ISSN:0016-786X    

DOI:10.1080/11035898009450853

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Fifty-one kilograms of limestones and dolomites, roughly 35% from the outcrop, 8% from cores, and the remainder from glacial erratics scattered around the Åland Archipelago, have produced several thousand Ordovician conodonts. Erratic materials range in age from Arenigian (‘orthoceratite limestone’) to upper Caradocian (‘Baltic limestone’). Most of these erratics probably were derived very locally and thereby provide some additional information for geologic mapping of the adjacent floor of the Gulf of Bothnia. In situ sedimentary rocks in Lumparn Bay may be the only post-Cambrian stratiform Paleozoic deposits in Finland. Like most of the ‘Baltic limestone’ erratics, the conodont abundance in these Lumparn limestones is generally quite low, but the outcropping upper part of the more than 80 m of carbonates is quite productive and substantiates a late Caradocian (upperAmorphognathus superbusZone) age, at least in part. Its nearest age equivalents appear to be the Kullsberg and Slandrom limestones in Sweden and the Nabalan Stage in Estonia. The bulk of the samples are highly bioturbated and dolomitized micrites with few body fossils and a sparse conodont fauna dominated by distacodontids, chieflyPanderodus.Environmentally, these observations suggest deposition on a hyper- to schizohaline carbonate bank that may have been, in part at least, intertidal. Preservation of the Paleozoic section in Lumparn seems best explained by the Lumparn basin being a meteorite impact structure.

ISSN:0016-786X    

DOI:10.1080/11035898009450854

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

ISSN:0016-786X    

DOI:10.1080/11035898009450855

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

An early phase of the Littorina transgression is14C dated at 6800–7000 B.P. (plant material at 2–3 m above sea level). It corresponds to the first Atlantic transgression in Blekinge and western Skåne. The highest mean water level of the Littorina Sea was at ca. 5 m above sea-level. By analogy with western Skåne and Blekinge it is suggested that this level was attained in the time range 5500-4500 B.P. During this interval the highest Littorina beach ridges were formed at 6.5–7 m. A gastropod fauna found in a lime gyttja overlain by the highest Littorina beach ridge includesDiscus ruderatus(but not D.rotundatus). The fauna is compared with a Recent to ‘sub-Recent’ fauna containingD. rotundatusbut lackingD. ruderatus. D. ruderatus(a boreo-alpine species today) might have persisted into the Atlantic stage or longer as a relict from a cooler climatic stage.

ISSN:0016-786X    

DOI:10.1080/11035898009450856

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

A magnetic anomaly in the Tåsjön-Ormsjön area of the Caledonian Front, central Sweden, has been studied. Its orientation discordant to Caledonian structures in the sedimentary cover requires a basement source probably related to a basic intrusion. Calculations of depth to the top of the magnetic source in the eastern part of the anomaly coincide well with depth to basement known from drillings. There is good agreement with new data from deep drilling further west in the Tåsjön area. This implies that the depth determination of ca. 600 m below sea level in the western area northwest of Lake Tåsjön probably indicates the surface of the crystalline basement beneath late Precambrian Risbäck Group sediments.

ISSN:0016-786X    

DOI:10.1080/11035898009450857

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

A Rb-Sr whole rock isochron for late tectonic granitic dykes intruding the high-grade Rödingsfjället Nappe in the Scandinavian Caledonides gives an age of 447±7 Ma and an initial87Sr/86Sr ratio of 0.7060±0.0004 (87Rb decay constant λ = 1.42 × 10−11a−1). The dykes cut the regional schistosity in the country rocks and are themselves only locally deformed by later movements. It is suggested that the Ordovician age gives a lower limit for the timing of regional metamorphism in the area. The initial Sr-ratio implies that the magma was probably derived by anatexis of greywackes.

ISSN:0016-786X    

DOI:10.1080/11035898009450858

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Staining of thin sections for quick identification of quartz, potash feldspar and plagioclase is usually done with sodium hexanitrocobaltate (III) and rhodizonic acid disodium salt. This method is unsatisfactory when the anorthite content of the plagioclase is low. A new method which makes it possible to stain the albite component of the plagioclase is described.

ISSN:0016-786X    

DOI:10.1080/11035898009450859

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

The Hanö Bay part of the Fennoscandian Border Zone has been investigated by means of seismic reflection profiling. These data have been interpreted on the basis of correlation with two offshore boreholes. Hanö Bay is found to be a tectonically formed sedimentary basin. Mesozoic sedimentary rocks are deposited on an eroded surface consisting partly of remnants of presumed Lower Cambrian sandstone and Precambrian basement. The Hanö Bay Basin is divided into a shallow and a deep part by the Nävlinge Flexure in the southeastern extension of the northern scarp of the Nävlingeåsen Horst. The basin is bounded to the SW by the Linderödsåsen and Christiansö Horst blocks. South of the dividing flexure, Upper Triassic-lower Upper Cretaceous deposits are present in the deeper part of the basin, whereas Santonian and Campanian strata cover all of the Hanö Bay Mesozoic basin. Post-Campanian movements have occurred in the Linderödsåsen-Christiansö Horst blocks and in the flexure where, in addition, indications of volcanic or intrusive activity have been observed in the seismic sections.

ISSN:0016-786X    

DOI:10.1080/11035898009450860

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

ISSN:0016-786X    

DOI:10.1080/11035898009450861

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

ISSN:0016-786X    

DOI:10.1080/11035898009450862

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor