Wind-wave transformations in an elongated bay

In order to determine wave transformations in an elongated bay, a numerical solution was used to interpret yearlong records of bottom pressure and wind velocity obtained at the mouth and head of Concepción Bay, on the Gulf of California side of the Baja California peninsula. Observed wind waves were predominantly produced by southeastward winds in the winter and north–northwestward winds in the summer. Typical mean wave periods at the bay entrance were between 3 and 5 s. In contrast, the waves at the head of the bay had predominant periods <3 s. The energetic long-period swell waves were dissipated somewhere in the bay as they were not observed at the head of the bay. This study centered in identifying the effects that caused swell waves to attenuate in the bay. The ‘Simulating WAves Nearshore (SWAN)’ model was used to determine the cause for such wave attenuation. Model results showed that swell waves were attenuated because of the combined effects of bottom friction, wave breaking, whitecapping, refraction and wave blocking by the coastline. Most of the attenuation (close to 90%), however, was caused by wave blocking owing to the change of coastline orientation of the bay. This wave blocking mechanism should therefore be explored further in embayments of complex coastline morphology.     

Dynamics of a Prorocentrum minimum bloom along the northern coast of Sinaloa,Mexico

To investigate the relative importance of mesoscale physical events, such as upwellings and physical and chemical variables during an algae bloom of Prorocentrum minimum, 25 sampling sites were established offshore of the Navachiste Lagoon Complex on the east side of the Gulf of California. Samples were analyzed for phytoplankton concentration, water chemistry, and temperature during November 1999, January, March, April, May, and August 2000. Satellite imagery of sea surface temperature (SST) for April 2000 was processed to obtain a synoptic view of the area during the extraordinary bloom of P. minimum in the open waters of the Gulf of California. The bloom was associated with change of oceanographic conditions from moderate winds to calm period, temperature increase and high nitrate (NO₃⁻-N) and ammonia (NH₄⁺-N) content in the offshore waters. Depletion of these nutrients during the bloom suggests that this species uses both types of nitrogen substrates. Cysts in the northernmost sampling stations in January and March indicate that upwelling water, rich in nitrates, also carried a seed stock population of P. minimum. SST patterns in the satellite imagery suggest wind-forcing as the responsible mechanisms triggering the algal bloom offshore of the Navachiste Lagoon Complex.     

Distribution of radioactive pollution of 238U, 232Th, 40K and 137Cs in northwestern coasts of Persian Gulf, Iran

A reconnaissance study has been made of the distribution of 238U, 232Th, 40K and 137Cs and geochemical features in soils and sediments samples at various locations in the northwestern coast of Persian Gulf. Activity concentration levels due to radionuclides were measured in 30 soil and sediment samples collected from this region. From the measured spectra, activity concentrations were determined for 40K (range from 146 to 500 Bq kg(-1)), 137Cs (from 5 to 20 Bq kg(-1)), 238U (from 21 to 65 Bq kg(-1)) and 232Th (from 15 to 45 Bq kg(-1)) with lowest limit detection (LLD) of 68, 3.2, 4.3 and 4.3 Bq kg(-1), respectively. The dose rate from ambient air at the soil ranges was between 19 and 58 nGy h(-1) with an average of 37.41+/-9.66 nGy h(-1).     

渤海湾盆地曙光油田曙266油藏沉积微相及储层的非均质性研究

曙266断块油藏杜家台油层为扇三角洲前缘沉积。本次研究精细划分出水下分流河道、水下分流间湾、水下天然堤、河口坝、远砂坝、前缘席状砂及前三角洲泥7个沉积微相,其中水下分流河道是本区储层的主要成因类型。平面上,杜家台油层属强非均质性,储层层内及层间属中等——强非均质性,在微观上则表现为细喉道、高配位数的特点。本区储层非均质性主要受沉积环境的控制。      

北部湾近海结构物污损生物研究

对海洋结构物而言,污损生物不仅增加其水下部位表面粗糙度,显著增大波浪所引起的动力载荷效应,sup>[1],而且还能改变金属腐蚀过程,引起局部腐蚀或穿孔腐蚀,并妨碍水下检测、保养和维修等工作的进行[2,3].因此,在开发利用海洋资源时,必须预先对特定海区污损生物群落的结构特点及发展趋势有所了解,以便人们经济、有效的角度选择防污手段和制定清除保养计划.     

关于长江三角洲两大开发工程的构想

为了解决上海缺乏深水港址和宁波、舟山港腹地范围狭小的问题,提出了两个相互关联的宏大构想：一是在杭州湾建造锁海大坝并展开大规模的围垦造陆;二是兴建宁波至舟山的跨海交通与输水工程。这两大构想一旦付诸实施,其直接效益主要有二：１．为长江三角洲增加数千平方公里的土地;２．今后可望在宁波－舟山建成世界超级大港和千万人口级特大城市。更进一步的影响则是在锁海大坝沿线和钱塘江下游沿岸将出现两个新的产业密集带与城镇     

Distribution and dispersal pattern of clay minerals in surface sediments, eastern Beibu Gulf, South China Sea

Clay minerology of sediments are useful in determining distribution,sources and dispersal routes of fine-grained sediments.In the present paper,clay minerals of surface sediments throughout the eastern part of Beibu Gulf has been investigated to reveal sources and transport of detrital finegrained sediments.Four distinct clay mineral suites were observed from cluster analysis of clay mineral compositions of the samples.From the distribution pattern of clay minerals,we conclude that kaolinte in the eastern gulf is mainly derived from South China Landmass;Smectite could not be transported mainly by surface current from north-western Hainan Island,and maybe minor portion of it from Red River;Illite is mainly transported by the currents from South China Sea.Chlorite has two sources,namely South China Sea and South China Landmass.The Zhujiang River derived sediments could not be one of the sources for the clay mineral here,because of very different composition and ratios.The distribution pattern of clay minerals in the eastern Beibu Gulf is mainly controlled by fine-grained sediment source and local currents.The Silt/Clay,Smectite/Kaolinte,and Smetite/(Chlorite+Illite) ratios could be used as indicators of fine-grained sediment dispersal in the gulf.     

北部湾防城港沿岸土壤137Cs背景值及表层分布特征

在北部湾防城港沿岸采集土壤样品,通过测量样品¹³⁷Cs比活度及有机质含量,确定了¹³⁷Cs背景值,分析表层土壤中¹³⁷Cs分布特征,并探讨样品中¹³⁷Cs活度与有机质含量的关系。结果表明：研究区土壤中¹³⁷Cs背景值为626±15 Bq/m²,自然因素和人为活动对¹³⁷Cs在海岸带表层土壤中的再分配起到重要作用,不同表层样中¹³⁷Cs比活度高低表现为：自然林地>水稻田>旱田>草地>河口海湾。把研究区土壤表层样及P01剖面样中¹³⁷Cs含量与有机质含量进行相关性分析,结果表明：两者相关性显著,相关系数分别为0.414和0.732。通过探讨研究区¹³⁷Cs背景值及沿岸表层土壤¹³⁷Cs分布特征,可为进一步定量研究北部湾沿岸土壤侵蚀和堆积状况以及评价防城港红沙核电站运行后对环境的影响提供科学依据。     

Sea level rise in the north-western part of the Arabian Gulf

Relative sea level variations in the north-western part of the Arabian Gulf have been estimated in the past using no more than 10 to 15 years of observations. In this study, we have almost doubled the period to 28.7 years by examining all available tide gauge data in the area and constructing a mean gauge time-series from seven coastal tide gauges. We found for the period 1979–2007 a relative sea level rise of 2.2 ± 0.5 mm/year. Using the subsidence observed at 6 GPS stations within a radius of 100 km of the tide gauges as an indication of the vertical land motion, the corresponding absolute sea level rise is 1.5 ± 0.8 mm/year that is in agreement with the global estimate of 1.9 ± 0.1 mm/year (Church and White, 2011) for the same studied period. By taking into account the temporal correlations we conclude that previous published results underestimate the true sea level rate uncertainty in this area by a factor of 5–10.     

Ca. 13 Ma strike-slip deformation in coastal Sonora from a large-scale,en-echelon,brittle-ductile,dextral shear indicator: implications for the evolution of the California rift

The Rancho Nuevo semi-circular structure is a geomorphological structure defined by drainage patterns in coastal Sonora, about 160 km NW of Hermosillo. The structure is about 15 by 30 km, and it is cored by felsic to intermediate plutons (granodiorite, monzogranite, quartz-porphyry) covered by Miocene volcanic rocks. This work is focused on the deformation of the intrusives which cover most of study area.The plutons are a co-magmatic suite dated between 71 ± 1.1 and 67.9 ± 1.0 Ma (U-Pb zircon, LA-ICPMS). The most voluminous unit is a granodiorite characterized by conspicuous sigmoidal fractures at the scale of high resolution satellite images, along which rhyolite dikes were emplaced about 13.2 Ma. Magnetic fabric (AMS) and paleomagnetic data were collected from 27 sites in the granodiorite. Magnetic fabrics are weak but well developed, and are characterized by steep foliation planes with strikes that follow the sigmoidal fracture pattern and suggest NE-SW to NW-SE flattening after emplacement. The characteristic magnetization is of dual polarity, but it is dominantly reverse consistent with emplacement during chron C31r. The prevalent magnetization is southwest and moderately steep negative (ten sites), a discordant direction rotated clockwise about 41 ° ± 11 with respect to the expected Late Cretaceous reference direction, also indicating gentle southward tilt. There is, however, paleomagnetic evidence suggesting that the structure did not rotate as a rigid body, but it deformed internally instead. These data are interpreted to indicate that the Rancho Nuevo semicircular structure is a large-scale, dextral, brittle-ductile shear indicator. The age of the dikes and the fact that they are covered discordantly by rocks assigned to the tuff of San Felipe indicate that northwest, srike-slip, motion of Baja California peninsula (and thus the Pacific plate relative to North America) was accommodated by faults in coastal Sonora about 13 Ma ago.