东海DC-2孔岩芯粘土矿物组合及其分布特征

DC-2孔柱状岩芯取样深度为48.6m,粘土矿物组分以伊利石为主,其次为绿泥石、高岭石和蒙脱石。岩芯共分6个粘土矿物组合层,参考Mn/Fe计算结果,0—29.46m为浅海相;33.42—33.46m为淡水相;38.44—38.46m为浅海相;44.0—48.06m为淡水相沉积。综合研究表明该沉积段出现二次海进和一次海退。     

东海DC-2孔沉积物中有机质的特征

为查明东海DC-2孔岩芯中有机质含量的变化情况,对沉积物中有机碳和沥青总量进行了分析测定。在不同深度和不同层位共取了58个样品,由于样品量受到限制,分析沥青的样品重量由250—700克不等。 沉积物的粒度在整个岩芯中变化比较明显,由下而上可分为五个大层。 1.粉砂层(91.5—75.5米):粉砂粒级含     

尼罗河三角洲全新世海平面变动及其对环境的影响——与长江三角洲的对比

利用泥炭(33个)和潟湖(65个)14C测年数据重建了尼罗河三角洲全新世海平面的变动过程,结果显示潟湖样品比泥炭更为有效地反映出海平面变动特征:距今7000a时海平面约位于现今-10m,距今5000a时约为-5m,距离2000a时已接近现代.海侵强度和范围受古地貌和区域沉降的影响呈现出东北部大、中部其次、西部最小.随着海平面上升速率减小,三角洲在约距今7000a时开始建造,并广泛发育潟湖、沙坝和平原河流沉积体系.此后,海平面趋于稳定,人类活动增强,导致海岸沉积环境大片萎缩、消亡.同样利用泥炭(45个)测年数据重建了长江三角洲全新世海平面变动,结果与尼罗河的差异较大,可能是两地沉降差异所致.近代长江三角洲人类活动也是导致环境退化的主要原因.     

5000 aBP南部大洋南大西洋区南极表层水温急剧下降和浮冰扩张

我们根据南部大洋大西洋区南纬 53°活塞岩心分析结果重建南大西洋全新世南极表层水变化史。此岩心沉积速率较高 (全新世平均值为50 cm/ 1 0 3a) ,且位于亚南极的南大西洋 ,适用于古气候研究。钻位位于现代极地前缘带( PFZ)以南约 3°,冬季海冰边界以北约 2°。利用硅藻转换函数、硅藻内有机质的碳和氮同位素、粗粒沉积物 ( >1 50 μm～ 2 mm)中放射虫、有孔虫和浮冰碎屑相对丰度 ,对硅藻和有孔虫的氧同位素、二月表层海水和海冰盖层温度进行了测定 ,提供了 50 0 0 a BP表层水特征急剧变化的证据。1 0 0 0 0～ 550 0 a BP粗粒沉积物 ( >1…     

中国北方沿海两个沉积岩芯的古地磁研究

为编制中国北方沿海地区的古地磁年表,并为该区第四纪地层的划分与对比提供年代地层上的依据,我们选择了辛集孔(沦-13)和 H-70孔沉积岩芯进行了古地磁研究。根据磁倾角的正、反向变化,绘成了古地磁极性变化(柱状)年表。辛集孔位于华北平原东部仅有的两个出露死火山(即大山和小山)之间。该孔井深600米,下部未见到基岩,全部岩芯均为松散沉积,不含玄武岩及其他喷发岩层。全岩芯共制成136块标本进行了天然剩余磁性测量。     

上新世晚期以来黄河三角洲地区的沉积作用

通过450m长的五号桩岩芯的粒度分析、粘土矿物分析、碳酸盐分析和古地磁测年,揭示了现代黄河三角洲地区上新世晚期(约距今380×10~4a)以来,经历了一个长期稳定的沉积过程,沉积了一套以河流-湖泊相为主的粉砂质粘土、粘土质粉砂和细砂沉积;晚更新世以后,局部地区受渤海海侵影响,接受海相沉积。本区沉积动力作用很弱,沉积作用主要受区域构造运动和沉积古气侯的影响;晚更新世以前,在渤海地区的海侵期间,可能海水并未进入本区。     

西太平洋DSDP451孔晚中新世—第四纪的微体化石群及其古海洋学意义

西太平洋 DSDP45 1孔 (18°0 0 .88′N、143°16 .5 7′E,水深 2 0 6 0 m)的微体化石群和底栖有孔虫的同位素变化揭示了研究区中新世晚期以来的古海洋学演变及其重大事件。介形类化石群由晚中新世—早上新世 (超微化石 NN11- 13/ 14带 )的 Cytheropteron组合向早上新世—第四纪 (NN15～ 2 1带 )的 K rithe组合转变及 K rithe丰度的连续上升 ,很可能指示了西马里亚纳海岭自中新世以来下沉幅度达千米左右 ,水团由早期的中层水逐渐被深层水替代。底栖有孔虫 Cibicidoides wuellerstorfiδ1 8O在 NN11带晚期至 NN12带早期急剧变轻 ,反映了中新世末期碳偏移的全球事件。在 NN12带晚期至 NN16带早期 ,δ1 8O比其现代值轻 0 .5 5‰ ,推测早—中上新世暖期时底层水温要比现代高约 2℃左右 ;介形类的新生速率大于灭绝速率指示当时为有利底栖生物的时期。 δ1 8O最急剧的转变发生在 NN16和 NN17的过渡带 (距今约 2 .5 Ma) ,增值达 1.0‰ ,并在此后保持高值 ,标记北极冰盖的形成和北半球冰期气候的开始     

晚更新世末期的地磁短期反极性事件

晚更新世末期的地磁短期反极性事件,是由邦赫梅特(N.Bonhommet)和巴肯(J.Babkine)于法国拉斯钱普山(Puy de Laschamp)首先发现的。近十几年来,各国的某些古地磁研究者先后发表了数十篇论文对该事件的时代进行过讨论,但到目前为止,尚无较为一致的意见。根据已发表的年代资料,大体可将其归纳为两种意见:一是以莫尔尼(N.Morner)为代表,根据瑞典京城哥德堡公园的研究资料,认为该短期漂移时间应在距今13750—12350年范围内,并将其称为哥德堡事件(Gothenburg reversal);二是以威苏帕(K.L.Verosub)为代表,认为在距今21000—36000年间并不存在反向时期。而全球性的倒转时间应在距今35000—40000年间的某一时期。 根据我们对黄海,东海近岸带沉积岩芯的古地磁研究,认为晚更新世的地磁短期反极性事件,可能由两个事件组成。本文根据对沉积岩芯的系统测量、结合C~(14)测年和微     

南沙群岛海区NS97-13柱样沉积物磁化率各向异性研究

通过南海南沙群岛海区NS97-13柱样磁化率各向异性系统测试、统计计算和测年等分析,给出了沉积物的磁化率椭球几何形态,重建了研究海区的古水流方向、沉积物的沉积形式。研究结果表明:(1)压扁型椭球(E>1)的择优方向位于磁性线理-磁性叶理直线的上方,夹角β的范围为0°<β≤33.14°,拉长型椭球(E<1)的择优方向位于磁性线理-磁性叶理直线的下方,夹角α的范围为33.14°<α<56.86°,指示磁性颗粒沉降时受动力作用的大小及其受力方向不同;(2)由磁化率各向异性参数(磁性线理-各向异性度,磁性叶理-各向异性度)确定的沉积物有改造沉积、再沉积和稳定沉积三种形式,前两种形式掺杂在稳定沉积层中的不同部位,构成部分混合沉积;(3)最大磁化率和中间磁化率的轴向分布表征研究海区距今近62 ka以来古水流方向主要为南北和北东-南西向,总磁化率记录了Heinrich层中的冷事件H1—H6。     

南沙南部近30ka来的古海洋学记录

南海南部17962柱状样(7°11′N、112°5′E,柱长8 m,水深1 968 m)中近30 ka来的沉积物堆积速率计算结果显示,该孔冰期平均堆积速率为全新世的3倍多.其变化与冰期时海平面下降、地表径流所携陆源物质增多、全新世时海平面的回升以及陆源物质的提前卸载有关.浮游有孔虫氧同位素测定结果表明,该孔的浮游有孔虫的氧同位素冰期/全新世差值高于南海的平均值,更大于开放性大洋赤道西太平洋低纬度区的平均值.CaCO3变化则受陆源物质的"稀释作用"控制,而溶解作用对其影响并不太显著.     

东海北部外陆架EY02—1孔磁性地层研究

对长达70.20m的东海浅钻EY02-1进行了岩石磁学和古地磁分析,证明沉积物的载磁矿物主要为低矫顽力的磁铁矿,磁性地层揭示了发生于9.62~8.58m的磁极性事件,结合钻孔上部的AMS14C测年证明它为全新世初期的哥德堡磁极性漂移,线性外推的时间是距今12681~10206Ma,为全新世开始时地磁场是否发生过短期的磁极性漂移提供了新证据;与东海高分辨率的浅地层地震剖面以及典型钻孔(中法联合东海地震调查和DZQ4钻孔)对比还揭示,在中更新世地层中也出现过两次磁倾角变化。在钻孔中下部54.00~50.94m(2271—2151号样品)出现一段磁倾角变小甚至变成负值,但是由于该段沉积物以粗颗粒的砂为主并且负向样品并不连续,依据研究的标准不作为反磁极性事件。第二个比较连续的负向样品段出现在最底部70.20~64.31m。虽然研究区域内不乏揭示中更新统地层的地震剖面,但至今没有足够长的钻孔在时间上予以佐证。根据东海地震相对比和沉积物中海侵和海退旋回的不同特征以及布容期以来报道的反磁极性事件发生的时间来推测下部地层的时代归属。由于钻孔最底部的沉积主要是粗颗粒的粉砂质砂和细砂,同时钻孔也穿透了倒数第二冰期的杂乱地震相地层和其下的平行透明海相层,所以推测下部的倒转可能为发生在MIS8晚期的CR0反磁极性事件(距今265~255ka)。     

Deglaciation and meltwater events in hudson strait and the Eastern Canadian Arctic

Stable isotope measurements on molluses from raised marine deposits, and on foraminifera in a piston core, define a series of light isotope events. A major event is¹⁴C dated at ca. 10.3 ka and is correlated with a marked isotopic excursion in HU77-021-156. This event is followed by a dramatic rise in diatom and, slightly later, in benthic foraminiferal abundances. Molluses record another light event around 8 ka. Major fluctuations in both ¹⁸O and ¹³C around 10.3 ka suggests that the Hudson Strait ice stream may have responded to the Younger Dryas climatic oscillation.     

Growth dynamics of the deep-water Asian eelgrass, <Emphasis Type="Italic">Zostera asiatica</Emphasis>, in the eastern coastal waters of Korea

Among the seagrasses that occur along the coast of Korea, Zostera asiatica inhabits the deepest depth; however, to date, there is limited information on its ecology. This study presents the first quantitative data on the seasonal growth dynamics of Z. asiatica in Korea. We measured seasonal growth and morphological characteristics, as well as environmental factors, including underwater irradiance, water temperature, salinity and nutrient concentrations of the water column and sediment pore water, bimonthly from July 2012 to May 2015. Underwater irradiance showed clear seasonal trends, increasing in the spring and summer and decreasing in the fall and winter, ranging from 2.4 ± 0.2 mol photons m^-2 d^-1 in November 2012 to 12.8 ± 1.3 mol photons m^-2 d^-1 in July 2014. Water temperature also followed a strong seasonal trend similar to underwater irradiance, ranging from 9.8 ± 0.1°C in January 2013 to 20.5 ± 0.2°C in September 2013. Nutrient availability fluctuated substantially, but there was no evidence of distinct seasonal variations. Shoot density, biomass, leaf productivity, and morphological characteristics of Z. asiatica exhibited significant seasonal variations: maximum values of these variables occurred in summer, and the minima were recorded in winter. Total shoot density was highest (218.8 ± 18.8 shoots m^-2) in July 2012 and lowest (106.3 ± 6.3 shoots m^-2) in January 2013. Total biomass ranged from 182.6 ± 16.9 g dry weight (DW) m^-2 in January 2015 to 310.9 ± 6.4 g DW m^-2 in July 2014.Areal leaf production was highest (4.9 ± 0.0 g DW m^-2 d^-1) in July 2012 and lowest (1.4 ± 0.2 g DW m^-2 d^-1) in January 2013. The optimum water temperature for the growth of Z. asiatica was between 16-19°C. Growth of Z. asiatica was more strongly correlated with underwater irradiance than water temperature, suggesting that light is the most important factor determining seasonality of Z. asiatica at the study site.     

古海滩砾石层与海平面变动

在我国华北平原和长江三角洲等构造沉降区,已发现4—5个第四纪海相层和多条古海岸线。而在构造上升区沿海虽然找到了多级台地,但因缺乏可靠的海相沉积物,难以把它们定为海成阶地,山东半岛北部就是如此。因此,寻找古海相沉积就成为构造上升的沿海地区研究海平面变动的关键。到目前为止,已先后在辽东半岛、庙岛群岛等地区高于现今海平面的阶地上发现了海相层。近年     

赣北黄茅潭近代湖泊~(137)Cs蓄积特点、SCP计数和事件性沉积及其对~(210)Pb计年的矫正

对赣北黄茅潭近代湖泊沉积岩芯进行了~(137)Cs、~(210)Pb测试和SCP(球状碳粒)计数分析,阐述了~(137)Cs蓄积特征,结合SCP计数、粒度指标及降水记录厘定了一些事件性沉积层位。研究表明,1986年前后是沉积环境中~(137)Cs行为的转折点;在这之前,~(137)Cs以大气散落为主,其蓄积行为大致与降水存在正相关关系,在这之后,~(137)Cs以流域侵蚀为主,其蓄积行为与降水呈负相关关系。1953—1954年、1974—1975年、1998—1999年,流域降水丰沛,相应沉积层位~(137)Cs比活度低,这与流域强烈侵蚀稀释了进入湖泊的~(137)Cs有关。1963—1964年沉积层位~(137)Cs蓄积峰稳定而显著,与高通量的大气散落有关,也与当时降水量低,大雨、暴雨次数少,流域侵蚀强度低造成较低的沉积速率等密切相关,是可靠的定年时标。1986年存在同样的气候环境特点,其蓄积峰可能也是存在的,但需要进一步确认。基于~(210)Pb方法,利用多种计年模式计算了沉积岩芯的年代,发现与这些事件性沉积层位具有较大差异。研究认为,在长江中游这种降水高、流域侵蚀强度高的较为复杂的沉积环境中,~(210)Pb计年存在较大误差。复杂沉积环境中近代沉积的定年,有必要深度挖掘~(137)Cs环境行为,在全面阐述其蓄积特点的基础上,辅以SCP计数、粒度指标及降水等识别事件性沉积层位,矫正~(210)Pb计年,是精确建立近代沉积时标的必要方法。     

末次冰消期以来东海内陆架沉积物磁化率的环境意义

对末次冰消期以来东海内陆架沉积物磁化率的影响因素及其蕴含的古环境信息进行了探讨.对位于浙闽沿岸泥质沉积中心附近的EC2005孔沉积物磁化率、岩性、粒度、常量元素、矿物以及AMS<'14>C测年数据进行了综合分析,得出以下主要结论:EC2005孔沉积物磁化率的变化受多种因素的制约,不同层位的主要控制因素不同,60.20～...     

