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Sand Compositional Analysis Using a Combined Geological and Spectroscopic Approach
Title
Sand Compositional Analysis Using a Combined Geological and Spectroscopic Approach.
Creator
Smith, Molly E., Oleinik, Anton E., Zhang, Caiyun, Florida Atlantic University, Charles E. Schmidt College of Science, Department of Geosciences
Abstract/Description
Many minerals, such as calcite and magnetite, show diagnostic overtone and combination bands in the 350-2500 nm window. Sand, though an important unconsolidated material with great abundance on the Earth’s surface, is largely overlooked in spectroscopic studies. Over 100 sand samples were analyzed through traditional microscopic methods and compared to spectral reflectance collected via an ASD Spectroradiometer. Multiple methods were chosen to compare spectroscopic data to sand composition...
Show moreMany minerals, such as calcite and magnetite, show diagnostic overtone and combination bands in the 350-2500 nm window. Sand, though an important unconsolidated material with great abundance on the Earth’s surface, is largely overlooked in spectroscopic studies. Over 100 sand samples were analyzed through traditional microscopic methods and compared to spectral reflectance collected via an ASD Spectroradiometer. Multiple methods were chosen to compare spectroscopic data to sand composition and grain size: 1) existing spectral indices, 2) continuum removal, 3) derivative analysis, and 4) correlation analysis. Particular focus was given to carbonate content. Results from derivative and correlation analysis showed strong correlations in the 2180-2240 nm and 2300-2360 nm windows to carbonate content. Proposed here is the Normalized Difference Carbonate Sand Index (NDCSI), which showed Pearson correlations of r=-0.78 for light-colored samples and r=-0.77 for all samples used. This index is viable for use with carbonate-rich sands.
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Date Issued
2016
PURL
http://purl.flvc.org/fau/fd/FA00004634
Subject Headings
Physical geology., Environmental geology., Coast changes--Analysis., Beach erosion., Sand--Optical properties., Spectrophotometry.
Format
Document (PDF)
Multi-scale characterization of dissolution structures and porosity distribution in the upper part of the Biscayne aquifer using ground penetrating radar (GPR)
Title
Multi-scale characterization of dissolution structures and porosity distribution in the upper part of the Biscayne aquifer using ground penetrating radar (GPR).
Creator
Mount, Gregory J., Comas, Xavier, Florida Atlantic University, Charles E. Schmidt College of Science, Department of Geosciences
Abstract/Description
The karst Biscayne aquifer is characterized by a heterogeneous spatial arrangement of porosity, making hydrogeological characterization difficult. In this dissertation, I investigate the use of ground penetrating radar (GPR), for understanding the spatial distribution of porosity variability in the Miami Limestone presented as a compilation of studies where scale of measurement is progressively increased to account for varying dimensions of dissolution features. In Chapter 2, GPR in zero...
Show moreThe karst Biscayne aquifer is characterized by a heterogeneous spatial arrangement of porosity, making hydrogeological characterization difficult. In this dissertation, I investigate the use of ground penetrating radar (GPR), for understanding the spatial distribution of porosity variability in the Miami Limestone presented as a compilation of studies where scale of measurement is progressively increased to account for varying dimensions of dissolution features. In Chapter 2, GPR in zero offset acquisition mode is used to investigate the 2-D distribution of porosity and dielectric permittivity in a block of Miami Limestone at the laboratory scale (< 1.0 m). Petrophysical models based on fully saturated and unsaturated. water conditions are used to estimate porosity and solid dielectric permittivity of the limestone. Results show a good correspondence between analytical and GPR-based porosity estimates and show variability between 22.0-66.0 %. In Chapter 3, GPR in common offset and common midpoint acquisition mode are used to estimate bulk porosity of the unsaturated Miami Limestone at the field scale (10.0-100.0 m). Estimates of porosity are based on the assumption that the directly measured water table reflector is flat and that any deviation is attributed to changes in velocity due to porosity variability. Results show sharp changes in porosity ranging between 33.2-60.9 % attributed to dissolution areas. In Chapter 4, GPR in common offset mode is used to characterize porosity variability in the saturated Biscayne aquifer at 100-1000 m field scales. The presence of numerous diffraction hyperbolae are used to estimate electromagnetic wave velocity and asses both horizontal and vertical changes in porosity after application of a petrophysical model. Results show porosity variability between 23.0-41.0 % and confirm the presence of isolated areas that could serve as enhanced infiltration or recharge. This research allows for the identification and delineation areas of macroporosity areas at 0.01 m lateral resolution and shows variability of porosity at different scales, reaching 37.0 % within 1.3 m, associated with areas of enhanced dissolution. Such improved resolution of porosity estimates can benefit water management efforts and transport modelling and help to better understand small scale relationships between ground water and surface water interactions.
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Date Issued
2014
PURL
http://purl.flvc.org/fau/fd/FA00004143
Subject Headings
Ground penetrating radar, Limestone -- Florida -- Miami Dade County -- Analysis, Physical geology, Sedimentary basins -- Florida -- Biscayne Aquifer, Sedimentation analysis
Format
Document (PDF)