Marine and lacustrine sedimentation in a submerged karst basin : The Late Quaternary Lošinj Channel depositional system

Paleookoliši na prostoru današnjeg Lošinjskoga kanala i otoka Cresa mijenjali su se s promjenama morske razine i klime tijekom kasnog kvartara. Depresije u kršu, prisutne na istraživanom području, omogućile su očuvanje sedimentološkog zapisa paleookolišnih promjena. Stoga se paleookolišna rekonstrukcija temeljila na jezgrama sedimenata. Analizirano je ukupno 8 jezgara sedimenata izbušenih u depresijama u kršu. Geokemijske analize, granulometrijske i mineraloške analize, mjerenje magnetskog susceptibiliteta, te izračun fluksa organskog ugljika omogućili su odredbu okoliša koji su postojali na istraživanom prostoru tijekom kasnog kvartara. Mikropaleontološka analiza zajednice foraminifera, ostrakoda, mekušaca i palinomorfa olakšala je interpretaciju prikupljenih podataka. Kronologija jezgara zasnivala se na datiranju metodom AMS 14C. Rezultati analize jezgara sedimenata upotpunjeni su podacima seizmičke refleksije visoke rezolucije. Dobiveni rezultati su ukazali na izmjenu morskih i jezerskih, odnosno kopnenih faza na istraživanom prostoru od MIS 7 do danas, sukladno s varijacijama morske razine. Osnovni čimbenik koji je utjecao na paleookolišni razvoj istraživanog prostora, uz morsku razinu, je dubina praga istraživanih depresija. Interpretacija paleookoliša zasnivala se na korelaciji s modernim analozima kasno-pleistocenskih i holocenskih paleookoliša, odnosno marinskim jezercima danas razvijenim u ponikvama na otoku Cresu.Sea level and climate changes enabled development of different paleoenvironments during the Late Quaternary in the present-day Lošinj Channel and coastal zone of Cres Island. Karst depressions in the investigated area are exceptional geomorphological features for preservation of thick sediment sequences. Therefore, paleoenvironmental reconstruction was based on the sediment cores. Analysis of 8 sediment cores was conducted using the multi-proxy approach and included determination of geochemical and mineralogical composition, grain-size, magnetic susceptibility measurements and organic carbon flux. Paleontological analysis (foraminifera, ostracods, mollusks, palynomorphs) facilitated the interpretation of obtained sediment core data. Core chronologies were based on 14C dating method. The high-resolution seismic data gave an additional insight into the thick sediment sequences preserved in the investigated depressions. The results indicated the exchange of marine and lacustrine or terrestrial environments since MIS 7, in accordance with the Quaternary sea level changes. The main factor that influenced the paleoenvironmental development of the area, except sea level, was the sill depth. The interpretation of paleoenvironments was based on correlation with the modern analogs of the Late Pleistocene and Holocene paleoenvironments, today present in the coastal zone of Cres Island

Marine and lacustrine sedimentation in a submerged karst basin : The Late Quaternary Lošinj Channel depositional system

Paleookoliši na prostoru današnjeg Lošinjskoga kanala i otoka Cresa mijenjali su se s promjenama morske razine i klime tijekom kasnog kvartara. Depresije u kršu, prisutne na istraživanom području, omogućile su očuvanje sedimentološkog zapisa paleookolišnih promjena. Stoga se paleookolišna rekonstrukcija temeljila na jezgrama sedimenata. Analizirano je ukupno 8 jezgara sedimenata izbušenih u depresijama u kršu. Geokemijske analize, granulometrijske i mineraloške analize, mjerenje magnetskog susceptibiliteta, te izračun fluksa organskog ugljika omogućili su odredbu okoliša koji su postojali na istraživanom prostoru tijekom kasnog kvartara. Mikropaleontološka analiza zajednice foraminifera, ostrakoda, mekušaca i palinomorfa olakšala je interpretaciju prikupljenih podataka. Kronologija jezgara zasnivala se na datiranju metodom AMS 14C. Rezultati analize jezgara sedimenata upotpunjeni su podacima seizmičke refleksije visoke rezolucije. Dobiveni rezultati su ukazali na izmjenu morskih i jezerskih, odnosno kopnenih faza na istraživanom prostoru od MIS 7 do danas, sukladno s varijacijama morske razine. Osnovni čimbenik koji je utjecao na paleookolišni razvoj istraživanog prostora, uz morsku razinu, je dubina praga istraživanih depresija. Interpretacija paleookoliša zasnivala se na korelaciji s modernim analozima kasno-pleistocenskih i holocenskih paleookoliša, odnosno marinskim jezercima danas razvijenim u ponikvama na otoku Cresu.Sea level and climate changes enabled development of different paleoenvironments during the Late Quaternary in the present-day Lošinj Channel and coastal zone of Cres Island. Karst depressions in the investigated area are exceptional geomorphological features for preservation of thick sediment sequences. Therefore, paleoenvironmental reconstruction was based on the sediment cores. Analysis of 8 sediment cores was conducted using the multi-proxy approach and included determination of geochemical and mineralogical composition, grain-size, magnetic susceptibility measurements and organic carbon flux. Paleontological analysis (foraminifera, ostracods, mollusks, palynomorphs) facilitated the interpretation of obtained sediment core data. Core chronologies were based on 14C dating method. The high-resolution seismic data gave an additional insight into the thick sediment sequences preserved in the investigated depressions. The results indicated the exchange of marine and lacustrine or terrestrial environments since MIS 7, in accordance with the Quaternary sea level changes. The main factor that influenced the paleoenvironmental development of the area, except sea level, was the sill depth. The interpretation of paleoenvironments was based on correlation with the modern analogs of the Late Pleistocene and Holocene paleoenvironments, today present in the coastal zone of Cres Island

