台湾地区重力场特征及莫霍面反演

台湾地区空间重力异常幅值在-240~340mGal之间变化,布格重力异常幅值在-140~380mGal之间变化,重力异常及圈闭走向呈现北东、北北东向。将小波分析方法引入台湾地区的重力异常数据处理,经过分析比对,台湾地区布格重力异常小波分析三阶逼近结果代表莫霍面起伏形态,利用重力数据反演了深部界面莫霍面,研究区莫霍面深度为12~32km,莫霍面展布呈现北东走向,台湾岛区莫霍面深,在24~31km之间变化,由西北往东南为厚-薄-厚分布,台湾东部海区莫霍面深度浅,在12~17km之间变化,台湾岛属于陆壳结构,靠近菲律宾海的台湾岛外海地区,属于海洋性地壳结构。     

南极布兰斯菲尔德海峡区域重力场特征及异常分析

南极布兰斯菲尔德海峡及周边区域是南极大陆火山、地震等新构造活动最活跃的地区,与南设得兰海沟、南设得兰群岛一同构成南极大陆边缘现存唯一的"沟-弧-盆"构造体系。本文基于"雪龙"船第28、第30航次实测数据及两个航次的国际共享资料,利用均衡改正数据处理方法获得布兰斯菲尔德海峡的莫霍面深度及其分布规律,分析深部构造-断裂的区域分布及其重力异常特征等。布兰斯菲尔德海峡内的空间重力异常呈条带状分布,走向总体与地形相近,布格重力异常则由两侧向中间升高,大致在坡折处形成异常场值为100×10-5 m/s2的分界线,在中央次海盆和东部次海盆海山处形成两个异常高值圈闭,异常值最高为150×10-5 m/s2。莫霍面深度以弧后扩张中心为最低值,向南设得兰群岛和南极半岛两个方向递增,深度从12 km递增至陆坡位置的24 km。     

南极罗斯海R11柱样晚更新世晚期以来稀土元素地球化学特征

南极大陆边缘沉积物记录着南极及周缘地区海洋沉积与气候变化的重要信息。利用ICP—MS分析技术对取自南极罗斯海的R11柱状样沉积物进行了稀土元素地球化学特征分析。在R11柱样沉积物中,∑REE介于132.33~200.75 μg/g之间,在纵向上呈现波动式变化,体现出了沉积环境的不稳定性;REE含量变化与沉积物细粒组分(粉砂+黏土)和硅质生物碎屑不具有显著相关性;经球粒陨石标准化的REE配分特征表现为轻稀土富集、重稀土相对均一和Eu明显负异常的右倾型,与上陆壳(UCC)和澳大利亚后太古代页岩(PAAS)的配分模式较为接近,揭示R11柱样沉积物来源自晚更新世晚期以来相对稳定,物源区具有大陆性质。综合REE配分模式、富集因子和典型参数等特征分析表明,R11柱样沉积物主要来自于周缘的维多利亚地、横断山脉和玛丽伯德地古老沉积岩石或地层提供的长英质碎屑,新生代火山岩物源贡献相对较低。     

南极普里兹湾外海沉降颗粒物通量、组成变化及其与罗斯海对比研究

在南极普里兹湾外开阔海域布放时间系列沉积物捕获器,研究沉降颗粒物中生源组分(生物硅、有机质、碳酸钙)通量、组成、来源及元素的摩尔比值的生物地球化学意义,结果表明Ⅲ-1+站在1000m处颗粒物总通量的变化为13.00~334.59mg/(d·m2),颗粒物中以生物硅为主,占总通量的80%以上;各组分通量呈现明显的季节性变化.结合罗斯海沉降颗粒物通量和元素的摩尔比值的对比研究表明,研究海域1000m深的沉降颗粒物中生物硅与有机碳元素摩尔比值、无机碳与有机碳的元素摩尔比值较高,表明研究海域生物硅与有机碳生物地球化学循环过程是非耦合的,生物活动有效地将CO₂由表层水中移出.     

西太平洋卫星测高重力场与地球动力学特征

通过多卫星测高数据的综合处理，获得西太平洋卫星测高重力场，进行不同尺度、深度构造动力信息的分离，探讨诸边缘海盆的地球动力学问题。测高大地水准面反映了研究区板块相互作用的特点，其高频成分可以刻画各海盆的构造特征。测高空间重力异常也可刻画陆架构造及盆地分布，由其推算出的海底地形含有大量的海底构造信息。各边缘海盆的莫霍面埋深具有往南变浅的趋势，与菲律宾海各海盆的莫同埋深大致相当，说明岛弧两侧的构造力强度基本相似。大尺度地幔流应力场总体上反映了欧亚板块向东南蠕散和太平洋板块向北西扩张的特点；日本海北侧和南海巽他陆架的中尺度上地幔对流与地幔柱之间有着密切关系，西北菲律宾海的上地幔对流强化了日本－琉球－台湾－菲律宾岛弧的活动强度；上尺度地幔流主要限于软流圈层内部，在各海盆分散，而在冲绳 海槽和马里亚纳海槽则会聚，可与均衡重力异常比。还讨论了大、中、小地幔流体系的特点及相互之间的关系，籍以阐明海盆及槽演化的地球动力学过程。     

南海北部海陆过渡带地壳平均速度及莫霍面深度分析

南海北部海陆过渡带是一条深地震探测的空白带,其地壳结构研究不仪可以揭示华南沿海地区地震活动规律和构造活动特征,而且可以将以往在海上和陆上使用深地震探测所获得的地壳结构模型进行有效的衔接.鉴于南海北部海陆过渡带地壳结构的重要性,2004年我们在香港外海域进行了一次海陆地震联测实验.本文以此次实验中广东和香港地区固定地震台网以及担杆岛流动台所获得的数据为基础,对各台站接收到的Pg和PmP震相进行了近似横向均一的二维结构模拟,获得了各台站对应的地壳平均速度和PmP反射点处的莫霍面深度值.其结果显示研究区地壳平均速度普遍为6.2km·s-1左右,比全球地壳平均速度6.45km·s-1要低,这可能与普遍发育于华南沿海地带的中地壳低速层有关.研究区东边的SHW台所获得的地壳平均速度为6.7km·s-1左右,要明显高于全球地壳平均速度,它可能是由于局部异常结构所造成的,其与地幔岩浆的侵入作用可能存在一定联系.研究区莫霍面深度在26-35km左右,变化趋势较为明显,从北西向南东方向逐渐变浅,属于地壳减薄型结构,推测其可能与南海北部边缘的形成演化有密切联系.研究表明南海北部海陆过渡带是一个明显的转换地带,它的深部地壳结构特征应该与南海的扩张演化有密切联系,这些认识推进了华南地区和南海北部陆缘地壳结构和构造属性的深入研究.     

太平洋卫星测高重力场与地球动力学特征

通过多卫星测高数据的综合处理，获得西太平洋卫星测高重力场，进行不同尺度、深度构造动力信息的分离，探讨诸边缘海盆的地球动力学问题。测高大地水准面反映了研究区板块相互作用的特点，其高频成分可以刻画各海盆的构造特征。测高空间重力异常也可刻画陆架构造及盆地分布，由其推算出的海底地形含有大量的海底构造信息。各边缘海盆的莫霍面埋深具有往南变浅的趋势，与菲律宾海各海盆的莫霍面埋深大致相当，说明岛弧两侧的构造动力强度基本相似。大尺度地幔流应力场总体上反映了欧亚板块向东南蠕散和太平洋板块向北西扩张的特点；日本海北侧和南海巽他陆架的中尺度上地幔对流与地幔柱之间有着密切关系，西菲律宾海的上地幔对流强化了日本-琉球-台湾-菲律宾岛弧的活动强度；小尺度地幔流主要限于软流圈层内部，在各海盆分散，而在冲绳海槽和马里亚纳海槽则会聚，可与均衡重力异常类比。还讨论了大、中、小地幔流体系的特点及相互之间的关系，籍以阐明海盆及海槽演化的地球动力学过程。     

南极罗斯海柱样沉积物中有机碳和氮元素地球化学特征及其来源

南极周边海域沉积物中的有机碳和氮元素地球化学特征对于深入研究全球碳循环和海洋生态环境演变具有重要意义。本文对取自南极罗斯海的RBA08C柱状样沉积物进行了有机碳和氮元素地球化学特征分析。结果表明：RBA08C柱样中TOC含量在顶部0~12cm呈现随柱深增加而降低的趋势, 自12cm以深含量总体相对稳定; TN总体具有与TOC相同的变化趋势, 两者含量变化呈现较强正相关性, 说明可能具有相同来源; 沉积物TOC/TN比值和δ13C值揭示RBA08C柱样有机质主要为海洋生源沉积, 其含量变化应主要受控于上层水体生产力、沉积速率和氧化还原环境等因素的共同作用; RBA08C柱样的TOC埋藏率约为50%, 与位于普里兹湾埃默里冰架边缘的IS-4站柱样相同, 加之较为相近的TOC和TN含量及变化趋势, 表明两者可能具有相近的沉积速率, 其所在的海区是南极海域较重要的碳循环和碳储区。     

南海中北部莫霍面及深部构造

本文用重力资料反演计算了测区莫霍面埋深,试分析了影响莫霍面埋深及其展布形态的深部因素,并以莫霍面等埋深图为依据,结合重磁水深图探讨了南海地壳结构及深部构造,发现与相邻边缘海和大洋相比,南海具有莫霍面埋深浅,布格重力异常值低的特点,究其原因可能与南海复杂的构造活动和低密度地幔的存在有关。     

东海莫霍面起伏与地壳减薄特征初步分析

收集、整理大量由地震剖面提供的沉积层厚度资料,得到东海沉积层等厚图。对完全布格重力异常进行沉积层重力效应改正后,得到剩余重力异常,利用地震资料揭示的莫霍面深度值来约束界面反演得到东海莫霍面埋深。结果表明,东海陆架盆地莫霍面深度在25～28 km之间平缓变化,地壳厚度为14～26 km,西厚东薄;冲绳海槽盆地莫霍面深度为16～26 km,地壳厚度为12～22 km,北厚南薄。东海陆架盆地东部与冲绳海槽盆地南部地壳减薄明显,拉张因子分别达到2.6和3。初步分析认为冲绳海槽地壳以过渡壳为主,并未形成洋壳。     

南极罗斯海表层沉积物GDGTs含量 分布及其环境意义

通过分析罗斯海15个表层沉积物中甘油双烷基甘油四醚(Glycerol Dialkyl Glycerol Tetraethers,GDGTs)的含量与分布,探讨了各种GDGTs来源及TEX₈₆指标的环境意义。结果表明:表层沉积物中GDGTs总含量为93.67~2 663.37 ng/g,其中类异戊二烯GDGTs(IsoGDGTs)占90.33%~98.56%,远高于支链GDGTs(BrGDGTs)。类异戊二烯GDGTs与支链GDGTs具有显著的耦合关系(R²=0.88,p<0.01)。沉积物中的IsoGDGTs主要来源于海洋奇古菌,BrGDGTs主要由海洋水体和沉积物中原位细菌所产生。应用TEX^L₈₆公式估算研究区SST,与WOA夏季表层温度呈现较好的线性关系,表明TEX^L₈₆指标在罗斯海具有适用性,可作为重建古海洋温度的替代指标。     

利用脂肪酸标记法对南极罗斯海桡足类优势物种的食性研究

脂肪酸标记法是浮游动物食性研究的一种重要方法.将提取的脂质区分为中性脂和极性脂,可以进一步查明不同脂质在浮游动物食性研究中的作用.本研究通过分析不同脂质的脂肪酸构成,对2013年1月中国第29次南极考察期间在罗斯海采集的5种优势种桡足类的食性进行了研究.结果显示:5种桡足类的极性脂脂肪酸具有相似的组成,无法给出桡足类食...     

