Sedimentation and tectonics of the Upper Proterozoic-Lower Cambrian deposits of the southern Małopolska Massif (SE Poland)

Geological Quarterly, 2000,44 (1): 47-58

Sedimentation and tectonics of the Upper Proterozoic-Lower Cambrian deposits

o f the southern Malopolska Massif (SE Poland)

Wadyshw MORYC and Kazimierz LYDKA

Moryc W. and Lydka K. (2000) - Sedimentation m d tectonics o f the Uppcr Prokromic-Lower Cambrian deposits of the southern Mnlopolska Mnssif (SE Poland). h o l . Quart., 44 (1): 47-58. Wmzawa.

I n the latest Precambrian and Early Cambrian, turbidity currents and cohesive flowstransported pebbles, sand and mud into a deep water in south-east Poland, this sediment probably being sourced from Gondwana. Abundant detritnl aIbite grains suggest volcanism during sedi- mentation. PebbIes in conglomernte interbeds nre polymict and include rock fragments showing greenschist racies regional ~netamorphism in the source area. The Pre~nmbrian surface in the margrnal part o f thc Carpnthians I~es at 20065000 m b.s.l., whereas farther south, mound Kuiminn it reaches 7000 m. Still farthcr south (KrosnolSanok-Baligrbd) geophysicnf evidcnce suggests it lics at about 17-20 km depth.

W/ai&dan~ Motyc, Geological Oflm "Geonafio ", Llrbic: 25, PL-31-503 Krakmv, Poland: Kezimier= tydka, Ittsritwte o j Geocfiemi~ fty, Mineralom and Peti-ogmphy, h i v e r s i p of Wurdmv, fivirki i Wip.ry 93, PL-02-089, Wnrszmra, Poiand (received. Juni 29, 1999; ac- cepted: October 28, 1399).

Key words: Carpathian Foreland, Tam6w-PmmySl are& Precambrian, sedimentation. lithology, basement tectonics, cIastic rocks.

Basement rocks of the Carpathian Foreland were recog- nized in 1954 in the Gorl iczyna 2 boreho te, located around 35 km NE of Rzeszhw. They comprise stsongly folded and weakly metamorphosed claystones and siltstones, lying unconformably beneath Miocene deposits. Initially, Wdowiarz (1954) sug- gested a Silurian or Cambrian, or perhaps older age.

Samsonawicz (I 955,1956) considered them to be Precambrian (Riphean), as did subsequent autl~ors (Karnkowski and Gfowacki, 1961; Gfowacki md K d o w s k i , 1963; Glowacki et a!., 1963; Lydka and Siedlecki, 1963; Obuchowicz, 1963;

Parachoniak, 1963; Stem~~lak and Jawor, 1963; Poiaryski and Tomczyk, 1968; Jawor, 1970; Kicula and Wieser, I970; Heflik and Konior, 197 1, 1974; Jurkiewicq 1973, 1975; Lydk~, 1973;

Konior, 1974, 1978; Kowalczewski, 1979; Hefl ik, 19821, and they were also considered to represent the Upper Sinian (Znosko, 1965; Jaworowski et at., 1967: Jurkiewicz and Kowalczewski, 1968), Vendian (Kowalczewski, 1979, 198 1 a;

Kowalski, 1983) or Precambrian-Cambrian (I~owalczewski, 198 16, 1990, 1994; Wieser, 1967, 1989, in: Wdowian et al.,

1974; Poiaryski el a/., 1981). Acritarchs found by Vidal (in:

Poiaryski et al., I98 I) indicated an Early Cambrian age. Based on this, similar depositc; drilled in the Ryszkowa Wola 3a bare- hole (about 50 ~ Nofrtzeszdw) E have also been considered to be Early Cambrian (Holmio Cambrian).

Early Cambrian acritarchs in Iitl~ologically similar deposits have also been recently found in borehoIes in theNW part ofthe Ryszkowa Wola Horst pziadzio and Jachowicz, 1996). No acricarchs have been noted so far f ~ o m such deposits located to the south (Jaroshw-PrzemySI area), tl~ougl~ it has been sug-

gested that ""Szrb-HoImia and older rocks" may be exposed in this area (Po2aryski et a/., 198 1). Rocks occurring south of the Ryszkowa Wola Rorst were considered by Moryc ( 1 985) to be Precambrian. Assuming the presence of a sedimentary succes-

sion ranging from the uppermost Proterozoic through Lower Cambrian, such Sub-Holn~ia Beds and Precmnbrim rocks may also occur south ofthe Ryszkowa WolaHorst, as suggested also by Precambrian acritarchs recognized in the vicinity of Tarnbw (Zalasowa 1 borehole) (Moryc and Jachowicz, in press).

