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Volume 28 (2022): Edition 3 (December 2022)

Volume 28 (2022): Edition 2 (August 2022)

Volume 28 (2022): Edition 1 (April 2022)

Volume 27 (2021): Edition 3 (December 2021)

Volume 27 (2021): Edition 2 (August 2021)

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Volume 26 (2020): Edition 3 (December 2020)

Volume 26 (2020): Edition 2 (August 2020)

Volume 26 (2020): Edition 1 (April 2020)

Volume 25 (2019): Edition 3 (December 2019)

Volume 25 (2019): Edition 2 (August 2019)

Volume 25 (2019): Edition 1 (April 2019)

Volume 24 (2018): Edition 3 (December 2018)

Volume 24 (2018): Edition 2 (August 2018)

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Volume 22 (2016): Edition 3 (September 2016)

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Volume 21 (2015): Edition 4 (December 2015)

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Volume 21 (2015): Edition 2 (June 2015)

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Volume 20 (2014): Edition 4 (December 2014)

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Volume 19 (2013): Edition 4 (December 2013)

Volume 19 (2013): Edition 3 (September 2013)

Volume 19 (2013): Edition 1-2 (May 2013)
Heavy-mineral analysis as a tool in earth-scientific research

Volume 18 (2012): Edition 4 (December 2012)

Volume 18 (2012): Edition 3 (October 2012)

Volume 18 (2012): Edition 2 (August 2012)

Volume 18 (2012): Edition 1 (March 2012)

Volume 17 (2011): Edition 4 (December 2011)

Volume 17 (2011): Edition 3 (September 2011)

Volume 17 (2011): Edition 2 (June 2011)

Volume 17 (2011): Edition 1 (April 2011)

Volume 16 (2010): Edition 4 (December 2010)

Volume 16 (2010): Edition 3 (October 2010)

Volume 16 (2010): Edition 2 (June 2010)

Volume 16 (2010): Edition 1 (April 2010)

Volume 15 (2009): Edition 3-4 (December 2009)

Détails du magazine
Format
Magazine
eISSN
2080-6574
Première publication
24 Dec 2009
Période de publication
3 fois par an
Langues
Anglais

Chercher

Volume 28 (2022): Edition 2 (August 2022)

Détails du magazine
Format
Magazine
eISSN
2080-6574
Première publication
24 Dec 2009
Période de publication
3 fois par an
Langues
Anglais

Chercher

8 Articles
Accès libre

Reconsidering the glaciogenic origin of Gondwana diamictites of the Dwyka Group, South Africa

Publié en ligne: 13 Oct 2022
Pages: 83 - 113

Résumé

Abstract

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 in-situ 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.

Mots clés

  • Surface microtexture
  • sediment gravity flow
  • Late Palaeozoic Ice Age
  • pavement
  • Nooitgedacht
Accès libre

Frequency magnitude distribution and spatial correlation dimension of earthquakes in north-east Himalaya and adjacent regions

Publié en ligne: 13 Oct 2022
Pages: 115 - 128

Résumé

Abstract

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 (Dc) 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 Dc 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 Dc 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 > 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 Dc values refer to the heterogeneity of the seismogenic sources.

Mots clés

  • North-east India
  • b-value
  • maximum likelihood estimation
  • correlation dimension
Accès libre

Iron-bearing phases affecting the colour of upper Neogene clayey sediments from Dymaczewo Stare, west-central Poland

Publié en ligne: 13 Oct 2022
Pages: 129 - 139

Résumé

Abstract

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 57Fe Mössbauer spectroscopy (57Fe-MS). The PXRD-based phase analysis has demonstrated the variable compositions of samples, consisting of, inter alia, 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.

Mots clés

  • mineral composition
  • powder X-ray diffraction (PXRD)
  • iron minerals
  • Fe Mössbauer spectroscopy (Fe-MS)
  • ‘Poznań Clays’
  • Mio-Pliocene
Accès libre

Analysis of the geotouristic potential of geosites in Divjakë-Karavasta National Park, Albania

Publié en ligne: 13 Oct 2022
Pages: 141 - 155

Résumé

Abstract

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.

Mots clés

  • Geodiversity
  • geoheritage
  • protected area
  • GAM model
  • SPSS analyses
Accès libre

Against steady state

Publié en ligne: 13 Oct 2022
Pages: 157 - 168

Résumé

Abstract

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.

Mots clés

  • understanding nature
  • models in geology
  • uniformitarianism and catastrophism
  • data interpretation
  • physical models
Accès libre

Book reviews: Structural geology: principles, concepts, and problems (3rd edition)

Publié en ligne: 13 Oct 2022
Pages: 169 - 172

Résumé

Accès libre

Book reviews: Introduction to environmental modelling

Publié en ligne: 13 Oct 2022
Pages: 173 - 174

Résumé

Accès libre

Book reviews: Volcanoes: a very short introduction

Publié en ligne: 13 Oct 2022
Pages: 175 - 177

Résumé

8 Articles
Accès libre

Reconsidering the glaciogenic origin of Gondwana diamictites of the Dwyka Group, South Africa

Publié en ligne: 13 Oct 2022
Pages: 83 - 113

Résumé

Abstract

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 in-situ 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.

Mots clés

  • Surface microtexture
  • sediment gravity flow
  • Late Palaeozoic Ice Age
  • pavement
  • Nooitgedacht
Accès libre

Frequency magnitude distribution and spatial correlation dimension of earthquakes in north-east Himalaya and adjacent regions

Publié en ligne: 13 Oct 2022
Pages: 115 - 128

Résumé

Abstract

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 (Dc) 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 Dc 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 Dc 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 > 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 Dc values refer to the heterogeneity of the seismogenic sources.

Mots clés

  • North-east India
  • b-value
  • maximum likelihood estimation
  • correlation dimension
Accès libre

Iron-bearing phases affecting the colour of upper Neogene clayey sediments from Dymaczewo Stare, west-central Poland

Publié en ligne: 13 Oct 2022
Pages: 129 - 139

Résumé

Abstract

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 57Fe Mössbauer spectroscopy (57Fe-MS). The PXRD-based phase analysis has demonstrated the variable compositions of samples, consisting of, inter alia, 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.

Mots clés

  • mineral composition
  • powder X-ray diffraction (PXRD)
  • iron minerals
  • Fe Mössbauer spectroscopy (Fe-MS)
  • ‘Poznań Clays’
  • Mio-Pliocene
Accès libre

Analysis of the geotouristic potential of geosites in Divjakë-Karavasta National Park, Albania

Publié en ligne: 13 Oct 2022
Pages: 141 - 155

Résumé

Abstract

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.

Mots clés

  • Geodiversity
  • geoheritage
  • protected area
  • GAM model
  • SPSS analyses
Accès libre

Against steady state

Publié en ligne: 13 Oct 2022
Pages: 157 - 168

Résumé

Abstract

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.

Mots clés

  • understanding nature
  • models in geology
  • uniformitarianism and catastrophism
  • data interpretation
  • physical models
Accès libre

Book reviews: Structural geology: principles, concepts, and problems (3rd edition)

Publié en ligne: 13 Oct 2022
Pages: 169 - 172

Résumé

Accès libre

Book reviews: Introduction to environmental modelling

Publié en ligne: 13 Oct 2022
Pages: 173 - 174

Résumé

Accès libre

Book reviews: Volcanoes: a very short introduction

Publié en ligne: 13 Oct 2022
Pages: 175 - 177

Résumé

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