Department of Geography, Faculty of Science, University of Zagreb
Abstract
This paper presents the data on the influence oft he sea level change during the last 150000 years on the morphogenetic events int he Kvarner region (the north eastern part of the Adriatic Sea). Some geomorphologic indicators with possible influences on sea level changes, such as sea bottom morphology, the submarine zone sediments disposition, karsification depths, cave development depths and others have been analysed. The present land, coastal, and submarine relief in the Kvarner region was formed as a consequence of tectonic movements, different lithology, climatic changes, and sea level fluctuations during the late geological history, but also because of the erosional amd accumulation processes caused by these changes. The remnants of the older morphogenetic phases have mostly been destroyed. The riverbeds were cut into the bedrock to -60 m beacuse of the sea level fall during the Würm. The carbonate rocks were karstified 70 m below the recent sea level. The present sediment distribution in the Kvarner submarine zone is a consequence of several morphogentic phases correlated with the sea level changes during the Late Pleistocene. Due to much lower sea level in some periods of the Würm glacial the connections between the Rijeka Bay, Kvarnerić, Vinodol and Velebit channels and the open Adriatic were reduced or even interrupted. In the depressions of the Rijeka Bay, Vinodol, and Velebit Channel during periods of lower sea level, lakes could be formed and only the Kvarnerić Bay could have remained connected to the Central Adriatic basin. In this period the Cres – Lošinj archipelago elevations were a morphologic barrier that divided open Adriatic sedimentation zone from the relatively isolated Kvarner region. Therefore the sea bottom is considerably deeper eastern (-70 to -90 m) than western of the Cres and Lošinj islands (-40 to -50 m). That is also the reason for the bottom sediments western of Cres – Lošinj archipelago to be mainly sandy. while those on eastern side to be more silty. Due to the lower sea level, the terrigenous material deposition occurred deeper and farther away from the present coastline, in areas where terrigenous influence is neglibible today. According to the traces of the ancient riverbeds in the Kvarnerić region the sea level at the peak of Würm was more than 100 m below present position. Marine terraces on -45 m and tidal notches on -19 m might have been formed during periods of the slower sea level rise or even its temporal stagnation during the Würm-Holecene transgression.U radu se prikazuje utjecaj promjene morske razine tijekom posljednjih 150 000 godina na morfogenetska zbivanja u području Kvarnera (sjeveroistočni dio Jadranskog mora). Analizirani su oni geomorfološki indikatori koji bi mogli ukazivati na promjene morske razine: morfologija dna, raspored dna, raspored sedimenata u podmorju, dubine okršavanja, dubine razvoja spilja i slično. Recentno kopno, obalni i podmorski reljef u području Kvarnera su posljedica tektonskih pokreta, različitog litološkog sastava, klimatskih promjena i fluktuacije morske razine tijekom mlađe geološke prošlosti, ali također i posljedica erozijskih i akumulacijskih procesa prouzročenih tim promjenama. Tragovi starijih morfogenetskih etapa uglavnom su uništeni. Zbog snižavanja morske razine tijekom virma korita vodotoka usječena su u podlogu do -60 m. Karbonatne stijene su okršene 70 m ispod današnje razine mora. Današnji raspored sedimenata u podmorju Kvarnera posljedica je nekoliko morfogenetskih etapa sukladnih promjenama morske razine tijekom gornjeg pleistocena. Tijekom niže razine mora u nekim razdobljima virmskog glacijala veze između Riječkog zaljeva, Kvarnerića i Vinodolskog i Vinodolskog kanala i otvorenog Jadrana bile su reducirane ili čak prekinute. U razdobljima niže morske razine u depresijama Riječkog zaljeva, Vinodolskog i Vinodolskog kanala mogla su preostati jezera, a jedino je Kvarnerić mogao ostati povezan s morskim bazenom srednjeg Jadrana. U tom razdoblju uzvišenja Cresko-lošinjskog otočja bila su morfološka barijera koja je odvajala sedimentaciju u zoni otvorenog Jadrana od relativno izoliranog akvatorija Kvarnera. Zato su dubine mora znatno veće istočno od Cresa i Lošinja (-70 do -90 m) od onih na zapadu (-40 do -50 m), te su sedimenti zapadno od Cresko-lošinjskog arhipelaga pretežno pjeskoviti, a istočno više muljeviti. Zbog obalne linije koja je bila niža i dalje od današnje, taloženje krupnozrnatih terigenih sedimenata zbivalo se dublje i dalje od recentne obalne crte, u području gdje je utjecaj terigene sedimentacije danas zanemariv. sudeći prema usječenim dolinama vodotoka kojim su tekli do bazena Kvarnerića, more je na vrhuncu virma bilo preko 100 m niže. Tragovi marinskih terasa na -45 m i plimskih potkapina na -19 m mogli bi biti posljedica sporijeg rasta ili čak stagnacije morske razine tijekom virmsko-holocenske transgresije
