Hasil untuk "Petrology"

Rufaida T. Ibrahim, Watheq J. Al-Mudhafar, Dahlia A. Alobaidi et al.

Abstract Anthropogenic CO2 emissions are a key factor in global climate change, necessitating technologies that improve energy security and enable permanent CO2 sequestration. CO2-enhanced oil recovery (CO2-EOR), combined with carbon capture, utilization, and storage (CCUS), offers a strategy to boost hydrocarbon production while reducing atmospheric CO2. However, challenges such as reservoir heterogeneity, early gas breakthrough, and inefficient sweep dynamics hinder its widespread deployment, affecting both economic viability and storage permanence. This comprehensive review, therefore, examines the historical evolution, fundamental mechanisms, and future potential of CO2-EOR. A critical analysis of advanced injection techniques—continuous gas injection (CGI), water-alternating-gas (WAG), and gas-assisted gravity drainage (GAGD)—addresses persistent challenges including gas breakthrough, poor sweep efficiency, and reservoir heterogeneity. The physicochemical mechanisms of CO2-EOR, such as miscibility, capillary effects, and displacement efficiencies, are detailed, with a comparative assessment of horizontal versus vertical flooding approaches. The GAGD process is highlighted as a gravity-dominated alternative, with analysis focused on its underlying mechanisms, operational parameters, and dimensionless governing forces. Furthermore, the integration of CO2-EOR with carbon capture and storage (CCS) is explored as a dual strategy for emission reduction and reservoir revitalization. The review also evaluates economic and environmental criteria for CO2 selection, reservoir complexities, and containment risks. By synthesizing current practices, challenges, and advancements, this work positions CO2-EOR as an essential approach for aligning energy production with decarbonization targets, with its novelty lying in a focused analysis of gravity-stable processes and their integration within the carbon utilization and storage framework.

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.

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.

Ahmad Jamshidzaei, Khadijeh Khalili, Ghodrat Torabi

The Godar-e-Siah Eocene monzodiorite stock is located in the southwest of the Jandaq area (NE of Isfahan) and northwest of the Central-East Iranian Microcontinent (CEIM). The main minerals in these monzodiorites are plagioclase, K-feldspar, clinopyroxene, phlogopite, and garnet, which are set in a fine-grained groundmass of feldspars. The main textures are granular, porphyritic, and poikilitic. In some cases, these rocks contain euhedral to subhedral garnet crystals with inclusions of the igneous clinopyroxene and groundmass minerals including feldspar and graphite. These garnets exhibit Ti-andradite and Ca-melanite composition from the solid solution series of andradite-grossular. The chemical zoning patterns of the studied garnets confirm that these garnets have a non-magmatic origin and metamorphic nature. In the investigated monzodiorites, the presence of euhedral garnet crystals with inclusions of igneous clinopyroxenes metasomatic scapolite, and metasomatic phlogopite shows that these garnets are of metasomatic origin, which formed due to the alteration of igneous clinopyroxenes. All geochemical and petrographic evidences from the studied garnets indicate that they have formed as a result of the intrusion of Eocene monzodiotites into the carboniferous limestones (or dolomites), leading to the creation of endoskarn or reactions skarn that can be distinguished at the millimetric scale in microscopic studies. Introduction Garnet is a general mineral forms in metamorphic rocks derived from the sedimentary and igneous protoliths and at all metamorphic grades above the greenschist facies (Baxter et al., 2017). However, the presence of garnet in certain types of igneous rocks, such as peraluminous granite and ultramafic rocks in the upper mantle, introduces complexities in unraveling the petrogenesis of garnets in igneous and metamorphic rocks (Rong et al., 2018). Titanium-rich garnets are enriched in andradite, occur in various types of rocks, including a variety of igneous rocks, encompassing trachytes and phonolites (Dingwell and Brearley 1985), syenites and carbonatites, nephelinites and tephrites (Gwalani et al., 2000), as well as ultramafic lamprophyres, rodingites (Schmitt et al., 2019); high temperature metamorphic rocks and skarns. The composition of titaniferous garnets besides their paragenetic relationships is one of the significant petrology factors (Chakhmouradian and McCammon, 2005). The study area is situated in the northwestern part of the CEIM (northwestern part of the Yazd block), and southwest of the Jandaq City. The rock units of the Jandaq area are mainly include Paleozoic metamorphic rocks, Upper Paleozoic sedimentary rocks, Cretaceous and Paleocene sediments, Eocene intrusive rocks, Eocene subvolcanic (dikes) and volcanic rocks (Jamshidzaei et al., 2021), the Pis-Kuh upper Eocene sedimentary rocks (flysch), and Early Oligocene lamprophyric rocks, and alkali basalts (Torabi, 2010; Berra et al., 2017; Sargazi et al., 2019; Jamshidzaei et al., 2021). In this paper, the chemical characteristics of the monzodiorite stock and origin of garnet mineral are discussed. Material and methods To determine the chemical compositions of minerals, JEOL JXA-8800 WDS at the Department of Earth Science, Kanazawa University, Kanazawa, Japan was used. Chemical analyses of minerals was performed under an accelerating voltage of 20 kV, a probe current of 20 nA, and a focused beam diameter of 3μm. The ZAF program was used for data correction. Natural minerals and synthetic materials with well-characterized compositions serve as standards for calibration and validation purposes. The Fe2+# and Mg# parameters of minerals are represented by the atomic ratios of Fe2+/(Fe2++Mg) and Mg/(Mg+Fe2+), respectively. To recalculate the FeO and Fe2O3 concentrations from Fe2O3*, recommended ratios of Middlemost (1989) is used. The mineral abbreviations used in this context are derived from Whitney and Evans (2010). Results and discussion The monzodiorites of the Godar-e-Siah area mostly show fine to coarse-grained granular, porphyritic and poikilitic textures. These rocks are mesocrate in color, displaying massive and mineralogically homogeneous nature in their outcrops. K-feldspars are the primary minerals and garnet mineral is imposed on these rocks. The main minerals of this monzodiorite stock are plagioclase, K-feldspar, clinopyroxene, phlogopite, and garnet, set in a fine-grained matrix of feldspars. These rocks have mainly granular, porphyritic, and poikilitic textures. In some cases, these rocks contain euhedral to subhedral garnet crystals with inclusions of igneous clinopyroxene and groundmass minerals including feldspar and graphite. These garnets have a composition of Ti-garnet and Ca-melanite from the solid solution series of andradite-grossular. Based on the EPMA data, the clinopyroxenes show diopside to hedenbergite compositions, indicating that two types of clinopyroxene are in these rocks. The first group of this mineral contain MgO (6.9-10.20 wt.%), FeO*(11-16.88 wt.%), Al2O3 (2-5.84), and Na2O (1.1-1.9 wt.%), is reactive pyroxenes. The second category contains MgO (9.98-12.89 wt.%), FeO* (9.13-13.87 wt.%), Al2O3 (1.82-3.11 wt.%), and Na2O (0.7-1.42% Wt.%), is igneous pyroxenes. Chemistry of the pyroxenes reveals that reactive pyroxenes have higher concentrations of FeO* and Al2O3 than igneous pyroxenes. Chemistry of the feldspars indicates that the K-feldspars is orthoclase in composition. Also, chemical analyses of mica show that these minerals contain high concentrations of MgO (21.54-22.60 wt.%) and low values of Al2O3 (12.89-13.30 wt.%). The mica from the studied rocks of the Jandaq area plots in the phlogopite field. The garnet grains in these rocks contain 61.94-66.39 mol.% almandine (Fe2Al2Si3O12), 18.60-23.40 mol.% grossular (Ca3Al2Si3O12), 10.06-15.11 mol.% pyrope (Mg2Al2Si3O12), and 1.09-4.32 mol.% spessartine (Mn2Al2Si3O12). These garnets have a composition of Ti-garnet and Ca-melanite from the solid solution series of andradite-grossular. The chemical zoning patterns of the studied garnets confirm that these garnets have a non-magmatic origin and metamorphic nature. The presence of discontinuous chemical zoning and the pattern of variations in the end-member compositions of these garnets indicate that they were formed under disequilibrium conditions accompanied by changes in the environmental oxidation conditions. In the studied monzodiorites, the presence of euhedral garnet crystals with inclusions of igneous clinopyroxenes, metasomatic scapolite, and metasomatic phlogopite shows that these garnets are of metasomatic origin which formed due to the alteration of igneous clinopyroxenes. The geochemical characteristics and petrographic evidences from the studied garnets; including the presence of euhedral crystals with distinct boundaries to contact minerals, the occurrence of inclusions of background minerals and igneous clinopyroxenes in the garnets, as well as the presence of discontinuous chemical zoning, confirms that they have formed as a result of the intrusion of Eocene monzodiotites into the carboniferous limestones (or dolomites), leading to the creation of endoskarn or reactions skarn.

Pengfei Zuo, Haihua Cheng, A. J. C. Magalhães et al.

Dolostone, with its complex diagenetic history, has long been debate. The formation of patchy dolostone, which consists of various types of dolomites, is particularly controversial due to the superimposed diagenetic events. In this study, we conducted mineralogical and stable isotope geochemical analyses of the Ediacaran patchy dolostone from the Dengying Formation in South Qinling to elucidate the diagenetic processes involved. Microscopic examination reveals that the patchy dolostone can be classified into three types: Type I, composed of micritic to powdery crystalline dolomite (D1) and fine crystalline dolomite (D2); Type II, primarily consisting of medium-coarse crystalline dolomite (D3) along with D2; and Type III, characterized by the presence of saddle dolomite (SD) and D1. Cathodoluminescence and electron probe microanalysis indicate that D2 and D3 are enriched in Mn and Fe, whereas SD is depleted in Sr and Na compared to D1. Backscattered electron images reveal a prevalence of apatite, particularly in Type III dolostone. Calcite and quartz extensively replace the dolomites. Carbon and oxygen isotopes indicate that D1 has the highest δ13C and δ18O values, while D2 and D3 show negative shifts, and SD exhibits the lowest values. These observations suggest that the transition from D1 to D2 and D3 is due to recrystallization processes during burial. The formation of SD is likely the result of hydrothermal activity. Consequently, the patchy dolostone experienced three main stages of diagenesis, which included the recrystallization of D1 and the formation of SD. Considering the vertical distribution of the patchy dolostone and the occurrence of hyperkarst breccia dolostone, it is reasonable to infer that sea level variations are the primary cause of the formation of patchy dolostone.

A. Ogbamikhumi, J. O. Ebeniro

Abstract In an attempt to reduce the errors and uncertainties associated with predicting reservoir properties for static modeling, seismic inversion was integrated with artificial neural network for improved porosity and water saturation prediction in the undrilled prospective area of the study field, where hydrocarbon presence had been confirmed. Two supervised neural network techniques (MLFN and PNN) were adopted in the feasibility study performed to predict reservoir properties, using P-impedance volumes generated from model-based inversion process as the major secondary constraint parameter. Results of the feasibility study for predicted porosity with PNN gave a better result than MLFN, when correlated with well porosity, with a correlation coefficient of 0.96 and 0.69, respectively. Validation of the prediction revealed a cross-validation correlation of 0.88 and 0.26, respectively, for both techniques, when a random transfer function derived from a given well is applied on other well locations. Prediction of water saturation using PNN also gave a better result than MLFN with correlation coefficient of 0.97 and 0.57 and cross-validation correlation coefficient of 0.89 and 0.3, respectively. Hence, PNN technique was adopted to predict both reservoir properties in the field. The porosity and water saturation predicted from seismic in the prospective area were 24–30% and 20–30%, respectively. This indicates the presence of good quality hydrocarbon bearing sand within the prospective region of the studied reservoir. As such, the results from the integrated techniques can be relied upon to predict and populate static models with very good representative subsurface reservoir properties for reserves estimation before and after drilling wells in the prospective zone of reservoirs.

Christopher J. Spencer, Ross N. Mitchell, Michael Brown

Abstract Since the Archean, secular change in orogenic style is demonstrated through evolution of metamorphic conditions and geochemical proxies. Linked to orogenic style is the amount of crustal thickening and elevation, whereas orogenic vigor is related to the supercontinent cycle. An array of Proterozoic orogens spanned the assembly of supercontinents Columbia and Rodinia, but the vigor of orogenesis is debated, with proposals for both Mesoproterozoic quiescence and climax. We show mid‐Proterozoic orogenesis occurred globally and was broadly continuous; furthermore, orogens exhibit elevated metamorphic thermobaric ratios with large volumes of high‐temperature felsic magmatic rocks. These features reflect higher mantle heat flux leading to increased mid‐crustal flow and lower elevation. In this context, proposals that geochemical proxies for crustal thickness record orogenic quiescence are inconsistent with the geological record. Alternatively, secular change in crustal thickness is attributed to orogenic style, namely the prevalence of hot, thin, and low orogens in the mid‐Proterozoic.

Mattia Bonazzi, Antonio Langone, Simone Tumiati et al.

Corundum-rich (up to 55 vol.%) felsic dykes formed with albite, ±K-feldspar, ±hercynite and ±biotite-siderophyllite cut the lower crustal rocks exposed in the Ivrea–Verbano Zone (NW Italy). Zircon is an abundant accessory mineral and its investigation through laser ablation-inductively coupled plasma (multi-collector)-mass spectrometer (LA-ICP-(MC)MS) has allowed results to directly constrain the timing of emplacement, as well as petrology and geochemistry of parental melts. Zircons are characterized by very large concentration in rare earth elements (REE), Th, U, Nb and Ta, and negative Eu anomaly. U–Pb analysis points to Norian emplacement ages (223 ± 7 Ma and 224 ± 6 Ma), whereas large positive εHf_(t) values (+13 on average) indicate a derivation from depleted to mildly enriched mantle source. The mantle signature and the corundum oversaturation were preserved thanks to limited crustal contamination of the host, high-temperature refractory granulites and mafic intrusives. According to the geochemical data and to the evidence of the development of violent explosions into the conduits, it is proposed that dykes segregated from peraluminous melts produced by exsolution processes affecting volatile-rich differentiates during alkaline magmatism. This work provides robust evidence about the transition of the geochemical affinity of Southern Alps magmatism from orogenic-like to anorogenic during Norian time, linked to a regional uprising of the asthenosphere and change of tectonic regime.

Agus Abdullah, Waskito Pranowo

Abstract Seismic artifacts due to random and linear noises, low fold coverage, statics, and spatial aliasing are frequently affecting uncertainties in seismic interpretation. Several conventional methods, such as median filter, have been implemented to reduce random noises. However, this method can not be utilized for the area in which rich with stratigraphic features such as clinoforms and in the area with strong dips. We implemented layer-steered filter in order to attenuate random noises in this kind of situation. Layer-steered filter has ability to attenuate random noises but still respects to local dip events; therefore, the method provides better preservation of events and stratigraphics compared to other conventional methods such as median filter and dip-steered filter.

M. Fouad Snosy, Mahmoud Abu El Ela, Ahmed El-Banbi et al.

Abstract Waterflooding has been applied for many years as secondary recovery method with no or little regard to the effect of the injected water salinity on oil recovery. However, in the last decade, there has been an increasing interest in understanding the effects of changing injected water salinity on reservoir performance. The potential of low-salinity waterflooding (LSWF) has been studied in sandstone reservoirs by numerous core-flooding experiments. These experiments have shown diverse results. This paper aims to investigate the effects of changing water salinity on oil recovery. A comprehensive review and analysis of the results of more than 500 core-flood experiments from published work were investigated to study the effects of several parameters such as clay content, clay type, and temperature on oil recovery. The relation between incremental oil recovery and sodium adsorption ratio SAR, and exchangeable sodium percentage (ESP) parameters which control clay swelling was illustrated. The analysis of the results revealed that there is an optimum composition and optimum salinity for waterflooding in secondary flooding stage. However, for tertiary flooding stage, the results showed that the controlling factor may be not decreasing the salinity but rather changing the salinity (e.g., either increasing or decreasing) with minor improvement in oil recovery. It was clear also that applying the optimum salinity in the secondary recovery stage is more effective than applying it in the tertiary recovery stage. This study aims to develop important guidelines for screening and designing optimum salinity for waterflooding projects in sandstone reservoirs.

Natalia S. Petrova, Natalia Yu. Denisova, Aliaksei V. Kirykovich

The requirements of complex subsoil use are increasing in the Pripyat potash-bearing basin: potash ore of new technologic types, with lower contents of useful components, increased concentrations of harmful impurities. Using all complex of quality indicators assessment of natural types of potash ore is undoubtedly prioritized by characteristic of potash deposits. The study of structural and textural features and composition of potash deposits has been given attention since the time of discover of the Starobin deposit. Systematic study of salt rock petrology has been started after the discovery of the Starobin deposit. Until now in the petrology, there is no recognized rational genetic classification of the structures of salt rocks being potash (potassium-magnesium) ore. The name of certain structure is based on the secondary features that are brightly expressed, color or similarity with different objects. The aim of the present work is an element recognition of the primary sedimentary features of rocks, systematization of primary and secondary characteristics and their typification according to petrochemical parameters. In the article the main microfabric types of potash ore that are typical for the deposits of red-colored and mottled hypersaline association of the Pripyat basin.

Guang-Hui Yuan, Ying-Chang Cao, Jon Gluyas et al.

Abstract Burial dissolution of feldspar and carbonate minerals has been proposed to generate large volumes of secondary pores in subsurface reservoirs. Secondary porosity due to feldspar dissolution is ubiquitous in buried sandstones; however, extensive burial dissolution of carbonate minerals in subsurface sandstones is still debatable. In this paper, we first present four types of typical selective dissolution assemblages of feldspars and carbonate minerals developed in different sandstones. Under the constraints of porosity data, water–rock experiments, geochemical calculations of aggressive fluids, diagenetic mass transfer, and a review of publications on mineral dissolution in sandstone reservoirs, we argue that the hypothesis for the creation of significant volumes of secondary porosity by mesodiagenetic carbonate dissolution in subsurface sandstones is in conflict with the limited volume of aggressive fluids in rocks. In addition, no transfer mechanism supports removal of the dissolution products due to the small water volume in the subsurface reservoirs and the low mass concentration gradients in the pore water. Convincing petrographic evidence supports the view that the extensive dissolution of carbonate cements in sandstone rocks is usually associated with a high flux of deep hot fluids provided via fault systems or with meteoric freshwater during the eodiagenesis and telodiagenesis stages. The presumption of extensive mesogenetic dissolution of carbonate cements producing a significant net increase in secondary porosity should be used with careful consideration of the geological background in prediction of sandstone quality.

Suparit Tangparitkul

Abstract The new method to evaluate the contribution of the related factors to the oil recovery is proposed by using the desirability model. The related factors are re-scaled and combined to be a single parameter in order to correlate with an indicator of oil recovery. The correlated result could be able to predict a trend of the factors and oil recovery as an empirical approach if a good correlation is achieved. Three published works of the coreflooding experiments are examined the effectivenesses and limitations of the proposed model. The analysed plots of desirability and the oil recovery imply an insight into the oil recovery mechanisms by indicating the dominant factors. The results meet a good agreement with the published works. Although the dominant factors are indicated and the correlation trend is able to be determined, the accuracy of the proposed method needs a high number of data sets to increase the statistical reliability.

Jie He, Hua Wang, Chengcheng Zhang et al.

Abstract The sandstone from the Oligocene Xiaganchaigou Formation (E3) in the Lengdong area, Qaidam Basin, China, is extensively distributed and acts as an effective regional reservoir for hydrocarbon accumulation. Based on thin sections, scanning electron microscopy (SEM), X-ray diffraction (XRD) image analysis and cathodoluminescence (CL), a comprehensive analysis of the sedimentology, petrography, diagenesis and reservoir quality of the Oligocene sandstone reservoirs of the Xiaganchaigou (E3) Formation in the Lengdong area, Qaidam Basin, are studied. The sandstones in the Lengdong area are classified as argillaceous sandstone, silty sandstone, fine sandstone, medium sandstone, pebbly sandstone, conglomeratic sandstone and conglomerate based on their grain sizes, degrees of sorting, and matrix contents. Five sedimentary facies were identified in the Xiaganchaigou Formation (E3) of the Lengdong area, Qaidam Basin: distributary channel, interdistributary bay, mouth bar, central bar and distal sand sheet facies. Their major diagenetic processes include compaction, carbonate cementation and feldspar and calcite cement dissolution. The porosity and permeability values of the fine sandstone, conglomerate, and conglomeratic sandstone are the highest, followed by those of the medium sandstone and silty sandstone, and the argillaceous sandstone and pebbly sandstone have the lowest porosity and permeability values. The diagenetic sequence in the study area ranges from the eodiagenesis B stage to the mesodiagenetic A stage. Compaction has significantly reduced the primary porosity. Carbonate cements, mainly calcite cements, occlude pores by precipitating in intergranular and intragranular spaces. Dissolution largely contributes to increasing the secondary porosity. The well-sorted and relatively coarser-grained sandstones that formed in higher-energy sedimentary facies (distributary channel, mouth bar and central bar) have a better reservoir quality than the poorly sorted, clay-rich sandstones that formed in low-energy environments (interdistributary bay and distal sand sheet). Based on the comprehensive analysis of petrographic data, diagenesis and sedimentary facies, the reservoir in the Lengdong area is classified into three types: type A, type B and type C. Type A, located in the center of the study area, is the most favorable reservoir, while type C sandstone is the last to consider when looking for a good reservoir. This study can guide hydrocarbon exploration in the Lengdong area, as well as in northwestern China and similar areas throughout the world.

K. F. Fozao, L. Fotso, A. Djieto-Lordon et al.

Abstract The use of seismic attributes for understanding reservoir complexity has been proven to work in several fields. Thus, we demonstrate applications of seismic attributes for evaluating the oil and gas reservoirs in the eastern portion of the Rio del Rey (RDR) Basin. The presence of these fluids in twenty-six (26) reservoirs of the study area was confirmed with the help of Larson VizEx Pro software using well and seismic data. The 3D merged seismic data reprocessed in 2011 were used to extract the root-mean-square (RMS) and maximum amplitude attributes for each of the reservoirs. Forty-seven (47) RMS and maximum surface attributes were generated using Petrel E&P 2014 software. Seven (7) of these attributes have been presented. Quality control using Interactive Petrophysics (IP) software was applied on the reservoir fluid type found in each well. These fluid types were later superposed on each of the amplitude maps to match the corresponding amplitude responses. A good match could be observed between some well tops and their corresponding amplitude values. The results obtained indicate that GH and WX concessions could be the best concessions in the eastern part of the RDR Basin since most of their reservoirs, especially WX S6.3 maximum amplitude map, matched with their well fluid contents. The results obtained have been used to propose potential areas for further drilling.

Pia Orywall, Kirsten Drüppel, Dietmar Kuhn et al.

Abstract After publication of the article (Orywall et al. 2017), it has been brought to our attention that there are a number of errors. The authors have listed them below.

Pedro Robledo Ardila, Luis Pomar

V obalnih stenah na Mallorci (Zahodno Sredozemlje) so obsežni izdanki zgornjemiocenskih karbonatnih kamnin. Na vzhodni obali otoka prekrivajo grebenski sklop mesinijski plitvovodni karbonati. Tod so v zgornjemiocenskih kamninah številne paleokraške podorne strukture. V apnence Santanyí so vrezane strukture v obliki črke V, kar kaže na udiranje stropov jam, nastalih v spodaj ležečih grebenskih sklopih. Glede na model je mogoče nastanek nekaterih izmed teh kraških podornih struktur povezati z zgodnjimi diagenetskimi procesi, na katere so vplivale pogoste spremembe nivoja morske gladine. V času nizkega nivoja morske gladine je sladkovodni tok izdolbel jamski sistem v bližini vodne gladine na tak način, da je raztapljal aragonit v frontalnem faciesu in skupke koral v obstoječih lagunskih plasteh. Ta jamski sistem se je razvijal v bližini površinske erozijske baze. Med kasnejšim dvigom morske gladine so plasti notranjega dela šelfa prekrile predhodno zakraselo jedro grebena in izvenlagunske plasti. Vrezane »V« strukture je lahko povzročila povečana teža odloženih plitvovodnih karbonatov, zaradi česar je prihajalo do gravitacijskih udiranj jamskih stropov v času, ko te plasti še niso bile popolnoma strjene. In the sea cliffs on the Mallorca Island, Western Mediterranean there are extensive outcrops of Upper Miocene carbonate rocks. On the Eastern coast of Mallorca, the reefal complex is overlain by a Messinian shallowwater carbonate complex. There are abundant Paleokarst collapse structures. The Santanyí Limestone beds are affected by V-incasion structures produced by roof collapse of caverns developed in the underlying reefal complex. According to the model, the origin of some of these karst-collapse structures may be related to early diagenetic processes controlled by high-frequency sea-level fluctuations. During lowstands of sea level, freshwater flow might have create a cave system near the water table by dissolution of aragonite in the reef front facies and coral patches existing in the lagoonal beds. This cave system developed near the subaerial erosion surface. During subsequent rise of sea level inner-shelf beds overlaid the previously karstified reef-core and outer-lagoonal beds. Increase of loading by subsequent accretion of the shallow-water carbonates might have produced V-incasion structures by gravitational collapse of cave roofs when these beds were still not completely consolidated.

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.

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.

W. Engelhardt, H. Füchtbauer, G. Müller et al.