TY - JOUR
T1 - The uppermost mantle seismic velocity structure of West Antarctica from Rayleigh wave tomography
T2 - Insights into tectonic structure and geothermal heat flow
AU - O'Donnell, J. P.
AU - Stuart, G. W.
AU - Brisbourne, A. M.
AU - Selway, K.
AU - Yang, Y.
AU - Nield, G. A.
AU - Whitehouse, P. L.
AU - Nyblade, A. A.
AU - Wiens, D. A.
AU - Aster, R. C.
AU - Anandakrishnan, S.
AU - Huerta, A. D.
AU - Wilson, T.
AU - Winberry, J. P.
N1 - Funding Information:
We thank all BAS camp staff, field guides and air unit personnel for the logistical support of the UKANET seismic and GNSS networks. We similarly acknowledge all field teams and camp staff associated with the POLENET-ANET project, and thank Kenn Borek Air and the New York Air Guard for flight support. JPOD, GAN and PLW are supported by the Natural Environment Research Council [grants NE/L006065/1 , NE/L006294/1 and NE/K009958/1 ], KS is supported by the Australia Research Council [grant F150100541 ]. POLENET-ANET is supported by the National Science Foundation Office of Polar Programs [grants 0632230 , 0632239 , 0652322 , 0632335 , 0632136 , 0632209 , and 0632185 ]. UKANET seismic instrumentation was provided and supported by SEIS-UK. POLENET-ANET seismic instrumentation was provided and supported by the Incorporated Research Institutions for Seismology (IRIS) through the PASSCAL Instrument Center. The UKANET ( www.ukanet.wixsite.com/ukanet ; network code 1D; https://doi.org/10.7914/SN/1D_2016 ) data will be accessible through the IRIS Data Management Center ( http://www.iris.edu/mda ) from January 2021. POLENET-ANET (network code YT), ASAIN (network code AI), GSN (network code IU) and SEPA (network code XB) seismic data can be accessed through the IRIS DMC. The facilities of the IRIS Consortium are supported by the National Science Foundation under cooperative agreement EAR-1063471 , the NSF Office of Polar Programs , and the DOE National Nuclear Security Administration . Figures were created using the Generic Mapping Tools (GMT) software ( http://gmt.soest.hawaii.edu ). The phase and shear wave velocity models developed here can be accessed at the UK Polar Data Centre ( https://doi.org/10.5285/c11bdb27-df44-4b56-8f4c-afc51b6e1e3a and https://doi.org/10.5285/b5ffac8a-9846-4f86-9a71-3ce992a18148 ). We thank Jolante van Wijk and an anonymous reviewer for helpful reviews.
Funding Information:
We thank all BAS camp staff, field guides and air unit personnel for the logistical support of the UKANET seismic and GNSS networks. We similarly acknowledge all field teams and camp staff associated with the POLENET-ANET project, and thank Kenn Borek Air and the New York Air Guard for flight support. JPOD, GAN and PLW are supported by the Natural Environment Research Council [grants NE/L006065/1, NE/L006294/1 and NE/K009958/1], KS is supported by the Australia Research Council [grant F150100541]. POLENET-ANET is supported by the National Science Foundation Office of Polar Programs [grants 0632230, 0632239, 0652322, 0632335, 0632136, 0632209, and 0632185]. UKANET seismic instrumentation was provided and supported by SEIS-UK. POLENET-ANET seismic instrumentation was provided and supported by the Incorporated Research Institutions for Seismology (IRIS) through the PASSCAL Instrument Center. The UKANET (www.ukanet.wixsite.com/ukanet; network code 1D; https://doi.org/10.7914/SN/1D_2016) data will be accessible through the IRIS Data Management Center (http://www.iris.edu/mda) from January 2021. POLENET-ANET (network code YT), ASAIN (network code AI), GSN (network code IU) and SEPA (network code XB) seismic data can be accessed through the IRIS DMC. The facilities of the IRIS Consortium are supported by the National Science Foundation under cooperative agreement EAR-1063471, the NSF Office of Polar Programs, and the DOE National Nuclear Security Administration. Figures were created using the Generic Mapping Tools (GMT) software (http://gmt.soest.hawaii.edu). The phase and shear wave velocity models developed here can be accessed at the UK Polar Data Centre (https://doi.org/10.5285/c11bdb27-df44-4b56-8f4c-afc51b6e1e3a and https://doi.org/10.5285/b5ffac8a-9846-4f86-9a71-3ce992a18148). We thank Jolante van Wijk and an anonymous reviewer for helpful reviews.
Publisher Copyright:
© 2019 Elsevier B.V.
PY - 2019/9/15
Y1 - 2019/9/15
N2 - We present a shear wave model of the West Antarctic upper mantle to ∼200 km depth with enhanced regional resolution from the 2016-2018 UK Antarctic Seismic Network. The model is constructed from the combination of fundamental mode Rayleigh wave phase velocities extracted from ambient noise (periods 8-25 s) and earthquake data by two-plane wave analysis (periods 20-143 s). We seek to (i) image and interpret structures against the tectonic evolution of West Antarctica, and (ii) extract information from the seismic model that can serve as boundary conditions in ice sheet and glacial isostatic adjustment modelling efforts. The distribution of low velocity anomalies in the uppermost mantle suggests that recent tectonism in the West Antarctic Rift System (WARS) is mainly concentrated beneath the rift margins and largely confined to the uppermost mantle (<180 km). On the northern margin of the WARS, a pronounced low velocity anomaly extends eastward from beneath the Marie Byrd Land dome toward Pine Island Bay, underlying Thwaites Glacier, but not Pine Island Glacier. If of plume-related thermal origin, the velocity contrast of ∼5% between this anomaly and the inner WARS translates to a temperature difference of ∼125-200 C∘. However, the strike of the anomaly parallels the paleo-Pacific convergent margin of Gondwana, so it may reflect subduction-related melt and volatiles rather than anomalously elevated temperatures, or a combination thereof. Motivated by xenolith analyses, we speculate that high velocity zones imaged south of the Marie Byrd Land dome and in the eastern Ross Sea Embayment might reflect the compositional signature of ancient continental fragments. A pronounced low velocity anomaly underlying the southern Transantarctic Mountains (TAM) is consistent with a published lithospheric foundering hypothesis. Taken together with a magnetotelluric study advocating flexural support of the central TAM by thick, stable lithosphere, this points to along-strike variation in the tectonic history of the TAM. A high velocity anomaly located in the southern Weddell Sea Rift System might reflect depleted mantle lithosphere following the extraction of voluminous melt related to Gondwana fragmentation. Lithospheric thickness estimates extracted from 1D shear wave velocity profiles representative of tectonic domains in West Antarctica indicate an average lithospheric thickness of ∼85 km for the WARS, Marie Byrd Land, and Thurston Island block. This increases to ∼96 km in the Ellsworth Mountains. A surface heat flow of ∼60mW/m2 and attendant geotherm best explains lithospheric mantle shear wave velocities in the central WARS and in the Thurston Island block adjacent to Pine Island Glacier; a ∼50mW/m2 geotherm best explains the velocities in the Ellsworth Mountains, and a ∼60mW/m2 geotherm best explains a less well-constrained velocity profile on the southern Antarctic Peninsula. We emphasise that these are regional average (many hundreds of km) heat flow estimates constrained by seismic data with limited sensitivity to upper crustal composition.
AB - We present a shear wave model of the West Antarctic upper mantle to ∼200 km depth with enhanced regional resolution from the 2016-2018 UK Antarctic Seismic Network. The model is constructed from the combination of fundamental mode Rayleigh wave phase velocities extracted from ambient noise (periods 8-25 s) and earthquake data by two-plane wave analysis (periods 20-143 s). We seek to (i) image and interpret structures against the tectonic evolution of West Antarctica, and (ii) extract information from the seismic model that can serve as boundary conditions in ice sheet and glacial isostatic adjustment modelling efforts. The distribution of low velocity anomalies in the uppermost mantle suggests that recent tectonism in the West Antarctic Rift System (WARS) is mainly concentrated beneath the rift margins and largely confined to the uppermost mantle (<180 km). On the northern margin of the WARS, a pronounced low velocity anomaly extends eastward from beneath the Marie Byrd Land dome toward Pine Island Bay, underlying Thwaites Glacier, but not Pine Island Glacier. If of plume-related thermal origin, the velocity contrast of ∼5% between this anomaly and the inner WARS translates to a temperature difference of ∼125-200 C∘. However, the strike of the anomaly parallels the paleo-Pacific convergent margin of Gondwana, so it may reflect subduction-related melt and volatiles rather than anomalously elevated temperatures, or a combination thereof. Motivated by xenolith analyses, we speculate that high velocity zones imaged south of the Marie Byrd Land dome and in the eastern Ross Sea Embayment might reflect the compositional signature of ancient continental fragments. A pronounced low velocity anomaly underlying the southern Transantarctic Mountains (TAM) is consistent with a published lithospheric foundering hypothesis. Taken together with a magnetotelluric study advocating flexural support of the central TAM by thick, stable lithosphere, this points to along-strike variation in the tectonic history of the TAM. A high velocity anomaly located in the southern Weddell Sea Rift System might reflect depleted mantle lithosphere following the extraction of voluminous melt related to Gondwana fragmentation. Lithospheric thickness estimates extracted from 1D shear wave velocity profiles representative of tectonic domains in West Antarctica indicate an average lithospheric thickness of ∼85 km for the WARS, Marie Byrd Land, and Thurston Island block. This increases to ∼96 km in the Ellsworth Mountains. A surface heat flow of ∼60mW/m2 and attendant geotherm best explains lithospheric mantle shear wave velocities in the central WARS and in the Thurston Island block adjacent to Pine Island Glacier; a ∼50mW/m2 geotherm best explains the velocities in the Ellsworth Mountains, and a ∼60mW/m2 geotherm best explains a less well-constrained velocity profile on the southern Antarctic Peninsula. We emphasise that these are regional average (many hundreds of km) heat flow estimates constrained by seismic data with limited sensitivity to upper crustal composition.
UR - http://www.scopus.com/inward/record.url?scp=85068899453&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85068899453&partnerID=8YFLogxK
U2 - 10.1016/j.epsl.2019.06.024
DO - 10.1016/j.epsl.2019.06.024
M3 - Article
AN - SCOPUS:85068899453
VL - 522
SP - 219
EP - 233
JO - Earth and Planetary Science Letters
JF - Earth and Planetary Science Letters
SN - 0012-821X
ER -