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Heavy-mineral analysis as a tool in earth-scientific research

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Journal Details
Format
Journal
eISSN
2080-6574
ISSN
1426-8981
First Published
24 Dec 2009
Publication timeframe
3 times per year
Languages
English

Search

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

Journal Details
Format
Journal
eISSN
2080-6574
ISSN
1426-8981
First Published
24 Dec 2009
Publication timeframe
3 times per year
Languages
English

Search

4 Articles
Open Access

Relationships between microstructural features and mesoscopic fracture density in a Pleistocene till (Konin area, central Poland)

Published Online: 26 Apr 2010
Page range: 3 - 26

Abstract

Relationships between microstructural features and mesoscopic fracture density in a Pleistocene till (Konin area, central Poland)

The qualitative and quantitative characteristics of microstructures in a till were analysed with SEM; it was also investigated whether the results depend on the till's mesostructural characteristics. The till, exposed in a few open-cast browncoal mines near Konin in central Poland, is cut by numerous fractures which correspond to Riedel shear patterns, P-type structures and C-S type foliations. The fractures developed as a result of simple shearing induced by movement of the base of the Odranian ice sheet. On the basis of fracture density, two till types are distinguished: coarsely-brecciated till (wide spacing of fractures) and finely-brecciated till (closely spaced fractures). It is found that the fracture density is reflected in the microstructure of the till. The finely-brecciated till is characterised by a high porosity and has predominantly anisometric and fissure-like pores that also show a more clearly preferred orientation than the pores in the coarsely-brecciated till. In contrast, the coarsely-brecciated till has anisometric pores that show a less preferential orientation. The porosity of the coarsely-brecciated till is lower than in the finely-brecciated till.

The finely-brecciated till probably represents a strongly deformed deposit, related in some cases to zones developed along thrusts that cut the till. Positive correlation between the porosity, the spatial arrangement of pores, and the density of fractures suggests a synsedimentary origin of the shear strain. This strain was accommodated by a particulate flow developed within both wide, pervasive zones and narrow, localised zones. The hydraulic conditions within the subglacial shear zone controlled rheological differences within the till during deformation and thus influenced the degree of the microstructure alteration.

Keywords

  • till
  • shear fractures
  • microstructures
  • SEM
  • rheology
Open Access

Sedimentology of a Permian playa lake: the Boda Claystone Formation, Hungary

Published Online: 26 Apr 2010
Page range: 27 - 41

Abstract

Sedimentology of a Permian playa lake: the Boda Claystone Formation, Hungary

The Upper Permian Boda Claystone Formation (BCF) in SW Hungary has been previously been identified as a saline lake deposit. A country-wide screening found this 800-1000 m thick succession the most suitable for the disposal of high-level radioactive waste in Hungary, and research into this formation has consequently been intensified since. The investigations included a detailed study of the sedimentological characteristics. Data obtained by mapping of the 25 km2 outcrop area of the formation and from more than 40 boreholes were processed. The sedimentary structures were investigated on outcrop to microscopic scales, and cycles in the succession were interpreted.

The main lithofacies, sedimentary structures and ichnofossils are presented. They indicate that the major part of the succession was deposited in a playa mudflat and is not of lacustrine origin in a strict sense. The lake sediments are represented by laminated and ripple-marked/flaser-type cross-laminated claystones and siltstones and by massive dolomites; trace fossils include crawling traces and burrows. Partial or complete drying out of the lake commonly occurred after the formation of carbonate mud by evaporation. Periodic fluvial influx is recorded by cross-bedded sandstones and unsorted gravelly sandstones of up to pebble-sized angular grains. Fenestral and stromatolitic structures reflect the repeated appearance of playa mudflat conditions. The silty claystones, which compose the major part of the succession, lost their primary structures due to pedogenic processes and indicate prolonged subaerial intervals with soil formation and only ephemeral inundations. The presence of pedogenic carbonate concretions supports the interpretation of an arid climate and a relatively shallow groundwater table. Drying-out events shown by desiccation cracks and authigenic breccias can be traced all over the succession.

The various facies form small-scale sedimentary cycles showing a shallowing-upward trend and the growing influence of aridity and subaerial exposure.

Keywords

  • Late Permian
  • Boda Claystone Formation
  • Hungary
  • playa
Open Access

Engineering-geological and geotechnical investigations for risk assessment of the University Olympic Village in Izmir (Turkey)

Published Online: 26 Apr 2010
Page range: 43 - 57

Abstract

Engineering-geological and geotechnical investigations for risk assessment of the University Olympic Village in Izmir (Turkey)

The Metropolitan Municipality of Izmir (Turkey) designated a steeply inclined area for the construction of buildings to house the participants of the Izmir University Olympic Games. Before the construction activities could start, engineering geological and geotechnical investigations had to be carried out in order to establish which zones in the area were suitable for safe constructions. Seismic studies, borings and laboratory tests yielded the data, which were used for preparing five hazard maps in a GIS environment. The construction activities based on the results of this complex investigation appeared successful. The engineering geological investigations included geotechnical measurements on core samples obtained from the boreholes (core drilling) and laboratory testing. The rock-quality designation (RQD%) values of the rock units were determined and used in the rock-mass classification (rock-mass rating method) as an input parameter and in the calculation of the bearing capacity of the various rock units. Geophysical surveys were carried out to determine the seismic velocity of the rocks at the site. A short overview is provided of the main problems that had to be dealt with, and of the successive steps taken to solve the engineering-geological problems. Determination of these problems is necessary for adequate land-use planning and construction activities.

Keywords

  • engineering geology
  • hazard maps
  • bearing capacity
  • Izmir
  • Turkey
Open Access

The Kaali crater field and other geosites of Saaremaa Island (Estonia): the perspectives for a geopark

Published Online: 26 Apr 2010
Page range: 59 - 68

Abstract

The Kaali crater field and other geosites of Saaremaa Island (Estonia): the perspectives for a geopark

The Island of Saaremaa in Estonia offers highly spectacular geological features that belong to the most interesting in the Baltic Sea area. A unique geological monument on the island is the Kaali meteorite-crater field, formed by nine meteorite impacts. There are also attractive coastal cliffs, huge erratics, alvars (limestone areas covered by a very thin soil) and well-developed glacial and marine landforms. Limestone cliffs and shingle beaches abound with Silurian fossils and offer great opportunities to fossil collectors. The island is a prospective geopark. During the past few years, the geology of the island has become an intensely studied object of Estonian and Polish geologists.

Keywords

  • geopark
  • geosites
  • meteorite-crater field
  • Saaremaa Island
  • Estonia
4 Articles
Open Access

Relationships between microstructural features and mesoscopic fracture density in a Pleistocene till (Konin area, central Poland)

Published Online: 26 Apr 2010
Page range: 3 - 26

Abstract

Relationships between microstructural features and mesoscopic fracture density in a Pleistocene till (Konin area, central Poland)

The qualitative and quantitative characteristics of microstructures in a till were analysed with SEM; it was also investigated whether the results depend on the till's mesostructural characteristics. The till, exposed in a few open-cast browncoal mines near Konin in central Poland, is cut by numerous fractures which correspond to Riedel shear patterns, P-type structures and C-S type foliations. The fractures developed as a result of simple shearing induced by movement of the base of the Odranian ice sheet. On the basis of fracture density, two till types are distinguished: coarsely-brecciated till (wide spacing of fractures) and finely-brecciated till (closely spaced fractures). It is found that the fracture density is reflected in the microstructure of the till. The finely-brecciated till is characterised by a high porosity and has predominantly anisometric and fissure-like pores that also show a more clearly preferred orientation than the pores in the coarsely-brecciated till. In contrast, the coarsely-brecciated till has anisometric pores that show a less preferential orientation. The porosity of the coarsely-brecciated till is lower than in the finely-brecciated till.

The finely-brecciated till probably represents a strongly deformed deposit, related in some cases to zones developed along thrusts that cut the till. Positive correlation between the porosity, the spatial arrangement of pores, and the density of fractures suggests a synsedimentary origin of the shear strain. This strain was accommodated by a particulate flow developed within both wide, pervasive zones and narrow, localised zones. The hydraulic conditions within the subglacial shear zone controlled rheological differences within the till during deformation and thus influenced the degree of the microstructure alteration.

Keywords

  • till
  • shear fractures
  • microstructures
  • SEM
  • rheology
Open Access

Sedimentology of a Permian playa lake: the Boda Claystone Formation, Hungary

Published Online: 26 Apr 2010
Page range: 27 - 41

Abstract

Sedimentology of a Permian playa lake: the Boda Claystone Formation, Hungary

The Upper Permian Boda Claystone Formation (BCF) in SW Hungary has been previously been identified as a saline lake deposit. A country-wide screening found this 800-1000 m thick succession the most suitable for the disposal of high-level radioactive waste in Hungary, and research into this formation has consequently been intensified since. The investigations included a detailed study of the sedimentological characteristics. Data obtained by mapping of the 25 km2 outcrop area of the formation and from more than 40 boreholes were processed. The sedimentary structures were investigated on outcrop to microscopic scales, and cycles in the succession were interpreted.

The main lithofacies, sedimentary structures and ichnofossils are presented. They indicate that the major part of the succession was deposited in a playa mudflat and is not of lacustrine origin in a strict sense. The lake sediments are represented by laminated and ripple-marked/flaser-type cross-laminated claystones and siltstones and by massive dolomites; trace fossils include crawling traces and burrows. Partial or complete drying out of the lake commonly occurred after the formation of carbonate mud by evaporation. Periodic fluvial influx is recorded by cross-bedded sandstones and unsorted gravelly sandstones of up to pebble-sized angular grains. Fenestral and stromatolitic structures reflect the repeated appearance of playa mudflat conditions. The silty claystones, which compose the major part of the succession, lost their primary structures due to pedogenic processes and indicate prolonged subaerial intervals with soil formation and only ephemeral inundations. The presence of pedogenic carbonate concretions supports the interpretation of an arid climate and a relatively shallow groundwater table. Drying-out events shown by desiccation cracks and authigenic breccias can be traced all over the succession.

The various facies form small-scale sedimentary cycles showing a shallowing-upward trend and the growing influence of aridity and subaerial exposure.

Keywords

  • Late Permian
  • Boda Claystone Formation
  • Hungary
  • playa
Open Access

Engineering-geological and geotechnical investigations for risk assessment of the University Olympic Village in Izmir (Turkey)

Published Online: 26 Apr 2010
Page range: 43 - 57

Abstract

Engineering-geological and geotechnical investigations for risk assessment of the University Olympic Village in Izmir (Turkey)

The Metropolitan Municipality of Izmir (Turkey) designated a steeply inclined area for the construction of buildings to house the participants of the Izmir University Olympic Games. Before the construction activities could start, engineering geological and geotechnical investigations had to be carried out in order to establish which zones in the area were suitable for safe constructions. Seismic studies, borings and laboratory tests yielded the data, which were used for preparing five hazard maps in a GIS environment. The construction activities based on the results of this complex investigation appeared successful. The engineering geological investigations included geotechnical measurements on core samples obtained from the boreholes (core drilling) and laboratory testing. The rock-quality designation (RQD%) values of the rock units were determined and used in the rock-mass classification (rock-mass rating method) as an input parameter and in the calculation of the bearing capacity of the various rock units. Geophysical surveys were carried out to determine the seismic velocity of the rocks at the site. A short overview is provided of the main problems that had to be dealt with, and of the successive steps taken to solve the engineering-geological problems. Determination of these problems is necessary for adequate land-use planning and construction activities.

Keywords

  • engineering geology
  • hazard maps
  • bearing capacity
  • Izmir
  • Turkey
Open Access

The Kaali crater field and other geosites of Saaremaa Island (Estonia): the perspectives for a geopark

Published Online: 26 Apr 2010
Page range: 59 - 68

Abstract

The Kaali crater field and other geosites of Saaremaa Island (Estonia): the perspectives for a geopark

The Island of Saaremaa in Estonia offers highly spectacular geological features that belong to the most interesting in the Baltic Sea area. A unique geological monument on the island is the Kaali meteorite-crater field, formed by nine meteorite impacts. There are also attractive coastal cliffs, huge erratics, alvars (limestone areas covered by a very thin soil) and well-developed glacial and marine landforms. Limestone cliffs and shingle beaches abound with Silurian fossils and offer great opportunities to fossil collectors. The island is a prospective geopark. During the past few years, the geology of the island has become an intensely studied object of Estonian and Polish geologists.

Keywords

  • geopark
  • geosites
  • meteorite-crater field
  • Saaremaa Island
  • Estonia

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