Preprints
Filtering by Subject: Earth Sciences
Distributions of geohopanoids in peat: implications for the use of hopanoid-based proxies in natural archives
Published: 2018-02-04
Subjects: Biogeochemistry, Chemistry, Earth Sciences, Environmental Sciences, Geochemistry, Other Physical Sciences and Mathematics, Physical Sciences and Mathematics
Hopanoids are pentacyclic triterpenoids produced by a wide range of bacteria. Within modern settings, hopanoids mostly occur in the biological 17β,21β(H) configuration. However, in some modern peatlands, the C31 hopane is present as the thermally-mature 17α,21β(H) stereoisomer. This has traditionally been ascribed to isomerisation at the C-17 position catalysed by the acidic environment. However, [...]
Groundwater pumping impacts on real stream networks: testing the performance of simple management tools
Published: 2018-02-02
Subjects: Earth Sciences, Environmental Sciences, Hydrology, Physical Sciences and Mathematics, Water Resource Management
Quantifying reductions in streamflow due to groundwater pumping (‘streamflow depletion’) is essential for conjunctive management of groundwater and surface water resources. Analytical models are widely used to estimate streamflow depletion but include potentially problematic assumptions such as simplified stream-aquifer geometry and rely on largely untested depletion apportionment equations to [...]
The stratigraphy and eruptive history of the Palaeogene Arran Volcanic Formation, western Scotland: a proximal record of caldera-forming eruptions
Published: 2018-02-01
Subjects: Earth Sciences, Physical Sciences and Mathematics, Volcanology
Caldera-forming volcanic eruptions are among the most dangerous, and can generate extensive pyroclastic deposits and deliver ash into global atmospheric circulation systems. As calderas collapse, the eruptions can deposit thick proximal ignimbrite sequences and thinner ignimbrites more distally. However, the proximal record of caldera collapse is often obscured by later intrusions, volcanism, [...]
Rift-related magmatism influences petroleum systems development in the NE Irish Rockall Basin, offshore Ireland
Published: 2018-01-29
Subjects: Earth Sciences, Geology, Physical Sciences and Mathematics, Tectonics and Structure, Volcanology
Large volumes of hydrocarbons reside in volcanically influenced sedimentary basins. Despite having a good conceptual understanding of how magmatism impacts the petroleum system of such basins, we still lack detailed case studies documenting precisely how intrusive magmatism influences, for example, trap development and reservoir quality. Here we combine 3D seismic reflection, borehole, [...]
Multi-scale segmentation algorithm for pattern-based partitioning of large categorical rasters
Published: 2018-01-28
Subjects: Computer Sciences, Earth Sciences, Geography, Numerical Analysis and Scientific Computing, Other Earth Sciences, Physical Sciences and Mathematics, Social and Behavioral Sciences, Spatial Science
Analyzing large Earth Observation (EO) data on the broad spatial scales frequently involves regionalization of patterns. To automate this process we present a segmentation algorithm designed specifically to delineate segments containing quasi-stationary patterns. The algorithm is designed to work with patterns of a categorical variable. This makes it possible to analyze very large spatial [...]
Volume And Recurrence of Submarine-Fan-Building Turbidity Currents
Published: 2018-01-28
Subjects: Analysis, Applied Mathematics, Earth Sciences, Geology, Geomorphology, Mathematics, Physical Sciences and Mathematics, Sedimentology, Stratigraphy
(now published in "The Depositional Record") Submarine fans are archives of Earth-surface processes and change, recording information about the turbidity currents that construct and sculpt them. The volume and recurrence of turbidity currents are of great interest for geohazard assessment, source-to-sink modeling, and hydrocarbon reservoir characterization. Yet, such dynamics are poorly [...]
Facies architecture of submarine channel deposits on the western Niger Delta slope: Implications for grain-size and density stratification in turbidity currents
Published: 2018-01-28
Subjects: Earth Sciences, Geology, Geomorphology, Mathematics, Oceanography and Atmospheric Sciences and Meteorology, Other Mathematics, Physical Sciences and Mathematics, Sedimentology, Stratigraphy
High-resolution bathymetry, seismic reflection, and piston core data from a submarine channel on the western Niger Delta slope demonstrate that thick, coarse-grained, amalgamated sands in the channel thalweg/axis transition to thin, fine-grained, bedded sands and muds in the channel margin. Radiocarbon ages indicate that axis and margin deposits are coeval. Core data show that bed thickness, [...]
High Resolution, Millennial-Scale Patterns of Bed Compensation on a Sand-Rich Intraslope Submarine Fan, Western Niger Delta Slope
Published: 2018-01-28
Subjects: Earth Sciences, Geology, Geomorphology, Geophysics and Seismology, Other Earth Sciences, Physical Sciences and Mathematics, Sedimentology, Stratigraphy
Near-seafloor core and seismic-reflection data from the western Niger Delta continental slope document the facies, architecture, and evolution of submarine channel and intraslope submarine fan deposits. The submarine channel enters an 8 km long x 8 km wide intraslope basin, where more than 100 m of deposits form an intraslope submarine fan. Lobe deposits in the intraslope submarine fan show no [...]
Comparing submarine and fluvial channel kinematics: Implications for stratigraphic architecture
Published: 2018-01-28
Subjects: Earth Sciences, Geology, Geomorphology, Physical Sciences and Mathematics, Sedimentology, Stratigraphy
Submarine and fluvial channels exhibit qualitatively similar geomorphic patterns, yet produce very different stratigraphic records. We reconcile these seemingly contradictory observations by focusing on the channel-belt scale and quantifying the time-integrated stratigraphic record of the belt as a function of (1) the geometric scale and (2) the trajectory of the geomorphic channel, applying the [...]
Rapid Adjustment of Submarine Channel Architecture to Changes in Sediment Supply
Published: 2018-01-28
Subjects: Earth Sciences, Geology, Geomorphology, Geophysics and Seismology, Physical Sciences and Mathematics, Sedimentology, Stratigraphy
Changes in sediment supply and caliber during the last ~130 ka have resulted in a complex architectural evolution of the Y channel system on the western Niger Delta slope. This evolution consists of four phases, each with documented or inferred changes in sediment supply. Phase 1 flows created wide (1,000 m), low-sinuosity (1.1) channel forms with lateral migration and little to no aggradation. [...]
Climbing Ripple Successions in Turbidite Systems: Depositional Environments, Sedimentation Rates, and Accumulation Times
Published: 2018-01-28
Subjects: Earth Sciences, Geology, Geomorphology, Physical Sciences and Mathematics, Sedimentology, Stratigraphy
Climbing-ripple cross-lamination (CRCL) is most commonly deposited by turbidity currents when suspended load fallout and bedload transport occur contemporaneously. The angle of ripple climb reflects the ratio of suspended load fallout and bedload sedimentation rates, allowing for the calculation of the flow properties and durations of turbidity currents. Three areas exhibiting thick (> 50 m) [...]
Impacts of land-use and land-cover change on stream hydrochemistry in the Cerrado and Amazon biomes
Published: 2018-01-28
Subjects: Chemistry, Computer Sciences, Earth Sciences, Environmental Indicators and Impact Assessment, Environmental Monitoring, Environmental Sciences, Fresh Water Studies, Geography, Hydrology, Natural Resources and Conservation, Oceanography and Atmospheric Sciences and Meteorology, Physical and Environmental Geography, Physical Sciences and Mathematics, Physics, Social and Behavioral Sciences, Soil Science
Studies on the impacts of land-use and land-cover change on stream hydrochemistry in active deforestation zones of the Amazon agricultural frontier are limited and have often used low-temporal-resolution datasets. Moreover, these impacts are not concurrently assessed in well-established agricultural areas and new deforestations hotspots. We aimed to identify these impacts using an experimental [...]
Macrostrat: a platform for geological data integration and deep-time Earth crust research
Published: 2018-01-26
Subjects: Biogeochemistry, Earth Sciences, Geology, Paleobiology, Physical Sciences and Mathematics, Sedimentology, Stratigraphy
Characterizing the lithology, age, and physical-chemical properties of rocks and sediments in the Earths upper crust is necessary to fully assess energy, water, and mineral resources and to address many fundamental questions in the Earth sciences. Although a large number of geological maps, regional geological syntheses, and sample-based measurements have been produced, there is no openly [...]
Detecting orogenic wedge state and the rise of the External Alps by detrital thermochronology
Published: 2018-01-26
Subjects: Earth Sciences, Geochemistry, Geology, Physical Sciences and Mathematics, Tectonics and Structure
Critical taper theory permits the modelling of an orogenic wedge as a single mechanical entity. However, although shallow-crustal orogens dominated by brittle failure have been successfully modelled using critical taper, this remains controversial for major, ductile-failure-dominated orogens. In critical taper models, the steepness of the basal and upper orogenic surfaces defines the critical [...]
The role of H2O on the extraction of melt from crystallising magmas
Published: 2018-01-24
Subjects: Earth Sciences, Geology, Physical Sciences and Mathematics, Volcanology
The segregation and accumulation of felsic melts, from crystallising crustal magma reservoirs, is essential for the chemical evolution of the crust and is a phenomenon preceding some of the largest eruptions on Earth. The physical properties of residual melt and magma and the time over which the conditions remain appropriate for melt extraction are important factors controlling the efficiency of [...]