GEOL. CROAT. 50/1 49 · 56 6 Figs. ZAGREB 1997 

The Helicoidal Fault Systems of Vinodol (Croatia) and Their Genesis 

Ivan BLASKOVIC 

Key words: Helicoidal raull sys tem, Genesis of faults, 
En echelon rolds, f'ault s impact 011 hydrogeology, 
Vinodol , Croatia. 

Abstract 
The basic geological fca!urcs of (he he licoidal fault systems of 

Ihe Vinodol arC:l aTC outlined. [I S genes is is explained by a model 
proposing colli sion:l! stress implied on prev iollsly formed en echelon 
folds. The importance of Ihe fault system fo r struc tura l and palaeo­
geographic reconstruction as we ll as it s impact on hydrogeology are 
di scussed. The model could be applied 10 the External Dinaridcs or to 
olile r similar sys tems. 

1. INTRODUCTION 

By analyzing the geological and especially structu ­
ral relationships of the Vinodol area SE of Rijeka 
(mostly encounte red along the north-eastern rim of the 
va lley) fault sys tems o f variable morphologic and kine­
matic features that change along the ir strike and dip are 
recognized. 

Most or the northeaste rn rim or the V inodol valley 
is composed of Upper Cretaceous rudist limestones, 
transgressive ly and disco rdantl y overlain by Palaeo­
cene- Eocene foraminiferal limestones. The valley itself 
is built up by the Eocene fl ysch sedi ments (GRIMANI 
e t aI., 1973). The rim-va lley trans ition , i. e . the lime­
stone-flysch eonlaet is marked by two or more fault 
traces that by the ir kinematic fun ction along the strike 
merge into reverse or even overthrust st ruc tu res. The 
sam e fault s associated with inclined , overturn ed and 
isoc linal synclines or SW vergence can exp lain th e 
loca l, deep underthrusting of the nyseh sediment s (Fig. 
I ) . 

Within the described structural selling the complete 
ra id structures are only partly preserved: synclines, as 
the footwall of the reverse faults, with fl ysch occupying 
the ir cores have subsided and thus became less exposed 
at the surface, while th e limestone anticlines, as the 
hanging wall , arc uplifted and have bccom e more 
extended. 

The fault traces arc ensily recognisable al ong their 
strike as the line of the carbonate-flysch contact. rn cas-

FaC ilIt y of Mi ning. Geol ogy :wd Pet rolell m Engineering. Uni versity 
of Z lgrcb, Pi cro tlijev a 6, IIR - I 0000 Zagreb, Croatia. 

Kljucne rijeci: sustav helikoida lni h rasjeda , geneza 
rasjeda, esalonirane bore, hidrogeoloska uloga rasje­
da, Vinodol, Hrvatska. 

Saietak 
Na primj cru iz Vinodota dat j e prikaz karak lc ri s tika sus lava 

hcl ikoid alnih rasjeda. Modclom je prezenliranH gC llel.a sus tava, 
vezana uz dje lovanje ho ri l.O ntalnog s trcsa na prV OlllO formirane 
c~a t oniranc bore. tSlakn uto je znaccnjc rasjcdnog s lis lav (l u st ruk ­
turnoj i pa lcogeogra fs koj rekons lTukc iji , kao i u h idrogeo lo~k im 

iSlrazivanjima. Prczentirani modcl moze .~c primjcnili u Vanj skim 
Dinaridima a i sire. 

es when the faults strike farther into the carbonates their 
presence is much less obvious. However, they can a lso 
be identified by the truncation and offset of a transgres­
sive contact between the rudist and foraminiferal lime­
stones or by som e geomorpholog ical indicators , the 
most frequently by linear arrangement of s inkholes in 
the carbonate terrain. 

2. THE HELICOIDAL FAULT SYSTEMS 
OFVINODOL 

Generally , the faults can be de fined as convergent 
splays that joint the main fault (Fig. 2). In the ir margin­
al part splays strike NNW-SSE, more or less separated , 
predominately with oblique strike-slip and possibly nor­
mal movement. 

The peculiarity o r the fault s or the system is the he li ­
coidal shape or each individual rault plane (I'IARDING , 
1983; NAYLOR e t aI. , 1986; SYLVESTER , 1988). 
Along the strike, the azimuth or dip c hanges as the 
angle of dip gradually changes. An examp le of the fault 
systems used to create the model is shown in Fig. 3. 

Close to the conn ec tion point the fault planes 
become more inclined and beeome vertical while along 
strike the dip changes in the opposite direction. Conse­
quently, th e normal sensc of movem ent bccomes 
reverse combined with an oblique slip component. The 
strike gradually becomes "more dinaric" in orientation, 
typically NW-SE. Thus, the main fault plane shows a 
relatively low angl e of dip (up to 25°) with a marked 
reverse character and could poss ibly pass into an over­
thrust strue turc . The vergence o r reverse and thrust 
faults corresponds with thc SW vergence of the fold s. 



