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1.
Palaeo-bottom current strength of the West Spitsbergen Current (WSC) and the influence of the Svalbard-Barents Sea Ice Sheet (SBIS) on the depositional environment along the northern Svalbard margins are poorly known. Two gravity cores from the southern Yermak Plateau and the upper slope north of Nordaustlandet, covering marine isotope stage (MIS) 1 to MIS 5, are investigated. Five lithofacies, based on grain size distribution, silt/clay ratio, content and mean of sortable silt (SS), are distinguished to characterise the contourite-dominated sedimentary environments. In addition, depositional environments are described using total organic carbon (TOC), total sulphur (TS) and calcium carbonate (CaCO3) contents of sediments. Facies A, containing coarse SS, suggests strong bottom current activity and good bottom water ventilation conditions as inferred from low TOC content. This facies was deposited during the glacial periods MIS 4, MIS 2 and during the late Holocene. Facies B is dominated by fine SS indicating weak bottom current and poor ventilation (cf. high TOC content of 1.2–1.6%), and correlates with the MIS 4/3 and MIS 2/1 transition periods. With an equal amount of clay and sand, fine SS and high content of TOC, facies C indicates reduced bottom current strength for intervals with sediment supply from proximal sources such as icebergs, sea ice or meltwater discharge. This facies was deposited during the last glacial maximum. Facies D represents mass-flow deposits on the northern Svalbard margin attributed to the SBIS advance at or near the shelf edge. Facies E sediments indicating moderate bottom current strength were deposited during MIS 5 and MIS 3, and during parts of MIS 2. This first late Quaternary proxy record of the WSC flow and sedimentation history from the northern Svalbard margin suggests that the oceanographic conditions and ice sheet processes have exerted first-order control on sediment properties.  相似文献   

2.
波弗特环流(Beaufort Gyre)是 决定北冰洋海冰运移方向和滞留时间的主要因素。依据沉积物的颜色旋回、Mn元素含量和有孔虫丰度,本文建立了阿尔法洋脊(Alpha Ridge)B85-D孔轨道尺度上的年龄框架,并深入分析了该孔晚第四纪以来冰筏碎屑(IRD>154 μm)含量、组分及其源区的变化特点。结果表明,350ka以来最显著的变化发生在末次冰期(MIS2~4期),期间沉积物中Ca元素和白云石含量都接近于零,大部分来自班克斯岛、维多利亚岛和麦肯齐地区的碳酸盐岩碎屑没有在阿尔法洋脊沉积;随着波弗特环流的消亡,搬运陆源碎屑的海冰很可能沿着北美海岸线直接进入了欧亚海盆。而在末次间冰期(MIS5期),波弗特环流却十分流畅,并将大量碳酸盐岩碎屑限制在美亚海盆内,导致阿尔法洋脊沉积物中Ca元素含量急剧升高,与之对应的白云石含量高达16.4%。通过类比可知,在MIS6期波弗特环流的状态可能与MIS2~4期相似,而在MIS8和MIS10这两大冰期,波弗特环流却类似于MIS5期。显然,波弗特环流的存在与否并不严格遵循“冰期-间冰期”旋回,这种变化很可能是风场强度和海冰浓度双重作用的结果。  相似文献   

3.
黄河河口段与海河河口段沉积物碳酸盐对比分析   总被引：1，自引：1，他引：1  
王艳君  金秉福 《海洋科学》2017,41(7):94-104
利用筛析-沉降法对黄河系及海河系沉积物进行了粒度特征分析,黄河系沉积物以极细砂-粗粉砂为主,分选性中等,粒度分布正偏,峰态曲线尖窄;海河系沉积物以细粉砂为主,分选性较差,粒度分布正偏,峰态曲线较平缓。测定黄河系及海河系沉积物碳酸盐的粒度百分含量及碳酸盐加权粒度百分含量,结果表明:黄河系沉积物碳酸盐粒度百分含量加权平均值为11.36%,细砂碳酸盐粒度百分含量较高(15.24%),随粒度越细波动式降低后逐步增加,并在黏土富集,达20.67%;海河系沉积物中碳酸盐粒度百分含量加权平均值为15.05%,比黄河系略高,呈两端高中间低不对称鞍形粒度分布。黄河系与海河系碳酸盐粒度百分含量受粒度控制,对全样碳酸盐贡献最大的粒度黄河系为粗粉砂,海河系为细粉砂。黄河系全岩碳酸盐平均粒度百分含量与马兰黄土相近,与黄渤海泥质区相当,表明黄河沉积物的主要来源是马兰黄土,黄河在沉积物搬运过程中对黄土碳酸盐没有明显改造,黄河沉积物黏土组分是黄渤海泥质区沉积物高碳酸盐的主要影响因素。  相似文献   

4.
《Journal of Sea Research》2010,63(4):276-285
A decrease in the areas covered by seagrasses within the Ria de Aveiro, Portugal, has been observed over the past five decades, resulting in a corresponding increase of the areas of uncovered sediment supporting the growth of sparse macroalgae populations only. Presently, several macroalgae (Ulva spp., Gracilaria sp.) and one seagrass species (Nanozostera noltii (Hornem.) Toml. & Posl.) comprise the submerged aquatic vegetation (SAV) adapted to this shallow, high-energy environment, characterised by fast tidal currents and turbid waters and in which large areas of the bed are exposed during low tide. This study shows that there is a strong inter-relation between the SAV and the surface sediment in intertidal areas. The sediment covered by N. noltii was finer (median grain size 95 µm) and had a high percentage of organic matter (mean value 7.6%), compared with the sediment colonised by macroalgae (median grain size 239 µm; mean organic content 3.2%). The concentrations of both total nitrogen and phosphorous were significantly greater (P < 0.001) in surface sediments covered by N. noltii. Thus, sediments within N. noltii appear to act as a large reservoir of N and P by accumulating greater concentrations of fine sediment particles (silt and clay) and organic matter when compared with the coarser sediment covered with macroalgae only. Hence, the reduction in the area covered by seagrasses will likely result in a gradual loss of nutrients and fine sediment from the Ria de Aveiro channels.  相似文献   

5.
Characterization of the sediment composition of tidal flats and monitoring of their spatiotemporal changes has become an important part of the sustainable management of coastal environments. To accurately classify sediments through remote sensing, a comprehensive understanding of sediment reflectance spectra is indispensable. The present laboratory-based study explores the performance of the high spatial resolution (10?×?10 m) Advanced Land Observing Satellite (ALOS) launched in 2006. Relationships between reflectance spectra (bands 1 to 4) and four typical mass physical properties were investigated under wet and dry experimental conditions for intertidal sediments sampled near the Ba Lat Estuary in northern Vietnam. Reflectance in the near-infrared region corresponding to ALOS band 4 (0.76–0.89 μm) was found (1) to have a strong negative correlation with sand content (dry wt%) under both wet and dry conditions (linear correlation coefficient r?=?–0.7859 and –0.8094, respectively), (2) to increase with decreasing relative water content (%) in a given sediment type (r?=?–0.7748 to –0.9367 for mud, sandy mud, muddy sand, and sand), (3) to have a positive correlation with organic matter content (r?=?0.7610 and 0.6460 under wet and dry conditions for contents >0.20 dry wt%), and (4) to be insignificantly correlated with mineral composition assessed in terms of contents (wt%) of quartz, clay minerals, and mica group minerals. Positive relationships between reflectance and water content for the pooled data of all sediment types (r?=?0.6395) or organic matter content contrast with previous findings, and can be attributed to close interrelationships between these properties and the predominance of sand content as controlling factor of reflectance. This study clarifies that ALOS band 4 provides the most useful imagery for intertidal monitoring because its reflectance, as simulated using the laboratory data, shows the strongest correlation with sand content. In a next step, these experimental findings should be verified by identifying the reflectance relationships at satellite image scales, and also considering the effects of other tidal flat features on reflectance, such as microtopography and biological surface characteristics.  相似文献   

