Superposed folding in the Rockley district,Lachlan Fold Belt,New South Wales

Low grade metasediments and metavolcanics of the Hill End Synclinorial Zone within the Rockley district, NSW have experienced two phases of macroscopic folding (D1 and D2), both of which are post‐latest Silurian in age. No hiatus is evident between D1 and D2. D1 produced large Fi folds (λ/2 usually > 2 km) lacking mesoscopic elements and having variable axial trends. D2 was associated with the development of regional slaty cleavage (S2) and mesoscopic folds which are parasitic on plunging macroscopic F2 folds (λ/2=0.4–2 km). D2 strain is variable, being most intense in the north of the district where slaty cleavage and tight mesoscopic F2 folds are well developed, and weakest in the south where mesoscopic folds are absent or usually gentle and cleavage is often feebly developed even in mica‐rich rocks, which are stratigraphic equivalents to slates and schists in the north. The F1 fold mechanism may involve multiple folding, simultaneous folding in more than one direction, or complex buckling of layers of variable thickness. D1 and D2 are tentatively correlated with folding events elsewhere in the Hill End Synclinorial Zone.     

UKGrsHP: a UK high-resolution gauge–radar–satellite merged hourly precipitation analysis dataset

Climate Dynamics - There is an urgent need for high-quality and high-spatial-resolution hourly precipitation products around the globe, including the UK. Although hourly precipitation products...     

Structural style and fault kinematics of the Lower Eocene Rus Formation at Jabal Hafit area,Al Ain,United Arab Emirates (UAE)

The current contribution presents aspects of the structural style and fault kinematics of the Rus Formation that expose at Jabal Hafit, Al Ain, United Arab Emirates. Although the major structure of Jabal Hafit is an anticlinal fold, fractures (joints and faults) are the prominent structure of the study area. The fractures can be interpreted as the distributed effect of deep-seated basement fault reactivation or to be as reactivation of deep-seated basement faults. These fractures were created during two main tectonic stress regimes. The first is a WNW–ESE S _Hmax strike-slip stress regime, responsible for producing E–W to ESE–WNW joints and E–W dextral strike-slip and NNE–SSW reverse faults. This stress is interpreted to be post-Early Eocene in age and related to the second phase of thrusting in the Oman Mountains in the Miocene. The second stress regime is a NNE–SSW S _Hmax transtensional (strike-slip extensive) stress regime that was responsible for N–S to NNE–SSW striking joints and NE–SW sinistral strike-slip and N–S normal faults. This regime is interpreted to be post-Middle Eocene in age. This stress was the response to the collision of the Arabian–Eurasian Plates which began during the Late Eocene and continues to the present day.     

Paleolimnological comparison of algal changes in a clear-versus a brown-water lake over the last two centuries in the northeastern U.S.A

Journal of Paleolimnology - We reconstructed historical diatom and algal pigment records from a clear-water versus a brown-water lake in the northeastern U.S. to compare ecological responses to...     

The Mid-Atlantic Ridge at 37 and 45° N: some geophysical and petrological constraints

Summary. At present there is a strong conflict between, on the one hand, seismological and thermal models of the Mid-Atlantic Ridge, which indicate that no large crustal magma chamber can exist, and on the other hand petrological models many of which stress the importance of such a chamber. We review the available geophysical and petrological information from the FAMOUS area and 45° N in an attempt to resolve this conflict and demonstrate that a model (the infinite leek) can be constructed which satisfies all the available seismological, thermal, petrographic, major element and trace-element information from these two areas. This mode is as follows: mantle rising from depth begins to melt at about 60 km, and rises in equilibrium with its melt to about 15–25 km below the sea surface. At this level melt segregates and rises rapidly to the base of the crust. Magma injection above this takes place by a process of crack propagation, or by the development of a narrow vertical magma chamber, but no large crustal chamber is present. This model successfully explains the marked petrographic zonation of the floor of the median valley (Hekinian, Moore & Bryan).     

The Sha’it–Nugrus shear zone separating Central and South Eastern Deserts,Egypt: A post-arc collision low-angle normal ductile shear zone

The northerly dipping Sha’it–Nugrus shear zone (SNSZ) is the boundary separating the Central Eastern Desert from the South Eastern Desert of Egypt. The hangingwall of this shear zone is composed of low-grade metavolcanics and ophiolitic nappes of the Central Eastern Desert, while the footwall consists of South Eastern Desert high-grade metapsammitic gneisses (Migif-Hafafit gneissic complex). The SNSZ is about 700 m thick and represents the shear foliated lower parts of the hangingwall and upper parts of the footwall. A significant part of the SNSZ has been truncated by a later normal fault along Wadi Sha’it, however the SNSZ is well-preserved along Wadi Nugrus. Features of the SNSZ include shear-related schistosity (termed Ss), mylonite zones, sheared syn-kinematic granitoid intrusions, diverse metasomatism and metamorphic effects (higher T overprinting of hangingwall lithologies and retrogression of footwall lithologies). Shear-sense indicators clearly show top-to-N or NW displacement sense. SNSZ structures overprint arc collision related nappe structures (～680 Ma) and are therefore post-arc collision. SNSZ syn-kinematic intrusives have been dated at ～600 Ma. The SNSZ is deformed (regionally and locally folded and thrust dissected) during later NE–SW compressive tectonism. The SNSZ had an originally approximately E–W strike, low-angle N-dip and a normal shear sense, making this an example of a low-angle normal ductile shear (LANF) or detachment fault. The steep NE dip of Ss foliations and low-pitching slip lineations along Wadi Nugrus are due to NW–SE folding of the SNSZ, and do not indicate a sinistral strike-slip shear zone. The normal shear sense activity is responsible for juxtaposing the low-grade Central Eastern Desert lithologies against South Eastern Desert gneisses. A displacement of 15–30 km is estimated on the SNSZ, which is comparable to LANF displacements in the Basin and Range province of the western USA. Frictional resistance along this shear was probably reduced by high magmatic fluid pressure and hydrothermal fluid pressure. The vastness and diversity of the hydrothermal activity along this shear zone is a characteristic of other LANFs in the Eastern Desert, e.g. at Gabal El-Sibai, and may be Gabal Meatiq. The SNSZ formed during the Neoproterozoic extensional tectonic phase of Eastern Desert that began ～600 Ma, and followed arc collision and NW-ward ejection of nappes.     

Relative importance of dissolved and food pathways for lead contamination in shrimp

The relative importance of dissolved and food pathways and the influence of food type in the bioaccumulation and retention of lead in the shrimp Palaemonetes varians were examined using a radiotracer method. Shrimp were exposed to ²¹⁰Pb-labelled seawater or fed two types of ²¹⁰Pb-labelled food, viz. mussels or worms. The amount of radiotracer accumulated by shrimp was examined over a 7-day period, followed by a 1-month and a 7-day depuration period for the dissolved and food source, respectively. Steady state in the uptake was reached after 2 days exposure to dissolved lead, with a resultant estimated concentration factor of 98 ± 3. Transfer factors following ingestion of contaminated mussels and worms were lower than unity for both food types, with lead transfer from worms being significantly higher than that from mussels. Accumulation of dissolved Pb by shrimp was found to occur mainly through adsorption on the exoskeleton with a minor accumulation in the internal tissues probably resulting from the intake of seawater for osmoregulation. In contrast, lead taken up from contaminated food was readily absorbed and bound in the internal tissues of P. varians. Although the transfer of lead to P. varians through the ingestion of contaminated food was low (TF < 1%), it still represented 4 to 8% of the lead content in the prey which is a significant additional contribution of lead to the shrimp body burden. Independent of food type, following ingestion of contaminated food, approximately 23–27% of total lead accumulated in shrimp was located in the edible parts (e.g. muscle). Therefore, the food pathway is suggested to be a significant contributor to the lead transfer to humans through ingestion of contaminated shrimp. After exposure to contaminated food, lead loss kinetics were described by a two-component model, whereas Pb loss following direct uptake from seawater was best described by a three-component model. The additional compartment representing 64% of total Pb retained and characterized by a turnover < 10 min, corresponded to lead weakly adsorbed on the exoskeleton and incorporated in the hepatopancreas. Nevertheless, a significant fraction of lead accumulated from the dissolved (2%) and food (52–57%) pathways remained irreversibly retained in the tissues, suggesting that this organism could also serve as an effective long-term bioindicator of lead contamination in marine waters.     

Coastal seas as a context for science teaching: a lesson from Chesapeake Bay

Lessons that employ authentic environmental data can enhance the ability of students to understand fundamental science concepts. This differs from traditional "environmental education" in that school curricula need not set aside time for educators to teach only environmental topics. Rather, the "environment" is used to advance student learning in science and technology. The success of this approach depends on programs that encourage scientists to communicate more effectively with teachers at all education levels. The expanding diversity of research and monitoring activities on the world's marine waters constitutes an outstanding potential education resource. Many of these projects involve remote sensing with sophisticated instrumentation and employ Internet technology to compile measurements, interpret data using graphs and satellite imagery, and share the results among scientific colleagues and the general public alike. Unfortunately, these resources, which constitute a much shortened path between research findings and textbook presentation, are seldom interpreted for use by K-12 educators. We have developed an example that uses the Chesapeake Bay as a paradigm to demonstrate how such interpretation can assist educators in teaching important principles in physical oceanography and marine ecology. We present this example using PowerPoint to conduct a virtual tour of selected Internet sources. Our example begins with the conceptual "salt wedge" circulation model of Chesapeake Bay as a partially mixed estuary. Teachers have the opportunity to explore this model using salinity, temperature, and dissolved oxygen data taken from a research vessel platform during summer professional development programs. This source of authentic data, originally obtained by teachers themselves, clearly demonstrates the presence of a picnocline and deep-water anoxia. Our lesson plan proceeds to interpret these data using additional Internet-based resources at increasing scales of time and space. The "salt wedge," picnocline, and anoxia are examined using graphics derived from data taken by researchers using "ScanFish," a towed instrument that samples temperature, salinity, and dissolved oxygen at a resolution of only a few meters vertically and horizontally. The seasonal dynamics of these parameters at a given location are interpreted using biweekly monitoring data obtained as part of the state-federal Chesapeake Bay Program. The influence of annual variations in freshwater input is examined using stream flow data from US. Geological Survey gauging stations. Satellite remote sensing images from the TOPEX/Poseidon project are used to show how El Ni?o and La Ni?a events in the mid-Pacific affect the Chesapeake Bay system via rainfall on its watershed. Finally, the life cycle of the blue crab (Callinectes sapidus) is presented to show how an estuarine organism has adapted to this truly unique and dynamic coastal environment.     

Hydrocarbons and water in the Western Canada Sedimentary Basin — A tale of two fluids

Detailed petroleum system analysis allows the direction and extent of hydrocarbon flow to be assessed. In most parts of the Western Canada Sedimentary Basin, the major pulse of hydrocarbon generation and migration occurred as a result of the Laramide Orogeny in Late Cretaceous–Early Tertiary time. The distribution and chemistry of oils provide a detailed picture of fluid flow at this time with oil migration up to hundreds of kilometres observed. Hydrocarbon generation and migration mostly ceased once uplift of the basin commenced during Eocene time. As the basin evolved so did the hydrodynamic regime reflecting changes in topography, glaciation and other factors. This indicates possible problems with using present day hydrogeology to determine oil migration pathways although hydrogeology can help explain petroleum alteration.     

Water fluxes and their control on the terrestrial carbon balance: Results from a stable isotope study on the Clyde Watershed (Scotland)

The gradients between precipitation and runoff quantities as well as their water isotopes were used to establish a water balance in the Clyde River Basin (Scotland). This study serves as an example for a European extreme with poorly vegetated land cover and high annual rainfall and presents novel water stable isotope techniques to separate evaporation, interception and transpiration with annual averages of 0.029 km³ a⁻¹, 0.220 km³ a⁻¹ and 0.489 km³ a⁻¹, respectively. Transpiration was further used to determine CO₂ uptake of the entire basin and yielded an annual net primary production (NPP) of 352 × 10⁹ g C (Giga gram) or 185.2 g C m⁻². Compared to other temperate areas in the world, the Clyde Basin has only half the expected NPP. This lower value likely results from the type of vegetation cover, which consists mostly of grasslands. Subtracting the annual heterotrophic soil respiration flux (R_h) of 392 Gg (206.1 g C m⁻² a⁻¹) from the NPP yielded an annual Net Ecosystem Productivity (NEP) of −40 Gg C, thus showing the Clyde Watershed as a source of CO₂ to the atmosphere. Despite the unusual character of the Clyde Watershed, the study shows that areas with predominant grass and scrub vegetation still have transpirational water losses that by far exceed those of pure evaporation and interception. This infers that vegetation can influence the continental water balances on time scales of years to decades.