ISSN:0954-4879    

DOI:10.1111/j.1365-3121.1993.tb00264.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.tb00265.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Topography acts as a filter between regional climate and the consequent response of a glacier or ice sheet. It influences the mass and energy inputs and modifies the ice dynamics. The evolution of the ice sheet surface and, over longer time scales, of the bed topography modulates the climatic forcing.Until we have a better understanding of these topographic linkages, the use of geophysical signals from former ice masses to determine palaeoclimates must be regarded as fundamentally flawed.

ISSN:0954-4879    

DOI:10.1111/j.1365-3121.1993.tb00266.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

We propose that the precipitation of a gelatinous iron‐sulphide membrane is the necessary first step towards life. Membrane vesicles were inflated with alkaline, sulphide‐bearing hydrothermal (<200°C) solution and grew on a submarine sulphide mound in acid iron‐bearing Hadean seawater. Once a critical size had been reached (0.1–1 mm) vesicles would have budded contiguous self‐similar daughters. We assume that the membrane was rendered insulating by the adsorption and/or oxidative precipitation of organic and organosulphur compounds. As a consequence of the naturally induced proton‐motive (chemiosmotic) force, and the activity of the iron monosulphide redox catalysts within the membrane, organic compounds would have accumulated within the vesicle. Osmotically driven growth therefore became more significant with time. The geochemical environment envisaged as responsible for this first step towards life is consistent with that widely accepted for the

ISSN:0954-4879    

DOI:10.1111/j.1365-3121.1993.tb00267.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

The strata of the Ireviken Event can be correlated between Gotland, Sweden and the Viki core on Saaremaa, Estonia, with a high degree of precision. Most of the ten datum planes are found with a precision of better than 0.1 m in the Lower and upper Visby Beds on Gotland and high in the Mustjala Member of the Jaani Formation on Saaremaa. Five of the latest Llandovery–early Wenlock units defined by these datum planes are betweenc.0.12 and 1.77 m thick on Gotland and 0.12 and 0.67 m in Estonia. The duration of each was between a few thousand andc.31 000 years. The stratigraphic resolution achieved in the interval of the Ireviken Event is 10,000 years. Ultimate range ends are lacking within a preceding, slightly longer interval, but the pattern of intermittent presence of some taxa agrees well with an unchanged relative rate of sedimentation. Their coeval presence in different places indicates ecological, regional or more widespread change

ISSN:0954-4879    

DOI:10.1111/j.1365-3121.1993.tb00268.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

We have analysed ring‐width records of two Miocene coniferous trees with an absolute age of 15–20 million years. Such data may reflect solar periodicities from the prehistoric past. Evidence for a main period of ∼ 12.5 years has been found. This is near the present basic solar activity period of ∼ 11 years. Other periodic components appear at 220, 150 and 53 years, respectively, which may also be related to solar var

ISSN:0954-4879    

DOI:10.1111/j.1365-3121.1993.tb00269.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

The SW part of the Baltic Sea between Scania, Rügen, Bornholm and Mön constitutes a complex crustal transition between the Baltic Shield and the accreted Phanerozoic provinces of the West European Platform. An integrated interpretation of marine reflection seismic data sets from the BABEL AC line and two commercial surveys offshore NE Germany and S Sweden have resulted in a complete view of the structural framework in the area. The general seismic picture can best be detected by two characteristic sets of reflection phases. The lower set is dominated by slightly dipping and vertically displaced prominent reflectors corresponding to downfaulted Lower Palaeozoic strata on top of the Precambrian basement. The upper set represents Mesozoic and Cenozoic coherent reflection phases including a thick Upper Cretaceous unit. The Caledonian deformation front is identified in the southern part of the investigated area as the border against which basement rocks have been affected by Caledonian metamorphism and deformation. Major structural elements also include the N–S trending Agricola–Svedala Fault and North Rügen‐Skurup Fault. Several NW–SE trending faults are also identified including the Nordadler–Kamien Fault, Jutland–Mön Fault, Carlsberg Fault, Romeleåsen Fault Zone and the Fyledalen Fault Zone. The sedimentary record from NE German offshore wells and Scanian boreholes is compared with the seismic data. The Cambro‐Silurian strata are composed mainly of quartzitic sandstones, shales and biomicritic limestones. The Silurian is dominated by grey, micaceous shale and micaceous siltstone deposited in a marginal basin. Upper Palaeozoic strata are merely encountered in the southernmost part of the investigated area. These include Zechstein strata. The Mesozoic deposits are dominated by a thick Cretaceous sequence of mainly limestones with inte

