Petrogenesis of the Greenhills Complex,Southland, New Zealand: magmatic differentiation and cumulate formation at the roots of a Permian island-arc volcano

A Permian (~265 Ma) intrusive complex which formed as a magmatic feeder reservoir to an immature island-arc volcano is fortuitously exposed in southern New Zealand. Known as the Greenhills Complex, this intrusion was emplaced at shallow crustal levels and consists of two layered bodies which were later intruded by a variety of dykes. Cumulates, which include dunite, olivine clinopyroxenite, olivine gabbro, and hornblende gabbro-norite, are related products of parent-magma fractionation. Both primary (magmatic) and secondary platinum-group minerals occur within dunite at one locality. Using the composition of cumulus minerals, mafic dykes and melt inclusions, we have determined that the parent magmas of the complex were hydrous, low-K island-arc tholeiites of ankaramitic affinities. Progressive magmatic differentiation of this parent magma generated fractionated melt of high-alumina basalt composition which is now preserved only as dykes which cut the Complex. Field evidence and cumulus mineral profiles reveal that the magma chambers experienced turbulent magmatic conditions during cumulate-rock formation. Recharge of the chambers by primitive magma is likely to have coincided with eruption of residual melt at the surface. Similar processes are inferred to account for volcanic-rock compositions in other parts of this arc terrane and in modern island-arc systems.     

Middle Paleozoic paleomagnetism of east Kazakhstan: post-Middle Devonian rotations in a large-scale orocline in the central Ural–Mongol belt

In order to test different hypotheses concerning the Paleozoic evolution of the Ural–Mongol belt (UMB) and the amalgamation of Eurasia, we studied Middle Devonian basalts from two localities (11 sites) and Lower Silurian volcanics, redbeds, and intra-formational conglomerates from three localities (20 sites) in the Chingiz Range of East Kazakhstan. The Devonian rocks prove to be heavily overprinted in the late Paleozoic, and a high-temperature, presumably primary, southerly, and down component is isolated at only four sites from a homoclinal section. Most Silurian redbeds are found to be remagnetized in the late Paleozoic; in contrast, a bipolar near-horizontal remanence, isolated from Silurian volcanics, is most probably primary as indicated by positive tilt and conglomerate tests. Analysis of paleomagnetic data from the Chingiz Range shows that southward-pointing directions in Ordovician, Silurian, and Devonian rocks are of normal polarity and hence indicate large-scale rotations after the Middle Devonian. The Chingiz paleomagnetic directions can be compared with Paleozoic data from the North Tien Shan and with the horseshoe-shaped distribution of subduction-related volcanic complexes in Kazakhstan. Both paleomagnetic and geological data support the idea that today's strongly curved volcanic belts of Kazakhstan are an orocline, deformed mostly before mid-Permian time. Despite the determination of nearly a dozen new Paleozoic paleopoles in this study and other recent publications by our team, significant temporal and spatial gaps remain in our knowledge of the paleomagnetic directions during the middle and late Paleozoic. However, the paleomagnetic results from the Chingiz Range and the North Tien Shan indicate that these areas show generally coherent motions with Siberia and Baltica, respectively.     

The Cretaceous and younger thermal history of the KTB site (Germany): apatite fission-track data from the Vorbohrung

A detailed fission-track analysis was carried out on 41 apatite samples from the 4001-m-deep pilot hole of the German Continental Deep Drilling Program (KTB). The investigations include dating by the population method and length measurements of horizontal confined tracks. Age and length information indicate that all samples above the present-day partial annealing zone cooled from temperatures above 120?°C in the Cretaceous. The top two kilometres of the profile show less variation of age with depth than was expected. Modelling of the profile indicates that the distribution of fission track ages with depth requires that the profile was disturbed during or after cooling through the partial annealing zone. Modelling of individual samples reveals that at least the upper 2?km experienced reverse faulting, effectively thickening the upper part of the rock column by up to 1000?m in the Tertiary. A present-day partial annealing zone for apatite was observed between 2000 and 4000?m (～60–110?°C). This confirms earlier in situ observations of the position of the partial annealing zone.     

Mechanical aspects of sedimentary basin formation: development of integrated models for lithospheric and surface processes

Different assumptions for the thermo-mechanical properties of the lithosphere strongly affect predictions inferred from quantitative sedimentary basin modeling. Examples from various basins, selected as natural laboratories, illustrate the importance of incorporating a finite strength of the extending lithosphere in forward stratigraphic modeling of large-scale basin stratigraphy. Current models can effectively couple erosion at uplifted rift shoulders of extensional basins with the basin fill architecture of the subsiding basin compartments. Modeling of the synrift strata integrates spatial scales characteristic for subbasins, such as the Oseberg field in the North Sea, with large-scale lithospheric properties characterizing the bulk strength of extending lithosphere. Modeling of compressional basins in foreland fold-and-thrust-belt settings can effectively link lithospheric flexure with surface processes. Scales pertinent to short-term spatial and temporal variations in basin fill and basin deformation can now be addressed, allowing the quantitative investigation of consequences of different modes of thrusting for basin fill geometry and facies characteristics.     

Measured and modeled effects of benthic algae on eutrophication in Indian River-Rehoboth Bay, Delaware

A combination of field studies and mathematical modeling was used to examine the role of subtidal benthic algae in the eutrophication processes in two shallow estuarine systems. Field measurements indicated uptake by benthic algae retained ammonium and phosphate in the sediments when light at the sediment surface exceeded ≈150 μE m² s^?1. The measurements were used to calibrate a newly developed model of benthic algal activity. The benthic algal model was coupled with a hydrodynamic model, a eutrophication model, and a sediment diagenesis model. In the simulated ecosystem, benthic algae had a major influence in the intra-annual cycling of nitrogen and phosphorus. When nutrients were abundant in the water column (late winter and spring) they were transferred to the sediments through algal activity. Diagenesis released these nutrients to the water column in summer when nutrients were scarce. As a result of the nutrient transfer, annual primary production in the water column, in the presence of benthic algae, exceeded production in the absence of the algae.     

Water-quality trends in White Rock Creek Basin from 1912-1994 identified using sediment cores from White Rock Lake reservoir, Dallas, Texas

Historical trends in selected water-quality variables from 1912 to 1994 in White Rock Creek Basin were identified by dated sediment cores from White Rock Lake. White Rock Lake is a 4.4-km² reservoir filled in 1912 and located on the north side of Dallas, Texas, with a drainage area of 259 km². Agriculture dominated land use in White Rock Creek Basin before about 1950. By 1990, 72% of the basin was urban. Sediment cores were dated using cesium-137 and core lithology. Major element concentrations changed, and sedimentation rates and percentage of clay-sized particles in sediments decreased beginning in about 1952 in response to the change in land use. Lead concentrations, normalized with respect to aluminum, were six times larger in sediment deposited in about 1978 than in pre-1952 sediment. Following the introduction of unleaded gasoline in the 1970s, normalized lead concentrations in sediment declined and stabilized at about two and one-half times the pre-1952 level. Normalized zinc and arsenic concentrations increased 66 and 76%, respectively, from before 1952 to 1994. No organochlorine compounds were detected in sediments deposited prior to about 1940. Concentrations of polychlorinated biphenyls (PCB) and DDE (a metabolite of DDT) increased rapidly beginning in the 1940s and peaked in the 1960s at 21 and 20 µg kg^-1, respectively, which is coincident with their peak use in the United States. Concentrations of both declined about an order of magnitude from the 1960s to the 1990s to 3.0 and 2.0 µg kg^-1, respectively. Chlordane and dieldrin concentrations increased during the 1970s and 1980s. The largest chlordane concentration was 8.0 µg kg^-1 and occurred in a sediment sample deposited in about 1990. The largest dieldrin concentration was 0.7 µg kg^-1 and occurred in the most recent sample deposited in the early 1990s. Agricultural use of chlordane and dieldrin was restricted in the 1970s; however, both were used as termiticides, and urban use of chlordane continued at least until 1990. Recent use of dieldrin and aldrin, which degrades to dieldrin, has not been reported; however, increasing trends in dieldrin since the 1970s suggest recent urban use could have occurred.     

Remote sensing techniques for landslide studies and hazard zonation in Europe

An inventory is presented of researches concerning the use of remote sensing for landslide studies and hazard zonation as mainly carried out in the countries belonging to the European Community. An overview is given of the applicability of remote sensing in the following phases of landslide studies:

1. (1) Detection and classification of landslides. Special emphasis is given to the types of imagery required at different scales of analysis.

2. (2) Monitoring the activity of existing landslides using G.P.S., photogrammetrical techniques and radar interferometry.

3. (3) Analysis and prediction in space and time of slope failures. The different factors required in a landslide hazard study are evaluated, and the optimum remote sensing imagery for obtaining each of these factors is indicated.

Examples are given of research work carried out in these three phases from EC countries. Finally an evaluation is given of the aspects of uncertainty associated with the use of remote sensing data, and conclusions are given as to the incorporation of remote sensing techniques within the overall framework of techniques.     

Palaeoecology and Archaeology of the Kärlich–Seeufer Open-Air Site (Middle Pleistocene) in the Central Rhineland, Germany

The Kärlich–Seeufer archaeological site in Germany's central Rhineland was excavated between 1980 and 1992. The site provides evidence for hominid activity during a Middle Pleistocene interglaciation known up to now only from the Kärlich clay pit and therefore defined as the Kärlich Interglaciation, which is considered to be post-Cromer IV and pre-Holstein (sensu stricto) in age. The site is characterized by Acheulean artifacts, a fauna dominated byElephas (Palaeoloxodon) antiquus,and a unique and outstanding preservation of wooden and other palaeobotanical remains. Assuming all finds are associated, the site previously was interpreted as an elephant hunting camp with a wooden structure, together with wood and bone implements preservedin situ.Recent analysis of the same features has shown that the site can also be interpreted as a reworked archaeological sample. Hominid occupation occurred in the vicinity of a small lake with prevailing meso-oligotrophic conditions. Expanding boreal forests and fen vegetation characterized the landscape.