The age of claystones and siltstones which represent the Precambrian in the southern part ofthe Carpachian Foreland is unknown, isotopic studies to date being inconclr~sive (Burchart, 1971). In the Polish part of the "non-metamorphosed

48 Wladvslaw Morvc and Kazimierz Lvdka

Sedimentation and tectonics of the Uppe :r Proteromic-Lower Cambrian deposits 44

Precambrian" (Heflik and Konior, 197 1, 1974; Heflik, 1982) east and north-east of the Rzeszotary high, isotopic measure- ments were made onmaterial from 4 boreholes (SiedIecki eb a/.,

1966). Recalculations by Burchart (197 1) of material from the Nieczajna 3 borehole suggests an age of 6.00 Ma. This corre- sponds, according to the time scales by Odin (19S2) and Harland et dl. ( 19891, to the Late Proteromic (Vendian). Rocks from the Fusxza (P-2) boreI101e yielded ail age of 523 Ma, cor- responding either to the Ewly Cambrian (Odin, 1982) or to the Middle Cambrian(?) (Hmland et d., 1989). Deposits h m the M ~ d m c h b w 1 borehole yieided an agc, after recalculation by Burchart (op. cit.), of 434 Ma, corresponding to the J3rly Silu- rian. As the weakly rnetamorpl~osed mudroclcs from the Mpkzecli6w 1 borehole are overlain by Ordovician (Arenig) deposits, this date nlrlst be wrong.

[t is clear that the age of the mudrock cleposits in the Carpatllian Foreland basement requires hither investigation.

Regional assessment of these deposits require petrographic and structuraI data as well. Recently, in the vicinity of Tarnbw (Zalasowa), two conglomerate horizons have been fo~md for the first time witl~in these pelitic sediments, and are currently under study.

LITHOLOGY AND DEPOSITIONAL ENVIRONMENTS

The oldest deposits of the consolidated basement of the Matopoiska Massif comprise poorly metamorpI~osed chystones and siltstones with interkds d conglo~nerates and sa~ldstones showing variable levels of diagenetic changcs. The pelites usually sllow ribbon textures, are compact and very poorly calca~ous. They are frequently variegated in red and gmeu, de~lsely jointed wit11 single pyrite inclusions or concen- trations, and thin calcite veins. Thin to thick interbeds of grey siltstone and greywacke sandstone and locally coarse-graincd conglomerates and greywackes - as at Zalasowa new Tarn6w - are intercalated with ^the petitic material. The rocks are usu- ally strongly folded and frequent Iy show abundant s lickensides.

Many pub1 ications describe the uppei~nost parts of these rocks, below which most drilling stopped. Their total thickness is still unknow11. The thickest section yet recognized in the northern part of the Carpatl~iazi Foreland was recorded in the Opatkowice 1 borehole ([Cicu ta and Wieser, 1970). There, the apparent tl~ickness of unpierced deposits exceeds 13 10 in. In the southern p u t of the Carpathian ForeIand, the most co~nptete section is represe~~ted in the Zalasowa 1 borehole (740111- Fig.

2).

The Precambrian basement drilled in different parts of the Carpatl~ian Foreland usually sl~aws steep straral dips up to 90' reflecting folds andlor thrust slices. H;e~~ce, it is difficult to esti- mates their aue thickness. Previous estimate suggested tllick- nesses of > 8500 m (Tokarski, 1962), 1000 m (Kowalczewski, 1981B) or 30004000 m (Znosko, 1983). Thicknesses of analo- gous deposits in Central Dobrogea, Romania, are estimated at about SO00 ITI (Krtiiitl~er and Savu, 1978; Sa~~dulescu, 19X4).

Samples described herein were col Iected From boreholes drilled in the southern part of the Carpntllian Foreland. They are tliought to be roughly coeval wit11 h e P~ecambrian rocks proved in the northern mile (Zalasowa). 80 samples ~vcre coltected

(Fig. 2) fur m ineralog ical-petrographic studies from 10 bore holes drilled between Tarn6w-'Rzesz6w and Przemyll (Figs. 1, 2A, B). They represent peIitic (claystones and siltstones) and come-grained deposits (sandstones, greywackes, conglomer- ates).

