rss_2.0Geologos FeedSciendo RSS Feed for Geologos Feed steady state<abstract> <title style='display:none'>Abstract</title> <p>Nature is never at a steady state. Natural history is generated by ever-new and ever-interacting forces that produce continuous changes. At virtually all timescales, the geological record shows that these changes do not cancel each other out and, thus, that the steady state is utopic. However, we need a state of equilibrium as a starting point for modelling Nature, and the steady-state condition is widely used as a reference in idealisations aimed at understanding natural processes. The present contribution is meant as an epistemological note of caution − from Earth scientists to Earth scientists − aimed at discouraging the use of theoretical models as true evidence instead of terms of comparison.</p> </abstract>ARTICLEtrue phases affecting the colour of upper Neogene clayey sediments from Dymaczewo Stare, west-central Poland<abstract> <title style='display:none'>Abstract</title> <p>The present paper investigates the colour dependence of mineral compositions in clay-rich sedimentary strata, mainly clayey silts, the emphasis being on iron-bearing minerals (rather than clay minerals) by using powder X-ray diffraction (PXRD) and <sup>57</sup>Fe Mössbauer spectroscopy (<sup>57</sup>Fe-MS). The PXRD-based phase analysis has demonstrated the variable compositions of samples, consisting of, <italic>inter alia</italic>, quartz, calcite or gypsum, and admixtures of potassium feldspars and plagioclase. Hematite + goethite (sample D1, dark red), goethite (sample D2, pinkish brown), poorly crystalline goethite (sample D3, orange) and jarosite (sample D4, yellow) have been distinguished. A very low jarosite content was detected in sample D5 (light grey); this did not affect its colour. The potential yellow/brown shades in sample D6 (dark grey), coming from trace amounts of jarosite, are masked by macroscopically visible organic matter. In the case of the two last-named samples (D5 and D6), with trace amounts of Fe-bearing minerals, it is most likely that the organic matter was effective in influencing the light and dark grey colour of the sediment, respectively.</p> </abstract>ARTICLEtrue reviews: Introduction to environmental modelling reviews: Structural geology: principles, concepts, and problems (3rd edition) reviews: Volcanoes: a very short introduction magnitude distribution and spatial correlation dimension of earthquakes in north-east Himalaya and adjacent regions<abstract> <title style='display:none'>Abstract</title> <p>The north-east sector of the Himalaya is one of the most active tectonic belts, with complex geological and tectonic features. The b-value and spatial correlation dimension (D<sub>c</sub>) of earthquake distribution in the north-east Himalaya and its adjacent regions (20–32°N and 88–98°E) are estimated in the present study. Based on seismicity and faulting pattern, the region is divided into five active regions, namely the (i) South-Tibet, (ii) Eastern-Syntaxis, (iii) Himalayan-Frontal Arc, (iv) Arakan-Yoma belt and (v) Shillong-Plateau. A homogeneous catalogue of 1,416 earthquakes (mb ≥ 4.5) has been prepared from a revised catalogue of the ISC (International Seismological Centre). The b-value has been appraised by the maximum likelihood estimation method, while D<sub>c</sub> values have been calculated by the correlation integral method; b-values of 1.08 ± 0.09, 1.13 ± 0.05, 0.92 ± 0.05, 1.00 ± 0.03 and 0.98 ± 0.08 have been computed for the South-Tibet, Eastern-Syntaxis, Himalayan-Frontal Arc, Arakan-Yoma belt and Shillong-Plateau region, respectively. The D<sub>c</sub> values computed for the respective regions are 1.36 ± 0.02, 1.74 ± 0.04, 1.57 ± 0.01, 1.8 ± 0.01, and 1.83 ± 0.02. These values are &gt; 1.5, except for the South-Tibet (1.36 ± 0.02). The b-values around the global average value (1.0) reflect the stress level and seismic activity of the regions, while high D<sub>c</sub> values refer to the heterogeneity of the seismogenic sources.</p> </abstract>ARTICLEtrue of the geotouristic potential of geosites in Divjakë-Karavasta National Park, Albania<abstract> <title style='display:none'>Abstract</title> <p>Elements of geodiversity evaluated for scientific value should be protected, conserved and promoted as potentially important for geotourism. The Divjakë-Karavasta National Park is a large natural area that comprises six geosites along the Adriatic coastline of Albania. Geosites are elements of the geosphere that should be preserved for geoeducation of the present and future generations, in view of the fact that they yield significant data on Earth’s history. By means of the Geosite Assessment Method (GAM) and the SPSS program (version 20), we have analysed the geotouristic values of the Divjakë-Karavasta geosites and interpreted the importance of each subindicator. A correlation analysis, performed through SPSS and Pearson’s correlation coefficient as a test statistics, has been carried out as well. The Pearson’s correlation coefficient reflects the strong relationship between the scientific/educational values (i.e., representativeness and scientific knowledge) and touristic values (promotion, number of visitors, interpretative panels, hostelry services, restaurant services, touristic infrastructure). These coefficients express the importance of the dependence of additional values in the development of geotourism at protected sites.</p> </abstract>ARTICLEtrue the glaciogenic origin of Gondwana diamictites of the Dwyka Group, South Africa<abstract> <title style='display:none'>Abstract</title> <p>The Gondwana Late Palaeozoic Ice Age is probably best represented by the Dwyka Group in South Africa. Striated and grooved surfaces or pavements are commonly considered to have formed subglacially, as are diamictites which have been interpreted as <italic>in-situ</italic> or reworked tillites. These interpretations were tested by investigation of outcrops in formerly well-studied areas, throughout South Africa. Detailed analyses have focused on striated surfaces/pavements and surface microtextures on quartz sand grains in diamictites. The sedimentological context of four pavements, interpreted to be glaciogenic, display features commonly associated with sediment gravity flows, rather than glaciation. A total of 4,271 quartz sand grains were subsampled from outcrops that are considered mainly to be tillites formed by continental glaciation. These grains, analysed by SEM, do not demonstrate the characteristic surface microtexture combinations of fracturing and irregular abrasion associated with Quaternary glacial deposits, but mainly a mix of surface microtextures associated with multicyclical grains. The Dwyka Group diamictites warrant reinterpretation as non-glacial sediment gravity flow deposits.</p> </abstract>ARTICLEtrue settings of Jurassic granitoids in the Sanandaj-Sirjan Zone, Iran: A review<abstract> <title style='display:none'>Abstract</title> <p>The present paper discusses the geochemical affinities, origin and ages of Jurassic granitoids of the Sanandaj-Sirjan Zone (SaSZ) in the eastern part of the Zagros Thrust Zone. A multidisciplinary, integrated approach was carried out using existing granitoid geochemical data (major, trace, rare earth element and isotopes) and knowledge of the regional geology (geodynamic and metamorphic setting), coupled with geophysical data (magnetic susceptibility) from granitoids in the SaSZ. We re-interpret and re-classify the Jurassic granitoids of this zone into three main genetic groups: S-type, I-type and A-type subduction-related ones. In the central to southern part of the Sanandaj-Sirjan zone (between Hamadan and Sirjan), S-type magmatism appeared between 178 and 160 Ma during the Cimmerian orogeny, due to continental collision. To the north of the Sanandaj-Sirjan zone (between Sanandaj and Ghorveh), I-type and A-type magmatism occurred between 158 and 145 Ma. This heterogenic tectonomagmatic system along the SaSZ suggests a heterogenic subcontinental lithospheric mantle, resulting in two Jurassic tectonomagmatic zones of (1) the Sanandaj-Ghorveh Zone and (2) the Hamadan-Sirjan Zone.</p> </abstract>ARTICLEtrue hydrogeology, by Jiao Jimmy and Vincent Post, 2019. Cambridge University Press, Cambridge, UK. 403 pages. Hardback: price £49.99, ISBN: 9781107030596. characteristics, mode of transportation and depositional environment of the Stormberg Group in the Eastern Cape, South Africa: evidence from grain size and lithofacies analyses<abstract> <title style='display:none'>Abstract</title> <p>The Stormberg Group comprises the Molteno, Elliot and Clarens formations and is one of four stratigraphical groups that make up the Karoo Supergroup in South Africa. The group is the highest unit in the Karoo Basin, representing the final phase of preserved sedimentation. The major problem with the Stromberg Group is that the mode of transport, hydrodynamic energy conditions and depositional environment are still poorly understood. For the present paper, grain size and lithofacies studies on selected sandstones from the Molteno, Elliot and Clarens formations were performed so as to elucidate their textural characteristics, depositional processes, sedimentation mechanisms and hydrodynamic energy conditions and to discriminate different depositional environments. The statistical parameters of grain size distribution (mean grain size, standard deviation, skewness and kurtosis) show that the sandstones are predominantly unimodal, fine grained, moderately well sorted, mesokurtic and near symmetrical. The bivariate diagrams of the aforementioned statistical parameters demonstrate that river and aeolian dune had the greatest impact on the depositional environments. Likewise, the C-M pattern (Passega diagram) shows that the sandstones were mostly deposited through tractive current process. Furthermore, the C-M diagram reveals the prevalence of rolling, suspension and graded suspension modes of sediment transportation. Seventeen sedimentary lithofacies were identified and grouped into seven lithofacies associations. These lithofacies associations indicate braided channel, overbank and swamp deposits for the Molteno Formation, alluvial fan/floodplain and playa deposits for the Elliot Formation and aeolian deposits for the Clarens Formation.</p> </abstract>ARTICLEtrue reviews: The Nile Basin: Quaternary geology, geomorphology and prehistoric environments, by Martin Williams, University of Adelaide, 2019. Cambridge University Press, Cambridge, UK. Hardback: price £105.00, ISBN: 9781107179196 of potholes formed on bedrock sandstones at Loei Dun, Phetchabun Geopark, Thailand<abstract> <title style='display:none'>Abstract</title> <p>Phetchabun National Geopark comprises varied geosites; one of the fluvial bedrock landforms distinguished here is Loei Dun. This shows many potholes in Mesozoic sandstone of the Nam Phong Formation (Khorat Group). A genetic study of the occurrence of the Loei Dun potholes lends it a higher geoheritage value. For the present study we did fieldwork and carried out petrographical and geotechnical analyses so as to classify and characterise the potholes and consider geotourism potentials. Petrographically, the bedrock sandstone is a lithic arenite which consists of 82-96 percent very fine to coarse, well-sorted subangular sand with low sphericity and calcite cementation. Our geotechnical analysis of the bedrock sandstone suggests that pothole occurrence may be linked to low rock strength and slake durability index with high rock absorption and porosity at Loei Dun. Field studies confirmed the impact of other factors such as joints/faults, fluvial conditions and biological weathering. There are five types of pothole, viz., simple ones, potholes with external furrows, compound potholes, breached potholes and lateral ones. The present study adds educational value to the Loei Dun geosite at Phetchabun Geoparks and cultural and economic aspects can be further strengthened through the development of geotourism in the area.</p> </abstract>ARTICLEtrue filtration for climate resilience: potentiality of a new site along the Ismailia Canal in Egypt<abstract> <title style='display:none'>Abstract</title> <p>Bank filtration (BF) is a nature-based solution that can provide safe drinking water at a low cost, in being a green technology that benefits from natural ecosystem services and saves energy as well. The objective of the present paper is to evaluate the potentiality of a new site for bank filtration along a surface water source that experiences periods of both high and low flow. This site is located along the Ismailia Canal in the eastern Nile Delta fringe of Egypt. The present evaluation is based on exploratory drilling, installation of monitoring infrastructure and monitoring of both water level and water quality parameters for one year. The site has favourable hydrogeological conditions; the mean hydraulic conductivity of aquifer materials (sand and gravel) is 18.98 m/day. Moreover, there is a hydraulic connection between canal and aquifer; under steady conditions, the canal feeds the aquifer. Using different tracers, such as Cl, EC, Sr and SO<sub>4</sub>, the average bank filtration share is in excess of 95%. BF has reduced the particulates (turbidity) by 96%, total coliform by 99 % and total organic carbon (TOC) expressed as ultra-violet absorbance at 254 wavelengths (UVA254) by 44%. In addition, BF reduces concentrations of disinfection by-products due to its ability to remove organic matter. The potential degradation of TOC in the canal bed sediments may cause the release of iron (Fe) and manganese (Mn) to the bank filtrate water; this process is exaggerated during low-flow periods. Compared to conventional water treatment, BF is a cost-effective green technology, because no chemicals are used and no waste products are generated.</p> </abstract>ARTICLEtrue and palaeogeographical peculiarities of the Adamów Graben area, central Poland<abstract> <title style='display:none'>Abstract</title> <p>From a geological and palaeogeographical point of view, the area of the Adamów Graben in the vicinity of Turek ranks amongst the best known in central Poland, with several opencast mines located here where lignite was exploited for 57 years. These large-surface exposures provide a good opportunity for detailed geological studies of strata of Late Cretaceous to Holocene age. However, the present research focuses mainly on those deposits, forms and structures that have been most thoroughly examined and are best exposed. These are Cretaceous marls and gaizes, Paleogene ‘blue clays’ and the ‘Koźmin Gravels’, Neogene sandstones, as well as the Quaternary glacial ‘Lake Koźmin’, involutions and ‘Koźmin Las’. Some of these, e.g., the ‘Koźmin Gravels’ and ‘Koźmin Las’, are not known from other Polish territories. Furthermore, results obtained by the authors over a period of nearly 30 years also include data on palaeogeographical changes across some Cenozoic intervals, especially during the early Oligocene and late Weichselian.</p> </abstract>ARTICLEtrue hydrology and climate variability, monitoring, modelling, adaptation and mitigation, by A. Melesse, W. Abtew & G. Senay (Eds.), 2019. Elsevier Inc., Amsterdam. 580 pages. Paperback: price $170.00, ISBN 9780128159989 plate boundaries and fracture zones, by J.C. Duarte (Ed.), 2019. Elsevier Inc., Amsterdam. 478 pages. Paperback: price €137,55, ISBN 9780128120644., Campi Flegrei and Campanian volcanism, by Benedetto De Vivo, Harvey E. Belkin and Giuseppe Rolandi (Eds.), 2019. Elsevier Inc., Amsterdam. 520 pages. Paperback: price $175.00, ISBN 9780128164549 of the depositional sedimentary environment of Oligocene deposits (Qom Formation) in the Qom Basin (northern Tethyan seaway), Iran<abstract><title style='display:none'>Abstract</title><p>During the Rupelian–Chattian, the Qom Basin (northern seaway basin) was located between the Paratethys in the north and the southern Tethyan seaway in the south. The Oligocene deposits (Qom Formation) in the Qom Basin have been interpreted for a reconstruction of environmental conditions during deposition, as well as of the influence of local fault activities and global sea level changes expressed within the basin. We have also investigated connections between the Qom Basin and adjacent basins. Seven microfacies types have been distinguished in the former. These microfacies formed within three major depositional environments, i.e., restricted lagoon, open lagoon and open marine. Strata of the Qom Formation are suggested to have been formed in an open-shelf system. In addition, the deepening and shallowing patterns noted within the microfacies suggest the presence of three third-order sequences in the Bijegan area and two third-order depositional sequences and an incomplete depositional sequence in the Naragh area. Our analysis suggests that, during the Rupelian and Chattian stages, the depositional sequences of the Qom Basin were influenced primarily by local tectonics, while global sea level changes had a greater impact on the southern Tethyan seaway and Paratethys basins. The depositional basins of the Tethyan seaway (southern Tethyan seaway, Paratethys Basin and Qom Basin) were probably related during the Burdigalian to Langhian and early Serravallian.</p></abstract>ARTICLEtrue Horner in Bonn 1831–1833, finding loess and being incorporated into Lyell’s Loess Legion<abstract><title style='display:none'>Abstract</title><p>Leonard Horner (1785–1864) was a pioneer in the study of loess. His 1836 paper on the geology of Bonn contained detailed descriptions of loess in the Rhine valley. He identified and presented loess as an interesting material for geological study. He investigated loess in the crater of the Rodderberg with Charles Lyell in 1833. He presented the first significant paper on loess in Britain in 1833, but it was not published until 1836. With the assistance of G.A. Goldfuss and J.J. Noegerath he conducted early studies of the Siebengebirge and published the first geological map of the region, and the first picture of loess, at Rhondorf by the Drachenfels. He became the eleventh person to be included in the list of loess scholars which Charles Lyell published in volume 3 of the <italic>Principles of Geology</italic>. These were Leonhard, Bronn, Boue, Voltz, Steininger, Merian, Rozet, Hibbert in 1833, Noeggerath, von Meyer in 1835, Horner in 1837. Horner arrived after the publication of his studies on the loess at Bonn in 1836.</p></abstract>ARTICLEtrue