Marine and lacustrine sedimentation in a submerged karst basin : The Late Quaternary Lošinj Channel depositional system

Paleookoliši na prostoru današnjeg Lošinjskoga kanala i otoka Cresa mijenjali su se s promjenama morske razine i klime tijekom kasnog kvartara. Depresije u kršu, prisutne na istraživanom području, omogućile su očuvanje sedimentološkog zapisa paleookolišnih promjena. Stoga se paleookolišna rekonstrukcija temeljila na jezgrama sedimenata. Analizirano je ukupno 8 jezgara sedimenata izbušenih u depresijama u kršu. Geokemijske analize, granulometrijske i mineraloške analize, mjerenje magnetskog susceptibiliteta, te izračun fluksa organskog ugljika omogućili su odredbu okoliša koji su postojali na istraživanom prostoru tijekom kasnog kvartara. Mikropaleontološka analiza zajednice foraminifera, ostrakoda, mekušaca i palinomorfa olakšala je interpretaciju prikupljenih podataka. Kronologija jezgara zasnivala se na datiranju metodom AMS 14C. Rezultati analize jezgara sedimenata upotpunjeni su podacima seizmičke refleksije visoke rezolucije. Dobiveni rezultati su ukazali na izmjenu morskih i jezerskih, odnosno kopnenih faza na istraživanom prostoru od MIS 7 do danas, sukladno s varijacijama morske razine. Osnovni čimbenik koji je utjecao na paleookolišni razvoj istraživanog prostora, uz morsku razinu, je dubina praga istraživanih depresija. Interpretacija paleookoliša zasnivala se na korelaciji s modernim analozima kasno-pleistocenskih i holocenskih paleookoliša, odnosno marinskim jezercima danas razvijenim u ponikvama na otoku Cresu.Sea level and climate changes enabled development of different paleoenvironments during the Late Quaternary in the present-day Lošinj Channel and coastal zone of Cres Island. Karst depressions in the investigated area are exceptional geomorphological features for preservation of thick sediment sequences. Therefore, paleoenvironmental reconstruction was based on the sediment cores. Analysis of 8 sediment cores was conducted using the multi-proxy approach and included determination of geochemical and mineralogical composition, grain-size, magnetic susceptibility measurements and organic carbon flux. Paleontological analysis (foraminifera, ostracods, mollusks, palynomorphs) facilitated the interpretation of obtained sediment core data. Core chronologies were based on 14C dating method. The high-resolution seismic data gave an additional insight into the thick sediment sequences preserved in the investigated depressions. The results indicated the exchange of marine and lacustrine or terrestrial environments since MIS 7, in accordance with the Quaternary sea level changes. The main factor that influenced the paleoenvironmental development of the area, except sea level, was the sill depth. The interpretation of paleoenvironments was based on correlation with the modern analogs of the Late Pleistocene and Holocene paleoenvironments, today present in the coastal zone of Cres Island

Active tectonics in the Kvarner region (External Dinarides, Croatia) – an alternative approach based on new focused geological mapping, 3D seismological and shallow seismic imaging data

