MINERALOGY OF COASTAL DEPOSITS OF NORTH-WESTERN SEA OF JAPAN   总被引：1，自引：0，他引：1  

N.G.Razjigaeva  L.A.Ganzey 《海洋地质与第四纪地质》1991,(4)

Distribution of heavy, light and clay minerals in Late Pleistocene—Holocene deposits from different coastal environments (beaches, lagoons, dunes, relict lakes, ria bays and inlets, open inlets) was analysed. It was established that mineralogical composition of coastal deposits was a result of provenance and its hypergenous changes, transformation of material within transit zone, and accumulative conditions of inshore zone. Contents of stable minerals increase in deposits of the inlets confined to mouths of the small streams and in horizons of the sections, formed during regressive phases. Unstable minerals amount is higher in deposits of inlets, confined to mouths of the large river. The clay mineral fraction of shelf sediments consists mostly of illite. Authigenous pyrites dominate in deposits of ria bays, lagoons and relict lakes, formed during transgressive phases. Volcanic glass, found in deposits, is product of Holocene eruptions of Baegdusan (Baitushen) Volcano.  相似文献   

辽东早元古代碳酸盐岩的地质地球化学特征     

王仲会  马青 《吉林大学学报(地球科学版)》1991,(1)

辽东半岛早元古宙坳拉槽内靠近优地槽一侧,分布着一套复杂碳酸盐岩系,其下部和海底拉斑玄武岩呈沉积接触,或薄互层状共存,与火山凝灰岩互层。底部碳酸盐岩主要为钙型,向上过渡为钙镁型碳酸盐,其中含有数层由海底喷气作用形成的硅质岩,上部的硅质条带状碳酸盐岩中含有条带状、条纹状喷气沉积的硫化物。碳酸盐岩系顶部为厚层质纯镁质碳酸盐岩,局部含巨厚层状菱镁矿。岩系中碳酸盐岩、硅质岩、金属硫化物的稀土特征和铁锰指数具有一致性。铅同位素研究表明它们源于下地壳。有证据显示:碳酸盐岩系是在一定水深条件下由沉积作用形成的。这和碳氧同位素碳研究的结果吻合。种种特征表明这套复杂的碳酸盐岩系具有其独特性,可能暗示着一种特殊的碳酸盐岩形成方式。  相似文献   

Grounding line proximal sediment characteristics at a marine‐based,late‐stage ice stream margin     

《第四纪科学杂志》2017,32(4):463-474

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Biogeochemistry of southern Australian continental slope sediments     

H. H. Veeh  D. T. Heggie  A. J. Crispe 《Australian Journal of Earth Sciences》2013,60(4):563-575

Sediment cores from the middle to lower slope of the southern continental margin of Australia between the Great Australian Bight and western Tasmania are compared in terms of marine and terrigenous input signals during the Holocene. The mass accumulation rates of carbonate, organic carbon, biogenic Ba, and Al are corrected for lateral sediment input (focusing), using the inventory of excess ²³⁰Th in the sediment normalised to its known production rate in the water column above each site. The biogenic signal is generally higher in the eastern part of the southern margin probably due to enhanced productivity associated with seasonal upwelling off southeastern South Australia and the proximity of the Subtropical Front, which passes just south of Tasmania. The input of Al, representing the terrigenous signal, is also higher in this region reflecting the close proximity of river runoff from the mountainous catchment of southeastern Australia. The distribution pattern of Mn and authigenic U, together with pore‐water profiles of Mn⁺⁺, indicate diagenetic reactions driven by the oxidation of buried organic carbon in an oxic to suboxic environment. Whereas Mn is reduced at depth and diffuses upwards to become immobilised in a Mn‐rich surface layer, U is derived from seawater and diffuses downward into the sediment, driven by reduction and precipitation at a depth below the reduction zone of Mn. The estimated removal rate of U from seawater by this process is within the range of U removal measured in hemipelagic sediments from other areas, and supports the proposition that hemipelagic sediments are a major sink of U in the global ocean. Unlike Mn, the depth profile of sedimentary Fe appears to be little affected by diagenesis, suggesting that little of the total Fe inventory in the sediment is remobilised and redistributed as soluble Fe.  相似文献   

Spatial variability in fluvial style and likely responses to sea‐level change,Herbert River,Queensland     

K. J. Woolfe  P. Larcombe  A. R. Orpin  R. G. Purdon 《Australian Journal of Earth Sciences》2013,60(4):689-694

In broad terms, fluvial systems can be considered as comprising two basic geomorphologic features, a channel and its floodplain (overbank), each of which may accumulate sediment or undergo erosion. The sedimentary relationships between channels and floodplains, the resultant sedimentary architecture and the form of the dependent landscape may all be considered in terms of the relative rates of channel and floodplain aggradation and/or erosion. Using this approach, the Herbert River in north Queensland can be divided into seven ‘fluvial fields’. By considering the likely migration directions of field boundaries in the lower floodplain we conclude that, contrary to many sequence‐stratigraphic models, lowering sea‐level would drive a general aggradation of the system on the Great Barrier Reef shelf, whereas a sea‐level rise would cause further incision of the modern coastal plain.  相似文献   

