Sulfur and oxygen isotopes in the gypsum deposits of the Provalata sulfuric acid cave (Macedonia)

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Geo-values of the natural monument Markovi Kuli near Prilep

Located on the southwestern branches of Babuna Mountain, north of Prilep in North Macedonia is the Natural Monument Markovi Kuli – a geosite with an exceptional weathering landscape. It is a host to a vast variety of weathering landforms (boulders, pillars, weathering pits, tafoni, etc.), mainly due to the lithology where Proterozoic gneiss rocks are intruded by Late Paleozoic granitic rocks. In addition, landform development is also controlled by the local climate conditions. As a result of its geomorphological significance, in 2004 Markovi Kuli geosite was placed on the tentative list of UNESCO World Heritage, and in 2006 it was proclaimed as a Natural Monument, within the network of protected areas in Macedonia. However, despite its geodiversity being the cornerstone of its significance, not many geomorphological studies have been made so far. Considering that, and especially the necessity for the effective protection of the area, the results of the latest research are presented in this work

A cave response to environmental changes in the Late Pleistocene: a study of Budimirica Cave sediments, Macedonia

Budimirica Cave is a small cave located in the southern part of the Republic of Macedonia, inthe Kamenica Valley, a tributary to the Crna Reka and part of the Vardar river drainage network.The response of the cave to Late Pleistocene environmental changes is interpreted based on adetailed study of cave sediments, with previous data being supplemented, reinterpreted andcompared to the Ohrid Lake palaeoclimate record. The oldest exposed speleothems in the Budimiricasediment profile were deposited during the MIS 5a (radiometric age of ca 83 ka). Sandsto clays in the overburden are characterized by cycles separated by short-lived interruptions indeposition. They were deposited from a number of repeated flood events likely during the MIS4 stage, the Weichselian (Wurmian) Glaciation, correlating to aggradation in the Kamenica Valley.The top flowstone is correlated with a warmer climate excursion at 45–50 ka (MIS 3) recordedfrom the Ohrid Lake deposits. The whole section was extensively eroded during the MIS 2stage, due to strong incision in the Kamenica Valley, indicated by knickpoint retreat. The erosionsurface is overlain by a fossil-bearing breccia (with Ursus spelaeus) derived from frost shatteringof the cave walls close to the entrance due to climate deterioration and enlargement of theentrance by slope retreat during the MIS 2 stage. Budimirica Cave sediments reflect changes inthe Kamenica Valley, as well as the environmental changes during the last glacial-interglacialcycle, with clastic cave sediments deposited during glacial stadials, and erosion and flowstonedeposition characteristic of the interstadials. They also allow reconstruction of the evolution ofthe Kamenica Valley during the Late Pleistocene, with a general trend of valley incision hinderedby climate influenced river aggradation, but reinforced by river knickpoint retreat.</p

Rainwater Isotopic Composition in the Ecuadorian Andes and Amazon Reflects Cross-Equatorial Flow Seasonality

The variability of the rainfall stable isotopic values (δ2Hp, δ18Op) in the Ecuadorian Amazon to the Andes presents a marked local “altitude” effect. At the same time, this complex orography creates diverse precipitation regimes (unimodal, bimodal, and three-modal) that make it difficult to establish a relationship with the local amount. Nevertheless, stations along these regions show a similar intra-annual isotopic variability, with lower values during MAM and ON. In contrast, higher values are found during DJF and JAS in a w-shaped pattern, suggesting a common regional controller. A monthly δ2Hp and δ18Op collection campaign was established in Central Ecuador (n = 30) to complement stations biased towards the northern and southern parts. Based on back trajectory analysis, the results demonstrated that moisture arrives from two primary sources: the Tropical North Atlantic (DJFM) and the Amazon Basin (JAS). Nevertheless, their convergence (AMJ and ON) is the crucial factor modulating the lowest isotopic values. Precisely, this convergence is stronger at the V-Index region (5° S–5° N, 65°–75° W), where the wind seasonality and reversal at low levels are enhanced, allowing the inter-hemispheric moisture flux transport (cross-equatorial flow). We propose that the amount of rainfall located at the V-Index region is a more robust approach for explaining the δ2Hp and δ18Op variability rather than the local amount

