摘要:

A new wave of speculation on the palinspastic and plate tectonic development of the Baltic shield has underlined the need for palaeocurrent data coupled with interpretation of depositional environments for the sedimentary units in the shield. This paper presents data from the lower part of the Middle Proterozoic (Jotnian) Dala sandstone. Spectacular largescale cross-stratification at Risberg and Mångsbodarne is interpreted as being of aeolian origin. Dip directions of foresets indicate transport towards the northerly quadrant, but, as this reflects a wind direction, it does not tell anything about the regional palaeoslope at the time of deposition. On the other hand, tabular and trough cross-stratified sandstones with abundant intraformational clasts occurring at Fjätfallen are interpreted as being of fluvial origin. Foreset dip directions and trough axes indicate that the palaeocurrent at Fjätfallen was towards the south. This, being a direction of river flow, probably reflects the regional palaeoslope. This palaeoslope direction is consistent with at least one recent model for the palinspastic development of the Baltic shield.

ISSN:0016-786X    

DOI:10.1080/11035898509452614

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Subtill fossiliferous glacimarine sediments from Arnøy, north Troms suggest an ice-free period with high-arctic environments about or before 30000 years B. P. The overlying till shows that the island later has been glaciated by an ice sheet. The till contains reworked marine fossils, probably of interglacial (Eemia?) and Weichselian interstadial age. Similar shell-bearing till is found in Lauksundet on the east side of Arnøy. Radiocarbon dates on reworked shell fragments from Lauksundet indicate a maximum age of the glacial advance of approximately 27000 years B. P.

ISSN:0016-786X    

DOI:10.1080/11035898509452615

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The Rönnklint section is a sea cliff in the Silurian strata of Gotland north of Visby, where the upper part of the Lower Visby Marl and the Upper Visby Marl are excellently exposed. The rich bryozoan fauna from the section comprises twenty six species. There is no faunal shift at the boundary between the Lower and Upper Visby Marl. One new species (Fistulipora pusilla) is described.

ISSN:0016-786X    

DOI:10.1080/11035898509452616

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

ISSN:0016-786X    

DOI:10.1080/11035898509452617

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The cementation of Upper Silurian biohermal rudstones and bedded crinoidal grainstones on Gotland, has been investigated with eathodoluminescence microscopy. The cement stratigraphy includes early marine cement succeeded by clear calcite cements indicating transition from oxidizing to increasingly reducing pore water conditions. The distribution of cement generations shows a systematic variation which indicates preferential penetration of the coarse-grained biohermal rocks by oxidizing meteoric water. This cement stratigraphy together with internal sediment, interpreted as vadose silt, indicates late Silurian emergence and subaerial exposure. The final stages of cement growth and pore occlusion took place after reburial of the locality.

ISSN:0016-786X    

DOI:10.1080/11035898509452618

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

This is a scanned image of the original Editorial Board page(s) for this issue

ISSN:0016-786X    

DOI:10.1080/11035898509452603

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor