Preprints
Filtering by Subject: Earth Sciences
Early exhumation of the Frontal Cordillera (Southern Central Andes) and implications for Andean mountain-building at ~33.5°S
Published: 2019-03-13
Subjects: Earth Sciences, Geology, Physical Sciences and Mathematics, Tectonics and Structure
The Andes are the modern active example of a Cordilleran-type orogen, with mountain-building and crustal thickening within the upper plate of a subduction zone. Despite numerous studies of this emblematic mountain range, several primary traits of this orogeny remain unresolved or poorly documented. The onset of uplift and deformation of the Frontal Cordillera basement culmination of the Southern [...]
The effect of stress changes on time-dependent earthquake probabilities for the central Wasatch Fault Zone, Utah, USA.
Published: 2019-03-12
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics, Tectonics and Structure
Static and quasi-static Coulomb stress changes produced by large earthquakes can modify the probability of occurrence of subsequent events on neighboring faults. This approach is based on physical (Coulomb stress changes) and statistical (probability calculations) models, which are influenced by the quality and quantity of data available in the study region. Here, we focus on the Wasatch Fault [...]
Separating isotopic impacts of karst and in-cave processes from climate variability using an integrated speleothem isotope-enabled forward model
Published: 2019-03-12
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 [...]
Post-critical SsPmp and its Applications to Virtual Deep Seismic Sounding 2: 1D Imaging of the Crust/Mantle and Joint Constraints with Receiver Function
Published: 2019-03-12
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
Virtual Deep Seismic Sounding (VDSS) has recently emerged as a novel method to image the crust-mantle-boundary (CMB) and potentially other lithospheric boundaries. In Liu et al., 2018 (“Part 1”), we showed that the arrival time and waveform of post-critical SsPmp, the post-critical reflection phase at the CMB used in VDSS, is sensitive to multiple attributes of the crust and upper mantle. Here, [...]
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 [...]
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 [...]
Unfolding Veined Fold Limbs to Deduce a Basins Prefolding Stress State
Published: 2019-03-06
Subjects: Earth Sciences, Education, Outdoor Education, Physical Sciences and Mathematics, Tectonics and Structure
Tectonic structures that developed prior to folding, such as pre- and early-kinematic veins, hold valuable information on the stress state of the paleobasin in which these early structures formed. To derive the parental orientation of these prefolding brittle structures, folds need to “unfold.” A fold restoration methodology is presented in which fold limbs, and the structures they contain, are [...]
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 [...]
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 [...]
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 [...]