GEOL. CROAT. 50/2 1 157- 160 1 ZAGREB 1997 

Professor Herak's Contribution to Regional Geology and Geotectonics 

Josip BENIC ', Ivan BLASKOVIC' and Vladimir TOMIC' 

A deep insight into the s trati g raphy ancl reg ional 
g~o logy of many countries from several continents, as 
well as acquaintance with geotectonical references and 
experience from many detailed fie ld explorations of 
"c rucial cases" gave Herak an original altitude and 
unique way o r approaching geotec tonic problems. 

Although g lobal tectonics was never actually his 
pr imary scient ifi c objective, some practica l problems 
persuaded Il c rak of the necessity 10 understand the 
structural relationships of any studied area. 

The first scientific contributions of global tectonics 
ex tend to the carly days of Herak's career. Apml [rom 
<In acquaintance with stratigraphy, practical problem s 
!110slly of a hydrogeolog ical nature required ex plana­
ti on of the struc tural re lationships in the in ves tigat ed 
a reas. Thus, as early as 1959, in his paper on the geolo­
gy and hydrogeology of the island of Hvar, the under­
ground water system of thc island was explained with 
the aid o f a del imi ted anticline. Only a year later, by 
d isclosin g the Middle Triassic anticline in the Ric ica 
po lje he e luc id ated the mechani sm of sinking and 
upwelling of the local ground waters (HERAK , 1960). 
Apart from its scienti fic contributi on, the latter was also 
important in planni ng the accumulation basi n of the 
Obrovac electri c plant. 

It seems that the significant moment for Herak 's 
geotecton ic inc lination occured in 196 1, when he stud­
ied geologica l relationships in the upper course of the 
Kupa river, with the purpose or inves tigating possibili ­
ties for the accumu lation of water. It was thcn that Her­
ak and hi s coworkers published the paper "New ele­
ments of tec tonics in the upper course of the Kupa riv­
e r". In stead of being autochthonous with Palaeozoic 
an ti c linal corcs, they di scovered tha t both Palaeozoic 
nnd Triassic sediments lay allochthonously over Juras­
sic carbonate rocks. [-Ie ex posed hi s vi si on or tectonic 
upheavals in the Dinaricles at the International Congress 
in Bar in 1971. One should not ove rl ook the sc ientific 
paper 0 11 the tectonic in te rpretation of evapor ites of the 

1 Ins!i lu!e of Geology. S<lchsova 2, P.O. Box 268. IIR -lOOOO Zagreb, 
em;lIia. 

2 PactdlY of Mining, Geol ogy and Pelro leum Engineering, Un iversily 
of Zagreb. Pierollijeva 6, HR · I 0000 Zagreb, Croatia. 

.1 Departmen! of Geology and Pa taeo ntology. Facu hy of Science, 
University o f Zagreb. Ul. kralja Zvoni mi ra S, HR -IOOOO Zagreb, 
CrO;l! ia. 

Dalmatian Zagora, ei ther (HERAK, 1973). He late r 
re interpreted this idea in hi s capital work on tectonics 
publi shed in 1986, in which the thrusts from the north­
eas t had been subs tituted with continental s ubduc ti on 
from the southwest, that is, with subduction of the Adri ­
atic beneath the Dinaric plate, taking into consideration 
his observations from earlier work. From then on , Her­
ak was no longer sa tisfi ed with the Ilumerous geotecto­
nic models that describe the struc ture of the Dinarides 
based on the theory of geosynclines with double oroge­
ny. He unde rstood that something must be radi call y 
changed in the basic concepts of Dinaric geotcctonisrn. 
Painstakingly col lecting the fi e ld data, analysing them, 
and reeva luat ing all accessible elata, parti cul arly in the 
area of Gorski Kotar, Velcbit Mountain and Lika, Herak 
discovered the ex istence of allochthonous tectonics in 
the reg ions form erly treated entire ly as autochthonous 
in origin. He reconstructed the mechanism or movement 
with two cardina l iss ues: a) the cause of mo veme nt 
must be sought muc h deeper ("subc ru sta lly '"), while 
subduction is direc ted toward the north east ane! 
obstructed from withi n the cru stal zone; b) the intensity 
of allochthony increases with the depth. 

This point of view is bas ically differe nt from co­
existing opinion s, bccause all geotectonic concepts 
about the structure of the Dinarides held that the thrust­
ing was directed [rom the northeast toward southwes t. 
All this was exposed as early as 1980 in hi s first pio­
neering work based on mobilis ti e ideas: "The system of 
nappes betwcen Vrbovsko and Delnice in Gorski KOlar 
(Hrvatska)" (HERAK , 1980). Today, the re is no doubt 
that Herak had already presupposed the continental sub­
duction (A-subduction) which, a lthough under diffe rent 
name, would later im print the tec toni cs or the Din ar­
ides. 

