| Title | Lateral variation in slab window viscosity inferred from global navigation satellite system (GNSS)-observed uplift due to recent mass loss at Patagonia ice fields |
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| Author | Russo, R M; Luo, H; Wang, K ; Ambrosius, B; Mocanu, V; He, J; James, T;
Bevis, M; Fernandes, R |
| Source | Geology 2021 p. 1-5, https://doi.org/10.1130/G49388.1  Open Access |
| Image |  |
| Year | 2021 |
| Alt Series | Natural Resources Canada, Contribution Series 20210178 |
| Publisher | Geological Society of America |
| Document | serial |
| Lang. | English |
| Media | paper; on-line; digital |
| File format | pdf |
| Area | Chile; Argentina |
| Lat/Long WENS | -77.0000 -70.0000 -43.0000 -53.0000 |
| Subjects | tectonics; geophysics; surficial geology/geomorphology; Science and Technology; Nature and Environment; tectonic environments; subduction zones; mid-ocean ridges; rheology; viscosity; crustal uplift;
deformation; isostasy; geodynamics; satellite geodesy; navigation satellites; glaciers; modelling; mantle; thermal analyses; Chile Ridge; Chile Triple Junction; Nazca Plate; Antarctic Plate; South America Plate; North Patagonia Ice Field; South
Patagonia Ice Field; global navigation satellite systems (GNSS); Phanerozoic; Cenozoic |
| Illustrations | geoscientific sketch maps; time series; 3-D models; profiles |
| Program | Public Safety Geoscience Assessing Earthquake Geohazards |
| Released | 2021 10 08 |
| Abstract | The geographic coincidence of the Chile Ridge slab window and the Patagonia ice fields offers a unique opportunity for assessing the effects of slab window rheology on glacial isostatic adjustment
(GIA). Mass loss of these ice fields since the Little Ice Age causes rapid but variable crustal uplift, 12-24 mm/yr around the North Patagonia ice field, increasing to a maximum of 41 mm/yr around the South Patagonia ice field, as determined from
newly collected or processed geodetic data. We used these observational constraints in a three-dimensional Maxwell viscoelastic finite element model of GIA response above both the subducting slab and slab window in which the upper-mantle viscosity
was parameterized to be uniform with depth. We found that the viscosity of the northern part of the slab window, ~2 × 1000000000000000000 Pa·s, is lower than that of the southern part by approximately an order of magnitude. We propose that this
along-strike viscosity contrast is due to late Cenozoic ridge subduction beneath the northern part of the slab window, which increases asthenospheric temperature and reduces viscosity. |
| Summary | (Plain Language Summary, not published)
When mid-ocean ridge subducts, it creates a gap in the subducting slab called the slab window. Because slab window strongly affects changes in
seismogenic behavior along a subduction zone, its mechanical properties are of great interest. Climatically induced ice melting at the Patagonia icefields causes rapid crustal uplift, and the rate of the uplift depends on the viscosity of the
underlying Chile slab window. Using GPS observations of the uplift rates to constrain a 3-D model, we are able to estimate the viscosity values. We find that the younger northern part of the slab window is less viscous than the older southern
part. |
| GEOSCAN ID | 328621 |
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