Streamflow Regime Change in the Delaware River Basin

The combined impacts of hydroclimatic change and land development are widely expected to increase the frequency and magnitude of flooding in the northeast United States, with potential implications to floodplain infrastructure and mapping, hydraulic structures, land management, and flood losses. Additionally, shifting flow regimes pose a challenge for engineers and regulators of stormwater management, dams, and levees because design storms are commonly based on historical data, with the stationarity assumption that the future flow regime will mimic the past. Here, we examine selected long-term (40 to 114 years of data) streamflow records from watersheds of varying size in the upper Delaware River basin to assess changes in streamflow regimes. A structural breakpoint analysis of the streamflow records indicated a break in time-series around the year 2000. Hypothesis testing comparing pre- and post-2000 streamflow metrics (annual peak, median, and 7-day low flows) confirmed a statistically significant shift around the year 2000. For example, median flows across the two time periods were statistically different with over 90% confidence for 14 of 28 gauges considered

Dating the youngest deformation in the Alps with ESR thermochronometry

Low-temperature thermochronology is a useful tool to reconstruct tectonic deformation and landscape evolution within the first 2 km of the crust. It is a suitable tool to investigate deformation associated with cooling and exhumation of the lower crust in orogenic settings. Low temperature thermochronology is applied here to understand the Neogenic post-collisional extensional event that occurred in the Alps, because a gap in previous age dating exists between a thousand and a million years. Quartz is the most common mineral in the crust; occurring in magmatic as well as sedimentary and metamorphic rocks. The potential of quartz electron-spin resonance (ESR) as a radiation dosimeter has been well documented, and many studies applied the method to date sediments and heated rocks (e.g. tephra). In this study, we apply quartz ESR dating as an ultralow-temperature thermochronometer, characterized by a closure temperature of 30°-90°, and dating range of 103-107 years. We show the results of ESR thermochronometry on quartz applied to rocks from crustal-scale faults in the Central (Simplon Fault) and Eastern Alps (Brenner and Salzachtal Faults). Here, the lower crust has been tectonically exhumed, associated with exhumation of the Lepontine Dome and Tauern Window, respectively. Thermochronological data are available from this area, such as fission tracks or U-Th/He data on zircon and apatite. Results of the ESR measurements of 15 samples crossing the Brenner and Salzachtal faults (northern and western border of the Tauern Window) show that the ESR ages of quartz get younger (<1Ma) inside the western part of the Tauern Window, in accordance with fission track and (U-Th)/He ages. In general, younger ages (between 200 and 500 ka) are also obtain closer to the fault zone, localized near (e.g. Simplon Fault) or at the bottom of the valley (e.g. Brenner Fault), compared with the protolithic rocks (600-900 ka). We interpret the trend of the ESR ages as an exhumation of the isotherms due to both recent uplift of the footwall of the fault and for erosion of the valley, where the later overprints the former. These results promise to establish ESR as an ultra-low thermochronometer using quartz for the Quaternary landscape reconstruction of the Alpine chain

Grain-size distribution dataset of supercritical flow sediments from a Gilbert-type delta that are associated with disaggregation bands

This is a dataset of grain-size distribution in sub- and supercritical flow sediments of a Gilbert-type delta from an outcrop in North Germany. Thirteen samples of ca 2.5 kg were dried (at 105°C), and homogenised twice with a sample divider. A representative sample of 1-2 g was then analysed using laser diffraction. The grain-size distribution of the sand has a maximum between fine to medium sand, with a long fine fraction tail down to 0.06 µm and occasional coarse fractions (up to 1.5 mm) in some samples. Specific grain-size distributions correlate with the different sedimentary bedforms from which the samples were taken. This data is important for two reasons: Firstly, sedimentary structures formed by Froude supercritical flows are controlled by grain-size. However, few studies have provided grain-size datasets from the natural record, which often have a much wider grain-size distribution than experimentally-produced supercritical flow deposits. Secondly, the sands were deformed subsequently by disaggregation bands, a type of geological fault that only develops in porous granular materials, i.e. well-sorted, medium sand. The disaggregation bands are indicative of seismic or even aseismic, creeping movement of basement faults

Disaggregation bands as an indicator for slow creep activity on blind faults

Hidden, blind faults have a strong seismic hazard potential. Consequently, there is a great demand for a robust geological indicator of neotectonic activity on such faults. Here, we conduct field measurements of disaggregation bands above known underlying blind faults at several locations in Central Europe. We observe that the disaggregation bands have the same orientation as that of the faults, indicating their close connection. Disaggregation bands develop in unconsolidated, near-surface, sandy sediments. They form by shear-related reorganization of the sediment fabric, as a consequence of grain rolling and sliding processes, which can reduce the porosity. Using an analogue shearing experiment, we show that disaggregation bands can form at a velocity of 2 cm h−1, which is several orders of magnitude slower than seismogenic fault-slip velocities. Based on the field data and the experiments, we infer that disaggregation bands can form in the process zone of active blind faults and serve as an indicator of neotectonic activity, even if the fault creeps at very low slip velocity. Disaggregation bands could open a new path to detect hidden active faults undergoing aseismic movements.publishedVersio

2-D kinematic restoration of the western Tauern Window using thermochronological constraints

The Tauern Window (TW) in the European Alps has a high tectonic complexity. It is a key area to understand a number of important orogenic processes. During the Cretaceous, subduction and accretion of the Penninic realm beneath the northern margin of Adria (Austroalpine) began, which led to collision between Europe (Subpenninic) and the Adria margin, from Eocene to early Oligocene. This resulted in the Penninic and Subpenninic nappe stack in the southward-dipping orogenic wedge. After the “Tauernkristallisation”-event, indentation of the Dolomites Indenter (Eastern Southern Alps) is heralded in the last deformation stage, which bent the primarily W-E striking, dextral Periadriatic Fault System (PFS) separating the Eastern from the Southern Alps, and finally caused this fault system to be sinistrally offset by the NNE-SSW-striking Giudicarie fault system in the Miocene. This last deformation stage resulted in strong N-S shortening (ca. 70 km) of the western TW in front of the Dolomites indenter as well as W-E extension, which formed the Katschberg and Brenner Normal Faults (eastern and western border of the TW), and to lateral extrusion towards the east involving major strike-slip faults (e.g., Inntal Fault, PFS, SEMP). It is widely assumed that all these processes happened synkinematically exhuming the western TW up to ca. 20 km (derived from the throw of the Brenner Normal Fault and by the metamorphic conditions reached). However, the quantitative deformation history of the western TW, and in particular its Subpenninic core (Venediger Duplex, VD), has never been investigated in detail. Our goal is therefore to quantify the deformation and kinematics accommodated by the VD in a first step by restoring the Brenner Base Tunnel cross-section using the software MOVE (Ptx). Since standard balancing of this structure is not possible due to penetrative deformation, we integrate Zircon Fission Track data (partial annealing zone of 240 – 180°C and closure temperature ca. 210°C) as marker for the transition from brittle to viscous conditions in the felsic rocks of the VD: Any folding in the VD must be older than the ZFT age of the corresponding unit. For this reason, we first displaced the whole duplex structure down along the Sub-Tauern Ramp below the Zircon Fission Track annealing zone. We then unfolded the gneiss cores individually until a symmetrical duplex structure was modeled, which reached 20 km depth. Since the modeling of vertical exhumation, N-S shortening and displacement along the Sub-Tauern Ramp strongly depends on the geothermal gradient (GG), we tested different GG. Resulting exhumation rates related to a GG of 30°C/km and 50°/km fit well with former studies, which means that 30-50°C/km is a reasonable range for the GG during the last deformation stage

Disaggregation bands as an indicator for slow creep activity on blind faults

Hidden, blind faults have a strong seismic hazard potential. Consequently, there is a great demand for a robust geological indicator of neotectonic activity on such faults. Here, we conduct field measurements of disaggregation bands above known underlying blind faults at several locations in Central Europe. We observe that the disaggregation bands have the same orientation as that of the faults, indicating their close connection. Disaggregation bands develop in unconsolidated, near-surface, sandy sediments. They form by shear-related reorganization of the sediment fabric, as a consequence of grain rolling and sliding processes, which can reduce the porosity. Using an analogue shearing experiment, we show that disaggregation bands can form at a velocity of 2 cm h−1, which is several orders of magnitude slower than seismogenic fault-slip velocities. Based on the field data and the experiments, we infer that disaggregation bands can form in the process zone of active blind faults and serve as an indicator of neotectonic activity, even if the fault creeps at very low slip velocity. Disaggregation bands could open a new path to detect hidden active faults undergoing aseismic movements. © 2022, The Author(s)

How to select interventions for promoting physical activity in schools? Combining preferences of stakeholders and scientists

Background The failure to scale-up and implement physical activity (PA) interventions in real world contexts, which were previously successful under controlled conditions, may be attributed to the different criteria of stakeholders and scientists in the selection process of available interventions. Therefore, the aim of our study was to investigate and compare the criteria applied by local stakeholders and scientists for selecting amongst suitable school-based PA interventions for implementation. Methods We conducted a three-round repeated survey Delphi study with local stakeholders (n = 7; Bremen, Germany) and international scientific PA experts (n = 6). Independently for both panels, two rounds were utilized to develop a list of criteria and the definitions of criteria, followed by a prioritization of the criteria in the third round. For each panel, a narrative analysis was used to rank-order unique criteria, list the number of scorers for the unique criteria and synthesize criteria into overarching categories. Results The stakeholders developed a list of 53 unique criteria, synthesized into 11 categories with top-ranked criteria being ‘free of costs’, ‘longevity’ and ‘integration into everyday school life’. The scientists listed 35 unique criteria, synthesized into 7 categories with the top-ranked criteria being ‘efficacy’, ‘potential for reach’ and ‘feasibility’. The top ranked unique criteria in the stakeholder panel were distributed over many categories, whereas four out of the top six criteria in the scientist panel were related to ‘evidence’. Conclusions Although stakeholders and scientists identified similar criteria, major differences were disclosed in the prioritization of the criteria. We recommend an early collaboration of stakeholders and scientists in the design, implementation, and evaluation of PA interventions