摘要:

Glacial flutes in front of Isfallsglaciären, Swedish Lapland, have been investigated by mapping and till fabric analyses. Till forms near the ice margin reveal a continuum between flutes and shorter forms. Of four considered models of flute genesis, only one fits the observations of this investigation. According to this model, till is squeezed into an initial cavity in the ice formed leeward of an obstruction. The cavity is preserved and migrates in the direction of ice movement. The infilling of the till takes place at right angles to the long axis of the flute. It is stressed that coarse material in flutes can initiate cavities in the same way as the proximal boulder.

ISSN:0016-786X    

DOI:10.1080/11035898009455166

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

ISSN:0016-786X    

DOI:10.1080/11035898009455167

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

A geodynamic balance between movements of the Fennoscandian Shield and the North Atlantic ocean floor (the Faeroe-Iceland Ridge region) is proposed: a vertical movement in one area is balanced by counter-movements in the other area due to the transfer of a low viscosity mass in the asthenosphere. A rapid uplift of the Fennoscandian Shield (and the Barents Sea region) of at least 600 m around the Oligocene-Miocene transition (22.5 Ma) was compensated for by subsidence of the Faeroe-Iceland Ridge area of the order of 1000–1500 m. A significant subsidence of the Fennoscandian Shield at about 0.9–0.8 Ma (of about 600 m) is likely to have been compensated by an uplift of the Faeroe-Iceland Ridge area (explaining a major paleoclimatic change at this time). Major paleoceanographic events occurred at about 38 Ma, 22.5 Ma and 3.2 Ma. A drastic paleoclimatic event — the beginning of the north hemisphere continental glaciations — occurred at about 2.5 Ma. Eustasy is much more complex than originally assumed. In the history of the North Atlantic, eustatic changes play a secondary role.

ISSN:0016-786X    

DOI:10.1080/11035898009455168

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Synclinally folded supracrustal rocks of greenschist-facies metamorphic grade occur in the Grythyttan-Hällefors region. The lower units of the sequence consist of metavolcanic rocks. A quartz-porphyritic K-rhyolite from the upper part of the metavolcanic unit has been dated. Zircons from this rock have a U-Pb age of 1862 Ma, indicating that this volcanic unit in the Grythyttan-Hällefors syncline is younger than the Svecokarelian synkinematic granitoids in general and is as a consequence younger than the rocks of the Leptite formation. Alternatively, the supracrustal sequence in Grythyttan-Hällefors constitutes the uppermost and youngest unit of the Leptite formation.

ISSN:0016-786X    

DOI:10.1080/11035898009455169

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Hornblendite together with anorthositic and pegmatitic dikes forms the bedrock of islet of Hattholmen (20 km south of the town of Umeå, Sweden). These rocks have been analysed chemically. The K-Ar age of the anorthositic and pegmatite dikes is 1676 ± 24 Ma and 1663 ± 24 Ma.

ISSN:0016-786X    

DOI:10.1080/11035898009455170

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Shocked milky quartz from the core of a granite pegmatite occurs at Brunnvasselbodarna, about 10 km from the impact center of the Siljan ring structure. The quartz displays well-developed cleavage fractures dominantly parallel with {1011}, some of which are filled with secondary laumontite. Planar features are common, the most frequently observed are oriented parallel to {1013}, {1011}, {0001}, but {1012}, {1122}, {2131}, {2241} and {5161} are also observed. An estimate of the peak pressure of the shock wave in Brunnvasselbodarna gives ca. 16 GPa. This value is probably too high because the grain size of the pegmatite quartz is large compared to the quartz grains of the rocks for which the method used has been devised.

ISSN:0016-786X    

DOI:10.1080/11035898009455171

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Keilorites(earlier known asTrachyderma) is here considered to be the mucous tube of an annelid worm. Two species are reported from the Silurian of Gotland,K. cf.squamosus(Phillips) from the Hemse Beds (Ludlovian) andK. liljevallisp. nov. from the Högklint and Slite Beds (Wenlockian).

ISSN:0016-786X    

DOI:10.1080/11035898009455172

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

ISSN:0016-786X    

DOI:10.1080/11035898009455173

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

ISSN:0016-786X    

DOI:10.1080/11035898009455175

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

ISSN:0016-786X    

DOI:10.1080/11035898009455176

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor