Sedimentary facies and paleoenvironmental interpretation of a Holocene marsh in the Gironde Estuary in France

1Introduction Since the last glacial maximum, the Holocenehas been marked by a rapid rise in sea level. After6 000 a BP, the present-day level was reached andthe rate of sea-level rise (SLR) decreased rapidly(Morzadec -Kerfourn, 1974; Kidson, 1986 ).These…     

LEADAT: a MATLAB-based program for lead-210 data analysis of sediment cores

1Introduction Tracking the history of man s impact on the en-vironment, it is clear that in many places the periodof greatest impact and most dramatic transformationlies within the last 150 a (Oldfield and Appleby,1984). Many aspects of this impact can be…     

Spatial and temporal variations of sedimented organic matter in Xiaohai Lagoon, Hainan Island

The characteristics of grain-size,total organic carbon(TOC) and total nitrogen(TN) contents,TOC/TN ratios,stable carbon isotope(δ13C) and 210 Pb dating were measured in six sediment cores from the Xiaohai Lagoon.The results show distinct spatial and temporal variations in sedimentation patterns.The sediments are dominated by clayey silt,sandy silt and by silty sand in the southern,middle lagoon and the northern lagoon,respectively.TOC and TN contents decline from south to north.Sedimentation rates,determined by 210 Pb dating,tend to decrease from south to middle.However,the determination of sedimentation rate in the north is difficult.These spatial variations are related to the variations in sediment sources and hydrodynamic conditions in the Xiaohai Lagoon.The variations of organic matter signatures can be divided into two stages in the cores from the southern and middle lagoon.Before 1988,the organic matter signatures are relatively stable.The contribution of terrestrial organic carbon sources varies between 60% and 85%.After 1988,the organic matter signatures demonstrate significant variations.TOC and TN contents increase rapidly,TOC/TN ratios decrease,δ13C values shift to higher and the contribution of terrestrial organic carbon sources decreases to 40%-50%.The contributions of phytoplankton organic matter have increased in the sediment since 1988.Increasing aquaculture activities have had a significant impact on organic matter signatures since 1988.The sedimentation rates have increased rapidly in the southern and middle lagoon since 1988 due to the anthropogenic activities which include aquaculture,mining and deforestation.These activities have caused eutrophication and increased siltation in the southern and middle lagoon.     

U、Th同位素在沉积物定年中的应用

全球气候变化已成为当前研究的热点问题,为预测未来气候的变化趋势,有必要对过去气候变化进行深入的研究,而这又基于可靠的年代学成果,故而年代尺度的高灵敏度、高精密度的测量成为当前迫切需要解决的课题之一。U-Th定年技术在14C年代测定(通常仅适用于39Ar/40Ar法或裂变径迹年代测定(一般用于>500 ka的火山堆积物)之间提供了一种年代测定的桥梁。U-Th定年技术在50~500 ka测年范围内是首选。主要介绍了国内外热电离质谱法(TIMS)U-Th定年技术、单接受器电感耦合等离子体质谱技术(SC ICP-MS)和多接受器电感耦合等离子体质谱法(MC ICP-MS)、U-Th定年法在沉积物领域中的研究概况,并对α谱仪、TIMS、SC ICP-MS、MC ICP-MS U-Th定年技术在测量时间、测量精度、样品需要量等方面进行比较。     

Modbus在生物采样电子监控系统中的应用

针对深海生物幼体采样的需要,提出一种基于Modbus协议的电子监控系统.首先介绍了Modbus通信协议,并重点研究了Modbus主从机的软件设计.设计实现了电子监控系统的软硬件部分.文章设计的监控系统将电子监控引入深海生物幼体采样,并实现了Modbus规约的网络化控制.系统大大提高了采样系统各部件的工作效率和稳定性,低功耗模式的设计也延长了采样系统的工作时间,一定程度上缓解了海底设备电力不足的困境.系统也适用于普通渔场生物拖网的控制.     

Characterization of tar-like material and producible oil in Misoa C2 and C3 reservoir sands of the Area 2 South (Ceuta Field,Venezuela)

Here we characterized asphaltic oil occurrences in the Misoa C2 and C3 reservoirs within Area 2 South of the Ceuta Field (Lake Maracaibo Basin, NW Venezuela). To perform the geochemical and petrological characterization of the C2 and C3 sub-units, which cover an interval in which tar-like material was detected, we analyzed core (18) and cutting (123) samples using the Rock-Eval 6 technique in reservoir mode. Samples were studied under fluorescence light and scanning electron microscopy (SEM), showing the presence of two charges of oils and the relationships within silica cements and clay minerals. To evaluate vertical inter-reservoir communication and lateral intra-reservoir continuity, we also studied 12 oil samples from wells in Area 2 South. Biomarkers and isotopic signatures were examined using gas chromatography-mass spectrometry (GC-MS) and isotope ratio mass spectrometry (IRMS). The results suggest that oil and core extracts belongs to a single family derived from two pulses of hydrocarbon generation from the La Luna source rock, which was deposited in a marine reducing environment. The oil samples are a mixture of a paleobiodegraded oil charge and a later fresh, more mature oil recharge. The geochemical analyses also evidence that the formation of heavy oil tar zones can be related to biodegradation and in-reservoir oil mixing, though other formation mechanisms for the tar are also feasible. Finally, the GC fingerprints of the oils are indicative of lateral reservoir continuities across the F-1 and F-2 faults and vertical communication between the Misoa C2 and C3 sub-units in Area 2 South, suggesting that tar occurrences do not act as permeability barriers within the two reservoirs studied.     

基于多源数据的山东省围填海造地特点及发展趋势研究

文章基于文献资料分析、官方数据汇总、国产高分辨率资源卫星遥感影像信息提取以及发展趋势研判等方法,对改革开放以来山东省全海域范围内围填海造地的历史发展、现状特征、发展趋势及其对生态环境的影响进行了分析和总结,并提出相关的政策建议。研究表明:改革开放以来,山东省围填海造地累计已超过4.58万hm~2。21世纪以来围填海造地进入快速增长时期,尤其是2010年以来,全省围填海造地又掀起了一次新的热潮,其面积和速度都远远超过了历史水平。鉴于围填海造地对环境和生态的巨大影响,文章提出了加强管理、严格环境影响评价、引入生态环境补偿机制以及建立分级填海评估制度和年度监测机制等建议。     

西北冰洋表-底层碳动力学耦合作用的同位素(13C,234Th)指示

The coupling of upper ocean-benthic carbon dynamics in the ice-free western Arctic Ocean(the Chukchi Sea and the Canada Basin) was evaluated during the late July–early September 2003 using natural stable(13C) and radioactive(238U-234Th) isotope tracers. POC export flux estimated from 234Th/238 U disequilibria and dissolved CO2 concentration([CO2(aq)]) pointed out that the strengthened biological pump in the Chukchi Shelf have significantly lowered [CO2(aq)] and altered the magnitude of isotopic(12C/13C) fractionation during carbon fixation in the surface ocean. Further, d13 C signatures of surface sediments(d13Csed) are positively correlated to those of weighted d13 CPOC in upper ocean(d13Csed =13.64+1.56×d13CPOC, r2=0.73, p0.01), suggesting that the POC isotopic signals from upper ocean have been recorded in the sediments, partly due to the rapid export of particles as evidenced by low residence times of the highly particle-reactive 234 Th from the upper water column. It is suggested that there probably exists an upper ocean-benthic coupling of carbon dynamics, which likely assures the sedimentary d13 C record an indicator of paleo-CO2 in the western Arctic Ocean.     

对虾高位池精养和生态养殖模式下沉积物中碳、氮元素变化及对底栖细菌的影响

本文采用原位生态学研究方法分析两种较为典型的对虾养殖模式—高位池精养模式和生态养殖模式沉积物中碳、氮元素的变化和其对底栖细菌的影响.结果表明:(1)在两种养殖模式下沉积物中碳元素含量都是呈上升趋势,高位池精养模式中C∶N值呈下降趋势,而生态养殖模式中C∶N值则呈上升趋势.(2)底栖细菌的呼吸量及其生物量变化呈显著正相关.单位生物量的底栖细菌代谢力变化和沉积物中C∶N值有关.在高位池精养模式中,沉积物C∶N值较高(＞16.59),单位生物量底栖细菌代谢力保持恒定;在生态养殖模式中,沉积物C∶N值较低(＜15.58),单位生物量底栖细菌代谢力随C∶N值的上升而增加.     

Zircon U–Pb and pyrite Re–Os age constraints on pyrite mineralization in the Yinjiagou deposit,China

We report new zircon U–Pb and pyrite Re–Os geochronological studies of the Yinjiagou poly-metallic deposit, sited along the southern margin of the North China Craton (SMNCC). In this deposit, pyrite, the most important economic mineral, is intergrown/associated with Mo, Cu, Au, Pb, Zn, and Ag. Prior to our new work, the age of chalcopyrite–pyrite mineralization was known only from its spatial relationship with molybdenite mineralization and with intrusions of known ages. The U–Pb and Re–Os isotope systems provide an excellent means of dating the mineralization itself and additionally place constraints on the ore genesis and metal source. Zircons separated from the quartz–chalcopyrite–pyrite veins include both detrital and magmatic groups. The magmatic zircons confine the maximum age of chalcopyrite–pyrite mineralization to 142.0 ± 1.5 Ma. The Re–Os results yield an age of 141.1 ± 1.1 Ma, which represents the age of the chalcopyrite–pyrite mineralization quite well. The common Os contents are notably low (0.5–20.1 ppt) in all samples. In contrast, the Re contents vary considerably (3.0–199.2 ppb), most likely depending on intensive boiling, which resulted in an increase of Re within the pyrite. This study demonstrates that the main chalcopyrite–pyrite mineralization occurred late in the magmatic history and was linked to a deeper intrusion involving dominant mantle-derived materials. This mineralization event might be related to the Early Cretaceous lithospheric destruction and thinning of the SMNCC.