Ionic composition of pore water in shallow shelf deposits of the Laptev Sea

The cationic and anionic compositions of pore water in shallow deposits of Buor-Khaya Bay is studied. Significant concentration heterogeneity of the vertical ionic profile in the studied drill columns is shown. It is established that the vertical ionic profile of shelf deposits of the Laptev Sea is basically formed under the influence of thawing of underwater permafrost, hydrodynamic conditions, the water mass, and heat flows and depends on the lithological and granulometric types of the deposits. The highest concentrations of ions are registered in plant detritus represented by ground grass vegetation. A relationship between the ionic composition of pore water and cryogenic state of the sequence and its variability is demonstrated using the method of major components.     

Ashes of Chanbaishan volcano in sediments of the Sea of Japan: Identification from data on micro- and rare-earth elements and datings of their eruptions

We have first done the correlation of ashes and tephra of Chanbaishan volcano sampled on its slopes with the ash interbeds of the Japan Sea bottom.     

Marker tephra layers in the late quaternary deposits of the Sea of Okhotsk as evidence of catastrophic eruptions in the Nemo caldera complex (Onekotan Island, Kuril Islands)

On the basis of complex studies of tephra layers (morphology of volcanic glass particles, chemical composition of glass particles and minerals, and REE distribution), marker tephra layers (K2, K3) were distinguished in the stratigraphic columns in the area of the Sea of Okhotsk. The areas of distribution of tephra layers and their age datings were determined. Tephra layers are shown to be similar in their chemical composition. They are correlated with strong explosive eruptions in the Nemo caldera complex on Onekotan Island (northern part of the Kuril Islands) in the Late Pleistocene.     

开江-梁平陆棚东南延伸部分——建南陆棚的发现

自王一刚发现开江-梁平陆棚后,作者对其东南延伸部位进行了追踪。通过地表露头剖面及钻井、地震资料等研究后认为,长兴期开江-梁平陆棚自宣汉达县、梁平及开江地区向东南延伸至建南地区,称之为建南陆棚,该陆棚可能与东部的鄂西陆棚相连。建南陆棚与开江-梁平陆棚既有相似性也有重大差别。相似性表现在两方面,一是沉积物岩性相似,都为泥晶灰岩;二是陆棚边缘都发育生物礁,生物礁顶部发育生屑滩白云岩储层。差别主要体现在四个方面:一是水体深度,建南陆棚水浅,开江-梁平陆棚水深,深水与浅水的交汇处在涪陵地区中石化二维地震剖面线TB16与TB17之间;二是斜坡坡度,开江-梁平陆棚边缘斜坡坡度陡,建南陆棚斜坡坡度缓;三是生物礁规模,开江-梁平陆棚边缘生物礁、白云岩储层厚度大,建南陆棚边缘生物礁、白云岩储层厚度小;四是陆棚发育时间,建南陆棚仅发育于长兴早中期,晚期因填平补齐而消失,开江-梁平陆棚发育于整个长兴期。建南陆棚与周边构成碳酸盐缓坡沉积模式,生物礁规模较小,生物礁是优质储发育的主要地区。     

The first ever application of electromagnetic sounding for mapping the submarine permafrost table on the Laptev Sea shelf

The inconsistency between the position of the submarine permafrost table in the East Arctic seas revealed by simulation and anomalies in the distribution of dissolved methane associated with ascending torchlike ejections of bubbling methane made it necessary to develop a representative geophysical express method, which allows the position of the submarine permafrost table to be determined. The method is based on sounding of the generated primary electromagnetic field in the near zone of the medium and measurement of the induced secondary EM field. The reliability of the method is confirmed by core drilling in the Laptev Sea.     

A pilot acoustic experiment to determine the coordinates of a submarine object in the shelf zone of the Sea of Japan

Doklady Earth Sciences -     

Genetic suppositions of oil and gas formation and conditions of hydrocarbon deposits in Mesozoic-Cenozoic sediments in the Caspian Sea shelf

Source rocks are present in all the stratigraphic units of the Mesozoic-Cenozoic deposits of the Turkmen shelf in the Caspian Sea. The highest source rock potential is characteristic of I terrigenous and carbonate-terrigenous rocks of Middle Jurassic age, and the Aptian, Paleogene, Neogene and Apsheron stages of the Quaternary system. To reveal the formation conditions of hydrocarbon deposits within Southwestern Turkmenistan, the principle of chemical thermodynamics is primarily used via the calculation of the free energy of gaseous hydrocarbons. This showed that hydrocarbon deposits within the topmost depositional complex (the red-colored strata of the Middle Miocene at the Akchagyl and Apsheron stages) are syngenetic; their formation was due to lateral migration from even-aged deposits from depression zones neighboring the uplifts.     

An assessment of the risk from future eruptions of the Soufriere volcano of St. Vincent,West Indies

The Soufriere volcano is a 1220 m high stratovolcano which occupies the northern part of the island of St. Vincent. It is one of the most active centres of volcanism in the Caribbean and has a record of activity dating back to the Pleistocene. Historic eruptions (since 1718) have caused over 1600 deaths and resulted in damage to property valued in excess of 4.8 million USD. In addition, current development plans for the area point towards increased risk of disastrous consequences from future activity at the volcano.All aspects of risk relevant to the volcano, are discussed, with particular emphasis on the manner in which these are perceived and on the question of acceptable risk. A method is presented for use in risk assessment of volcanic hazard and a number of risk zones are defined for the Soufriere volcano. Numerical estimates of the relative loss expected within each zone are obtained from a consideration of the value of property at risk, its vulnerability to the hazardous volcanic events and the expected spatial impact of volcanic events. Such estimates suggest that the northern-most third of the island is at least ten times more at risk than areas further south. The likelihood of death and destruction is extreme in such high risk areas, while the most feasible method of loss reduction is evacuation before an eruption occurs.Formerly at Department of Earth Sciences, University of Leeds, Leeds LS2 9JT, United Kingdom.     

Paleogeography of the Laptev Sea eastern shelf in the first half of Holocene based on faunal and palynological evidence

The Holocene paleogeography of the Laptev Sea eastern shelf is reconstructed based on mollusks, foraminifers, ostracodes, spores and pollen found for the first time. Environmental changes in the course of the postglacial (Holocene) transgression are detectable from quantitative analysis of three ostracod assemblages. Three phases of the transgression are established based on ostracode assemblages from the AMS ¹⁴C-dated core from the ancient valley of Yana River, central part of the Laptev Sea eastern shelf. After the first phase of coastal brackish-water environment (11.3–11.1 ka), shallow-water marine taxa appeared in the transitional phase (11.1–10.3 ka), and the third phase of modern sea conditions commenced 10.3 ka ago. Spore and pollen assemblages from the core indicate that the early Holocene land vegetation was dominated by tundra plant communities adapted to climatic conditions not warmer than at present. In the interval of 9.3–8.0 ka, climate was increasingly humid and warm, and forest-tundra vegetation occupied more favorable zones of the region.     

The role of volcanic eruptions in blocking the drainage leading to the Dead Sea formation

The shrinkage of the Lisan Lake (LL) to form the recent Dead Sea (DS) was mainly a result of the reduction of the catchment area from around 157,000 km² during Late Pleistocene to 43,000 km² presently. The reduction in the catchment area resulted from the eruption and spread of the basalt flows of Jabal Arab-Druz (JAD), which together with the resulting deposition of thick rock debris and gravels occupied the drainage system. The filling of the pre-basalt drainage system, which used to feed the Dead Sea, with basalts and alluvial sediments blocked the inflows from reaching the Dead Sea. Local base levels along the basalt flow boarders such as Azraq Oasis, Sirhan Basin and Damascus Oasis, and numerous pools and mud flats were created.     

Explosive eruptions of the Sarychev Peak volcano in the Holocene on Matua Island, the Central Kuriles: The tephra geochemistry

The first results of tephrochronological studies of the Sarychev Peak volcano on Matua Island in the Central Kuril Islands are presented and the eruptive evolution of the volcano in the Holocene is reconstructed. The volcanic products are typified and the general style of their geochemical evolution is reviewed on the basis of the distribution of the petrogenic oxides and trace elements in tephra samples taken bed-by-bed from the reference section of the soil-pyroclastic cover on Matua Island. The horizons of transit ashes are identified.     

川南沐川地区首次发现宣威组底部古风化壳-沉积型铌、稀土矿

1 研究目的(Objective) 本项目为四川省自然资源厅2020年省政府性投资地质勘查项目,总体目标任务是对川南沐川县建和乡宣威组(P3x)底部的铌、稀土矿进行勘查,提交可供普查的矿产地1处.本项目设计钻孔揭露宣威组(P3x)与峨眉山玄武岩(P3e)界线,评价宣威组(P3x)底部古风化壳含矿性,希望在"三稀"找矿方...     

西藏羌塘中部独泉沟地区发现青藏高原首例富锰矿

独泉沟锰矿是青藏高原发现的首例富锰矿,成矿元素分析结果表明,矿石中Mn平均品位为41.95%,达到了Ⅰ级富锰矿石的品位标准。该锰矿体主要呈层状、似层状产出于上二叠统—下三叠统天泉山组复理石碎屑岩内;矿体地表部分为残坡积,残坡积范围宽20~30m,长约50m。根据产状及结构构造的差异,将研究区锰矿体分为层状锰矿体和脉状锰矿体,二者的矿石矿物皆是硬锰矿,脉石矿物以石英为主。初步研究认为,独泉沟锰矿是海相热水沉积型锰矿。作为青藏高原地区发现的首例富锰矿,独泉沟锰矿的发现填补了区内锰矿找矿工作的空白,对其成因的研究能为今后的找矿工作提供重要的线索和依据,在区域找矿方面具有一定的指示意义。     

西藏松多地区首次发现非金属矿——黑曜岩

最新区域地质调查发现,西藏工布江达县松多乡存在天然非金属矿——黑曜岩。该矿源地处青藏高原冈底斯板块上,发育于新生代年波组中。"球泡"状黑曜石清晰可见,部分达到宝石级别。初步研究显示,该黑曜岩是地壳部分熔融的产物。冈底斯成矿带上成矿种类以多金属为主,松多黑曜岩的发现不仅初步圈定了一个非金属矿点,还为区域后续找矿工作和考古学研究提供了重要线索。     

The first discovery of crinoids and cephalopod hooklets in the British Triassic

The Late Triassic Rhaetian stage is perhaps best known in south-west Britain for the bone beds of the Westbury Formation, but there are other fossil-rich horizons within this and the underlying Blue Anchor Formation. Samples from a borehole drilled at the Filton West Chord, and collected from exposures near Bristol Parkway railway station, have yielded significant fossil material from both of these formations. The assemblage recovered from the Blue Anchor Formation is similar to those from the lower Westbury Formation, yielding roughly equal proportions of chondrichthyans and osteichthyans. Assemblages recovered from the Westbury Formation are typical of those from the upper Westbury Formation, in being dominated by osteichthyans. The borehole samples have produced the first recorded evidence of crinoids in the British Triassic, and the first evidence of coleoid cephalopods, in the form of grasping hooklets, from the Rhaetian, and indeed the first from the British Triassic.     

The sources of metal contents in the shelf sediments from the Marmara Sea, Turkey

The shelf area is the largest morphological unit of the Marmara Sea and is subjected to increasing population, urbanization, and industrial activities. Metal contents (Al, Fe, Mn, Cu, Pb, Zn, Ni, Cr, Co and Hg) of the surface sediments from the shelf areas of the Marmara Sea generally do not indicate shelf-wide pollution. The variability of the metal contents of the shelf sediments is mainly governed by the geochemical differences in the northern and southern hinterlands. Northern shelf sediments contain lower values compared to those of the southern shelf, where higher Ni, Cr, Pb, Cu and Zn are derived from the rock formations and mineralized zones. However, besides from the natural high background in the southern shelf, some anthropogenic influences are evident from EF values of Pb, Zn and Cu, and also from their high mobility in the semi-isolated bay sediments. Anthropogenic influences are found to be limited at the confluence of Istanbul Strait in the northern shelf. However, suspended sediments along the shallow parts of the northern shelf were found to be enriched in Pb and Hg and to a lesser degree in Zn, reflecting anthropogenic inputs from Istanbul Metropolitan and possibly from the Black Sea via the Istanbul Strait.     

Transition from basin-plain to shelf deposits in the carboniferous flysch of Southern Morocco

In the Jebilet Palaeozoic inlier, 20 km north of Marrakech, there are extensive exposures of Carboniferous flysch deposits. Although there are some structural complications due to over-riding nappes with associated chaotic breccias, one clearly unbroken succession from basin-plain turbidites to shallow-marine deposits can be examined. The succession is more than 2 km thick and is dated as Upper Viscan in the uppermost part.The lowermost unit of B- and C-based turbidites shows no sequential organisation and is interpreted as a typical basin-plain association. Above this are similar turbidites arranged in thickening-upward sequences that may represent outer-fan or base-of-slope deposits. Succeeding these are thin-bedded turbidites with interbedded units formed by mass movement that represent a slope deposit. The overlying lenticular-bedded facies resembles previously described overflow deposits of submarine-fan channels, but is here interpreted as comprising storm-generated deposits on the outer shelf/upper slope. These deposits are genetically linked with the overlying parallel-laminated sandstones with irregular-rippled tops for which a storm-surge origin is suggested. The upper part of the succession shows cross-bedded, oolitic, bioclastic, sandy limestones with bipolar current structures sandwiched between low-energy siltstones containing thin-graded silt/sand beds. These are collectively interpreted as shelf deposits that formed under different depths due to transgressive-regressive events.The sequence differs from many described in the literature in that there is an absence of most submarine-fan facies. Locally a NNE-SSW basin strike is proposed with a basin margin to the ESE, but there is at present little control on regional palaeogeography.     

The First Find of Goethite Crusts in the Sea of Japan

Doklady Earth Sciences - Ferruginous (goethite) mixed-type hydrothermal–hydrogenetic crusts, which were found in the Sea of Japan for the first time, are described. Compared to manganese...