Upper Eocene ejecta of the New Jersey continental margin reveal dynamics of Chesapeake Bay impact

Evidence for the Chesapeake Bay Crater as the source for New Jersey continental margin ejecta is provided by fine-grained tektites and coarse-grained unmelted ejecta. The Upper Eocene ejecta deposit, now demonstrated to be part of the North American strewn field, occurs on the New Jersey continental margin at Ocean Drilling Program (ODP) Sites 904 and 903. The mineralogy, major oxide composition of the ejecta materials, and biostratigraphic age of the enclosing sediments link the origin of these ejecta to the recently recognized Chesapeake Bay impact crater, located only 330 km away. Sediments associated with the ejecta provide information about the dynamics of impact events. The 35-cm-thick ejecta-bearing layer can be subdivided into three subunits that indicate a sequence of events. Bottom subunit III documents sediment failure and deposition of gravel-sized fragments, middle subunit II records deposition of abundant sand-sized ejecta by gravity settling, and upper subunit I contains a 12-cm-thick sedimentary deposit containing rare silt-sized tektites and evidence of waning currents. These events are interpreted by linking sediment deposition to seismic ground motion and subsequent tsunami waves triggered by both the Chesapeake Bay impact and slope failures.     

Neolithic wooden trackways and bog hydrology

Five wooden trackways in raised bogs located along a precipitation gradient in Northwest Europe (Ireland, England, The Netherlands and Germany), and all dated toc. 2600 cal.BC, show differences in building method related to variable hydrological conditions in the local bog surfaces. Differences in the bearing strength of the highly humified hummock-hollow surfaces can be largely attributed to differences in the climatically related water content of the peat. Water balance studies, based on current climatic data and using the concept of system-linked discharge, can explain the hydrological differences between the ombrotrophic bogs established by archaeological excavations of the wooden trackways. Active peat growth at the time of construction and building methods used indicate mean annual precipitation values similar to present reflecting the modern rainfall gradient.This publication is the fourth paper in a series of papers presented at the session on Past Climatic Change and the Development of Peatlands at the ASLO and SWS Meetings in Edmonton, Canada, May 30–June 3, 1993. Dr P. Kuhry and Dr S. C. Zoltai are serving as Guest Editors.     

Our astrochemical heritage

Our Sun and planetary system were born about 4.5 billion years ago. How did this happen, and what is the nature of our heritage from these early times? This review tries to address these questions from an astrochemical point of view. On the one hand, we have some crucial information from meteorites, comets and other small bodies of the Solar System. On the other hand, we have the results of studies on the formation process of Sun-like stars in our Galaxy. These results tell us that Sun-like stars form in dense regions of molecular clouds and that three major steps are involved before the planet-formation period. They are represented by the prestellar core, protostellar envelope and protoplanetary disk phases. Simultaneously with the evolution from one phase to the other, the chemical composition gains increasing complexity. In this review, we first present the information on the chemical composition of meteorites, comets and other small bodies of the Solar System, which is potentially linked to the first phases of the Solar System??s formation. Then we describe the observed chemical composition in the prestellar core, protostellar envelope and protoplanetary-disk phases, including the processes that lead to them. Finally, we draw together pieces from the different objects and phases to understand whether and how much we inherited chemically from the time of the Sun??s birth.     

Effects of high pressure,hot water shore cleaning after oil spills on shore ecosystems in the Northern Baltic proper

The use of high pressure, hot water hosing techniques in oil spill clean-up operations on rocky and stony-gravelly shores drastically reduces the shore vegetation and macrofauna. The negative effects are more substantial than on oiled shores cleaned by raking and scraping. After one year the hot water cleaned shores were not restored completely.On rocky shores the high pressure, hot water technique is very efficient in terms of freeing the rocks from oil. However, due to its detrimental effects on shore organisms this type of oil spill clean-up operation can only be recommended for bird or wildlife protection areas. The cleanup method is inefficient on stony-gravelly shores due to penetration of oil into the ground and sediment and direct killing of shore organisms. The method should be avoided on these types of shores.     

Water quality management in Singapore: the role of institutions,laws and regulations

Abstract

The paper analyses the legal and regulatory instruments for water quality management that have been set in place in Singapore for control of water pollution, and their evolution since the time of independence in 1965. The role of institutions in the strict implementation of the laws and regulations is also discussed, with special emphasis on the efficient inter-institutional coordination machinery that has made it possible. The analyses show that overall long-term planning and policy-making and a strong political will have been instrumental to give all aspects of water management high priority in the national agenda, thus directly supporting urban, industrial and commercial growth.

Editor Z.W. Kundzewicz     

Clues for the origin of the fundamental metallicity relations – I. The hierarchical building up of the structure

We analyse the evolutionary history of galaxies formed in a hierarchical scenario consistent with the concordance Lambda cold dark matter (ΛCDM) model focusing on the study of the relation between their chemical and dynamical properties. Our simulations consistently describe the formation of the structure and its chemical enrichment within a cosmological context. Our results indicate that the luminosity–metallicity and the stellar mass–metallicity (LZR and MZR) relations are naturally generated in a hierarchical scenario. Both relations are found to evolve with redshift. In the case of the MZR, the estimated evolution is weaker than that deduced from observational works by approximately 0.10 dex. We also determine a characteristic stellar mass, M _c≈ 3 × 10¹⁰ M_⊙, which segregates the simulated galaxy population into two distinctive groups and which remains unchanged since z ∼ 3, with a very weak evolution of its metallicity content. The value and role played by M _c is consistent with the characteristic mass estimated from the SDSS galaxy survey by Kauffmann et al. Our findings suggest that systems with stellar masses smaller than M _c are responsible for the evolution of this relation at least from z ≈ 3. Larger systems are stellar dominated and have formed more than 50 per cent of their stars at   z ≥ 2  , showing very weak evolution since this epoch. We also found bimodal metallicity and age distributions from z ∼ 3, which reflects the existence of two different galaxy populations. Although SN feedback may affect the properties of galaxies and help to shape the MZR, it is unlikely that it will significantly modify M _c since, from   z = 3  this stellar mass is found in systems with circular velocities larger than 100 km s⁻¹.     

U�CPb isotopic ages and Hf isotope composition of zircons in Variscan gabbros from central Spain: evidence of variable crustal contamination

Ion microprobe U?CPb analyses of zircons from three gabbroic intrusions from the Spanish Central System (SCS) (Talavera, La Solanilla and Navahermosa) yield Variscan ages (300 to 305?Ma) in agreement with recent studies. Only two zircon crystals from La Solanilla massif gave slightly discordant Paleoproterozoic ages (1,848 and 2,010?Ma). Hf isotope data show a relatively large variation with the juvenile end-members showing ?Hf_i values as high as +3.6 to +6.9 and +1.5 to +2.9 in the Navahermosa and Talavera gabbros, respectively. These positive ?Hf_i values up to +6.9 might represent the composition of the subcontinental mantle which generates these SCS gabbros. This ?Hf_i range is clearly below depleted mantle values suggesting the involvement of enriched mantle components on the origin of these Variscan gabbros, and is consistent with previous whole-rock studies. The presence of zircons with negative ?Hf_i values suggest variable, but significant, crustal contamination of the gabbros, mainly by mixing with coeval granite magmas. Inherited Paleoproterozoic zircons of La Solanilla gabbros have similar trace element composition (e.g. Th/U ratios), but more evolved Hf-isotope signatures than associated Variscan zircons. Similar inherited ages have been recorded in zircons from coeval Variscan granitoids from the Central Iberian Zone. Granitic rocks have Nd model ages (T_DM) predominantly in the range of 1.4 to 1.6?Ga, suggesting a juvenile addition during the Proterozoic. However, Hf crustal model ages of xenocrystic Proterozoic zircons in La Solanilla gabbro indicate the presence of reworked Archean protoliths (T_DM2 model ages of 3.0 to 3.2?Ga) incorporated into the hybridized mafic magma.     

Conflation of OpenStreetMap and Mobile Sports Tracking Data for Automatic Bicycle Routing

This article investigates how workout trajectories from a mobile sports tracking application can be used to provide automatic route suggestions for bicyclists. We apply a Hidden Markov Model (HMM)‐based method for matching cycling tracks to a “bicycle network” extracted from crowdsourced OpenStreetMap (OSM) data, and evaluate its effective differences in terms of optimal routing compared with a simple geometric point‐to‐curve method. OSM has quickly established itself as a popular resource for bicycle routing; however, its high‐level of detail presents challenges for its applicability to popularity‐based routing. We propose a solution where bikeways are prioritized in map‐matching, achieving good performance; the HMM‐based method matched correctly on average 94% of the route length. In addition, we show that the extremely biased nature of the trajectory dataset, which is typical of volunteered user‐generated data, can be of high importance in terms of popularity‐based routing. Most computed routes diverged depending on whether the number of users or number of tracks was used as an indicator of popularity, which may imply varying preferences among different types of cyclists. Revising the number of tracks by diversity of users to surmount local biases in the data had a more limited effect on routing.