The mineralogy and geochemistry of the ela y fraction ( <2f.!) of the Quater nary deposits in... more The mineralogy and geochemistry of the ela y fraction ( <2f.!) of the Quater nary deposits in the Numedal area, southern Norway, have been studied. The Numedal clays contain considerable amounts of illite, but chlorite, vermiculite, mixed layer minerals, quartz, microcline, and acid plagioclase are also usually found. Amphibole is present in most of the samples. Traces of montmorillonite are occasionally found. During weathering the amount of vermiculite and mixed layered illite vermiculite increases at the expense of trioctahedral illite and chlorite. The average chemical composition of the clay fraction ( <2!!) corresponds to that of coarse clays. The clay material is only slightly weathered, and the residual indexes correspond to those of fresh rocks. Comparison of the mineralogical and chemical data shows the physico chemical variations during weathering, transport and sedimentation, and the composition of the parent material to be of significant importance to the clay ...
A description is given of overconsolidated sub-tiU day sediments situated about 260 m a.s.l., i.e... more A description is given of overconsolidated sub-tiU day sediments situated about 260 m a.s.l., i.e. 90 m above the 1ocal marine limit ofi the last deglaciation. The clay sediments contain neither macro- nor micro-fossils. Textural, mineralogical and geochemical investigations, strongly supported by the Ce deficient lanthanide abundance pattern, indicate marine depositional environment. The clay sediments are assumed to be of Middle-Weichseli an age and are thus correlated with the Sandnes Interstadial, described from SW-Norway, and its analogues. E. Roaldset, Institutt for geologi, Universitetet i Oslo, Boks 1047, Blindern, Oslo 3, Norway. In the Numedal river basin sub-till sediments have previously been described from the north em parts of the area (Roaldset 1973a, Rosenqvist 1973). This paper presents data on the ftrst sub till clays in the lower part of the Numedal river basin, where in 1973 in the valley Herlandsdalen, overconsolidated sub-till clays situated 260 m a.s.l. (Fig...
DURING our investigations of the genesis of Scandinavian glacial loams and clays, we have examine... more DURING our investigations of the genesis of Scandinavian glacial loams and clays, we have examined some gneisses in upper Numedalen, Eastern Norway. These rocks have undoubtedly been exposed to glacial erosion, but they seem to represent deeper parts of the preglacial (tertiary) weathering profile. We are particularly interested in the rare Earth elements (yttrium + lanthanides) which these rocks contain. The determinations were carried out by spark mass spectrometer1, which is well suited for all rare Earth elements except Tm. The micaceous fractions were found to be extremely enriched in lanthanides. Whereas micas of magmatic and highly metamorphosed rocks normally have lower rare Earth content than the host rock, we have found the opposite in these weathered gneisses. Thus a slightly weathered mylonite gneiss (from Smadola) has a total rare Earth content of 525 p.p.m. The light mica fraction (degraded muscovite), which made up approximately 2% of the rock, contained 3,755 p.p.m. and the dark mica fraction (chlorite and vermiculized biotite), which made up approximately 8% of the rock, contained 1,584 p.p.m. of rare Earth elements.
Decompaction may be defined as a process to reconstruct the palaeothickness and the palaeoporosit... more Decompaction may be defined as a process to reconstruct the palaeothickness and the palaeoporosity distributions of a sedimentary column. This process is normally realized by computation of pore volume reduction in sedimentary histories (Perrier and Quiblier 1974). Decompaction modelling has been a subject of interest because of its uses in quantitative geohistory analysis, reservoir evaluation and fluid migration studies in sedimentary basins (Sclater and Christie 1980; Bessis 1985; Bertram and Milton 1989). Petroleum geologists, while preparing palaeogeographic or palaeostructural reconstructions, must consider how thicknesses of strata were modified during depositional history.
This paper reports the organic constitution of the CO3 chondrites identified by 4D TOFMS in order... more This paper reports the organic constitution of the CO3 chondrites identified by 4D TOFMS in order to decipher the composition, structure and alteration history of the CO3 parent asteroid.
Geological Society, London, Special Publications, 1986
Summary A prograding sequence of near shore sediments is identified at the border of the northern... more Summary A prograding sequence of near shore sediments is identified at the border of the northern North Sea plateau (water depth 135 m) and the western slope of the Norwegian Trench. In Late Weichselian time (probably about 15 000 years bp) the relative sea level was approximately 180 m lower than today. During this low sea-level stand, the older consolidated glaciomarine sediments in the slope area were exposed to coastal erosion, leading to a prograding unit of sand fining outwards to silt and clay. During rising sea-level the coastal erosion gradually reached a lodgement till deposited at the top of the plateau, resulting in coarser sediments such as stones and gravel, fining outwards to sand down the slope. The plateau area was transgressed shortly after 13 000 years bp.
Mass spectrometric analyses for rare earth elements (REE) have been carried out on some Precambri... more Mass spectrometric analyses for rare earth elements (REE) have been carried out on some Precambrian mica schists, gneisses and granites from the Precambrian Numedal area, Norway and on their phyllosilicates. The rocks, which are metamorphosed in the upper greenschist to amphibolite facies, were originally partly sedimentary, partly magmatic. The total REE contents for rocks varies from 145 to 761 ppm. An average of 16 phyllosilicate samples gave 417 ppm REE (max. of 1809 ppm, min. of ca. 50 ppm). Coexisting light and dark phyllosilicates have similar abundances of REE. For the micas of high REE content most of the REE was extractable by rinsing with EDTA. The data thus support the possibility of an extensive adsorption of REE ions on micaceous minerals. The REE distribution patterns do not provide a clear distinction between the sedimentary and magmatic origin for the rocks examined.
Fourteen rare-earth elements (REE) have been determined in metavolcanics and metagabbros from the... more Fourteen rare-earth elements (REE) have been determined in metavolcanics and metagabbros from the island of Leka, Norway. The overall REE content of these rocks ranges from about 3ppm, with strong light REE depletion, for the metagabbros to 170ppm with light REE enrichment, for porphyritic greenstones and pillow lavas. Based on regional geological features, lithology, and the REE abundances it is concluded that rocks of the island Leka constitute a part of an ophiolite complex.
The mineralogy and geochemistry of the ela y fraction ( <2f.!) of the Quater nary deposits in... more The mineralogy and geochemistry of the ela y fraction ( <2f.!) of the Quater nary deposits in the Numedal area, southern Norway, have been studied. The Numedal clays contain considerable amounts of illite, but chlorite, vermiculite, mixed layer minerals, quartz, microcline, and acid plagioclase are also usually found. Amphibole is present in most of the samples. Traces of montmorillonite are occasionally found. During weathering the amount of vermiculite and mixed layered illite vermiculite increases at the expense of trioctahedral illite and chlorite. The average chemical composition of the clay fraction ( <2!!) corresponds to that of coarse clays. The clay material is only slightly weathered, and the residual indexes correspond to those of fresh rocks. Comparison of the mineralogical and chemical data shows the physico chemical variations during weathering, transport and sedimentation, and the composition of the parent material to be of significant importance to the clay ...
A description is given of overconsolidated sub-tiU day sediments situated about 260 m a.s.l., i.e... more A description is given of overconsolidated sub-tiU day sediments situated about 260 m a.s.l., i.e. 90 m above the 1ocal marine limit ofi the last deglaciation. The clay sediments contain neither macro- nor micro-fossils. Textural, mineralogical and geochemical investigations, strongly supported by the Ce deficient lanthanide abundance pattern, indicate marine depositional environment. The clay sediments are assumed to be of Middle-Weichseli an age and are thus correlated with the Sandnes Interstadial, described from SW-Norway, and its analogues. E. Roaldset, Institutt for geologi, Universitetet i Oslo, Boks 1047, Blindern, Oslo 3, Norway. In the Numedal river basin sub-till sediments have previously been described from the north em parts of the area (Roaldset 1973a, Rosenqvist 1973). This paper presents data on the ftrst sub till clays in the lower part of the Numedal river basin, where in 1973 in the valley Herlandsdalen, overconsolidated sub-till clays situated 260 m a.s.l. (Fig...