,0 

LE GEN D " 

~ 
m 2 

liEnl 3 

Geologia Croalica 50/1 

4 

b( 11 

Fig. 1 Index and genera lized geological map of !he Vinodol area (a fter ~USN J AR CI aI., 1970; simpli f ied and part l y modified). Legend: 1) 
Upper Cretaceous limesto nes and do lomites; 2) Palaeogene fo raminifcral1imesloncs ; 3) Palaeoge ne tl ysch; 4) normal contact, UllconfOl"Jll i­

Iy: 5) strike-s lip faull: 6) reverse fault; 7) upright, incl ined, OVCr!llrtlcd iLlll icl ine; R) upright, inc lined, ove rt urned !iynclinc: 9) monocl ine; [0) 
strike and dip of bedding wilh 25_35° and 50-75° angle of dip: II) overturned bed. 

SI. I SmjcSlajna i shcmatska gco[oska karla Vinodo la. Shemalsld prikaz gco!oskih odnosa 11 <1 d ijclll sjcvcroistocnog obocla Vinodola s posebno 
islaknulim uzd uzni rn rasjcdima (prCIll41 SUSNJAR et aI. , 1970, pojcd nos lav ljcno i dijclom dopu njcno). Legcnda: I) gornjokredni vapnenci i 
dolomili; 2) palcogenski fo mm inifcrski vapncnci; 3) palcogcnski n isni sed imcnt i: 4) normal na granica, Icklonsko-crozijska d iskonlancija; 5) 
horizon!al ni msjcd: 6) rcvcrzni rasjed: 7) usprav na, kosa, prcbacena an!ikli nala; 8) tlspravn:l, kosa, prebaccna sink linala: 9) koljcnieas!(t 
bora, tlcksura: 10) polozaj srojcva; vcliCi n<l nagiba 25-35°, 50_75°; 11) prc baccni sloj. 

LEGEND 

Ini!!!!!i:H Flysch 

D limestones 

Conditional 
orientation 

Not in scale 

The genes is o f the described faulL system li es in 
quite complex tec tonics and g reat differences in the 
gcomechanical p roperties of the carbonate and clast ic 
sedimentary bodies. It could be explained by a succes­
sion of geodynami c processes and presented by a con­
ceptual model as follows. 

The geodynami c evolut ion begins with the Larami ­
an deform alion phase that res ulted in the formation of 
en echelon folds (Fig. 4) and the consequen t morphol o­
gy. Furthermore, during thc pre-Pyrenean and Pyrenean 
deformation phases the anticlinorian parts o f the struc­
tures consisted of predominately of carbonate rocks and 
the synclinorian parts of fl ysch clasti cs. The thi ckness 
of clastics is direc tly related to the synform , as one part 

Fig. 2 Schelll ilt ic di agram showing Iwo systems of convergenl he li· 
coidal faul ts in the NE rim arC'I o f Vinodol. 

$1. 2 Shem<llski prikal dva sustava konvergirajllCi h hcli koidalni h ras­
jcda 1I istra:Zi vanorn d ijclu sjeveroistocnog oboda Vinodola. 



BI:l.~kovic: The t !clieoidnl Fnu h Systems of YinodoJ (Croatia) and Their Genesis 

~ 
N 
~ 

Condit ional 
orlentlltlOn 
Not scale-

LEGEND 

51 

Fig. 3 Schematic plan view of convergent he!i coidul fault planes with 
the great est principal stress orientation. A, B, C as reference 
observation points for the second deformation phase (sec Fig. 6). 

S1. 3 Shematski ortogonalni prikaz konvergirajllCih helikoidalnih ras ­
jednih ploha s naznacenOITl orijentacijom glavne osi stresa. A, B, 
C, referentne tocke razmat ranja II drugoj fazi strukturnih promje­
na (sJ. 6). 

of megastructure characterized by greater mobility and 
subsidence rale. 

Even with more intens ive folding during the pro­
gressive deformation process the mobility of the syn­
forms and particularly the flysch thickness arc of cru­
cial importance, i.e. the amplitudes of folds are directly 
related to the thickness of the less competent, clasti c 
sediments. 

Under the same stress field regime tha t regionally 
resulted in the continen tal subduction of the Adriatic 
under the Dinaric (HERAK, 1980; BLASKOYIC & 
ALlINOYIC, 1981; BLASKOYIC, 1991 ), the structur­
al changes are partially govemed by the clockwise rota­
tion of each individual fold around the "b" axis (Fig. 
Sa): the anticlines, as the more rigid , competent parts 

Conditional 
orienlation 

Not in scale 

a 
a 1 D 2 Il:!m[n~ 3 ~/:;. 4 ~ e-W 5 _._-- 6 _w. 7 1--1' 8 

Fig. 4 The genesis or the helicoidal fault syslem: a) pres umed originallcclonic fabric of wngelliial folded structures; b) collisio nal stress impl ied 
011 ell echelon folds: c) imbricate structure and convergent helicoidal fault splays . Legend: Compelcnt rocks: I) Upper Cretaceous rudiS I 
Ii llles ione; 2) Eocene foraminifera limes tones. incompetent rocks : 3) Eocene flysch. 4) Principal Slress orientation: 5) upright, inclined and 
oven urncd anticlin e: 6) predetermined faull zones; 7) nonnal and reverse fault: 8) Irace of schematic geological profile. 