Active tectonics in long-lived orogenic belts usually manifests on the preexisting inherited structures. In the Kvarner region of the External Dinarides, an area with low-to-moderate seismicity related to the Adriatic microplate (Adria) northward movement, we deal with faults in predominantly carbonate rocks within tectonically complex NW-SE striking foldand-thrust belt, which makes the identification and parametrization of the active structures challenging. Moreover, anthropogenic modifications greatly complicate access to the surface geological and geomorphological data. This paper demonstrates results of focused multidisciplinary research, from surface geological mapping and offshore shallow seismic surveys to earthquake focal mechanisms, as an active fault identification and parametrization kit, with a final goal to produce an acrossmethodological integrated model of the identified features in the future. Reverse, normal, and strike-slip orogen-parallel (longitudinal) to transverse faults were identified during geological mapping, but there is no clear evidence of their mutual relations and possible recent activity. The focal mechanisms calculated from the instrumental record include weak-to-moderate earthquakes and show solutions for all faulting types in the upper crust, compatible with the NE-SW oriented principal stress direction, with the stronger events favoring reverse and strike-slip faulting. The 3D spatial and temporal distribution of recent earthquake hypocenters indicate their clustering along predominantly subvertical transversal and steeply NE-dipping longitudinal planes. High-resolution shallow seismic geoacoustical survey (subbottom profiler) of the Quaternary sediments in the Rijeka Bay revealed local tectonic deformations of the stratified Late Pleistocene deposits that, along with overlaying mass-transport deposits, could imply prehistorical strong earthquake effects. Neotectonic faults onshore are tentatively recognized as highly fractured zones characterized by enhanced weathering, but there is no evidence for its recent activity. Thus, it seems that the active faults are blind and situated below the thin-skinned and highly deformed early-orogenic tectonic cover of the Adria. A strain accumulating deeper in the crust is probably irregularly redistributed near the surface along the preexisting fault network formed during the earlier phases of the Dinaric orogenesis. The results indicate a need for further multidisciplinary research that will contribute to a better seismic hazard assessment in the densely populated region that is also covered by strategic infrastructure

Late Quaternary Evolution of a Submerged Karst Basin Influenced by Active Tectonics (Koločep Bay, Croatia)

Koločep bay is a 30 km elongated karst basin located between the Elafiti Islands and the mainland with a NW–SE general direction. The bay lies within the seismically active southern Dalmatia zone. Irregular grid sub-bottom profiles and two legacy reflection seismic profiles have been used to determine the overall morphology of the bay and to establish the seismic stratigraphy of its sedimentary infill. Three major seismic–stratigraphic units have been identified in the upper ~50 m of the ~120-meter-thick sedimentary sequence that lies above the karstified limestone bedrock. The karst polje basin was flooded due to sea-level rise before 12.1 kyr BP. The morphology of the bay implies complex influences of Late Glacial meltwater discharges, aeolian sand deposition, the existence of paleo–ponor/karst spring zones and buried Pleistocene river channels. The Pleistocene seismotectonic units are deformed in the NW and SE parts of the basin. The central part of the basin has no signatures of intensive tectonic activity during the Holocene. A major erosion event was identified that led to the formation of a basin within the older sedimentary infill. In the southern part of the basin, we have evidence of Holocene tectonic activity with the formation of erosional scarps on the seafloor of the bay

SALTECTA – salt diapirs and active tectonics in the Central Adriatic

Srednji Jadran je predgorje dvaju orogenih sustava – Dinarida na sjeveroistoku i Apenina na jugozapadu. Osim velike debljine naslaga, to područje obilježava i specifična predgorska tektonika te brojne solne strukture. Te halokinetske strukture različito su prikazivane na objavljenim preglednim kartama i ilustracijama geoloških profila, a tek sporadično na interpretiranim seizmičkim profilima. Solni dijapiri čine impozantne potpovršinske strukture koje mjestimice izbijaju na površinu i tako utječu na morfologiju (batimetriju) tog područja. Solne strukture srednjeg Jadrana su znanstveno nedovoljno istražene, a nije istraživana niti uzročno-posljedična veza halokinetike i umjerene seizmičke aktivnosti koja obilježava to područje. Pretpostavlja se da je izdizanje soli vezano uz neotektonsku reaktivaciju mezozojskih rasjeda, od kojih su neki vjerojatno i danas aktivni. Projektom se namjeravaju interpretirati najnoviji 2D seizmički profili odobreni od strane Agencije za ugljikovodike (AZU), reinterpretirati gravimetrijski podatci, definirati glavni rasjedi te 3D modelirati geometrija odabranih solnih struktura. Strukturno-tektonski sklop (re)definirat će se na pučinskim otocima srednjeg Jadrana (slika 1). Uspoređivanjem prostornog rasporeda epicentara i hipocentara zabilježenih potresa s interpretiranim geološkim strukturama, pokušat će se razjasniti povezanost aktivne tektonike sa solnim strukturama. Istraživanjem i datiranjem najmlađih (kvartarnih) naslaga pokušat će se definirati neotektonska aktivnost solnih dijapira. Istraživanjem odabranih markantnih (sub)recentnih erozijskih oblika nastojat će se procijeniti prošla i buduća seizmotektonska aktivnost i seizmogeohazardi

Geological Modelling at the Croatian Geological Survey

Geological modeling at the Croatian Geological Survey is a developing discipline. In the past few years, a number of geological models were made, mostly for internal use, or as a training result for the ongoing projects, primarily GeoTwinn and Geosekva, while others were built for the purposes of scientific publication. This review will give several examples of selected geological models developed during the past few years period. It will also list different types of geological models and needed typical input data, and give a basic workflow for model building. Geological modeling requires acquisition of different spatial surface and subsurface input data, including primarily digital elevation model – DEM (or similar), different base maps, and other spatial data containing various geological information. Besides the resulting geological model, in the model building process, a whole series of resulting maps and other cartographic outputs are developed