San~ples from boreholes Zalasowa 1, Zalasowa 2, Stawiska 1 and WaryS 5 (Fig. 2A) were examined using microscopic and X-ray methods. For sandstones the classification by Dott modi- fied by Pettijohn et aL (1972) was employed. The Zalasowa I borehole recorded a 740 m-thick succession at well depths 36954435 m, overlain by Jurassic deposits (Dagger). Its upper part (36954182 in) is represented by variegated red, green, grey and brown slates and siltstones, which are locally sandy.

Tl~e claystones are compact and are diageuetical ly altered. In places they contain thin intercalations of grcy, compact and fractured sandstones and greywackes with calcite veins.

Locally, dispersed crystals and concentrations of pyrite occur in muddy strata. Compact siltstone layers with in mudstones repre- sent turbidile bases. Stratal dips are low, predominantly 2-5", indicating that the drilled tl~ickness approximates the tnie thick- ness.

Siliiilar claystonesiltstone deposits were recorded in the boreI~oles Stawiska 1 (98 m-thick) and WaryS 5 (220 111). M i k e the Zalasowa I borehole, they show steep dips ranging from 35 to 7.5" (Fig. 2A). Petrographically, there are a nltnber of corn- nlon feahires. The pelites are composed of Fine-gtaincd detrital albite and quart;; autlligenic chlorite passing into brown biotite, and calcite cement. Siltier rocks froin the borehole are Iami- nated and contain albite, C J Uinicrocline ~ ~ and muscovite.

Chlorite in porphyroblasts shows optical features of penninite and occurs as a sttbordinnte component l i e rocks are locally hctured into a tectonic breccia of cm-scale angular and clon- gated fragments. Coarsely crystalline calcite fills Fmchlres and cements tire breccia. hi the core interval of 1972-1 976 m, silty n~udstones show synsedirnentary flow stntch~res.

Table 1 shows the mineral con~position of pelites from bore- holes Waryi 5 and Zalnsowa 1 compared with analogous rocks from the western part ofthe Matopolska aiza.

The Zalasowa 1 borehole penetrated o tder Precambrian rocks. An upper unit ofvariegated poly~nictconglomerai~ with pebbles 1 to 5 cnl in diameter occurs at depths of4 182-4225 m (Fig. 2). Tliese conglomerates are accompanied by mostly thin pelitic interbeds as well as by litl~ic arlcosic greywackes (in par- ticular within a second, tower conglon~erate unit occurring at depths of 4352-441 0 in), S~naller pebbles of r o c k similar to tllose from the conglomeratic intervals have been found in both ntudstones (also fmm depths of44 10-4435 rn) and greywackes.

The two units contain detrital material petrographically variable and of different tmnsfornlation grade

(PI.

1). This deversity is de~nonstmred, among others, by microcline clasts, 2-4 cm in diameter, without traces of aIteration, co-occurring with large, angular albite grains sericitized to a considerable extent. Tl~erc are aIso garnet a few millimetres in diameter with no trace of secondary alteration.

50 Wtadvslaw Morvc and Kazirnierz Lvdka

Fig. 2. Correlation of Precambrian deposits h r n s e l d d botehotw; Tmbw region (A), Rzeszbw and Przemy4I r e ~ i o n 113)

1 - claystones with strong diagenetic alterations; 2- si!tFtones with strong diagenctic nlterations; 3 -pelites with interbeds of cornpact sandstones; 4 -

polymict conglommtes; 5

-

-

- Middle hraqsic; &-- Middle Devonian; 0

-

Sedimentation and tectonics of the Upper Proterozoic-Lower Cambrian deposits 51

Table 1 Mincral composition ofpclitic rocks nnd matrix of Trccsmbrjan dcposits

Larger clasts, several centimeires in diameter, include h g - men@ of magmatic, metamorphic and sedimentary rocks.

