ISSN:0954-4879    

DOI:10.1111/j.1365-3121.1996.tb00562.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

ISSN:0954-4879    

DOI:10.1111/j.1365-3121.1996.tb00563.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTMetamorphosed tectonic blocks (or ‘knockers’) are widespread but volumetrically minor constituents of many circum‐Pacific mélange belts, Due to the common lack of an exposedin situprovenance and to the seemingly chaotic field disposition of most block‐bearing mélanges, their origin and uplift history are problematic and controversial. On the Indonesian island of Sulawesi a block‐bearing mélange is overlain by an ophiolite nappe, the base of which is characterized by a metamorphic sole sequence. Petrological, geochemical and geochronological data indicate a direct genetic relationship between high‐grade tectonic blocks in the mélange and amphibolites in the metamorphic sole. Amphibolite precursors to lower temperature blueschist assemblages are virtually ubiquitous in the tectonic blocks and subdivisions based on the nature of the overprinting relationships can be systematically correlated with block distribution patterns orientated subparallel to the strike of the mélange belt. It is suggested here that the high‐grade tectonic blocks originated in a thin, thermally zoned metamorphic sheet welded to the oceanic hangingwall plate at the inception of subduction. Break‐up of this sequence at depth, by tectonic erosion, led to dispersal of fragments into a newly developed serpentinite mélange wedge. Blocks experienced abrupt changes in P‐T‐X conditions due to a combination of hydration in the new fluid‐rich environment, gradual cooling of the hangingwall over time and continuing underflow dragging sheared blocks deeper into the subduction zone, prior to upflow. Blocks plucked from the hangingwall at different depths and at different times evidently experienced uplift in different flow channels, resulting in block concentrations, with P‐T‐t paths characteristic of their source and flow trajectory, at systematically greater distances from the subduction zone hangingwall. The elucidation of the origin and significance of tectonic blocks in Sulawesi has important implications not only for the tectonometamorphic evolution of similar inclusions in other mélange belts, but also for models of the inceptio

ISSN:0954-4879    

DOI:10.1111/j.1365-3121.1996.tb00564.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTFor groundwaters of tectonic active regions the problem of determining the residence time above the range of the tritium method arises. The usually applied isotope techniques are often not appropriate because of (i) the high amount of water‐rock interaction, (ii) the underground production of nuclides in crystalline fissured rocks under geothermal conditions, (iii) the occurrence of highly saline waters at boiling temperature affected by waterrock interaction processes, as also the high fluxes of CO2. However, the36Cl evolution will be affected by these processes, too. Nevertheless it gives an independent tool to investigate the groundwater evolution. Therefore the application of the36Cl method looks very promising. Within this publication the interpretation of36Cl measurements of three study areas along the North Anatolian Fault zone (from East to West) of Kuzuluk/Adapazari, Bursa and of Canakkale (Tuzla/Kestanbol) are discussed. By considering for each area the sources of36Cl and the water‐rock interaction with respect to the chloride cycle, information on the ongoing processes of groundwater circulation and evolution have been derived. In addition, ranges of residence times of these waters were gained which are compatible with the results of geological, hydrogeological and hydrochemical investigations (Baldereret al., 1991; Greber, 1992, 1994; lmbach, 1992, 1994; Imbach and Balderer, 1990; Mutzenberg, 1989) as well as with already developed conceptual groundwater flow mod

ISSN:0954-4879    

DOI:10.1111/j.1365-3121.1996.tb00565.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTSequence stratigraphic concepts can provide a powerful tool for understanding the tectono‐sedimentary evolution of areas extending across different tectonic domains. An example is provided by the upper Serravallian strata of the northern Apennines, where a sedimentological and biostratigraphic study allows a sequence boundary to be traced across the foredeep and piggy‐back basin successions. Turbidite sedimentation of predominantly alpine and subordinate apenninic provenance occurred in the apenninic foreland basin throughout the middle Miocene. Deep‐water sedimentation in the foredeep was laterally associated with deposition in shelf to slope environments in the piggy‐back basins.In the piggy‐back basin succession, the upper Serravallian sequence boundary is a laterally extensive unconformity within homogeneous marly deposits. This unconfonnity is laterally correlative with the base of lenticular turbidite bodies. A stratigraphic lacuna affecting Zone N14 characterizes the marginal areas, where glaucony‐rich deposits assigned to Zone N15 unconformably overlie marls displaying association of Zone N13. In the depocentres, where no significant stratigraphic gap has been detected, the sequence boundary is narrowly constrained to lowermost Zone N14.The upper Serravallian unconformity of the piggy‐back basins succession is correlative with time‐equivalent features in two distinct parts (inner basin and outer basin) of the foredeep. In the inner basin the sequence boundary separates basin margin turbidites from overlying slope hemipelagites. In a more external position (outer basin) the sequence boundary is the base of a characteristic mega turbidite of apenninic provenance (Turrito layer). In other sectors of the outer basin, where turbidite sedimentation was entirely of alpine provenance, the sequence boundary has no clear physical expression.The observed facies distribution in the study area suggests that an important thrusting event affected the northern Apennines in the late Serravallian, resulting in submarine channel incision and nondeposition in the piggy‐back basins. Compressional activity in the foredeep was responsible for the closure of the inner basin and subsequent shifting of turbidite sedimentation in the outer basin. Slope instability led to widespread remobilization of previously deposited turbidites, triggering turbidite events of huge volume. The different characteristics of the sequence boundary in the various parts of the foredeep constitute an example of differential response of a multisourced supply system to tec

