Preprints
There are 6976 Preprints listed.
Understanding snow hydrological processes through the lens of stable water isotopes
Published: 2017-11-07
Subjects: Earth Sciences, Environmental Sciences, Glaciology, Hydrology, Physical Sciences and Mathematics, Water Resource Management
Snowfall may have different stable isotopic compositions compared to rainfall, allowing its contribution to potentially be tracked through the hydrological cycle. This review summarizes the state of knowledge of how different hydro-meteorological processes affect the isotopic composition of snow, and, through selected examples, discusses how stable water isotopes can provide a better [...]
Collinearity assessment of geocentre coordinates derived from multi-satellite SLR data
Published: 2017-11-08
Subjects: Earth Sciences, Geophysics and Seismology, Other Earth Sciences, Physical Sciences and Mathematics
Of the three satellite geodetic techniques contributing to the International Terrestrial Reference Frame (ITRF), Satellite Laser Ranging (SLR) is generally held to provide the most reliable time series of geocentre coordinates and exclusively defines the ITRF origin. Traditionally, only observations to the two LAser GEOdynamics Satellite (LAGEOS) and Etalon pairs of satellites have been used for [...]
Sequential growth of deformation bands in carbonate grainstones in the hangingwall of an active growth fault: Implications for deformation mechanisms in different tectonic regimes
Published: 2017-11-07
Subjects: Earth Sciences, Geology, Physical Sciences and Mathematics, Tectonics and Structure
Deformation bands in porous sandstones have been extensively studied for four decades, whereas comparatively less is known about deformation bands in porous carbonate rocks, particularly in extensional settings. Here, we investigate porous grainstones of the Globigerina Limestone Formation in Malta, which contain several types of deformation bands in the hangingwall of the Maghlaq Fault: (i) [...]
Pastoralism may have delayed the end of the green Sahara
Published: 2017-11-06
Subjects: Earth Sciences, Environmental Studies, Geology, Physical Sciences and Mathematics, Social and Behavioral Sciences
The benefits of pastoralism for marginal, arid environments are often not appreciated. One notable past example of the human response to encroaching desertification comes from the regional climate deterioration after the most recent African Humid Period, which ended around 5,500 years ago. Recent evidence points to a population expansion in northern Africa prior to this, associated with the [...]
Rifts and Rifted Margins: A Review of Geodynamic Processes and Natural Hazards
Published: 2017-11-06
Subjects: Earth Sciences, Geology, Other Earth Sciences, Physical Sciences and Mathematics, Tectonics and Structure
This review provides an introduction to the geodynamic processes that influence tectonic rift evolution and rifted margin architecture. With a strong focus on numerical modeling, I summarize classical and recent insights on rift evolution with differentiation between 2D and 3D concepts and models. One of the key processes during rift evolution is crust-mantle coupling, which controls not only the [...]
Duration and nature of the end-Cryogenian (Marinoan) glaciation
Published: 2017-11-05
Subjects: Earth Sciences, Geology, Physical Sciences and Mathematics, Stratigraphy
The end-Cryogenian glaciation (Marinoan) is portrayed commonly as the archetype of snowball Earth, yet its duration and character remain uncertain. Here we report U-Pb zircon ages for two ash beds from widely separated localities of the Marinoan-equivalent Ghaub Formation in Namibia: 639.29 ± 0.26 Ma and 635.21 ± 0.59 Ma. These findings verify, for the first time, the key prediction of the [...]
Controls of inherited lithospheric heterogeneity on rift linkage: Numerical and analog models of interaction between the Kenyan and Ethiopian rifts across the Turkana depression
Published: 2017-11-06
Subjects: Earth Sciences, Geology, Physical Sciences and Mathematics, Tectonics and Structure
Inherited rheological structures in the lithosphere are expected to have large impact on the architecture of continental rifts. The Turkana depression in the East African Rift connects the Main Ethiopian Rift to the north with the Kenya rift in the south. This region is characterized by a NW-SE trending band of thinned crust inherited from a Mesozoic rifting event, which is cutting the [...]
Evaluating uncertainties in the calibration of isotopic reference materials and multi-element isotopic tracers (EARTHTIME Tracer Calibration Part II)
Published: 2017-11-05
Subjects: Earth Sciences, Physical Sciences and Mathematics
A statistical approach to evaluating uncertainties in the calibration of multi-element isotopic tracers has been developed and applied to determining the isotopic composition of mixed U-Pb (202Pb-205Pb-233U-235U) tracers used for accurate isotope dilution U-Pb geochronology. Our experiment, part of the EARTHTIME initiative, directly links the tracer calibration to first-principles measurements [...]
Seismotectonics of a diffuse plate boundary: Observations off the Sumatra-Andaman trench
Published: 2017-11-05
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
Seismic slip extends from maximum expected depth through the crust in 45-75 Ma oceanic lithosphere in the Indo-Australian intraplate region off the Sumatra-Andaman trench. Large (magnitude greater than 7) strike-slip earthquakes in this region can rupture multiple differently oriented faults. Rupture directivity modeling provides tentative support for active east-west oriented faults.
Data quality of collocated portable broadband seismometers using direct burial and vault emplacement
Published: 2017-11-05
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
Temporary broadband sensor deployments have traditionally been predominantly emplaced using shallow vaults that require more materials, personnel, and time than direct burial. However, new developments in seismometer and seismograph technology are increasingly facilitating systems that can be directly buried in earth or snow without vault enclosures. We analyze data from two identical shallow [...]
Magmatic Densities Control Erupted Volumes in Icelandic Volcanic Systems
Published: 2017-11-05
Subjects: Earth Sciences, Physical Sciences and Mathematics, Volcanology
The control of magmatic physical properties on the range and volumetric distribution of eruptions has been investigated for the active volcanic zones of Iceland. Magmatic density and viscosity both exert control over observed erupted volumes. The largest volume of erupted material sits at a density and viscosity minimum corresponding to the composition of basalts at the arrival of plagioclase on [...]
Constraints on the numerical age of the Paleocene‐Eocene boundary
Published: 2017-11-05
Subjects: Earth Sciences, Geochemistry, Geology, Physical Sciences and Mathematics, Stratigraphy
Here we present combined radioisotopic dating (U-Pb zircon) and cyclostratigraphic analysis of the carbon isotope excursion at the Paleocene-Eocene (P-E) boundary in Spitsbergen to determine the numerical age of the boundary. Incorporating the total uncertainty from both radioisotopic and cyclostratigraphic data sets gives an age ranging from 55.728 to 55.964 Ma, within error of a recently [...]
Multiple Palaeoproterozoic carbon burial episodes and excursions
Published: 2017-11-05
Subjects: Earth Sciences, Geochemistry, Geology, Physical Sciences and Mathematics, Stratigraphy
Organic-rich rocks (averaging 2–5% total organic carbon) and positive carbonate-carbon isotope excursions ( ‰ δC13>+5‰ and locally much higher, i.e. the Lomagundi-Jatuli Event) are hallmark features of Palaeoproterozoic successions and are assumed to archive a global event of unique environmental conditions following the c. 2.3 Ga Great Oxidation Event. Here we combine new and published [...]
Dating the termination of the Palaeoproterozoic Lomagundi-Jatuli carbon isotopic event in the North Transfennoscandian Greenstone Belt
Published: 2017-11-05
Subjects: Earth Sciences, Geochemistry, Geology, Physical Sciences and Mathematics, Stratigraphy
Existing radio-isotopic age constraints indicate that the global Palaeoproterozoic Lomagundi-Jatuli large, positive carbonate carbon isotopic excursion, with δ13C values >+5‰, occurred between 2.2 and 2.06 Ga. In the North Transfennoscandian Greenstone Belt of the Kola Peninsula, NW Russia, northern Norway and Finland, the Lomagundi-Jatuli Event is recorded in the carbonate rocks of the Umba [...]
A users guide to Neoproterozoic geochronology
Published: 2017-11-05
Subjects: Earth Sciences, Geochemistry, Geology, Paleontology, Physical Sciences and Mathematics, Stratigraphy
Geochronology is essential for understanding Neoproterozoic Earth history. Here we review the types of rocks and minerals that are used to date geologic events and the analytical protocols for the different radio-isotopic decay systems employed. We discuss the limitations and potential of these methodologies for dating Neoproterozoic stratigraphy, highlighting the major sources and magnitudes of [...]