Preprints
Filtering by Subject: Geology
Global dominance of tectonics over climate in shaping river longitudinal profiles
Published: 2020-03-18
Subjects: Earth Sciences, Geology, Geomorphology, Hydrology, Physical Sciences and Mathematics, Tectonics and Structure
River networks are striking features engraved into Earths surface, shaped by uplift and erosion under the joint influence of climate and tectonics. How a river descends along its course – its longitudinal profile – varies greatly from one basin to the next, reflecting the interplay between uplift and erosional processes. It has recently been argued that climatic aridity should be a first-order [...]
Dynamic recrystallisation can produce porosity in shear zones
Published: 2020-03-18
Subjects: Earth Sciences, Geology, Physical Sciences and Mathematics, Tectonics and Structure
Creep cavities are increasingly recognised as an important syn-kinematic feature of shear zones but much about this porosity needs investigation. Largely, observations of creep cavities are restricted to very fine grained mature ultramylonites and it is unclear when they developed during deformation. Specifically, a question that needs testing is; should grain-size reduction during deformation [...]
Global inventories of inverted stream channels on Earth and Mars
Published: 2020-03-03
Subjects: Earth Sciences, Geology, Geomorphology, Physical Sciences and Mathematics
Data from orbiting and landed spacecraft have provided vast amounts of information regarding fluvial and fluvial-related landforms and sediments on Mars. One variant of these landforms are sinuous ridges that have been interpreted to be remnant evidence for ancient fluvial activity, observed at hundreds of martian locales. In order to further understanding of these martian landforms, this paper [...]
Magma diversity reflects recharge regime and thermal structure of the crust
Published: 2020-03-03
Subjects: Earth Sciences, Geochemistry, Geology, Physical Sciences and Mathematics, Volcanology
The chemistry of magmas erupted by volcanoes is a message from deep within the Earth’s crust, which if decrypted, can provide essential information on magmatic processes occurring at inaccessible depths. While some volcanoes are prone to erupt magmas of a wide compositional variety, others sample rather monotonous chemistries through time. Whether such differences are a consequence of physical [...]
Pre-inversion normal fault geometry controls inversion style and magnitude, Farsund Basin, offshore southern Norway
Published: 2020-02-28
Subjects: Earth Sciences, Geology, Physical Sciences and Mathematics, Tectonics and Structure
Inversion may localise along pre-existing structures within the lithosphere, far from the plate boundaries along which the causal stress is greatest. Inversion style and magnitude is expressed in different ways, depending on the geometric and mechanical properties of the pre-existing structure. A three-dimensional approach is thus required to understand how inversion may be partitioned and [...]
Structural inheritance and border fault reactivation during active early-stage rifting along the Thyolo fault, Malawi
Published: 2020-02-26
Subjects: Earth Sciences, Geology, Geomorphology, Physical Sciences and Mathematics, Tectonics and Structure
We present new insights on the geometry, initiation and growth of the Thyolo fault, an 85 km long active border fault in the southern Malawi Rift, from high-resolution topography, field and microstructural observations. The Thyolo fault is located towards the edge of the Proterozoic Unango Terrane, and is the border fault of the Lower Shire Graben, which has experienced four phases of extension [...]
Using computer-aided image processing to estimate chemical composition of igneous rocks: A potential tool for large-scale compositional mapping
Published: 2020-02-20
Subjects: Earth Sciences, Geochemistry, Geology, Physical Sciences and Mathematics
Digital cameras, particularly on smartphones, have led to the proliferation of amateur photographers. Of interest here is the use of smartphone cameras to conduct rapid, low-cost compositional mapping of geologic bedrock, such as plutons and batholiths, in combination with chemical analyses of rocks in the laboratory. This paper discusses some of the challenges in geochemical mapping using image [...]
New composite bio- and isotope stratigraphies spanning the Middle Eocene Climatic Optimum at tropical ODP Site 865 in the Pacific Ocean
Published: 2020-02-20
Subjects: Earth Sciences, Geology, Paleontology, Physical Sciences and Mathematics, Stratigraphy
The Middle Eocene Climatic Optimum (MECO) at ca. 40 Ma is one of the largest of the transient Eocene global warming events. However, it is relatively poorly known from tropical settings as few sites span the entirety of the MECO event and/or host calcareous microfossils, which are the dominant proxy carrier. Ocean Drilling Program (ODP) Pacific Ocean Site 865 in the low-latitude North Pacific [...]