6.
The eelgrass Zostera marina is a key structural and functional species across the European coastline. The separate and interactive effects of eelgrass canopy removal and sediment addition on the sediment characteristics and the structure of benthic communities were studied in a factorial field experiment in the Northern Baltic Sea in July–August 2006. The removal of eelgrass canopy temporarily increased the sediment oxygen consumption, reduced the content of fine particles (<100 μm) and organic matter in the sediment, and increased the share of sand fraction (250–500 μm). Sediment addition increased the content of fine particles (<100 μm) and reduced the share of sand fraction (250–1000 μm). The effects were strongest in the presence of eelgrass canopy. Benthic invertebrates and macroalgae were affected by eelgrass canopy removal but not by sediment addition. The removal of eelgrass canopy significantly decreased benthic species richness and invertebrate and macroalgal densities. To conclude, our experiment demonstrates that Z. marina defines the patterns of benthic macroalgae and invertebrates but has moderate effects on sediment structure and metabolism in the Northern Baltic Sea.  相似文献   

7.
Periplatform surface sediments were studied for carbonate mineralogy in conjunction with analyses of the water column for carbonate chemistry on the eastern Northern Nicaragua Rise (NNR) in the Caribbean Sea. The results show a strong correspondence between variations and disappearance, with increasing water depth, of metastable carbonate minerals (fine aragonite and magnesian calcite) and their respective saturation levels in the overlying waters. Similar correspondence between variations in sediment proportions of fine aragonite and magnesian calcite and their respective saturation levels has previously been established in the Bahamas. There are, however, significant differences between the two areas. The sharp decrease in aragonite content and the measured aragonite saturation level occur at 4000 m in the Bahamas, compared to 1800 m on the eastern NNR. In both areas, magnesian calcite minima correspond to the in situ PCO2 maxima in the water column. The magnesian calcite minimum, however, is at 950 m in the Bahamas and 750 m on the eastern NNR. Magnesian calcite disappears in the Bahamas at 3800 m and at 2000 m on the eastern NNR. These results demonstrate the importance of the influence of overlying water chemistry on the preservation of metastable carbonate minerals in off-bank periplatform sediments, and they clearly demonstrate the difference in terms of carbonate preservation between the poorly ventilated waters of the Caribbean Sea and the well-oxygenated waters of the adjacent Atlantic Ocean. They also open the possibility of obtaining paleoceanographic information on the depth of the CO2 maximum (O2 minimum) and its separation from the aragonite saturation depth in at least some areas.  相似文献   

8.
对CSH1岩心全样沉积物样品进行元素地球化学分析,揭示了过去88ka冲绳海槽北部沉积物成分、水动力条件及陆源碎屑物质源区风化历史。冲绳海槽北部碎屑沉积物母岩主要以长英质为主,在MIS 1期沉积物存在大量火山源物质。过去88ka,沉积物源区风化程度较弱,但是自冰消期以来有逐渐增强的趋势。沉积物Zr/Nb比值表明在MIS 1期和MIS 5.1期水动力较为强烈,这与黑潮增强的时间一致,可能是指示黑潮强度的一个指标。冲绳海槽北部陆坡沉积物陆源碎屑贡献在低海平面时期显著增加,而在MIS 1和MIS 5.1期生源贡献显著增加。冲绳海槽北部沉积物成分变化明显受到黑潮和入海径流的调节,实际上受海平面和东亚季风的制约。  相似文献   

9.
本文通过对阿蒙森海西北部陆隆AMS01岩心沉积物颜色、粒度及地球化学等多种指标分析，重建了该地区氧同位素9期(MIS9，大约距今34万年)以来冰盖与古生产力演变历史，结果表明:(1)岩心沉积物粒度与古生产力替代指标表现出明显的冰期–间冰期旋回变化特征；(2)MIS9、MIS7和MIS5等间冰期沉积速率较小，沉积物呈褐色，冰筏碎屑含量低，生源组分含量高，反映出该时期阿蒙森海地区气候温暖，冰盖发生了大规模退缩，冰盖–冰架–冰山等陆源冰对沉积物的影响减弱，海冰覆盖减弱，有利于浮游植物的生长和繁殖；(3)MIS8c、MIS8a、MIS6、MIS2等冰期沉积速率大，沉积物呈灰色，沉积物随之变粗，冰筏碎屑含量高，生源组分含量低，说明该时期冰盖大幅扩张，陆隆区成为近冰盖/冰架沉积环境，海冰和冰山密集，海洋生产力显著降低；(4)冰期、间冰期内，冰盖与古生产力也有不同程度的波动；特别是MIS8b期发育浅褐色间冰阶沉积，冰筏碎屑含量低，生产力水平与间冰期基本持平，说明阿蒙森海地区冰盖、海洋对气候变化的响应比东南极地区敏感。  相似文献   

10.
本文针对采自印度洋深海中最常见的两类生物成因沉积物——钙质软泥和硅质软泥，开展了全岩样和不同粒级组分中常微量元素、稀土元素和Y（REY）含量的系统分析，探讨了两类沉积物中REY的组成特征、物质来源和富集机制。研究表明，钙质软泥以富含CaO和Sr为主要特征，硅质软泥则富集SiO2、Al2O3、Fe2O3等。钙质软泥中∑REY平均含量为40.56×10-6，轻稀土元素（LREE）略有富集，REY有向细粒沉积物中富集的特征，PAAS标准化后全岩样和不同粒级组分均表现为Ce负异常、Eu和Y正异常；REY以自生来源为主，继承了海水的组成特征，同时也受到了热液流体物质和洋底玄武岩风化产物的影响。硅质软泥中∑REY的含量为248.54×10-6，LREE相对富集，REY在4φ以细的沉积物中富集；研究站位沉积物中∑REY含量处于边界品位附近，但在细粒级沉积物中重稀土元素（HREY）含量则达到了工业品位；该类沉积物细粒组分中REY主要来自陆源或火山碎屑组分中黏土矿物和铁锰氧化物吸附作用，粗粒组分中REY来源则主要与生物作用相关；硅质软泥中REY的富集与沉积物中磷灰石等矿物相关，部分不同来源的REY可能是在沉积之后的成岩过程中再次分配向磷灰石、钙十字沸石等矿物中富集。  相似文献   

11.
The aim of this study was to evaluate the erodibility of submarine coastal sediments for the purpose of modelling sediment dynamics in Mecklenburg Bay, south-western Baltic Sea. Erosion thresholds derived from experiments with a device microcosm on cores of fine sand (n=5, mean grain size=132 µm) and mud (n=5, medium silt size, mean=21 µm), collected at different times of the year, were compared to theoretical critical shear stress velocities based on grain-size measurements. For this purpose, a sedimentological map of natural surface sediments was constructed for the study area. Calculated values for critical shear stress velocities (u* cr-Hjulström ) are 1.2 cm s?1 for fine sand, and 3.75 cm s?1 for cohesive mud. At the mud station, erosion experiments showed an initial transport of the fluffy surface layer (u* cr-initial ) at a mean critical shear stress velocity of 0.39 cm s?1. Initial rolling transport at the fine sand station for single sand grains was recorded at values of 0.5 cm s?1. At higher shear stress velocities, the two sediment types showed diverging erosion behaviour. Measurable erosion (ε>5.0×10?6 kg m?2 s?1) of fine sand starts at a mean critical shear stress velocity (u* cr-erosion ) of 1.15 cm s?1 whereas fluffy surface material on mud cores was eroded at mean u* cr-erosion of 0.62 cm s?1. This indicates that measured erosion thresholds at the fine sand site fit well to calculated critical shear stress velocities whereas calculated erosion thresholds for cohesive mud are roughly 6 times higher than measured values. As erosion behaviour at the mud station was dominated by fluffy surface material, the comparability of measured and calculated threshold values may be reduced. The underlying silt-sized sediment itself was stable due to cohesive effects. This behaviour has to be taken into consideration by using sediment types instead of mean grain sizes for mapping and modelling sediment dynamics. A comparison of the near-bottom hydrodynamic conditions in the study area and experimentally derived critical shear stress velocities suggests that particle transport is controlled by storm events whereas under calm conditions shear stress velocities do not exceed the critical values.  相似文献   

