380 (230-680)
240±160 (10-430)
Mg 1170±490
(550-2120)
1615±270 (950-2240)
921±740 (10-1500)
1677±40 (1470-2460)
Fe 3850±4730
(10-12790)
3940±340 (330-13430)
5335±6250 (450-13040)
66±95 (10-190)
S 140±90
(10-290)
269±210 (40-1340)
3908±6020 (60-11390)
630±230 (310-1960)
5 I80pdb
-3.79%o n= 2
-1.42%o n=l
-6.85%o n= 2
-2.08%o n=l
S13Cpdb
2.36%o n= 2
2.12%o n=l
1.34%«
n= 2
2.66%o n=l
sponge buildup from M łynka it is distinctly low er, w ith an average o f 280 ppm . The M g content o f the cem ent is defi
nitely low er than that o f the m atrix, both in the cyanobacte
rial-sponge buildup and the Tubiphytes-reef. W ithin the late cem ent from T ubiphytes-reef there are p laces distinctly en
riched w ith S and Fe in com parison to the m atrix.
DISCUSSION
The results obtained here suggest that the SCs in the cy- anobacterial-sponge m ud m ound at M łynka and the SICs in the Tubiphytes-reet' at Z abierzów d iffer in origin. T his is due to differences in the developm ent o f these tw o types o f car
bonate buildups.
The carbonate buildup at M łynka, o f the m ud m ound type, w as developed in the subtidal zone, at a m oderate depth below the w ave base. D uring form ation o f the SCs a significant role w as p layed by internal erosion resulting in w innow ing o f the unlithified p arts o f the sedim ent (cf. Pratt, 1982, 1995; W allace, 1987; M atyszkiew icz, 1993; M ac
D onald e t al., 1994). T he w in now ing occurred on slopes o f the cyanobacterial-sponge buildup w here its rigid fram e
w ork w as only partly developed and som e fragm ents o f sedim ent w ere still unlithified (cf. P ratt, 1982; M atyszkie-
STROMATACTIS CAVITIES IN UPPER JURASSIC BUILDUPS
51
w icz, 1993). The turbulence w as probably induced by sub
m arine m ass flow s (Fig. 9; M atyszkiew icz, 1993). The SCs w ere nex t filled by cem ents in early and late stages o f dia
genesis.
The 5 180 values for th e m atrix and cem ents filling stro
m atactis in cyanobacterial-sponge buildup from M łynka are situated left o f the reference curve obtained for brachiopods (H offm an e t a l., 1992; P isera et al., 1992), as the form er are m ore prone to diagenetic alterations in com parison w ith the b rachiopod shell m aterials (H udson, 1977). It seem s that the significantly low er 5 180 values, relatively unchanged ô l3C values in com parison w ith the brachiopod shells, and the generally ferroan com position suggest a burial or a m eteoric origin o f the cem ents (cf. L ohm ann, 1988; Bourque & R a y m ond, 1994; R einhold, 1996) w ithin the SCs from cyano- bacterial-sponge m ud m ound at M łynka.
The succesion o f filling the SCs in cyanobacterial- sponge buildup at M ły n k a w ith cem ents has been estab
lished on the basis o f cathodolum inescence analysis. A t first, th e inclusion-rich, non-lum inescent radiaxial fibrous and bladded cem ents w ere precipitated. The lack o f lum i
nescence in the radiaxial cem ents indicates that they w ere form ed during early diagenesis u nder active m arine phreatic conditions (cf. M achel, 1985; B ourque & R aym ond, 1994).
T he blocky granular cem en t that fills the central parts o f cavities and shows w eak lum inescence w as probably form ed slightly later under m ixed, freshw ater-m arine ph rea
tic conditions (cf. L ongm an, 1980). The poikilotopic cem ent w ith yellow -orange lum inescence was form ed in late d i
agenesis either in the vadose zone or during burial diagene
sis (cf. M oham ad & T ucker, 1992). The genesis o f the thin rim s o f isopachous granular cem ent w ith distinct, m edium - orange lum inescence is not clear. They represent probably a neom orphic cem ent, originating from replacem ent o f the prim ary m arine isopachous cem ent in stagnant fresh-w ater phreatic zone (cf. A m ieux e t a l , 1989).
