The stratigraphy of the Permo-Triassic rocks of the Dorset and East Devon Coast World Heritage Site,U.K.

An almost complete late Permian and Triassic succession c. 1300 m thick is exposed in the cliffs between Exmouth and Lyme Regis in the Dorset and East Devon Coast World Heritage Site, U.K. All except the youngest part of the succession was deposited in terrestrial environments that include alluvial fans, aeolian sand dunes, braided rivers and playa-lakes. The succession of environments with time not only reflects the denudation of the Variscan mountains that lay to the west and south in the Cornubian and Armorican massifs, but also responses to periods of tectonic uplift and subsidence, and to long- and short-term climatic and associated biotic changes. Notwithstanding the almost continuous, readily accessible exposures in the cliffs and intertidal areas, few of the formations have yielded any age-diagnostic fossils with the result that much of the succession cannot be dated with certainty. The Permo-Triassic boundary has been placed in the lower part of the succession on the basis of magnetostratigraphy and the same method has been used to quantify some of the stage boundaries and the principal tectonic breaks in the succession.     

Cenozoic basin evolution of the Central Patagonian Andes: Evidence from geochronology,stratigraphy, and geochemistry

The Central Patagonian Andes is a particular segment of the Andean Cordillera that has been subjected to the subduction of two spreading ridges during Eocene and Neogene times. In order to understand the Cenozoic geologic evolution of the Central Patagonian Andes, we carried out geochronologic(U-Pb and⁴⁰Ar/³⁹Ar), provenance, stratigraphic, sedimentologic, and geochemical studies on the sedimentary and volcanic Cenozoic deposits that crop out in the Meseta Guadal and Chile Chico areas(～47°S). Our data indicate the presence of a nearly complete Cenozoic record, which refutes previous interpretations of a hiatus during the middle Eocene-late Oligocene in the Central Patagonian Andes. Our study suggests that the fluvial strata of the Ligorio Marquez Formation and the flood basalts of the Basaltos Inferiores de la Meseta Chile Chico Formation were deposited in an extensional setting related to the subduction of the Aluk-Farallon spreading ridge during the late Paleocene-Eocene. Geochemical data on volcanic rocks interbedded with fluvial strata of the San Jose Formation suggest that this unit was deposited in an extensional setting during the middle Eocene to late Oligocene. Progressive crustal thinning allowed the transgression of marine waters of Atlantic origin and deposition of the upper Oligocene-lower Miocene Guadal Formation. The fluvial synorogenic strata of the Santa Cruz Formation were deposited as a consequence of an important phase of compressive deformation and Andean uplift during the early-middle Miocene. Finally, alkali flood basalts of the late middle to late Miocene Basaltos Superiores de la Meseta Chile Chico Formation were extruded in the area in response to the suduction of the Chile Ridge under an extensional regime. Our studies indicate that the tectonic evolution of the Central Patagonian Andes is similar to that of the North Patagonian Andes and appears to differ from that of the Southern Patagonian Andes, which is thought to have been the subject of continuous compressive deformation since the late Early Cretaceous.     

Modified NLPM-ANN model and its application

The non-linear perturbation model based on artificial neural network (NLPM-ANN) takes advantage of the consideration of seasonal information by the linear perturbation model (LPM) and the notable non-linear simulation capability of artificial neural network (ANN). However, this model does not take account of antecedent catchment wetness that may effect the simulation and forecasting accuracy. A modified NLPM-ANN model is proposed and developed to take the consideration of antecedent catchment wetness. The output perturbing terms of the response function in the simple linear model (SLM) in an auxiliary component are taken as inputs of ANN to represent catchment wetness. The simulated total runoff is obtained by integrating the outputs of ANN with that of the seasonal model. The rainfall–runoff data of eight catchments were selected and used to compare the modified NLPM-ANN with the NLPM-ANN models. Results show that the modified NLPM-ANN is significantly superior to the NLPM-ANN, and the model component efficiency index values are 16.82% and 16.74% over the NLPM-ANN during calibration and verification periods, respectively.     

单井多层位水温微动态初步研究

基于海口ZK26井的水温观测环境以及近10年的观测资料, 分析-153 m、 -336 m、 -510 m水温的频谱特征, 探讨单井各层位水温丰富的微动态信息, 对比观测结果表明: 海口ZK26深井不同层位的水温表现出不同的微动态特征, 与观测层位的频谱特征、 水文地质条件、 水力性质等有着密切的联系。 -153 m位于含水层负梯度区, 主要处于低频段, 而且高低频噪声较弱, 信噪比较高, 可以表现出较清晰的微动态特征, 如水温海潮效应、 震前异常、 同震效应以及震后效应; -336 m与-510 m水温位于非含水层, 主要处于高频段, 并且背景噪声较强, 水温微动态信息较弱。     

Upper Neoproterozoic–Lower Cambrian sedimentary successions in the Central Iberian Zone (Spain): sequence stratigraphy, petrology and chemostratigraphy. Implications for other European zones

2 O₃, TiO₂, Zr, and Nb abundances in shales from all the units, strongly suggest a gradual compositional change within this sedimentary succession. Together with the petrological data, the chemical results do not reveal any obvious coeval volcanic contribution to the sediments. On the basis of the chemical data, a comparison is made with other European zones containing detrital sediments composed of reworked crustal components. Received: 4 January 1999 / Accepted: 1 December 1999     

草型湖泊与藻型湖泊大型底栖动物生产力的比较

较系统地比较了典型草型湖泊(扁担塘)与典型藻型湖泊(后湖)底栖动物优势种类、主要类群及整个群落的周年生产量.结果表明,典型草型湖泊扁担塘底栖动物群落的周年生产量(湿重或带壳湿重)38.926g/穴m2·a雪比典型藻型湖泊后湖47.505g/穴m2·a雪为低.各类群具体情况为,后湖(藻型湖泊)的营养水平较高,更适合苏氏尾鳃蚓等耐污性种类的生长,因此寡毛类生产量较扁担塘的为高;藻型湖泊比草型湖泊更适合铜锈环棱螺等腐生螺类的生长,螺类的生产量也比草型湖泊略高;藻型湖泊摇蚊的生产量较高,原因在于藻型湖泊更适合具有较多耐污种类的摇蚊生长.但从大型底栖动物群落生产量的组成看,摇蚊、软体动物、寡毛类等三大类群所占份额相对较稳定,分别为14%-15%、77%-79%、7%-8%.     

Arundian (Dinantian) carbonate mudbanks in north-west Ireland

Arundian mudbank complexes at Pollower and Carrickbaun in north-west Ireland are described in detail. The two bank complexes developed on different fault blocks controlled and separated by the Curlew Mountain Fault system which was active during the Dinantian. The two mudbank complexes are composed predominantly of lime mudstone and wackestone textures with abundant peloids and intraclasts. Stromatactoid cavity systems in the banks are extensive and have multiple generations of geopetal internal sediment and radiaxial and bladed cryptofibrous calcite cements. These mudbanks are comparable with earlier Courceyan-Chadian deep water Waulsortian mudbanks which accumulated on carbonate ramps. Components in the Pollower bank most closely resemble those in subphotic Phase C Waulsortian banks, whereas the Carrickbaun mudbank, which possesses dasycladacean algae, intraclasts and micritized fragmented bioclasts, indicates a much shallower environment of in situ carbonate mud accumulation, comparable to the photic Phase D assemblages of Waulsortian banks. The difference in depositional setting is also reflected by their respective enclosing lithologies. The Pollower bank is surrounded by deep water black argillaceous wackestones and shales, whereas at Carrickbaun shallower water crinoidal packstones and grainstones are developed on the flanks and bank top. The Arundian mudbank complexes have many similarities with the Asbian mudbanks of north-west Ireland and as such appear to represent an important ‘stratigraphic’ link in the continuum of deep water mudbanks between the two main periods of development in the early Dinantian (Waulsortian) and late Dinantian (Asbian/Brigantian).     

比较沉积学概念体系的厘定与重构

近代沉积学的诸多进步都是由比较沉积学推动的,它对沉积学的发展有重要意义。目前,其被广泛应用于相模式的推断和沉积相带、储层及其非均质性的预测。比较沉积学是利用比较对象所选变量的时空展布建立模型,再利用模型推断预测被比较对象因变量时空展布的沉积学分支学科。它是根据比较沉积学类比原则,在自生旋回、他生旋回识别的基础上开展的或然性推理。完整的比较沉积学工作过程必然存在2个步骤——比较建模和推断预测。其研究方法包括相模式分析法、几何形态分析法、沉积物载荷分散体系分析法和模拟重构法4种,这些方法多与层序地层学方法联合使用。本文根据比较沉积学的原理和方法综合分析了历年来的典型成果。未来比较沉积学将开展更多与边界条件有关的研究、多尺度统一解释的研究,进一步加强量化,提高预测精度的研究。     

小黄鱼(Larimichthys polyactis)线粒体基因组结构与特征

采用长片段扩增策略,获得鲈形目石首鱼科黄鱼属小黄鱼的线粒体基因组全序列。组装分析结果表明,其长度为16470bp,H链碱基组成呈明显反G偏倚,G含量仅为16%。13个蛋白质基因起始密码子均为ATG。COI基因的终止密码子为AGA,ND1和ND3基因为TAG,COII、ND4和Cytb基因为不完全终止密码子T,其余7个基因都是完整的TAA。在小黄鱼mtDNA中发现2个特殊发夹结构,一个是轻链复制起始区(OL)的发夹环,位于tRNA簇,环区T含量仅为9%,而G含量达45%,这与哺乳动物和爪蟾该区域富含T有所不同。另一个假定发夹结构位于ATP6基因末端,这种二级结构可能与准确转录有关。该mtDNA控制区长度为799bp,5′端含有9个连续TA串联重复和2个5′-ATGTA---TACAT-3′重复,与已报道的鱼类扩展终止相关序列模式恰恰相反;中央控制区仅识别出CSB-E结构;保守序列区含有CSB-1,2,3,其中CSB-2具有高度保守性。对小黄鱼和大黄鱼的mtDNA比较进化研究,根据分子钟假说,估计二者线粒体基因组的进化分歧时间为4.8百万年前。     

南海夏季风强弱年环流形势与热带对流特点对比分析

利用NCEP/NCAR(美国国家环境预报中心/国家大气研究中心)再分析资料,对南海强夏季风年和弱夏季风年进行合成分析,结果表明,无论是在夏季风爆发前的1月份或是夏季风盛行的7月份,强弱夏季风年的平均经圈环流和平均纬圈环流都有明显差异。在强夏季风年,1月份的哈特莱环流、7月份的瓦克环流和季风经圈环流都比弱夏季风年同期的明显。强夏季风年的西太平洋副热带高压比弱夏季风年明显偏弱。利用OLR资料分析强夏季风年(1981年)和弱夏季风年(1983)4～9月份赤道东印度洋和南海对流活动的季节内振荡,发现在南海强夏季风年,季节内振荡的次数偏少而强度偏强,在弱夏季风年,季节内振荡的次数偏多而强度偏弱。相比之下,在南海强夏季风年,赤道东印度洋的季节内振荡比南海的更具典型性。