12.
Substantial amounts of adsorbed methane were detected in authigenic carbonate concretions recovered from sedimentary layers from depths between 245 and 1,108 m below seafloor during Ocean Drilling Program Leg 186 to ODP sites 1150 and 1151 on the deep-sea terrace of the Japan Trench. Methane contents were almost two orders of magnitude higher in the concretions (291–4,528 nmol/g wet wt) than in the surrounding bulk sediments (5–93 nmol/g wet wt), whereas methane/ethane ratios and stable carbon isotopic compositions were very similar. Carbonate content of surrounding bulk sediments (0.02–3.2 wet wt%) and methane content of the surrounding bulk sediments correlated positively. Extrapolation of the carbonate contents of bulk sediments suggests that 100 wt% carbonate would correspond to 1,886±732 nmol methane per g bulk sediment, which is similar to the average value observed in the carbonate concretions (1,321±1,067 nmol/g wet wt, n = 13). These data support the hypothesis that, in sediments, adsorbed hydrocarbon gases are strongly associated with authigenic carbonates.  相似文献   

13.
《Marine Geology》2001,172(3-4):265-285
Studies of latest Quaternary continental slope sediments at two localities on the east Australian margin have revealed markedly different responses to late Quaternary sea level fluctuations. Offshore of Noosa, in the sub-tropics, the sediment is predominantly a mixture of fine metastable carbonate, siliciclastic material, and pelagic carbonate. Important features of the stratigraphy include a siliciclastic-dominated facies deposited relatively slowly during the last glacial lowstand (sedimentation rate ≤8 cm/ka), and a calcareous facies, rich in metastable carbonate, deposited more rapidly during the late post-glacial transgression (sedimentation rates 15–24 cm/ka). Highstand and transgressive sedimentation rates are greater than lowstand rates by a factor of 2.5–6 due to increased shelf carbonate productivity after flooding of the mid-shelf. Off Sydney, in temperate latitudes, continental slope sediment is largely a mixture of fine siliciclastic material and pelagic carbonate. Mean sedimentation rates range from 2 to 5 cm/ka over the last four oxygen isotope stages, with mean glacial/interstadial rates higher than Holocene rates by a factor of ∼1.36. This largely reflects the transfer of siliciclastic mud from the shelf to the slope during sea level regression. In both localities, facies changes on the slope are not related to specific sea level states (e.g. lowstand facies, transgressive facies, etc.), but reflect instead the interaction of changing sea level with shelf morphology.  相似文献   

14.
The previous studies of the sedimentology and chronology of sediment core SYS-0701, which was recovered from the western South Huanghai Sea (Yellow Sea), have revealed the changes in the sea-level and sedimentary evolution during the late Quaternary in the region. The present study used mineralogical data from the section of the core deposited since Marine Isotope Stage (MIS) 3, to decipher the provenance of sediments of the paleo-delta deposited during MIS 3 and MIS 1. Based on the lithologic features and the variations with depth of the concentrations of carbonates and both heavy and light minerals in bulk samples, the upper part of Core SYS-0701 can be divided into three units designated DU1, DU4, and DU5, in accord with previously used terminology. Sub-units of units DU1 (DU1-1 and DU1-2) and DU4 (DU4-1 and DU4-2) have also been identified. DU1 was deposited during MIS 1, and DU4 and DU 5 were formed during MIS 3. All data pertaining to dominant heavy mineral assemblages, diagnostic minerals, ratios of diagnostic minerals, light mineral associations, textural maturities, and carbonate contents, indicate that the sediments of Core SYS-0701 are comparable with Huanghe River (Yellow River) sediments. Moreover, the mineralogy of the sediment evidenced its dependence on supply rates and hydrodynamic conditions. Weak hydrodynamics (DU5 and DU4-2) and/or low sediment supply (DU1-2) led to sediment containing less hornblende and epidote, with a large specific gravity and high content of flaky minerals, and vice versa in cases of strong hydrodynamics (DU4-1) and very large sediment supply (DU1-1).  相似文献   

15.
Grain size and water content in box-core sediments from the Clarion-Clipperton fracture zone (C-C zone) in the northeast equatorial Pacific were analyzed in detail to understand the downcore variations across a hiatus between Quaternary and Tertiary layers. Grain-size distributions in the topmost core sediments show two modes: a coarse mode (peaked at 50 μm) and a fine mode (at 2-25 μm). The coarse mode disappears gradually with depth accompanied by the dissolution of siliceous fossil tests, whereas the fine mode coarsens due to the formation of authigenic minerals. Water content increases abruptly across a color boundary between an upper pale brown layer and a lower dark brown layer that is the hiatus between Quaternary and Tertiary layers. Abundant smectites and microvoid molds, which are created by the prolonged fossil dissolution in the underlying sediment, are attributed for the abrupt downcore variation of water content. Overall variations in grain size and water content in the topmost core sediments in the western C-C zone are possibly constrained by the dissolution of biogenic siliceous fossils. Variations in geotechnical properties related to these changes must be considered in the design of nodule collectors.  相似文献   

16.
Sediment grain size, and specifically changes in the percent mud content (i.e. the fraction <63?µm) over time is often used as an indicator of estuarine environmental health. Using sediment samples from three distinct estuarine systems, we determined that different analytical methods (laser diffraction and wet sieving) gave significantly different results in terms of percent mud content. These differences are also ecologically meaningful when considering the influence of mud on estuarine macrofauna. We propose an approach to measuring sediment grain size termed Environmentally Available Sediment (EAS), which advocates for the measurement of the sediment that biota are directly exposed to. For the purposes of environmental monitoring, it is also essential to monitor sediment grain size in a repeatable way which is likely to be achieved using consistent (or no) pre-treatment and the use of a measurement technique that is unlikely to change over time, e.g. wet sieving.  相似文献   

17.
Large sediment deposits on the reef front around Oahu are a possible resource for replenishing eroded beaches. High-resolution subbottom profiles clearly depict the deposits in three study areas: Kailua Bay off the windward coast, Makua to Kahe Point off the leeward coast, and Camp Erdman to Waimea off the north coast. Most of the sediment is in water depths between 20 and 100?m, resting on submerged shelves created during lowstands of sea level. The mapped deposits have a volume of about 4?×?108?m3 in water depths less than 100?m, being thickest off the mouth of channels carved into the modern insular shelf, from which most of the sediment issues. Vibracore samples contain various amounts of sediment of similar size to the sand on Oahu beaches, with the most compatible prospects located off Makaha, Haleiwa, and Camp Erdman, and the least compatible ones located in Kailua Bay. Laboratory tests show a positive correlation of abrasion with Halimeda content: samples from Kailua Bay suffered high amounts of attrition, but others were comparable to tested beach samples. The common gray color of the offshore sediment, aesthetically undesirable for sand on popular tourist beaches, was diminished in the laboratory by soaking in heated hydrogen peroxide.  相似文献   