Evolution of a mixed siliciclastic-carbonate deep-marine system on an unstable margin: the Cretaceous of the Eastern Greater Caucasus, Azerbaijan
Published: 2020-02-20
Subjects: Earth Sciences, Geology, Physical Sciences and Mathematics
Mixed siliciclastic-carbonate deep-marine systems (mixed systems) are less documented in the geological record than pure siliciclastic systems. The similarities and differences between these systems are therefore poorly understood. A well-exposed Late Cretaceous mixed system on the northern side of the Eastern Greater Caucasus (EGC), Azerbaijan, provides an opportunity to study the interaction [...]
Evidence of recurrent mass movement in front of the maximum slip area of the 1960 Chile earthquake: Implications for risk assessment and paleoseismology
Published: 2020-02-20
Subjects: Earth Sciences, Geology, Geomorphology, Geophysics and Seismology, Physical Sciences and Mathematics
We present evidence that suggests a new risk scenario for the Valdivia basin in south Chile, located in the area of the magnitude 9.5 1960 earthquake. In 1960, three mass movements, triggered by the earthquake shaking, dammed the upper course of the San Pedro River and threatened Valdivia City until it was opened in a controlled manner by its inhabitants. Published historical accounts indicate [...]
Constraints on mantle viscosity and Laurentide ice sheet evolution from pluvial paleolake shorelines in the western United States
Published: 2020-02-12
Subjects: Earth Sciences, Geology, Geophysics and Seismology, Physical Sciences and Mathematics
The deformation pattern of the paleoshorelines of extinct Lake Bonneville were among the first features to indicate that Earths interior responds viscoelastically to changes in surface loads (Gilbert, 1885). Here we revisit and extend this classic study of isostatic rebound with updated lake chronologies for Lake Bonneville and Lake Lahontan as well as revised elevation datasets of shoreline [...]
Chalcophile elements track the fate of sulfur at Kīlauea Volcano, Hawai’i
Published: 2020-02-08
Subjects: Earth Sciences, Geochemistry, Geology, Physical Sciences and Mathematics, Volcanology
Chalcophile element concentrations in melt inclusions and matrix glasses may be used to investigate low pressure degassing processes, as well as sulfide saturation during crustal fractionation, and mantle melting. Erupted products from Kīlauea Volcano, Hawaiʻi, record three stages of sulfide saturation (in the mantle, crust, and within lava lakes), separated by episodes of sulfide resorption [...]
A new model for fault growth during syn-kinematic deposition
Published: 2020-02-04
Subjects: Earth Sciences, Geology, Physical Sciences and Mathematics, Tectonics and Structure
Constraining the mechanisms of fault growth is essential for understanding extensional tectonics. In these dynamic systems the propagation of existing faults through recent syn-kinematic depositions is a poorly understood yet critical process. To understand how underlying structures influence faulting, we examine fault growth in a 10 kyr magmatically-resurfaced region of the Krafla fissure swarm, [...]
Entangled external and internal controls on submarine fan evolution: an experimental perspective
Published: 2020-02-02
Subjects: Earth Sciences, Geology, Geomorphology, Physical Sciences and Mathematics, Sedimentology, Stratigraphy
Submarine fans are formed by sediment-laden flows shed from continental margins into ocean basins. Their morphology represents the interplay of external controls such as tectonics, climate, and sea-level with internal processes including channel migration and lobe compensation. However, the nature of this interaction is poorly understood. We used physical modelling to represent the evolution of a [...]
Integrating suspended sediment flux in large alluvial river channels: Application of a synoptic Rouse-based model to the Irrawaddy and Salween rivers
Published: 2020-02-02
Subjects: Earth Sciences, Geochemistry, Geology, Geomorphology, Hydrology, Physical Sciences and Mathematics, Sedimentology
A large portion of freshwater and sediment is exported to the ocean by a small number of major rivers. Many of these mega-rivers are subject to substantial anthropogenic pressures, which are having a major impact on water and sediment delivery to deltaic ecosystems. Due to hydrodynamic sorting, sediment grain size and composition varies strongly with depth and across the channel in large rivers, [...]