ISSN:0954-4879    

DOI:10.1111/j.1365-3121.1993.tb00270.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

The Carpathian‐Pannonian region has been characterized by a two‐stage tectonic evolution since the beginning of the Neogene. During early and mid‐Miocene the lateral eastward escape of the Pannonian Fragment caused thrusting and folding in the Outer Carpathian Mountains, south‐ and westward directed subduction of the Eurasian lithosphere, calc‐alkaline volcanism along the Inner Carpathian bend, and localized fault‐controlled subsidence of basins in the Pannonian region. This style of tectonic deformation ceased by the end of the mid‐Miocene. The neotectonic stage began in the late Miocene. It is characterized by differential regional subsidence with maximum rates in the west and east and minimum rates in the centre of the Pannonian Basin. Further characteristics of the central Pannonian Basin are the anomalous high heat flow values, the thin crust and lithosphere.The neotectonic stress field has been determined byin situstress measurements, the analyses of borehole breakouts and fault‐plane solutions of earthquakes.In situstress measurements by the doorstopper and triaxial strain cell methods indicate high compressional stresses in the western Pannonian Basin with its maximum in WNW‐ESE to NW‐SE direction. In contrast to its western part, the central Pannonian Basin shows tensional stresses near the Earth's surface with maximum tension in the same WNW‐ESE direction. Borehole breakout data indicate a general WNW‐ESE orientation of maximum horizontal stress in the western part of the Pannonian Basin and in the eastern part as well, whereas in the central Pannonian Basin this direction is the preferred azimuth of minimum horizontal stress.It is suggested that the neotectonic deformations and stresses in the Carpathian‐Pannonian region have a sublithospheric origin.Asthenospheric convection with an upwelling mantle flow below the centre of the Pannonian Basin and downwelling flows along the cold lithospheric roots below the eastern Carpathians and the Alps seems to be most plausible. Accordingly, the relative uplift of the centralPannonian Basin, the high heat flow and also the tensional stresses are explained as the surface expression of an upstreaming branch of a localized convection cell

ISSN:0954-4879    

DOI:10.1111/j.1365-3121.1993.tb00271.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Terrestrial heat flow density is a key parameter in understanding the past, present and future development of our planet. Most phenomena studied in deep crustal geophysics are temperature dependent and therefore reliable assesments of deep temperatures are necessary. Most heat flow measurements have been made in drill holes which are shallow (<1 km) in comparison to the thicknesses of the crust and lithosphere. The recent findings in deep drilling projects (e.g. the Kola deep hole in Russia and the KTB hole in Germany) have yielded results which suggest that there is a distinct contrast between heat flow densities measured in the uppermost 1 km and values measured at deeper levels. The factors contributing to the vertical variation in the uppermost few kilometres are discussed with special emphasis on palaeoclimatic ground surface temperature changes and groundwater circulation in the bedrock.

ISSN:0954-4879    

DOI:10.1111/j.1365-3121.1993.tb00272.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

The earthquake (Ms= 5.3) of 20 March 1992 and its aftershocks, which occurred near the volcanic island complex of Milos, South Aegean, Greece, are studied on the basis of filed observations and instrumental data. The mainshock caused some building damage, the maximum intensity of VI+ (MM) being assigned to Triovasalos, Milos. Ground cracks, liquefaction in soil, landslides and rockfalls were observed in Milos. Liquefaction took place at an apparently anomalously long epicentral distance (D= 12 km) and is associated with unusually small earthquake magnitude. Abnormal animal behaviour was reported no longer than twelve hours before the mainshock. Theb‐value (= 1.02) of the G–R relation for the aftershock sequence, the exponentially decreasing number of aftershocks with time, and the difference (= 0.5) in magnitude between the mainshock and its largest aftershock imply that the origin of these earthquakes is tectonic and not associated with the volcanic field of Mi

ISSN:0954-4879    

DOI:10.1111/j.1365-3121.1993.tb00273.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY