Preprints
There are 7994 Preprints listed.
Separating isotopic impacts of karst and in-cave processes from climate variability using an integrated speleothem isotope-enabled forward model
Published: 2019-03-11
Subjects: Biogeochemistry, Earth Sciences, Hydrology, Physical Sciences and Mathematics, Speleology
Speleothem δ18O values are commonly used to infer past climate variability. However, both non-linear karst hydrological processes and in-cave disequilibrium isotope fractionation are recognised and hinder the interpretation of δ18O values. In recent years, proxy system models (PSMs) have emerged to quantitatively assess the confounding effects of these processes. This study presents the first [...]
Machine Learning Reveals the State of Intermittent Frictional Dynamics in a Sheared Granular Fault
Published: 2019-03-05
Subjects: Civil and Environmental Engineering, Earth Sciences, Engineering, Geophysics and Seismology, Geotechnical Engineering, Physical Sciences and Mathematics
The seismogenic plate boundaries are presumed to behave similarly to a densely packed granular medium, where fault and blocks systems rapidly rearrange the distribution of forces within themselves, as particles do in slowly sheared granular systems. We use machine learning and show that statistical features of velocity signals from individual particles in a simulated sheared granular fault [...]
New flow relaxation mechanism explains scour fields at the end of submarine channels
Published: 2019-03-11
Subjects: Earth Sciences, Oceanography, Oceanography and Atmospheric Sciences and Meteorology, Physical Sciences and Mathematics, Sedimentology
In the ocean, particle-laden gravity flows, turbidity currents, flow in river-like channels across the ocean floor. These submarine channels funnel sediment, nutrients, pollutants and organic carbon into the ocean basins and can extend over 1,000’s of kilometers. At the end of these channels, turbidity currents lose their confinement, decelerate and deposit their sediment load. This is what we [...]
Autogenic translation and concave bank deposition in meandering rivers
Published: 2019-03-02
Subjects: Earth Sciences, Geomorphology, Physical Sciences and Mathematics, Sedimentology
Although it has long been recognized that deposition along meandering rivers is not restricted to convex banks, the consensus is that external forcing, that is, confinement by an erosion-resistant barrier, is necessary for significant concave-bank deposition to occur. Using a kinematic model of channel meandering and time-lapse satellite imagery from the Mamoré River in Bolivia, we show that [...]
Hydrodynamic control of gas-exchange velocity in small streams
Published: 2019-03-02
Subjects: Civil and Environmental Engineering, Earth Sciences, Engineering, Environmental Sciences, Fluid Dynamics, Hydraulic Engineering, Physical Sciences and Mathematics, Physics, Planetary Sciences
Gas exchange is a critical component of any biogeochemical mass balance model of dissolved gases in aquatic systems, yet the magnitude and drivers of spatial and temporal variations of air-water exchange rates in shallow streams are poorly understood. We investigated the relationships between gas exchange velocity of carbon dioxide and methane and flow hydraulics at different sections along a [...]
Direct observations of the coupling between quartz dissolution and Mg-silicate formation
Published: 2019-03-19
Subjects: Earth Sciences, Geochemistry, Geology, Physical Sciences and Mathematics
Although quartz is a stable mineral at Earth surface conditions, field samples have shown its rapid dissolution in combination with the precipitation of Mg-silicate phases. Atomic force microscopy (AFM) experiments were performed to investigate the dissolution of quartz and the precipitation of secondary phases in high-pH, Mg-rich solutions both in-situ and ex-situ. Experiments were conducted at [...]
Sustainability of the Marine Environment Towards the Anthropogenic Impacts in the Ecosystem of the Barents Sea
Published: 2019-01-25
Subjects: Ecology and Evolutionary Biology, Education, Environmental Education, Environmental Health and Protection, Environmental Indicators and Impact Assessment, Environmental Monitoring, Environmental Sciences, Environmental Studies, Geography, Life Sciences, Natural Resources and Conservation, Nature and Society Relations, Physical and Environmental Geography, Physical Sciences and Mathematics, Science and Mathematics Education, Social and Behavioral Sciences, Sustainability, Terrestrial and Aquatic Ecology, Water Resource Management
Among all Arctic seas, the Barents Sea is characterized by its unique environment and high level of the biodiversity. At the same time the Gulf Stream waters transport large amounts of pollutants in the Barents Sea bringing various contaminants and substances from the North Sea. Nowadays, there are in Timan Pechora-Carboniferous basin located in the Barents Sea with 76 oil and gas subsidies, [...]