Thermohaline variability and Antarctic bottom water formation at the Ross Sea shelf break

We use hydrological and current meter data collected in the Ross Sea, Antarctica between 1995 and 2006 to describe the spatial and temporal variability of water masses involved in the production of Antarctic Bottom Water (AABW). Data were collected in two regions of known outflows of dense shelf water in this region; the Drygalski Trough (DT) and the Glomar-Challenger Trough (GCT). Dense shelf water just inshore of the shelf break is dominated by High Salinity Shelf Water (HSSW) in the DT and Ice Shelf Water (ISW) in the GCT. The HSSW in the northern DT freshened by ∼0.06 in 11 y, while the ISW in the northern GCT freshened by ∼0.04 in 8 y and warmed by ∼0.04 °C in 11 y, dominated by a rapid warming during austral summer 2001/02. The Antarctic Slope Front separating the warm Circumpolar Deep Water (CDW) from the shelf waters is more stable near GCT than near DT, with CDW and mixing products being found on the outer DT shelf but not on the outer GCT shelf. The different source waters and mixing processes at the two sites lead to production of AABW with different thermohaline characteristics in the central and western Ross Sea. Multi-year time series of hydrography and currents at long-term moorings within 100 km of the shelf break in both troughs confirm the interannual signals in the dense shelf water and reveal the seasonal cycle of water mass properties. Near the DT the HSSW salinities experienced maxima in March/April and minima in September/October. The ISW in the GCT is warmest in March/April and coolest between August and October. Mooring data also demonstrate significant high-frequency variability associated with tides and other processes. Wavelet analysis of near-bottom moored sensors sampling the dense water cascade over the continental slope west of the GCT shows intermittent energetic pulses of cold, dense water with periods from ∼32 h to ∼5 days.     

南极罗斯海氧化还原敏感元素沉积地球化学特征及其古海洋意义

大洋深部氧化还原环境与深部水体流通状况以及表层水体生产力密切相关。表层生产力与深部流通性变化影响着有机碳-呼吸CO2的转化及其在海洋-大气中的转移,最终与大气CO2分压(pCO2)变化密切相关。故探明大洋深部氧化还原环境的变化对于解决大气pCO2冰期旋回机制具有重要意义。本次研究以中国第31和32次南极科考获得的南极罗斯海柱状岩心ANT31-R23及表层样为研究材料。通过元素钙、钛,以及氧化还原敏感元素(RSE)锰、钼、镍、钴、镉的测试分析,以表层样中RSE与Ti的比值作为判断ANT31-R23孔中相应RSE富集程度的背景值。结果显示,Mn在沉积期均表现出富集,表明罗斯海深部在该孔沉积期为氧化环境。根据Mn在不同层位出现的富集峰识别出4次强氧化脉冲事件,可能由南大洋底层水流通性增强和/或生产力降低导致。4次氧化脉冲事件层位中Mo、Ni、Co的明显富集,是由于锰(氢)氧化物对其捕获或吸附所致。此外,推测分析认为罗斯海对冰期大气pCO2降低似乎没有明显贡献,但很可能对冰消期大气pCO2迅速升高起重要作用。然而这些有关南极罗斯海深部氧化还原环境与大气pCO2变化之间关联的推测,有待后续该孔精确年代模式的构建,方可进一步验证。     

Biological components of Ross Sea short-term particle fluxes in the austral summer of 1995–1996