SI. 4 Pos tanak sllstaV<l hclikoidalnih rasjeda: a) prelposlav lj eni polazni tektollski sklop langencijalnih boranih st ru ktura; b) esa lonirane bore 
izlozene horil',onlalnom strew: c) Ijuskave siruklllre i konvergirajuci snap helikoidalnih rasjeda. Legellda: Kornpetentnc stijene: I) gornjo­
kredni rudiSllli vapnenci i 2) eoccnski foraminifcrski vap nenc i; nekompelentne stije ne: 3) cocenski flis. 4) Orij cntacija glavnog Slrcs a: 
5) uspravnit, kosa i prebaccna ;lIl1ikl inal a; 6) prcdisponirane zone rasjeda: 7) rasjcd normalnog, revcrznog karaklcra; 8) Irasa shcmatskog 
geo lo.~kog profila . 



Geologia Croatica 50/1 

I. AI, "1("-__ _ cI.~~ 
-r---

8W NE 

IlItrt~'"I ... 1 
II: I 

1 
II: 

~4.. __ _ 

-r---

Fig. 5 Prc!'cntation of !'tnlctural changes on schcmatic geo logical profiles, an <lddi\ ion to Fig. 4. a) En ec hclon fo lds from Fig. 4b. Due to bend ­
ing o f presumed mega .~ t fUCHIre (Fig. 4a) thc axial planes and fold limbs changc Iheir strike and dip: b) the result of the fi rs t deformation 
phase: imbricate structures o f variable de formation intensity with faults merging into the main fault zonc. Symbol ex planation as for Fig. 4. 

S1. 5 Praccnje Slruklurn ih promjena na shematskim geoloskirn profilima, dopun<l sl. 4 . a) Borane strukturc csa lon iranog rasporcda sa sl. 4b. 
OponasajllCl zakrivljenost pretposlavljcnc mcgastrllktlll'e (sl. 4a) bore mijcnjaju c lemente polozaja o!'nih ravnina i krila. b) Rezultat djclo­
vanja gcncralnog !'tresa i Olpora istomc u prvoj fazi slrllktllrnih prornjcna: Iju skave struklure nizli cilOg ilHenzilcla porcmecaja liZ slapanjc 
rasjcda II jed inslvenu rasjednu ZOIiU . Zn:lccnjc simbola vidi 1I pOlpiSli 51. 4. 

(regarding lheir structural form and predominance of 
carbonate rocks ncar the surface) are uplifted whi le the 
synclines, as the more mobile parts ( regarding the ir 
negative fo rm and predominance o f clastics) tend to 
subside. Thi s results in brittle failure within th e folds 
inflection zones and thus in the [ormation of fault s (Fig. 
5a). 

Within parts of en echelon fold s dominated by anti­
cl ine structures characteri zed by the more rigid carbon­
ate rocks, the developed fa ults are partially of normal 
lype and with vertical fault planes. Therefore the reduc­
tion of width of the original en echelon structurc due to 
faulting is minimal (Figs. 4e, 5b, prollie e I-I'). In con­
tras t, within the parts o f en echelon fo lds dominated by 
sync linal structures characterized by predominance of 
the thi ck, less competent clastics, the developed j~\Lllt s 

are o f a reverse type with fault planes that dip in the 
direction of the main coll is ional stress, i.e. wi th struc­
tures showing opposite vergencc (Figs. 4b, Sa, profile b 
II-II'). 

As the anticlines pl un ge and turn into a uniform 
gross synclinal st ructure the reverse fault s merge into a 
s ing le ma in fau lt that could possibly become an over­
thrust structure (Figs. 4c, 5b, profi le c II-II '). The reduc­
tion of width of the origi nal en eche lon structure is 
maximal: the synclinal structures , the thickness of the 
clastic compl ex, as well as the deepe r pos ition o r car­
bonate rocks reduce the resistance to the main coll is io­
nal stress. 

The transition between the described end cases is 
gradati onal regarding the character and shape o f the 
developed structures as we ll as to the intens ity of the 
deformation. 

The first phase of the geodynamic process thus 
results in the formation of a system or convergent heli ­
coidal faults (Fig. 3), and in modified en echelon imbri­
cate structures, that mark the structural fabric in general 
(Fig. 4c). The strike of the imbricate structures changed 
in respect to the st rike of the axial planes of the orig inal 
en echelon folds. In the process of the rOllllation of the 
imbricate structures and the convergent splay of heli­
coidal fault s, respecti vely, the reeluction of the origi nal 
width resulted in bcnd ing of the strike lincs. Thi s 
change in strike is only local duc to specific conditions 
and not due to change in the regional o rientation of the 
main collisional stress direction, as is shown on the pre­
sented mode l. 

The nex t deformation phase or the geodynamic 
process is marked by a relative change in the stress 
field orientation (ANDERSON & JACKSON, 1987; 
RITSEMA, 1974) with a generally N-S to NNW-SSE 
orientation of the greates t principal stress ax is, i.c. diag­
onally to the dinaric strikc of the structures. Alt hough 
thi s change in orient ation was gradual we shall discuss 
here and schematically present only the youngest de for­
mational phase. 

The prev iously formed faults in the marginal part of 
the convergent splay of the he lico idal system , stri ke 



B1as~o\lic: The I lclicokial Ewh Systems of Vinodol (Cro;lti., ) ,Hid Their Genesi~ 53 

LEGEND : ~ 
D N 

~ 
llillilll 2 Conditionol 

Of 11m tat IOn 

¢= 
No l scale 

3 , 4 

B 5 

- 6 

-- 7 

--0 8 

Fig. 6 The strucillral deve lopment in the sccond phase of the geodynamic process due to the regional change of stress fi eld orientation: the 
development of tile transtcnsion zone: the impact or struCtu res to hydrogeology. Legend: t) karstified carbonate rocks - permeable rocks: 
2) fl ysc h sedimcnts - impermeabte rocks: 3) stress fi eld orientation: 4) fau lt s willl Ihe se nse or di splacemen t - predetermined groundwate r 
flow conduits: 5) transtension zones, i.e. zones of ex lension fractures: 6) the transpression zones - relative barri cr to groundwtller now: 
7) supposed groundwater flow direction: 8) potential spring occurrence. 

SI. 6 Ova sluC:ija slruktu rnih promjena druge faze gcodi namskog procesa u uvjctima promjene smjcra gcncralnog stres;!: fonniranje ekstenzi­
jski h zona: naznaka hidrogcoloskc uloge formiran ih st ruktur:.!. Legenda: I) okrSenc vapnenacke st ijenc - propusnc slijcne: 2) ni sni sedimenti 
- ncpropusne stijcnc: 3) orijentacija slresa: 4) rasjedi s oznakorn krctanja hila - priv ilcgirani pravci krctanja podzcmne vode; 5) zone ekslen-
7ij ... kih karaktcrislik a - zjapcce pukotine: 6) zone komprcsijskog karaktcm - rclaliv ilc barijcre krclanja podzemnc vode: 7) prelpostavljeni 
~tlljcr kretanja podzcmnc vodc: 8) moguCi izvori. 

almosi para ll c l with the greates t pr inc ipa l s tress ax is 
(Figs. :) and 6). T hus, the dextra l st ri ke-s li p and 

oblique-slip di splacement s predominate. The magnitude 
of di splaceme nt is direc tly re la ted to the mass or eOI11-
pe tent, ri g id blocks bounded by fau lls of the sys tem as 
well as 10 the volume of the claslic nyseh complex of 
the tec tonically reduced syncli na l struclure. 

The dexlra l s lrike-s li p displacemellls along subpar­

a ll e l fau ll planes of Ihe convergent splay of the hel i­
coidal syslcm lead 10 the deve]opmclll of a transtension 

zone (RAMSAY & H UB ER, 198 7) with ex te ns ion 
fraclures (Fig. 6). T his is pa rt icularly wel l developed 

with in Ihc competent carbonate rocks even in cases 
whe n Ihese arc overla in by clas t ic fly sch sedi ments. 
These fract ures call rarely be seen o n the surface as 
they become partia lly fi lled and hidden, due to grav ila­
lional collapse and roek raIl. 

The imporL ance o f the described in terp re ta tion o r 
the he li co idal fau lt sys tem is man ifo ld . It coul d be 
applied to resolv ing structural prob lems and genesis o j' 

termines charac te ri zed by tangentia l tec to ni cs, e .g. in 

the ra Id- thrust be lt s. Moreover, one can c learly rea lise 

the poss ibility for pal aeogeog raphi c an d pa linspas ti c 
reconst ruction as well as for studyi ng structura l changes 
duri ng the geodynamic process by app ly ing the reverse 
method of study to the onc described above. 

T he pa rti cu lar importance and in flu e nce of he li­
coidal rault sys tems on hyd rogeology shou ld be a lso 
emphas ized (Fig. 6). T he faull con tac t be tween the car­

bonate and clastic complex is also the conlac i be l ween 
permcable and impermeabl e rock unit s; the imperme­
ab le cl astics Ihat arc mostl y fau lt bounded flysc h 

wedges, represent hanging barriers thai ex te nd re lati ve­
ly deeply undergroun d, th us clearly de term inin g Ihe 
ve rt ica l and hori zonta l groun dwa ter now. However, 

even the fault s of the helicoida l sys tem thai s tri ke in to 
the carbonat e rock comple x p lay an importa nl ro le in 
the gro undwate r n ow reg im e: the prede term incd 

groundwate r fl ow d irec ti ons co uld be expec ted along 
these fa ult zones. Furthe rmo rc, wit hin Ihe transtension 



54 

zone wi th abundan t extension fractures developed in 
the carbonate rocks massive development of cave sys­
tems could be expected as well as the occurrence of 
springs of the greatest discharge. 

3. CONCLUSION 

The helicoidal fau lt systems of Vi nodol represent 
convergent splay fau lts that j oint into the main reverse 
fault. They cou ld be particu larly important in regions 
characterized by compressive tangential tectonics, i.e. 
within the [old- th rust belts. They have the ir orig in in 
deformation induced by coll isional stress imposed on 
previously formed en echelon folds composed mostly 
of competent and incompetent rocks. The most recent 
structural fabric was produced by a relative change in 
the stress field orientation that resulted in the predomi­
nance of strike-s lip displacements along the faults of 
the system. 

During the next deformation phase the formation of 
extension fractures in competent rocks could be expect­
ed due to transtension developed at fault bcnds. 

Regarding their particularly marked impact on karst 
hydrogeology the faults of the helicoidal sys tem 
whether deve loped in permeable strata, or along their 
contact with impermeable rocks, could be predeter­
mincd to serve as the main groundwater flow conduits. 
Within the transtension zones developed at their bends 
they could result in the occurrence of karst springs of 
the highest discharge values. 

The described model could be app lied in reg ions of 
simi lar geology, e.g. throughout the External Dinarides, 
or fur ther afield. 

Geologia Croatica 50/1 

4. REFERENCES 

ANDERSON. H. & JACKSON, J. (1987): Active tec­
ton ics of the Adriatic rcgion.- Geophy. J. R. Astr. 
Soc., 91, 937-983. 

BLASKOVIC, I. (1991): Raspored uzduznih. reversn ih 
i norma lnih rasjeda i konstrukcija oblika i dubina 
ploha podv lai'enja.- Geol. vjcsnik. 44, 247-256. 

BLASKOVIC, I. & ALJlNOVIC, B. (198 1): M ikrotek­
tonski elementi kao os nova za mode l tektonske 
grade sircg podrucja Kvarnera.- Zbornik radova 
simpozija "Kompleksna naftnogeoloska problema­
tika podmOija i priobalni h dijelova Jadranskog 
mora", Split, 1,87-100, Zagreb. 

GRIMANI, I., SUSNJAR, M., BUKOVAC, J., MI­
LAN. A .. NIKLER. L., CRNOLATAC, I., SIKIC, 
D. & BLASKOVIC. I. (1973): Osnovna geoloska 
karta SFRJ 1: 100 000. Tumai' za lis t Crikvenica L 
33-102.- Inst. geol. istraz. Zagreb (1963), Savezni 
geol. zavod Beograd, 47 p. 

HARDING. T.P. (1983): Divergent wrench fault and 
negative flower struct ure. Andaman Sca.- In: BAL­
LY, A.W. (ed.): Seismic expression of structural 
styles, Volume 3. Am. Assoc. of Petr. Geol. Studies 
in Geology, ser. 15,4.2.1. -4.2.8. 

HERAK. M. (1980): Sustav navlaka izmedu Vrbovskog 
i Dclnica u Gorskom Kotaru (Hrvatska). - Acta Geo­
logica, 10/2, 35-51. Zagreb. 

NA YLOR, M.A .• MANDL, G. & SIJPESTEIJN, C.H.K. 
(1986): Fault geometries in basement-induced 
wrench faulting under different initial stress states.­
Jour. Struet. Geol.. 8. 737-752. 

RAMSAY, J .G. & I-lUBER, M. 1. (1987): The tech­
niques of modern structural geology, Vol. 2.- Acad­
em. Press. London, 309-700. 

RITSEMA, A.R. (1974): The earthquake mechanism of 
the Balkan Region. - UNDP Projekt R. 3 EM, 
70/172. UNESCO, Skopje. 

SYLVESTER, A.G. (1988): Strike-sl ip faults.- Geol. 
Soc. Am. Bull., 100, 1666-1703. 

SUSNJAR. M., BUKOVAC, J., NIKLER, L.. CRNO­
LATAC, I., MILAN, A., SIKIC, D., GRIMANI, I., 
VULlC, Z. & BLASKOVIC, I. (1970): Os novna 
geoloska karta SFRJ, 1: 100.000, list Crikveniea 
L33 -101.- Inst. geol. istraz .. Zagreb (1958-1967), 
Savez. geoL zavod Beograd. 



I3h;;kovic: 111C llelicoidal Fault Systems of Vinodol (Croatia) and Their Genesis :i5 

Sustavi helikoidalnih rasjeda u Vinodolu i njihov postanak 

Ivan IlLASKOVIC 

1. UVOD 

iSlraz ivanjima geoloskih i posebno slruklurnih odnosa 
u po cirllcj ll Vinodola, locnijc sjeveroi slocnog oboda 
doline, lllvrdeni Sll sll slavi rasjeda razlicilih karaklcri slika, 
koje sc mijcnjaju po prllzanjll i nagibu rasjednih ploila. 

Sjcvcroi slocni obod Vinodola izgraden je pre tez ito iz 
go rnjokrcdnih rlld islnih i paJeocensko-eocenskih foramini~ 

ferskih vapnc naca. Oni su mcdllsobno II Iransgresiv nom , 
disko rdanlllom kon laklll . Samu dolinll izgraduju eocenski 
f1i sni scdi mcnli (ORTM AN I eL aI. , 1973). KOlllakl izmedu 
vapnenac<I oboda i f1i sa dol ine je ra5jedan i nijejedinstven; 
sastoji se iz 2 iii vise rasjeda koji se u pruzanjll i funkciji 
slapaju u reverzne odnosno navlac nc slruk lurc. Uz kosc, 
prcbaccnc i izoklinalnc bore, tocn ije s inklinalne dijelove 
lih bora , jugozapadne vergencije, upravo navedcnim rasjc­
dillla moze se objasnili mjestimi cc d uboko uvlace njc 
rJi snih scd imcnala (s l. 1). 

U takovim slruklurnim odnosima bore su fraglllenlarno 
sac uvane; s inklinalni dijclovi izgradcni iz fli snih nas laga 
S Li rasjcdi ma rcdllc irani , odnosno nalaze sc II poclinskim 
krilima revcrznih rasjcda, dok VCC ll povrsinll imaju anti ­
klinalni dijclovi bora, izgradeni iz rig idn ij ih vapnenack ih 
st ijena. Oni s u u krovinskilll krilima istih rasjeel a. 

Rasjcdi SLt vrl0 lIoc lj ivi Lt dijc lu prolczanja gdje Ivo rc 
kon tak t iZl11cdu karbonatn ih slijena oboda i Oisnih naslaga; 
pruz;'ljuCi sc u nastavku i unutar vapncnackih slijena oboda 
Vinodola vrlo sc lesko zapazaju, osim prek idom i 
Ira nslacijom Iransgrcsivne granice izmeelu rud isln ih i 
roraminircrsk ih vapncnaca iIi indirckln im geomorfo loskim 
po kaz<llc ljim:l , najcesce nizom ponik vi II pra vocrt no m 
rasporcelll. 

2. SUSTA VI HELIKOIDALNIH RAS.JEDA 
U VINODOLU 

Op is<l ni sustavi se IllOgu gcncralno dcfinirali kao kon­
ve rgenlni snop rasjcda koji se spajajll II rasjccl s jeclin­
slvcnom rasjcdnom ploholll (s l. 2). U perifc rn oJl1 d ijel u 
snopa, mcc! usobno vise iIi manje uda ljc ni, llg lavnolll s u 
pruzanja NNW-SSE, hori w ntalnog oclnosno d ijagonalnog, 
pa i Illogllce no rmalnog krelanja krila. 

Posebno~t rasjcda koj i c ine suSlav jc hcl ikoiclalni obl ik 
,.asjcdnih ploha (HARDI NG, 1983; NAYLOR Cl aI. , 1986; 
SY LVEST ER. 1988) po pruz<lnju; uz poslllpnll promjcnu 
ve lici nc nagiba mijenja sc i smje r nag iba. Modc lski 
obradlljllc i jedan od slls lava 10 je i prczcnlirallo na sl. 3. 

Pri blizavajuci .'iC mjest ll s pajanja, rasjcdne plohc sc 
llslnnljllju sve do oko milog polozaja, a icluci clalj e po 
pruzanju z<luz imajll s liprotan smjcr nagiba od polaznog; 
karakt c l' ra sjcdanja postajc rcvcrza n LI Z dijagonalno i 
clominiln tllo vcrlikalno krctanje kri la . Mijenja sc pruzanjc 
rasjccla It .wc izrazcniji dinaridski pravac (NW-SE). 

Spojeni sno p rasjcda u rasjed s jcdinstvcnom rasj c­
dnom ploholl1 rc lativno blazcg iii blagog nag iba (najvi sc 

do 25 °), oznacen je izrazitim rcverznim karakterol1l i s 
l1log 11 c im prijelazom Ll struklllrLl navlakc. Vcrgencija 
reverznih iIi navlacnih slrllktura ide ntic na j e vc rgcIlciji 
bora Ij. prcma jllgozapadu. 

Postanak takovih rasjednih suSlava jc rczultat s lozenog 
te ktonizma i geomehanickih karaklcri slika karbonatnih i 
klaslicnih sedimentnih kOlllpJcksa koji izg radlljll Ie stru ­
kture. Moze se objasniti odrcdcnim sljcdom gcod inamskih 
procesa, kako je 10 modclolll i lIcinjcno u nastav ku . 

Oeod inamski razvoj zapocinjc laramijskim pokrelima. 
Pod uljecajcm horizonta lnog stresa i o lpo ra iS lom , formi­
raju sc borc csaloniranog rasporeda (sl. 4) i konsekventne 
l11orfo logije. 

U nastavk u procesa, u predpirencjskoj i pirc nejs koj 
faz i geodinamskih promjcna, prctpostav ljajll sc an li klinori­
jski dij c lovi struktura s ciominacijol1l karbonalnih stijena te 
s inklinorij ski dijelovi II kojima S ll iSla lozcnc fli sne 
klast icne stijene vecih debljina. I ovclje se deb ljina klast ita 
veic uz sinformu , kao clio megaslrukt llre vecc l1lobilnosli 
tij ckom scdimentacije, LI smis lu subs idell c ije. 

No i LI geodinamskom p roceS Il cJaljcg, inlcnzivnijeg 
boranja kojc slj cdi, mobilnost sredine, a posebno deb ljina 
fl isa je od pre.suclne vaznosti ; amplitude bora su u izravnoj 
ovisnost i i 0 dcbljini plaslicnijih scdimcllata. 

U n<lstavkll dje lovanja horizonlalnog siresa, a koji II 

regionalnim okvirima dovodi do podvlaccnja - s llbdukcije 
konlinclltalnc korc Adrijatika pod Di narik (HER AK, 1980; 
BLASKOVIC & ALJI NOV IC, 1981; BLASKOV IC, 
199 1) strukturne prollljcnc s u odraz d ijc lo m i rOlac ije 
svakc od bora oke b - osi (s l. Sa); antik linalc kao rig icl niji, 
ko rnpelc ntniji dij c lovi, s o bz irom na strukl llrni oblik i 
dOl1l inaciju vapnenackih slijcna, blize povrsin i se izd iz LI , a 
sinklinale kao l1lobilniji dije lovi bora, s o bz irom na ncga­
livnll fOrl1l11 Ie clominac iju klastila, tcze sp us lanju. To 
rczultira pLicanjem II zoni prcgiba bora tj. infl cksijc i ras ­
jcdanjclll (5 1. Sa). 

U dijclovima csaloniranih bora, u koji ma c10llliniraju 
antiklinalnc st ru klure, s islaknlllijo lll povrsinom i kine­
lllatskom ulogom rigidne kompetcnlnc vapncnacke slijene, 
rasjcdi SLl dijelom i normalnog karaklc ra i s vc rtikalnim 
rasjed nilll p lohama. Redukcija s iri nc pril1larnog cSa loni ­
ranog stru klurnog skT opa ll sIijed rasjedanja jc minimalna; 
horizontal nom st.resu suprotstavljen jc odgovarajuc i olpo r, 
kao rezu ltal antiformnih struk tura i ri gidnijih kompleksa 
sl ijcn" (s l. 4c I, 5b, profil c 1. 1'). 

Nasuprot tome, u d ijelovima csalo niran ih bora 1I koji­
ma dominirajll sinklinalne slrllklurc s vecom povrsinom i 
dcblj inolll fli snih naslaga, podatnijih de formacijam<l, rasje­
d i cc bili reve rznog karaktera, s rasjcdnim plohama nag nll ­
l im Ll smje ru g lavne osi slrcsa, od nosno sa st ruklllrama 
sllprolne vcrgcnc ije (sl. 4b I, Sa, profil b II - II '). 

Buduci da ccla anliklina la tonu i prclaze u jCd instvcllll 
s inklinalnu struklllru, doJazi do stapanja rcvcrzilih rasjccla 
II j ed instven i rasjed s mog ll cnosc ll njegovog prijc laza u 
slrukturll navlake (s l. 4c I; s l. 5b, prori l c II - II '). Rcdukc ija 
s irin c primarnog ciialoniranog sk lopa jc maksimalna; 



56 

sinklinalne slruklurc i debljina klaslicnog kompleksa slije­
na, Ie dublja pozicija vapncnack ih st ijcna u podini, sllla­
njuju Olpor glavnolll kolizijskolll slresu. 

Prijelaz iZlllcdu opisana elva krajnja sl ucajaje postupan 
s obz irom na karakter i obl ik struklura, kao i intenzitet 
poremecaja. 

Rczultat opisane prve faze geodinamskih proccsa prcd­
slavlja /"ormiranje kOllvergirajuceg snopa - sustava heli­
koidalnih rasjeda (sl. 3), odnosno u opcelll struklurnolll 
sklopu modirieiranih, takodcr ciialoniranih ljuskavih stru­
ktura (sl. 4e). Pruzanje ljuskavih strukLura promijenjeno je 
u odnosu na pruzanje osnih ploha ishodisnih eSaloniranih 
bora; u proccsu form iranja Ijuskavih struktura, odnosno 
konvergclltnog snopa hclikoidalnih rasjcda doslo jc do 
povijanja pruzanja kao rezultat redukcije s irine . Takova 
promjena prllzanja je, kako se iz prezenliranog modcla 
vidi, tck lokalna pojava vezana LI Z speeiricne llvjele, a nc 
posljediea promjene smjera glavnc osi slresa. 

Iduca faza geod in amskih proccsa oznacena je rela­
tivnom promjenolll sllljera slresa (ANDERSON & JACK­
SON, 1987; RITSEMA, 1974); sIres jc usmjcrcn prema 
sjcveru odnosno sjeversjcvcrozapadu, dijagonalno na 
dinaridsko prllzanjc struktura. Do te promjcne dolazi pos­
tupno, medutim, ovdje se shematsk im prikazolll komentira 
najmlaela faza. 

Tako orijenlirani stres gotovo je paralelan pruzanju 
rasj eda na per ifernom dijelu konvergentnog snopa koji 
Ivore helikoida lni sustav (s1. 3 i 6). Pod njegovim lltjeca­
jem oelvija se dijagonalno pa i horizonlalno krctanje krila 
rasjcda; uglavnolll jc to desno kretanjc. Velicina hoda jc 
ovisna 0 !nasi kompclenlnih, rigidnijih rragmenala izmedu 
rasjeda sustava i iSlovremeno 0 povrsini i debljini 
klaslicnog rliSflOg kompleksa tektonski reducirane sink li ­
nalnc slruklUre. 

