Blanco Arrué, B. ORCID: 0000-0002-0470-3542 (2024). Multidimensional inversion of transient electromagnetic data for the exploration of clay pans in the Atacama Desert, Chile. PhD thesis, Universität zu Köln.
PDF (Thesis (PhD thesis))
Diss_BlancoArrue_2023.pdf - Accepted Version Bereitstellung unter der CC-Lizenz: Creative Commons Attribution Non-commercial. Download (184MB) |
Abstract
This thesis focuses on the geophysical exploration of selected clay pans in northern Chile, the so-called PAG and Paranal clay pans. These sedimentary deposits, are sensitive archives of the Atacama Desert paleoclimate and contain valuable information on the precipitation history. The loop source transient electromagnetic (TEM) method is used to provide the geometry and bedrock topography of each site. In addition to standard 1D inversion techniques, 2D forward modeling approaches are utilized, and a recently published 3D forward modeling and inverse scheme are applied to the TEM data. The investigated sites are study areas of the interdisciplinary Collaborative Research Center, \textit{Earth Evolution at the Dry Limit} (CRC 1211), established at the Universities of Cologne, Bonn, and Aachen. The CRC 1211 contributes to seeking the mutual evolutionary relationships between Earth's surface processes and biota under extreme water limitation. Two extensive geophysical surveys were conducted in both clay pans measuring a total of 181 TEM soundings on a 3D grid. Within the project, other geophysical techniques, such as active seismic and magnetics, were also carried out, complementing the geoscientific integrated interpretation of the subsurface. The presented thesis provides foundations for suitable drilling locations within the CRC 1211 project. The 1D inversion results reveal a three-layered resistivity structure with reliable information down to a depth of 250 m. At the PAG site, the results identify a resistive colluvial sequence increased to high conductive lacustrine sediments followed by a resistive basement. Additionally, at the Paranal clay pan, the results detect a resistive layer of fine sediment succeeded by a conductive sequence of a fluvial conglomerate with a resistive basement beneath. The subsurface models agree with lithology, borehole data, and geological information. In addition, key information is obtained with respect to the sedimentary thickness above the basement, contributing to paleoclimate research in northern Chile. A 2D forward modeling study was performed to validate the 1D interpretation and evaluate possible distortion effects. The analyzed scenarios confirm the presence of 2D effects in the data from both PAG and Paranal TEM data sets, being in the latter more strong. Aiming to obtain a more accurate and independent model, a 3D inversion of the whole Paranal TEM data is derived. The obtained 3D inversion models are in good agreement with the local geology, which validates the geometry and subsurface distribution of the studied clay pan.
Item Type: | Thesis (PhD thesis) | ||||||||||||
Translated abstract: |
|
||||||||||||
Creators: |
|
||||||||||||
URN: | urn:nbn:de:hbz:38-727212 | ||||||||||||
Date: | 3 May 2024 | ||||||||||||
Place of Publication: | Köln, Germany | ||||||||||||
Language: | English | ||||||||||||
Faculty: | Faculty of Mathematics and Natural Sciences | ||||||||||||
Divisions: | Faculty of Mathematics and Natural Sciences > Department of Geosciences > Institute for Geophysics and Meteorology | ||||||||||||
Subjects: | Earth sciences | ||||||||||||
Uncontrolled Keywords: |
|
||||||||||||
Date of oral exam: | 5 May 2023 | ||||||||||||
Referee: |
|
||||||||||||
Refereed: | Yes | ||||||||||||
URI: | http://kups.ub.uni-koeln.de/id/eprint/72721 |
Downloads
Downloads per month over past year
Export
Actions (login required)
View Item |