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11.
Siliceous and marine organic-rich deposits are sometimes associated, sometimes separate in space and time; however, both are
generally accepted to be the result of high planktonic productivity. Among the siliceous marine deposits, the phtanite family
facies is distinguished from the radiolarite family facies by several characteristics: They contain organic material and as
a result are blackish (vs red/green for radiolarite facies), their time of deposition corresponds with strong faunal modifications
and they are deposited generally in shallower environments. A palaeogeographic analysis of locations of Tethyan biosiliceous
and marine organic-rich rocks, both resulting from a high planktonic palaeoproductivity, for three Mesozoic high sea-level
intervals, Toarcian, Kimmeridgian and Cenomanian, show: (a) during Jurassic times these Tethyan deposits were dissociated,
the siliceous deposits being closer to open ocean waters than the organic-rich ones. This is a common disposition in modern
upwelling systems and suggests a common process; (b) during Cretaceous times these Tethyan deposits were often associated,
i.e. both occur at the same site, and are probably the result of a different process from that in the Jurassic. 相似文献
12.
13.
The success of ultradeep drilling projects, as e.g. within the German Continental Deep Drilling Programme (Kontinentales Tiefbohrprogramm, KTB) in the Oberpfalz strongly depends on the thermal and geological-tectonic environment of the well. In the present paper we apply the correlation of elevated temperatures and seismic reflectivity of the lower continental crust to the deep seismic network of the Oberpfalz. The results together with the correlation to other geoscientific data indicate increased temperatures in the area of the KTB location. These temperatures are most probably related to influences of the Eger graben and possibly are not yet measured at the surface using heat flow determinations.
Zusammenfassung Der Erfolg ultratiefer Bohrungen, wie etwa in der Oberpfalz im Rahmen des deutschen Kontinentalen Tiefbohrprogramms (KTB), hängt sehr stark vom thermischen und geologisch-tektonischen Umfeld der Bohrung ab. In der vorliegenden Arbeit wird die Korrelation von erhöhten Temperaturen und guter Reflektivität der kontinentalen Unterkruste angewandt auf das seismische Netz der DEKORP 4 und KTB Linien in der Oberpfalz. Aufgrund der Ergebnisse und anderer geowissenschaftlicher Resultate sind höhere Temperaturen als vorher berechnet im Bereich der Tiefbohrung zu erwarten. Diese dürften im Zusammenhang mit dem westlichen Ende des Eger Grabens stehen.
Résumé Le succès de sondages très profonds, comme celui qui est envisagé dans le Haut Palatinat dans le cadre du programme allemand de sondages profonds continentaux (Kontinental Tiefbohrprogramm: KTB) est étroitement lié à l'environnement thermique et tectono-géologique des forages. Dans cette note, la corrélation entre les hautes températures et la réflectivité sismique est appliquée au réseau sismique fourni par les profils DEKORP 4 et KTB dans le Haut Palatinat. Les résultats obtenus, joints à d'autres données géologiques, laissent prévoir dans la région du KTB des températures plus élevées que celles qui étaient envisagées jusqu'ici. Ces températures élevées sont probablement en relation avec l'extrémité ouest du graben d'Eger et n'ont pas encore été repérées en surface par les mesures du flux de chaleur.
170- - / / . , . 18% , : KTst 0=950 (Stefan A), KTst 1=700 (Westfal D), KTst 3=400 (Westfal C), KTst 4a=330 (Westfal ), KTst 4a=322 (Westfal C), KTst 4=320 (Westfal C), KTst 5=300 (Westfal C), KTst 6=270 (Westfal C). . , . , . . , , , - . , 43 - 8,2 3, — 20,5 3. , , - ; , .相似文献
14.
In situ pore-pressure evolution during dynamic CPT measurements in soft sediments of the western Baltic Sea 总被引：1，自引：1，他引：0
Annedore?SeifertEmail author Sylvia?Stegmann Tobias?M?rz Matthias?Lange Thomas?Wever Achim?Kopf 《Geo-Marine Letters》2008,28(4):213-227
We present in situ strength and pore-pressure measurements from 57 dynamic cone penetration tests in sediments of Mecklenburg (n?=?51), Eckernförde (n?=?2) and Gelting (n?=?4) bays, western Baltic Sea, characterised by thick mud layers and partially free microbial gas resulting from the degradation of organic material. In Mecklenburg and Eckernförde bays, sediment sampling by nine gravity cores served sedimentological characterisation, analyses of geotechnical properties, and laboratory shear tests. At selected localities, high-resolution echo-sounder profiles were acquired. Our aim was to deploy a dynamic cone penetrometer (CPT) to infer sediment shear strength and cohesion of the sea bottom as a function of fluid saturation. The results show very variable changes in pore pressure and sediment strength during the CPT deployments. The majority of the CPT measurements (n?=?54) show initially negative pore-pressure values during penetration, and a delayed response towards positive pressures thereafter. This so-called type B pore-pressure signal was recorded in all three bays, and is typically found in soft muds with high water contents and undrained shear strengths of 1.6–6.4 kPa. The type B signal is further affected by displacement of sediment and fluid upon penetration of the lance, skin effects during dynamic profiling, enhanced consolidation and strength of individual horizons, the presence of free gas, and a dilatory response of the sediment. In Mecklenburg Bay, the remaining small number of CPT measurements (n?=?3) show a well-defined peak in both pore pressure and cone resistance during penetration, i.e. an initial marked increase which is followed by exponential pore-pressure decay during dissipation. This so-called type A pore-pressure signal is associated with normally consolidated mud, with indurated clay layers showing significantly higher undrained shear strength (up to 19 kPa). In Eckernförde and Gelting bays pore-pressure response type B is exclusively found, while in Mecklenburg Bay types A and B were detected. Despite the striking similarities in incremental density increase and shear strength behaviour with depth, gas occurrence and subtle variations in the coarse-grained fraction cause distinct pore-pressure curves. Gaseous muds interbedded with silty and sandy layers are most common in the three bays, and the potential effect of free gas (i.e. undersaturated pore space) on in situ strength has to be explored further. 相似文献
15.
