Preprints
Filtering by Subject: Other Earth Sciences
Machine Learning for Inferring CO2 Fluxes: The New Metaphysics of Neural Nets
Published: 2019-10-24
Subjects: Earth Sciences, Environmental Sciences, Other Earth Sciences, Physical Sciences and Mathematics
The advent of direct high-resolution global surface measurements of CO2 from the recently launched NASA Orbiting Carbon Observatory (OCO-2) satellite offers an opportunity to improve the estimate of Net Ecosystem Exchange (NEE) over land. Long-term measurements of CO2flux obtained from eddy covariance instruments on Flux towers show large annual differences with NEE calculated by inverse methods [...]
Plate tectonics drive deep biosphere microbial community structure
Published: 2019-10-13
Subjects: Earth Sciences, Environmental Microbiology and Microbial Ecology Life Sciences, Life Sciences, Microbiology, Other Earth Sciences, Physical Sciences and Mathematics
The deep subsurface is one of Earth’s largest biomes. Here, microorganisms modify volatiles moving between the deep and surface Earth. However, it is unknown whether large-scale tectonic processes affect the distribution of microorganisms across this subterranean landscape. We sampled subsurface microbial ecosystems in deeply-sourced springs across the Costa Rican convergent margin. Noble gases, [...]
Holocene relative sea-level changes and glacial isostatic adjustment of the U.S. Atlantic coast
Published: 2019-09-30
Subjects: Climate, Earth Sciences, Environmental Sciences, Geomorphology, Glaciology, Oceanography and Atmospheric Sciences and Meteorology, Other Earth Sciences, Physical Sciences and Mathematics, Sedimentology, Stratigraphy, Tectonics and Structure
The first quality-controlled Holocene sea-level database for the U.S. Atlantic coast has been constructed from 686 sea-level indicators. The database documents a decreasing rate of relative sea-level (RSL) rise through time with no evidence of sea level being above present in the middle to late Holocene. The highest rates of RSL rise are found in the mid-Atlantic region. We employ the database to [...]
Repeated degradation and progradation of a submarine slope over geological timescales
Published: 2019-09-30
Subjects: Earth Sciences, Geology, Other Earth Sciences, Physical Sciences and Mathematics, Sedimentology, Stratigraphy, Tectonics and Structure
Submarine slopes prograde via accretion of sediment to clinoform foresets, and degrade in response to channel or canyon incision, or mass-wasting processes. The timescales over which progradation and degradation occur, and the large-scale stratigraphic record of these processes, remain unclear due poor age constraints in subsurface-based studies, and areally limited exposures of exhumed systems. [...]
Controls on variations in minibasin geometries: Lower Congo Basin, offshore Angola
Published: 2019-08-30
Subjects: Earth Sciences, Geology, Other Earth Sciences, Physical Sciences and Mathematics, Tectonics and Structure
In passive margin salt basins, the distinct tectonic domains of thin-skinned extension and contraction exert important controls on the geometry and evolution of minibasins. In this study, we use a semi-regional 3D seismic dataset from the Lower Congo Basin to investigate the spatial and temporal evolution of a network of salt-related minibasins and intervening salt walls and diapirs during [...]
Deep-water reservoir distribution on a salt-influenced slope, Santos Basin, offshore Brazil
Published: 2019-08-07
Subjects: Earth Sciences, Geology, Other Earth Sciences, Physical Sciences and Mathematics, Sedimentology, Stratigraphy, Tectonics and Structure
Studies of near-seabed datasets show that salt tectonics controls the distribution and architecture of deep-water reservoirs in many salt-influenced basins. It is typically difficult, however, to study the distribution and stratigraphic evolution of depositional systems preserved at deeper, economically significant depths, reflecting poor seismic imaging of steeply dipping strata flanking [...]
Southern Ocean Phytoplankton Blooms Observed by Biogeochemical Floats
Published: 2019-07-16
Subjects: Earth Sciences, Oceanography, Oceanography and Atmospheric Sciences and Meteorology, Other Earth Sciences, Physical Sciences and Mathematics
The spring bloom in the Southern Ocean is the rapid-growth phase of the seasonal cycle in phytoplankton. Many previous studies have characterized the spring bloom using chlorophyll estimates from satellite ocean color observations. Assumptions regarding the chlorophyll-to-carbon ratio within phytoplankton and vertical structure of biogeochemical variables lead to uncertainty in satellite-based [...]
Are magnetic stripes on the Cuvier Abyssal Plain (offshore NW Australia) diagnostic of oceanic crust?
Published: 2019-06-22
Subjects: Earth Sciences, Geology, Geophysics and Seismology, Other Earth Sciences, Physical Sciences and Mathematics, Tectonics and Structure
Magnetic stripes have long been used to define the presence and age of oceanic crust. However, continental crust heavily intruded by magma can record magnetic reversals akin to those observed in oceanic crust. We re-evaluate the nature of the Cuvier Abyssal Plain (CAP), offshore NW Australia, which hosts magnetic stripes and has previously been defined as oceanic crust. We use magnetic, 2D [...]
Holocene sedimentary record and coastal evolution in the Makran subduction zone (Iran)
Published: 2019-05-14
Subjects: Earth Sciences, Geomorphology, Other Earth Sciences, Physical Sciences and Mathematics, Sedimentology
The Makran coast displays evidence of surface uplift since at least the Late Pleistocene, but it remains uncertain whether this displacement is accommodated by creep on the subduction interface, or in a series of large earthquakes. Here, we address this problem by looking at the short term (Holocene) history of continental vertical displacements recorded in the geomorphology and sedimentary [...]
Using a Superconducting Gravimeter in Support of Absolute Gravity Campaigning — A feasibility study
Published: 2019-05-13
Subjects: Earth Sciences, Engineering, Life Sciences, Other Earth Sciences, Physical Sciences and Mathematics
Preparing for joint analysis of absolute gravity (AG) campaigns, this report investigates whether a stationary superconducting gravimeter (SCG) can provide a long-term stable measurement of site-dependent perturbations that help in reduction to the local value of little-$g$ and its secular rate of change. The crucial element concerns the discrimination of instrumental drift components from trends [...]
On the automatic and a priori design of unstructured mesh resolution for coastal ocean circulation models
Published: 2019-05-10
Subjects: Civil and Environmental Engineering, Earth Sciences, Engineering, Oceanography, Oceanography and Atmospheric Sciences and Meteorology, Other Civil and Environmental Engineering, Other Earth Sciences, Physical Sciences and Mathematics
This study investigates the design of unstructured mesh resolution and its impact on the modeling of barotropic tides along the United States East Coast and Gulf Coast (ECGC). A discrete representation of a computational ocean domain (mesh design) is necessary due to finite computational resources and an incomplete knowledge of the physical system (e.g., shoreline and seabed topography). The [...]
Three Billion Year Secular Evolution of the Triple Oxygen Isotope Composition of Marine Chert
Published: 2019-05-07
Subjects: Earth Sciences, Geochemistry, Other Earth Sciences, Physical Sciences and Mathematics
The 18O/16O ratios of ancient marine minerals show a puzzling increase over geologic time. Long-term changes in temperature, seawater 18O/16O ratios, and post-depositional overprinting can all explain this trend, but few tracers can distinguish between these scenarios. Here, we report high-precision 18O/16O and 17O/16O ratios of cherts through 3.4 Ga of Earth′s history. We find that Phanerozoic [...]
Application of multivariate statistical methods to hydrogeological property parameterisation from geotechnical and geophysical data
Published: 2019-04-26
Subjects: Earth Sciences, Environmental Sciences, Geology, Hydrology, Other Earth Sciences, Physical Sciences and Mathematics, Water Resource Management
Hydrogeological data sets are often relatively sparse compared to the scale of investigation, resulting in degrees of uncertainty which, although constrained, may be considered as not acceptable for achieving the desired precision in numerical modelling. The potential use of multivariate statistical methods in identifying correlations between geotechnical properties of the rock mass and hydraulic [...]
Characterising strong force networks produced during granular shear using percolation methods: Revealing the bridge between local grain scale processes and macroscopic sliding
Published: 2019-04-08
Subjects: Earth Sciences, Geology, Geophysics and Seismology, Other Earth Sciences, Physical Sciences and Mathematics, Physics, Tectonics and Structure
Faults, landslides and subglacial till often contain accumulations of granular debris. Their macroscopic motion is at least to some extent determined by the processes operating in this sheared granular material. A valid question in these environments is how the local behaviour at the individual granular contacts actually sums up to influence macroscopic sliding. Laboratory experiments and [...]
Determining cooling rates from mica 40Ar/39Ar thermochronology data: effect of cooling path shape
Published: 2019-04-02
Subjects: Earth Sciences, Geochemistry, Geology, Other Earth Sciences, Physical Sciences and Mathematics
Tectonic models are commonly underpinned by metamorphic cooling rates derived from diffusive-loss thermochronology data. Such cooling ages are usually linked to temperature via Dodson’s 1973 closure temperature (TC) formulation, which specifies a 1/time-shaped cooling path. Geologists, however, commonly discuss cooling rates as a linear temperature/time shape. We present the results of a series [...]