Open Access. Powered by Scholars. Published by Universities.®
- Discipline
- Publication Type
Articles 1 - 4 of 4
Full-Text Articles in Geology
Three-Dimensional Intrusion Geometries In The Monogenetic San Rafael (Utah) Sub-Volcanic Field Revealed By Nonlinear Inversion Of Magnetic Anomaly Data, Troy A. Berkey
USF Tampa Graduate Theses and Dissertations
Distributed volcanic fields are common on Earth and nearby planetary bodies. Unlike their central-vent counterparts, these volcanic centers are comprised of many individual basaltic magmatic dikes, which are often only expressed at the surface in the form of vents, domes, and lava flows. In situ imaging of the shallow (<1 km) subsurface can reveal important details about the 3D geometry of fissure systems that feed distributed eruptive centers, with implications for the nature of these eruptions: their mass flow rates, explosivity, durations, and volcanotectonic interaction. Luckily, dikes, sills, conduits and related near-surface structures tend to carry high remnant magnetizations, creating magnetic anomalies at the surface where sufficient magnetic contrast exists with the host rocks they intrude. In the San Rafael Sub-volcanic field (SRSVF), basaltic dikes intrude fractured and horizontally bedded Jurassic sandstones, now eroded to a depth of about 800 m beneath the paleo-surface. Detailed mapping and profiles with a Cs-vapor magnetometer reveal far more complex anomalies than can be attributed to simple planar dikes, including: sills, buds, and domes. We image these geometries using MagCube-parallel, an open-source nonlinear inversion code we developed that models complex geometry with multiple (<= 1,000) vertical-sided prisms. I show one normally polarized fissure system to include along strike: An ~3-14 m thick, ~50 m wide dome-like feature or laccolith at depths of ~9-20 m, a roughly vertical conduit ~15 m thick, ~36-50 m wide, at ~1-16 m depth near the center of the mapped fissure-like system, and a ~8-48 m. wide dike at ~2-17 m depth that is <1-6 m thick, with reducing magnitude northward. While model depth and thickness vary with magnetization contrast, the main geometric relationships do not. Magnetic mapping of a nearby fissure reveals the same types of structures. The implication of these structures is that the small-volume fissure eruptions were likely pulsatory, with episodes of horizontal intrusion of sills, and sufficient time to develop gravitational instabilities.
Integrated Approach For Sinkhole Evaluation And Evolution Prediction In The Central Ebro Basin (Ne Spain), Oscar Pueyo Anchuela, Andrés Pocoví Juan, Antonio M. Casas Sainz, Javier Gracia Abadias, Carlos L. Liesa Carrera
Integrated Approach For Sinkhole Evaluation And Evolution Prediction In The Central Ebro Basin (Ne Spain), Oscar Pueyo Anchuela, Andrés Pocoví Juan, Antonio M. Casas Sainz, Javier Gracia Abadias, Carlos L. Liesa Carrera
International Journal of Speleology
Evaluation of karst hazards benefits from the integration of different techniques, methodologies and approaches. Each one presents a different signature and is sensitive to certain indicators related to karst hazards. In some cases, detailed analysis permits the evaluation of representativeness either from isolated approaches or by means of integrated analyses. In this study, we present the evaluation of an area with high density of karstic collapses at different evolutionary stages through the integration of surficial, historical, geomorphological and geophysical data in order to finally define the evolutionary model for karst activity development. The obtained dataset permits to identify different steps …
2d And 3d Imaging Of The Metamorphic Carbonates At Omalos Plateau/Polje, Crete, Greece By Employing Independent And Joint Inversion On Resistivity And Seismic Data, Hamdan Ali Hamdan Dr, Nikos Economou, Giorgos Kritikakis, Nikos Andronikidis, Emmanuil Manoutsoglou, Antonis Vafidis, Pangratis Pangratis, Georgina Apostolidou
2d And 3d Imaging Of The Metamorphic Carbonates At Omalos Plateau/Polje, Crete, Greece By Employing Independent And Joint Inversion On Resistivity And Seismic Data, Hamdan Ali Hamdan Dr, Nikos Economou, Giorgos Kritikakis, Nikos Andronikidis, Emmanuil Manoutsoglou, Antonis Vafidis, Pangratis Pangratis, Georgina Apostolidou
International Journal of Speleology
A geophysical survey carried out at Omalos plateau in Chania, Western Crete, Greece employed seismic as well as electrical tomography methods in order to image karstic structures and the metamorphic carbonates (Tripali unit and Plattenkalk group) which are covered by post-Mesozoic deposits (terra rossa, clays, sands and gravels). The geoelectrical sections image the metamorphic carbonates which exhibit a highly irregular relief. At the central part of the plateau the thickness of post-Mesozoic deposits (terra rossa, clays, sands and gravels) ranges from 40-130 m. A 3D resistivity image was generated by inverting resistivity data collected on a grid to the south …
Quasi 3-Dimensional Electrical Resistivity Mapping Of Air-Filled Karst Conduits And Policy Implications, Charles W. Mccrackin
Quasi 3-Dimensional Electrical Resistivity Mapping Of Air-Filled Karst Conduits And Policy Implications, Charles W. Mccrackin
USF Tampa Graduate Theses and Dissertations
This study assesses the capability and practical applications of quasi 3-Dimensional (3D) electrical resistivity surveying (ER) for mapping air-filled karst conduits. Vadose zone caves within the Brooksville Ridge of West Central Florida are relatively similar in architecture, with N-S elongation, and do not consist of an interconnected network of conduits. A high resolution quasi-3D ER survey was performed over two mapped cave systems on the Brooksville Ridge. The resultant survey verified the general effectiveness of quasi-3D ER in locating the two known near-surface cave features. Several other locations in the survey show similar or stronger resistivity anomalies trending in a …