RUSSIAN JOURNAL OF EARTH SCIENCES VOL. 8, ES6001, doi:10.2205/2006ES000206, 2006


Conclusion

[62]  The general trend in sedimentation development is the inherited character of carbonaceous deposition in the major part of sedimentary basins at the end of Cretaceous-beginning of the Paleogene. Limestone-marl formation of the Upper Cretaceous developed in the Early Paleocene as well. An exception was the margin of southeastern ending of the Russian Plate and the Cis-Caspian Basin with its sharply contrasting sedimentary settings at the Maastrichtian-Danian boundary. There are good reasons to believe that a rapid transition from Late Cretaceous carbonaceous sedimentation to silicious accumulation in the Early Paleocene for the major part was caused by the arrival of silica and iron paramagnetic compounds, which came by faults in the periods of their tectonic activation.

[63]  From literature and direct observations, the Maastrihtian-Danian boundary in vast areas is marked by low but stable growth of sedimentary rocks susceptibility at the expense of a supply of fine volcanogenic-terrigenous material for the major part paramagnetic (iron hydroxides and clayey minerals containing iron). The stability of this feature in the sections of shelf and upper continental slope is remarkable. This minor rise of magnetization at the boundary between two systems may be interpreted as the initial stage indicator of large-scale changes in sedimentation processes at a large part of the earth surface, including volcanogenic and hydrothermal processes that resulted in the accumulation of metal-bearing sediments and concretions. It is conceivable that a deep relation may have existed between these processes and large geodynamic events, which also included plume formation processes as a part, in the Mesozoic-Cenozoic boundary.

[64]  From correlation of available data, tectonic settings of areas related to plumes and of areas located out of zones of their direct influence appear to be somewhat antipodal. The former are characterized by lacking differentiation of tectonic movements, and scarce troughs only show subsidence of small amplitudes. On the contrary, in remote areas, sedimentation in the Late Cretaceous and Early Paleogene was characterized by lateral heterogeneity, frequent facies alteration, numerous erosions, breaks in sedimentation and common erosional unconformity in the Maastrichtian-Danian boundary. Sections that show gradual transition from the Maastrichtian to the Danian are exclusively rare; in this case hidden interruptions in them are not excluded. The cause of such differences is not evident and thus we restrict ourselves to stating them.

[65]  At present the evidence of the plumes direct influence on sedimentary formations of remote areas is not convincing. Dispersed volcanogenic material admixtures in beddings formed in the epochs of plume process may become perspective indicator. It is not improbable that they may occur in the siliceous deposits of Povolzh'e. Such indicator may be the increased accumulation in sediments of iron-containing paramagnetic minerals of volcanogenic hydrothermal origin of the type of metal-bearing sediments. It awaits for special directed research. Several thin horizons with ash and vitroclastic material in Santonian and Zealandian opoka beds testify to prolonged volcanic activity outside Povolzh'e. In principle, such activity may be related to plumes, but it is not inconceivable that the other feature, island-arc volcanism in Transcaucasia was superimposed.

[66]  An illustrative example shows the lack of direct relation between plume (magmatic) activity and impact events. From detailed biostratigraphic, geochemical and petromagnetic data on the transition layer of clay between the Maastrichtian and the Danian in Gams section (East Alps, Austria) [Grachev et al., 2005], it was established that the early stage of its accumulation went on with active basalt volcanism and it was approximately 500-800 years later, at the end of the layer accumulation, that the impact event indicators like local accumulations of metallic nickel and ferro-nickel alloy spherules and diamond crystals appeared.

[67]  In the Upper Maastrichtian sediments microspherules of metallic iron are noted that are most likely of cosmic meteoric dust, and have no direct relation to impact or/and plume events.

[68]  On the other hand, a marked chronological coincidence of numerous plume activity with global events levels in the Phanerozoic is significant. Such relation is noted at the Vendian-Phanerozoic boundary as well as at the Paleozoic-Mesozoic, the Mesozoic-Cenozoic, and the Eocene-Oligocene boundaries. These facts cannot be explained by a coincidence. They suggest a relation between plume process and large geodynamic reconstructions at major geohistorical boundaries in the last 600 million years.


RJES

Citation: Molostovsky, E. A., V. A. Fomin, and D. M. Pechersky (2006), Sedimentogenesis in Maastrichtian-Danian basins of the Russian plate and adjacent areas in the context of plume geodynamics, Russ. J. Earth Sci., 8, ES6001, doi:10.2205/2006ES000206.

Copyright 2006 by the Russian Journal of Earth Sciences

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