Oil refineries and petrochemical industries in Europe 总被引：2，自引：0，他引：2
16.
17.
The possibility of naval mines buried in the seafloor poses difficulties for navies concerned with port and seaway operations. To devise countermeasures, predictions of degrees of impact burial over wide areas of seabed must be made. Under ideal conditions, this is done with a knowledge of local seabed shear strengths, but in practice, such data are rarely available.
We describe an alternative prediction method. Probabilistic predictions of mine impact burial are made across areas of variable seafloor by combining data on sedimentary character directly with experimental impact burial results. The most useful seafloor characteristics are mud content and consolidation. The predictions are relatively accurate (SD 1-22%), and are computable in detail over wide geographic areas. They are of a form immediately useful for naval operations (including calculations of risk) and are easily displayed in geographic information systems (GIS). An example is shown for the northern Gulf of Mexico. 相似文献
We describe an alternative prediction method. Probabilistic predictions of mine impact burial are made across areas of variable seafloor by combining data on sedimentary character directly with experimental impact burial results. The most useful seafloor characteristics are mud content and consolidation. The predictions are relatively accurate (SD 1-22%), and are computable in detail over wide geographic areas. They are of a form immediately useful for naval operations (including calculations of risk) and are easily displayed in geographic information systems (GIS). An example is shown for the northern Gulf of Mexico. 相似文献
18.
During the 2003-2004 winter season, the U.S. Office of Naval Research (ONR, Arlington, VA), sponsored a detailed in situ study of the mine burial process resulting from wave-seafloor-mine interaction at Martha's Vineyard Coastal Observatory (MVCO, Edgartown, MA). In total, 16 mine shapes were deployed. Six were the Forschungsanstalt der Bundeswehr fur Wasserschall und Geophysik (FWG, Kiel, Germany) burial registration mines using optical sensors, four others were equipped with acoustical sensors, and six were simple shapes. Repeated acoustic surveys and detailed sediment sampling were conducted to characterize the site and the burial status of all objects. This paper focuses on data from three recovered optical systems. The records show three roll events at all three registration mines, which are necessary for scour burial. Two systems experienced a fourth roll event. Results from earlier experiments suggest only three (four) stages of progressively increasing burial despite frequent successive burial and exposure cycles (some as short as 1 h). During these burial-exposure cycles changes of buried mine volume reached up to 80%. The only reasonable explanation is a change of sediment height of up to 40 cm relative to the stably lying mines. This requires new concepts. Cyclic burial changes that were observed simultaneously at different positions cannot be explained with existing models. The least difficult explanation is ldquounderwater sand stormsrdquo which are characterized by a high sediment suspension. 相似文献
19.
Guyonic S. Mory M. Wever T.F. Ardhuin F. Garlan T. 《Oceanic Engineering, IEEE Journal of》2007,32(1):119-132
A mine burial field experiment was carried out on two sandy seafloors between January and April 2004 in the Bay of Brest, France. Burial recording mines (BRMs) were used to measure burial and mine orientation at 15-min intervals. Sonar and bottom photographs were also used to characterize sediment morphology and mine burial. These observations are compared with the predictions of mine burial using the following three models: a momentary liquefaction model, a current-induced scour model, and a wave-induced scour model. Analysis combines mine burial data, sediment data, seabed observations, and hydrodynamic measurements. At the first site, ldquoRascas,rdquo the seabed dynamics are dominated by tides and river runoff. Almost no mine burial was measured during the experiment which is in agreement with predictions of mine burial models (current-induced scour and liquefaction). Dynamics at the second site, ldquoBertheaume,rdquo are driven by tides and ocean waves. A long storm (one week) and several swell events were experienced and significant mine burial was observed in conjunction with high significant waveheights. Mine burial models suggest that burial at ldquoBertheaumerdquo was dominated by wave-induced scour rather than current-induced scour or momentary liquefaction. 相似文献
20.