The role of inherited extensional fault segmentation and linkage in contractional orogenesis: a reconstruction of Lower Cretaceous inverted rift basins in the Eastern Cordillera of Colombia

Lower Cretaceous early syn‐rift facies along the eastern flank of the Eastern Cordillera of Colombia, their provenance, and structural context, reveal the complex interactions between Cretaceous extension, spatio‐temporal trends in associated sedimentation, and subsequent inversion of the Cretaceous Guatiquía paleo‐rift. South of 4°30′N lat, early syn‐rift alluvial sequences in former extensional footwall areas were contemporaneous with fan‐delta deposits in shallow marine environments in adjacent hanging‐wall areas. In general, footwall erosion was more pronounced in the southern part of the paleorift. In contrast, early syn‐rift sequences in former footwall areas in the northern rift sectors mainly comprise shallow marine supratidal sabkha to intertidal strata, whereas hanging‐wall units display rapid transitions to open‐sea shales. In comparison with the southern paleo‐rift sector, fan‐delta deposits in the north are scarce, and provenance suggests negligible footwall erosion. The southern graben segment had longer, and less numerous normal faults, whereas the northern graben segment was characterized by shorter, rectilinear faults. To the east, the graben system was bounded by major basin‐margin faults with protracted activity and greater throw as compared with intrabasinal faults to the west. Intrabasinal structures grew through segment linkage and probably interacted kinematically with basin‐margin faults. Basin‐margin faults constitute a coherent fault system that was conditioned by pre‐existing basement fabrics. Structural mapping, analysis of present‐day topography, and balanced cross sections indicate that positive inversion of extensional structures was focused along basin‐bounding faults, whereas intrabasinal faults remained unaffected and were passively transported by motion along the basin‐bounding faults. Thus, zones of maximum subsidence in extension accommodated maximum elevation in contraction, and former topographic highs remained as elevated areas. This documents the role of basin‐bounding faults as multiphased, long‐lived features conditioned by basement discontinuities. Inversion of basin‐bounding faults was more efficient in the southern than in the northern graben segment, possibly documenting the inheritance and pivotal role of fault‐displacement gradients. Our observations highlight similarities between inversion features in orogenic belts and intra‐plate basins, emphasizing the importance of the observed phenomena as predictive tools in the spatiotemporal analysis of inversion histories in orogens, as well as in hydrocarbon and mineral deposits exploration.     

Assessment of spatial transferability of process‐based hydrological model parameters in two neighbouring catchments in the Himalayan Region

Estimating the hydrological regime of ungauged catchments in the Himalayan region is challenging due to a lack of sufficient monitoring stations. In this paper, the spatial transferability of the model parameters of the process‐oriented J2000 hydrological model was investigated in 2 glaciated subcatchments of the Koshi river basin in eastern Nepal. The catchments have a high degree of similarity with respect to their static landscape features. The model was first calibrated (1986–1991) and validated (1992–1997) in the Dudh Koshi subcatchment. The calibrated and validated model parameters were then transferred to the nearby Tamor catchment (2001–2009). Sensitivity and uncertainty analyses were carried out for both subcatchments to discover the sensitivity range of the parameters in the two catchments. The model represented the overall hydrograph well in both subcatchments, including baseflow, rising and falling limbs; however, the peak flows were underestimated. The efficiency results according to both Nash–Sutcliffe (ENS) and the coefficient of determination (r²) were above 0.84 in both catchments (1986–1997 in Dudh Koshi and 2001–2009 in Tamor). The ranking of the parameters in respect to their sensitivity matched well for both catchments while taking ENS and log Nash–Sutcliffe (LNS) efficiencies into account. However, there were some differences in sensitivity to ENS and LNS for moderately and less‐sensitive parameters, although the majority (13 out of 16 for ENS and 16 out of 16 for LNS) had a sensitivity response in a similar range. The generalized uncertainty likelihood estimation results suggest that the parameter uncertainty are most of the time within the range and the ensemble mean matches very good (ENS: 0.84) with observed discharge. The results indicate that transfer of the J2000 parameters to a neighbouring catchment in the Himalayan region with similar physiographic landscape characteristics is viable. This indicates the possibility of applying a calibrated process‐based J2000 model to other ungauged catchments in the Himalayan region, which could provide important insights into the hydrological system dynamics and provide much needed information to support water resources planning and management.     

Evaluation of a spatial rainfall generator for generating high resolution precipitation projections over orographically complex terrain

Space–time variability of precipitation plays a key role as driver of many environmental processes. The objective of this study is to evaluate a spatiotemporal (STG) Neyman–Scott Rectangular Pulses (NSRP) generator over orographically complex terrain for statistical downscaling of climate models. Data from 145 rain gauges over a 5760-km² area of Cyprus for 1980–2010 were used for this study. The STG was evaluated for its capacity to reproduce basic rainfall statistical properties, spatial intermittency, and extremes. The results were compared with a multi-single site NRSP generator (MSG). The STG performed well in terms of average annual rainfall (+1.5 % in comparison with the 1980–2010 observations), but does not capture spatial intermittency over the study area and extremes well. Daily events above 50 mm were underestimated by 61 %. The MSG produced a similar error (+1.1 %) in terms of average annual rainfall, while the daily extremes (>50-mm) were underestimated by 11 %. A gridding scheme based on scaling coefficients was used to interpolate the MSG data. Projections of three Regional Climate Models, downscaled by MSG, indicate a 1.5–12 % decrease in the mean annual rainfall over Cyprus for 2020–2050. Furthermore, the number of extremes (>50-mm) for the 145 stations is projected to change between ?24 and +2 % for the three models. The MSG modelling approach maintained the daily rainfall statistics at all grid cells, but cannot create spatially consistent daily precipitation maps, limiting its application to spatially disconnected applications. Further research is needed for the development of spatial non-stationary NRSP models.     

Miocene to Quaternary basin evolution at the southeastern Andean Plateau (Puna) margin (ca. 24°S lat,Northwestern Argentina)

The Andean Plateau of NW Argentina is a prominent example of a high‐elevation orogenic plateau characterized by internal drainage, arid to hyper‐arid climatic conditions and a compressional basin‐and‐range morphology comprising thick sedimentary basins. However, the development of the plateau as a geomorphic entity is not well understood. Enhanced orographic rainout along the eastern, windward plateau flank causes reduced fluvial run‐off and thus subdued surface‐process rates in the arid hinterland. Despite this, many Puna basins document a complex history of fluvial processes that have transformed the landscape from aggrading basins with coalescing alluvial fans to the formation of multiple fluvial terraces that are now abandoned. Here, we present data from the San Antonio de los Cobres (SAC) area, a sub‐catchment of the Salinas Grandes Basin located on the eastern Puna Plateau bordering the externally drained Eastern Cordillera. Our data include: (a) new radiometric U‐Pb zircon data from intercalated volcanic ash layers and detrital zircons from sedimentary key horizons; (b) sedimentary and geochemical provenance indicators; (c) river profile analysis; and (d) palaeo‐landscape reconstruction to assess aggradation, incision and basin connectivity. Our results suggest that the eastern Puna margin evolved from a structurally controlled intermontane basin during the Middle Miocene, similar to intermontane basins in the Mio‐Pliocene Eastern Cordillera and the broken Andean foreland. Our refined basin stratigraphy implies that sedimentation continued during the Late Mio‐Pliocene and the Quaternary, after which the SAC area was subjected to basin incision and excavation of the sedimentary fill. Because this incision is unrelated to baselevel changes and tectonic processes, and is similar in timing to the onset of basin fill and excavation cycles of intermontane basins in the adjacent Eastern Cordillera, we suspect a regional climatic driver, triggered by the Mid‐Pleistocene Climate Transition, caused the present‐day morphology. Our observations suggest that lateral orogenic growth, aridification of orogenic interiors, and protracted plateau sedimentation are all part of a complex process chain necessary to establish and maintain geomorphic characteristics of orogenic plateaus in tectonically active mountain belts.     

Quasi-periodic oscillations in low-mass X-ray binaries and constraints on the equation of state of neutron star matter

Recently discovered quasi-periodic oscillations in the X-ray brightness of low-mass X-ray binaries are used to derive constraints on the mass of the neutron star component and the equation of state of neutron star matter. The observations are compared with models of rapidly rotating neutron stars which are calculated by means of an exact numerical method in full relativity. For the equations of state we select a broad collection of models representing different assumptions about the many-body structure and the complexity of the composition of superdense matter. The mass constraints differ from their values in the approximate treatment by ∼10 per cent. Under the assumption that the maximum frequency of the quasi-periodic oscillations originates from the innermost stable orbit, the mass of the neutron star is in the range M ∼1.92–2.25 M_⊙. The quasi-periodic oscillation in the Atoll-source 4U 1820−30 in particular is only consistent with equations of state that are rather stiff at high densities, which is explainable, so far, only with pure nucleonic/leptonic composition. This interpretation contradicts the hypothesis that the protoneutron star formed in SN 1987A collapsed to a black hole, since this would demand a maximum neutron star mass below 1.6 M_⊙. The recently suggested identification of quasi-periodic oscillations with frequencies of about 10 Hz with the Lense–Thirring precession of the accretion disc is found to be inconsistent with the models studied in this work, unless it is assumed that the first overtone of the precession is observed.     

Integrated global change impact studies in the Arctic: the role of the stakeholders

Responses to global change impacts require the specification of mitigation and adaptation options. Integrated regional impact studies provide some of the information needed for rational decision making. In order to carry out a comprehensive impact study, the involvement of stakeholders in the planning and execution of the study is seen as a necessary prerequisite for an acceptance of its conclusions by the broad public. One way to pursue such an involvement is through a scientist-stakeholder collaborative. Such a collaborative, for instance institutionalized through a joint scientist-stakeholder steering committee addressing issues related to mutual communication and the integration of individual study results, offers a number of additional advantages. The experience of local residents and the utilization of traditional knowledge may provide insight and expertise inaccessible to scientific investigations. Within the Barents Sea Impact Study, the involvement of stakeholders has been given significant weight early on. One of the main instruments employed in the stakeholder collaborative is the BASIS Information Office. However, given the diversity of backgrounds and interests of stakeholders from four different countries, scientist-stakeholder collaboration represents a significant challenge within BASIS. This notwithstanding, we consider the advantages gained worth the extra effort.     

Remote sensing of terrestrial impact craters: The TanDEM‐X digital elevation model

With the TanDEM‐X digital elevation model (DEM), the terrestrial solid surface is globally mapped with unprecedented accuracy. TanDEM‐X is a German X‐band radar mission whose two identical satellites have been operated in single‐pass interferometer configuration over several years. The acquired data are processed to yield a global DEM with 12 m independent posting and relative vertical accuracies of better than 2 m and 4 m in moderate and mountainous terrain, respectively. This DEM provides new opportunities for space‐borne remote‐sensing studies of the entire sample of terrestrial impact craters. In addition, it represents an interesting repository to aid in the search for new impact crater candidates. We have used the TanDEM‐X DEM to investigate the current set of confirmed impact structures. For a subsample of the craters, including small, midsized, and large structures, we compared the results with those from other DEMs. This quantitative analysis demonstrates the excellent quality of the TanDEM‐X elevation data. Our findings help to estimate what can be gained by using the TanDEM‐X DEM in impact crater studies. They may also be beneficial in identifying the regions and morphologies where the search for currently unknown impact structures might be most promising.     

Seasonal patterns of soil respiration in three types of communities along grass-desert shrub transition in Inner Mongolia,China

The seasonal dynamics of soil respiration in steppe (S. bungeana), desert shrub (A. ordosica), and shrub-perennial (A. ordosica + C. komarovii) communities were investigated during the growth season (May to October) in 2006; their environmental driving factors were also analyzed. In the three communities, soil respiration showed similar characteristics in their growth seasons, with peak respiration values in July and August owing to suitable temperature and soil moisture conditions during this period. Meanwhile, changes in soil respiration were greatly influenced by temperatures and surface soil moistures. Soil water content at a depth of 0 to 10 cm was identified as the key environmental factor affecting the variation in soil respiration in the steppe. In contrast, in desert shrub and shrub-perennial communities, the dynamics of soil respiration was significantly influenced by air temperature. Similarly, the various responses of soil respiration to environmental factors may be attributed to the different soil textures and distribution patterns of plant roots. In desert ecosystems, precipitation results in soil respiration pulses. Soil carbon dioxide (CO₂) effluxes greatly increased after rainfall rewetting in all of the ecosystems under study. However, the precipitation pulse effect differed across the ecosystem. We propose that this may be a result of a reverse effect from the soil texture.