I 
GEOL. CROAT. SOil !OS - 110 2 Figs. ZAGREB 1997 

The Morphogenesis of Submarine Springs in the Bay of Kastela, Croatia 

Franjo FRITZ I and Stjepan BAHUN' 

Key words: Submarine spring (vruJja), Morphogenesis, 
Hanging barrier, Coastal karst spring, Adriatic Sea, 
Croatia. 

Abstract 
Offshore, in the !Jay of Kastela, karst groundwater, which initial­

ly flowed under a hanging karst barrier, flows out from two subma­
rinc springs. The waler !lows from fissures enlarged by corrosion and 
erosion at siles (hal were previollsly coastal karst springs. They were 
submerged due 10 sea level rise at least 7,000 years ago and, since 
Ihallimc, they function as submarine springs, at about 32-35 III below 
sea level. 

1. INTRODUCTION 

In the Bay or Kastela, which extends between Split 
and Trogir, two submarine springs (or vrl/ljas - as such 
watcr phcnomena are called in the Croatian Adriatic 
coast) occur (Fig. 1). The submarine spring Arbanija is 
about 800 m and the Slatina about 3200 m from the 
mainland. The data on their depth differ. After 
ALFIREVIC (1960), the both submarine springs dis­
charge from the bottoms of doline-like depressions: 
Arbanija at 35 m and Slatina 32 m below sea level. 
BREZNIK (1973) mentioned that the Arbanija is at 32 
m and the Slatina at 39 III depth. Both authors concur 
that the Kastela Bay bottom around the submarine 
springs is mainly flat and about 15 m below sea level. 
Thc depth differences of the submarine springs (-32, -
35 , and -39 m) are unimportant in the interpretation of 
submarine spri ng morphogenesis, thcrcfore, Alfirevic's 
measured data (Breznik did not mcasure them; pers. 
comm.) will be used in continuation. 

The submarine springs are intermittent and, in the 
winter, they are of a large size, and thus probably have 
large discharge rates. ALFIREVIC (1966) observed the 
activity of these submarine springs once a month during 
the hydrological ycar 1963-64 and states that they 
became active between 20 November and 18 Dccember 
1963 and ceascd to discharge between 16 April and 18 
May 1964. During a wet period, the author recorded a 

I Institute of Geology, Sachsova 2, I-IR-IOOOO Zagreb, Croatia . 

2 Department of Geology and Palacontology, Faculty of Sciences, 
Zvonimirova g, HR - IOOOO Zagreb, Croatia. 

sea water sink into the submarine spring Arbanija and 
required this to be confirmed by tracing (ALFIREVIC, 
1969). The endeavour was not successful due to poor 
visibility and a low sink rate. Furthermore, with regard 
to the submarine spring activity, he concludes that "two 
time periods can be sharply distinguished: the winter 
period including thc latc autumn and eady spring and 
the summer period with the late spring and early 
autumn". ALFIREVIC (1966) also states that the sur­
face water is warmer than the bottom water during win­
ter activity (the coldest waler was that from the Arbani­
ja, measured in February, at 10.6°C), which is the con­
verse situation to that of thc surrounding sea water. In 
the summer, during thc submarine spring "rest" (i.c. 
inactivity), the temperature of the submarine spring 
water equals that of the surrounding sea (in the Arbani­
ja, the maximum in Septcmber was 24.4°C). These two 
periods can also be differentiated in terms of salinity, 
During the winter, the sea has a normal sali nity distribu­
tion (the surface water is less saline and the emerged 
groundwater more saline) while the submarine spring 
water has the opposite situation. Low salinity values 
calise the appearance of frost in the central part of the 
Kastcla Bay when special meteorological conditions 
occur. In general, sea water is more saline during the 
summer than in the winter. 

In September 1971, Alfirevic succeeded in confirm­
ing the water sink in the Arbanija submarine spring 
(MIJATOVIC, pcrs. comm. 1972). 20 kg of sodium llu­
oreseein was used on that occasion and it gradually dis­
appeared into the submarine spring. It was proof that 
this submarine spring is also a ponor (swallow hole), 
i.c. that it is an estavelle. 

