Scapozza, Cristian and Baron, Ludovic and Lambiel, Christophe (2015) Borehole Logging in Alpine Periglacial Talus Slopes (Valais, Swiss Alps). Permafrost and Periglacial Processes, 26 (1). pp. 67-83. ISSN 1099-1530
Full text not available from this repository.Abstract
Geophysical measurements were carried out in six boreholes at three periglacial talus slopes in the Swiss Alps in order to determine the talus structure and the geological and permafrost stratigraphy. These are important elements of interpretation of the palaeoclimatic significance of Alpine talus slopes. This study combined three nuclear well logging methods. Natural radioactivity of rocks and ice-rich permafrost were determined by using natural gamma-ray logs through the lack of radioactivity of massive ice. Quantification of the ice content in frozen layers and the air content in unfrozen layers by variations in bulk density was provided by the application of gamma-gamma logs. Neutron-thermal neutron logs were used to calculate the water content, linked with the porosity of the formation. Combination of the three logs allowed three-phase models (rock, ice and air/water) of the subsurface to be obtained. Results show that the air content decreases with depth because of the increasing in-situ stresses that cause compression of the rock debris and the existence of a fine matrix filling the voids. Calculation of the ice content variations shows that talus slopes are frequently partially saturated with ice or, at most, slightly supersaturated with ice. All three logs provide complementary information on the progressive infilling of the voids with depth and the occurrence of ice-rich layers. A similar trend in ice content and the apparent porosity was highlighted by the joint application of gamma-gamma and neutron-neutron logs, which provide a mirror image of these two parameters.
| Item Type: | Scientific journal article, Newspaper article or Magazine article |
|---|---|
| Uncontrolled Keywords: | borehole geophysics;nuclear well logging;porosity;ice content;talus slope;Swiss Alps |
| Subjects: | Physical sciences > Geology > Geophysics > Exploration geophysics Physical sciences > Science of aquatic & terrestrial environments > Glaciology & cryospheric systems Physical sciences > Physical geographical sciences > Physical geography > Geomorphology |
| Department/unit: | Dipartimento ambiente costruzioni e design > Istituto scienze della Terra |
| Depositing User: | Cristian Scapozza |
| Date Deposited: | 17 Apr 2015 11:38 |
| Last Modified: | 23 May 2016 08:15 |
| URI: | http://repository.supsi.ch/id/eprint/5748 |
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