The Ross Sea, a region of high seasonal production in the Southern Ocean, is characterized by blooms of the haptophyte Phaeocystis antarctica and of diatoms. The different morphology, structural composition and consumption of these two phytoplankton by grazing zooplankton may result in different carbon cycling dynamics and carbon flux from the euphotic zone. We sampled short-term (2 days) particle flux at 5 sites from 177.6°W to 165°E along a transect at 76.5°S with traps placed below the euphotic zone at 200 m during December 1995–January 1996. We estimated carbon flux of as many eucaryotic organisms and fecal pellets as possible using microscopy for counts and measurements and applying volume:carbon conversions from the literature. Eucaryotic organisms contributed about 20–40% of the total organic carbon flux in both the central Ross Sea polynya and in the western polynya, and groups of organisms differed in contribution to the carbon flux at the different sites. Algal carbon flux ranged from 4.5 to 21.1 mg C m⁻² day⁻¹ and consisted primarily of P. antarctica (cell plus mucus) and diatom carbon at all sites. Different diatom species dominated the diatom flux at different sites. Carbon fluxes of small pennate diatoms may have been enhanced by scavenging, by sinking senescent P. antarctica colonies. Heterotrophic carbon flux ranged from 9.2 to 37.6 mg C m⁻² day⁻¹ and was dominated by athecate heterotrophic dinoflagellate carbon in general and by carbon flux of a particular large athecate dinoflagellate at two sites. Fecal pellet carbon flux ranged from 4.6 to 54.5 mg C m⁻² day⁻¹ and was dominated by carbon from ovoid/angular pellets at most sites. Analysis of fecal pellet contents suggested that large protozoans identified by light microscopy contributed to ovoid/angular fecal pellet fluxes. Carbon flux as a percentage of daily primary production was lowest at sites where P. antarctica predominated in the water column and was highest at sites where fecal pellet flux was highest. This indicates the importance of grazers in carbon export.     

Microalgal Communities of the Sea Ice, Ice-Covered and Ice-Free Waters of Wood Bay (Ross Sea, Antarctica) During the Austral Summer 1993 – 94

Abstract. During the austral summer 1993 – 94, microalgal density and biomass were investigated in the sea ice, in the underlying water column, in the melt water and during the formation of the sea ice. Of the 96 taxa identified, 59 were diatoms and 32 were dinoflagellates. Among the remaining five species, Pseudopleurochloris antarctica  was very abundant both in the sea ice and in the ice-free waters. Cell densities and biomass of microalgae were higher in the bottom of the sea ice and during the formation of the ice than in the seawater, and diatoms were the dominant group at higher microalgal biomass. Among these, Entomoneis kufferathii , Chaetoceros dichaeta and Fragilariopsis species were the most common taxa.     

Interannual variability in vertical export in the Ross Sea: Magnitude, composition, and environmental correlates

The vertical flux of particulate matter from the surface of the Ross Sea, Antarctica, has been suggested as being large, with substantial seasonal and spatial variations. We conducted a study in which vertical flux was quantified using sediment traps deployed at 200 m and compared to estimates calculated from one-dimensional budgets of nutrients (nitrogen and silicon). Estimates of flux were collected at two locations in the southern Ross Sea from late December to early February during four years: 2001-2002, 2003-2004, 2004-2005, and 2005-2006. Phytoplankton biomass and vertical flux varied substantially seasonally and spatially between the two sites, and among years. The greatest flux was observed in 2001-2002, with a short-term maximum organic carbon flux of 3.13 mmol m⁻² d⁻¹, and the summer mean organic carbon flux equal to 0.93 mmol m⁻² d⁻¹. In contrast, the mean carbon flux at the same site in 2003-2004 was over an order of magnitude less, averaging 0.19 mmol m⁻² d⁻¹, despite the fact that productivity in that year was substantially greater. In 2005-206 the contribution of fecal pellets to flux was smallest among all years, and the pellet contribution ranged from <1 to more than 50% of organic flux. As the moorings also had surface layer fluorometers, the relationship between surface biomass and sediment trap flux was compared. Temporal lags between surface fluorescence and flux at 200 m maxima in 2003-2004 and 2004-2005 ranged from two to six days; however, in 2005-2006 the temporal offset between biomass and flux was much longer, ranging from 11 to 27 days, suggesting that fecal pellet production appeared to increase the coupling between flux and surface production. Estimates of export from the upper 200 m based on one-dimensional nutrient budgets were greater than those recorded by the sediment traps. Nutrient budgets also indicated that siliceous production averaged ca. 40% of the total annual production. The variations observed in the flux of biogenic matter to depth in the Ross Sea are large, appear to reflect different forcing among years, and at present are not adequately understood. However, such variability needs to be both understood and represented in biogeochemical models to accurately assess and predict the effects of climate change on biogeochemical cycles.