Seasonal and interannual variability in particle fluxes of carbon,nitrogen and silicon from time series of sediment traps at Ocean Station P, 1982–1993: relationship to changes in subarctic primary productivity

An extended time series of particle fluxes at 3800 m was recorded using automated sediment traps moored at Ocean Station Papa (OSP, 50°N, 145°W) in the northeast Pacific Ocean for more than a decade (1982–1993). Time-series observations at 200 and 1000 m, and short-term measurements using surface-tethered free-drifting sediment traps also were made intermittently. We present data for fluxes of total mass (dry weight), particulate organic carbon (POC), particulate organic nitrogen (PON), biogenic Si (BSi), and particulate inorganic carbon (PIC) in calcium carbonate. Mean monthly fluxes at 3800 m showed distinct seasonality with an annual minimum during winter months (December–March), and maximum during summer and fall (April–November). Fluxes of total mass, POC, PIC and BSi showed 4-, 10-, 7- and 5-fold increases between extreme months, respectively. Mean monthly fluxes of PIC often showed two plateaus, one in May–August dominated by <63 μm particles and one in October–November, which was mainly >63 μm particles. Dominant components of the mass flux throughout the year were CaCO₃ and opal in equal amounts. The mean annual fluxes at 3800 m were 32±9 g dry weight g m⁻² yr⁻¹, 1.1±0.5 g POC m⁻² yr⁻¹, 0.15±0.07 g PON m⁻² yr⁻¹, 5.9±2.0 g BSi m⁻² yr⁻¹ and 1.7±0.6 g PIC m⁻² yr⁻¹. These biogenic fluxes clearly decreased with depth, and increased during “warm” years (1983 and 1987) of the El Niño, Southern Oscillation cycle (ENSO). Enhancement of annual mass flux rates to 3800 m was 49% in 1983 and 36% in 1987 above the decadal average, and was especially rich in biogenic Si. Biological events allowed estimates of sinking rates of detritus that range from 175 to 300 m d⁻¹, and demonstrate that, during periods of high productivity, particles sink quickly to deep ocean with less loss of organic components. Average POC flux into the deep ocean approximated the “canonical” 1% of the surface primary production.     

Occurrence patterns of mesopelagic fish larvae in Sagami Bay, central Japan

The species composition, seasonal abundance, and vertical distribution of mesopelagic fish larvae are described based on discrete depth sampling from the surface down to 1000 m depth during four cruises at a fixed sampling station in Sagami Bay. The abundances of total mesopelagic fish larvae in April, July, September, and December were 65.7, 13.6, 118.9, and 17.2 individuals per 10 m² sea surface, respectively. Twenty species or types of mesopelagic fish larvae belonging to 10 families were collected. Diaphus garmani, Lipolagus ochotensis, Diogenichthys atlanticus, Sigmops gracile, and Maurolicus japonicus were the five most abundant larvae and accounted for 43.1, 14.5, 7.4, 6.3, and 5.9% of the total mesopelagic fish larvae, respectively. These five species showed clear seasonal changes in abundance, i.e. L. ochotensis, D. atlanticus, and S. gracile larvae mainly occurred during winter— spring; D. garmani and M. japonicus were collected during summer—autumn. No obvious diel vertical migration was found in these larvae. The larvae of D. garmani and M. japonicus were concentrated in the 25–50 and 50–100 m depth layers, respectively. The transforming stage of L. ochotensis, S. gracile, and D. atlanticus occurred at 400–1000 m depth, while their larvae (<8 mm standard length) occurred in the upper 100 m layer, indicating that metamorphosis of these species takes place in the 400–1000 m layer. Based on the occurrence of mesopelagic fish larvae and oceanographic processes in Sagami Bay, with the exception of D. garmani and M. japonicus, most larvae are considered to originate from the Kuroshio region where their main spawning grounds are formed.     

Physical model studies on wave transmission of a submerged inclined plate breakwater

This paper examines the results of physical model studies conducted in a monochromatic wave flume, to evaluate the wave transmission characteristics of a submerged plate breakwater consisting of a fixed plate of 0.50 m length and 0.003 m thickness. The model was oriented at varying inclinations and submergence. The influence of wave steepness, relative depth, relative submergence and angle of inclination on wave transmission was analysed. It was found that the horizontal plate is effective for short waves with steepness parameter higher than 5×10^?3 in relative depth grater than 0.21. The plate oriented at an angle of inclination of 60° is found to be effective for the entire ranges of wave parameters considered for the study and it reduces the wave height by about 40%.