Vietnam Institute of Geosciences and Mineral Resources VIGMR

Hanoi, Vietnam

Vietnam Institute of Geosciences and Mineral Resources VIGMR

Hanoi, Vietnam
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Takahashi O.,Tokyo Gakugei University | Maekawa T.,Kumamoto University | Komatsu T.,Kumamoto University | Nguyen Duc P.,Vietnam Institute of Geosciences and Mineral Resources VIGMR | And 2 more authors.
Revue de Micropaleontologie | Year: 2017

This article presents a rather well-preserved radiolarian fauna recovered from black siliceous mudstone occurring in the Ky Cung River section 02 (KC02) of the Bac Thuy Formation, Lang Son Province, northeastern Vietnam. The KC02 section has been regionally correlated on the basis of the first appearance of the diagnostic Spathian ammonoid Tirolites. The ammonoid assemblage associated with radiolarians indicates that the black mudstone sample is early Spathian in age (Late Olenekian). The radiolarian fauna is characterized by a very low diversity of entactinarians of the family Hindeosphaeridae and of to another unidentified family, and by the absence of nassellarians. Here we describe two new species of entactinarians, Parasepsagon primitivus nov. sp. and Eptingium? reticulatum nov. sp. The composition of the fauna suggests that the beginning of diversification of Mesozoic-type radiolarians occurred at the beginning of the Spathian on the eastern margin of the tropical Tethys. © 2017 Elsevier Masson SAS.

Komatsu T.,Kumamoto University | Takashima R.,Tohoku University | Shigeta Y.,National Museum of Nature and Science | Maekawa T.,Kumamoto University | And 5 more authors.
Palaeogeography, Palaeoclimatology, Palaeoecology | Year: 2016

The Smithian-Spathian boundary is indicated by the first occurrence of the ammonoid Tirolites cf. cassianus in the Olenekian Bac Thuy Formation, northeastern Vietnam. The boundary is intercalated within organic-rich dark gray mudstone that accumulated under anoxic to dysoxic conditions in the An Chau and Nanpanjiang Basins on the South China Block. In Lang Son area, three conodont zones, Novispathodus ex gr. waageni, Novispathodus ex gr. pingdingshanensis, and Icriospathodus collinsoni, are recognized in the formation. The Smithian-Spathian boundary is intercalated within N. ex gr. pingdingshanensis conodont Zone. The positive excursion inδ13C with values increasing from around -2.3‰ to +5.7‰ was recorded in the uppermost Smithian Xenoceltites variocostatus ammonoid beds and N. ex gr. pingdingshanensis conodont Zone. The δ13C values decrease across the Smithian-Spathian boundary. These δ13C isotopic patterns are correlated with well-known positive excursions around the Smithian-Spathian boundary globally. © 2016 Elsevier B.V.

Komatsu T.,Kumamoto University | Naruse H.,Kyoto University | Shigeta Y.,National Museum of Nature and Science | Takashima R.,Tohoku University | And 7 more authors.
Sedimentary Geology | Year: 2014

In the An Chau basin in northeastern Vietnam, the Olenekian (Lower Triassic) stage comprises mixed carbonate and siliciclastic shallow marine to marginal basin deposits that extend into the southern Nanpanjiang basin in South China. The upper Lang Son Formation, which is dominated by siliciclastic facies, is composed of storm- and wave-influenced shallow marine and slope deposits. The overlying and interfingering Bac Thuy Formation consists of tidal flat, wave-influenced carbonate platform, slope, and marginal basin plain deposits. The tidal flat deposits are composed mainly of lenticular, wavy-bedded, or thin flat-bedded carbonates containing desiccation cracks and ripples that are indicative of bidirectional paleocurrents. The platform carbonates are characterized by wave ripples, ooids, and abundant marine mollusks and microfossils; the molluscan fossil assemblage primarily contains Smithian ammonoids such as Owenites koeneni. The slope deposits are characterized by limestone breccia and slump beds. The marginal basin plain deposits consist of classical turbidite beds, minor limestone breccia, and hemipelagic mudstone and marl containing the Spathian ammonoids Tirolites and Columbites. The turbidite sets may represent frontal splay environments in the marginal basin plain. These Olenekian carbonate and siliciclastic facies are typical of a transgressive succession.The Smithian-Spathian boundary and the anoxic to dysoxic facies of the latest Smithian are characterized by organic-rich dark gray limestone and mudstone deposits intercalated in the succession of slope to marginal basin plain facies, which are composed mainly of gravity flow and hemipelagic deposits. The organic-rich deposits show no evidence of bioturbation and are characterized by low-diversity fauna. Clastics in the marginal basin plain deposits were apparently supplied from the west; hence, the paleocurrent direction of the siliciclastic gravity flows was approximately eastward. © 2013.