U svakom sl llcaju, II zoni spajanja snopa helikoidalnih 
rasjeda suslava, gdje se lim rasjedima zalvaraju rigidniji 
rragmcnli, i gdje jc oeita promjcna pruzanja vanjskih rasjc­
da sllslava, kao i sve to ved nagib jedinstvenc rasjedne 
plohc, ll s lij ed dcsnog krclanja krila dolaz i do rorm iranja 
c kstenzijskc zone (RAMS A Y & I-lUBER, 1987), i' ijilll 
progrcsivnim razvojem naslaje suslav zjapecih pukolina 
(s1. 6), mecl usobno uglavnom povezanih. To je poscbno 
izrazeno u kompaktnim vapnenaekim stijcnama kojc su i 1I 

podini klasticnih nisnih naslaga, ukoliko su ove prisutnc u 
strukturi i na povrsini. 

Takve ce pukotine na povrsini bili rijetko vidlj ive; usli­
jed g ravilacijskog povijanja iIi obrusavanja dijelom Sll 
za tvorcnc i skrivcne. 

Znacenje opisani h helikoidalnih rasjedni h sustava je 
visestruko. Moze se primijeniti u rijcsavanjll slruklll rnog 
sklopa i njegovc genczc u podrucjima ka rak lcrizi ranim 
tangencijalnim boranim i rasjednim strukturama isto­
znacne vcrgencije. 

Geologia Croa!ica 50/1 

Nadalje, ukoliko sc primjeni obrnuti postupak od trcli ­
ranog u ovom radu, jasno je istaknuta mogucnost paleo­
geografske i palinspaslicke rckonstrukcije primarnih 
odnosa, kao i pracenje promjcna tijekom geodinamskog 
procesa. 

Valja poscbno istaknuti i znacenjc hclikoidalnih ras­
jednih sustava u hidrogeologiji. Na s li c i 6 dijclom su 
naznaccnc i hidrogeoloske lllogc slijena i strukturni h e le­
mcnata. Slijedi i kratki komentar takovog prikaza. 

Rasjeclni kontakt vapnenaekog i klasl ienog komp leksa 
je i kontakt propusnih i nepropusnih naslaga; klasticne 
nasI age u ovakovim odnosima prcdslavljaju visecli bari­
jeru relativno dubokog elosega. Obicno su to tektonski 
llkljdteni rlisni sed imenti uz rasjede sllslava. S takovom 
ulogom jasno dijelom odrcduju i krelanje podzemne vode 
Ll horizontalnom i vertikalnom smislu. No, i sami heli­
koielalni rasjedi sustava, unutar okrsenog vapnenackog 
kompleksa, igrajll znacajnll hidrogeolosku ulogu; cluz ras­
jeda - rasjednih zona mogu se pretpostaviti privilegirani 
slllje rovi toka podzcmnc vode; okom ito na njih pret­
postavlja se zna(no slllanjena mogllcnost protjecanja. U 
zonama formiranih zjapccih pukot ina unutar rasjednog 
suslava, duz kojih je logieno ocekivali i spcleoloske objc­
kle, s velikom vjerojalnoscll mogu se J"ormirati izvori i 
znacajnijeg kapacilela. 

3. ZAKLJUCAK 

Rczultati rada mogu se svcsti u ncko li ko zakljllcaka. 
Sustavi helikoidalnih rasjeda predstav ljaju konve rge­

ntni snop rasjeda koji se spajaj u II jedinstveni rasjed 
reverznog karaklera . Znacajni su za te rCIlC oznacene 
kompresijskim tangencijalnim sl ruktu rama. Nastaju kao 
rezu llal deformacija esaloni ranog rasporcda bora, u pravilll 
izgradenih iz kompetciltnih i nekompetenlnih stijena, 
izlozenog hor izonta lnom strcsll . Recentni slruklurni sklop 
nastaje relativnom promjenom smjcra horizonlalnog stre­
sa, slo dovodi do horizontalnog kretanja LIZ pojedinc ras ­
jedc sustava. 

U toj drugoj fazi geodinam skog proeesa mogllce je 
formiranj c ekstenzijsk ih - zjapecih pukotina II kompaktnim 
sl ijcnama u rasjednim zonama. 

S obzirom na posebno izrazenu hid rogeoloskll ulogu u 
krskim tercnima, rasjcdi helikoidalnog sustava, unu tar pro­
pllsn ih stijena i 1I dodiru s nepropLlsnima, mogu biti privi ­
legirani pravc i lokova podzemne vode, odnosllo zone 
izdasnih izvora, posebno na mjestima ekstenzijskc dezintc­
grac ije stijena. 

Primjena op isanog 1110dcla bila bi pozeljna Ll terenima 
sa sl icnim geo loskim odnosima, a to znaci u sirokom poja­
Sll Vanjskih Dinarida, iako ni kronostratigrarski ni pro­
storno nije ogranicena i na druge arealc. 

Manuscript received September 9, 1996. 
Revised manuscript accepted April 28, 1997.