摘要:

Inarticulate brachiopods are described from the Upper Viruan (Middle Ordovician) and Lower Harjuan (Upper Ordovician) limestones in Gullhögen quarry, Västergötland, southern Sweden. Sixteen species of inarticulate brachiopods (seven named, six of which are new) are assigned to 14 genera (13 named, one of which is new). The lingulids are treated under open nomenclature. One new acrotretacean genus (Rhinotreta) is described as are the acrotretacean speciesHisingerella tenuis, Conotreta? orbicularis, Veliseptum strictum, Rhinotreta muscularis, Torynelasma? curvata and T.? plana.The stratigraphy of the Middle-Upper Ordovician boundary interval in Västergötland is briefly discussed.

ISSN:0016-786X    

DOI:10.1080/11035898609452633

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The present studies in the northwesternmost part of the Western Gneiss Region, Norway, have demonstrated the existence of previously unknown metasediments and metavolcanics in the Caledonian nappe units. Tectonic and metamorphic breaks as well as lithological differences separate these units from the underlying migmatized gneissic granites and granodiorites. Structural concordance between basement and cover developed as a result of high strain induced by nappe translation. An intense interfolding of basement and cover units postdated the thrusting event. Metamorphic and lithological contrasts in the area are generally preserved. Garnet-biotite thermometry data suggest that the temperatures during post-thrusting metamorphism did not exceed 600°C. Later movements were cataclastic in character and often occurred parallel to older thrust planes.

ISSN:0016-786X    

DOI:10.1080/11035898609452634

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Betechtinite and cobalt pentlandite, two minerals new for Långban, were observed coexisting with chalcocite, bornite, sphalerite, galena, and magnetite in a serpentinized skarn. Magnetite occurs in two generations, as euhedral crystals and as fracture fillings. This feature plus the textural relations of sulfides suggest an oxidation at very low temperature. The presence of chalcocite, bornite and minor amounts of native bismuth, and the absence of pyrite indicate a low sulfur activity during crystallization of these sulfides.

ISSN:0016-786X    

DOI:10.1080/11035898609452635

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

ISSN:0016-786X    

DOI:10.1080/11035898609452636

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Rb-Sr isotope data of whole-rock samples and apatites from the Hällefors composite dyke, south central Sweden, are presented and discussed. A good fit of several whole-rock points on a 1000 Ma line suggests a homogeneous Rb-Sr composition along the Hällefors dyke. The obtained data (age = 1001 ± 8 Ma, initial Sr ratio = 0.7103 ± 0.0003 and MSWD = 2.84) most likely reflect the low-grade metamorphism or alteration to which the rocks of the dyke were subjected. Several factors, besides sample inhomogencity, are suggested to explain the scattering of the remaining whole-rock samples around the 1000 Ma line: (a) variations inherited from the primary distribution of Sr and Rb in the different components of the dyke, (b) variations due to sampling within more altered domains of the dyke, (c) inheritance of the Sr isotope ratio from the country-rock gneiss. Two apatite separates of different rock types give a mean87Sr/86Sr ratio of 0.70505 ± 0.00043, believed to reflect the initial Sr ratio of the Hällefors system.

ISSN:0016-786X    

DOI:10.1080/11035898609452637

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Rb-Sr whole-rock dating of the Eringsboda and Klagstorp granites in southern Sweden yields an isochron age of 1358 ± 114 Ma with initial87Sr/86Sr ratio of 0.7064. These values, as well as field and petrographical-geochemical data, are in harmony with similar data for rocks from the Karlshamn granite group, southern Sweden.

ISSN:0016-786X    

DOI:10.1080/11035898609452638

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Organic sediments taken from eight south Swedish lakes show a marked decrease in the δ13C values at approximately the Pleistocene-Holocene chronostratigraphic boundary. The result of a survey of different factors influencing the stable carbon isotope ratio in the organic component in lake sediments is presented and discussed for the special case at hand, namely a change from late-glacial to post-glacial environmental conditions for lakes with moderately soft water.

ISSN:0016-786X    

DOI:10.1080/11035898609452639

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The Segmon granite is one of the younger ensialic granites which intruded the Southwestern Gneiss Region of the Baltic Shield. The granite is red, medium-grained and strongly foliated, and has a zircon age of 1249 Ma. The geochemical characterization is based on nineteen rock samples. Even though the analyses show considerably heterogeneous compositions, regular interelement variations among the immobile elements are found. The granite is alkali-calcic and metaluminous. REE analyses show distinctly enriched LREE patterns, less enriched HREE patterns, and strong negative Eu anomalies.

ISSN:0016-786X    

DOI:10.1080/11035898609452640

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Fossil frost fissures are frequent in southern Sweden. Except those formed in an intermorainic position they are all caused by the periglacial environment at the time of deglaciation. The different types of these fossil frost fissures are described, and examples are taken from different areas in southern Sweden.

ISSN:0016-786X    

DOI:10.1080/11035898609452641

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

ISSN:0016-786X    

DOI:10.1080/11035898609452642

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor