Preprints
Filtering by Subject: Geology
Transgression–regression cycles drive correlations in Ediacaran–Cambrian rock and fossil records
Published: 2023-11-07
Subjects: Earth Sciences, Geology, Paleontology, Physical Sciences and Mathematics, Sedimentology, Statistical Methodology, Statistics and Probability, Stratigraphy
Strata of the Ediacaran Period (635–538.8 Ma) yield the oldest known fossils of complex, macroscopic organisms in the geologic record. These “Ediacaran-type” macrofossils (known as the Ediacaran biota) first appear in mid-Ediacaran strata, experience an apparent decline through the terminal Ediacaran, and directly precede the Cambrian (538.8–485.4 Ma) radiation of animals. Existing hypotheses for [...]
Petrological Evolution and Mass Redistribution in Basaltic Fault Zones: An Example from the Faroe Islands, North Atlantic Igneous Province
Published: 2023-11-06
Subjects: Earth Sciences, Geochemistry, Geology, Tectonics and Structure
Fault rock petrology exerts an important control on the permeability structure and mechanical properties of fault zones. Slip-related deformation on upper-crustal faults in basaltic rocks is closely associated with fluid-rock interaction, altering the distribution of physical properties within the fault. Here we present quantitative descriptions of the geochemical and petrological evolution of [...]
Observations of beach cusp morphodynamics on a composite beach
Published: 2023-11-02
Subjects: Geology, Geomorphology
Substantial volumes of sediment are moved on coarse grained beaches through the formation and destruction of beach cusps, yet the processes governing cusp behaviour remain poorly understood. Here, we combine continuous 2D LiDAR scan data with daily UAV topographic surveys and RGB imagery to provide detailed morphological measurements of beach cusps on a composite beach with the aim to investigate [...]
Quantifying fault interpretation uncertainties and their impact on fault seal and seismic hazard analysis
Published: 2023-10-31
Subjects: Geology, Tectonics and Structure
Fault-horizon cut-off data extracted from seismic reflection datasets are used to study normal fault geometry, displacement distribution, and growth history. We assess the influence of three seismic interpretation factors (repeatability, measurement obliquity, and fault cut-off type) on fault parameter uncertainty. Two repeat interpretations resulted in mean differences of 5-15% for throw, 11-42% [...]
New insights into the Upper Pleistocene directed blast eruption, Popocatépetl volcano, México
Published: 2023-10-30
Subjects: Geology, Stratigraphy, Volcanology
Volcanic eruptions of the directed blast type are characterized by powerful explosions with a significant lateral pyroclastic density current (PDC) component that can travel at speeds above 100 m s–1 and affect hundreds of square kilometers around a volcano. This study presents preliminary results of a detailed fieldwork and stratigraphic study of deposits associated with the Ocoxaltepec Blast [...]
Sediment supply controls on Early Eocene delta sequences (South Pyrenean Foreland Basin; Spain)
Published: 2023-10-13
Subjects: Climate, Geochemistry, Geology, Sedimentology, Stratigraphy
Sediment supply variations are often overlooked when interpreting depositional sequences, which tend to emphasize changes in accommodation. Here, we focus on a temporally well-constrained shallow-marine succession in the South Pyrenean Foreland Basin to test the control of sediment supply on the development of deltaic sequences during the Early Eocene. We analyzed the paleoenvironmental record [...]
The Heavy Mineral Map of Australia Project: A Novel, Rapid, Automated Quantitative Mineralogy Workflow
Published: 2023-10-11
Subjects: Earth Sciences, Geochemistry, Geology, Physical Sciences and Mathematics
The Heavy Mineral Map of Australia (HMMA) is the world’s first project aiming to define a continental heavy mineral baseline. It utilises a novel sample processing workflow and automated mineralogy techniques to rapidly generate and analyse mineralogical data from 1315 archived samples of catchment outlet sediments collected from 1186 catchments across the Australian continent. Heavy [...]
