平衡剖面的制作流程及其地质意义

平衡剖面技术是地质思维和计算机技术的结晶,使对断层构造的研究提高到定量阶段,其依据是在垂直构造走向的剖面上,地层长度和面积(2D)或体积(3D)是均衡的。在此原理基础上利用数学手段对盆地的构造发育史进行正演和反演模拟,直观地再现地下构造的原始几何形态,迅速提供地震剖面的构造解释方案,并对解释结果进行检验(不平衡的剖面其解释一般有问题),为深刻认识构造发育史、分析油气运移及聚集规律提供依据,提高了工作效率。其结果也为盆地模拟、油藏模拟、定量计算构造伸缩量等地质研究打下了坚实的基础[1]。     

Silicon limitation on primary production and its destiny in Jiaozhou Bay, China——Ⅳ：Study on cross-bay transect from estuary to ocean

The authors analyzed the data collected in the Ecological Station Jiaozhou Bay from May 1991 to November 1994, including 12 seasonal investigations, to determine the characteristics, dynamic cycles and variation trends of the silicate in the bay. The results indicated that the rivers around Jiaozhou Bay provided abundant supply of silicate to the bay. The silicate concentration there depended on river flow variation. The horizontal variation of silicate concentration on the transect showed that the silicate concentration decreased with distance from shorelines. The vertical variation of it showed that silicate sank and deposited on the sea bottom by phytoplankton uptake and death, and zooplankton excretion. In this way, silicon would endlessly be transferred from terrestrial sources to the sea bottom. The silicon took up by phytoplankton and by other biogeochemical processes led to insufficient silicon supply for phytoplankton growth. In this paper, a 2D dynamic model of river flow versus silicate concentration was established by which silicate concentrations of 0.028–0.062 μmol/L in seawater was yielded by inputting certain seasonal unit river flows (m³/s), or in other words, the silicate supply rate; and when the unit river flow was set to zero, meaning no river input, the silicate concentrations were between 0.05–0.69 μmol/L in the bay. In terms of the silicate supply rate, Jiaozhou Bay was divided into three parts. The division shows a given river flow could generate several different silicon levels in corresponding regions, so as to the silicon-limitation levels to the phytoplankton in these regions. Another dynamic model of river flow versus primary production was set up by which the phytoplankton primary production of 5.21–15.55 (mgC/m²·d)/(m³/s) were obtained in our case at unit river flow values via silicate concentration or primary production conversion rate. Similarly, the values of primary production of 121.98–195.33 (mgC/m²·d) were achieved at zero unit river flow condition. A primary production conversion rate reflects the sensitivity to silicon depletion so as to different phytoplankton primary production and silicon requirements by different phytoplankton assemblages in different marine areas. In addition, the authors differentiated two equations (Eqs. 1 and 2) in the models to obtain the river flow variation that determines the silicate concentration variation, and in turn, the variation of primary production. These results proved further that nutrient silicon is a limiting factor for phytoplankton growth. This study was funded by NSFC (No. 40036010), and the Director's Fund of the Beihai Sea Monitoring Center, the State Oceanic Administration.     

断层相关褶皱理论在准噶尔盆地南缘山前带构造研究的应用

利用断层相关褶皱的构造几何分析方法，对准噶尔盆地南缘山前复杂构造带内基于地震剖面进行了构造解析，搭建了中、东段的构造轮廓和构造组合样式，认为东段阜康断裂带主要表现为至地表的推覆逆掩。由于位移量大部分转移至地表，阜康断裂带的前陆部分无喜山期构造带；西段造山带内的挤压往前陆方向传递过程中以前列式不断释放其位移量，造成在纵向上呈现三排主要的断层相关褶皱带。根据正演平衡地质剖面制作技术对山前复杂构造区地震剖面反射波的构造识别进行了模拟与探讨。     

VERTICAL PROFII,ES OF CHL-A AND PRIMARY PRODUCTIVITY IN THE MIDDLE CONTINENTAL SHELF AREA AND EDDY AREA OF THE EAST CHINA SEA

Vertical profiles of chl-a and primary productivity in the middle continental shelf area and eddy area of the East China Sea were studied using data from a cruise in the East China Sea in February to March, 1997 and a cruise in July, 1998. The results showed that chl-a vertical distribution closely related to in situ hydrological and nutrient conditions. Chla-a concentration ranged from 0.22 to 0.35 mg/m³ and 0.93–1.09 mg/m³ in the eddy area and in the middle continental shelf area, respectively. In both areas, chl-a concentrations in deep layers were slightly higher than those in shallow layers, but was of the same order of magnitude. In summer, when a thermocline existed in the water column, highest chl-a concentrations appeared at the base of the thermocline layers in both areas. In the eddy area, chl-a concentration maximized at 31.743 mg/m³, and averaged 1.143 mg/m³ below 30 m depth. In the middle continental shelf area, the highest chl-a concentration was 2.120 mg/m³, the average was 1.168 mg/m³. The primary productivity reached 1418.76 mgC/(m²·d) in summer and 1360.69 mgC/(m²·d) in winter. In the eddy area, the primary productivity was 787.50 mgC/(m²·d) in summer and 159.04 mgC/(m²·d) in winter. Vertical carbon sinking rate from the deep layer to the bottom in both areas is also discussed in this paper. Contribution NO. 4183 from the Institute of Oceanology, Chinese Academy of Sciences. Project No. 49636210 supported by NSFC.     

Biogenic silicate accumulation in sediments, Jiaozhou Bay

1 INTRODUCTION Silicate, or silicic acid (H4SiO4), is a very im- portant nutrient in the ocean. Unlike other major nu- trients such as phosphate and nitrate or ammonium, which are needed by almost all marine plankton, silicate is an essential chemical req…     

河南桐柏老湾花岗岩体锆石SHRIMP U-Pb年龄及其地质意义

通过对河南桐柏老湾花岗岩体开展锆石SHRIMP U-Pb测年,获得了一个高精度的U-Pb年龄(132.5±2.4)Ma,比较可靠地限定了老湾花岗岩体的形成时代属于燕山中期,而不是前人所认为的燕山晚期.结合区域构造-岩浆活动时间,认为在燕山中期,桐柏及其邻区存在次比较重要的构造-岩浆事件,老湾花岗岩体是这次构造-岩浆活动事件的产物.     

浙江省长兴县煤山剖面二叠—三叠系过渡地层中的黑碳记录及其地质意义

首次报道了浙江煤山二叠-三叠系界线地层中黑碳的含量及其碳同住素的变化特征。黑碳含量在26层存在一个明显的峰值,含量高达0．51％。黑碳与总有机碳比值从25层底部开始持续升高,在26层达到最高,稳定在0．40以上。黑碳的碳同位素在24层和25层之间有一个陡然的降低,降低幅度达2‰,在25和26层中则存在一个幅度达3‰的缓慢降低,总降低幅度达5‰。黑碳是动植物和化石燃料燃烧的天然记录,浙江煤山二叠-三叠系界线附近黑碳特征反映了二叠纪末期陆地生态系统发生了突然的衰退,发生了强烈的天然大火。根据事件层大火燃烧的长期性或频繁的特征,以及黑碳同位素大幅度陡然降低和缓慢降低,认为燃烧源除了陆地植被外,还有其他富含轻碳的化石燃料,即大火的燃烧源除了植被外,还可能有煤和甲烷水合物等。浙江煤山剖面的黑碳记录,反映了二叠-三叠纪之交地球陆地环境的剧烈变化,有助于理解和揭示生物大灭绝的过程和原因。