Silica‐rich layering at Blanche Point,South Australia     

J. B. Jones  M. J. Fitzgerald 《Australian Journal of Earth Sciences》2013,60(4):529-551

The chemistry and mineralogy of much of the Late Eocene Blanche Point Formation of South Australia show that biogenic and volcanogenic products were the only significant contributor to the sedimentary record. Intermittent volcanic activity followed by dissolution of the resultant silicic ash and small scale migration of silicon with reprecipitation as the oxide, provides the simplest and most likely explanation for the repetitive nature of the silicification. Seemingly, this was controlled by local silica concentrations which in turn were apparently controlled by the biota. Changes in circulation patterns and/or water depth may have initiated the environmental variations recorded in the formation.  相似文献   

Fjord stratigraphy and processes – evidence from the NE Atlantic Fensfjorden system     

BERIT OLINE HJELSTUEN  HEIDI KJENNBAKKEN  VEGARD BLEIKLI  REMI ANTHONI ERSLAND  SIGURD KVILHAUG  CHRISTINE EULER  SVANHILD ALVHEIM 《第四纪科学杂志》2013,28(4):421-432

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Sedimentation of overbank floods in the confined complex channel–floodplain system of the Lower Yellow River,China          下载免费PDF全文

Min Zhang  He Qing Huang  Paul A. Carling  Mingwu Zhang 《水文研究》2017,31(20):3472-3488

The channel boundary conditions along the Lower Yellow River (LYR) have been altered significantly since the 1950s with the continual reinforcement and construction of both main and secondary dykes and river training works. To evaluate how the confined complex channel–floodplain system of the LYR responds to floods, this study presents a detailed investigation of the relationship between the tempo‐spatial distribution of sedimentation/erosion and overbank floods occurred in the LYR. For large overbank floods, we found that when the sediment transport coefficient (ratio of sediment concentration of flow to flow discharge) is less than 0.034, the bankfull channel is subject to significant erosion, whereas the main and secondary floodplains both accumulate sediment. The amount of sediment deposited on the main and secondary floodplains is closely related to the ratio of peak discharge to bankfull discharge, volume of water flowing over the floodplains, and sediment concentration of overbank flow, whereas the degree of erosion in the bankfull channel is related to the amount of sediment deposited on the main and secondary floodplains, water volume, and sediment load in flood season. The significant increase in erosion in the bankfull channel is due to the construction of the main and secondary dykes and river training works, which are largely in a wide and narrow alternated pattern along the LYR such that the water flowing over wider floodplains returns to the channel downstream after it drops sediment. For small overbank floods, the bankfull channel is subject to erosion when the sediment transport coefficient is less than 0.028, whereas the amount of sediment deposited on the secondary floodplain is associated closely with the sediment concentration of flow. Over the entire length of the LYR, the situation of erosion in the bankfull channel and sediment deposition on the main and secondary floodplains occurred mainly in the upper reach of the LYR, in which a channel wandering in planform has been well developed.  相似文献   

Recognition of the Minoan tephra in the Acigöl Basin,western Turkey: implications for inter‐archive correlations and fine ash dispersal     

R. SULPIZIO  M. C. ALÇIÇEK  G. ZANCHETTA  L. SOLARI 《第四纪科学杂志》2013,28(4):329-335

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Depositional and palaeoenvironmental variation of lower Turonian nearshore facies in the Bohemian Cretaceous Basin,Czech Republic     

《Cretaceous Research》2015

Dark grey strata belonging to the basal horizons of the Bílá Hora Formation (lower Turonian) were exposed during quarrying at the locality of Plaňany (Bohemian Cretaceous Basin). Based mainly on quarry maps, the early Turonian rocky bottom was reconstructed in the area of about 14,800 m². Two sedimentologic and palaeoecological settings were recognized in the area. Dark grey deposits form part of the first setting, representing a fill of large and deep depressions on the northern foot of the Plaňany elevation. The second setting with a phosphatic lag is located on the elevated part of the area. Dark grey sedimentation belongs to the UC6a and particularly to the UC6b nannoplankton zones. During the latter zone the dark sedimentation passed upwards into light siltstones. The enrichment of C_org and S, clay minerals with an important kaolinite peak, formation of framboidal pyrite and the enrichment of macrofauna and phosphatic particles are characteristic of the basal portions of the dark deposits. The sulphate reduction zone is suggested for this sedimentary environment. In the associations of phosphatic particles, shark coprolites, faecal pellets and sponge fragments prevail. No phosphatic lag is developed. On the other hand, the phosphatic lag directly overlying the Cenomanian relics is most characteristic of the second setting. This lag is a product of sedimentary condensation, characterized by a long-lasting concentration of phosphatic particles and phosphogenesis, accompanied by encrustation of closely adjacent free rock surfaces by a faunal community with Terebella. Additional biostratigraphic data presently contributed to a proposed correlation of both settings. Micropalaeontological data (foraminifera, palynomorphs, nannoplankton) indicate that the phosphatic lag and basal dark grey deposits may be approximately coeval. The stagnant depositional conditions with only very slow sea-level rise are thought to have lasted for a relatively long period that includes a significant part of the Whiteinella archaeocretacea Zone (lowermost Turonian). In elevated parts, condensation could proceed under conditions of prevailingly weak currents and strong oxidation of organic matter, while decomposition of organic matter was probably very slow and incomplete in depressions below the elevation. The sedimentary condensation in both settings is highlighted by the remarkable formation of abundant glauconite in local deposits.  相似文献