Tanaka G.,Gunma Museum of Natural History | Komatsu T.,Kumamoto University | Saito Y.,Geological Survey of Japan | Nguyen D.P.,Vietnam Institute of Geosciences and Mineral Resources VIGMR | Vu Q.L.,Ai Mo
Marine Micropaleontology | Year: 2011

Eighty-five species belonging to 46 genera of Ostracoda were recovered from 169 samples in three sediment cores (VN, NB, and GA) from the Red River delta plain, northeastern Vietnam. From a Q-mode cluster analysis, we recognized three biofacies (Biofacies A, B, and C). Biofacies B is subdivided into Biofacies BI and BII. The environment of Biofacies A is interpreted as open marine, those of Biofacies BI and BII as marine to brackish water and brackish water, respectively, and that of Biofacies C as oligohaline to mesohaline brackish water. The Holocene sediments consist of estuarine sediments deposited under relatively high sea levels following transgression, deposited during 11-8.5cal kyr BP, overlain by deltaic sediments deposited under relatively low sea levels following regression, and the ostracod assemblages reflect these changes. The estuarine sediments of the early Holocene transgression are characterized by ostracod Biofacies BI. An erosional surface marks an abrupt change to the shelf environment, accompanied by sediment starvation. The interval around this surface, identified as the maximum flooding surface, is characterized by ostracod Biofacies A. During the subsequent delta progradation, the sedimentary environment changed from a prodelta to delta front, and then to a delta plain, and the corresponding ostracod assemblages changed from Biofacies A to BI, BII, and then C in ascending order. Taken together, our results show that the temporal changes in ostracod assemblages since 10. cal kyr BP are closely related to the evolution of the Red River delta system and can serve as good indicators of paleoenvironmental changes. © 2011 Elsevier B.V.

Komatsu T.,Kumamoto University | Shigeta Y.,National Museum of Nature and Science | Huyen D.T.,Vietnam Institute of Geosciences and Mineral Resources VIGMR | Tien D.C.,Vietnam Institute of Geosciences and Mineral Resources VIGMR | And 2 more authors.
Paleontological Research | Year: 2013

Well preserved molluscan fossils of Olenekian age (Early Triassic) were obtained from the upper part of the Bac Thuy Formation in Lang Son City, northern Vietnam. We report here an ammonoid, Xenoceltites variocostatus Brayard and Bucher, and describe two bivalve species, Crittendenia australasiatica (Krumbeck) and Crittendenia langsonensis sp. nov. Xenoceltites variocostatus is a characteristic species of the uppermost Smithian Anasibirites ammonoid zone and the earliest Spathian Tirolites ammonoid zone. Crittendenia australasiatica and C. langsonensis may thus be significant diagnostic species suggesting a middle Olenekian age. In addition, these occurrences demonstrate a probable faunal exchange between the eastern Tethys and eastern Panthalassa during the Olenekian, because many species of Crittendenia have been reported from Asia and from Panthalassic basins in the United States. © by the Palaeontological Society of Japan.

