Dynamics of the main components of fluxes of sedimentary matter in the White Sea

Doklady Earth Sciences - The results of long-term investigations in a small sea of the Arctic Ocean served as a basis for revealing new regularities characteristic of the sedimentary process in the...     

Depths of the Sea of Okhotsk sedimentary basin in the Cenozoic

The biofacies analysis of benthic foraminifers in sediments of the Sea of Okhotsk paleobasin revealed the presence of typical abyssal species in their Oligocene-Miocene assemblages that are missing in the Pliocene and Pleistocene section. The development of the abyssal fauna in the Sea of Okhotsk was determined by its relatively large depths (>2000 m) and intense water exchange with the Pacific Ocean. The Sakhalin folding phase at the Neogene-Quaternary transition resulted in the uplifting of the Japan-Kurile cordillera and separation of deep basins of the Japan and Okhotsk seas from the ocean, which was responsible for the formation of unfavorable conditions for migration and existence of the Pacific abyssal fauna. The taxonomic similarity and general tendencies in the development of the Neogene benthic foraminifers common for the Japan and Okhotsk seas imply the lack of narrow and shallow thresholds between these basins similar to the present-day Nevel’skoi, La Pérouse, and Sangar straits. Such bottom topography stimulated the intense northward water flow, which determined the similarity between the benthic foraminiferal assemblages of the Japanese and Okhotsk paleobasins.     

Comparative study of vertical suspension fluxes from the water column,rates of sedimentation,and absolute masses of the bottom sediments in the White Sea basin of the Arctic Ocean

A new approach using dispersed organic matter of the water column in sedimentation traps in comparison with the surface layer of the bottom sediments is applied for the study of marine sedimentation. This approach provides the opportunity for an in situ (by fluxes of sedimentary matter in the water column) study of modern sedimentation in the surface layers of the bottom sediments and tracing the changes in the environment and climate at a new technological level. This also allows us to choose the reverse task: to reconstruct the fluxes of the matter and chemical elements in ancient seas by the rates (or absolute masses) of sedimentation.     

南极普里兹湾北部深海沉降颗粒物通量的季节性变化

利用1998～2000年中国南极科学考察期间(第15和16航次)在南极普里兹湾北部海域所获得的沉积物捕获器样品的资料,对南极普里兹湾北部海域颗粒物的有机地球化学特征进行了调查,并重点开展了该海域颗粒物通量及其季节性变化特征的研究。研究结果表明,在1000m深度,颗粒物通量呈现明显的季节性变化,最高通量出现在南极夏季的1月份,最低通量出现在4～7月份;通量的变化范围为13.00～334.59mgd-1m-2。捕获器中颗粒物的主要成分为生源物质(生物硅、有机质和碳酸钙),占总通量的50.62%～92.06%,而生源组分中又以生物硅为主要成分,其值介于9.30～136.33mgd-1m-2之间,占总通量的40.74%～74.21%。有机质和碳酸钙的通量远小于生物硅,分别平均占总通量的9.06%±4.26%和4.42%±2.14%。颗粒物中各组分通量的变化趋势与总通量明显相似,均呈现明显的季节性变化,这主要归因于研究海域海冰的形成与消退。在垂向变化上,1月份1000m深度颗粒物通量高于2000m深度,这表明该海域颗粒物的转化主要发生在上层水体。     

Seasonal variation of chlorophyll and primary productivity in central Arabian Sea: A macrocalibrated upper ocean ecosystem model

Seasonal variation of chlorophyll has been of considerable interest on account of the effect of photosynthesis on ocean-atmosphere carbon exchange. It can be predicted by a dynamical system model of the marine ecosystem coupled with a physical oceanographic model. There is however a major difficulty in the calibration of contemporary ecosystem models on account of sparse data and a large number of model parameters. This paper reports a new approach of macrocalibration in which values of six parameters are determined by examining in detail the seasonal variation of chlorophyll and primary productivity keeping in view the observations of two Indian JGOFS cruises. Both switching and non-switching versions of grazing functions are used in a 7-component FDM model. Detailed simulations are reported for one station (16°N, 65°E). They show the effects of dependence of grazing preference on prey density on the behaviour of the ecosystem. The results of the simulation also provide a partial basis for developing correlations of primary production with chlorophyll and sediment flux.     

On the elemental composition of suspended matter of the Severnaya Dvina River (White Sea region)

New data on the elemental composition of the Severnaya Dvina River, the largest one in the White Sea region, are presented. The elemental composition of the river water in May, the period of the snowmelt flood, is similar to the upper layer of the Earth’s continental crust due to the active erosion of the earth material in the catchment area. In August, the period of the summer low water, the impact of biogenic components increases and elevated concentrations of Cd, Sb, Mn, Zn, Pb, and Cu are observed. At other times, no significant pollution by heavy and rare-earth elements is registered.     

Vendian of the Fore-Yenisei sedimentary basin (southeastern West Siberia)

Fossiliferous Upper Vendian strata are discovered in the Upper Proterozoic to Lower Paleozoic Fore-Yenisei sedimentary basin under a thick Mesozoic-Cenozoic cover in southeastern West Siberia. Two depositional systems are recognized based on sedimentological features: (1) wave- and current-agitated shoreface-forereef-biohermal reef system (Vostok-3 Borehole section) and (2) tidal flat-evaporite basin (Averinskaya-150 Borehole section). The forereef facies yielded fossilized tubular calcareous skeletons of reef-building metazoans Cloudina riemkeae, Cloudina hartmannae and Cloudina carinata, phosphatized Namacalathus-like fossils, and a diversity of tubular phosphatized and agglutinated tubular fossils. The fossil assemblage can be interpreted as the evidence of ecological complexity of the reef system. Paleontological characteristics suggest correlation of the Vendian strata with the lowermost Purella antiqua Assemblage Zone and the boundary interval with the underlying Anabarites trisulcatus Assemblage Zone of the Siberian Platform. Therefore, at least in the late Proterozoic, the Fore-Yenisei sedimentary basin was part of a larger pericratonic depositional system on the western margin of the Siberian Craton.     

Geoelectrical studies of the Chuya basin sedimentary fill (Gorny Altai)

The VES method was used to determine the geoelectric parameters of Cenozoic rocks in the Chuya intermontane basin. It was shown that the polyfacies and polychromous sediments filling the basin are well differentiated by their electrical parameters. A combination of methods used in data acquisition and processing, due to their high resolution capacity at shallow depths, provided information on the structure and physical properties of the Chuya rocks from surface to depths of 250–300 m. Despite a reasonable consistence among these methods to the above depths, the VES method is a more effective tool for detecting shallower layers. Interpretation of the VES data proved the existence of a large outburst channel as new geological evidence for an ice-dammed origin of the Middle Neopleistocene lake. A more detailed layering of the topmost part of the geoelectrical section across the Irbistu–Kokozek interfluve using the VES data revealed a number of fine-grained lenticular structures of the ancient lakes in the Chuya depression, which are hidden beneath a cover of fluvioglacial and lacustrine bouldery pebbles and moraine diamictons.     

Geological structure of Cenozoic sedimentary basin in the Northwestern margin of the Barents Sea shelf

There are two stages in Cenozoic development of the West Barents continental margin: rifting and passive margins. The main thickness of the Pliocene-Eocene complex is typical of the Serverstsnaget Basin, Vestbakken Volcanic Province, and Hornsund fault zone formed under conditions of strike-slip tectonics (“pull-apart” conditions). However, the thickness of the Oligocene-Pliocene sediments reaches its maximum on the eastern slope of the North Atlantic ocean basin. Paleogene and Neogene sediments consist mostly of claystones and siltstones but there are also sandy intervals formed because of gravity flows. The sandy layers can form lithological hydrocarbon traps.     

Dispersed organic matter and its fluxes in oceans and seas from the example of the White Sea: Results of a 12-year study

Annual and long-term quantitative estimations of the vertical fluxes of sedimentary matter in the White Sea are the basis for direct calculations of the gain of chemical components and minerals and diverse pollution of the surface layer of the bottom sediments. The White Sea, one of six Russian Arctic seas, may be considered as a megapolygon for further modern study using the new mechanisms of Arctic sedimentogenesis discovered. This work is directed at elaboration of new technologies of complex study of seas using submarine sedimentation and regular vessel observatories. The first priority task is year-round monitoring along the Northern Sea route.     

Dynamics of suspended matter concentration in Chupa Inlet (Karelian Coast,the White Sea) in summer and autumn

Studies on the water and suspended matter concentration dynamics were performed for the summer and autumn periods in Kruglaya Bay, Chupa Inlet (Karelian Coast, the White Sea). The tidal cycle appeared as the major factor defining the water salinity, temperature, and suspended matter concentration. The water temperature and suspended matter concentration increased during low tide, and the opposite pattern was observed for water salinity; all the processes were true for both surface and bottom water layers. Therefore, we conclude that major bulk of the allochtonous suspended matter is carried into the sea by the ebb stream.     

黄海和东海沉积物有机质活性及营养盐再生潜力初探

2000年秋季和 2001年春季,对黄海和东海 6个站位的水柱和沉积物样品进行了营养盐、沉积有机碳、有机碳同位素和氨基酸分析.结果表明, 表层沉积物的有机碳含量和有机质活性存在较明显的季节性变化,这主要由春秋两季表层水体生物量的差异引起.在泥质堆积区 E2、 E4、 E5站,春季表层沉积物有机碳的含量与活性均较高,而同期底部沉积物向上的营养盐梯度也明显增大, 显示有机碳的含量及活性与营养盐再生有密切关系.     

Nature of sedimentary organic matter in the lower reaches of the Godavari River basin, India

The distribution and nature of sedimentary organic matter (OM) have been examined in sediment cores collected from the lower reaches, including estuary, of the Godavari River in order to understand sedimentation patterns, sources, and diagenesis of OM. The samples were analyzed for organic carbon (Corg), total nitrogen, amino acids and hexosamines. The observed irregular trends in Corg distribution with depth indicate the unstable nature of bed sediment in the lower reaches of the river. Yet, in the lower estuarine region, regular trends in Corg distribution with depth reflect the deposition of sediment. The atomic ratio of Corg and total nitrogen (C/N; 10.5–16.1) also supported this observation. The distribution of amino acids and diagenetic indicators (β-ala+γ-aba mol.%, AA/HA and Glc-NH₂/Gal-NH₂) in individual cores revealed the post-depositional changes in the OM. In the core sediment from the lower reaches, there was no clear cut trend in amino acid content with depth. In the estuarine region, however, amino acid content was very low (50.5 and 186.5 μg g⁻¹) in the upper layers compared to that in the lower layers (558.5 and 1099.3 μg g⁻¹). Reactivity index (range 0.3–3.7) revealed that OM in the upper few centimeters, especially in the lower estuarine region, was more reactive relative to that in the deeper layers.     

东海陆架泥质区沉积有机质的物源分析

色谱和色谱／质谱分析表明，济州鸟西南泥质区正构烷烃、姥鲛烷、植烷、藿烷和甾烷等生物标志物的特征与现代长江口、老黄河口和新黄河口的河流沉积物均区别很大，该泥质区的沉积有机质主要来源于海洋低等生物（如细菌和藻类等）以及陆源高等植物的输入，表现为不同来源和成熟度的生物标志物的混合，同时该泥质区沉积有机质与矿物碎屑沉积物来源不尽相同。长江口泥质区正构烷烃高相对分子质量部分与长江口沉积物相似，正构烷烃和藿烷所反映的有机质成熟度高于现代长江和老黄河口沉积物，甾烷的成熟度与长江相仿而明显高于老黄河口沉积物。长江口泥质区的沉积有机质主要来源于长江输入的陆源高等植物碎片和海洋源的低等生物。东海陆架近岸与远端泥质区沉积有机质的物源很不相同。     

西藏中部伦坡拉盆地古近系沉积有机质特征及意义

西藏中部班公湖-怒江缝合带之上发育一些新生代陆相沉积盆地.与西藏海相沉积盆地相比,这些陆相沉积盆地沉积有机质丰度高、类型好及热演化程度中等,具有很好的油气勘探前景.伦坡拉盆地是其中的代表并且是目前西藏唯一的获得工业油流的盆地.本文对伦坡拉盆地古近系丁青湖组与牛堡组实测剖面有机岩石学及有机地球化学分析研究表明:丁青湖组页岩沉积于半深湖-深湖环境,有机碳含量在2.84%～6.92%之间,有机质类型为Ⅰ型和Ⅱ1型,母质主要来源于藻类及少量高等植物的输入,有机质镜质组反射率(Ro)在0.46%～0.63%之间;牛堡组泥岩和页岩为滨浅湖相沉积,有机碳含量在0.25%～5.99%之间,有机质类型为Ⅰ型和Ⅱ 1型,母质主要来源于藻类及极少量高等植物的输入,镜质组反射率(Кo)在0.49%～0.66%之间;生物标志化合物组成分布特征显示丁青湖和牛堡组沉积于分层的水体且底部水体盐度较高.     

Palynostratigraphy of the Erkovtsy field of brown coal (the Zeya-Bureya sedimentary basin)

The Erkovtsy brown coal field in the northwestern Zeya-Bureya sedimentary basin (129°–130° E, 46°–47° N) is structurally confined to southern flank of the Mesozoic-Cenozoic Belogor’e depression. The verified stratigraphic scheme of the coalfield sedimentary sequence is substantiated by palynological data on core samples from 18 boreholes sampled in the course of detailed prospecting and by paleobotanical analysis of sections in the Yuzhnyi sector of the coalfield (data of 1998 by M.A. Akhmetiev and S.P. Manchester). Sections of the Erkovtsy, Arkhara-Boguchan, and Raichikha brown-coal mines are correlated. Stratigraphic subdivisions distinguished in the studied sedimentary succession are the middle and upper Tsagayan subformations (the latter incorporating the Kivda Beds), Raichikha, Mukhino, Buzuli, and Sazanka formations.     

Seasonal variability of deep ocean particle fluxes and particle composition in the north open sea of Prydz Bay

Time-series Mark VII sediment trap was deployed at 72°58.55′E, 62°28.63°S (north of the Prydz Bay, Antarctica) during the cruise of CHINARE-15 in cooperation with University of Marine of America. Seasonal variability of deep ocean particle fluxes and biogenic components were investigated in order to reveal the fluxes and biogeochemistry of sinking particles in the deep ocean. The results show that the total mass flux of sinking particles at a water depth of 1000 m ranges from 13.00 to 334.59 mg⋅d⁻¹⋅m⁻²). A marked seasonal variability exists in the fluxes of all particle components reflecting the seasonal changes in upper water productivity. Biogenic material was a significant component and biogenic silica represented more than 80% of the biogenic matter, reflecting a diatom dominated system, but a lithogenic fraction is always present. The fact that the POC dominated over particulate inorganic carbon (as CaCO₃) and C_inorg/C_org was always greater than 1, indicate a net removal of CO₂ from surface water by biological activity. __________ Translated from Acta Oceanologica Sinica, 2006, 5: 49–55 [译自:海洋 学报]     

Depositional environment of the Laptev Sea (Arctic Siberia) during the Holocene

The Holocene depositional setting of the Laptev Sea was studied using three marine sediment cores from water depths between 77 and 46 m. Based on sedimentary parameters (TOC content, δ¹³C_org, sedimentation rates) controlled by radiocarbon age models the palaeoenvironment of a strongly coupled river-shelf system was reconstructed since ˜11 ka BP. Caused by a transgressing sea after the last glaciation, all cores reveal progressive decreases in sedimentation rates. Using the sedimentary records of a core from the Khatanga-Anabar river channel in the western Laptev Sea, several phases of change are recognized: (1) an early period lasted until ˜10 ka BP characterized by an increased deposition of plant debris due to shelf erosion and fluvial runoff; (2) a transitional phase with consistently increasing marine conditions until 6 ka BP, which was marked at its beginning near 10 ka BP by the first occurrence of marine bivalves, high TOC content and an increase in δ¹³C_org; (3) a time of extremely slow deposition of sediments, commencing at ˜6 ka BP and interpreted as Holocene sea-level highstand, which caused a southward retreat of the depositional centres within the now submerged river channels on the shelf; (4) a final phase with the establishment of modern conditions after ˜2 ka BP.