18.
Abundant evidences of higher sea levels from Jiangsu and Fujian coasts have proved a marine transgression event during 30–40 ka BP, suggesting that there was a stage with high sea level and a warm climate when ice sheets shrank in the Northern Hemisphere. The duration of 30–40 ka BP spanned a period in the late Marine Isotope Stage 3(MIS 3) and was in nature an interstadial epoch during the Last Glacial period of the Quaternary. Different from the glacial period with a cold climate, this marine transgression considered as a penultimate higher sea level during the Quaternary remains a puzzle that why the evidence is contrary to the Quaternary glacial theory. It is important to understand sea level rise for these areas sensitively responding to the global changes in the future. To recognize the key issues on sea level changes, the eustatic sea level(H_S) was defined as the glaciation-climateforced sea levels, and the relative sea level change(H_R) was defined as that a sea level record was preserved in sediment that experienced multiple secondary actions of land and sea effects. On the basis as defined above, we constructed multi-level models of climate-driven glacio-eustatic changes and land-sea systems. By integrating data sets from eight borehole cores and prescribing the boundary conditions, we simulated the changes of HS and HR in the East China Sea and southern Yellow Sea areas in the late MIS 3. The marine transgression strata from the borehole core data was identified at ca. 30 m below present sea level as a result of the collective influence of ice melting water, neotectonic subsidence, sediment compaction and terrestrial sediment filling since ca. 35 ka ago,whereas the simulated relative sea-levels turned out to be –26.3––29.9 m a.s.l. The small error involved in the simulation results of ±(2.5–4.5) m demonstrated the credibility of the results. Our results indicated that sea level change in the late MIS 3 was dominated by glacial effects, in which the eustatic sea-level was between –19.2––22.1m a.s.l. The study sheds light on the nature of sea-level changes along the east coast of China in the late MIS 3 and contributes to understanding the characteristics of marine transgression under the effects of multiple complex land-sea interactions.  相似文献   

19.
Multiproxy investigations have been performed on Core 08P23 collected from the Chukchi Plateau, the western Arctic Ocean, during the Third Chinese National Arctic Expedition. The core was dated back to Marine Isotope Stage(MIS) 3 by a combination of Accelerator Mass Spectrometric(AMS) carbon-14 dating and regional core correlation. A total of five prominent ice-rafted detritus(IRD) events were recognized in MIS 2 and MIS 3. The IRD sources in MIS 3 are originated from vast carbonate rock outcrops of the Canadian Arctic Archipelago and clastic quartz in MIS 2 may have a Eurasian origin. Most δ18O and δ13C values of Neogloboquadrina pachyderma(sinistral)(Nps) in Core 08P23 are lighter than the average values of surface sediments. The lighter δ18O and δ13C values of Nps in the two brown layers in MIS 1 and MIS 3 were resulted from meltwater events; and those in the gray layers in MIS 3 were caused by the enhanced sea ice formation. The δ18O values varied inversely with δ13C in MIS 2 indicate that the study area was covered by thick sea ice or ice sheet with low temperature and little meltwater, which prevented the biological productivity and sea-atmosphere exchange, as well as water mass ventilation. The covaried light values of δ18O and δ13C in MIS 1 and MIS 3 were resulted from meltwater and/or brine injection.  相似文献   

20.
Color measuring is characterized by high resolution, high efficiency, and low cost. The application becomes increasingly common for tracing sediment sources and climate variation. Borehole LZ908 in the south coastal plain of the Laizhou Bay in northeast China, was used, of which the top 54 m containing all marine facies was focused, to test the feasibility of colorimetry as a climate indicator using visible light reflectance spectra and L*a*b* measurement results. The results show a good correction between lightness and calcium carbonate content in marine-terrigenous deposits; therefore, these deposits can be used as a proxy to study climate changes. Factor-analysis on the first derivative values of the raw visible light reflectance spectra produced three principal factors corresponding to goethite, organic matter, and hematite. Down hole variations in the three factor scores, lightness, calcium carbonate content, and grain size were quite consistent. Moreover, high lightness and low factor scores in goethite, hematite, and organics indicated glacial regression deposits, while low lightness and high factor scores in goethite, hematite, and organics indicated interglacial transgression deposits.  相似文献   

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