The mantle transition zone beneath <scp>W</scp>est <scp>A</scp>ntarctica: Seismic evidence for hydration and thermal upwellings

Emry, E.; Nyblade, A.; Julià, Jordi; Anandakrishnan, S.; Aster, R. C.; Wiens, Douglas A.; Huerta, A. D.; Wilson, T. J.

doi:10.1002/2014gc005588

Cited by 41 publications

(50 citation statements)

References 100 publications

(204 reference statements)

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“…Hansen et al () detected slow wave speed anomalies in the transition zone beneath Marie Byrd Land and suggested that this anomaly extended into the transition zone, but the anomalies were not well localized. Emry et al () investigated the thickness of the transition zone as a proxy for temperature, as the transition zone should be thinner in hot regions. They found evidence for higher temperatures beneath the northeast coast of Marie Byrd Land and also along the southern edge of West Antarctica, but not beneath central Marie Byrd Land.…”

Section: Discussionmentioning

confidence: 99%

Seismic Structure of the Antarctic Upper Mantle Imaged with Adjoint Tomography

Lloyd¹,

Wiens²,

Zhu

et al. 2020

JGR Solid Earth

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109

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The upper mantle and transition zone beneath Antarctica and the surrounding oceans are among the poorest‐imaged regions of the Earth's interior. Over the last 15 years, several large broadband regional seismic arrays have been deployed, as have new permanent seismic stations. Using data from 297 Antarctic and 26 additional seismic stations south of ~40°S, we image the seismic structure of the upper mantle and transition zone using adjoint tomography. Over the course of 20 iterations, we utilize phase observations from three‐component seismograms containing P, S, Rayleigh, and Love waves, including reflections and overtones, generated by 270 earthquakes that occurred from 2001–2003 and 2007–2016. The new continental‐scale seismic model (ANT‐20) possesses regional‐scale resolution south of 60°S. In East Antarctica, thinner continental lithosphere is found beneath areas of Dronning Maud Land and Enderby‐Kemp Land. A continuous slow wave speed anomaly extends from the Balleny Islands through the western Ross Embayment and delineates areas of Cenozoic extension and volcanism that span both oceanic and continental regions. Slow wave speed anomalies are also imaged beneath Marie Byrd Land and along the Amundsen Sea Coast, extending to the Antarctic Peninsula. These anomalies are confined to the upper 200–250 km of the mantle, except in the vicinity of Marie Byrd Land where they extend into the transition zone and possibly deeper. Finally, slow wave speeds along the Amundsen Sea Coast link to deeper anomalies offshore, suggesting a possible connection with deeper mantle processes.

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Section: Discussionmentioning

confidence: 99%

Seismic Structure of the Antarctic Upper Mantle Imaged with Adjoint Tomography

Lloyd¹,

Wiens²,

Zhu

et al. 2020

JGR Solid Earth

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109

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“…It is possible that a thin conduit below the MBL anomaly could go undetected in our models; however, transition zone receiver functions do not indicate a mantle thermal anomaly beneath this region of MBL at transition zone depths [ Emry et al ., ]. Transition zone thinning, indicative of elevated mantle temperatures, is observed elsewhere in West Antarctica with the most significant beneath the MBL coast geographically northwest of station CLRK (Figure ), and thinning is also noted to a lesser extent beneath the Whitmore Mountains and the Bentley Subglacial Trench [ Emry et al ., ].…”

Section: Discussionmentioning

confidence: 99%

“…The absolute P wave tomography has limited resolution but shows a region of slow velocities beneath MBL and part of the eastern WARS extending to ~800 km depth [ Hansen et al ., ]. However, little variation in transition zone thickness is reported beneath the region, suggesting that under normal mantle assumptions, there is no regional mantle thermal anomaly at depths greater than 400 km associated with this feature [ Emry et al ., ].…”

Section: Introductionmentioning

confidence: 99%

A seismic transect across West Antarctica: Evidence for mantle thermal anomalies beneath the Bentley Subglacial Trench and the Marie Byrd Land Dome