In the carbonate buildup o f T ubiphytes-reef type at Z abierzów a fully rigid fram ew ork w as developed early, and com plete early lithification took place. Thus, it is not pro b able that the SICs resulted from w innow ing o f the unlithified parts o f sedim ent. The internal erosion o f sedim ent m ay be, therefore, explained in term s o f high-energy processes. It seem s th at cavitation m ay be seen as the process responsible for the form ation and d evelopm ent o f cavities in the early and co m pletely lithified deposits.
C avitation, understood in term s o f the inability o f a v is
cous liquid to transfer tensile strain under conditions o f a rapidly low ered pressure, m anifests itself as the loss o f the liquid continuity and form ation o f cavities w ithin the liquid.
C avitation follow ed by cavitational erosion stipulates the presence o f undissolved gas bubbles, so-called cavitation nuclei, w ith diam eters 1 0 ° -1 0 " 7 m (Terao & Ito, 1981). The gas dissolved in this liquid does not practically affect its proneness to cavitation (K napp e t al., 1970).
The developm ent o f fine bubbles into big ones during cavitation proceeds u nder conditions o f a suddenly d e
creased pressure. In turn, due to a sudden increase in pres
sure a bubble becom es strongly flattened and, then, a d e
pression form s in it. This depression m ay be pierced by a high-energy m icrojet o f the liquid w hich represents the
S e a le v e l
intensive w a te r turbulence zone
microbial siliceous —
crusts
Û
* sponges withepifauna
' S
other bioclasts
wackestone to packstone
turbulence of water within growth cavity
Fig. 9. Development o f the SCs in a carbonate buildup with an initial stage of the rigid framework (partly after Matyszkiewicz, 1993). The cyanobacterial-sponge buildup developed at a moder
ate depth below wave base. The incipient laminar rigid framework was a delicate construction composed o f cyanobacterial crusts and calcified siliceous sponges. Most o f the spaces between the frame
work was filled with the soft carbonate mud, but part o f the pore spaces and growth cavities was filled with sea water. Strong water turbulence, resulting from a mass flow induced by tectonic upward movements, caused washing out o f the soft sediment around pore spaces and growth cavities and development a cavity network.
This course o f an internal erosion led to remodelling and the
“upward migration’7 o f cavities (cf. Wallace, 1987)
52
J. MATYSZKIEWICZSea le v e l
Wave base
Tubiphytes and other microbial
features
ixP < r
packstone
to grainstone )
bioclasts
cavitation within growth cavity
Fig. 10. Development of the SICs in a carbonate buildup with a well-grown rigid framework. The Tubiphytes-rseï was primarily formed near wave base and have been subsequently shifted above the wave base. The rigid framework was a massive construction built o f Tubiphytes and other cyanobacterial features. Within this framework there were numerous growth cavities, incrusted with fauna. The buildup was affected by waves when it was in the intertidal zone. Sudden and repeating many times changes of the pressure gradient resulted in cavitational erosion o f primary growth cavities but the well-grown, strong lithified rigid frame
work stopped a formation o f cavity network
proper factor o f the cavitational erosion. L aboratory obser
vations prove th at such bubbles are num erous, and grow and im plode close to each other or to surrounding surfaces (K napp e t al., 1970). This observation corresponds well w ith th e sw arm occurrences o f the SICs.
It m ay be accepted that cavitation explains w ell the in
ternal erosion w ithin strongly lithified lim estones (Fig. 10).
In carbonate buildups w ith rigid fram ew ork w hich w ere rich in growth cavities, the presence o f cavitation nuclei in the form o f bubbles o f undissolved gas seem s obvious. T he in
tertidal zone is an environm ent in w hich cavitation plays an im portant role as changes o f th e pressure caused by the w ave action are particularly strong and repeat m any tim es (Fig. 10).
T he T ubiphytes-re ef at Z abierzów form ed n ea r th e w ave base in th e period o f distinct shallow ing o f th e Jurassic basin in the vicinity o f Cracow . H ow ever the SICs did n o t develop w ithin it during early diagenesis but after a hiatus, and re
sulted from strong w ave action. It w as a process w hich be
gan during the Late Jurassic regression and later recurred during num erous transgressions and regressions during the C retaceous.
The lack o f cem ent above th e internal sedim ent in m ost SICs in the Tubiphytes-re e f results probably from subaerial exposure o f the sedim ent soon after the form ation o f the SICs. The isopachous granular cem ent, lining som etim es the cavity walls, indicates p robably a short m arine episode, w hen the sea w ater filled the cavities. Burial diagenesis took place at the end o f the C retaceous and in the T ertiary, but the significant dim ensions o f the SICs caused that they could not be filled by capillary-draw n fluids, from w hich cem ents could have precipitated. Still later, under the continental conditions w hich prevailed in th e vicinity o f C racow in T er
tiary tim e, part o f the SICs w ere filled w ith greenish clay o f continental origin (Felisiak, 1992).
The cem ent filling the SICs in th e dark lim estone defi
nitely differs in hand specim ens from the other cem ents.
T his observation is confirm ed by (i) the M g content o f this cem ent, distinctly low er in com parison w ith the m atrix, (ii) the yellow -orange lum inescence definitely different than in other cem ents, and (iii) the 5 O values, distinctly low er than the ones an th e M fynka-quarry. A ll these data suggest that th e cem ent in question w as form ed during epigenetic processes. The dissolution p henom ena observed along the borders o f cavities, filled w ith th e late cem ent, indicate clearly the corrosive action o f solutions, from w hich the ce
m ents precipitated. It seem s th at the late cem ent m ay be linked w ith low -tem perature h y drotherm al solutions (cf.
Lohm ann, 1988; R einhold, 1996) reported from the C racow area (M orozew icz, 1909; D żułyński & Ż abiński, 1954; M a- tyszkiew icz, 1987; R einhold, 1996).
The results o f m icroprobe investigations confirm that the substance w hich locally im parts th e grey colour o f lim e
stone is finely dispersed pyrite (cf. D żułyński & Żabiński, 1954). The total content o f pyrite is very low and often the m ineral is not identifiable by classical analytical m ethods.
Pyritization took place p robably in th e M iocene, w hen the platform sedim ents w ere faulted. T he fault zones w ere m a
jo r conduits for solutions from w hich pyrite-rich cem ents precipitated in the dark lim estone. T he m ineralization o f the
STROMATACTIS CAVITIES IN UPPER JURASSIC BUILDUPS
53
m atrix w ith pyrite resulted from penetration o f these solu
tions along stylolite seam s (cf. Braithw aite, 1989). This low -tem perature hydrotherm al m ineralization also caused a local infilling o f the already existing SICs. As the tem pera
tures o f these solutions w ere low and the tim e o f their action w as short, the prim ary shape o f the SICs has only been slightly m odified through dissolution.
Acknowledgements
The author expresses his thanks to Prof. A. Kostecka, Dr. B.
R. Pratt, Dr. A. Świerczewska and Dr. J. Motyka for the critical reading o f the earlier versions of the manuscript and to Prof. H.
Seyfried and Dr. M. Nose for inspiring discussions. Thanks are also due to Dr. M. Joachimski for isotopic analyses and to Dr. A.
Skowroński for his assistance with the English. This research was supported by University of Mining and Metallurgy (project no. 10.
140. 75.) and Alexander von Humboldt Foundation.
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S tre s z c z e n ie
K A W E R N Y S T R O M A T A C T IS I S T R O M A T A C T IS S E N S U L A T O W G Ó R N O J U R A J S K IC H B U D O W L A C H W Ę G L A N O W Y C H W M Ł Y N C E
I Z A B IE R Z O W IE (O K S O R D , P O Ł U D N IO W A P O L S K A )
J a c e k M atyszkiew icz
S tosow anie term inu „strom atactis” je s t zasadniczo ograniczone do cem entu sparytow ego stanow iącego w ypeł
nienie górnej części system u kaw ern (B athurst, 1959; 1982;
B ouque & B oulvain, 1993). W tym znaczeniu term in ten nie uw zględnia całości w ypełnienia, które w dolnej części ka
w ern tw orzy zw ykle sedym ent w ew nętrzny. P rzy zachow a
niu klasycznej definicji strom atactis proponuje się dw a now e term iny (Tab. 1): „kaw erny strom atactis” (SC s) i „ka
w erny strom atactis sensu lato” (SICs).
G óm ojurajskie budow le w ęglanow e okolicy K rakow a cechują się różnym stopniem rozw oju sztyw nego szkieletu.
W budow lach typu cyjanobakteryjno-gąbkow ych kopców m ułow ych rozw ijających się generalnie poniżej podstaw y falow ania szkielet ten je s t rozw inięty słabo. W centralnych partiach budow li je st on w ykształcony w postaci tzw. szkie
letu siatkow atego (reticulate fram ew ork; sen su Pratt, 1982), natom iast na stokach budow li w ystępuje inicjalny szkielet lam inam y (lam inar fram ew ork; sen su Pratt, 1982).
W regionie krakow skim budow le o tak w ykształconym szkielecie w ystęp u ją w środkow o- i górnooksfordzkich osa
dach (M atyszkiew icz, 1994; M atyszkiew icz & K rajew ski, 1996) i w latach osiem dziesiątych odsłaniały się w kam ie
niołom ie w M łynce (H offm ann & M atyszkiew icz, 1989). W cyjanobakteryjno-gąbkow ych kopcach m ułow ych tw orzyły sie SCs na skutek erozji w ew nętrznej budow li w ęglanow ej spow odow anej tu rb u le n cją w ody w y w o łan ą przez p odm or
ski spływ m asow y (M atyszkiew icz, 1993). C em entacja po w stałych w ten sposób SCs zachodziła początkow o w m or
skiej strefie freatycznej i była kontynuow ana w różnych sta
diach diagenezy.
Sztyw ny szkielet w budow lach w ęglanow ych je s t do
brze w ykształcony w rafach tubiphytesow ych, które w re
gionie krakow skim rozw ijały się w pobliżu podstaw y falo
w ania, podczas spłycenia zbiornika w późnym oksfordzie.
T ypow a rafa tubiphytesow a z licznym i SICs odsłania się obecnie w nieczynnym kam ieniołom ie w Z abierzow ie. R oz
wój SICs w tak w ykształconych budow lach za chodził na skutek erozji kaw itacyjnej. Proces ten m iał m iejsce u schył
ku ju ry , z hiatusem w zględem w zrostu budow li i m ógł się kontynuow ać w kredzie podczas w ielokrotnych transgresji i regresji. E rozja kaw itacyjna zw iązana z oddziaływ aniem in
tensyw nego ruchu falow ego w strefie m iędzypływ ow ej spo
w odow ała erozję w ew nętrzną silnie zlityfikow anej rafy p rzejaw iającą się rozsadzaniem pierw otnych kaw ern w zros
tow ych. SICs o takiej genezie nie zostały zw ykle w y p eł
nione przez cem ent. N a ściankach SICs je s t rozw inięta n ie
kiedy pow łoka izom etrycznego cem entu granulam ego, w y trąconego praw dopodobnie bezpośrednio po p ow staniu ka
w erny, podczas krótkiego okresu diagenezy w m orskich w a
STROMATACTIS CAVITIES IN UPPER JURASSIC BUILDUPS
55
runkach freatycznych.
W kam ieniołom ie w Z abierzow ie w ystępuje ponadto ciem na odm iana w apienia z SICs w ypełnionym i ciem nym cem entem . C iem na barw a skały i cem entów w ypełniają
cych SICs je s t efektem trzeciorzędow ych procesów hydro-
term alnych (cf. M orozew icz, 1909; D żułyński & Żabiński, 1954; M atyszkiew icz, 1987; R einhold, 1996), które objęły utw ory m ezozoiczne w rejonie K rakow a. N isk o tem p eratu rowe, prow adzące piryt roztw ory spow odow ały także częś
ciow e przem odelow anie istniejących SICs.
