Hasil untuk "Stratigraphy"

Zhiyuan Li, Xinsong Wu, Zhilong Huang et al.

Abstract The previous studies on coal-measure tight sandstone reservoirs often focused on the single diagenetic evolution and pore structure characterization. The understanding of reservoir evolution under the comprehensive control of the sedimentary–diagenetic process was insufficient. In this paper, the coal-measure tight sandstone reservoir evolution mechanism under the control of the depositional–diagenetic process is studied through sequence stratigraphy, sedimentology, petrology, mineralogy, and geochemistry analysis. The study found that during the depositional process of coal-bearing strata, there were differences in sedimentary environments, sand body types, and coal-mud-sand combinations in different sedimentary stages. These differences result in different diagenetic evolution processes and ultimately different reservoir qualities. In general, the coal-bearing strata underwent a depositional evolution process from the lowstand filling stage to the lacustrine transgressive-maximum flooding stage, and finally highstand filling stage. In this process, sand-coal-mud combinations of thick coal-mud covering thick sand, thick coal-mud thin sand, and thick sand thin coal-mud are formed. The sedimentary environment and coal-mud-sand combination control the type and content of carbonate cement. In the rapid lacustrine transgressive-maximum flooding stage, with a reducing-high salinity sedimentary environment, strong organic matter fermentation leads to the production of large amounts of CO2 and reducing metal cations. It is conducive to the formation of a large number of early carbonate cements (siderite and ankerite). And the fluids and substances often migrate from the thick coal seam to the underlying thick lowstand filling sandstone. That is the reason why carbonate cement of lowstand filling sandstone is dominated by siderite and ankerite. In the highstand filling stage, with an oxidized-low salinity sedimentary environment, ferro calcite is the main carbonate cement in tight sandstone. Overall, the lacustrine transgressive-maximum flooding sandstone has a fine grain size and low content of rigid minerals, resulting in strong compaction and weak dissolution. And there is a large amount of siderite and ankerite developed. The reservoir quality is poor. Sandstones in lowstand and highstand filling stages have a coarse grain size and high content of rigid minerals, resulting in good pore preservation and strong dissolution. The reservoir quality is good. Siderite and ankerite are developed in reservoirs of lowstand filling stage. Due to the dissolution of early carbonate cements, its pores are particularly well preserved.

Á. Gamisel-Muzás, Á. Gamisel-Muzás, R. Soto et al.

<p>The major goal of this work is to provide insight into the structural and geological anatomy of the Pyrenees based on the magnetic anomalies and inferred lineaments from Earth Magnetic Anomaly Grid 2 arcmin resolution (EMAG2v2) magnetic data. We focus on providing qualitative and semi-quantitative evidence of the magnetic signature of the Pyrenees mountain range domains and structures. The integration of reduced-to-the-pole and processed maps, as well as the Bouguer anomaly map with geological data, has proved to be significantly useful in order to shed light on the main anomaly sources. Considering their magnetic response and texture, several anomalies can be linked to buried geological bodies or changes in the magnetic character of the basement. We have estimated their source bodies' depth through Euler and power spectrum calculations.</p> <p>We have identified and confirmed eight magnetic zones with different features and interpreted them in terms of the geological and structural setting of the area: one on the Aquitaine Basin with the highest magnetic response in the area, linked to the Sub-Pyrenean Thrust; three along the North Pyrenean Zone linked to mantle materials; one to the east of the Axial Zone representing the boundary between the Pyrenean mountain range and the Mediterranean Sea; two more located in the Catalan Coastal Range related to the volcanic fields in the area; and one in the Gulf of Lyon caused by a thicker crustal block. The result is an overall interpretation of the Pyrenees main magnetic domains.</p>

Degterev, Artem V., Romanyuk, Fedor A.

