U članku se prikazuju geomorfološka obilježja područja sjevernog Velebita s posebnim naglaskom na Nacionalni park Sjeverni Velebit. Temeljne morfometrijske i morfogenetske analize nekad rađene ...analogno, načinjene su korištenjem digitalnih tehnologija te nadopunjene novim analizama i terenskim radom. Od općih morfometrijskih metoda korištene su hipsometrija, analiza nagiba padina, analiza vertikalne raščlanjenosti
te ekspozicije padina. Morfogenetska analiza temelji se na specifičnim morfometrijskim te terenskim istraživanjima. U okviru morfogeneze analiziran je morfostrukturni reljef, a od egzogenih utjecaja najveća je pažnja posvećena krškim, glaciokrškim i fluviokrškim reljefnim oblicima.
Analiza krškog reljefa na području Nacionalnog parka Sjeverni Velebit, jednog od temeljnog fenomena Parka, pokazala je da je više od polovice njegove površine (50,66%) predstavljeno krškim depresijama (ponikve i uvale), što govori o izuzetno jakoj i
dugotrajnoj denudaciji. Uz krške procese, pojačanoj denudaciji značajno su pridonijeli glacijalni procesi koji su u vrijeme posljednjeg glacijalnog maksimuma znatno preoblikovali krške reljefne oblike i generalno utjecali na geomorfološku evoluciju Sjevernog Velebita.
Oledba Sjevernog Velebita, osim na krške reljefne oblike, utjecala je povremeno na intenziviranje fluvijalnih te postojanje limničkih procesa, stoga je poznavanje geomorfoloških obilježja Sjevernog Velebita i Nacionalnog parka Sjeverni Velebit od iznimnog značenja, kako za očuvanje georaznolikosti, tako i za njegovu daljnju turističku valorizaciju i promociju.
Glacial sediment is an important paleoclimatological and paleoenvironmental archive. In the Mediterranean region most of the Quaternary glaciers were hosted in carbonate mountains. Diagenetical ...processes in carbonate sediments tend to impact preservation of glacial features and complicate the establishment of accurate chronologies. This paper presents a sedimentological study of a paleoglacier hosted in the carbonate Velebit Mountain, Croatia. Three carbonate tills were studied in order to evaluate their depositional environments and the diagenetical processes that affect them. The tills were selected from lateral moraines of different glacial stages of the paleoglacier and they are interpreted as lodgement and melt-out tills. Diagenetical processes such as cementation, dissolution and increase in organic content were enhanced by the percolation of water through the sediment and the propagation of rootlets. This research demonstrates the importance of understanding the diagenetical processes affecting carbonate tills after their sedimentation. Studies like this are an essential research stage prior to conducting geochronological and paleoclimatological interpretations based on paleoglaciers in carbonate regions.
•Diagenesis of carbonate tills affects the original properties of glacial sediments.•Dissolution and formation of cements are common processes of early diagenesis.•Dating of carbonate tills by different methods is potentially impacted by diagenesis.
Mercury (Hg/TOC) spikes from eight Permian–Triassic boundary (PTB) sections in this study display patterns similar to each other across the so-called extinction interval as well as strong variation ...in sedimentation rates from section to section. Mercury may have been originated from the synchronous magmatism of the Siberian Traps Large Igneous Province (STLIP).
At the GSSP in Meishan, China, Hg/TOC peaks were observed in the latest Permian mass extinction interval (LPME) and Early Triassic mass extinctions (ETME). The successions at Hovea-3 (Australia), Ursula Creek (Canada), Idrijca (Slovenia), Rizvanuša (Croatia) exhibit Hg/TOC peaks at the LPME and PTB. The Rizvanuša section displays one peak at the ETME horizon, Zal and Abadeh (Iran) successions at the LPME and ETME horizons, while Misci/Seres (Tyrol/Italy) section shows an enrichment at the LPME. The largest Hg/TOC peaks at the LPME, PTB and ETME are, perhaps, linked to the beginning of stage 2 (extrusive hiatus) of the Siberian Traps LIP. The meaning of the Hg/TOC spike between the LPME event and the PTB in seven of these sections is fuzzy.