ISSN:0954-4879    

DOI:10.1111/j.1365-3121.1996.tb00566.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTExpanded sedimentary records from the Tethys reveal unique faunal and isotopic changes across the Palaeocene‐Eocene (P‐E) transition. Unlike in the open oceans, the Tethys exhibits a gradual decrease of 1.5% in δ13C values prior to the rapid δ13C excursion. Associated with the 613C excursion is a decrease in calcite burial, increase in detrital content and appearance of a unique opportunistic planktic foraminifera1 assemblage (e.g. compressed acarininids). The existence of a prelude decrease in δ13C values in the Tethys suggests that the P‐E δ13C excursion may have occurred in two steps and over a few hundred thousand years, rather than as one step over a few thousand years as previously suggested. This slower excursion rate is readily explained by changing organic carbon weathering or burial rates and avoids the need of invokingad hoc

ISSN:0954-4879    

DOI:10.1111/j.1365-3121.1996.tb00567.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTThe Eotvos acceleration, too low to be the principal driving force in Wegener's theory of continental drift, where the decoupling surface was placed between crust and mantle, must be re‐evaluated in the context of Plate Tectonics, where the same surface is localized at the lithosphere‐asthenosphere boundary. In this note, taking into account the departure from spherical symmetry of the Earths internal gravitational potential, a value for the Eotvos acceleration is obtained that is one order of magnitude larger than pre‐Plate Tectonics estimates and almost two times greater than more recent results. This force was higher in the geological past because the Earths angular velocity and flattening were greater than today, and thus may be considered in the large‐scale reconstruction of continental displa

ISSN:0954-4879    

DOI:10.1111/j.1365-3121.1996.tb00568.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTThree field examples are presented which show changes in fault patterns at different scales. Normal faults in Jurassic limestones in Somerset consist of zones of sub‐parallel segments at the exposure‐scale, but contain complex zones of brecciation at the decimetre‐scale. Normal faults in chalk at Flamborough Head consist of a complex network of small faults which accommodate strain between a set of large faults. The different‐sized faults at Flamborough Head have different geometries and histories, with the larger faults showing a phase of reverse reactivation. The faulting in the Sydney Basin, Australia, can be explained in terms of the evolution and reactivation of transfer zones between overstepping faults. These transfer zones can cause the deformation to appear to be more complex as the analysis becomes more detailed.Much recent work on the scaling relationslups of faults assumes that self‐similar fault patterns occur over a wide range of scales. The data presented in this paper, however, suggest that there are problems in using the deformation pattern at one scale to infer deformation at other scales. Ideally, any analysis should involve the study of a wide range of scales to overcome these

ISSN:0954-4879    

DOI:10.1111/j.1365-3121.1996.tb00569.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTThe 1968 Belice earthquake sequence, characterized by six main shocks with 5

ISSN:0954-4879    

DOI:10.1111/j.1365-3121.1996.tb00570.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTSeveral seismogeological effects of earthquakes on the environment have been collected by means of the ING macroseismic procedure. The fast and easy collection of information about ground and hydrological effects constitutes a complementary instrument in assessing the effects on human structures and the environment, and, ultimately, establishing intensity values. In this paper the distribution of seismogeological effects within intensity values has been verified, using data from three moderate Italian earthquakes; the density of the same effects are then discussed in comparison with isoseismal maps.

ISSN:0954-4879    

DOI:10.1111/j.1365-3121.1996.tb00571.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY