Preprints
Filtering by Subject: Earth Sciences
A potential link between waterfall recession rate and bedrock channel concavity
Published: 2018-03-15
Subjects: Earth Sciences, Geomorphology, Physical Sciences and Mathematics
The incision of bedrock channels is typically modeled through the stream power or the shear stress applied on the channel bed. However, this approach is not valid for quasi-vertical knickpoints (hereafter waterfalls), where water and sediments do not apply direct force on the vertical face and waterfall retreat rate is often modeled as a power function of drainage area. These different incision [...]
Slow-slip events in semi-brittle serpentinite fault zones
Published: 2018-03-14
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
Slow-slip events are earthquake-like events only with much lower slip rates. While peak coseismic velocities can reach tens of meters per second, slow-slip is on the order of 1E-7 m/s and may last for days to weeks. Under the rate-and-state model of fault friction, slow-slip is produced only when the asperity size is commensurate with the critical nucleation size, a function of frictional [...]
Reporting negative results to stimulate experimental hydrology
Published: 2018-03-13
Subjects: Earth Sciences, Hydrology, Life Sciences, Physical Sciences and Mathematics
Experimental work in hydrology is in decline. Based on a community survey, Blume et al. showed that the hydrological community associates experimental work with greater risks. One of the main issues with experimental work is the higher chance on negative results (defined here as when the expected or wanted result was not observed despite careful experimental design, planning and execution), [...]
Investigation of variable aeration of monodisperse mixtures: implications for Pyroclastic Density Currents
Published: 2018-03-13
Subjects: Earth Sciences, Geology, Physical Sciences and Mathematics, Volcanology
The high mobility of dense pyroclastic density currents (PDCs) is commonly attributed to high gas pore pressures. However, the influence of spatial and temporal variations in pore pressure within PDCs has yet to be investigated. Theory suggests that variability in the fluidisation and aeration of a current will have a significant control on PDC flow and deposition. In this study, the effect of [...]
Monoclinal flexure of an orogenic plateau margin during subduction, south Turkey
Published: 2018-03-12
Subjects: Earth Sciences, Geology, Physical Sciences and Mathematics, Tectonics and Structure
Geologic evidence across orogenic plateau margins enables the discrimination of the relative contributions of orogenic, epeirogenic and/or climatic processes that lead to growth and maintenance of those plateaus and their margins. Here, we discuss the mode of formation of the southern margin of the Central Anatolian Plateau (SCAP) and evaluate its time of formation using fieldwork in the onshore [...]
Resolving the era of river-forming climates on Mars using stratigraphic logs of river-deposit dimensions
Published: 2018-03-10
Subjects: Earth Sciences, Geology, Geomorphology, Physical Sciences and Mathematics, Sedimentology, Stratigraphy
River deposits are one of the main lines of evidence that tell us that Mars once had a climate different from today, and so changes in river deposits with time tell us something about how Mars climate changed with time. In this study, we focus in on one sedimentary basin – Aeolis Dorsa – which contains an exceptionally high number of exceptionally well-preserved river deposits that appear to have [...]
Mechanical models to estimate the paleostress state from igneous intrusions
Published: 2018-03-09
Subjects: Earth Sciences, Geology, Physical Sciences and Mathematics, Tectonics and Structure, Volcanology
Dikes and sills represent an important component of the deformation history in volcanic systems, but unlike dikes, sills are typically omitted from traditional paleostress analyses in tectonic studies. The emplacement of sheet intrusions is commonly associated with mode I fracturing in a low deviatoric stress state, where dilation is perpendicular to the fracture plane. Many natural examples of [...]
Climatic influences on the offset between d18O of cave drip waters and precipitation inferred from global monitoring data
Published: 2018-03-09
Subjects: Earth Sciences, Engineering, Environmental Monitoring, Environmental Sciences, Geochemistry, Hydrology, Physical Sciences and Mathematics, Speleology
We present a meta-analysis of data from 22 caves and 96 drip sites from 4 continents where both the cave drip water d18O and the weighted mean d18O of precipitation have been measured. Drip water d18O is similar to the weighted mean d18O of precipitation (within ± 0.3 ‰) for sites where mean annual temperature (MAT) is less than 15 °C (85% of drips where MAT < 15 °C) and an aridity index [...]
Uncertainty in sea level rise projections due to the dependence between contributors
Published: 2018-03-08
Subjects: Applied Statistics, Climate, Earth Sciences, Environmental Sciences, Oceanography and Atmospheric Sciences and Meteorology, Physical Sciences and Mathematics, Probability, Statistical Models, Statistics and Probability
Sea level rises at an accelerating pace threatening coastal communities all over the world. In this context sea level projections are key tools to help risk mitigation and adaptation. Sea level projections are often made using models of the main contributors to sea level rise (e.g. thermal expansion, glaciers, ice sheets...). To obtain the total sea level these contributions are added, therefore [...]
Is fine sediment in sandy riverbed deposits a proxy for paleo-sediment supply?
Published: 2018-03-04
Subjects: Earth Sciences, Geology, Geomorphology, Physical Sciences and Mathematics, Sedimentology, Stratigraphy
The amount of silt and clay supplied to rivers can be a primary control on the form and dynamics of channel networks, and it affects the distribution and interconnectedness of buried fluvial reservoirs. Despite its importance, it is difficult to reconstruct how much fine sediment was supplied to ancient rivers. The presence of silt and clay accumulations in sandy river deposits is often [...]
Redefining ‘Clean’ Sand By Integrating Field And Laboratory Data On Mixed Sand–Clay–EPS Rippled-Bed Transport
Published: 2018-03-02
Subjects: Earth Sciences, Physical Sciences and Mathematics, Sedimentology
The shape and size of sedimentary bedforms play a key role in the reconstruction of sedimentary processes in modern and ancient environments. Recent laboratory experiments have shown that bedforms in mixed sand–clay develop at a slower rate and often have smaller heights and lengths than equivalent bedforms in pure sand. This is generally attributed to cohesive forces that can be of physical [...]
Revisiting the crustal structure and kinematics of the Central Andes at 33.5°S : implications for the mechanics of Andean mountain-building
Published: 2018-03-02
Subjects: Earth Sciences, Physical Sciences and Mathematics, Tectonics and Structure
The Andean belt is the only present-day active case example of a subduction-type orogeny. However, an existing controversy opposes classical views of Andean growth as an east-verging retro-wedge, against a recently proposed bi-vergent model involving a primary west-vergent crustal-scale thrust synthetic to the subduction. We examine these diverging views by quantitatively re-evaluating the orogen [...]
Radiative feedbacks from stochastic variability in surface temperature and radiative imbalance
Published: 2018-03-02
Subjects: Climate, Earth Sciences, Oceanography and Atmospheric Sciences and Meteorology, Physical Sciences and Mathematics
Estimates of radiative feedbacks obtained by regressing fluctuations in top-of-atmosphere (TOA) energy imbalance and surface temperature depend critically on assumptions about the nature of the stochastic forcing and on the sampling interval. Here we develop an energy-balance framework that allows us to model the different contributions of stochastic atmospheric and oceanic forcing on feed- back [...]
A faithful record of channel mouth bifurcation angles in river delta stratigraphy on Earth and Mars
Published: 2018-03-01
Subjects: Earth Sciences, Geology, Geomorphology, Physical Sciences and Mathematics, Sedimentology, Stratigraphy
Which geomorphologic features of sedimentary systems persist into the stratigraphic record? In modern river deltas, channel mouth bifurcation angles have been shown to be consistent with network growth in a Laplacian flow field proximal to the channel margins. This results in a characteristic bifurcation angle of 72 . However, the persistence of this formative angle through channel evolution and [...]
Tracking Groundwater Levels using the Ambient Seismic Field
Published: 2018-02-27
Subjects: Earth Sciences, Geophysics and Seismology, Hydrology, Physical Sciences and Mathematics
Aquifers are vital groundwater reservoirs for residential, agricultural, and industrial activities worldwide. Tracking their state with high temporal and spatial resolution is critical for water resource management at the regional scale yet is rarely achieved from a single dataset. Here, we show that variations in groundwater levels can be mapped using perturbations in seismic velocity (dv/v). [...]