RUSSIAN JOURNAL OF EARTH SCIENCES VOL. 7, ES6003, doi:10.2205/2005ES000183, 2005
[79] 1. The analysis of microfossil distribution in the Late Proterozoic sediments of the SBFS, which were deposited in various environments of the evolving marine basin, shows the actuopaleontological correspondence of the discussed assemblages to certain bathymetrically and facially different zones of the paleobasin.
[80] 2. The reconstruction of sedimentation environments in the Late Precambrian basin of the SBFS confirms as a whole the ecological confinement of the distinguished microfossil groups. Benthic anaerobic bacteria assemblages along with the transported algae remains are characteristic of areas with various depth and stagnant conditions of carbon deposition. The relics of phototrophic cyanophytes and diverse forms of eucaryotic algae are associated with littoral and upper sublittoral sediments. The structures interpreted as bacterial substitute forms occur in almost all environments.
[81] 3. Temporal alterations of microfossil features in the Dal'netaiga and Zhuya horizons are observed almost exclusively in morphotypes referred to the green algae ancestors ( Aducta, Bailikania, Centrum, Dictyotidium, Paracrassosphaera, Retiforma, Sibiriella, and Tchuja). Their initial characters first occurred in the Dal'netaiga Horizon, which basal beds were most likely deposited in the mid-Late Riphean. The ultimate formation of their taxonomic features occurred in the pre-Vendian time, in the uppermost Zhuya Horizon.
[82] 4. Results of the reported investigation support the statement that evolutionary innovations in both Phanerozoic and Precambrian biotas can be revealed only in tracing a temporal succession of biologically related morphotypes and within their inferior taxonomic groups. Taking into account a scantiness of pure morphological method, the improvement of widely used acritarch classification in order to consider the non-formal criteria for distinction of their forms, is desirable.
[83] 5. Considering the studies of Precambrian organic remains as a part of paleontology, we emphasize that its chronological aspect results from notion about nature and evolutionary tendencies of fossil organisms. Thus the ecobiological line of investigation is the decisive for the Precambrian biostratigraphy. The reported records clearly indicate the prospects for use of paleophytological data in conducting the stratigraphic and ecobiological research and geodynamic reconstructions. We suppose that even modest success in this path permits to outline the stratigraphic criteria of previously "mute" microbiotas from ancient basins.
Citation: 2005), Precambrian microfossil-characterized biotopes from the southern margin of the Siberian craton, Russ. J. Earth Sci., 7, ES6003, doi:10.2205/2005ES000183.
Copyright 2005 by the Russian Journal of Earth Sciences (Powered by TeXWeb (Win32, v.2.0).