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The seismic expression of a salt-filled channel which cuts across the Mid North Sea High in Quadrant 37 is described, with features interpreted as being produced by salt-edge dissolution forming both eastern and western margins of the channel. The apparent half-graben nature of the channel is shown to be only superficial, and due to complex faulting associated with, but not defining, its western margin. The shallower faulting here is a Mesozoic to early Tertiary growth fault related to local dissolution of Zechstein salt. The dissolution effect appears in turn to have been localized by the presence of a deeper fault that was already downthrown to the east in Zechstein times, when it seems to have limited the eastward progradation of Zechstein shelf carbonates and anhydrites, and had probably ceased to move significantly before the onset of the Late Cimmerian erosional phase. The origin of this arcuate fault is tentatively ascribed to subsidence around a granite batholith. Zechstein salt originally spread some distance to the east and west of the channel; it was dissolved from the edges inwards, mainly before the Late Cretaceous, giving rise to a thicker Mesozoic sequence on parts of the flanks of the channel than in the middle. Besides providing an interesting structural case history, the features described have implications regarding Zechstein sedimentation, reservoir potential, the tectonic history of the North Sea, and the nature of the Mid North Sea High itself. 相似文献
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Trace metals were analyzed in the bulk fine phase of two contrasting salt marsh cores on the North Atlantic east (Baie de l'Aiguillon, LaRochelle, France) and west (Lewes, DE, USA) coasts. The purpose is to gauge how the different clay mineral sources and surface sedimentary diagenetic conditions affect the respective trace element geochemistries. It has been established that there is considerably more clay mineral diagenesis at the zone of redox transition in the Delaware core than in the l'Aiguillon core. The Delaware core shows unweathered glacial sedimentary material directly deposited from the continental shelf whereas the l'Aiguillon core is formed from soil clays deposited after river and estuarine transport. Although there is strong Mn redox depletion in the Delaware salt marsh core, and enrichment in the French one at l'Aiguillon, transition elements seem to follow iron content in both cores. The trace pollutant elements Pb, Sn and Zn show pronounced depth profiles in both North Atlantic cores. The Pb, Sn and Zn appear to be carried by clay sources into the French marshes, while appearing to be largely deposited by atmospheric processes as well into the Delaware marsh.Upon deposition, the Zn appears to become decoupled from lead, which is probably more strongly fixed on clays. The Sn seems to be both air transported, and carried as well on non-clay phases contaminated by industrial organo-tins, including antifouling bottom paints. Copper while uniformly enriched in France, probably from use in regional vineyards, appears enriched only near the top at Delaware, suggesting diagenetic recycling in the more abundant peat in the surface. The Cs and Li appear to be tracers for specific soil-derived clay sources in the French core source materials. These observations suggest that clay is a very important carrier in fixing trace elements for historical records as salt marsh sediments. 相似文献
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本文主要基于浙江中、北部沿海二十一个潮位站资料收集的基础上,分析和计算了水中天与各测站发生高潮的时间间隙,进一步探讨了１９９８年塑望时的高潮间隙。借古论今,从定性到定量论述了浙江中、北部沿海各测站朔望时发生高潮的时间,从而为从事海上作业的人员提供具有实用价值的图表作为参考依据。 相似文献
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