Gravity constraints on structure of the East-West Antarctic lithospheric transition zone
The differing structural evolution of cratonic East Antarctica and younger West Antarctica has resulted in contrasting lithospheric and asthenospheric mantle viscosities between the two regions. Combined with poor constraints on the upper mantle viscosity structure of the continent, estimates of sur...
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ftsmithonian:oai:figshare.com:article/15110442 2023-05-15T13:56:27+02:00 Gravity constraints on structure of the East-West Antarctic lithospheric transition zone Treweek, Sam (11233980) 2021-08-05T05:14:26Z https://doi.org/10.26686/wgtn.15110442.v1 unknown https://figshare.com/articles/thesis/Gravity_constraints_on_structure_of_the_East-West_Antarctic_lithospheric_transition_zone/15110442 doi:10.26686/wgtn.15110442.v1 CC BY-SA 4.0 CC-BY-SA Gravimetrics Geophysics Antarctica Gravity Taylor Valley School: School of Geography Environment and Earth Sciences 040405 Gravimetrics Degree Discipline: Geophysics Degree Level: Masters Degree Name: Master of Science Text Thesis 2021 ftsmithonian https://doi.org/10.26686/wgtn.15110442.v1 2021-12-20T04:59:56Z The differing structural evolution of cratonic East Antarctica and younger West Antarctica has resulted in contrasting lithospheric and asthenospheric mantle viscosities between the two regions. Combined with poor constraints on the upper mantle viscosity structure of the continent, estimates of surface uplift in Antarctica predicted from models of glacial isostatic adjustment (GIA) and observed by Global Satellite Navigation System (GNSS) contain large misfits. This thesis presents a gravity study ofthe lithospheric transition zone beneath the Taylor Valley, Antarctica, conducted to constrain the variation in lithological parameters such as viscosity and density of the upper mantle across this region. During this study 119 new gravity observations were collected in the ice-free regions of the Taylor Valley and amalgamated with 154 existing land-based gravity observations, analysed alongside aerogravity measurements of southern Victoria Land. Gravity data are used to construct 2D gravity models of the subsurface beneath this region. An eastward gradient in Bouguer anomalies of ~- 1.6 mGal/km is observed within the Taylor Valley. Models reveal thickening of the Moho from 23±5 km beneath the Ross Sea to 35±5 km in the Polar Plateau (dipping at 24.5±7.2°), and lithospheric mantle 100 km thicker in East Antarctica (~200±30 km) than West Antarctica (~90±30 km). Models of predicted surface uplift history are used to estimate an asthenospheric mantle viscosity of 2.1x1020 Pa.s at full surface recovery beneath the Ross Embayment, differing by ~14% from the viscosity at 50% recovery. The temperature contrast between lithospheric and asthenospheric mantle is estimated as ~400°C, equivalent to a viscosity that decreases by a factor of about 30 over the mantle boundary. Results demonstrate that the history of surface uplift in the study area may be complicated, resulting in observations of uplift, or subsidence, at GNSS stations. Future work should incorporate additional geophysical methods, such as seismicity and electrical resistivity, improving constraints on gravity models. A better understanding of the surface uplift (or subsidence) history in the Transantarctic Mountains is critical, with implications in reducing uncertainty in GIA models. Thesis Antarc* Antarctic Antarctica East Antarctica Ross Sea Victoria Land West Antarctica Unknown Antarctic East Antarctica Ross Sea West Antarctica Victoria Land Transantarctic Mountains Taylor Valley ENVELOPE(163.000,163.000,-77.617,-77.617) Polar Plateau ENVELOPE(0.000,0.000,-90.000,-90.000) |
institution |
Open Polar |
collection |
Unknown |
op_collection_id |
ftsmithonian |
language |
unknown |
topic |
Gravimetrics Geophysics Antarctica Gravity Taylor Valley School: School of Geography Environment and Earth Sciences 040405 Gravimetrics Degree Discipline: Geophysics Degree Level: Masters Degree Name: Master of Science |
spellingShingle |
Gravimetrics Geophysics Antarctica Gravity Taylor Valley School: School of Geography Environment and Earth Sciences 040405 Gravimetrics Degree Discipline: Geophysics Degree Level: Masters Degree Name: Master of Science Treweek, Sam (11233980) Gravity constraints on structure of the East-West Antarctic lithospheric transition zone |