Since 1980 Herak has been directing hi s sc ientifi c 
curiosi ty increasingly to the e lucidation o f th e geotec­
tonic problems of the Dinarides. Although subduct ions 
on the ocean marg ins were in those days the prim ary 

This paper was presented at the scientific meeting 
dedicated to the 80th anniversary of the life of 

Professor Milan Herak, 
held on March 5th, 1997 in Zagreb 



foclIS of scien tific interes t, he presupposed simultane­
ous subduct ions among separate parts of the cot incnlal 
crust. 

Having realized that an ample conceptual diversity 
desc ribing the teclOn ics of the Dinarides can not be 
reduced to some already recognized common model, he 
preferred to announce his own idea of regional tecton­
ics. Exploring the available literature he recogn ized that 
the concept of plate tectonics had displaced completely 
the classic concept o[ fixism all over the world. There­
fore he tried \0 discover new geotectonic definitions for 
our Croat ian regions as well as abroad . By 1986, Herak 
brou ght to light a new concept of genesis and structure 
of the Dinarides ("A new concept for the geotectonics 
of the Dinaricles") (HERAK, 1986), suggesting an alter­
nati vc for the two princ ipal geotectonic units, mostl y 
called the "Outer" and "Inner Dinarides", and supplant ­
ing them by the four palaeoambi ental and pa laeody­
namic belts. These are reall y four independent palaeo­
geographic units with appointed significance of corre­
sponding paleodynamic units in the period of develop­
ment and structural formation. This is precisely where 
interdependence has been observed between reg ional 
geo logy, which is a basis for the definition of palaeo­
geog raphic unit s, on one side, and geotectonics on the 
other, as far as similar behaviour of the newly promoted 
units in the stages of structural formation is concerned . 
Ex tending continuously from the Peloponnese to the 
Southern Alps these palaeogeographic units arc aligned 
as fo [l ows: "Ad ri atic um ", "Epiadriaticum", " Dinar­
icum ", and "S upradinari cum", each with its spec iric 
attri butes. They occupy mutually allochthonou s pos i­
tions brought about by continental subductions of cer­
tain units under others. Reinterpreting all access ibl e 
data from nUlllerous localit ies and correlating the re lief 
of the Moho discontinui ty with tectonic configurat ion, 
Herak in his subsequent works substantiated his earlier 
conclu sion concerning pronounced Illobilism as a rea­
son for th e origin of allochthonous structures in the 
broader area of the Dinaridcs. This idea gradually pre­
vailed throu gh the tectonic literature, resulting in the 
reex amination of many previous theories about the 
structure of locally confined areas, and sometimes their 
correc ti on. 

The widespread geological community sometimes 
cons iders He rak 's ideas daring and revolutionary, but 
onl y because the whole concept represents the fru it of 
long- last ing re fl ections and thought on the basis of 
bonding theory and cx perience. The scientific results he 
has accomp lished were promptly uti lized in practi ce, 
whi le, in turn , he subsequentl y used applied geological 
results to supplement and improve the fundam ental 
geolog ica[ scientific principles. 

Geologia Croatica 50/2 

REFERENCES 

HERAK , M. ( 1959): Prilog geolog iji i hidrogeo logiji 
otoka Hvara (Zur Geologie und Hyd rogeologie der 
1nsel Hvar).- GeoL vjesn ik, 12 (1958), 135- 148. 

HERAK , M. ( 1960): Geologija Gracackog polja u Liei 
(Geologie des Karst Polje von Gracac in def Lika, 
Kroatien).- GeoL vjesnik, 13 ( 1959), 3 1-56. 

HERAK, M., BOlANIC, L., SIKIC, D. & MAGDA­
LENIC, A. (196 1): Novi clement i tektonike u pod­
rucju gornjeg toka rijeke Kupe (Neuc Elcmente der 
Tektonik im Gebiet des Oberlaufs des Kupa-Flus­
ses).- GcoL vjesnik, 14 (1960), 245-251. 

HERAK, M. ( 1971): Beitrag zur Rekon struktion der 
orogenetischen Dynamik in def Din ariden Kroati ­
ens.- I simp. 0 orog. [az3m<l u prosto ru Ev rope, 
Beograd-Bm (1970), 35-40, Beograd. 

HERAK, M. (1973): Some teetonieal problems or eva­
porit ic area in the Dinarides of Croat ia (Neki tek ton­
ski problemi pojasa s evaporitim a u DinaridimH 
Hrvatske).- GeoL vjesnik, 26 (1972), 29-40. 

