GG Tau: the ringworld and beyond

In binary stellar systems, exoplanet searches have revealed planetary mass companions orbiting both in circumstellar and in circumbinary orbits. Modelling studies suggest increased dynamical complexity around the young stars that form such systems. Circumstellar and circumbinary disks likely exhibit different physical conditions for planet formation, which also depends on the stellar separation. Although binaries and higher order multiple stars are relatively common in nearby star-forming regions, surprisingly few systems with circumbinary distributions of proto-planetary material have been found. With its spectacular ring of dust and gas encircling the central triple star, one such system, GG Tau A, has become a unique laboratory for investigating the physics of circumsystem gas and dust evolution. We review here its physical properties.     

Evolution of depositional settings in the Torrey area during the Smithian (Early Triassic,Utah, USA) and their significance for the biotic recovery

This work focuses on well‐exposed Lower Triassic sedimentary rocks in the area of Torrey (south‐central Utah, USA). The studied Smithian 8 deposits record a large‐scale third‐order sea‐level cycle, which permits a detailed reconstruction of the evolution of depositional settings. During the middle Smithian, peritidal microbial limestones associated with a rather low‐diversity benthic fauna were deposited seaward of the tidal flat siliciclastic red beds. Associated with siliceous sponges, microbial limestones formed small m‐scale patch reefs. During the late middle to late Smithian interval, the sedimentary system is characterized by tidal flat dolostones of an interior platform, ooid‐bioclastic deposits of a tide‐dominated shoal complex, and mid‐shelf bioclastic limestones. Microbial deposits, corresponding to sparse stromatolites formed in the interior platform, are contemporaneous with a well‐diversified marine fauna living in a seaward shoal complex and mid‐shelf area. The nature and distribution of these Smithian microbial deposits are not related to any particular deleterious environmental condition, highlighting that observed patterns of biotic recovery after the end‐Permian mass extinction were directly influenced by depositional settings. Facies evolution and stratal stacking patterns allow us to identify large, medium and small‐scale, as well as elementary depositional sequences. Large‐ and medium‐scale sequences are consistent with sea‐level changes, whereas small‐scale and elementary sequences are better explained by autocyclic processes. Copyright © 2015 John Wiley & Sons, Ltd.     

The difficult combination of renting and building a house in urban Ghana: analysing the perception of low and middle income earners in Accra

This study examines the experiences of low and middle income earners in urban Ghana in combining renting and self-building a house with their meagre income. Using a case study of 3 building sites in Accra, this study employs semi-structured interview guide to gather qualitative data from fifty respondents. The conclusion of this study is that improving housing career amidst other competing responsibilities in the life course pathways imposes stress and huge financial burden on households in a manner that they are compelled to forgo or cut down on non-housing consumption such as clothing, up-keep of in-laws, marriage, higher educational qualification and cars among others. This study recommends a revisit of the discussion on the enforcement of the provisions of the Rent Act, 1963 and consideration of the practice of rent deposit and monthly rent. Affordable housing finance options should be a priority of African governments and their development partners.     

Is the connectivity function a good indicator of soil infiltrability distribution and runoff flow dimension?

Among the studies on runoff connectivity of soils with heterogeneous properties, the need to understand the relationships between soil heterogeneity and the associated runoff organization and amount is frequently mentioned. In this study, we simulate the stationary runoff–runon process on bi‐dimensional (2D) flat slopes for five infiltrability distributions, one of them correlated, as a function of rainfall intensity and flow dimension. We define flow dimension by 1 + ε, where ε is the outflow fraction transferred from one pixel to each of the two lateral downslope pixels. Our aim is to assess the effect of ε and soil heterogeneity on the connectivity function compared to the mean runoff flow rate, the wet area and the number of runoff patterns. The analysis of connectivity is carried within the percolation framework. The results show that the integral connectivity scale is more sensitive to the flow dimension and soil heterogeneity compared to the other variables. The wet area fraction does not depend on ε. Unlike previous studies, we find that increased runoff production is not necessarily related to increased connectivity. The use of the connectivity function within the percolation framework appears to be a valuable method for assessing the impact of soil heterogeneity and flow dimension on the runoff organization during a rainfall event. Copyright © 2014 John Wiley & Sons, Ltd.     

ERORUN-STAFOR: A collaborative observatory for the multidisciplinary study of the critical zone processes in a tropical volcanic watershed including a Tropical Montane Cloud Forest

Tropical volcanic islands are biodiversity hotspots where the Critical Zone (CZ) still remains poorly studied. In such steep topographic environments associated with extreme climatic events (cyclones), deployment and maintenance of monitoring equipment is highly challenging. While a few Critical Zone Observatories (CZOS) are located in tropical volcanic regions, none of them includes a Tropical Montane Cloud Forest (TMCF) at the watershed scale. We present here the dataset of the first observatory from the French network of critical zone observatories (OZCAR) located in an insular tropical and volcanic context, integrating a ‘Tropical Montane Cloud Forest’: The ERORUN-STAFOR observatory. This collaborative observatory is located in the northern part of La Réunion island (Indian Ocean) within the 45.0 km² watershed of Rivière des Pluies (i.e., Rainfall river) which hosts the TMCF of Plaines des Fougères, one of the best preserved natural habitats in La Réunion Island. Since 2014, the ERORUN-STAFOR monitoring in collaboration with local partners collected a multidisciplinary dataset with a constant improvement of the instrumentation over time. At the watershed scale and in its vicinity, the ERORUN-STAFOR observatory includes 10 measurement stations covering the upstream, midstream and downstream part of the watershed. The stations record a total of 48 different variables through continuous (sensors) or periodic (sampling) monitoring. The dataset consists of continuous time series variables related to (i) meteorology, including precipitation, air temperature, relative humidity, wind speed and direction, net radiation, atmospheric pressure, cloud water flux, irradiance, leaf wetness and soil temperature, (ii) hydrology, including water level and temperature, discharge and electrical conductivity (EC) of stream, (iii) hydrogeology, including (ground)water level, water temperature and EC in two piezometers and one horizontally drilled groundwater gallery completed by soil moisture measurements under the canopy. The dataset is completed by periodic time series variables related to (iv) hydrogeochemistry, including field parameters and water analysis results. The periodic sampling survey provides chemical and isotopic compositions of rainfall, groundwater, and stream water at different locations of this watershed. The ERORUN-STAFOR monitoring dataset extends from 2014 to 2022 with an acquisition frequency from 10 min to hourly for the sensor variables and from weekly to monthly frequency for the sampling. Despite the frequent maintenance of the monitoring sites, several data gaps exist due to the remote location of some sites and instrument destruction by cyclones. Preliminary results show that the Rivière des Pluies watershed is characterized by high annual precipitation (>3000 mm y⁻¹) and a fast hydrologic response to precipitation (≈2 h basin lag time). The long-term evolution of the deep groundwater recharge is mainly driven by the occurrence of cyclone events with a seasonal groundwater response. The water chemical results support existing hydrogeological conceptual models suggesting a deep infiltration of the upstream infiltrated rainfall. The TMCF of Plaine des Fougères shows a high water storage capacity (>2000% for the Bryophytes) that makes this one a significant input of water to groundwater recharge which still needs to be quantified. This observatory is a unique research site in an insular volcanic tropical environment offering three windows of observation for the study of critical zone processes through upstream-midstream-downstream measurements sites. This high-resolution dataset is valuable to assess the response of volcanic tropical watersheds and aquifers at both event and long-term scales (i.e., global change). It will also provide insights in the hydrogeological conceptual model of volcanic islands, including the significant role of the TMCFs in the recharge processes as well as the watershed hydrosedimentary responses to extreme climatic events and their respective evolution under changing climatic conditions. All data sets are available at https://doi.org/10.5281/zenodo.7983138 .     

Rotation of the Semail ophiolite (Oman): Additional Paleomagnetic data from the volcanic sequence

Thirty-two flows (247 cores) were sampled in the V1 (Geotimes) and V2 (Lasail) volcanic units of the Semail ophiolite, Oman (Aswad, Fizh, Hilti, Sarami, Wuqbah, and Tayin massifs). Paleomagnetic analysis of the samples was complicated by a large overlap of the two components of magnetization carried by the rocks: a crystalline remanent magnetization (CRM) acquired in the present day field, probably during weathering, and an older CRM probably produced by oxidation of the original titanomagnetites during hydrothermal event(s). If the magnetization carried by the V1 samples was acquired during the hydrothermal event related to the emplacement of these lava, e.g., during and/or shortly after cooling, the tectonic unity of the northern domain has to be questioned and a differential rotation considered between the Aswad and Hilti-Sarami massifs but, by the time of emplacement of the V2 series, this northern area seems to behave as one large unit. As only one set of data is available for the southern Tayin-Sumail massif, it is premature but a possible relative rotation on the order of 90° can be suspected between the Hilti-Sarami and Tayin-Sumail massifs, rotation which would have occurred after emplacement of the V2 series.     

Synthetic hydrograph generation by hydrological donors

A method to build synthetic hydrographs is introduced, based on 1300 gauging stations in France and Switzerland, covering a wide range of size and climatology. For each station, an average of two floods per year are selected by a peak-over-threshold method, providing about 69?000 hydrographs. For a given catchment, some “donor stations” are selected with criteria of proximity in space, size and runoff production. These donors provide hundreds of hydrographs which can complement the ones recorded locally, or replace them if no hydrograph is available. With this subset of hydrographs, one can estimate the catchment’s average peak-to-volume ratio of floods, and build the corresponding median hydrograph. Another application is, for a given daily discharge sequence (being observed or simulated), to generate a relevant synthetic hydrograph by combining appropriate hydrographs of the subset. These methods are assessed by performing a jack-knife validation on a wide dataset of stations.     

Analytical model for the in‐plane seismic performance of cold‐formed steel‐framed gypsum partition walls

This paper proposes an experimentally verified procedure to analytically model cold‐formed steel‐framed gypsum nonstructural partition walls considering all the critical components. In this model, the nonlinear behaviors of the connections are represented by hysteretic load‐deformation springs, which have been calibrated using the component‐level experimental data. The studs and tracks are modeled adopting beam elements with their section properties accounting for nonlinear behavior. The gypsum boards are simulated by linear four‐node shell elements. The proposed procedure is implemented to generate the analytical models of three full‐scale partition wall specimens in the OpenSees platform. The specimens were tested as a part of the NEESR‐GC Project on Simulation of the Seismic Performance of Nonstructural Systems. Force‐displacement responses, cumulative dissipated energy, and damage mechanisms from the analytical simulation are compared to the experimental results. The comparison shows that the analytical model accurately predicts the trend of the response as well as the possible damage mechanisms. The procedure proposed here can be adopted in future studies by researchers and also engineers to assess the seismic performance of partition walls with various dimensions and construction details, especially where test data are not available. Copyright © 2015 John Wiley & Sons, Ltd.     

Mineral Resources: The Bread and Butter of NRR

Natural Resources Research -     

Multi-scale Numerical Simulation and 3D Modeling for Deep Mineral Exploration in the Jiaojia Gold District,China

In this study, deposit- and district-scale three-dimensional (3D) fault-and-intrusion structure models were constructed, based on which a numerical simulation was implemented in the Jiaojia gold district, China. The numerical simulation of the models shows the basic metallogenic path and trap of the gold deposits using mineral system theory. The objective of this study was to delineate the uncertainty of the geometry or buffer zones of the ore-forming and ore-controlling fault-and-intrusion domains in 3D environment representing the exploration criteria extraction and the gold potential targeting in the study area. The fast Lagrangian analysis of continua in three dimensions was used as the platform to define the stress deformation fracture ore storage and the hydrothermal seepage channel zone based on the gold deposit features and metallogenic model in the study area. The validity of the numerical simulation was verified by comparing it with robust 3D geological models of the large Xincheng gold deposit. The potential targeting zones are analyzed for uncertainty and then evaluated by Boolean operation in a 3D geological model using the computer-aided design platform. The research results are summarized as follows. (1) In the pre-mineralization period, the Jiaodong fault’s left lateral movement created the Jiaojia network faults and formed a fracture zone with NW- to NNW-trending dips of 20° to 40°. (2) During the mineralization period, hydrothermal flow was associated with the intrusion geometry and features. However, it was constrained by the Jiaojia fault, which blocked the vadose flow into the upper wall rock and made the hydrothermal route close to the fault in the footwall fracture zones. (3) Three gold potential targets were identified by the numerical simulation results in the study area: the NW-trending Sizhuang gold deposit, the NW-trending zone of Jiaojia gold deposit, and the NE-trending zone of the Xincheng gold deposit. (4) The numerical simulation results show the fault-and-intrusion metallogenic domain and the hydrothermal alteration zones, which reflect the main ore-controlling and ore-forming factors of mineralization. The information obtained through the numerical simulation discussed here can be used to define exploration criteria in the study area.