Continental scale hydrostratigraphy: comparing geologically informed data products to analytical solutions
Published: 2023-09-12
Subjects: Civil and Environmental Engineering, Geology, Hydrology
This study synthesizes two different methods for estimating hydraulic conductivity (K) at large scales. We derive analytical approaches that estimate K and apply them to the contiguous US. We then compare these analytical approaches to three-dimensional, national gridded K data products and three transmissivity (T) data products developed from publicly available sources. We evaluate these data [...]
The Role of Normal Fault Growth History in Influencing Fault Seal Potential, Samson Dome, Offshore Norway
Published: 2023-09-02
Subjects: Geology
The growth of normal faults can influence subsurface fluid flow and entrapment within rift basins. However, fault seal studies typically view faults as static structures, with their growth and the potential related temporal changes in hydraulic properties being ignored. In this study, we use borehole data and a high-quality 3D full-stack depth migrated seismic reflection volume to analyse the [...]
Full-waveform inversion as a tool to predict fault zone properties
Published: 2023-09-02
Subjects: Geology
Understanding the physical properties of fault zones is essential for various subsurface applications, including carbon capture and geologic storage, geothermal energy, and seismic hazard assessment. Despite improvements in fault imaging and visualisation, predicting the physical properties of faults and fault zones in the subsurface remains challenging, even with high-quality seismic reflection [...]
Generation of LOMU type alkali basalts in East Asia by melting and melt metasomatism of the asthenospheric mantle by a Paleoproterozoic subducted slab component
Published: 2023-08-30
Subjects: Geochemistry, Geology, Volcanology
The origin of alkali basalts with distinctive time-integrated low U/Pb (low µ, LOMU) from East Asia is controversial due to the complex geochemical and tectonic signatures reported from this region. We report new data on the petrology and geochemistry of the Higashi-Matsuura and Kita-Matsuura alkali basalts from southwest Japan, which confirm the presence of a LOMU-type mantle component below the [...]
Garnet zoning patterns record multiple processes of chemical transfer during subduction
Published: 2023-08-24
Subjects: Geology, Other Earth Sciences
Subduction facilitates the transfer of volatiles from the Earth’s surface to its interior. However, the rock-scale processes that govern the efficiency of deep volatile transfer are not fully understood. Garnets from subduction zone rocks commonly have fine-scale, oscillatory elemental zoning that is typically considered to record external fluid ingress/transfer. Elemental and oxygen-isotope [...]
Spontaneous Unsteadiness and Sorting in Pyroclastic Density Currents and their Deposits
Published: 2023-08-22
Subjects: Geology, Sedimentology, Stratigraphy, Volcanology
Pyroclastic density currents (PDCs) pose substantial risk to populations living on and around active volcanoes, but their structure and internal dynamics are poorly understood. Much of this understanding is derived from interpretation of their widespread deposits. Scaled experiments are able to probe different conditions, to explore how changing flow dynamics relate to the wide variety of [...]
Generation of evolving plate boundaries and toroidal flow from visco-plastic damage-rheology mantle convection and continents
Published: 2023-08-17
Subjects: Geology, Geophysics and Seismology, Tectonics and Structure
Earth's style of planetary heat transport is characterized by plate tectonics which requires rock strength to be reduced plastically in order to break an otherwise stagnant lithospheric lid, and for rocks to have a memory of past deformation to account for strain localization and the hysteresis implied by geological sutures. Here, we explore $\sim$10$^7$ Rayleigh number, visco-plastic, [...]
Eocene (50-55 Ma) greenhouse climate recorded in nonmarine rocks of San Diego, CA, USA
Published: 2023-08-08
Subjects: Chemistry, Climate, Earth Sciences, Geochemistry, Geology, Physical Sciences and Mathematics, Soil Science, Stratigraphy
Nonmarine rocks in sea cliffs of southern California store a detailed record of weathering under tropical conditions millions of years ago, where today the climate is much drier and cooler. This work examines early Eocene (~50-55 million-year-old) deeply weathered paleosols (ancient, buried soils) exposed in marine terraces of northern San Diego County, California, and uses their geochemistry and [...]