topic_facet |
Gravimetrics Geophysics Antarctica Gravity Taylor Valley School: School of Geography Environment and Earth Sciences 040405 Gravimetrics Degree Discipline: Geophysics Degree Level: Masters Degree Name: Master of Science |
description |
The differing structural evolution of cratonic East Antarctica and younger West Antarctica has resulted in contrasting lithospheric and asthenospheric mantle viscosities between the two regions. Combined with poor constraints on the upper mantle viscosity structure of the continent, estimates of surface uplift in Antarctica predicted from models of glacial isostatic adjustment (GIA) and observed by Global Satellite Navigation System (GNSS) contain large misfits. This thesis presents a gravity study ofthe lithospheric transition zone beneath the Taylor Valley, Antarctica, conducted to constrain the variation in lithological parameters such as viscosity and density of the upper mantle across this region. During this study 119 new gravity observations were collected in the ice-free regions of the Taylor Valley and amalgamated with 154 existing land-based gravity observations, analysed alongside aerogravity measurements of southern Victoria Land. Gravity data are used to construct 2D gravity models of the subsurface beneath this region. An eastward gradient in Bouguer anomalies of ~- 1.6 mGal/km is observed within the Taylor Valley. Models reveal thickening of the Moho from 23±5 km beneath the Ross Sea to 35±5 km in the Polar Plateau (dipping at 24.5±7.2°), and lithospheric mantle 100 km thicker in East Antarctica (~200±30 km) than West Antarctica (~90±30 km). Models of predicted surface uplift history are used to estimate an asthenospheric mantle viscosity of 2.1x1020 Pa.s at full surface recovery beneath the Ross Embayment, differing by ~14% from the viscosity at 50% recovery. The temperature contrast between lithospheric and asthenospheric mantle is estimated as ~400°C, equivalent to a viscosity that decreases by a factor of about 30 over the mantle boundary. Results demonstrate that the history of surface uplift in the study area may be complicated, resulting in observations of uplift, or subsidence, at GNSS stations. Future work should incorporate additional geophysical methods, such as seismicity and electrical resistivity, improving constraints on gravity models. A better understanding of the surface uplift (or subsidence) history in the Transantarctic Mountains is critical, with implications in reducing uncertainty in GIA models. |
format |
Thesis |
author |
Treweek, Sam (11233980) |
author_facet |
Treweek, Sam (11233980) |
author_sort |
Treweek, Sam (11233980) |
title |
Gravity constraints on structure of the East-West Antarctic lithospheric transition zone |
title_short |
Gravity constraints on structure of the East-West Antarctic lithospheric transition zone |
title_full |
Gravity constraints on structure of the East-West Antarctic lithospheric transition zone |
title_fullStr |
Gravity constraints on structure of the East-West Antarctic lithospheric transition zone |
title_full_unstemmed |
Gravity constraints on structure of the East-West Antarctic lithospheric transition zone |
title_sort |
gravity constraints on structure of the east-west antarctic lithospheric transition zone |
publishDate |
2021 |
url |
https://doi.org/10.26686/wgtn.15110442.v1 |
long_lat |
ENVELOPE(163.000,163.000,-77.617,-77.617) ENVELOPE(0.000,0.000,-90.000,-90.000) |
geographic |
Antarctic East Antarctica Ross Sea West Antarctica Victoria Land Transantarctic Mountains Taylor Valley Polar Plateau |
geographic_facet |
Antarctic East Antarctica Ross Sea West Antarctica Victoria Land Transantarctic Mountains Taylor Valley Polar Plateau |
genre |
Antarc* Antarctic Antarctica East Antarctica Ross Sea Victoria Land West Antarctica |
genre_facet |
Antarc* Antarctic Antarctica East Antarctica Ross Sea Victoria Land West Antarctica |
op_relation |
https://figshare.com/articles/thesis/Gravity_constraints_on_structure_of_the_East-West_Antarctic_lithospheric_transition_zone/15110442 doi:10.26686/wgtn.15110442.v1 |
op_rights |
CC BY-SA 4.0 |
op_rightsnorm |
CC-BY-SA |
op_doi |
https://doi.org/10.26686/wgtn.15110442.v1 |
_version_ |
1766263960587206656 |