Bacterial response to contrasting sediment geochemistry in the Central Indian Basin

In order to investigate whether geochemical, physiographic and lithological differences in two end‐member sedimentary settings could evoke varied microbe–sediment interactions, two 25 cm long sediment cores from contrasting regions in the Central Indian Basin have been examined. Site TVBC 26 in the northern siliceous realm (10°S, 75·5°E) is organic‐C rich with 0·3 ± 0·09% total organic carbon. Site TVBC 08 in the southern pelagic red clay realm (16°S, 75·5°E), located on the flank of a seamount in a mid‐plate volcanic area with hydrothermal alterations of recent origin, is organic‐C poor (0·1 ± 0·07%). Significantly higher bacterial viability under anaerobic conditions, generally lower microbial carbon uptake and higher numbers of aerobic sulphur oxidizers at the mottled zones, characterize core TVBC 26. In the carbon‐poor environment of core TVBC 08, a doubling of the ¹⁴C uptake, a 250 times increase in the number of autotrophic nitrifiers, a four‐fold lowering in the number of aerobic sulphur oxidizers and a higher order of denitrifiers exists when compared with core TVBC 26; this suggests the prevalence of a potentially autotrophic microbial community in core TVBC 08 in response to hydrothermal activity. Microbial activity at the northern TVBC 26 is predominantly heterotrophic with enhanced chemosynthetic activity restricted to tan‐green mottled zones. The southern TVBC 08 is autotrophic with increased heterotrophic activity in the deepest layers. Notably, the bacterial activity is generally dependent on the surface productivity in TVBC 26, the carbon‐rich core, and mostly independent in TVBC 08, the carbon‐poor, hydrothermally influenced core. The northern sediment is more organic sink‐controlled and the southern sediment is more hydrothermal source‐controlled. Hydrothermal activity and associated rock alteration processes may be more relevant than organic matter delivery in these deep‐sea sediments. Thus, this study highlights the relative importance of hydrothermal activity versus organic delivery in evoking different microbial responses in the Central Indian Basin sediments.     

Basin structures and sediment accumulation in the Baikal Rift Zone: Implications for Cenozoic intracontinental processes in the Central Asian Orogenic Belt

In this paper we present a review of sedimentological, geomorphological, lithological, geochronological and geophysical data from major, minor and satellite basins of the Baikal Rift Zone (BRZ) and discuss various aspects of its evolution. Previously, the most detailed sedimentological data have been obtained from the basins of the central BRZ, e.g., Baikal, Tunka and Barguzin, and have been used by many scientists worldwide. We add new information about the peripheral part and make an attempt to provide a more comprehensive view on BRZ sedimentation stages and environments and their relations to local and regional tectonic events. A huge body of sedimentological data was obtained many years ago by Soviet geologists and therefore is hardly accessible for an international reader. We pay tribute to their efforts to the extent as the format of a journal paper permits. We discuss structural and facial features of BRZ sedimentary sequences for the better understanding of their sedimentation environments. In addition, we review tectono-sedimentation stages, neotectonic features and volcanism of the region. Finally, we consider the key questions of the BRZ evolution from the sedimentological point of view, in particular, correlation of Mesozoic and Cenozoic basins, bilateral growth of the Baikal rift, Miocene sedimentation environment and events at the Miocene/Pliocene boundary, Pliocene and Pleistocene tectonic deformations and sedimentation rates. The data from deep boreholes and surface occurrences of pre-Quaternary sediments, the distribution of the Pleistocene sediments, and the data from the Baikal and Hovsgol lakes sediments showed that 1) BRZ basins do not fit the Mesozoic extensional structures and therefore hardly inherited them; 2) the Miocene stage of sedimentation was characterized by low topography and weak tectonic processes; 3) the rifting mode shifted from slow to fast at ca. 7–5 Ma; 4) the late Pleistocene high sedimentation rates reflect the fast subsidence of basin bottoms.     

Relationship between chemical composition and magnetic susceptibility in sediment cores from Central Indian Ocean Basin

Three sediment cores in a north-south transect (3°N to 13°S) from different sediment types of the Central Indian Ocean Basin (CIOB) are studied to understand the possible relationship between magnetic susceptibility (χ) and Al, Fe, Ti and Mn concentrations. The calcareous ooze core exhibit lowest χ (12.32 × 10⁻⁷ m³ kg⁻¹), Al (2.84%), Fe (1.63%) and Ti (0.14%), terrigenous clay core with moderate χ (29.93 × 10⁻⁷ m³ kg⁻¹) but highest Al (6.84%), Fe (5.20%) and Ti (0.44%), and siliceous ooze core with highest χ (38.06 × 10⁻⁷ m³ kg⁻¹) but moderate Al (4.49%), Fe (2.80%) and Ti (0.19%) contents. The distribution of χ and detrital proxy elements (Al, Fe, and Ti) are identical in both calcareous and siliceous ooze. Interestingly, in terrigenous core, the behaviour of χ is identical to only Ti content but not with Al and Fe suggesting possibility of Al and Fe having a non-detrital source. The occurrence of phillipsite in terrigenous clay is evident by the Al-K scatter plot where trend line intersects K axis at more than 50% of total K suggesting excess K in the form of phillipsite. Therefore, the presence of phillipsite might be responsible for negative correlation between χ and Al (r = −0.52). In siliceous ooze the strong positive correlations among χ, Al_exc and Fe_exc suggest the presence of authigenic Fe-rich smectite. High Mn content (0.5%) probably in the form of manganese micronodules is also contributing to χ in both calcareous and siliceous ooze but not in the terrigenous core where mean Mn content (0.1%) is similar to crustal abundance. Thus, χ systematically records the terrigenous variation in both the biogenic sediments but in terrigenous clay it indirectly suggests the presence of authigenic minerals.     

Current radiation environment in the Central Ecological Zone of the Baikal Natural Territory

The main natural and human-induced radiation factors were assessed on the basis of long-term targeted radioecological studies in the Central Ecological Zone of the Baikal Natural Territory as a world heritage site. We identified areas with a problematic level of different radiation parameters determining the current radiation environment. Such areas should be taken into account in the development and implementation of nature management plans in the Baikal region, including ecotourism.     

Origin of Lau Basin Rise sediment

The chemistry and mineralogy of sediments in the vicinity of the active rise in the Lau Basin can be accounted for by weathering of tholeiitic basalts exposed in the Basin, the introduction of pumice fragments derived from the Tonga Ridge, precipitation of ferromanganese minerals from sea water and pore water addition.     

Research advance in sediment provenance of the Qiongdongnan Basin

<正>1 Introduction Sediment provenance study,as an important part of basin analysis,is a key for source area definition,paleogeographic reconstruction,sediment transport route identification,and tectonic evolution(Haughton et al.,1991;Morton et al.,1999;Fontanelli et al.,2009;Cawood et al.,2012).The Qiongdongnan Basin(QDNB),lies in the northwestern passive continental margin of the South     

The impact of technogenic factors on the seismicity of the Kuznetsk Basin region and Lake Baikal

Using the materials from the catalogue of seismic events in the Siberian region, we estimated the impact of man’s activity on natural seismicity. Local man’s intervention into natural processes has been studied by the examples of commercial explosions during the quarry mineral mining in the Kuznetsk Basin and the exploitation of the railroad site along the shore of Lake Baikal. Seismic emission is shown to change with time under the impact of powerful monochromatic vibrators on the environment.     

Implications of REE incorporation and host sediment influence on the origin and growth processes of ferromanganese nodules from Central Indian Ocean Basin

This study presents new major, trace and REE data for thirty-five ferromanganese nodules recovered from areas representing three different sediment types (silic...     

Strain localization due to structural in-homogeneities in the Central European Basin System

The large-scale crustal deformations observed in the Central European Basin System (CEBS) are the result of the interplay between several controlling factors, among which lateral rheological heterogeneities play a key role. We present a finite-element integral thin sheet model of stress and strain distribution within the CEBS. Unlike many previous models, this study is based on thermo-mechanical data to quantify the impact of lateral contrasts on the tectonic deformation. Elasto-plastic material behaviour is used for both the mantle and the crust, and the effects of the sedimentary fill are also investigated. The consistency of model results is ensured through comparisons with observed data. The results resemble the present-day dynamics and kinematics when: (1) a weak granite-like lower crust below the Elbe Fault System is modelled in contrast to a stronger lower crust in the area extending north of the Elbe Line throughout the Baltic region; and (2) a transition domain in the upper mantle is considered between the shallow mantle of the Variscan domain and the deep mantle beneath the East European Craton (EEC), extending from the Elbe Line in the south till the Tornquist Zone. The strain localizations observed along these structural contrasts strongly enhance the dominant role played by large structural domains in stiffening the propagation of tectonic deformation and in controlling the basin formation and the evolution in the CEBS.     

Composition of macrobenthos from the Central Indian Ocean Basin

The deep sea is well known for its high faunal diversity. But the current interest in its abundant polymetallic nodules, poses a threat to the little known benthic organisms surviving in this unique environment. The present study is the first attempt to document the Indian Ocean abyssal benthic diversity of macroinvertebrates and to investigate its relation to the surface primary production (chl-a), sediment labile organic matter, organic carbon and texture. The present study is based on 87 individuals. Altogether 39 macroinvertebrate genera were obtained from water depths of 4500–5500 m from 23 box cores. Reduction in macrobenthic density was seen towards the southern latitudes. The area was dominated by deposit feeding macrobenthos. Vertically, the fauna was distributed down to 30 cm depth, with the highest faunal density in the top 2–5 cm sediment section. The values for population density were strongly correlated with surface water chl-a and sediment protein, indicating supply of fresh organic matter as a critical factor for maintaining the deep sea benthic diversity and abundance.     

鄂尔多斯盆地中部寒武纪岩相古地理研究

鄂尔多斯盆地寒武系是一套海相沉积地层,岩性以碳酸盐岩为主夹少量碎屑岩。近年来,该地区的寒武系被认为具有很大的勘探潜力,但迄今为止尚未发掘到大型储层。以往的研究主要集中在东、西和南部,而中部的研究严重缺乏,这阻碍了该区油气勘探的突破。笔者通过对56个钻孔岩心和13条野外露头进行单井划分,根据120块镜下薄片和岩石组合特征,识别出2种沉积相：斜坡相和台地相2种沉积相。在此基础上,开展联井对比,以盆地中部为中心划分出东西、南北2条贯穿盆地的连井剖面,探讨不同时期的沉积厚度和沉积相变规律。研究认为,鄂尔多斯盆地寒武系形成于海侵背景下,在经历了辛集期后,海水从盆地的西部和南部向内部推进。到张夏期,海进达到鼎盛,盆地绝大部分区域被海水淹没,只留下零星低矮的古陆。到三山子期,海进由盛转衰,开始发生海退。笔者重建了“一隆四凹”的古地理沉积格局,还原了盆地中部寒武纪构造沉积演化过程。     

Rare earth element geochemistry of Lake Baikal sediment: its implication for geochemical response to climate change during the Last Glacial/Interglacial transition

Sediments deposited on the bottom of Lake Baikal have contributed to the understanding of a long-term environmental history of continents. Rare earth elements (REEs) along with major elements and loss on ignition (LOI) of Baikal sediments were determined with the aim of evaluating their suitability for a new paleoenvironmental proxy. Our interest is concentrated on paleoenvironmental change during the Last Glacial/Interglacial transition (LGIT). Chondrite-normalized REE patterns for Baikal sediments show a similar variation to those for typical upper continental crustal materials. Three parameters of (La/Yb)_n (n: chondrite-normalized value) ratio, ΣREE/TiO₂ and Eu anomaly were used to express detailed characteristics of Baikal sediments. Depth profile of (La/Yb)_n ratio shows abrupt change, whose timing corresponds to the beginning of climatic warming inferred from the profiles of SiO₂/TiO₂ and LOI. In addition, (La/Yb)_n ratio, ΣREE/TiO₂ and the degree of Eu anomaly correlate with each other. This suggests that inflow process of particulate materials into the lake may have changed during the LGIT. The analytical results of this study lead to the conclusion that REE is a useful paleoenvironmental proxy in the Baikal region.     

Ferromanganese Crusts in the Central Basin,Sea of Japan

The paper presents a comparative analysis of ferromanganese crusts and concretions (FMC) recovered during the dredging of 14 seamounts in the Central Basin, Sea of Japan. The major rock-forming elements in FMC are Mn, Fe, and Si. In terms of the Mn content, the studied 53 samples are divided into four groups: (1) less than 10% (given than concentrations of 2–8% are lacking); (2) 10?25%; (3) 25?42%; and (4) 42?63%. The (Mn + Fe)/Si ratio increases from group 1 to group 4, and average value in them is 1.6, 2.5, 6.7, and 70.7, respectively. Taking Fe/Si and Mn/Si values into consideration, concretions of these groups belong to the following varieties: (1) ferrosiliceous; (2) mangano-ferrosiliceous; (3) siliceous-ferromanganese, and (4) manganiferous. The highest concentration of nonferrous metals is observed in FMC of groups 2 and 3. Their concentration is slightly lower in group 4 and very low in group 1. The internal structure of FMC in these groups is variable, suggesting their different formation settings. Crusts of group 1 were formed during the precipitation of Mn from a hydrothermal plume on the older ferrosiliceous crusts. Crusts of groups 2 and 3 were likely formed by the diffuse percolation of Mn-bearing hydrothermal solutions along fractures and weakened zones in volcanic rocks, with their subsequent cementation by manganiferous hydroxides from sedimentary or volcaniclastic deposits on seamounts. Crusts of group 4 were formed at sites of the hydrothermal solution discharge on the seafloor. FMC of different groups are recovered during the dredging of most volcanic seamounts in the Central Basin (Sea of Japan). Since the dredging is accomplished at a depth interval of a few hundreds of meters, the detection of concretions of a certain type is governed by the distance to the nearest hydrothermal source.     

Thin-skinned tectonics in the Central Basin of the Iranian Plateau in the Semnan area,Central Iran

During continent–continent convergence of the Arabian and Eurasian plates, and after the late Eocene inversion of a back-arc rift, the Iranian Plateau underwent broad subsidence resulting in the formation of the Central Basin (Morley et al., 2009). New 2D seismic data acquired by National Iranian Oil Company (NIOC) in the NW–SW-trending arm of the Central Basin suggest that during the main stage of shortening (middle–late? Miocene to Pliocene), strain concentrations resulted in the development of the thin-skinned Kuh-e-Gachab, Kuh-e-Gugerd, Garmsar and Sorkh-e-Kuh structures. These structures are built of Oligocene–Miocene/Pliocene(?) rocks belonging to the Lower Red, Qom and Upper Red formations. Seismic data suggest that one of these structures comprises the south-verging Kuh-e-Gachab anticline, which is bounded by the N-dipping Kuh-e-Gachab thrust and cored by a complex array of thrust sheets forming a triangle zone. During the deformation process, two salt evaporate levels played a significant role as detachment horizons. The main detachment horizon was rooted within the Lower Red Formation, whereas the second detachment horizon was located along evaporites belonging to the Upper Red Formation. Variations in the thin-skinned style of deformation between the larger triangle zone in the western part of the Kuh-e-Gachab structure contrasts with less shortening in the smaller triangle zone to the east. This suggests that the change resulted from the increase of thickness of the mobile detachment horizon to the east. Contraction deformations are still active south of the Alborz Mountains, which is confirmed by GPS data and present-day seismicity.     

Determination of sediment provenance at drift sites using hydrogen isotopes and unsaturation ratios in alkenones

The large (∼20‰) hydrogen isotopic gradient in surface waters of the northwest Atlantic Ocean is exploited to track changes in the source of alkenones to the Bermuda Rise sediment drift. Cultures of the predominant alkenone-producing coccolithophorid, E. huxleyi, were grown in deuterium-enriched seawater and shown to possess alkenones with a D/H ratio that closely tracked the water D/H ratio (r² = 0.999, n = 5 isotopic enrichments) with a fractionation factor (α) between 0.732 and 0.775. A hydrogen isotopic depletion of -193 ± 3‰ (n = 9) was measured in alkenones from suspended particles relative to seawater in the subpolar and subtropical northwest Atlantic Ocean. This value was used to calculate the water δD values in which alkenones from Bermuda Rise sediment were synthesized, and by extension, the water mass in which they were produced. Applying this technique we find that 60% to 100% of the alkenones in late Holocene Bermuda Rise sediment were produced in deuterium-depleted subpolar water to the northwest of the drift. To reconcile values of the alkenone unsaturation ratio (U^k′₃₇), a widely used proxy for sea surface temperature, with the δD values of alkenones in late Holocene sediments from the Bermuda Rise at least three sources of sediment must be invoked: a cold, very isotopically depleted source, almost certain to be the Scotian Margin; a warm, moderately isotopically-depleted source, likely to be the northwestern edge of the subtropical gyre; and a cold, isotopically enriched source, which we hypothesize to be the subpolar waters overlying the main branch of North Atlantic Deep Water flowing southwest from the Nordic Seas.     

Geologic framework for the coal-bearing rocks of the Central Appalachian Basin

Coal production has been an important economic factor in the Central Appalachian Basin. However, regional stratigraphic and structural relationships of the coal-bearing rocks of the basin have been poorly understood due to numerous separate nomenclatural schemes employed by various states. In order to estimate coal resources and understand mechanisms controlling the distribution of coal within the basin, a reliable geologic framework is necessary. Seven detailed cross sections across the Central Appalachian Basin were constructed in order to examine the stratigraphic and structural framework of the coal-bearing rocks in the basin. The cross sections were based on more than 1000 oil and gas well logs, measured sections, and borehole information from Kentucky, Ohio, Tennessee, Virginia and West Virginia.The cross sections revealed three main points discussed here: southeast thickening of the Pennsylvanian strata, uncomfortable northwestward onlapping relationship of Lower Pennsylvanian strata over underlying Lower Pennsylvanian and Mississippian strata and regional continuity of beds. The cross sections, geologic mapping, coal-resource studies, extensive new highway exposures and the occurrence of tonstein beds indicate that many coal beds and marine strata are laterally extensive, albeit locally variable across the basin. Certain quartzose sandstone bodies are also extensive over large areas of the basin.Existing stratigraphic nomenclature schemes obscured the geologic framework of the basin, so a new unified nomenclature scheme was devised to better describe stratigraphic features of the basin. The new stratigraphic nomenclature, now only formalized for Kentucky, was based on key stratigraphic units that proved to be extensive across the basin. Lower and Middle Pennsylvanian rocks are now recognized as the Breathitt Group (the Breathitt Formation was elevated to group rank). The Breathitt Group was subdivided into eight coal-bearing formations by relatively thick marine strata, and, in the lower part of the Breathitt Group, by quartzose sandstone formations. The new coal-bearing units are formally ranked as formations and, in ascending order, are the Pocahontas, Bottom Creek, Alvy Creek, Grundy, Pikeville, Hyden, Four Corners and Princess Formations. The quartzose sandstone units are also formally ranked as formations and are, in ascending order, the Warren Point, Sewanee, Bee Rock and Corbin Sandstones. The sandstone formations were previously recognized units in some states, but have been extended (formally in Kentucky) across the basin. The key stratigraphic marine units are formally ranked as members, and are, in ascending order, the Betsie Shale Member, the Kendrick Shale Member, Magoffin Member and Stoney Fork Member.