2. GEOLOGICAL AND PALAEOGEOGRAPHIC 
EVENTS 

A large volume of fresh water flows out from the 
mentioned submarine springs which, no doubt, is karst 
groundwater derived from the hinterland (Fig. 1), Since 
the whole coast and a part of the offshore Bay o[ 
Kastela is composed of impermeable Eocene flysch 
deposits, overlain by a permeable Cretaceous-Palaeo­
gene carbonate complex, the flysch deposits provide a 
hydrogeological barrier [or mainland karst groundwater. 
Thereforc, the groundwater, on its way 10 the submarine 



106 

Catchment area of vruljas 
and Pantan spring I I 
Sliv vrulja i izvora Pantan 

Catchment area of springs 
Jadro and Zrnovnica I 
Sliv izvora Jadro i Zrnovnica 

K o z 
J 

a 
b 

a 

2 -

Geologia Croatica 50/1 

k 

3 4 5km 
s-=l d 

~1 \, 3 fI 5 <>--0- 6 ...J,......J... 7 

Fig. 1 Hydrogeo logical map of" the Bay of Kastcla, Southern Croalia. Legend: 1) impclmeabJe rocks (Eocene flysch); 2) permeable Crclaccous­
Palaeogene carbonate rocks; 3) brackish spri ng, pcrmancm; 4) brackish spring, intcrmi!lcnl; 5) submarine spring; 6) watershed; 7) major 
reverse fault. 

spri ngs, must pass beneath those impermeable rocks 
(Figs. 1 and 2). The barrier in one part does nol extend 
deeply enough underground and forms a "hanging" bar­

rier. From this point laterally, the flysc h deposits have 
function of a true (entire) barrier. Under these condi­
tions, a large volume of karst groundwater, partly 
reta rded by flysch deposits ill the western part of the 
Bay of Kastela, is drained towards the hanging hydro­
geological barrier. Taking into account the present 
groundwater discharge from the drainage basin Pantan­
Sianac-submarine springs, on average from 1- >30 m3/s 
of brackish water flowed out from these submarine 
springs (FRITZ et aI., 1993). Were earlier precipitation 
more abundant, even greater rates of submarine spring 
discharges may be assumed. 

If the origin or these submarine springs is cons id­
ered, we have to return to not too far past, to the period 
between the last glacial stage and the present condit ions 
in the areas wherc karst groundwater had hydrogeologi­
cally open pass towards its erosional base - towards the 
sea. As a ru le, w ith some exceptions caused by local 
hydrogeological conditions, the sea level is the erosion­
al basis for karst groundwater and, below it, there is no 
recent karstification that would penetrate toward greatcr 
depths. Under such conditions, the karst springs of 

Wiinn glacial age were mai nly coastal brackish spri ngs 
as are the present springs. Meanwhile, thc altitude of 
the erosional base has changed due to the influence of 
sea level fluctuations (eustatic changes) and/or because 
of tectonic movcment of the land surface. It refers pri­
mordially to the question of whether the present ero­
sional basis is also the karstification basis or it is si tuat­
ed in an al ready karstified medium. Since we have no 
more accurate data about neotectonic movements in this 
region, we shall accept the known and wide acknow­
ledged data presented by SEGOTA (1962, 1968) and 
SEGOTA & FILIPC]C (1991) on sea level fluctuation 
from the Wiirm till the recent time, which states that all 
the old coastal springs would have been submerged, 
becoming submarine springs due to a global sea level 
risc betwecn the WUrnl and approximately 1,000 years 
ago. This resulled in a gradual migration of the subma­
rine springs in the direction of the present coastl ine. 

As a result of the hydrogeological conditions in 
karst terrains, the sea level change (coastal movement, 
or rather the movement of the erosional base) is always 
accompanied by the appearance of new coastal springs. 
From a primordial spring, several hydraulically con~ 
nee led submarine springs could have been formed, as 
well as the coastal spring occurring at the present coast. 