Formation of magnesium silicate hydrate cement in nature
Published: 2019-03-19
Subjects: Earth Sciences, Geology, Physical Sciences and Mathematics, Sedimentology
Tillite lithified by magnesium silicate hydrate (M-S-H) cement has been formed at the surface of the Feragen Ultramafic Body in SE Norway. Serpentinization of olivine-rich rocks led to formation of brucite that dissolves during weathering to form a high pH (>9) Mg-rich fluid. This fluid dissolves quartz deposited by glaciers during the Weichselian glaciation. Subsequent evaporation leads to [...]
A secondary zone of uplift due to megathrust earthquakes
Published: 2019-03-11
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics, Tectonics and Structure
The 1960 M9.5 Valdivia and 1964 M9.2 Alaska earthquakes caused a decimeters-high secondary zone of uplift a few hundred kilometers landward of the trench. We analyze GPS data from the 2010 M8.8 Maule and 2011 M9.0 Tohoku-Oki earthquakes to confirm the existence of a secondary zone of uplift due to great earthquakes at the megathrust interface. This uplift varies in magnitude and location, but [...]
Zealandia’s Early Paleozoic sandstones: detrital mineralogy of the Greenland and Reefton Groups
Published: 2019-03-01
Subjects: Earth Sciences, Geology, Physical Sciences and Mathematics
New point counts of 13 Buller Terrane sandstones have been made. The results suggest a less quartzose and more lithic rich content of detrital sand grains in the Ordovician Greenland Group than indicated by an earlier published study (average Q:F:L = 58:16:26 and 23% matrix rather than 81:8:11 and 37% matrix). A low grade sedimentary-metasedimentary provenance is indicated. Detrital K-feldspar, [...]
Determining sources of placer minerals using U-Pb ages of detrital zircons: example of auriferous quartz pebble conglomerates in Otago and Southland, New Zealand
Published: 2019-03-01
Subjects: Earth Sciences, Geology, Physical Sciences and Mathematics
We have dated populations of detrital zircons in two Miocene gold-bearing quartz pebble conglomerates, one at St Bathans in Central Otago and one near Gore in Northern Southland. Both samples contain large numbers of Triassic-Permian zircon grains that indicate a source area dominated by Eastern Province Torlesse Composite Terrane protoliths. On the basis that the detrital quartz, zircon and gold [...]
Revised three-dimensional geometry of the platiniferous Hekeia Gabbro, Longwood Range, Southland
Published: 2019-03-01
Subjects: Earth Sciences, Geology, Physical Sciences and Mathematics
The Hekeia Gabbro in the Longwood Range of Southland is prospective for platinum group element mineralisation. Recently acquired geological and isotopic data, combined with reinterpreted aeromagnetic data, provide new constraints on the three dimensional extent and internal structure of the gabbro. Direct observations of in situ subvertical igneous layering give confidence that most curvilinear [...]
Cretaceous tectonics and gold mineralisation in the Otago Schist, New Zealand
Published: 2019-03-01
Subjects: Earth Sciences, Geology, Physical Sciences and Mathematics
This paper provides a regional-scale background for understanding gold-mineralising processes in the Otago Schist during the Cretaceous. At this time the schist belt was in the latter stages of formation as an accretionary complex with 2000 km strike length on the Pacific margin of Gondwana. The Otago Schist is interpreted as an exhumed accretionary wedge of structurally stacked clastic [...]
Regional geological framework of New Zealands mineral deposits
Published: 2019-03-01
Subjects: Earth Sciences, Geology, Physical Sciences and Mathematics
New Zealand is the emergent part of a 4.9 Mkm2, mainly submerged continent in the SW Pacific Ocean that was formerly part of the Gondwana supercontinent. The geology can be described in terms of two main Cambrian-Early Cretaceous basement units (Western and Eastern provinces) and a Late Cretaceous-Holocene sedimentary and volcanic cover (Zealandia Megasequence and Rūaumoko Volcanics). New Zealand [...]
The 2018-2019 seismo-volcanic crisis east of Mayotte, Comoros islands: seismicity and ground deformation markers of an exceptional submarine eruption
Published: 2019-02-28
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics, Volcanology
On May 10th, 2018, an unprecedented long and intense seismic crisis started offshore, east of Mayotte, the easternmost of the Comoros volcanic islands. The population felt hundreds of events. Over the course of one year, 32 earthquakes with magnitude greater than 5 occurred, including the largest event ever recorded in the Comoros (Mw = 5.9 on May 15th, 2018). Earthquakes are clustered in space [...]