Preliminary results of field surveys (July 2025) of the ultra-acid sulfate-chloride thermal springs of the " Blue Lakes" which discharge in the Kipyashchiy Stream valley on the slope of the active Baransky volcano (Iturup Island, Southern Kuril Islands), are presented.

O. A. Lutikov

Niklas Hohmann, Joël R. Koelewijn, Peter Burgess et al.

Abstract Background The fossil record provides the unique opportunity to observe evolution over millions of years, but is known to be incomplete. While incompleteness varies spatially and is hard to estimate for empirical sections, computer simulations of geological processes can be used to examine the effects of the incompleteness in silico. We combine simulations of different modes of evolution (stasis, (un)biased random walks) with deposition of carbonate platforms strata to examine how well the mode of evolution can be recovered from fossil time series, and how test results vary between different positions in the carbonate platform and multiple stratigraphic architectures generated by different sea level curves. Results Stratigraphic architecture and position along an onshore-offshore gradient has only a small influence on the mode of evolution recovered by statistical tests. For simulations of random walks, support for the correct mode decreases with time series length. Visual examination of trait evolution in lineages shows that rather than stratigraphic incompleteness, maximum hiatus duration determines how much fossil time series differ from the original evolutionary process. Gradual directional evolution is more susceptible to stratigraphic effects, turning it into punctuated evolution. In contrast, stasis remains unaffected. Conclusions • Fossil time series favor the recognition of both stasis and complex, punctuated modes of evolution. • Not stratigraphic incompleteness, but the presence of rare, prolonged gaps has the largest effect on trait evolution. This suggests that incomplete sections with regular hiatus frequency and durations can potentially preserve evolutionary history without major biases. Understanding external controls on stratigraphic architectures such as sea level fluctuations is crucial for distinguishing between stratigraphic effects and genuine evolutionary process.

Tatina Blyakharchuk, Nikita Shefer, Olga Ponomareva et al.

West Siberian mires covering more than 50% of area in the subarctic are still poorly investigated despite their thick peat sediments suitable for paleogeographic research of past long-term landscape and climatic changes. In this research, a combination of paleoecological methods were used, including the analysis of pollen, spores, diatoms, NPPs, and macrofossils, the measurement of peat humification, and quantitative paleoclimate reconstruction. This multi-proxy approach was applied to study a palsa bog (frost peat heave mound) located in the north of western Siberia on the border of the northern taiga and forest–tundra (65°18′56″ N, 72°52′27″ E). Chronology is based on 21 radiocarbon dates, which were calibrated in CLAM. Studies have shown that sediments of palsa bog Nadym of a 1050 cm thickness were formed both in the Holocene and earlier periods of the Quaternary. Radiocarbon dating worked well for peat sequences (610 cm thick), but failed for underlying lacustrine and mineral sediments (440 cm thick). Numerous remains of salt-water diatoms and exotic Neogene pollen were found in the lacustrine sediments (650–850 cm). The oldest sediments (850–1050 cm) have signs of secondary epicryogenic diagenesis in the form of cryogenic iron-enriched granules. Both lacustrine and bottom sediments contain abundant coniferous pollen. At the same time, spore–pollen complexes dated to the Last Glacial Age were not found in low sediments because of failed dates. To explain this, the authors turn to the hypothesis of glyacioisostatic compensation, according to which the study area was uplifted during the Last Glacial Age and the ancient deposits underwent secondary diagenesis in subaerial conditions. Holocene lacustrine sedimentation began to form about 9800 cal. a BP. These lacustrine sediments turned out to be enriched in redeposited Neogene pollen and diatoms. It was interpreted as an influence of excess humid climate in combination with geological subsidence of landscape in the study area during the Early Holocene. This caused lake formation and introduction of exotic microfossils via surface run-off from higher-relief areas in the catchment. Syngenetic sedimentation in the Nadym section is associated only with peat-mire deposits covering the last 8400 cal. a BP. For this time, the dynamic of vegetation cover and quantitative changes in paleoclimate were reconstructed using spore–pollen, macrofossil, humus, and NPP data as well as the information–statistical method of V.A. Klimanov. The spore–pollen analysis revealed four main phases in the development of vegetation cover: 1. Spruce–birch forests with open meadows and lakes (8400–7600 cal. a BP); 2. Dominance of spruce forests and thawed eutrophic (minerotrophic) mires (7600 to 6500 cal. a BP); 3. Coniferous–birch forests and thawed mesotrophic mires (6500 to 4500 cal. a BP); 4. Birch–pine forests and oligotrophic (ombrotrophic) bogs with permafrost mounds—palsa bogs (approx. the last 4500 years). Quantitative reconstructions of paleoclimate based on pollen data show that in most cases the periods of a sharp decrease in mean January and mean July temperatures coincided with episodes of low solar activity. The assumption was made about the determining influence of solar activity on the formation of permafrost in the soils and mires of the study area. Sun minima caused permafrost formation in the mire periodically since 8400 cal. a BP in study peatland, but complete freezing of the peat mire and formation of the palsa bog occurred at c. 2800 cal. a BP.