Ho H.H.,Catholic University of Leuven | Ho H.H.,Vietnam Institute of Geosciences and Mineral Resources VIGMR | Swennen R.,Catholic University of Leuven | Cappuyns V.,Catholic University of Leuven | And 5 more authors.
Estuaries and Coasts | Year: 2013

In the present study, the geochemistry of 49 surficial-bed and 101 core sediment samples is investigated to clarify the origin of trace metals in the Cua Luc Estuary and Ha Long Bay, which is a famous World Natural Heritage Site in Vietnam. Moreover, the potential mobility of trace metals is also assessed and their relationship with reference elements (Al, Fe, and Ca) and organic matter is established in order to make recommendations for sediment management and monitor future pollution. Generally, trace metals display higher concentrations in Ha Long Bay compared to the Cua Luc Estuary. However, this is controlled by the distribution of the fine (clay + silt) fraction, and hence the concentrations of Al, Fe, Ca, and organic matter (OM). The comparison of concentrations of trace metals (normalized towards Al) between the surficial sediments and the subsurface core sediments based on 137Cs datings indicates that almost all surficial-sediment data fall inside or deviate slightly from the 95 % prediction interval of a background regression line. In addition, as determined by a Community Bureau of Reference three-step extraction, trace metals mainly dominate in the residual fraction (assumed to relate to crystal lattice of primary and secondary minerals), and this fraction does not change much in recent sediment layers. Therefore, trace metals are supposed to be derived from natural bio/geochemical processes and are characterized by a low potential mobility. Consequently, the established linear regression relationships of trace metal vs. Al or multiple regression relationships of trace metal vs. multi-elements (Al, Fe, Ca, and OM) are useful for the prediction of background levels of trace metals in sediments in future pollution monitoring and assessment programs. © 2012 Coastal and Estuarine Research Federation.

Ho H.H.,Catholic University of Leuven | Ho H.H.,Vietnam Institute of Geosciences and Mineral Resources VIGMR | Swennen R.,Catholic University of Leuven | Cappuyns V.,Catholic University of Leuven | And 4 more authors.
Science of the Total Environment | Year: 2012

Since contaminated river-bed sediments in the Cam River-mouth (Vietnam) are regularly dredged and disposed on land, an understanding of the influence of time, pH and oxidation on the leaching behavior of heavy metals (Cd, Cu, Mn, Pb and Zn) and arsenic is necessary for the management of these dredged materials. A 96h pHstat-leaching test to examine the leaching behavior of elements at pre-set pH values (2, 4, 6, 8 (natural), 9 and 11) and a BCR 3-step extraction to clarify the element fractionation, were performed on a freshly-collected wet suboxic sediment and a dry oxidized sediment. All heavy metals and arsenic display a V-shaped pH-dependent leaching pattern with important releases at pHs 2 and 11. At the investigated pH values, the release of As, Mn, Pb and Zn from the oxidized sediment is slower and lower if compared with the suboxic sediment while the opposite trend is found for Cd and Cu at pHs 2-8. The transfer from the acid-soluble (exchangeable and carbonate-bound) fraction to the reducible (Fe and Mn hydr/oxide-bound) fraction is consistent with the lower leachability of As, Mn and Zn at pHs 2-8 and Pb at pHs 4-8 after oxidation, while the transfer from the oxidizable (organic matter and sulfide-bound) fraction to the reducible fraction relates to the higher leachability of Cd and Cu at pHs 2-8. The lower leachability of all elements at alkaline pHs 9-11 is due to lower leached concentration of organic matter from the oxidized sediment. Sulfides only play a minor role in controlling the leachability of heavy metals and arsenic. © 2012 Elsevier B.V.

Ho H.H.,Catholic University of Leuven | Ho H.H.,Vietnam Institute of Geosciences and Mineral Resources VIGMR | Swennen R.,Catholic University of Leuven | Cappuyns V.,Catholic University of Leuven | And 4 more authors.
Aquatic Geochemistry | Year: 2013

The speciation and mobility of some selected trace metals (As, Cu, Mn, Pb and Zn) in sediments with depth was investigated in the Cam River-mouth (Vietnam) by collecting sediment cores and analysing porewater and sediment composition, complemented with single (ammonium-EDTA) and sequential (BCR 3-step) extractions and mineralogical analysis (XRD). All trace metals show overall decreasing trends with depth in porewater as a result of anthropogenic input in upper sediment layers. High porewater concentrations of As, Mn and Pb in oxic and suboxic sediment layers may result in groundwater pollution. Sediment-bound Pb and Mn dominate in the reducible and the acid-soluble fraction, respectively, while Cu and Zn distribute rather evenly between four extracted fractions. The porewater metal speciation, as predicted by a geochemical model Visual MINTEQ version 3. 0, indicates that the toxicity of Cu, Mn, Pb and Zn (presented by the proportions of free metal ions) decreases with depth, while the toxicity of As increases when As(III) becomes more abundant. The dissolved concentrations of trace metals are not only controlled by the precipitation/dissolution of discrete hydroxide/oxide, carbonate and phosphate minerals, but also by sorption processes on major sorbents (i. e. As on goethite, and Mn and Zn on calcite and dolomite). Sulphide minerals do not show any control even in the anoxic zone most likely because of the low concentration of sulphur. © 2012 Springer Science+Business Media Dordrecht.

Ho H.H.,Geology | Ho H.H.,Vietnam Institute of Geosciences and Mineral Resources VIGMR | Swennen R.,Geology | Cappuyns V.,Geology | And 3 more authors.
Journal of Asian Earth Sciences | Year: 2012

While assessing many different aspects of contamination by heavy metals and arsenic in sediments, the natural variability in element contents which depends on the grain-size and mineralogical composition of sediments, needs to be taken into account. In previous studies, the normalization of element contents to a reference element such as Al was commonly applied to compensate for granulometric and mineralogical effects. In the present study, through the investigation on the contamination of heavy metals and arsenic in sediments near Haiphong Harbor, the necessity of the normalization towards Al is assessed. The results indicate that before Al-normalization, the occurrences on the source and historical trend of contamination by heavy metals and arsenic can be masked by the distribution of clay (Φ<2 μm) or fine (Φ<63 μm) fractions as well as Al, Fe and organic matter. In contrast, after Al-normalization, spatial distribution of elements illustrates that Cr, Ni, Pb and Mn are enriched by the anthropogenic activities in the Haiphong industrial and harbor zone while As, Cd and Cu come from upstream sources, and Co and Zn indicate only locally-elevated contaminations. The vertical profile of elements in core sediments illustrates that the anthropogenic input of heavy metals and arsenic increased in recent years. Moreover, the assessment of the degree of contamination based on the Enrichment Factor (EF) and obtained local background values indicates a minor enrichment of all heavy metals and arsenic. This is not in line with the assessment based on the sediment quality guidelines or reference values from upper-continental or average-continental crust which states the "serious" contamination of Cd, Pb, Cu, Zn and especially As. Therefore, the normalization to Al is necessary in interpreting the source, historical trend and degree of contamination by heavy metals and arsenic in sediments of the study area. © 2012 Elsevier Ltd.

Ho H.H.,Vietnam Institute of Geosciences and Mineral Resources VIGMR | Swennen R.,Catholic University of Leuven | Van Damme A.,Catholic University of Leuven
Geologica Belgica | Year: 2010

The distribution, controlling geochemical factors and contamination status of heavy metals in estuarine sediments near Cua Ong Habor, Ha Long Bay (Vietnam) were investigated. 36 surface sediment samples were collected and analyzed for major elements (Al, Ca, Fe, K, Mg, S), heavy metals (As, Cd, Co, Cr, Cu, Mn, Ni, Pb and Zn), organic matter, loss on ignition (LOI), grain size composition and pH. Spatial distribution patterns of heavy metals as well as their controlling factors were elucidated based on geochemical mapping and statistical methods such as the Pearson Product-Moment linear correlation and Factor Analysis. The results illustrated that the distribution patterns of As, Cd, Cr, Cu, Ni, Pb and Zn are mainly controlled by organic matter and clay minerals and determined by the distribution of the finegrained fraction (φ < 63 μm) in the sediments. In contrast, Fe and Mn compounds seem to exert some control on the distribution of Co. Carbonates partly control the distribution of Mn, but are not important with respect to the other studied heavy metals. The contamination status by heavy metals was assessed based on comparison with Canadian, Wisconsin-United States and Flemish numerical Sediment Quality Guidelines, and calculation of Geo-accumulation Index (Igeo) and Enrichment Factor (EF). The results indicated that natural processes such as weathering and erosion of bedrock are the main supply sources of heavy metals in sediments near Cua Ong Harbor. Among the studied heavy metals, only As is of concern whereas Cd, Co, Cr, Cu, Mn, Ni, Pb and Zn seem to reflect their background concentrations in sediments of Ha Long Bay.

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