Late Pleistocene glacial advances, equilibrium-line altitude changes and paleoclimate in the Jakupica Mts (North Macedonia)

In the Jakupica Mts a plateau glacier was reconstructed (max. area ~45 km2, max thickness: ~260 m). The study area comprises six formerly glaciated valleys, five of which were fed by the plateau glacier and one had an independent cirque when local glaciation reached its maximum ice extent (MIE). The equilibrium line altitude (ELA) of the most extended glacial phase was at 2075+37/-25 m asl. The 10Be cosmic ray exposure (CRE) age of this phase was estimated at 19.3+1.7/-1.3 ka, conformable with the Last Glacial Maximum (LGM). CRE ages from the next moraine generation placed the first phase of deglaciation to 18.2+1.0/-3.0 ka. The samples from the moraine of the penultimate deglaciation phase provided CRE ages with large scatter and biased towards old ages, which is probably the result of inherited cosmogenic nuclide concentrations within the rock. Glacio-climatological modelling was performed for the MIE, which has a well-established LGM age. The degree-day model was used to calculate the amount of accumulation required to sustain the glaciological equilibrium assuming a certain temperature drop at the ELA. The degree-day model constrained by the pollen- based July paleo-temperature reconstructions yielded an annual total melt at the LGM ELA comparable to or slightly higher than the current mean annual precipitation at the same elevation. These wetter LGM conditions inferred from the paleo-glaciological evidence in Jakupica Mts suggest an enhanced moisture advection in the region

Preliminary geochemical characterization of gas manifestations in North Macedonia

L ike most of the Balkan Peninsula, North Macedonia is a geodynamically active area. As such it has many hydrothermal features and gas manifestations. Until now, no systematic study about the geochemical characterization of the geogenic gases was made before in this country. In August 2019, 24 gas samples were collected in the study area. All, except one collected at Duvalo (soil gas), are gases bubbling or dissolved in thermomineral waters (temperatures from 12 to 66 \ub0C). They were analysed in the laboratory for their chemical (He, Ne, Ar, O2 , N2 , H2 , H2S, CH4 and CO2) and isotopic composition (\u3b413C-CO2, \u3b413C-CH4, \u3b42H-CH4 and R/RA). Most of the gases have CO2 as the main component (400-998,000 ppm) while the remaining are enriched in N2 (1300-950,000 ppm). Helium ranges from 0.3 to 2560 ppm while CH4 from 1.6 to 20,200 ppm. R/RA and 4He/20Ne ratios indicate a generally low atmospheric contamination, a prevailing crustal contribution and mantle contributions between 1 and 20% considering a MORB endmember. The highest mantle contributions are found in the SE part of the country very close to the sites that show the highest R/RA values in continental Greece [1]. This area is characterised by extensional tectonics and Plio- Pleistocene volcanism. A quite high mantle contribution (about 15%) is also found in two manifestations in the NW part of the country along a main normal fault system. With the exception of the sample of Smokvica, which has very low CO2 (1400 ppm) and \u3b413C-CO2 (-15.7 \u2030 V-PDB), all free gases show a relatively narrow range in \u3b413C-CO2 values (-4.6 to +1.0 \u2030 V-PDB) indicating the mixing between a mantle and a carbonate rock source. The isotope composition allows us to assign the CH4 origin to three sources. The largest group can be attributed to a hydrothermal origin (\u3b413C-CH4 around -20 \u2030 V-PDB and \u3b42H-CH4 around -100\u2030). Three samples collected in the SW part of the country have a thermogenic origin (\u3b413C-CH4 around -35 \u2030 V-PDB and \u3b42H-CH4 around -160\u2030 V-SMOW). Finally, one sample (Smokvica) with the highest values (\u3b413C-CH4 -7.2 \u2030 V-PDB and \u3b42H-CH4 -80\u2030 V-SMOW) may be attributed to abiotic processes in a continental serpentinization environment or to methane oxidation

Duvalo (North Macedonia): A "volcano" without volcanic activity

T he Duvalo locality is located in the SW of the Republic of North Macedonia, in the Ohrid region, near the village of Kosel. It is an area of strong soil degassing, called “volcano” by the local people despite volcanic activity has never been documented in the recent geologic history of the area [1]. A large area (thousands of sqm) shows signs of strong alteration and is devoid of vegetation. Until the 19thcentury sulphur was mined from this area [1]. In August 2019, a campaign of soil CO2 flux measurements and soil gas sampling was made. Duvalo is sometimes referred to as an active geothermal feature but no signs of enhanced geothermal gradient were found and the soil temperatures at 50 cm depth in this campaign were always within the range of local mean air temperatures. Soil CO2 flux values ranged from 1.3 to 59,000 g/m2/d and can be modelled with the overlapping of 3 or 4 flux populations. A possible biological background is estimated in 6.8±1.8 g/m2/d while the other populations are characterized by an anomalous average flux ranging from 180 to 33,000 g/m2/d. The CO2 total emission, estimated both with a statistical and geostatistical approach, provided similar values in the order of 50 t/d. This has to be considered as a minimum value because only areas with evident signs of alteration have been investigated. Nevertheless, the estimated output is quite high for an area unrelated with recent volcanism or geothermal activity. The chemical composition of soil gases shows: CO2 (96.6%), N2 (1.8%), H2S (0.6%) and CH4 (0.3%) as the main gases. The present composition is almost indistinguishable from previous analyses made in 1957 and 1977 [1] pointing to a stability of the system in last decades. The isotope compositions indicate for CO2 (δ13C -0.2 ‰) a pure carbonate rock origin, for CH4 (δ13C -34.4 ‰ and δ2H -166 ‰) a thermogenic origin and for He (R/RA 0.10) a pure crustal origin. The H2S released at Duvalo may be produced by either microbial or thermochemical sulphate reduction favoured by hydrocarbons whose presence can be inferred by the uprise of thermogenic methane. Partial oxidation of H2S during its upflow, producing sulphuric acid, may be responsible of the production of abundant CO2 through dissolution of carbonate rocks. Similar processes have been evidenced also in other parts of North Macedonia [2]. These gases rise up through the N–S trending normal faults bordering the seismically active Ohrid basin graben [3] being released to the atmosphere through the soils of Duvalo “volcano”

Combined use of conventional and clumped carbonate stable isotopes to identify hydrothermal isotopic alteration in cave walls

Alteration of conventional carbonate stable isotopes (δ 18 O, δ13 C) in cave walls has been shown to be a useful tool to identify cave formation driven by deep-seated processes, i.e., hypogene karstification. If combined with a prior information on the paleowater stable isotope composition, further insights can be obtained on the temperature and the source of the paleowater. Clumped isotope composition (Δ 47 ) of carbonates is an independent measurement of temperature, and if combined with the conventional stable isotopes, can provide information on the paleowater stable isotope composition. On the example of Provalata Cave (N. Macedonia), we apply for the first time, both conventional and clumped stable isotope analysis, and identify two different isotope alteration trends, reflecting two distinct hydrothermal events: an older, hotter one, where isotope alteration was likely related to isotope diffusion, lowering the δ 18 O values of the carbonate; and a younger one, related to the cave formation by low-temperature CO 2 -rich thermal waters, with dissolution-reprecipitation as the alteration mechanism, causing decrease in δ 18 O values, and unexpected increase in δ 13 C values. The findings are further corroborated by additional insight from optical petrography and cathodoluminescence microscopy, as well as fluid inclusion analysis of secondary calcite crystals related to the cave forming phase