The Late Cretaceous–Cenozoic evolution of the eastern North Sea region is investigated by 3D thermo-mechanical modelling. The model quantifies the integrated effects on basin evolution of large-scale lithospheric processes, rheology, strength heterogeneities, tectonics, eustasy, sedimentation and erosion.
The evolution of the area is influenced by a number of factors: (1) thermal subsidence centred in the central North Sea providing accommodation space for thick sediment deposits; (2) 250-m eustatic fall from the Late Cretaceous to present, which causes exhumation of the North Sea Basin margins; (3) varying sediment supply; (4) isostatic adjustments following erosion and sedimentation; (5) Late Cretaceous–early Cenozoic Alpine compressional phases causing tectonic inversion of the Sorgenfrei–Tornquist Zone (STZ) and other weak zones.
The stress field and the lateral variations in lithospheric strength control lithospheric deformation under compression. The lithosphere is relatively weak in areas where Moho is deep and the upper mantle warm and weak. In these areas the lithosphere is thickened during compression producing surface uplift and erosion (e.g., at the Ringkøbing–Fyn High and in the southern part of Sweden). Observed late Cretaceous–early Cenozoic shallow water depths at the Ringkøbing–Fyn High as well as Cenozoic surface uplift in southern Sweden (the South Swedish Dome (SSD)) are explained by this mechanism.
The STZ is a prominent crustal structural weakness zone. Under compression, this zone is inverted and its surface uplifted and eroded. Contemporaneously, marginal depositional troughs develop. Post-compressional relaxation causes a regional uplift of this zone.
The model predicts sediment distributions and paleo-water depths in accordance with observations. Sediment truncation and exhumation at the North Sea Basin margins are explained by fall in global sea level, isostatic adjustments to exhumation, and uplift of the inverted STZ. This underlines the importance of the mechanisms dealt with in this paper for the evolution of intra-cratonic sedimentary basins. 相似文献
The updated study shows that the taphrogenesis of basement of the Fushun Basin is not a kind of instantaneous process. It intensified gradually and went to extreme in the sedimentary stage of the Guchengzi formation, and then, it weakened rapidly and stopped soon afterwards; the depression did not take place after the taphrogenesis. On the contrary, it almost happened simultaneously with the taphrogenesis. The depression went at a high speed from the beginning of the sedimentary period of the Xilutian formation, and then weakened gradually in the sedimentary period of the Gengjiajie formation. The evolution course of the synsedimentary structure of the Fushun Basin can be summarized as the following six stages: slow taphrogenesis and high speed depression to accelerated taphrogenesis and high speed depression to high speed taphrogenesis and high speed depression to retarded taphrogenesis and high speed depression to gradual halt of taphrogenesis and reduced depression to slow depression and gradual halt of depression. The tectonic evolution resulted in the formation of the "lower taphrogenesis and upper depression" structure. The formation of the binary structure might be due to the suspension of taphrogenesis and the change of the regional structure stress field, but the depression kept going. The result of calculation combining the analysis of the synsedimentary structural frame, the back-stripping method of the subsidence history of the basin basement and the simulation of thermo-settlement history indicates that the great sedimentary space required by the "upper depression part" consists of two parts, namely, 40% from compaction of sediments and 60% from slow depression of the basin basement during a long period of time. Gradual halt of the depression in the Fushun Basin may be attributed to the reversal of the lithosphere hot-recession and gravity isostasy adjustment which may be the result of new hot-events in the depths and accompanied invasion of extremely thick diabase sill, thus revealing a new forming mechanism of "fault subsidence at the base and depression on the top" structure. 相似文献
The lacustrine facies from two sections (Candasnos and Fraga) ofthe Oligocene-Miocene Torrente de Cinca lithostratigraphic Unit in thecentral part of the Ebro Basin (Spain) have been analysed to determine theinfluence of orbital parameters in lacustrine sedimentation. The unit ispredominantly composed of limestones and marls, and represents a shallowlacustrine freshwater system. The sedimentological features of the faciesstudied demonstrate that the lower part of the Candasnos section representsoffshore lacustrine subenvironments whereas the upper part, and the whole ofthe Fraga section, characterise marginal lacustrine areas. Series of stratalthickness variations of limestone, marl, and limestone/marl couplets fromboth sections have been analysed using spectral analysis. This shows thatinformation corresponding to periodic cycles only appears in the offshorefacies, that is to say, in the lower part of Candasnos section, and disappearsin the marginal facies where non-periodic cycles exist. Furthermore, thespectral analysis of the offshore facies highlights the existence of a peak inthe power spectrum with a period of around 7 (6.8 to 7.8) that can berecognised in the field as shallowing-upward lacustrine sequences.Magnetostratigraphic data from the Candasnos section allow us to establish atime span of 2,808 years for the limestone/marl couplet from the lower partof this section, and between 19,000 and 22,000 years for the periodic cycleidentified, thus representing the climatic precession cycle. Shallowingsequences from marginal areas do not correspond with any periodiccycle. 相似文献
. Three transgressive–regressive 2nd-order cycles were identified in the Upper Aptian–Albian fluvial and marine deposits of the Lusitanian Basin. Its widespread nature, probably including eustatic origin, allows correlation between the southern package, with precise stratigraphic positioning, and the northern series with a poorly constrained age. The main unconformities can be related to the onset of an oceanic crust, in the western margin of Galicia during the Late Aptian, in the bay of Biscay during the Early Albian, and, to the northwest of the Galicia triple point, during the Middle to Late Albian transition, and, at the Albian–Cenomanian boundary, to a probable compressive event with Africa due to the rotation of Iberia. To cite this article: J. Dinis et al., C. R. Geoscience 334 (2002) 757–764.相似文献