Gabbro pebbles, with augik and labradorite, and of ophitic structure show no trace of secondary alteration. There are also pebbles of aIbite metabasites with epiclotized plagioclases as well as large epjdote and chlorite parpIiyroblasts. Granitoid pebbles displaying graphic texture, in which idiomorpllic and bipyramidal q u m grains wit11 identical optic orientations are included in microcline crystals, occur togefllerwith material de- rived from erosion of basic magmatic rocks. Microcline pegma- tite pebbles are spomdic. Volcanic pebbles include spherolitic variolites composcd of albite and chlorite. Microophitic dobh=

ites and fragments of cbloritized rnetabasite with epidote porphyroblasts have also been found. Trachyte and rhyolite pebbles are unmetslrnorpl~osed slnd composed of feldspar and quartz grains embedded in a felsitic groundmass. Some of the trachytes are cut by ptygmatic veins of mici-ocrystalline qumk and albite. Some dacite pebbles contain polysynthetically twinnedalbite gmins to 1 rnm in diameter. Thevolcanic pebbles include rocks which underwent both cataclasis in the source area and rnet;unorphism under greenschist h i e s conditions;

their brittIe fractl~res are filled with coarsely crystalline epidote and quartz

Meramol-phic rocks are represented by fragments of coarsely crystalline albite-microcline orthogneisses locally cut by thin quartz veins; fragments of augen gneisscs with albite porphyroblasts rich in sericite and epidote inclusions are also observed.

Paragneiss pebbles witdl quartzand albite laminae, as well as fragments of quark-albite paragiieisses with chlorites and epidote occasionally reach 25 rnm in diameter. Fragments ofal- bite-epidote-quartz sc11ists belong to rather rarely occurring constituents of coarse-grained sediments. These schists simi- larly as quartzitic phyllitcs and t h i n I y laminated quartz-muscovite schists arc characterized by microfold struc- tures, and occasion~llly contain large muscovite porphyroblasts.

Slates

Sedimentary. rock fragments include abundant arenite peb- bles, as well as intraclasts of lithic greywackes auld hufite peb- bles. The conglomerates frequently show gradational transi- tions into Iithic greywackes or arkosic greywackes. Their ma- trix is compositionally sirnilair to the intehedded arenites and siltstoues (Tab. 1). Dctrital materia[ composi~ig the matrix is very poorly rounded, ~rachlres are filled with coarsely crystal- line calcite which corrodes detrital feldspars.

These conglomerate units are separated (depth 42254352 m) and underlain (depth 44104435 m) by mudscones (Fig.

2A).

The deposits from tlle Zalasowa 1 borehale represent turbidites dominated by thinly laminated claystones and siltstones, and interbedded with litl~ic arkosic greywackes and polymict conglomerates,

Similar deposits have also bee11 drilled below the Upper Ju- rassic carbonates in the barehole Zalasowa 2. These m con- glomerates and greywnckes with, in their upper part, a mudstone interbed dipping at about 40".

In the Stawistca 1 and Zalasowa 1 boreholes these deposits have yielded acritmchs indicating a Precambrian age (Moryc and Jachowicz, in press).

Conglomerates matrix

Many boreholes drilled over this area (Fig. I) have encoun- tered pelites considered to be of Precambrian age. In the bore- holes Zagotzyce 1, Nodwka 1 and Nos6wka 14, around Rzesdw, these PmcamI~ian pelites occur below Ordovician deposits. The Precambrian mudstones and siltstonw are green, grey and red in colour, frequently colour-band& fiachtred and cut by mlmerous thin caIcite veins. These deposits show steep dips of strata, locally (e.g. Nosbwka 14) up to 9O0(Fig. 26).

The rocks have undergone diagenetic and low-grade meta- morphic alterations. The higl~est grade pelitic deposits were drilled near Prze~nyil (Fig. 2B). ChIorite-sericitc slates with

Component

Quark Albite M~cmcIine Chlorite Sericitc

Pyrite+Fc andTi oxides Carbonates

Wary4 5 1840 m

30 48

7 3 12 imce trace

Zalnsowa t 4132 rn

---

33 45

4 2 16 trace trace

Puszcza 2 IlrF4.8-1147.8 m

26 25 trace

17 I7

3 I I

M q g l b d I 256 rn

-

Zalasowa l 4190 m

27 16 L I 16 23 6 trace

52 WEadyslaw Moryc and Kazimierz Lydka

A

NEI ^{s w}

Cis.1 P.130 P Gu.5 Cu.3 Ra.4

Sedimentation and tectonics of the Upper Proteromic-Lower Cambrian deposits 53

porphyroblasts of green pleochroic chlorite locally passing into brownish-green biotite have been found m cores from the Pnanyil252 (PI. 11, Fig. 2) and Przemyil254 boreholes. Such deposits were earlier described by Wieser (1967 and in:

Wdowiarz eC al., 1974) fiom the Cisowa IG 1 borehoIe and Wieser (1989) from the KLlimina 1 borehole and assigned by him to a cluarkalbite-muscovite-chlorite subfacia. Wieser (1 989) recorded bioturbation in these sediments and noted that these rocks show a level of metamorphism similar to that ob- served

in

Pelites from the Kuimina 1 borel~ole contain small chlorite xenoblasts displaying opticaI properties of penninite, in places with biotite intergrowths. LocalIy, the pelites are laminated; the laminae being a few to several tens of millirnetres thick Light laminae are enriched in detrital quartz and albite. The dark ones are enriched in micro-aggregates of iron oxides. Occasionally, within a firegrained quark-albite groundmass, green chlorite grains are arranged according to the oriented structure of rock.

Local, cross-cutting veins are filled w i t l ~ quark and subordinate chlorite.

In summary, the following conclusions can be drawn:

Sedimentation in a pelagic environment took place over this area in t l ~ e Late Precambriail and Early Cambrian. The subordi- nate interbeds of coarse-grained sediments were deposited at that time. These rocks have undergone various diagenetic alterations and low-=de regional metamorphism, reflecting progressive burial and then tectonism.

Early diag~netic processes include ilIitimtion and progres- sive sericitimtion of detrital feldspars and - probably - of volcanic glass, The preponderant detrital albites might suggest volcanism, presumably pyroclastic, during sedimentation. Co- eval and s~tbsequent quartz and chlorite crystalIization partly took place in response to tectonism.

Pebbles in the coarse-grained interbeds suggest lithologically diverse source maswhere the rocks undenvenr regionaI metamorphism of epidotsamphibolite and greenschist facies. Rocks composing pebbles of conglomerates have not been known from the basement of the Carpathian Fordeep (Malopolska Massif) so far. These source areas probably lay within Gondwana.

TECTONICS

The analysedPrem~nbrian deposits were found in boreholes located in the southern part o f the Mafopolska Massif. This structural element can be traced westwards to the

Lubl iniec-Myszkbw-Kmk6w belt (Brochwicz-Lewikki et ai., 1983; Pohyski, 1990; Bula, 1994; Buh andhchowicz, 1996), SE to the Bochnia-Zakliczyn area (Jachowicz and Moryc, 1995; Moryc and Jachowicz, in press) and farther east across Poland to the eastern state border. This massif is separated h m the Upper Silesian Block, located in the south-west, by the Lublinie~Krak6w-Rajbrot fault zone.

The southeastern continuation of the fault zone separating these two massifs has been documented as far b the Rajbrot area (Jachowicz and Moryc, 1995) with a completely different development of Lower Palaeozoic deposits on either side of the zone. There are clues to the probable c o m e of the fault zone yet farther east. The top of Precambrian deposits in the Zakliczyn I and Bmozowa 1 boreholes (Fig. I), still within the Majopolska Massif, is at the same [eve1 as at Zalasowa, at around 3400 m b.s.1. Boreholes at Rajtrot to the south (Fig. 1) (Jachowicz and Moryc, op. cit.) revealed epicontinental Lower Cambrian d&

posits, suggesting a location on theupper Silesian Block These deposits extend to a depth of at least 4560 m and presumably overlie a crystalline basement. About 22 km SE of the Rajbrot boreholes, the Siekierczyna IG 1 borehole (Fig. I) reached a depth of nearly 481 0 m (4425 rn b.s.t.), without reaching the base of the Carpathian flysch deposits (Fig. 3A). This borehole occurs within the SE continuation of tlte Rajbrot region, and should encounter similar geology. Hence, once below the flysch, Miocene, Mesozoic and Palaeozoic deposits (including the Cambrian epicontinental deposits), totalling some 2 Icm in thickness, should aIso occur beneath Sickiercyna. Thus, the top of the assumed crystalline basement may descend from about -5000 m down to 4 5 0 0 rn between Rajbrot and Siekimzyna(Fig. l), being approximately 2000-3000 m lower than the t o p of the Precambrian pelites of the Zakliczyn-B~zozowa Block. Such a considerable difference in the depths to the crystalline basement top between these two blocks (Fig. 3A) suggests separation by a fault zone, which is probably a SE continuation of the Lubliniec-Krakbw-Rajbrot fault zone (Fig. I). It is impossible to trace this zone farther at present. Its trendmay be afSected by basement tectonics e.g. the transversal Wysowz+Jaslo fault (see iytko, 1997 and Ryfko and Tom&, 1998).

The Precambrian basement rocks of the Mdopolska Massif [Fig. l) were strongIy folded (Fig. 3) and perhaps also thrusted.

Consolidated deposits in the Carpathian Foreland are repre- sented - at least in part - by Proterozoic rocks. This is evi- denced by the above-mentioned presence of acritarch microflora. Deposits similar in lithology, also exhibiting identi- cal alterations, occur farther10 the noi-th in the Carpathian Fore- landas far as about the Ryszkowa Wola Horst (e.g. in boreholes:

Fig. 3. Gcologiwl cross-section across the Ca~pathians and their basemelit: S i e k i e r ~ y n a - P i l z ~ ~ d q b i c a region (A), Szufnatowr+Bratkowice region (B), Kutmin3-PrzemySI-Radymna region (C); see Fig. L Tor a location

I-Carpathiern thrust front; 2 -2globim Unit (Mz) or Stcbnik (Mst) thrust front; 3- top surface ofPrecambrian deposits (in Mntopolska Mnssif): 4 - prc- sumed top surf= of crystalline rock (probabIe S E continuation of the Upper Silesian Block): 5 - folded md faulted Precambrian deposits (s~mplified

sketch); 6-major faults; Fl-Carpathien flysch; MP-tnnsgwsiw Miocene overlying flysch (La. "embaymcnts" of Pilano, Drzozown and Rzesz6w); Mz -MioceneoftheZgtobice Unit; Msi-Miocene afthe Sbbnit Unit; M-autochthonous Miocenc; K-Crctaceous; J3+2-Upper andMiddlc1urassic;T- Triassic; CI - Lower Carboniferous; D - Dcvonian; S

-

rocks - Precantbrion; pCm - pelites -Precambrian; USB - Upper Silcsian Block; MB

-

54 Wladvsfaw Morvc and Kazimierz Lydka

R W. 3% Je2owe 3, Eqtownia 1, Rudka 7, Dobra 4, Pislcorowice 2). They contain there Early Cambrian acritarchs of the Hdmia Zone (Pohryski et al., 198 1; Dziadzio and Jacl~owicz, 1996).

The same Iithology is known from many bareholes driIledinthe area between the Carpathians and Ryszkowa Wola Horst, We may thus infer that a continuous succession of deposits, repm senting intermediate members between the uppermost Precam- brian and Hoimia Zone Cambrian, occurs in this area. This opin- ion is in conformity with an idea expressed in the study by Poiaryski et a/. (1 98 1).

This deformation post-dated the Early Cambrian (see above) and pre-dated Upper Cambrian and possible Middle Cambrian rocks differring fmm the pelitic Late Precam- brianlEatIy Cambrian ^successim in lithology and fauna (Tomczyk, 1962, 1963; Poiaryski and Tornczyk, 1968;

Dziadzio and Jachowicz, 1496) and in showing consistent low dips in an absence ofmetamorphism. These cantrasts indirectly indicate the presence of an unconfomity between the two rock successions, folding taking place due to Late Cadomian (Early Caledonian? orogenic movements in the Middle Cambrian (Poiaryski ct a/., 1981; Brochwicz-Lewiriski el al., 1983;

Znosko, 1983; P o w s k i , 1990; IC.owalczewski, 1990, 1994).

In some boreholes (e,g. Zalasowa 1) the discussed deposits show [ow dips of strata and even rest horizonta1Iy. This may be explained by the location of che boreholes in synclinal axes or antic1 inal crests (Fig. 3A).

Faults in the Precambrian basement (Figs. 1, 3) include some showing Miocene movements probably representing r e juvenation of older tectonic lineaments.

The present-day Precambrian-Early Cambrian surface re- flects tectonic and erosional events which took place after the Alpine orogeny. This surface (Figs. 1,3) descends towards the south from a depth of -2000 m in the marginal zone of the Carpathians down to -5000 rn in the Sn~fnarowa area and to about -6500 m in the presumed prolongation of the Silesian Block in the Siekierczyna region. its lowest directly recorded position - at a depth of about -7000 m - is seen in boreholes in the K u h i n a region. Geophysical data (e-g. Pokaryski, 1970;

~ I ~ c z k ~ 1 975; Karnkowski, 1977a,6; Ryko and Tornai, 1945, 1998; Aytko, 1997) indicate that farther south, in the KrosnP-Sanok-BaligrBd region, this surface descends to about

12 km or even 17-20 km (kytko, op. ^cit.).

The top surface of the consolidated Precambrian deposits is additionally disturbed by a series of faults, into a pattern of smaller and larger tectonic blocks. Figure I shows only some of the most important faults (see also Fig. 3). They reveal a series of horsts (Zakliczyn-Brzozowa Block), tectonic grabens lo- cally of "scissors" iype (WaryS-Zalasowa) and monoclines (Dqbica-Kdmina). The monoclinal tectonic block locally

controlled Palaeozoic and Mesozoic sedimentation by move- ment on its northern bounding fault. In the Polish part: of the Carpathian Foredeep &is fault zone extends from the state bor- der with the Ukraine, between boreholes PrzemySl 113 and PmmySl 130 (Figs, I, 3C), westwards between boreholes Drohobyczka 1 and Drahobyczka 2, and between boreholes Tyczyn 1 andKielnamwa 1. West ofRzesz6w it trends between Bratkowice and Czarna Sqdziszowsh (Fig, 3B) and then near Mielec, and north of Busko it continues into the Miech6w Trough. This fault zone was rejuvenatd several times and in- fluenced erosion of suprajacent deposits and the top of the Pre- cambrian surface between the Dqbica-Kutmina n~onoclinal block and the hanging BratkowicePmrnySl Block Lo the north (Figs. 1,3B, C). The course of this fault zone coincides with the erosional extent oFLower Palaeozoic (tacking in the north) and Devonian (Iacking in the southern block) deposits and w it11 Iat- era1 thickness changes in the Mesozoic (Moryc, 1992, 1996).

Later, post-Laramide erosion resulted in a truncation of block margins which largely reduced differences in depth of the sur- face on either side of the fault zone.

CONCLUSIONS

1. Interbeds of sandstone, greywacke and conglomerate oc- cur within the pelites that make up the basei~~cnt of the Malopolska Massif.

2. Sedimentation took place from turbidity currents and su b- marine cohesive flows (conglomerates).

3. The conglomerates are composed of clasts of igneous, metamorphic and sedimentary rocks whicll are so far unknown from the Carpathian Foredeep (Malopolska Massif).

4. These clasts were probably sourced from Gondwana.

5. Tlie basement deposits comprise a Late Proterozoic to Early Cambrian succession.

6. The deposits were folded duri~lg Late Cadornian (Early Caledonian?) orogenic movements of Middle Cambrian age.

7. This basement: to the Carpathian Foreland descoids southwards fro111 about 2000-5000 m b.s-I. down to 7000 111

south of ~ y S 1 ~ K u i m i n a ) and to 17-20 km depth yet farther south.

8. The basement ofthe Matopolska Massif istransected by a series of faults dividing chis area into smaller tectonic blocks.

Acknowledgements. The authors thank the reviewers:

Prof dr hab. Ryszard Dadlez and t l ~ c anonymous reviewer, for their insightfulreviews of this study. Thanks are also dueto Mrs St~lnistawa L&czowsIca for drafting works.

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PLATE I

I . Conglomerate h m the Znlasowa 1 borehole, depth 43604369 rn. Pebble of micropegmatite granite. Feldspars with intergrowths of bipyramidal,

idiomorphic qum; x 100, crossed polars

2 Conglomerate b m the Zalasowa 1 boreholc, depth 43604369 n Metabmite pebble with large cpidotc crystaloblast crossed by uumems quwkveins; x

104 trussed polars

I, Conglomeratefmm the Znlasowa 1 hrehole, depth 43604369 rn. In upperp&-quwmfeldspar matrix witl~gretn chlorite; in lower pnrt-voIcani tcpeb- ble with large, i d i o m r p h i c p i ~ c l ~ crystal p m W d by brown hydrnted iron o x i h ; x 100, cmssed polnrs

2. Peiite with chlorite porphyroblasts. Borckole PrzemySI 252, depth 2539-2543 m; x 100, crossed polars