M. Evain, P. Schnürle, A. Leprêtre et al.

<p>Coincident wide-angle and multi-channel seismic data acquired within the scope of the PAMELA Moz3-5 project allow us to reconsider the formation mechanism of East African margins offshore of southern Mozambique. This study specifically focuses on the sedimentary and deep-crustal architecture of the Limpopo margin (LM) that fringes the eastern edge of the Mozambique’s Coastal Plain (MCP) and its offshore southern prolongation the North Natal Valley (NNV). It relies primarily on the MZ3 profile that runs obliquely from the northeastern NNV towards the Mozambique basin (MB) with additional inputs from a tectonostratigraphy analysis of industrial onshore–offshore seismic lines and nearby or crossing velocity models from companion studies. Over its entire N–S extension the LM appears segmented into (1) a western domain that shows the progressive eastward crustal thinning and termination of the MCP/NNV continental crust and its overlying pre-Neocomian volcano-sedimentary basement and (2) a central corridor of anomalous crust bounded to the east by the Mozambique fracture zone (MFZ) and the oceanic crust of the MB. A prominent basement high marks the boundary between these two domains. Its development was most probably controlled by a steep and deeply rooted fault, i.e., the Limpopo fault. We infer that strike-slip or slightly transtensional rifting occurred along the LM and was accommodated along this Limpopo fault. At depth we propose that ductile shearing was responsible for the thinning of the continental crust and an oceanward flow of lower crustal material. This process was accompanied by intense magmatism that extruded to form the volcanic basement and gave the corridor its peculiar structure and mixed nature. The whole region remained at a relative high level during the rifting period and a shallow marine environment dominated the pre-Neocomian period during the early phase of continent–ocean interaction. It is only some time after break-up in the MB and the initiation of the MFZ that decoupling occurred between the MCP/NNV and the corridor, allowing for the latter to subside and become covered by deep marine sediments. A scenario for the early evolution and formation of the LM is proposed taking into account both recent kinematic and geological constraints. It implies that no or little change in extensional direction occurred between the intra-continental rifting and subsequent phase of continent–ocean interaction.</p>

I. Lior, I. Lior, A. Sladen et al.

<p>The use of distributed acoustic sensing (DAS) presents unique advantages for earthquake monitoring compared with standard seismic networks: spatially dense measurements adapted for harsh environments and designed for remote operation. However, the ability to determine earthquake source parameters using DAS is yet to be fully established. In particular, resolving the magnitude and stress drop is a fundamental objective for seismic monitoring and earthquake early warning. To apply existing methods for source parameter estimation to DAS signals, they must first be converted from strain to ground motions. This conversion can be achieved using the waves' apparent phase velocity, which varies for different seismic phases ranging from fast body waves to slow surface and scattered waves. To facilitate this conversion and improve its reliability, an algorithm for slowness determination is presented, based on the local slant-stack transform. This approach yields a unique slowness value at each time instance of a DAS time series. The ability to convert strain-rate signals to ground accelerations is validated using simulated data and applied to several earthquakes recorded by dark fibers of three ocean-bottom telecommunication cables in the Mediterranean Sea. The conversion emphasizes fast body waves compared to slow scattered waves and ambient noise and is robust even in the presence of correlated noise and varying wave propagation directions. Good agreement is found between source parameters determined using converted DAS waveforms and on-land seismometers for both P and S wave records. The demonstrated ability to resolve source parameters using P waves on horizontal ocean-bottom fibers is key for the implementation of DAS-based earthquake early warning, which will significantly improve hazard mitigation capabilities for offshore earthquakes, including those capable of generating tsunami.</p>

Olivier Blarquez, Julie Aleman

Coring lakes and water bodies for paleoecological studies often involves using a coring platform to properly operate a sediment sampling device. In the past, coring platforms have been developed by specific paleoecology laboratories or by private companies. Those coring platforms are generally composed of two boats (inflatable boats, kayaks, etc.) connected together by a metallic and wood structure. While these coring platforms have proven their efficacy, they are not ideal in several coring settings requiring remote transportation, and their cost may be prohibitive for less funded paleoecological laboratories. On this technical note, we describe the Light, Affordable, Stable, and Transportable (LAST) coring platform. Coring platforms based on these principles and on the design presented herein have been extensively tested in various conditions and countries by our research group and collaborators. In the first part of this manuscript, we present the principles and the design of the LAST coring platform; then, we discuss the coring setting for which the LAST coring platform is suitable, and its possible limitations. Associated with this manuscript, we provide a construction and assemblage manual developed without words and with simple illustrations in order to make it easily accessible to speakers of any language.

