Sediment dynamic processes of the Yuehu inlet system, Shandong Peninsula, China

In order to investigate the sediment dynamic behavior of the Yuehu, a small inlet system characterized by abundant sediment supply and rapid sediment infilling, measurements and sampling were undertaken to obtain data sets of tidal water levels, current velocities, suspended sediment concentrations, grain size parameters, deposition rates and organic carbon contents. Sediment budget and the time–velocity asymmetry patterns of the inlet system were analyzed. The results show that the deposition rates are relatively high within the tidal basin. The total sediment flux cannot be balanced by the input from the open sea, the aerosol and biological production; rather, the material from land (which has been intensified by agricultural activities over the past several decades) represents a major component for the balance. Thus, the denudation rate must be reduced to protect the Yuehu as a natural reserve. Furthermore, it is found from the present study that the Yuehu inlet system exhibits all of the four time–velocity asymmetry patterns with varied frequencies of occurrence, compared with the two asymmetry patterns identified for larger inlet systems; such phenomena are partly due to the adjustment of entrance channel geometry. This behavior may be representative of the small tidal inlets at their late stage of morphological evolution and, therefore, may be utilized to prolong the lifespan of small inlet systems.     

太湖大气氮、磷营养元素干湿沉降率研究

分析了2002年7月—2003年6月太湖周边地区太湖站、拖山岛、东山站、无锡、苏州、湖州、常州、金坛等8个站、点大气TN、TP沉降通量和降水化学组成观测资料,测定和计算了水气界面TN、TP的表观总沉降率(RT)、湿沉降率(RW)和干沉降率(RD)。太湖大气TN的年平均RT为4226kg/(km2.a),TP的年平均RT为306kg/(km2.a)。大气TN、TP的年沉降负荷分别占由环湖河道等点污染源输入的N、P总负荷的48.8%和46.2%。指出形成太湖大气TN污染的主要途径是湿沉降,而大气TP污染则主要来自气溶胶等固体物质的干沉降;小雨携带入湖的大气TN、TP污染物通量高于中雨和大雨。TN总沉降率曲线在春季3—5月出现高峰值的现象对太湖水体的富营养化具有潜在的促进影响。     

鄂尔多斯盆地临兴—神府地区奥陶系马五段沉积相发育控制因素及沉积模式

鄂尔多斯盆地奥陶系碳酸盐岩是重要的天然气赋存单元。通过对盆地东缘的临兴—神府地区奥陶系马家沟组五段发育的沉积相类型和沉积模式进行研究和总结,结合岩芯、薄片、测井和综合地质录井数据等资料,判定了研究区属陆表海潮坪相沉积。受矿物蒸发析出机理、白云岩生成机理、盆山耦合关系3个基础地质模型控制,结合海平面变化,建立了研究区陆表海碳酸盐岩-蒸发岩综合沉积模式:海退-蒸发背景下,自隆向坳主要发育云坪(泥云坪)—含膏云坪—膏坪等潮上—潮间相带微相;海侵背景下,自隆向坳主要发育灰云坪、云灰坪和灰坪等潮间—潮下带微相。该沉积模式较好地解释了研究区马家沟组五段的复杂岩相和沉积微相的分布规律,预测结果后被钻井证实。成果对提高后续勘探成效和指导类似地区的沉积储层研究具有积极意义。     

滇中元江古元古代浊积岩特征及其地质意义

对滇中元江地区调查研究发现一套以钙质浊积岩-碎屑浊积岩组合为特征的岩石序列。测制的剖面由2个钙质浊积岩-碎屑浊积岩旋回组成,发育大量不完整的鲍马序列组合及粒序层理、斜层理、包卷层理、槽模构造、透镜状构造等典型浊积沉积构造,且岩石成熟度及分选度都较低。上部还发育一套凝灰质球粒石英岩,粒序层理发育,在其中获得了LA-ICP-MS锆石U-Pb年龄1102±76Ma和1713±48Ma(YJgzn-03),具有明显铅丢失现象;对侵入地层中的石英正长斑岩进行年代学研究,获得了LA-ICP-MS锆石U-Pb年龄349±13Ma和1732±13Ma(YJgzn-02),上部未发生明显铅丢失的平均年龄为1718±30Ma,应为成岩期年龄。两者的锆石都具环带结构,Th/U值都大于0.4,都明显发生了铅丢失,且形成时代相近,应为同期岩浆作用的结果。推测该套地层沉积或受到后期热蚀变年龄为1713±48～1718±30Ma,其沉积年龄应早于古元古代晚期。对比区域昆阳群及前人划分的古元古代地层,认为这套地层下伏于昆阳群之下,应属于早于古元古代晚期(1.7Ga)的碳酸盐前缘-陆棚斜坡浊积岩体系,建议依据地名定义为古元古代"曼林组"(Pt1m)。     

Connections between Evaporite Deposition and Glacial Periods since the Middle Pleistocene in Salt Lakes in the Western Qaidam Basin, China

The Quaternary was the main evaporite deposition period in the Qaidam Basin (QB), but the correlation between the evaporite deposition period and the glacial period is still unclear. In this study, the research objects are primarily evaporite-bearing strata in a 461.58 m-long drill core in the QB. X-ray powder diffraction (XRD) and scanning electron microscopy (SEM) were applied to study the evaporite minerals, U-Th dating being applied to construct the 230Th geochronological framework. Evaporite deposition from Marine Isotope Stage (MIS) 15 to MIS 4 in the borehole was reconstructed via mineralogical and geochronological data. The evaporite minerals are mainly halite (NaCl), mirabilite (Na2SO4·10H2O), thenardite (Na2SO4) and gypsum (CaSO4·2H2O). A total of 9 effective 230Th data points, ranging from 492.5 ± 43.0 ka to 62.0 ± 11.9 ka, were obtained. The depositional age of the earliest halite layer in the borehole is 592.5–563.0 ka. There were mirabilite deposits in the QB during the cold glacial environment of MIS 6. During MIS 4, the study area desiccated, with mirabilite and halite being deposited. This study suggests that mirabilite is an indicator mineral for the glacial environment in the QB, while halite deposition does not correspond well to glaciation.     

Coupling near-surface geomorphology with mangrove community diversity at the estuarine scale: A case study at Dongzhaigang Bay,China

Coastal wetlands are key features of the Earth's surface and are characterized by a diverse array of coupled geomorphological and biological processes. However, the links between the distribution of biodiversity (for example, species and structural diversity) and the formation of coastal geomorphology are not well-understood on a landscape scale most useful to coastal zone managers. This study describes the relationship between select geomorphological and biological mangrove community features (i.e. species composition and functional root type) in a landscape-distributed coastal zone of Dongzhaigang Bay, north-eastern Hainan Island, China. A total of 11 mangrove species and five functional aerial root types were encountered, with the location of species by root types being controlled by the elevation of the soil surface. Plank roots, prop roots and pneumatophores occupied the lowest intertidal elevations, while knee roots and fibrous roots of the mangrove fern, Acrostichum aureum, preferred the highest intertidal elevations. Surface sediment deposition in areas with mangroves was greater than deposition in non-mangrove forest zones, establishing an important biological mechanism for this large-area response because surface erosion/compaction was also more prominent within mangrove roots. Indeed, functional root type influenced the magnitude of deposition, erosion and compaction, with knee roots and pneumatophores being more effective in promoting deposition and preventing surface erosion/compaction than prop roots. These results indicate a potential role for vegetation type (especially functional root type) to influence coastal geomorphological processes at large landscape scales. While soil surface elevation is correlated to the distribution of mangrove species and functional root types, a significant feedback exists between elevation change and the capacity of those root types to influence coastal geomorphological differentiation within sustainable intertidal elevations. An enhanced understanding of geomorphological development, mangrove species distribution and functional root type may improve management to support nature-based solutions that adjust more effectively to sea-level rise through feedbacks.     

内陆河三角洲堆积体形成发展过程

通过概化水槽试验对水流泥沙从内陆河进入浅水湖泊后的三角洲堆积体形成发展过程进行研究。试验结果表明,在平面形态上,三角洲堆积体的形成发展过程可分3个阶段:第一阶段,水流泥沙在初期依次按小沙波体、带状沙波体、扇形三角洲堆积体和舌状三角洲堆积体形态形成发展,堆积体表面无明显主河槽且两侧区域无串沟;第二阶段,水流泥沙沿堆积体表面河槽在左侧区域和右侧区域之间交替推进;第三阶段,水流泥沙沿新河槽在摆动中同步推进。在纵向推进中,第一阶段初始较大,受横向展宽影响逐渐减弱;第二阶段以相对稳定的速率交替推进;第三阶段呈减弱趋势,最终保持同步推进速率。在垂向上,堆积体以稳定的速率淤积抬高发展;在横向上,水流泥沙在河槽主流摆动中不断横向输移泥沙。     

钱塘江河口水流-河床相互作用及对盐水入侵的影响

通过长系列实测水文、地形资料分析,钱塘江河口上段河床具有大冲大淤和洪冲潮淤的演变特性,影响河口上段的潮汐强弱,进而影响盐水入侵。若年内丰水期径流量大,则河床出现“大冲”,河床容积增大,潮汐增强,导致秋季强潮期盐水入侵加剧;反之,若年内丰水期径流量小,河床容积较小,导致秋季强潮期盐水入侵减弱。结果表明,钱塘江径流对盐水入侵存在直接和间接影响:直接影响是盐水入侵与径流量成反比;间接影响是通过径流冲刷河床,引起潮汐增大,间接导致盐水入侵加剧,这是钱塘江河口大冲大淤以及对潮汐巨大反作用的特性造成的。     

Regional heat safety thresholds for athletics in the contiguous United States

Exertional heat illnesses affect thousands of athletes each year across the United States (U.S.). Heat safety guidelines such as those developed by the American College of Sports Medicine (ACSM) are widely used to direct activities based on environmental conditions but rely on a uniform set of heat safety categories. Due to geographic variations in heat exposure and acclimatization, however, lower heat safety thresholds may be needed in areas with cooler climates. Our study addresses this shortcoming by developing regional guidelines for athletic activity that use relative thresholds of a commonly used heat metric -- the wet bulb globe temperature (WBGT). We employed a unique WBGT climatology for the contiguous U.S. to determine locally extreme WBGTs, defined as the 90th percentile warm season daily maximum value, for 217 stations. Three heat safety regions were identified based on local extremes: Category 3 (WBGTs ≥ 32.3 °C), Category 2 (30.1–32.2 °C), and Category 1 (≤30 °C). Geographically, Category 3 encompasses much of the southeastern quadrant of the U.S. along with portions of the Southwest, and the Central Valley of California; Category 2 areas extend in an arc from the interior Northwest through Nevada and portions of the Midwest, Ohio Valley, and Northeast; and Category 1 locations include the Pacific Coast, New England, and the northern tier of the country. Associated regional activity guidelines based on those developed by the ACSM and the Georgia High School Association (GHSA) were developed for each heat safety region.     

Environment and Age of the Upper Devonian‒Carboniferous Zhulumute and Hongguleleng Formations, Junggar Basin, NW China: Ichnological and Palynological Aspects

Two Upper Devonian to Lower Carboniferous sections, namely the Bulongguoer and Haer(Gennaren area) in the Junggar Basin, Central Asian Orogenic Belt, in northwestern China were examined with regard to ichnology and palynology. The deposits of the Hongguleleng Formation and Namu Member of the Heishantou Formation, respectively, are mostly unbioturbated or poorly bioturbated, with poorly diversified trace fossils, which indicate unfavourable conditions for the burrowing benthic community during the Late Devonian and Early Carboniferous. The main factor governing the growth of the bioturbating population was the rapid sedimentation of fine-grained, volcanic material documented as tempestites, which buried the benthic fauna. In the Bulongguoer section, the presence of miospores Teichertospora torquata and Grandispora gracilis enabled identification of the broad Teichertospora torquata–Grandispora gracilis Miospore Zone from the transitional Frasnian/Famennian interval. More accurate identification of palynostratigraphical levels(DE and CZ Miospore zones) is only tentative. On the basis of palynofacies analysis, samples from the lower Bulongguoer section indicate deposition in more proximal conditions, whereas samples from the top of the section indicate deposition in a more distal environment. In the Haer section, only a general biostratigraphic indication for the Tournaisian was possible, owing to poor preservation of organic matter.