HERAK, M. (1980): Sustav navlaka izmedu Vrbovskog 
i Delnica u Gorskom kOIHru - l-Irvatska (The nappc­
s·ystem between Vrbovsko and Delnice in Gorski 
Kotar - Croatia).- Acta geoL, 10/2, 35-5 1, Zagreb. 

HERAK, M. (1986): A new concept or geotectonics of 
the Dinarides (Nova koneepcij a geotekton ike Dinar­
ida).- Acta geoL, 16/1 , 1-42, Zagreb. 

HERAK, M. (199 1): Dinaridi - Mobi lis tick i osvrt no 
genezll i struktllru (Dinarides - Mobili s tic view or 
the genesis and stmcture). - Acta geoL, 21/2, 35-117, 
Zagreb. 



Benic. lll:lskovic & Tomie: llerak: Regional Geology and Geotectonics l.it) 

Doprinos prof. Heraka regionalnoj geologiji i geotektonici 

Dobro poznavanje stratigrafije i regiona!ne geo!ogi­
.Ie mnogih zemalja na vise kontinenata, poznavanjc lite­
rature 0 geotektonici, te iskustvo s brojni h terenskih 
detaljnih istrazivanja "klj ucnih terena", omogucili su 
profcsor Li M. Hcraku original an pristup pri rjdavanju 
gcotcktonskih problema. 

lako mu sira tektonika svojedobno i nij e bila u 
prvom planLi njcgovog znanst venog intcresa, pojedini 
prakticni zadaci su ga uvjeri!i u nuznost poznavanja 
strukturnih odnosa istrazivanih terena. 

Prvi znanstven i doprinosi iz sire tektonike sezu u 
m!adc dane profesora Heraka. Prakticni zadaci vezani 
uglavnom uz hidrogeolosku problematiku trazili Sll, LIZ 

poznavanjc stratigrafije, i Jjesavanjc strukturnih odnosa 
istrazivanih tcrena. Tako nalazimo vee 1959. godinc u 
znanstven01l1 radu 0 geologiji i hidrogeologiji otoka 
Hvara da uz POIllOC utvrdene antik li na!e objasnjava 
podze1l111e vode otoka, a slijedece godine u Ricickom 
polju otkrivanjclll srednjotrijaske antiklinale objasnjava 
mehanizam ponornih i izvorisnih voda, sto .Ie uz zllan­
stvcni doprinos bi lo vrlo va7.110 i za projektiranje aku­
mulacijskog bazena hidroclektrane Obrovac. 

Cini se da je znacajan trenutak za geotektonsko 
usmjcrcnjc bila 1961. godi na pri proucavanju gco loskih 
odl1osa II gornjcm toku rijeke Kupe u cilju odredivanj a 
mogucilosti akumuliranja vode, kada prof. Herak i sura­
dnici objavljlljll rCZll llate II radu "Novi clementi tek­
lonike II podrllcjll gornjeg toka rijcke Kupe". Umjesto 
alltohtonije s paleozojskim jezgram<1 antik li nala, utvr­
dili su da su i palcozojskc i trijaske naslagc alohtone na 
jurskim karbonatnilll naslagama. Slijcdi niz radova 
vezan na stratigrariju i hidrogeologiju, da bi 197 I. na 
Meclunaroclnolll si mpoziju II Boru izlozio svoje videnjc 
tektonskih prollljena u Dinaridima. Ne smije se presko­
citi ni 1973. godine publicirani znanstveni racl 0 tekton­
skoj intcrpretaeiji cvaporita Dalmatinske zagorc, koji u 
SVOl11 kapita lllOl11 tektonskol11 radu 1986. gocline rein­
terpretira zamijenivsi kretanja sa sjeveroistoka kon ti­
ncntalno1l1 subdukeijom s jugozapada, tj. podvlaccnjem 
J\drijatika pod Dinarik uz uvaZavanje svojih zapazanja 
iz starijeg rada. Od laela M. Heraka vise ne zaelovo­
Ijavaju brojni geotektonski modeli gracle Dinarida bazi­
rani na teoriji geosinklinala s dvostrllkilll orogenom . 
Shvatio.ie ela se U osnovnim poimanjima geotektonike 
Dinarida mora ncSto iz korijena mijenjati. Strpljivim 
prikupJjanjcm tcrenske faklografije i njihovom anali­
zom, te revidiranjem postojcCih podataka, prvens tveno 
U podrucju Gorskog kotara, Velebita i Like, otkriva 
prislllnost alohtol1e tektonike u podrucjima koja Sll do 
lada tretirana iskljucivo kao autohtona. Rekonstruirao .Ie 
mehanizam kretanja, gdjc su bitna dva zakljucka: 

a) uzrok kretanja treba lraziti dllbljc ("subkrustalno"), 
podvlacenje .Ie prema sjeveroistoku uz otpore u krllstal­
nom dijelu; b) intcnzitcl a lohtonij c poveeava se od 
povrsine prema dubini. 