1 Fritz 1& Bahull: The Morphogenesis of Submarine Springs ill the Bay of Kastela, Croatia 107 

1m) 
.. 100 

PLANO 
BAY OF KASTELA 

KASTELANSKI ZALJEV 

Slanae Arbanija Slatina 

-- --·Ik: YXX <X ~ 

~99 :88 :88600( :& ~ :ssz<95O XX:X <XX 

o 

-100 

""""'~I Iii I 
-~ 

1 
T 

Fig. 2 Schematic hydrogeological cross section, Legend: I) impermeable rocks (Eocene llysch); 2) permeable Cretaceous-Palaeogene rocks; 3) 
submarine spring; 4) assumed groundwater llow direction during rainy season; 5) assumed position of the boundary between flysch and 
limcstoncs. 

Therefore, the most distant submarine springs graduaJly 
become inactive or are intermittently active, during the 
maximal rates of mainland water flow. This is the rea­
SOil why most present submarine springs are situated 
relatively near the prcsent coastline, and also why a 
small number of them are pennanently active and why 
the largest portion of karst groundwater flowing from 
the mainland hinterland during dry seasons does not 
emerge from submarine springs but along the coastline, 
from brackish coastal springs, 

The submarine springs in the Bay of Kastela differ 
considerably from the described scheme of the appear­
ance of Croat ian submarine springs because their posi­
tion has not changed during the Holocene. Such a fact, 
in the genesis of kars t phenomena, is not surprising in 
this area as the result of the desc ri bed hydrogeological 
conditions including especially the groundwater flow 
towards the considered submarine springs (Fig. 2). The 
submarine spring Arbanija occurs as close to the main­
land as is at all possible. It appears in the boundary 
zone between permeablc carbonate and impermeable 
flysch deposits, even within marginal Eocene flysch 
deposits (ALFIREVIC, 1966). The submarine spring 
Slatina is about 3500 m from the mainland. It is , 
according to the available data, the most distant Adriat­
ic submarine spring to which groundwater flows from 
the mainland. The true silUation is probably more com­
plex, particularly in the zone between the Arbanija and 
Sial ina submarine springs, but we do not have more 
detailed data on the hydrogeology of this part of the 
slUdyarea. 

Thc reconstruction of sea level fluctuations , as men­
tioned above, indicates that the beginning of the recent 
sea level rise occurred after the last glacial stage, some 
25,000 years ago, and it has risen approximately 96 m 
(SEGOTA, 1968). The spot altitudes where water 
cmerges from the subma rin e springs arc -35 or -32 m 
(Arbanija) and -32 or -39 m (Slatina) arter ALFIREVIC 
(1966) nad BREZNIK (1973). This indicates thai both 
submarine springs werc formed after the last glacial 
stage, i.c. during the first part of the last 25,000 years, 
or 10,000 - I 1,000 years ago according to SEGOTA 

(1968). Since then, this area has becn submerged and 
these submarine springs have definitely been formed 
from older springs. 

The springs, which preceded the present submarine 
springs, ceased to function over two time periods in the 
Bay of Kastela. The first period is re lated to the Riss 
glacial stage, i.e. to the penultimate fall of the global 
sea level, belwcen 200,000 and 110,000 years before 
the present time, when the sea level fell 10 the deepest 
position, to -110 m below the present level. If the pre­
sent submarine springs were formed during the penulti­
mate glacial, i.e. between about 200,000 and 110,000 
years ago, when they were al ready submarine springs 
this could have occurred between 11,000 and 75,000 
years ago. That is to say, then the sea level was higher 
than their surface sites, and the highest elevation (+17 
m) was reached about 96,700 years ago. In this case, 
the Day of Kastela depression and the area where the 
present submarine spring occur would have twice been 
an erosional basis for the karstification of the present 
drainage basin of the neighbouring springs Pantan and 
Slanac and the submarine springs Arbanija and Slatina 
(Fig. 1). 