et al. 2015

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West Antarctica consists of several tectonically diverse terranes, including the West Antarctic Rift System, a topographic low region of extended continental crust. In contrast, the adjacent Marie Byrd Land and Ellsworth‐Whitmore mountains crustal blocks are on average over 1 km higher, with the former dominated by polygenetic shield and stratovolcanoes protruding through the West Antarctic ice sheet and the latter having a Precambrian basement. The upper mantle structure of these regions is important for inferring the geologic history and tectonic processes, as well as the influence of the solid earth on ice sheet dynamics. Yet this structure is poorly constrained due to a lack of seismological data. As part of the Polar Earth Observing Network, 13 temporary broadband seismic stations were deployed from January 2010 to January 2012 that extended from the Whitmore Mountains, across the West Antarctic Rift System, and into Marie Byrd Land with a mean station spacing of ~90 km. Relative P and S wave travel time residuals were obtained from these stations as well as five other nearby stations by cross correlation. The relative residuals, corrected for both ice and crustal structure using previously published receiver function models of crustal velocity, were inverted to image the relative P and S wave velocity structure of the West Antarctic upper mantle. Some of the fastest relative P and S wave velocities are observed beneath the Ellsworth‐Whitmore mountains crustal block and extend to the southern flank of the Bentley Subglacial Trench. However, the velocities in this region are not fast enough to be compatible with a Precambrian lithospheric root, suggesting some combination of thermal, chemical, and structural modification of the lithosphere. The West Antarctic Rift System consists largely of relative fast uppermost mantle seismic velocities consistent with Late Cretaceous/early Cenozoic extension that at present likely has negligible rift related heat flow. In contrast, the Bentley Subglacial Trench, a narrow deep basin within the West Antarctic Rift System, has relative P and S wave velocities in the uppermost mantle that are ~1% and ~2% slower, respectively, and suggest a thermal anomaly of ~75 K. Models for the thermal evolution of a rift basin suggest that such a thermal anomaly is consistent with Neogene extension within the Bentley Subglacial Trench and may, at least in part, account for elevated heat flow reported at the nearby West Antarctic Ice Sheet Divide Ice Core and at Subglacial Lake Whillans. The slowest relative P and S wave velocity anomaly is observed extending to at least 200 km depth beneath the Executive Committee Range in Marie Byrd Land, which is consistent with warm possibly plume‐related, upper mantle. The imaged low‐velocity anomaly and inferred thermal perturbation (~150 K) are sufficient to support isostatically the anomalous long‐wavelength topography of Marie Byrd Land, relative to the adjacent West Antarctic Rift System.

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“…In WANT, Marie Byrd Land (MBL) is a prominent region of uplift, accompanied by extensive Cenozoic sub ice and subaerial volcanism (LeMasurier, ; Wörner, ). Geochemically, its magmas indicate the signature of a possible deep mantle source (Panter et al, ; Weaver et al, ; Wörner, ) yet a high‐temperature conduit extending into the deep mantle has not been definitely established (Emry et al, ; Hansen et al, ). The relationship between the WARS and MBL uplift is unclear (Behrendt & Cooper, ; Rocchi et al, ; Salvini et al, ).…”

Section: Tectonic Setting Of the Study Regionmentioning

confidence: 99%

The Crust and Upper Mantle Structure of Central and West Antarctica From Bayesian Inversion of Rayleigh Wave and Receiver Functions

Wiens²,

et al. 2018

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We construct a new seismic model for central and West Antarctica by jointly inverting Rayleigh wave phase and group velocities along with P wave receiver functions. Ambient noise tomography exploiting data from more than 200 seismic stations deployed over the past 18 years is used to construct Rayleigh wave phase and group velocity dispersion maps. Comparison between the ambient noise phase velocity maps with those constructed using teleseismic earthquakes confirms the accuracy of both results. These maps, together with P receiver function waveforms, are used to construct a new 3‐D shear velocity (Vs) model for the crust and uppermost mantle using a Bayesian Monte Carlo algorithm. The new 3‐D seismic model shows the dichotomy of the tectonically active West Antarctica (WANT) and the stable and ancient East Antarctica (EANT). In WANT, the model exhibits a slow uppermost mantle along the Transantarctic Mountains (TAMs) front, interpreted as the thermal effect from Cenozoic rifting. Beneath the southern TAMs, the slow uppermost mantle extends horizontally beneath the traditionally recognized EANT, hypothesized to be associated with lithospheric delamination. Thin crust and lithosphere observed along the Amundsen Sea coast and extending into the interior suggest involvement of these areas in Cenozoic rifting. EANT, with its relatively thick and cold crust and lithosphere marked by high Vs, displays a slower Vs anomaly beneath the Gamburtsev Subglacial Mountains in the uppermost mantle, which we hypothesize may be the signature of a compositionally anomalous body, perhaps remnant from a continental collision.

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The mantle transition zone beneath West Antarctica: Seismic evidence for hydration and thermal upwellings

Cited by 41 publications

References 100 publications

Seismic Structure of the Antarctic Upper Mantle Imaged with Adjoint Tomography

Seismic Structure of the Antarctic Upper Mantle Imaged with Adjoint Tomography

A seismic transect across West Antarctica: Evidence for mantle thermal anomalies beneath the Bentley Subglacial Trench and the Marie Byrd Land Dome

The Crust and Upper Mantle Structure of Central and West Antarctica From Bayesian Inversion of Rayleigh Wave and Receiver Functions

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