Geptner A.R.,Russian Academy of Sciences |
Petrova V.V.,Russian Academy of Sciences |
Pha P.D.,Institute of Marine Geology and Geophysics |
Huyen N.X.,Vietnam Union of Geological science |
Nginh L.T.,Vietnam Union of Geological science
Lithology and Mineral Resources | Year: 2016
Siderites forming beds and lenses in the Neogene lacustrine—swampy sediments of the Rinh Chua Formation (northern Vietnam) are considered in detail. Results of the mineralogical and chemical study of siderites and host terrigenous–clayey siltstones are reported. New analytical data characterize the composition and structure of microbiomorphic (bacterial) bodies in the siderites and terrigenous sediments. Microstructures (porosity) and compositional peculiarities (up to 18% P2O5) of individual horizons of the sediments testify to their lacustrine-swampy genesis. It is established that the siderites in association with the layer silicates were formed during the microbiochemogenic decomposition of terrigenous components, including quartz. © 2016, Pleiades Publishing, Inc.
Tan M.T.,Hanoi University of Mining and Geology |
Dung L.V.,Vietnam Petroleum Institute |
Bach L.D.,Vietnam Union of Geological science |
Bieu N.,Vietnam Union of Geological science |
And 3 more authors.
Journal of Asian Earth Sciences | Year: 2014
The continental shelf of central Vietnam is characterized by complex geological structures in a strike-slip setting and thus by unique morphology compared to other parts of the Vietnam shelf. Studying the Pliocene-Quaternary sediments in this area allows the processes that control the stratigraphic evolution to be highlighted. In this paper, we present new results derived from high resolution seismic data that reveal the geological evolution of the continental shelf of central Vietnam during the Pliocene-Quaternary. Our results demonstrate that the continental shelf of central Vietnam is narrow relatively to other parts of the Vietnam shelf. The evolution of the shelf during the Pliocene-Quaternary was controlled by the pre-Pliocene rifting process. However, fault systems below the present shelf were not strongly active during the Pliocene-Quaternary period, except for several listric faults in the slope. Nonetheless, Quaternary volcanic activities occurred widely both offshore and onshore, especially near the major faults. The Pliocene-Quaternary sedimentary deposits were subdivided into 7 units based on unconformities as result of marine regression corresponding to glacial cycles. Sedimentary environments during this period consist of coastal plain, fluvial, nearshore and shelf environments. Most of the Holocene sediments were trapped nearshore while the outer shelf is characterized by abundant lag gravels as a result of rapid sea level rise between ~20 and 8. ka. © 2013 Elsevier Ltd.