Zeinab Najafi, Golam Hosein Karami, Haji Karimi

Abstract In karstification phenomenon of carbonate formations various factors are involved which the most important of them are lithology, precipitation, stratigraphic characteristics, structural factors and the topography of the region. Thick and massive limestones have much higher potential for the development of karst and, as a result, the formation of karst features. In this research, four important karstic springs have been investigated, the name of these springs are Ravansar, Kabotarlaneh, Sahneh and Kashanbeh. The catchment areas of these springs are located in the different geological formations with various lithologies and ages. The discharge of springs and its variability depends significantly on the lithology of the aforementioned formations. The average annual discharge of the Ravansar, Darband Sahneh, Kashanbeh, and Kabotarlaneh springs in the hydrological year 2016–2017 is 1932, 462, 166 and 771 lit/s, respectively. Moreover, the coefficients of variation of these karst springs are 1.07, 0.30, 0.49 and 0.48 and the maximum to minimum ratio of these springs were calculated 20, 2, 7 and 4, respectively. The Ravansar and Kabotarlaneh springs have three discharge coefficients, while the springs of the Sahneh and Kashanbeh have two, which are related to stratigraphy and lithology of their basins. The largest of the aquifer storage from these springs is dedicated to the Ravansar spring, and the smallest is Kashanbeh; the discharge of these springs also confirms it. Keyword: Stratigraphy, Karst Development, Karst spring, Kermanshah   Introduction: ‘‘Karst’’ refers to terrain with distinctive landforms and a largely subsurface drainage system, arising from the high solubility of certain rocks in natural waters (Karami 2002). Although karstic areas mainly develop on carbonate rocks (limestone in particular), they are not limited to these rocks and can also develop on other soluble rocks (e.g. gypsum, anhydrite, and halite). Several factors are involved in karst development, the karst development is mainly controlled by lithology, precipitation, stratigraphic, characteristics of structural factors and the topography of the area. Among them, the lithology and stratigraphic characteristics of carbonaceous formations are of particular importance. Thick and massive carbonate rocks have a higher degree of karst development and, as a result, more obvious karstic features. There are many karst springs (that is called “Sarab” in the local lingo) in Kermanshah province (more than 200 springs). The mean annual discharge of these springs is relatively considerable (the average annual discharge some of them is up to 3000 lit/s). In this study, karstic springs have been selected from different regions of the province and their characteristics related to the stratigraphy of spring's basin have been studied. The purpose of this study is to investigate the stratigraphic role of different formations on discharge fluctuations of the selected springs in the study area.   Material & Methods: For achieving the aim of this research as the initial evaluation, geological maps in the area were concerned and then springs were selected whose catchment area are located in different carbonate formations or have different lithologies status. In the fieldwork electrical conductivity and water temperature of springs has been measured. Spring's water was sampled monthly during a water year (2016–2017) and concentration of major ions of samples was determined in the hydrology laboratory of the Shahrood University of Technology by titration method, then the results were randomly re-measured at the Freie Universität Berlin (FUB) by ion chromatography, which showed high precision results. After following the steps mentioned above estimating recharge potential zone in the study area was estimated and the catchment area of the springs was determined. Finally, the effect of various stratigraphy on karst development and variability of karst springs discharges and groundwater flow in karst aquifers was investigated.   Discussion of Results & Conclusions The role of stratigraphy in karst aquifers is very important and plays a major role in karst development and the creation of various conduits and dissolution spaces in the aquifer of springs. This theme is well visible in the evaluation of the four springs of Ravansar, Kabotarlaneh, Darband, and Kashanbeh. Ravansar spring's basin due to the Bistoon Formation has high karst development and consequently high fluctuations in discharge, electrical conductivity, and temperature. Many studies have been carried out to determine the flow type and thickness dynamics of a karstic aquifer, mainly evaluating the physical and chemical properties of springs. Changes in the physical and chemical properties of the water of the selected springs are different and are influenced by the stratigraphy and geological characteristics of the catchment basins of these springs. The discharge coefficients and variations of the measured parameters for Ravansar spring indicate that conduit flow system is dominant in karst aquifer feeding this spring. According to the characteristics of the Kabotarleneh spring, the conduit system in its aquifer has become less developed in comparison to the Ravansar spring which is related to its different stratigraphy. The characteristics of catchment areas of the Darband are similar to the Kabotarlaneh spring, which has caused the flow system of the Darband spring to be similar to the Kabotarleneh spring. According to characteristics of Kashanbeh Springs, it has a diffuse-conduit flow system.

Chris Adesola Samakinde, Jan Marinus Van Bever Donker, Ray Durrheim et al.

Abstract The Barremian-Cenozoic depositional sequences in the northern Orange Basin, SW, South Africa, were investigated using the principles of seismic stratigraphy to understand the interplay of tectonics and sedimentary processes in the distribution of potential hydrocarbon reservoirs. A seismic stratigraphic workflow (seismic sequence, seismic facies and lithofacies analysis) was completed by utilising three seismic lines (L1, L2 and L3) tied to Wireline data (gamma, checkshots and sonic) in two exploration wells (A1 and A2). Seven depositional sequences were mapped followed by the creation of lithofacies log interpreted from the gamma-ray log (GR) by setting maximum GR value at 60 API for Sandstone, 60–100 API for Siltstone and above 100 API for Shale. Six seismic facies units are recognised based on internal geometry and configurations of the seismic reflectors; Tangential-Oblique (SF1), Hummocky (SF2), Wavy-Parallel (SF3), Chaotic (SF4), Sub-parallel/parallel (SF5) and Divergent (SF6). SF4 is dominant within the Barremian-Aptian sequence and expressed in an incised valley fill, suggesting mass transport deposition accompanied by strong hydrodynamic conditions. Evidence of sedimentary basins progradation is seen within the Late-Albian-Turonian sequences, because of the occurrences of SF2, SF6 and SF 4 facies. SF5 facies is prominent in the Maastrichtian/Campanian sequence, indicating that the deposition of sediments may have been accompanied by uniform margin subsidence after the Late-Cretaceous uplift of the Africa margin. The occurrence of SF1 and SF4 facies within the Cenozoic sequence indicates terrigenous pro-deltaic deposits and mass transport deposits, respectively. Further results from seismic-lithofacies modelling reveal that sand deposits of Barremian-Aptian (SF4 facies unit) and Albian sequences (SF2 and SF6 facies units) are potential stratigraphic reservoirs in this part of the basin.

