Difference between revisions of "Magnetotellurics case history: Precambrian overthrust (Northwestern Colorado)"
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==Survey results== | ==Survey results== | ||
| − | [[file:applying-magnetotellurics_fig16-7.png|thumb|{{figure number|1}}An 11-station MT profile across the thrust. Drafted from data from Mills.<ref name=ch16r5 />]] | + | [[file:applying-magnetotellurics_fig16-7.png|thumb|300px|{{figure number|1}}An 11-station MT profile across the thrust. Drafted from data from Mills.<ref name=ch16r5 />]] |
The MT station near the drill hole (see diagram [[:file:applying-magnetotellurics_fig16-7.png|Figure 1]]) shows a thin, near-surface conductor on top of the resistive Precambrian thrust sheet. This is a wedge of Quaternary and [[Tertiary]] sediments. Beneath the thrust, a thick conductive section of Cretaceous sediments is observed. | The MT station near the drill hole (see diagram [[:file:applying-magnetotellurics_fig16-7.png|Figure 1]]) shows a thin, near-surface conductor on top of the resistive Precambrian thrust sheet. This is a wedge of Quaternary and [[Tertiary]] sediments. Beneath the thrust, a thick conductive section of Cretaceous sediments is observed. | ||
Revision as of 20:14, 13 May 2014
| Exploring for Oil and Gas Traps | |
| |
| Series | Treatise in Petroleum Geology |
|---|---|
| Part | Predicting the occurrence of oil and gas traps |
| Chapter | Applying magnetotellurics |
| Author | Arnie Ostrander |
| Link | Web page |
| Store | AAPG Store |
MT can be used in an overthrust environment to delineate conductive sediments beneath a resistive thrust plate. It is often difficult to acquire good-quality seismic data in an overthrust area where high-velocity (high-resistivity) rocks overlie low-velocity (low-resistivity) sediments.
The Precambrian overthrust in the Bear Springs area of northwestern Colorado is an example.[1]
Survey results[edit]
The MT station near the drill hole (see diagram Figure 1) shows a thin, near-surface conductor on top of the resistive Precambrian thrust sheet. This is a wedge of Quaternary and Tertiary sediments. Beneath the thrust, a thick conductive section of Cretaceous sediments is observed.
Figure 1 is an 11-station MT profile across the thrust.
Structural details[edit]
These data provide the following structural details:
- Thickness of Quaternary and Tertiary cover
- Thickness of Precambrian thrust sheet
- Thinning of Cretaceous sediments to the south
- Depth to top of Paleozoic sediments
- No differentiation between Paleozoic and basement
A very detailed subsurface structural map could be obtained in this area using a 3-D grid, controlled-source MT survey depicting the Precambrian/Cretaceous thrust contact and the top of the Paleozoic section.
See also[edit]
- What is magnetotellurics?
- What does an MT survey measure?
- How are MT data acquired?
- Case history: frontier basin analysis (Amazon Basin, Colombia)
- Case history: rugged carbonate terrain (Highlands of Papua New Guinea)
- Case history: volcanic terrain (Columbia River Plateau)
References[edit]
External links[edit]
| find literature about Magnetotellurics case history: Precambrian overthrust (Northwestern Colorado) |
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