In the δ202Hg (MDF) vs Δ201Hg (MIF) cross plot, the majority of samples from the extinction interval appear within the volcanic-emission box and a few samples plot in the sediment/soil/peat box. Hg-isotope signatures resulted from mixing processes of volcanic and normal marine sediment Hg, generating four horizontal trends whose Δ201Hg shows negligible to no variation. Less terrigenous-Hg influx was noticed in the sections closer to the STLIP (Rizvanuša, Idrijca and Seres/Misci, all in Europe) in which Δ201Hg (MIF) is close to zero. Marked influence occurs in sections far distant from the STLIP (Meishan, Ursula Creek and Hovea-3) that exhibit negative Δ201Hg (MIF). The two sections from Iran, at intermediate distance from the STLIP, exhibit the highest, positive Δ201Hg values (Abadeh section) and the lowest, negative Δ201Hg values (Zal section). A Δ199Hg (MIF) vs Hg (n·ng−1) cross plot suggests that volcanic Hg has been contaminated by normal marine source-Hg influx in these sections helping to shape two major curved trends.
The negative C-isotope excursions and Hg/TOC enrichments in the studied sections are nearly coeval and this supports the hypothesis of synchronism between the Permian–Triassic transition biotic crises (LPME and ETME) and the start of the stage 2 of the Siberian Traps (sill-intrusion style of magmatism).
•Hg/TOC pathways across the extinction interval from eight PTB sections are similar.•Hg/TOC peaks at LPME, PTB and ETME are linked to stage 2 of Siberian Traps volcanism.•In δ202Hg vs Δ201Hg plot samples from the extinction interval plot in the volcanic box•Low terrigenous-Hg influx is noticed in sections closer to the STLIP.•High terrigenous-Hg influence occurs in sections far distant the STLIP.
Stable isotopes of carbonates (δ
13C
carb, δ
18O
carb), organic matter (δ
13C
org, δ
15N
org) and major, trace and rare earth element (REE) compositions of marine carbonate rocks of Late Permian to ...Early Triassic age were used to establish the position of the Permian–Triassic boundary (PTB) at two continuous sections in the Velebit Mountain, Croatia. The chosen sections — Rizvanuša and Brezimenjača — are composed of two lithostratigraphic units, the Upper Permian Transitional Dolomite and the overlying Sandy Dolomite. The contact between these units, characterized by the erosional features and sudden occurrence of ooids and siliciclastic grains, was previously considered as the chronostratigraphic PTB. The Sandy Dolomite is characterized by high content of non-carbonate material (up to ~
30
wt.% insoluble residue), originated from erosion of the uplifted hinterland. A relatively rich assemblage of Permian fossils (including
Geinitzina,
Globivalvulina,
Hemigordius, bioclasts of gastropods, ostracods and brachiopods) was found for the first time in Sandy Dolomite, 5
m above the lithologic boundary in the Rizvanuša section. A rather abrupt negative δ
13C
carb excursion in both sections appears in rocks showing no recognizable facies change within the Sandy Dolomite, −2‰ at Rizvanuša and −1.2‰ at Brezimenjača, 11
m and 0.2
m above the lithologic contact, respectively. This level within the lower part of the Sandy Dolomite is proposed as the chemostratigraphic PTB. In the Rizvanuša section, the δ
13C
org values decline gradually from ~
−25‰ in the Upper Permian to ~
−29‰ in the Lower Triassic. The first negative δ
13C
org excursion occurs above the lithologic contact, within the uppermost Permian deposits, and appears to be related to the input of terrigenous material. The release of isotopically light microbial soil-biomass into the shallow-marine water may explain this sudden decrease of δ
13C
org values below the PTB. This would support the hypothesis that in the western Tethyan realm the land extinction, triggering a sudden drop of woody vegetation and related land erosion, preceded the marine extinction. The relatively low δ
15N
org values at the Permian–Triassic (P–Tr) transition level, close to ≈
0‰, and a secondary negative δ
13C
org excursion of −0.5‰ point to significant terrestrial input and primary contribution of cyanobacteria. The profiles of the concentrations of redox-sensitive elements (Ce, Mn, Fe, V), biogenic or biogenic-scavenged elements (P, Ba, Zn, V), Ce/Ce* values, and normalized trace elements, including Ba/Al, Ba/Fe, Ti/Al, Al/(Al
+
Fe
+
Mn) and Mn/Ti show clear excursions at the Transitional Dolomite–Sandy Dolomite lithologic boundary and the chemostratigraphic P–Tr boundary. The stratigraphic variations indicate a major regression phase marking the lithologic boundary, transgressive phases in the latest Permian and a gradual change into shallow/stagnant anoxic marine environment towards the P–Tr boundary level and during the earliest Triassic.
►Biogeochemical study of two sections across the Permian–Triassic boundary (PTB) in Croatia. ►A negative δ13Ccarb excursion in both sections appears in rocks showing no facies change. ►The chemostratigraphic excursions are compared with data from PTB sections worldwide. ►The results of this study are consistent with the development of water column anoxia–euxinia. ►This study filled a gap in the knowledge on the PTB in Croatia and wider region of SE Europe.
Comprehensive glacial Quaternary studies involving geochronological methods, modelling of ice topography with the support of field geomorphological and geological data in the Balkan Peninsula are ...relatively scarce, although there is evidence of past glaciations in several mountain ranges. Here, we present research on the extent and timing of past glaciations on the northern Velebit Mt. in coastal Croatia and inferences of the climate during that time. Based on geomorphological and sedimentological evidence and using cosmogenic 36Cl surface exposure dating of moraine boulders, we provide an empirical reconstruction of past glaciers and compare this with the Parallel Ice Sheet Model (PISM) simulations under different palaeoclimate forcings. The dating results show that the northern Velebit glaciers reached their maximum extent during the last glacial cycle before the global Last Glacial Maximum (LGM). Maximum ice extent likely correlates with Marine Isotope Stage 5–4, although the exact timing cannot be determined at this point due to poorly known site- and time-specific denudation rates. Empirical reconstruction of the maximum extent suggests that the area covered by glaciers was ~116 km2. The-best fit PISM simulation indicates that the most likely palaeoclimate scenario for the glaciers of this size to form is a cooling of ~8 °C and a 10% reduction in precipitation from present-day levels. However, the best-fit simulation does not correctly model all mapped ice margins when changes in climatological parameters are applied uniformly across the model domain, potentially reflecting a different palaeoprecipitation pattern to today.
•The Northern Velebit glaciers reached their maximum extent before the global LGM.•The minimum moraine ages are 16.5 ± 1.6 ka, 52.6 ± 9.3 ka, 57.0 ± 11.0 ka and 94.0 ± 24.0 ka.•The maximum ice limit likely correlates with MIS 5–4.•The palaeoclimate was ~8 °C colder and ~10% drier than today.
Mljekarstvo, a osobito proizvodnja fermentiranih mliječnih proizvoda, strategije su uzgoja stoke koje često uključuju sezonska kretanja stada. Nedavno objavljene kemijske analize tragova na posuđu i ...analiza izotopa kisika na zubima ovikaprida pokazuju da su stočari iz sjevernodalmatinskog priobalja počeli svoja stada ljeti izdizati na planinske pašnjake u drugoj polovici 6. tisućljeća pr. Kr., otprilike u isto vrijeme kada su počeli proizvoditi sir. Rezultate tih istraživanja, provedenih na građi iz nizinskih neolitičkih sela, podupire i nadopunjuje raspoloživa arheološka građa iz nalazišta smještenih visoko na Velebitu. Sezonsko vertikalno kretanje pastira započelo je sredinom 6. tisućljeća pr. Kr., oko pet stoljeća nakon prve pojave zemljoradnje u sjevernoj Dalmaciji. Promjena strategije gospodarenja stadom vremenski se podudara s drugim promjenama koje upućuju na intenziviranje strategija preživljavanja. Širenje zemljoradnje u Liku možda je izravno povezano s početkom transhumantnog stočarstva.
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