Jean M. Philip, Jean Pierre Platel

A cartographic and stratigraphic study of the Upper Cretaceous series surrounding the Haushi-Huqf massif (easter Oman) has allowed to subdivide it into lithostratigraphic formations and to refine their chronostratigraphic age… in order to continue, download the full paper in PDF.

Iannace Pietro, Torrente Maurizio M., Milia Alfonsa

The Southern Campania Margin (SCM) represents a key area of the Central Mediterranean because it records all the rifting stages of the Tyrrhenian Sea. The interpretation of a seismic dataset calibrated with deep wells and outcrops, using seismic stratigraphy and structural geology methods in a dedicated Geographic Information System (GIS) environment, the seismic depth conversion, the generation of 2-D and 3-D models led to the reconstruction of a polyphased tectono-stratigraphic evolution of the SCM. During the early stage of Tyrrhenian opening a terrigenous transtensional Basin (Langhian-Tortonian Cilento Basin) formed on the Liguride accretionary prism adjacent to the Calabria crystalline terrane. In the SCM the Liguride thrust sheets tectonically overly the Apennine Platform units and both these nappes have been dismembered by Quaternary faults. Three rifting stages, not homogeneously distributed, affected the region since the Lower Pleistocene. They are associated to the deposition of a thick Quaternary succession (A, B and C units). During these Pleistocene stages there was an abrupt change of the extension direction (from NE-SW to NW-SE) accompanying a change of the nappe transport direction of the Southern Apennines. The construction of balanced sections using dedicated software, permitted us to recognize the true geometry of the faults and compute the amount of Quaternary extension of the SCM that results comparable to those calculated for other sectors of the Tyrrhenian margin and further extensional regions worldwide.

Ulises Hernández-Romano, Noemí Aguilera-Franco, Blanca E. Buitrón

The fossil content of a limestone succession of the Cuautla Formation, from the central part of the State of Morelos, indicates a late Cenomanian age. Amongst the fossils that were identified, those that do not show reworking include the calcareous algae Permocalculus irenae, P. budaensis, Heteroporella lepina, Dissocladella sp. cf. D. undulata… in order to continue, download the full paper in PDF.

FABIO STAFFINI, SILVIA SPEZZAFERRI, FULVIA AGHIB

Two recent sea-going expeditions showed that mud diapirism is a common feature in the accretionary wedge of the Mediterranean Ridge, but unlike in other prisms, it is well expressed exclusively in the most elevated areas of the Ridge. Three diapiric fields were discovered on the Mediterranean Ridge and informally called, from west to east, Pan di Zucchero, Prometheus 2 and Olimpi. They are located on the crestal part of the Mediterranean Ridge between Creta and the Cirenaic Promontory. Sedimentological, micropaleontological, and mineralogic investigations were performed on the mud breccia recovered in 15 cores raised during cruises BAN88 and BAN89. The sedimentological analyses allowed to recognize several sedimentary facies which are suggestive of different emplacement processes: 1) three massive facies are indicative of intrusion; 2) three organized facies are indicative of submarine extrusion and probably reworking. The micropaleontological study based on planktonic foraminifera and calcareous nannofossils provided an Oligocene age for the source sediments and/or for the sediments possibly involved in the diapiric processes of the Pan di Zucchero, and an Early Miocene age for the Olimpi and Prometheus 2 fields. No evidence was found of the typical Messinian lithologies, such as dolomite and gypsum, and microfossils ("lago-mare" biofacies). X-ray diffraction analyses allow to identify the major mineralogic component of the mud breccia and a westward decrease in the smectite content. Our investigations reveal that major differences occur between the Pan di Zuccchero and Olimpi areas, whereas minor differences are recorded between the Olimpi and Prometheus 2. Moreover, the Napoli Dome, located in the Olimpi area, differs from the other diapirs in several sedimentological, micropaleontological and mineralogic characters, and is interpreted as a mud volcano.