DURING our investigations of the genesis of Scandinavian glacial loams and clays, we have examine... more DURING our investigations of the genesis of Scandinavian glacial loams and clays, we have examined some gneisses in upper Numedalen, Eastern Norway. These rocks have undoubtedly been exposed to glacial erosion, but they seem to represent deeper parts of the preglacial (tertiary) weathering profile. We are particularly interested in the rare Earth elements (yttrium + lanthanides) which these rocks contain. The determinations were carried out by spark mass spectrometer1, which is well suited for all rare Earth elements except Tm. The micaceous fractions were found to be extremely enriched in lanthanides. Whereas micas of magmatic and highly metamorphosed rocks normally have lower rare Earth content than the host rock, we have found the opposite in these weathered gneisses. Thus a slightly weathered mylonite gneiss (from Smadola) has a total rare Earth content of 525 p.p.m. The light mica fraction (degraded muscovite), which made up approximately 2% of the rock, contained 3,755 p.p.m. and the dark mica fraction (chlorite and vermiculized biotite), which made up approximately 8% of the rock, contained 1,584 p.p.m. of rare Earth elements.
Decompaction may be defined as a process to reconstruct the palaeothickness and the palaeoporosit... more Decompaction may be defined as a process to reconstruct the palaeothickness and the palaeoporosity distributions of a sedimentary column. This process is normally realized by computation of pore volume reduction in sedimentary histories (Perrier and Quiblier 1974). Decompaction modelling has been a subject of interest because of its uses in quantitative geohistory analysis, reservoir evaluation and fluid migration studies in sedimentary basins (Sclater and Christie 1980; Bessis 1985; Bertram and Milton 1989). Petroleum geologists, while preparing palaeogeographic or palaeostructural reconstructions, must consider how thicknesses of strata were modified during depositional history.
This paper reports the organic constitution of the CO3 chondrites identified by 4D TOFMS in order... more This paper reports the organic constitution of the CO3 chondrites identified by 4D TOFMS in order to decipher the composition, structure and alteration history of the CO3 parent asteroid.
Geological Society, London, Special Publications, 1986
Summary A prograding sequence of near shore sediments is identified at the border of the northern... more Summary A prograding sequence of near shore sediments is identified at the border of the northern North Sea plateau (water depth 135 m) and the western slope of the Norwegian Trench. In Late Weichselian time (probably about 15 000 years bp) the relative sea level was approximately 180 m lower than today. During this low sea-level stand, the older consolidated glaciomarine sediments in the slope area were exposed to coastal erosion, leading to a prograding unit of sand fining outwards to silt and clay. During rising sea-level the coastal erosion gradually reached a lodgement till deposited at the top of the plateau, resulting in coarser sediments such as stones and gravel, fining outwards to sand down the slope. The plateau area was transgressed shortly after 13 000 years bp.
Mass spectrometric analyses for rare earth elements (REE) have been carried out on some Precambri... more Mass spectrometric analyses for rare earth elements (REE) have been carried out on some Precambrian mica schists, gneisses and granites from the Precambrian Numedal area, Norway and on their phyllosilicates. The rocks, which are metamorphosed in the upper greenschist to amphibolite facies, were originally partly sedimentary, partly magmatic. The total REE contents for rocks varies from 145 to 761 ppm. An average of 16 phyllosilicate samples gave 417 ppm REE (max. of 1809 ppm, min. of ca. 50 ppm). Coexisting light and dark phyllosilicates have similar abundances of REE. For the micas of high REE content most of the REE was extractable by rinsing with EDTA. The data thus support the possibility of an extensive adsorption of REE ions on micaceous minerals. The REE distribution patterns do not provide a clear distinction between the sedimentary and magmatic origin for the rocks examined.
Fourteen rare-earth elements (REE) have been determined in metavolcanics and metagabbros from the... more Fourteen rare-earth elements (REE) have been determined in metavolcanics and metagabbros from the island of Leka, Norway. The overall REE content of these rocks ranges from about 3ppm, with strong light REE depletion, for the metagabbros to 170ppm with light REE enrichment, for porphyritic greenstones and pillow lavas. Based on regional geological features, lithology, and the REE abundances it is concluded that rocks of the island Leka constitute a part of an ophiolite complex.
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Papers by Elen Roaldset