摘要:

ABSTRACTThree newThalassiosiraspecies are described.Thalassiosira baldaufiiandT. labimarginatahave previously never been reported whereas specimens ofT. tetraoestrupiihave probably often been assigned toT. oestrupii(Ostenfeld) Hasle (Fryxell and Hasle) in previous studies. The description ofThalassiosira praeoestrupiiDumont Baldauf and Barren is emended.Quantitative analysis of theseThalassiosiraspecies has been completed for upper Miocene and lower Pliocene sediments from three different regions in the northern hemisphere. The material used is from DSDP Hole 552A in the North Atlantic, Site 578 in the NW Pacific and ODP Site 642 in the Norwegian Sea. The abundance patterns (number of valves per gram dry sediment) obtained allow the assessment of the biostratigraphic significance and precision of specific diatom events. Levels of reliability are estimated based on the degree of abundance change at the critical stratigraphic interval, level of abundance, consistency of occurrence and duration of consistency. The chronology of the events is obtained through direct correlation to the established magnetic polarity history.The following four first‐order reliability (R1) diatom datums are proposed: in the North Atlantic the first abundant occurrence (FAO) ofT. praeoestrupii(5.34 Ma), in the Norwegian Sea, first consistent occurrence (FCO) ofT. tetraoestrupii(5.00 Ma), FCO ofT. praeoestrupii(5.00 Ma) and last consistent occurrence (LCO) ofT. baldaufii(4.30 Ma). Two R2 diatom datums are proposed: in the Norwegian Sea, FCO ofT. baldaufii(5.13 Ma), LCO ofT. praeoestrupii(4.87 Ma). Three R3 diatom datums are proposed: in the NW Pacific, FCO ofT. tetraoestrupii(5.02 Ma) and FCO ofT. praeoestrupii(5.54 Ma): in the Norwegian Sea, the first occurrence (FO) ofT. labimarginata(5.83 Ma

ISSN:0954-4879    

DOI:10.1111/j.1365-3121.1993.tb00227.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

ABSTRACTSeismic refraction measurements were made in August 1988 to study the crustal structure off Lofoten, Northern Norway. Twenty‐four 3‐component Ocean Bottom Seismographs (OBS) were used, of which seven were deployed in the area covered by landward‐flowing basalt deposited during the early Eocene break‐up between Norway and Greenland. The main purpose of the OBS survey was to investigate whether this method can be used to map structures below the basalt, which is not easy to penetrate with conventional seismic reflection techniques. The records obtained showed that the OBS data contain considerable information about structures below the flood‐basalt; preopening sediments up to 4.0 km thick is indicated below the 1.0–2.5 km‐thick landward‐flowing basalt. The success of the OBS survey indicates that such measurements can become an important tool in investigations on passive volcanic margins and, potentially, in other areas where highly reflective boundaries make the reflection technique dif

ISSN:0954-4879    

DOI:10.1111/j.1365-3121.1993.tb00228.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

ABSTRACTWe have used a combination of macroseismic and instrumental techniques to re‐evaluate the seismicity of Cyprus and the surrounding region for the period 1890–1900. We identified 56 events which we believe to have a surface‐wave magnitude (Ms) of 4.5 or greater. Early events are located by felt effects alone, and macroseismic information is used to improve the location of many later events. We find the broad pattern of seismicity follows that given by standard listings: an area of weak seismicity to the north‐west of Cyprus in the Gulf of Antalia includes intermediate‐depth events as are found in the Hellenic Arc to the west; a gap of reduced activity separates this activity from that of the main region of Cyprus, where we could find no evidence for sub‐crustal foci; there appears to be no present seismological connection along the presumed plate boundary to the north‐east to the junction of the East Anatolian fault and the extension of the Dead Sea rift system. We find a much greater level of activity in the first part of this century than is given in the standard listings, such as that of the ISC. Up to 1963 we identified 47 events ofMs>4.5, compared with only 10 given in the ISC files. Recent improved station coverage locates more events in the region, but these have not been of large magnitude, and the moment release in recent decades has been appreciably less than earlier in the century. For the events in our list the total moment release is 2.7x 1019 Nm with 75% of this originating in the main Cyprus region. We reaffirm the danger of uncritical use of standard earthquake listings for tectonic interpretation and in particular for hazard evaluation in areas such as this, where neither the historical nor the instrumental seismicity recor

ISSN:0954-4879    

DOI:10.1111/j.1365-3121.1993.tb00229.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

ISSN:0954-4879    

DOI:10.1111/j.1365-3121.1993.tb00230.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Book reviewed in this article:GEOLOGY AND TECTONICS OF THE KARAKORUM MOUNTAINS. Mike SearleTRACKING DINOSAURS. Martin LockleyTHE MECHANICS OF EARTHQUAKES AND FAULTING. Christopher H. ScholzTHE LAST DEGLACIATION: ABSOLUTE AND RADIOCARBON CHRONOLOGIES. E. Bardand and W. S. Broecker (eds)

ISSN:0954-4879    

DOI:10.1111/j.1365-3121.1993.tb00231.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

ISSN:0954-4879    

DOI:10.1111/j.1365-3121.1993.tb00232.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

ISSN:0954-4879    

DOI:10.1111/j.1365-3121.1993.tb00233.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

ISSN:0954-4879    

DOI:10.1111/j.1365-3121.1993.tb00234.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY