云南广南早二叠世生物礁的基本特征及其造架生物——串管海绵化石

在我国西南南盘江地区广泛分布着二叠系生物礁。可分为两种类型:1)堤礁;2)孤立礁。前者一般沿碳酸盐台地的边缘分布,后者发育于盆地内孤立碳酸盐台地的边缘。广南生物礁的礁后灰岩由浅灰色块状骨架岩组成。造架生物以串管海绵、纤维海绵、tabulozoans等为主,往往有蓝绿藻包覆。骨架生物之间有极为发育的纤状方解石胶结物。本文共描述了串管海绵8属12种,它们是Waagenella salinaria irregalaris Zhang,Waagenella sp., Rhabdactinita of columnaria Yabe and Sugiyama, Rhabdactinia sp., Intrasporeocoelia hubeiensis Fan and Zhang,Intrasporeocoelia sp., Uvanella guangnanensis sp. nov., Girtycoelia sp., Colospongia of dubia Laube, Colospongta sp., Verticillites sp.,Lichuanospongta typica Zhang.     

舟山海域人工鱼礁选址基于AHP的权重因子评价

根据嵊泗站、岱山1、2号站和普陀1、2号站的实测数据以及舟山群岛附近13300号海图的标绘数据,运用阶层层次分析法,综合探讨了对以上测站所在的舟山海域人工鱼礁选址有影响的多项因子(水深、底质类型、地形坡度、生物密度、平均流速、离岸距离),并根据各影响因子的重要性程度确定其权重,建立了该海域人工鱼礁选址的多因子综合评价模式。结果表明,在以上6个影响因子中,水深因子对人工鱼礁投放影响最甚,其所占权重最大,对人工鱼礁投放影响居其次的因子依次为底质类型、地形坡度、生物密度、平均流速和离岸距离,其权重分别为0.459 9、0.185 8、0.140 6、0.075 7、0.070 4和0.067 7。     

渤海湾泥质海岸带近现代地质环境变化研究(Ⅱ):成果与讨论

渤海湾泥质海岸带国土资源大调查以其特有的方法、手段和要求,获得了一批带有地质调查特点的、关于全新世地层与近现代地质环境变化的阶段性成果,主要包括:1)该地区海岸带全新世地层具有4种沉积类型:(A)远离海岸的传统的"三分"型;(B)海相层与陆(海陆过渡)相层的多次交替;(C)末次冰期后期未接受沉积,全新统半咸水的海陆过渡相直接覆于历时约10～20ka的沉积间断面上,向上,进一步发育为海相层;(D)沿海低洼地区在末次盛冰期后的晚更新世晚期即已进入海侵阶段,晚更新世晚期与全新世早期的海陆过渡相沉积是连续的,向上继续发育海相层.2)从以海水影响为主的开放潮坪(及浅海区)环境转变为(陆源影响逐渐加强的)湖-盐沼环境,是研究区中晚全新世地质环境转变的重要特征,建立了表征这两种不同环境的非正式地层单位("灰色单元"与"黄色单元").3)牡蛎礁与贝壳堤的对比方案,以牡蛎礁对应潮坪的贝类繁盛期,牡蛎礁中的水平再搬运夹层和/或上覆泥质盖层(往往形成"岭地")对应贝壳堤成堤.4)大比例尺区调地质点(浅孔)揭示了中晚全新世(近现代)地质环境变化,编绘出约4500calB.P.以来小于1ka时段的二维、假三维环境系列图.一个实例是Ⅱ贝壳堤向陆侧的洼地甚至早于该堤的形成,推测洼地边缘的NNW向的埋藏线性凸起可能受同一方向的新构造活动控制.5)渤海湾沿海平原线性砂坝(障壁岛)-湖/盐沼成因假说.作为堆积贝壳堤正地形的补偿,堤前因"簸选"贝壳导致的潮坪负地形,同样可发育湖沉积.6)210pb/137Cs测年研究提供了该地区现代沉积速率的初步结果(＜0.1cm/a或＞3cm/a不等),据此将海岸带划分为不同的沉积类型区.     

三维生物礁滩建模及地震数值模拟

基于塔礁、点礁、生物滩等地质体的几何特征及地质特征,采用高精度的三维块状建模方法,建立了适合于复杂地区的三维礁滩复合体模型。该模型不但立体地反映了生物礁、生物滩及地层间的空间展布特征,还可以直观地体现了生物礁滩储层内部的物性差异。此外采用FK域三维波动方程数值模拟方法对其进行了地震波场数值模拟,得到了一系列具有代表性时间剖面上的地震波场响应特征,为正确认识实际生物礁滩的复杂结构和特性提供了依据。     

中扬子西部下志留统生物礁特征及其油气地质意义

中扬子西部下志留统灰岩、生物礁的分布与奥陶纪-志留纪之交"崇余运动"形成的NE向分布的古隆起相关,沿着鄂西利川-重庆石柱-南川一线,在早志留世小河坝期发育大型水下古隆起,小河坝中期(相当turriculatus带底部)发生区域性海侵,有利于钙质沉积,在鄂西宣恩高罗等古隆起的边缘发育生物礁。高罗生物礁是在陆棚相泥质条带灰岩礁基之上发育的一套以珊瑚和层孔虫为造架生物的生物礁,主要出露礁核的背风面沉积,造架生物间充填含大量藻类的泥岩,指示较深水、宁静的沉积环境。中扬子地区下志留统生物礁是除小河坝砂岩体之外重要的储层类型。     

DARWIN'S Coral Reef Research - a Review and Tribute

Abstract. In rememberance of the death of CHARLES DARWIN 100 years ago, a review is given on his coral reef research from the point of view of present knowledge. Although during DARWIN'S time no one was aware of the changing level of the glacial sea or of the important function of the symbiotic zooxanthellae in the life of hermatypic corals, his observations and considerations on the ecology of corals and on the formation of coral reefs are relevant to this day. But of course his ideas need new causal interpretations. The origin of the different reef types can no longer be explained by subsidence alone, but by different modes biologists and geologists described during the following century. To summarize all the many existing theories, the all enclosing "theory of compensation" is put forward here in honour of this great man.     

Tidally-induced clouds of suspended sediment connected to shallow-water coral reefs

The Bay of Banten, West Java, Indonesia represents a shallow coastal embayment harboring coral reefs subject to extremely turbid conditions. The sedimentary regime and flow structure of two contrasting coral reef islands in the embayment were investigated to identify the mechanisms responsible for mean and peak levels of suspended sediment concentration (SSC) around the reefs. Arrays of in situ calibrated optical backscatter (OBS) sensors were deployed across the reef slopes. Far field conditions were simultaneously monitored using an acoustic Doppler current profiler (ADCP) and a conductivity temperature and depth (CTD) probe, equipped with an OBS sensor. In addition, hydrographic surveys were conducted using the ADCP attached to a small fishing boat, navigating transects perpendicular to the reef islands. The direct influence of river plumes was found to be insignificant. Waves act only in the uppermost few meters of the reef slopes, where coral growth is most abundant and little sediment is available for resuspension. Tidal currents are the primary cause of high turbidity, which was inferred from peaks in the diurnal and semidiurnal frequency bands of SSC spectra, and the large depths where the turbidity variation sometimes initiates. The entrained sediment disperses upward across the reef slopes, which is likely due to a secondary current associated with bending of the flow along the curved, hydraulically rough reef slopes, in weakly stratified ambient waters. Changes in sediment availability, variable critical shear stresses for erosion and deposition, and the formation and evanescence of island wakes may explain the high variability of SSC at the reef slopes.     

Spatial variation in otolith chemistry of Lutjanus apodus at Turneffe Atoll, Belize

Lutjanus apodus (Schoolmaster) were collected from several mangroves and coral reefs at Turneffe Atoll, Belize, in order to investigate whether elemental concentrations from the otolith edge could be used as a means to identify the habitat (mangrove or coral reef) and site (9 mangrove sites and 6 reef sites) from which they were collected. Results of a two factor nested MANOVA (sites nested within habitat) indicated significant differences in elemental concentrations between habitats (i.e., mangrove versus reef) as well as among sites. When separate Linear Discriminant Function Analyses (LDFA) were used to assess whether the spatial variability in otolith chemistry was sufficient to differentiate individuals to their respective habitats or sites, the results indicated that fish were classified (jackknife procedure) with a moderate to poor degree of accuracy (i.e., on average, 67% and 40% of the individuals were correctly classified to the habitat and site from which they were collected, respectively). Using a partial Mantel test we did not find a significant correlation between the differences in otolith elemental concentrations between sites and the distance between sites, while controlling the effect of habitat type (mangrove or reef). This suggests that for mangrove and reef sites at Turneffe Atoll, Belize, the overlap in terms of L. apodus otolith elemental concentrations is too high for investigations of fish movement. Finally, by comparing previously published Haemulon flavolineatum otolith chemistry to that of L. apodus we assessed whether these species showed similar habitat and/or site specific patterns in their otolith chemistry. Although both species were collected from the same sites our results indicated little similarity in their elemental concentrations, thus suggesting that habitat and site elemental signatures are species specific.