辽东半岛南部寒武系与奥陶系界线

笔者(1989)在辽东半岛南部复州湾和金县七顶山寒武系与奥陶系界线附近发现一层笔石,它们为:Airograptus furciferus,Staurograptus sp.,Dendrograptus sp.,并且建立了 Airograptus furciferus-Staurograptus 带,该带相当于华北的 Dictyonema flabelliforme-Staurograptus 带,相当于华南东南区的Staurograptus-Anisograptus 带,其层位相当于英国的特马豆克阶。由于该区寒武系顶部已建立了笔石带Dictyonema kelanense 带,因此,笔者将辽东半岛南部寒武系与奥陶系界线划在 Airograptus furciferus-Staurograptus 带与 Dictyonema kelanense 带之间。     

Particulate organic matter in the coastal and estuarine waters of Goa and its relationship with phytoplankton production

In the coastal and estuarine waters of Goa, particulate organic carbon (POC) varied from 0.52 to 2.51 mg l^?1 and from 0.28 to 5.24 mg l^?1 and particulate phosphorus (PP) varied from 0.71 to 5.18 μg l^?1 and from 0.78 to 20.34 μg l^?1, respectively. The mean values of chlorophyll and primary productivity were 1.94 mg m^?3 and 938.1 mg C m^?2 day^?1 in the coastal waters and 4.3 mg m^?3 and 636.5 mg C m^?1 day^?1 in the estuarine waters, respectively.$\text{POC}\text{chl}$ ratios were low in June and October even when POC values were quite high. The POC in surface waters was linearly correlated with the chlorophyll content. Also PP increased when chlorophyll and primary productivity remained high. The results suggest that the phytoplankton was sharply increasing and contributed to POC and PP content. The percentage of detritus calculated from the intercept values of chlorophyll on POC varied from 46 to 76% depending on season. Results indicate that the major portion of POC and PP during postmonsoon (October–January) is derived from phytoplankton production while the allochthonous matter predominate during monsoon (June–September).     

辽南早元古代花岗岩的变形温度及其构造意义

辽南早元古代辽河群中片麻状花岗岩的变形温度显示出645—690℃,550—610℃和485℃±三组温度值,表明花岗岩遭受了三幕构造变形。而区域构造解析亦表明辽河群在早元古时期经历了三幕构造变动。花岗岩的温度系列与区域变形序列具有一致性,排除了花岗岩晚期构造侵位的可能性。变形温度以550—610℃居多,意味着该幕构造形迹保存最好。第三幕变形变质作用相对较弱,仅局部出现485℃的温度值。     

Contribution of storms to groundwater recharge in the semi‐arid region of Karnataka,India

This paper describes the application of environmental isotopes and injected tracer techniques in estimating the contribution of storms as well as annual precipitation to groundwater recharge and its circulation, in the semi‐arid region of Bagepalli, Kolar district, Karnataka. Environmental isotopes ²H, ¹⁸O and ³H were used to study the effect of storms on the hydrological system, and an isotope balance was used to compute the contribution of a storm component to the groundwater. Some of the groundwater samples collected during the post‐storm periods were highly depleted in stable isotope content with higher deuterium excess relative to groundwater from the pre‐storm periods. Significant variation in deuterium excess in groundwater from the same area, collected in two different periods, indicates the different origin of air masses. The estimated recharge component of a storm event of 600 mm to the groundwater was found to be in the range of 117–165 mm. There was no significant variation in environmental tritium content of post‐storm and pre‐storm groundwater, indicating the fast circulation of groundwater in the system. After completion of the environmental isotope work, an injected radiotracer ³H technique was applied to estimate the direct recharge of total precipitation to the groundwater. The estimated recharge to the groundwater is 33 mm of the 550 mm annual precipitation during 1992. Copyright © 2003 John Wiley & Sons, Ltd.     

沉积物粒度分析在厦门市第四纪环境研究和地层划分对比中的应用

采用MS2000型激光粒度分析仪进行测试，利用计算机粒度分析软件对数据进行整理和计算，绘制出样品的频率曲线、概率累积曲线以及粒度众数位值曲线等图件并进行沉积环境分析。厦门地区第四纪环境演化经历了中更新世同安组(含泥中粗砂、含泥细中砂、砂为主)海积一冲积一更新统上部龙海组(含泥粗中砂、含泥细中砂、含泥粗砂、粗砂、细中砂、含细砾中粗砂、中细砂等)冲积一洪冲积一更新世上部东山组(砂、砂砾、含泥中粗砂、粗砂、泥质中细砂、细砂、中粗砂等)冲洪积及部分海积(粉砂、细粉砂、含碳质泥、粘土、淤泥质粘土、粉砂质粘土等)一全新世长乐组(粉砂，淤泥质粘土、粉砂质粘土、碳质粘土、含砂淤泥质粘土，粉砂质亚粘土、粉细砂亚粘土等)海湾沉积。在解释环境变化的同时，说明粒度变化曲线在一定程度上可以作为地层划分的依据之一，并以此对研究区地层进行了详细划分。     

宁远保安地区基性─超基性火山岩基本特征

本文论述了保安地区火山岩的地质、岩石、副矿物、岩石化学、微量元素、稀土元素、稳定同位素、火山岩相及火山机构等特征。并对其演化规律、形成机制与成矿作用的关系，作了初步探讨。     

The solubility of iron sulphides in synthetic and natural waters at ambient temperature

A critical evaluation of literature values for the solubility products, K _sp ^NBS = [Fe²⁺][HS^–] Fe²⁺ HS^– (H _NBS ⁺ )^–1, of various iron sulphide phases results in consensus values for the pKs of 2.95 ± 0.1 for amorphous ferrous sulphide, 3.6 ± 0.2 for mackinawite, 4.4 ± 0.1 for greigite, 5.1 ± 0.1 for pyrrhotite, 5.25 ± 0.2 for troilite and 16.4 ± 1.2 for pyrite.Where the analogous ion activity products have been measured in anoxic freshwaters in which there is evidence for the presence of solid phase FeS, the values lie within the range of 2.6–3.22, indicating that amorphous iron sulphide is the controlling phase. The single value for a groundwater of 2.65 (2.98 considering carbonate complexation) agrees. In seawater four values range between 3.85 to 4.2, indicating that mackinawite or greigite may be the controlling phase. The single low value of 2.94 is in a situation where particularly high fluxes of Fe (II) and S (–II) may result in the preferential precipitation of amorphous iron sulphide. Formation of framboidal pyrite in these sulphidic environments may occur in micro-niches and does not appear to influence bulk concentrations. Calculations show that the formation of Fe₂S₂ species probably accounts for very little of the iron or sulphide in most natural waters. Previously reported stability constants for the formation of Fe (HS)₂ and (Fe (HS)₃)^– are shown to be suspect, and these species are also thought to be negligible in natural waters. In completely anoxic pore waters polysulphides also have a negligible effect on speciation, but in tidal sediments they may reach appreciable concentrations and lead to the direct formation of pyrite. Concentrations of iron and sulphide in pore waters can be controlled by the more soluble iron sulphide phase. The change in the IAP with depth within the sediment may reflect ageing of the solid phase or a greater flux of Fe (II) and S (–II) nearer the sediment surface. This possible kinetic influence on the value of IAPs has implications for their use in geochemical studies involving phase formation.     

First seismic record for intra-arc strike-slip tectonics along the Liquiñe-Ofqui fault zone at the obliquely convergent plate margin of the southern Andes

A temporal seismic network recorded local seismicity along a 130 km long segment of the transpressional dextral strike-slip Liquiñe-Ofqui fault zone (LOFZ) in southern Chile. Seventy five shallow crustal events with magnitudes up to M_w 3.8 and depths shallower than 25 km were observed in an 11-month period mainly occurring in different clusters. Those clusters are spatially related to the LOFZ, to the volcanoes Chaitén, Michinmahuida and Corcovado, and to active faulting on secondary faults. Further activity along the LOFZ is indicated by individual events located in direct vicinity of the surface expression of the LOFZ. Focal mechanisms were calculated using deviatoric moment tensor inversion of body wave amplitude spectra which mostly yield strike-slip mechanisms indicating a NE–SW direction of the P-axis for the LOFZ at this latitude. The seismic activity reveals the present-day activity of the fault zone. The recent M_w 6.2 event near Puerto Aysén, Southern Chile at 45.4°S on April 21, 2007 shows that the LOFZ is also capable of producing large magnitude earthquakes and therefore imposing significant seismic hazard to this region.     

Focal mechanism inversion in the Giudicarie–Lessini seismotectonic region (Southern Alps, Italy): Insights on tectonic stress and strain

A set of 41 focal mechanisms (1989–2006) from P-wave first polarities is computed from relocated seismic events in the Giudicarie–Lessini region (Southern Alps). Estimated hypocentral depths vary from 3.1 to 20.8 km, for duration magnitudes (M_D) in the range 2.7–5.1. Stress and strain inversions are performed for two seismotectonic zones, namely G (Giudicarie) and L (Lessini). This subdivision is supported by geological evidence, seismicity distribution, and focal mechanism types. The available number of data (16 in G, 22 in L) does not make possible any further subdivisions. Seismotectonic zones G and L are undergoing different kinematic regimes: thrust with strike-slip component in G, and strike-slip in L. Principal stress and strain axes in each sub-region show similar orientations. The direction of maximum horizontal compressive stress is roughly perpendicular to the thrust fronts along the Giudicarie Belt in zone G, and compatible with right-lateral strike-slip reactivation of the faults belonging to the Schio-Vicenza system in zone L. On the whole, kinematic regimes and horizontal stress orientations show a good fit with other stress data from focal mechanisms and breakouts and with geodetic strain rate axes.     

Biostratigraphic and isotopic record of the Cenomanian–Turonian deposits in the Ohaba-Ponor section (SW Haţeg, Romania)

The middle Cenomanian–lower Turonian deposits of Ohaba-Ponor section (Southern Carpathians) were studied from biostratigraphic and isotopic points of view. Both the qualitative and semiquantitative nannofloral analyses, as well as the stable isotope (δ¹³C and δ¹⁸O) data support significant palaeoenvironmental changes in the investigated interval. Two δ¹³C positive excursions were recognized: (1) an excursion up to 1.8‰ (PDB) within the middle/late Cenomanian boundary; (2) an excursion up to 2.2‰ (PDB) in the Cenomanian/Turonian boundary interval. The oldest δ¹³C positive excursion recorded (placed within the Acanthoceras jukes-brownei/Eucalycoceras pentagonum Ammonite Zone boundary interval, and in the NC11 Calcareous Nannofossil Zone respectively) could be assigned to the middle Cenomanian Event II (MCEII). During the above-mentioned event, significant increase in abundance of Watznaueria barnesae, followed by successive blooms of Biscutum constans and Eprolithus floralis, were observed. The youngest δ¹³C positive excursion was identified in the Cenomanian/Turonian boundary interval (in the NC12 and lower part of the NC13 Calcareous Nannofossil Zones). Even the amplitude of this δ¹³C positive excursion is lower in the Ohaba-Ponor section, as generally reported, this may represent the regional record of the OAE2. The successive peaks of the nannofossils Biscutum constans, Zeugrhabdotus erectus and Eprolithus floralis indicate episodes of cooler surface water and high fertility, which preceded and lasted the Cenomanian/Turonian boundary event. Additionally, fluctuations of δ¹⁸O values between −2 and −6‰ suggest also cooler conditions within the Cenomanian/Turonian boundary interval.