Takav prist up .Ie dijametralno suprotan dotadasnj im 
shvaeanjima, jer se II svim geotektonskim koncepcija­
Illa 0 grad i Dinarida smatralo da su kretanja bila ad 
sjcvcroistoka prema jugozapadu. Sve .Ie to receno u njc­
govom prvolll (pionirskom) radu baziranom na l11obi­
list ickoj osnovi vee 1980. god.: "Sllstav navlaka izmedu 
Vrbovskog i Delnica u Gorskol11 kotaru (Hrvatska)". 
Citajuei danas taj rad jasno nam je cia .Ie profcsor Herak 
pretpostavio kontinenlalnu subdukciju (A-subdukciju), 
iako .Ie tada nije tako nazvao, a koja ce kasnije obiljeziti 
tektoniku Dinarida. 

Svoj zllanstveni interes M. Herak .Ie od tada svc vise 
uSl11jeravao na rjesavanje geotcktonskih problema 
Dinarida. Iako se u to vrijcmc pre tezito govori 0 sub­
dukeijama na rubovima oceana (13-subdukcije), U Dina­
ridima pretpostavlja medusobne subdukcijske procese 
dijelova kontinentalne kore. 

Uvidjevsi da vcliku razl1ol ikost ideja 0 tektonskoj 
gradi Dinarida ne moze svcsti na neki poznati zaje­
dnicki mode l, te cia takve interpretacije nemaju rcalnu 
potvrdu u tcrenu, od lucio sc za svoju viziju 0 tektonskoj 
gradi toga prostora. Prollcavajuci aktuall1u litcraturu 
uvidio je da koncepeija 0 tektoniei ploca posvuda u sv i­
jetu preuzima poJozaj klasicnih koncepeija fiksizma, te 
jc zato na tim osnovama pokusao naei nova geotekwn­
ska rjesenja za nas hrvatski prost or i s ire. I konacno -
1986. god inc profesor Herak iznosi novu koneepciju 0 

gcnczi i gradi Dinarida ("A New Concept or Geotecto­
nics of the Dinarides"), gdje predJaze zamjenu dviju 
glavnih gcotektonskih jediniea, koje se najcesce nazi ­
vaju "Vanjski" i "Unutrasnji Dinaridi", s cetiri paleoam­
bijentalna i paleodinamska pojasa. To Sll zapravo celiri 
izdvojenc pa!cogeografske jedinice kojima je clat znacaj 
pa leodinamskih jcdiniea u razdoblju razvoja i slruk­
turnog formiranja. 1 upravo ovdje se vidi povczanost 
regionalne gcologije, kao os nove odrcdivanja palco­
geografskih jedinica i geotektonike u smislu priblizno 
slicnog ponasanja tih jediniea u razama rormiranja 
struktura. Te se jedinice kontin ui rano pruzaju od Pelo­
poncza do Juznih Alpa. To su: "Adrijatik" , "Ep iadrija­
tik" , "Dinarik" i "Supradinarik", a odlikuju se nekim 
spccificnim znacajkama. Mcdllsobno Sll II alohtonim 
polozajima izazvanim kontinentalnim subdukcijama 
jednih jedinica pod druge. U svojim kasnUim radovima 
M. Herak reinlerpretacijom dosaciasnjih poslojecih 
podataka s brojnih lokaliteta i korclacijom izmcclu re!je­
fa Mohoroviciceva di skontinlliteta i tektonske grade 



",,, 

potvrduje svoj raniji zakljucak 0 izrazitom mobilizmu 
kao uzrocniku alohtonih struktura u sircm poctrucju 
Dillaricla. Ideja postupno, al i sigufI10 ulazi u nasu tek­
tonsku literaluru, trazcc i prcispitivanje mnogih dosa­
dasnjih shvacanja struktura uzc omedenih terena, u cilju 
uzajamnog oplodivanja, pa i korekcija. 

U prebogalom i razllovrsnom znanstvenom raclu 
profcsora Hcraka, geotektonski radovi postaju u zadnjih 

IJCl)LVgld I..-'V" ' I<";" _IVI.'.. 

lO-ak godina zacudujucom brzinol11 po opsegu i dubini 
uiaienja u problematiku srcdisnji intcrcs profcsora. 
Samo za siru gcoiosku javnost to su smjeli i revolu ­
ciallami patezi, jcr sve je to p lod dugogodisnjih razmi­
sljanja i sazrijevanja ideja na osnovi spajanja znanosti i 
prakse, gdje znanstvcnc rczuitatc izravno primjcnjujc u 
praksi, a s prakticnim geoloskim rezultalima nadopun ­
java i korigira [undamentalnu geolosku znanost.