Hyperpycnal wave-modified turbidites of the Pennsylvanian Minturn Formation, north-central Colorado

The Pennsylvanian Minturn Formation in north-central Colorado exhibits a complex stratigraphic architecture of fan-delta deposits that developed in association with high topographic relief in a tectonically active setting. The formation records a wide range of environments including alluvial fan, fluvial, deltaic, and open marine settings. This field trip will examine outcrops of a remarkable ~20 to 35-m-thick, unconformity-bound unit with turbidite-like beds that presumably developed within the lower reaches of incised valleys. This unit consists of dark green shale and graded sandstone beds with tool marks produced by abundant plant material. The sandstone event beds contain evidence for strong unidirectional flows and the variable influence of storm-generated waves. Proximal deposits contain beds with evidence for wave-dominated combined flows, including well developed, large-scale hummocky cross-stratification. Distal sections contain beds with reverse-to-normal grading and vertical successions of sedimentary structures that indicate long-lived waxing-to-waning unidirectional flows in conjunction with storm waves. We interpret these beds as a record of deposition from hyperpycnal flows, i.e., turbidity currents generated directly from highly concentrated river plumes, which waxed and waned in response to the rising and falling flood hydrograph. The focus of this trip will be the hydrodynamic interpretation of these different bed types, including their spatial and stratigraphic distribution

Hyperpycnal wave-modified turbidites of the Pennsylvanian Minturn Formation, north-central Colorado

The Pennsylvanian Minturn Formation in north-central Colorado exhibits a complex stratigraphic architecture of fan-delta deposits that developed in association with high topographic relief in a tectonically active setting. The formation records a wide range of environments including alluvial fan, fluvial, deltaic, and open marine settings. This field trip will examine outcrops of a remarkable ~20 to 35-m-thick, unconformity-bound unit with turbidite-like beds that presumably developed within the lower reaches of incised valleys. This unit consists of dark green shale and graded sandstone beds with tool marks produced by abundant plant material. The sandstone event beds contain evidence for strong unidirectional flows and the variable influence of storm-generated waves. Proximal deposits contain beds with evidence for wave-dominated combined flows, including well developed, large-scale hummocky cross-stratification. Distal sections contain beds with reverse-to-normal grading and vertical successions of sedimentary structures that indicate long-lived waxing-to-waning unidirectional flows in conjunction with storm waves. We interpret these beds as a record of deposition from hyperpycnal flows, i.e., turbidity currents generated directly from highly concentrated river plumes, which waxed and waned in response to the rising and falling flood hydrograph. The focus of this trip will be the hydrodynamic interpretation of these different bed types, including their spatial and stratigraphic distribution

A Reconfigurable Quantum Local Area Network Over Deployed Fiber

Practical quantum networking architectures are crucial for scaling the connection of quantum resources. Yet quantum network testbeds have thus far underutilized the full capabilities of modern lightwave communications, such as flexible-grid bandwidth allocation. In this work, we implement flex-grid entanglement distribution in a deployed network for the first time, connecting nodes in three distinct campus buildings time-synchronized via the Global Positioning System (GPS). We quantify the quality of the distributed polarization entanglement via log-negativity, which offers a generic metric of link performance in entangled bits per second. After demonstrating successful entanglement distribution for two allocations of our eight dynamically reconfigurable channels, we demonstrate remote state preparation -- the first realization on deployed fiber -- showcasing one possible quantum protocol enabled by the distributed entanglement network. Our results realize an advanced paradigm for managing entanglement resources in quantum networks of ever-increasing complexity and service demands

Genetic Structure, Linkage Disequilibrium and Signature of Selection in Sorghum: Lessons from Physically Anchored DArT Markers

Population structure, extent of linkage disequilibrium (LD) as well as signatures of selection were investigated in sorghum using a core sample representative of worldwide diversity. A total of 177 accessions were genotyped with 1122 informative physically anchored DArT markers. The properties of DArTs to describe sorghum genetic structure were compared to those of SSRs and of previously published RFLP markers. Model-based (STRUCTURE software) and Neighbor-Joining diversity analyses led to the identification of 6 groups and confirmed previous evolutionary hypotheses. Results were globally consistent between the different marker systems. However, DArTs appeared more robust in terms of data resolution and bayesian group assignment. Whole genome linkage disequilibrium as measured by mean r2 decreased from 0.18 (between 0 to 10 kb) to 0.03 (between 100 kb to 1 Mb), stabilizing at 0.03 after 1 Mb. Effects on LD estimations of sample size and genetic structure were tested using i. random sampling, ii. the Maximum Length SubTree algorithm (MLST), and iii. structure groups. Optimizing population composition by the MLST reduced the biases in small samples and seemed to be an efficient way of selecting samples to make the best use of LD as a genome mapping approach in structured populations. These results also suggested that more than 100,000 markers may be required to perform genome-wide association studies in collections covering worldwide sorghum diversity. Analysis of DArT markers differentiation between the identified genetic groups pointed out outlier loci potentially linked to genes controlling traits of interest, including disease resistance genes for which evidence of selection had already been reported. In addition, evidence of selection near a homologous locus of FAR1 concurred with sorghum phenotypic diversity for sensitivity to photoperiod

Lithologic, tectonic, and climatic controls on chemical weathering, soil production, and erosion in New Zealand

Over geologic timescales, chemical weathering in mountain landscapes may play an important role in regulating atmospheric CO2. Understanding the feedbacks between climate, tectonics, erosion rates, biota, and weathering has been a recent focus of research, but disentangling these complex relationships remains a challenge. One area of particular interest has been the potential for a kinetic limit to weathering and soil production. Studies in New Zealand's Southern Alps were among the first to clearly exceed proposed kinetic limits on soil production and demonstrate thresholds in the influence of precipitation on chemical weathering. Here we present a new dataset that addresses chemical weathering, soil production rates, and surface erosion rates, measured across an altitudinal transect in the Tararua Range on New Zealand's North Island. The transect spans a kilometer in relief, and receives 3.5-5.5 m of annual precipitation. Underlying bedrock comprises silty and sandy members of the same Cretaceous Greywacke, but subtle lithologic changes correspond to abrupt shifts in soil production rates and total weathering. Total weathering across the transect is roughly invariant for each lithology and reflects near-complete depletion of weatherable species, consistent with a previously proposed threshold in the influence of precipitation. However, spatial patterns in weathering differ markedly in saprolite and in soils. Deep weathering in saprolite decreases with elevation and makes up a large fraction of the total weathering. This pattern suggests that climate may influence saprolite weathering, even where the total weathering is supply-limited. Spatial patterns in saprolite and total weathering do not correlate with an abrupt vegetation transition from dense forest to alpine tussock, which may suggest that biota are more strongly affected by a temperature threshold or more complex biogeochemical cycling. We contrast these results with new and previously published data from the Southern Alps, which have a similar climate but experience rapid tectonic uplift. There, the fresh supply of minerals to soils provided by uplift and erosion may enable much faster weathering and soil production rates. Taken together, these observations suggest a strong lithologic and tectonic control on soil production and weathering rates in humid climates

Chemical Weathering and Organic Carbon Turnover in Soil

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