FRANCESCA R. BOSELLINI, ENRICO TREVISANI

The Castelgomberto Limestone is a 2OO m thick unit of Early Oligocene age (Rupelian) outcropping in the Eastern Lessini Mountains (Southern Alps of Northern ltaly). The internal cyclic organization of this Oligocene unit is described and analyzed on the basis of four selected sections; about thirteen well-bedded grainstone units alternate with marly horizons rich in corals. This peculiar cyclicity is here interpreted as a response to variations in platform hydrodynamics, i. e. to smaller eustatic fluctuations affecting the Lessini Shelf reef-lagoonal complex. During highstand periods, the shelf was open and relatively deep (20-50 m), and tidal currents and periodic storms were able to distribute bioclastic sands (bars, sand waves and spillovers). During lowstands the shelf was more protected by the occurrence of marginal reefs and was colonized by patches of poritid corals, mainly branching. Moreover, the largely exposed northern areas supplied fine detritus to the shelf itself.

Trevor R. Shaw

Udorni dolini ter ponori v Škocjanskih jamah so bili omenjani že v antiki in označeni na zemljevidih iz 16. stoletja, opisal jih je Valvasor (1689), obiskovali pa so jih tudi popotniki v 18. stoletju. Vzpodbudo je pomenila tudi pot, ki so jo 1823 speljali v Veliko dolino. Knjiga obiskovalcev, ki so jo uvedli 1819 je izgubljena, toda nekaj informacij o obiskih je mogoče dobiti iz drugih virov, vključno iz popotnih dnevnikov in Schmidlovih knjig okoli leta 1853. V Evopskih turističnih vodnikih je opaziti porast priljubljenosti jam. 1884 je Primorska sekcija Nemško-avstrijskega planinskega društva vzela jame v zakup in uredila vodeni turistični obisk. Isti vodniki so pomagali članom društva pri dolgotrajnih in težavnih raziskavah jam, vzporedno z njimi pa so stalno podaljševali turistično pot. V 1890-tih letih so v obisk vključili Dvorano planinskega društva in 1903 celo Martelovo dvorano. V prispevku so opisane tudi vstopnina in plačila za vodnike in razsvetljavo. After mention in Classical times and on 16th century maps, the dolines and sinks of Škocjanske jame were described by Valvasor (1689) and visited by travellers in the 18th century. Tourists were encouraged from 1823 when a path down Velika dolina was made. The visitors’ book started in 1819 is lost but information on some visits is available from other sources including travellers’ reports and Schmidl’s books of around 1853. European guide books mark the increasing popularity of the caves. In 1884 the Section Küstenland of the Deutscher und Österreichischer Alpenverein leased the caves and arranged guided tours for visitors. These same guides assisted Club members in lengthy and difficult explorations, and the tourist route was constantly extended. In the 1890s it included the Alpenvereins Dom, and in 1903 even the Martel Dom. The system of charging visitors for entry, for guides and for lights is described.

C. P. Vega, V. A. Pohjola, E. Beaudon et al.

Physical and chemical properties of four different ice cores (LF-97, LF-08, LF-09 and LF-11) drilled at Lomonosovfonna, Svalbard, were compared to investigate the effects of meltwater percolation on the chemical and physical stratigraphy of these records. A synthetic ice core approach was employed as reference record to estimate the ionic relocation and meltwater percolation length at this site during the period 2007–2010. Using this method, a partial ion elution sequence obtained for Lomonosovfonna was NO₃⁻ &gt; SO₄²⁻, Mg²⁺, Cl⁻, K⁺, Na⁺ with nitrate being the most mobile within the snowpack. The relocation length of most of the ions was on the order of 1 m during this period. In addition, by using both a positive degree day (PDD) and a snow–energy model approaches to estimate the percentage of melt at Lomonosovfonna, we have calculated a melt percentage (MP) of the total annual accumulation within the range between 48 and 70 %, for the period between 2007 and 2010, which is above the MP range suggested by the ion relocation evidenced in the LF-syn core (i.e., MP  =  30 %). Using a firn-densification model to constrain the melt range, a MP of 30 % was found over the same period, which is consistent with the results of the synthetic ice core approach, and a 45 % of melt for the last 60 years. Considering the ionic relocation lengths and annual melt percentages, we estimate that the atmospheric ionic signal remains preserved in recently drilled Lomonosovfonna ice cores at an annual or bi-annual resolution when weather conditions were similar to those during the 2007–2010 period.

Randall C. Orndorff, David J. Weary, Kerry M. Lagueux

Geološki vzroki, ki pogojujejo razporeditev in razvoj vrtač na Salem planoti, Ozarki, južno-osrednji Missouri, ZDA, so bili statistično analizirani z uporabo GIS. Geološki vzroki predstavljajo litostratigrafijo, geološko strukturo, površje in globino do talne vode. Obravnavali so področje za točkovne podatke 2.613 vrtač na dveh 30’ × 60’ kartah s 30 m intervali. Izračunali so % pogostosti vrtač za pet litostratigrafskih enot, pri čemer so ugotovili, da je v Jefferson City dolomitu in Roubidoux formaciji največja gostota vrtač. Opravljena je bila analiza žariščne vsote sosedstva, da bi ugotovili, če ima razporeditev vrtač značilnost združevanja v skupine ali značilnost linearnosti, kar kaže na vpliv geološke strukture. Usmerjenost skupin vrtač na SZ se pojavlja vzdolž projekcije prelomne cone Bolivar-Mansfield v južno-osrednjem Missouriju. Večina vrtač na obravnavanem terenu se nahaja na območjih uravnav in na položnih pobočjih, kar je pogosteje kot na močno razčlenjenih področjih. Močna razpokanost v bližini regionalnih prelomnih con lahko pospeši razvoj vrtač na planoti. Razumevanje kraškega sistema je pomembno za boljše urejanje uporabe zemlje v Ozarkih, vključno z ohranjanjem naravnih virov, urejanjem talne vode in varovanjem okolja, še posebno ker raziskani teren vsebuje možne ekonomsko ugodne zaloge Pb in Zn. The geologic controls on the distribution and development of dolines in the Salem Plateau of the Ozark Plateaus Province, south-central Missouri, USA, was statistically analyzed by using a geographic information system. The controls include lithostratigraphy, geologic structure, slope, and depth to water table. Area and point data for 2,613 dolines in two 30’ x 60’ quadrangles were compiled on a 30-meter grid. The percent area of dolines was calculated for five lithostratigraphic units, and it was determined that the Jefferson City Dolomite and Roubidoux Formation have the highest density of dolines. A focal sum neighborhood analysis was performed to determine if the distribution of dolines had any clustering or linearity that may suggest structural control. A northwest alignment of doline clusters occurs along a projection of the Bolivar-Mansfield fault zone in south-central Missouri. Most dolines in the study area occur on the plateau areas and on gentle slopes rather than in the highly dissected areas. Intense fracturing near regional fault zones may enhance doline development on the plateau areas. An understanding of the karst system is important for better landuse management practices in the Ozarks, including conservation of natural resources, ground-water management, and environmental protection, especially because the study area includes potential economic lead and zinc mineralization.