The second period is related to the WUrm glacial 
stage, i,e. to the last sea-level [all below the spring site, 
or below the site of the present submarine springs 
(about 75,000 years ago). Since then, the most intensive 
erosion-corrosion processes, or optimal climatic condi­
tions for the development of springs within the 
palaeodepression or the Bay of Kaste la occurred after 
the lowest sea level position (96.4 m below the present 
sea level occurred some 25,000 years ago) unti II the 
submergence of the spri ngs, 10,000 to ! 1,000 years 
ago, i.e. during the latest Pleistocene. The transforma­
tion of springs into submarine springs coincide approxi­
mately with the beginning of the Early Holocene, when 
the climatic conditions became relatively calm. \Vith 
the gradual sea-level rise (i.e. the erosional base for the 
neighbouring karst groundwater) the groundwater table 
within the carbonate hinterland also gradually rose. 
This resulted with ever longer siphonal groundwater 
tlow paths to the submarine springs. As a result of fur-



IDS 

ther sea- level ri sc, karst groundwater began to flow out 
on the land itself, at the upstream side of the hanging 
barrier, first from the Pantan spring and later from the 
Slanae spri ng (Fig. I). 

The submarine sp ring activity decreases with the 
recent sea-level rise and karst groundwater begins to 
flow out at increasing rates from higher altitudes, e.g. 
from the Pantan spring. The submarine springs afC 

nowadays active only during the rainy season and the 
Pantan spring has become a signi fi cant permanent karst 
brackish spring. During dry seasons, as mentioned 
above, the submarine spring Arbanija even draws in sea 
water, so this water phenomenon is in fact a submarine 
est3vclle (brackish water flows out during the winter 
while sea water sinks into it during the summer). This 
term, a submarine es tavelle, has not yet been used in 
the literature; it has becn known only as the submarine 
spring Arbanija. 

The questions of whether the submarine springs in 
the Bay of Kastcla have been active during one or two 
periods of time, and whether the groundwater conduits 
towards these submarine springs were karstified during 
one or two cycles, have not been resolved. The appear­
ance of submarine springs in the Bay of Kastela at only 
two sites, and the appcarance of younger springs at the 
contact between impenneable and permeable rocks at 
the "upstream" part of the barrier also at only two sites 
(the Pantan spring at the alti tude of 2.7 m above sca 
lcvel and the intermittent spring Slanac even about 30 
m above sea level), together with a relatively low sea­
level elevat ion (+ 17 m) suggests that thc water conduits 
towards the submarine spri ngs were dcveloped during 
the second part of time period which began about 
75,000 years ago. The most intensive karstification 
period occurred between about 25,000 and 10,000 years 
ago, at the end of the Pleistocene. During this time, 
only the karst springs at the present submarine spring 
sites were active. According to the concept that the sub­
marine springs are active only from the last sea-level 
fall, they then became ac tive by the beginni ng of the 
Holocene and are of Holocene age. Such a conclusion 
is in accord wi th the idea that the karstification cycle 
from the end of the Pleistocene and its continuation 
wi thi n the Holocene is related to the development of 
groundwater flow conduits towards the present karst 
springs and that the present re lief was formed during 
this pcriod (BAHUN & FRITZ, 1987; FRITZ, 1991, 
1992). 

3. THE MORPHOGENESIS OF SUBMARINE 
SPRINGS AND THEIR DEVELOPMENT 

Thc morphology and geology of the area where the 
submarine spri ngs appear has been studied by ALFIRE­
VIC (J 966, 1969). He writes that the morphologic 
aspect of submarine springs coincide with the fossil 
ponikvas (doli nes, sinkholes) formed during the conti­
nental phases of the littoral Dinaric Karst and that the 

Geologia Croatica 50/1 

submerged submarine springs, according to their litho­
logical and micropaleontological compos ition, occur 
within Eocene marly limestones which, according to 
their geological structure, coincide with the flysch syn­
cline of the Bay of Kastela. Furthermore, the author 
writes that the divers recorded "the rocky edge of a con­
ical depression" i.c. the ex istence of the funnel of a 
compact lithological composition (1969, p. 189). 

Further exploration has not been performed, thus, 
according to the mentioned data, the "ponikvas", from 
where the submarine spri ngs emerge, should occur 
within fl ysch deposits. It would be exceptional for the 
submarine springs to appear out of calcareous­
dolomitic rocks. Our opinion is that there are interlayers 
of calcarcous rocks, close to the considered submarine 
springs, through which groundwater nows from the 
hinterland, beneath the impermeable rocks, to the 
spri ngs or submari ne springs, Le. that the submarine 
springs occur within the contact zone of impermeable 
calcareous and impermeable flysch deposits. The 
impermeable rocks comprise the whole area between 
the submarine spring Arbanija (at the village of Divu­
Ije) and the springs Slanae and Pantan (Figs. 1 and 2). II 
is not important whether the final condui ts to the sub­
marine springs occur in limestones of the Cretaceous­
Palaeogene complex or calcareous breccias which are a 
constituent of flysch . In the both cases, the now of 
water towards the springs (submarine springs) is 
siphonal and it passes through calcareous rocks. The 
submarine spring water Ilows out, as also from most 
karst coastal springs in the Adriatic littoral, mostly 
along a reverse or thrust contact of permeable and 
impermeable rocks, probably from a calcareous inter­
layer within, in general, impermeable t1ysch deposits. 

Within our concept of the origin of subm arine 
springs in the Adriatic sea, as described above, the sub­
marine springs are submerged earl ier karst coastal 
springs. From that point of view, the depths of subma­
rine springs: -32 m and -35 m (after ALFIREVIC, 
1966) and even -39 m and -32 m (after BREZNIK, 
1973) have to be analyzed taking into account the pre­
sent depths of the bOllom of the Bay of Kastela, 15 m 
below sea leve l, because the fanner springs were defi­
nitely submerged only when the Bay of Kastela bottom 
was submerged. Therefore, the dilemma of the depth of 
these submarine springs should be resolved by the 
assumption that the fomler springs were at the level of 
palaeorelief, i.e. at the contemporaneous level of the 
Bay of Kastela bottom, naturally without the sediments 
deposited later. Therefore, it should be said that a sub­
marine spring is a spot at the sea bottom from whcre 
permanently or intermittently fresh or brackish water 
flows out, as it happens in brackish coastal springs in 
the mainland. Thus, it is not important how deep a 
water bearing fracture penetrates below the land surface 
or sea bottom or what size it is. 

In order to display a comparison, let us see what 
happens in a major coastal brackish spri ng, e.g. the 
Pantan spring, especially regarding its "morphological 



I Fri tl. l& l3ahun: Thc Morphogencs is of Submarine Springs in the Bay of Kastela. Croat ia 109 

aspect". \Vater emerges from the bottom of a lake 30 x 
60 m in size that is 2.7 III abovc sea level and about 12-
13 III below the lake water surface. This water emerges 
from the base or a depression, 9-10 III below sea level, 
fro m a 40 m long frac ture (FRITZ e t aI. , 1993) . The 
spring is situatcd in a thrust contact between permeable 
limestones o f the Palaeogene-Cretaceous complex and 
impermeab le fly sch, whil e the lake and frac ture are 
within fl ysch deposits. The Pant an spring morphology 
is interesting. The spring site has a funnel fonn , resem­
bling a ponikva (do line, s inkhole) and water emerges 
from the bottom of this "funnel" , rrom a widened frac ­
ture . Consequently, almost the same re li e f form , 
observed at the submarine spri ngs in the Bay of 
Kastela, also occurs at ascend ing springs or at springs 
with siphon al conduit s, as observed in the Pantan 
spring. Similar morphological form s also occur at the 
Jadro and Ombla springs which are the most well 
know n Croat ian karst spri ngs. The morphology of the 
bottom of the submarine springs in the Bay of Kastela 
resembles morc a widened fracturc, as at most ascend ­
ing karst springs, than a ponikva. Thi s can be concluded 
from the photos of Ihe s ubmarine spring S latin3 
(J\ LFIREVI C, 1966, 1969) and from the echogram of 
the submarine spring Arbanija (ALFIREVIC, 1969). In 
addition, it is necessary to emphasize lhal lhe genesis of 
ponikvas, as karst re li e f form s, is difficult to explain 
when they occur within Jlysch deposits. 

The refore, the present submarinc springs, do not 
deri ve from ponikvas. They arc frac tures widened by 
water and initiated by tectonics in the zones of thrust 
and reverse movements and through which water flew 
toward coastal springs during earlicr time phases. 

By considering the morphogenesis of these subma· 
rine springs, it may be concluded that the submarine 
springs (coas tal springs) of the Bay of Kastela wcre the 
erosional base for the pertinent groundwater during the 
Pleistocene epoc h. In the Holocene, the erosional base 
g raduall y rose to a hig her altit ude, where the Pantan 
and Slanac springs appeared as outl ets for the earlier 
formed "privileged" groundwater condui ts serving the 
submarine springs. This is why in the immediate hinter­
land of the Pantan and S ianae springs it is assumed that 
th e occurrence of a hi ghest porosity of calcareous 
rocks, the rocks of "privileged" groundwater nows is at 
a lower altitude than the present sea level. FUJ1helmore, 
until re lati vely recentl y the largest portion or ground ­
water deri ved from the entire drainage basin probabl y 
fl owed through siphonal conduits toward the submarine 
s prings in the Bay of Kastela. Thi s flo w enab led the 
development of recent karstification in the hinterland of 
the submarin e sprin gs reachin g unknown depths 
beneath and behind the mentioned hanging hydrogeo­
logical barrier. 

When the submarine springs are inactive, sea water 
mi grates landward through the whole calcareous per­
meable mediulll occurring below the hanging hydroge· 
o log ical barrie r, prim aril y through the s iphonal con­
duit s. Thi s sea water intru sion vari es durin g the ycar 

because of different hydraulic conditions and the same 
happens with the fl ow of fresh (brackish) watcr toward 
the submarine springs, both causing complex relations 
between sa line and fresh water. Intermitte nt flows o f 
brackish water from the S lanae spring occurring 30 m 
above sea level (be ing the g loba l a ltitude record for a 
coastal brackish spring - FRITZ, 1992 , 1994) , is the 
consequence of the rapid infl ow of large quantities of 
water from the calcareous h inte rland under the 
described hydrogeological conditions. The higher water 
salin ity in the Sianac spring than the Pantan spring at 
the same time together wit h the described submarine 
spring genesis indicate that the route of sea water pene­
tration int o the land is from the submarine springs, to 
the Sianac spring, then furth er into the land, mainl y 
separately from the underground nows toward the Pan­
tan spr ing. T he geographic shift and rise in altitude of 
the erosional base from the submarine springs toward 
the Pantan and Sianae springs, together with the gradual 
increase in discharge rate at the Pantan spring are the 
results of the last sea level ri se. The submarine springs 
that had earlier been permanent graduall y became inte r­
mitt ent and periods of their inac tivity became ever 
longer thus the submarine springs gradually died orr. 
Then, the permeable strata situated in the hinterland o f 
the hang in g hydrogeo logical barrie r became large ly 
filled with sea water and this is one of the reasons why 
the brackish Sianac spring occurs at such a high alti tude 
above sea level. It is difficu lt to predi c t whether th e 
s ubmarine springs in the Bay of Kaste la will die off 
entire ly by the end of the present interg lacial stage 
when the sea level should rise by an additional 1.17111 
(SEGOTA , 1968), but , there is no doubt that the pcri ­
ods of submarine spri ng inac tivity wi ll become longer 
and the coastal Panlan spring will di scharge mo re 
water. The sea level ri se will probably be greater than 
[ .17 m due to the still unknown mag nitude of the 
at mospheric temperatu re rise caused by human activity_ 

4. CONCLUSION 

The submarine sp rings of the Bay of Kastela arc 
unusually fa r from the mainl and and the grou ndwater 
on which thcir activity is dependent. They arc a conse­
q uence or many reverse and aJlochthono us rela ti o ns 
wi th in thc Cretaceous-Palaeogene carbonate comp lex 
and Eocene nysch deposits. Thus, the coastal area and a 
large part of the bottom of the Bay of Kastela are built 
o r impenneable fl ysch deposits. This is the reason why 
part of the groundwater percolates above a flysch barri­
er (th e Pan tan and Sianac spri ngs ) and the o th er part 
nows beneath this ba rrier to the subma rine Arbanija 
and S latina springs in the bay. 

The published data on the submarine spring mo r­
phology s upport the idea that the subm arine sprin gs 
were form ed when the bottom o f the prese nt Bay of 
Kastela was above sea level. T he submarine spring 
morphology can be exp lained as a result of the erosion 



110 

and corrosion of tectonic frac tures along which ascend­
ing water flowed toward original karst springs within 
the Bay of Kaste la paiaeociepress ion. During the last 
sea level rise , these springs were submerged by the sea 
and so became submarine springs. 

The question of the age of the submarine spring 
remains open. The supposed age of 10.000 to 11.000 
years is based on published data that the submarine 
springs are between 32 to 35 III below present sea level 
and that they were active on ly aetcr the last g lac ial 
s tage. If the morphoge netic concept described in this 
paper is accepted, i.e. that the present submarine 
springs are submerged ascending karst springs, then the 
submarine spri ngs are younger, because water flowed 
out from the former springs at the level of the present 
bottom of the Bay of Kastela, i.e. about 15 m bclow the 
present sea level. The sea level reached that elevation 
SOIllC 7,000 years ago (SEGOTA, 1968; SEGOT A & 
FILIPCIC, 1991), meaning that the former springs have 
ex is ted as submarine springs during the last 7,000 
years, Thi s is, probably, the real age of submarine 
spring activity in the bay of Kastela, The difference in 
these proposed ages of the submarine springs, obvious­
ly , is not large - whethe r we accept that the submarine 
spri ngs are situated a little more than 30 m (10,000 to 
11,000 years) or about 15 m below the present sea level 
(7,000 years) because the sea leve l rise decelerates with 
time. After SEGOTA (1968), during the present inter­
g lacial stage, the sea level w ill continue to rise during 
the next 1,900 years and it will only be approximately 
1.17 m higher than presenl. During this period, the sub­
marine springs wil l become more inactive, while ever 
more water wi llllow out from the Pantan spring during 
the rainy seasons, and the re fore, the submarine springs 
will most probably "die off'. 

Acknowledgments 

The author wishes to express his appreciation to 
Lui gi TULIPANO. from the Istituto di Geologia Appli­
cat a e Geotechnica, Politecnico di Bari, Italia and to 
Bozidar BIONDlC. Ivo VELIC and Ante SAR1N from 
the Inst itute of Geology, Zagreb, Croatia - for all their 
thorough and effective remarks and help. Also grateful 
thanks to Julie ROBSON for her language editing. 

Geologia Cro:l1ica 5011 

6. REFERENCES 

ALFIREVIC, S. (1966): Les sources sOlis-marine de la 
Baie de Kastela.- Acta Adriatica. 10/2. 1-38, Split. 

ALFIREVIC. S. (1969): Jadranske vrulje u vodnom 
rezimu Dinarskog priobalnog krsa i njihova prob­
lematika.- Krs Jugos!., 6, 183-206. Zagreb. 

BREZNIK. M. (1973): Nastanak zaslanjen ih kraskih 
izvirov in njihova sanacija.- Geologija, Razprave in 
porocila, 16.83-186, Ljubljana. 

BAHUN, S. & FRITZ, F. (1987): Postanak izvora 1I 

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Manuscript received April 4, 1996. 
Revised manuscript accepted Apri l 28. 1997.