江苏宜兴骆驼墩遗址地层7500～5400BC的海侵事件记录

在考古发掘基础上,野外共采集样品217个,对遗址地层剖面中63个样品进行了有孔虫、植物碎屑及种子化石等的鉴定分析,对4个地层相关样品进行了14C测年及相关分析。在第10层的泥炭层中发现底栖有孔虫2种1属,即压扁卷转虫（Ammonia compressiuscula）和近亲卷转虫相似种（Ammonia cff.sobrina）,表明全新世以来骆驼墩遗址及其附近区域在马家浜文化出现之前的7500-5400BC之间曾经历过海侵事件;共发现植物化石9种450颗,鉴定结果共统计出4（科）属,即Polygonum sp.（蓼属未定种）、Scirpus sp.（藨草属未定种）、Najas sp.（茨藻属未定种）、Physalis sp.（酸浆属未定种）,多属湖泊、沼泽等水生环境。     

2018年和2008年1～2月影响我国的持续低温事件及其对比分析

2018年1月中下旬至2月初我国发生了一次大范围的持续低温异常事件,给国民经济和人们生活带来了很大的不利影响。这次持续低温事件与众所周知的2008年1月发生在我国南方的持续雨雪冰冻事件（简称“0801”事件）有一个共同点,二者都是发生在La Ni?a和前秋北极海冰显著减少的背景之下。对比这两次事件发生的大气环流和热力背景,对认识冬季持续极寒事件的形成有重要意义。本文利用NCEP/NCAR大气环流再分析资料和NOAA卫星观测OLR资料,对这两次过程进行了比较。结果显示,与“0801”事件相比,2018年1月中下旬的低温事件表现出以下明显不同的特征:（1）过程持续短,冷空气路径偏东;（2）乌拉尔阻塞和东亚大槽并存,呈“西高东低”型,不同于“0801”高纬阻塞和低纬南支槽并存的“北高南低”型;（3）异常的环流型与自大西洋经乌拉尔山至东亚传播的波列有关,西伯利亚高压持续时间短;（4）热带对流活跃在海洋性大陆和西太平洋,不同于“0801”主要在印度洋。后者对该年南支槽和西太平洋副热带高压增强有显著贡献。最后,2018年过程期间水汽输送也不如“0801”强,导致降水弱。     

论辽西四合屯地区早白垩世构造-火山活动及生物事件

四合屯地区位于一个中生代火山一沉积盆地之中。该区早白垩世的主要构造行迹为NE向和NW向的断裂构造;这些断裂构造控制着火山一沉积盆地的边界和一些火山机构的分布。野外填图表明,该盆地内的早白垩世地层仅出露有义县组。义县组可进一步划分为3个段：第1段为含有沉凝灰岩夹层的基性、中基性火山岩;第2段是含有凝灰岩夹层和枕状熔岩的陆相沉积岩;第3段主要为玄武岩类。热河生物群(其中包括腹足类、双壳类、叶肢介、介形类、昆虫、鱼类、两栖类、爬行类、鸟类、哺乳类以及植物)化石主要产于义县组一段沉凝灰岩和二段的湖相泥质页岩中。化石发掘和微量元素分析表明,热河生物群经历了集群死亡和快速掩埋,火山活动的有毒气体是生物灾难事件的主要因素。根据同位素测年,义县组的时代为早白垩世。在此基础上,本文讨论了四合屯地区早白垩世构造一火山活动与生物事件的演化阶段：A阶段为盆地雏形的产生和早期的热河生物群;B阶段为第一次火山活动和生物灾难事件;C阶段为火山活动间歇期和热河生物群的繁衍;D阶段为火山喷汽与热河生物群的灾难事件;E阶段为火山灰沉降;F阶段为结束期。     

Sea Level Changes Along Bangladesh Coast in Relation to the Southern Oscillation Phenomenon

Interannual variations of sea level along the Bangladesh coast are quite pronounced and often dominate the long-term sea level trends that are taking place. The El Niño/Southern Oscillation (ENSO) induced variation is an important component of interannual mode of variations. The present article deals with the relationship between the sea level variations along the Bangladesh coast and the Southern Oscillation phenomenon. The mean tide level data of monsoon season (June to September) pertaining to Hiron Point (in Sundarbans) and Char Changa (on the mouth of Meghna River) have been analyzed and correlated to the Southern Oscillation Index (SOI). The annual variation of mean tide level in the coastal areas of Bangladesh reveals that the tide level reaches its peak during the monsoon season. The maximum tide level during the calendar year is recorded in August. Thus, it is not surprising that the inundation of the coastal belt of Bangladesh due to the floods is most common during the summer monsoon season, especially from July to September. Therefore, the sea level variations during the monsoon are of paramount importance to Bangladesh. The results of the present study show that both at Hiron Point and Char Changa there is a substantial difference between the mean tide level during the El Niño and La Niña monsoons. The mean tide level at Hiron Point is higher by about 5 cm during August of La Niña years as compared to that during the El Niño years. The difference at Char Changa, which is located at the mouth of Meghna River, is much higher. This is probably due to the increased fresh water discharge into the Meghna River during La Niña years. Thus at the time of crossing of a monsoon depression, the chances of widespread inundation are higher during a La Nin~a year as compared to that during an El Niño year. The Correlation Coefficients (CCs) between Mean Tide Levels (MTLs) at Hiron Point and Char Changa and the SOI during September (at the end of monsoon) are +0.33 and +0.39 respectively. These CCs are statistically significant at 90% and 95% levels, respectively. These results may find applications in the preparedness programs for combating sea level associated disasters in Bangladesh.     

Detection of ocean waves using satellite altimetry: Application to equatorial Kelvin waves

A new method for wave motion detection from satellite altimetric measurements of sea surface height is presented. The essence of the approach is to construct a two‐dimensional traveling‐wave Fourier series representation of the amplitude field within a prespecified oceanic region. The method employs an iterative, nonlinear least‐squares technique based on the Marquardt‐Levenberg algorithm to solve for model parameters describing characteristic features of the evolving wave system. The Marquardt‐Levenberg Fourier series (MLFS) algorithm was applied to Kelvin waves active during the 1986–1987 El Nino event in the equatorial Pacific ocean using GEOSAT Exact Repeat Mission altimetry data. Characteristics of the wave system were found to be in essential agreement with earlier field measurements and the observations of Cheney and Miller (1987) obtained using time series developed from GEOSAT data. The advantage of the present detection scheme lies in its speed and ability to determine a wave system's dispersion relation over a finite range of wavenumbers, and hence the group velocity of that system.     

Heavy Minerals and Rare Earth Elements in Coastal and Inland Dune Sands of El Vizcaino Desert,Baja California Peninsula,Mexico

A heavy mineral (HM) study and light and heavy rare earth elements (LREE and HREE) analysis were performed in coastal and inland dune sands, El Vizcaino Desert, Central Baja California Peninsula, Mexico. Our study shows high abundances of hornblende and apatite in the El Vizcaino dune sands, suggesting a dominance of granodiorites/intermediate plutonic rocks and marine authigenic phosphorite in the dune sands. There is a relationship between unstable heavy minerals like hornblende, pyroxenes, and sphene, and heavy rare earth elements (HREE) that suggests that unstable heavy minerals are potential carriers of HREE in the dune fields. However, there is a slight depletion of HREE in relation to LREE, especially in one locality of the inland dunes probably associated with the wind regime and weathering of unstable heavy minerals in the sands. Inland, transitional, and coastal dune fields can be observed as different dune provinces by means of grouping HM and REE data in two separate dendograms. It seems that HREE are correlated with fine-grained sand sizes and correlated with high CIA values linked to slightly weathered sands.     

Seismic activity recorded by a single OBS/H near the active Longqi hydrothermal vent at the ultraslow spreading Southwest Indian Ridge (49°39′ E)

ABSTRACT

In this paper, we describe the results of a first pilot experiment of passive seismic monitoring near the active Longqi hydrothermal vent at the Southwest Indian Ridge during Chinese cruise DY115-30. During 102-day experiment, we recorded over 2,000 seismic events on a single ocean bottom seismometer with hydrophone close to the hydrothermal field. We classified these events into the following three classes based on their time–frequency characteristics: (1) volcano tectonic microearthquakes (VTMs); (2) regional earthquakes; (3) short-duration events (SDEs). We preliminarily located the 1,277 VTMs using a single-station location method. Our results revealed hypocenters primarily beneath the axial valley ridge which is about 10?km away from hydrothermal vent and extending to the upper mantle at a depth of 15?km. Two discrete swarms of VTMs occurred during our survey period. The SDEs show a complex frequency characteristics ascribed to clusters of monochromatic waves around different frequencies. This suggests that SDEs result from combination of harmonic waves resonating in fluid-filled pipes and cracks.     

江苏宜兴骆驼墩遗址地层7500-5400BC的海侵事件记录

Based on archaeological excavations, 217 samples were collected from the Luotuodun Site. Of them 63 samples from the section plane of the site layer were used for identification analysis of foraminifera, plant debris and seed fossils, and four samples were used for ¹⁴C dating and relevant analysis. Through many kinds of experiments, we have drawn some conclusions. Firstly, benthic foraminifera, such as Ammonia compressiuscula and Ammonia cff. sobrina, are found in the 10th layer, indicating that between 7500 and 5400 BC, i.e. before the emergence of the Majiabang Culture, Luotuodun Site and its nearby regions had ever experienced a marine transgression event. Secondly, we have found 450 plant fossils in this site, such as Polygonum sp., Scripus sp., Najas sp., Physalis sp., which indicated lacustrine or swamp environment.     

Using Ancillary Information to Improve Hypocenter Estimation: Bayesian Single Event Location (BSEL)

We have developed and tested an algorithm, Bayesian Single Event Location (BSEL), for estimating the location of a seismic event. The main driver for our research is the inadequate representation of ancillary information in the hypocenter estimation procedure. The added benefit is that we have also addressed instability issues often encountered with historical NLR solvers (e.g., non-convergence or seismically infeasible results). BSEL differs from established nonlinear regression techniques by using a Bayesian prior probability density function (prior PDF) to incorporate ancillary physical basis constraints about event location. P-wave arrival times from seismic events are used in the development. Depth, a focus of this paper, may be modeled with a prior PDF (potentially skewed) that captures physical basis bounds from surface wave observations. This PDF is constructed from a Rayleigh wave depth excitation eigenfunction that is based on the observed minimum period from a spectrogram analysis and estimated near-source elastic parameters. For example, if the surface wave is an Rg phase, it potentially provides a strong constraint for depth, which has important implications for remote monitoring of nuclear explosions. The proposed Bayesian algorithm is illustrated with events that demonstrate its congruity with established hypocenter estimation methods and its application potential. The BSEL method is applied to three events: 1) A shallow Mw 4 earthquake that occurred near Bardwell, KY on June 6, 2003, 2) the Mw 5.6 earthquake of July 26, 2005 that occurred near Dillon, MT, and 3) a deep Mw 5.7 earthquake that occurred off the coast of Japan on April 22, 1980. A strong Rg was observed from the Bardwell, KY earthquake that places very strong constraints on depth and origin time. No Rg was observed for the Dillon, MT earthquake, but we used the minimum observed period of a Rayleigh wave (7 seconds) to reduce the depth and origin time uncertainty. Because the Japan event was deep, there is no observed surface wave energy. We utilize the prior generated from the Dillon, MT event to show that even in the case when a prior is inappropriately applied, high quality data will overcome its influence and result in a reasonable hypocenter estimate.     

贵州主汛期极端降水事件及其环流特征分析

利用贵州地区52个测站1961-2006年历年主汛期(6-8月)逐日降水资料,定义了不同台站的极端降水阈值,统计了贵州近46年主汛期极端降水事件发生的频次,并分析了极端降水的时空分布特征、周期振荡特征以及极端降水事件典型多年、少年的环流特征.结果表明:贵州主汛期极端降水自北向南逐渐增大,极端降水事件存在着明显的年际、年代际变化特征,并存在2.9 a、20 a的周期振荡特征,在贵州主汛期极端降水事件偏多和偏少时期,其环流特征存在着显著的差异.