Shallow-source aeromagnetic anomalies observed over the West Antarctic Ice Sheet compared with coincident bed topography from radar ice sounding—new evidence for glacial “removal” of subglacially erupted late Cenozoic rift-related volcanic edifices

Behrendt, John C.; Blankenship, D. D.; Morse, D. L.; Bell, Robin E.

doi:10.1016/j.gloplacha.2003.10.006

Cited by 28 publications

(27 citation statements)

References 30 publications

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“…The large volumes of sediment offshore of these sectors require a minimum average reconstructed elevation slightly above present sea level and permit an average elevation many hundreds of meters higher. Our reconstruction is certainly artificially smooth, as horst-and-graben fabric visible in ice-penetrating radar (Luyendyk et al, 2003;Behrendt et al, 2004) would be expected to have already been present prior to glacial erosion.…”

Section: Resultsmentioning

confidence: 99%

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Antarctic topography at the Eocene–Oligocene boundary

Wilson

Jamieson

Barrett

et al. 2012

Palaeogeography, Palaeoclimatology, Palaeoecology

181

217

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We present a reconstruction of the Antarctic topography at the Eocene-Oligocene (ca. 34 Ma) climate transition. This provides a realistic key boundary condition for modeling the first big Antarctic ice sheets at this time instead of using the present day bedrock topography, which has changed significantly from millions of years of tectonism and erosion. We reconstruct topography using a set of tools including ice sheet-erosion models, models of thermal subsidence and plate movement. Erosion estimates are constrained with offshore sediment volumes estimated from seismic stratigraphy. Maximum and minimum topographic reconstructions are presented as indicators of the range of uncertainty. Our results point to a significant upland area in the Ross Sea/Marie Byrd Land and Weddell Sea sectors. In addition, East Antarctic coastal troughs are much shallower than today due to the restoration of material that has been selectively eroded by the evolving ice sheets. Parts of East Antarctica have not changed since the E-O boundary because they were protected under non-erosive cold-based ice. The reconstructions provide a better-defined boundary condition for modeling that seeks to understand interaction between the Antarctic ice sheet and climate, along with more robust estimates of past ice volumes under a range of orbital settings and greenhouse gas concentrations.

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Section: Resultsmentioning

confidence: 99%

“…2a). In the Marie Byrd Land area of West Antarctica, several recent studies have reported significant improvements to the topographic database (Luyendyk et al, 2003;Behrendt et al, 2004;Holt et al, 2006;Vaughan et al, 2006;Wilson and Luyendyk, 2006), and we incorporate these updates in our grid (Fig. S1).…”

Section: Initial Topographymentioning

confidence: 99%

Antarctic topography at the Eocene–Oligocene boundary

Wilson

Jamieson

Barrett

et al. 2012

Palaeogeography, Palaeoclimatology, Palaeoecology

181

217

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“…Tectonic boundaries might be aligned with the basal topographic edge of the inter–ice stream ridges, which might explain the orientation of B1 and B2. Unfortunately, aerogeophysical surveys of the Siple Coast region [ Behrendt et al , 2004] do not extend over the downstream end of KIS. However, there are several characteristics of the synclines and flat ice terrains which are not easily reconciled with this scenario: (1) we expect that geologic sources of heat would be more persistent than the observed maximum time span for basal melting (300 years), (2) most aeromagnetic anomaly sources at the base of the ice sheet are associated with bed relief of between 60 and 600 m [ Behrendt et al , 2004]; such bed relief is not seen here, and (3) unless the heat source is very shallow, we expect that geothermal heat sources would be wider than the narrow region of basal melt observed.…”

Section: Discussion: Mechanisms Of Basal Meltmentioning

confidence: 99%

Evidence for floatation or near floatation in the mouth of Kamb Ice Stream, West Antarctica, prior to stagnation

et al. 2006

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[1] Ice-penetrating radar profiles reveal distinctive internal structure within the flat ice terrains that bound the lower reaches of the now stagnant Kamb Ice Stream, West Antarctica; slightly warped but continuous upper layers overlie extensive deep line diffractors located at a uniform depth several hundreds of meters above the bed. On the basis of their orientation and morphology we interpret the line diffractors to be the tips of basal crevasses. At the boundary between these terrains and the inter-ice stream ridges, internal layers are strongly downwarped, and the deepest layers are truncated at the bed. Results from simple kinematic ice flow modeling indicate that the observed layer pattern requires a cumulative basal melt of 120-350 m over a time period that is less than 300 years. Fields of basal crevasses are typically observed in ice shelves; however, isolated basal crevasses can also be found in grounded ice when the subglacial water pressure is close to overburden. On the basis of the presence of these crevasses we argue that these terrains were once floating or near floating in the past. We combine model results with estimates of recent ice thickness change to suggest that floatation was transitory and the region may have become fully grounded roughly 200 years prior to stagnation of Kamb Ice Stream.

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“…Aeromagnetic data have been interpreted as evidence for large volumes of volcanic products (>10 6 km 3 ) concealed beneath the ice sheet (Behrendt et al, 1994;Behrendt et al, 2004). If such a volume estimate is accepted and a Cenozoic age is assumed for all the inferred volcanic edifices, the average magma production rate is nevertheless low when the long duration of igneous activity (almost 50 m.y.)…”

Section: Spatial-chronological-volume Distribution Of the Igneous Actmentioning

confidence: 99%

No plume, no rift magmatism in the West Antarctic Rift

Rocchi¹,

Armienti²,

Vincenzo³

2005

Plates, Plumes and Paradigms

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The West Antarctic Rift system is one of the largest areas of crustal extension in the world. Current interpretations of its driving mechanisms rely mostly on the occurrence of one or more mantle plumes that was active during the Cenozoic or the Mesozoic. The plume hypotheses are mainly based on the similarity between the basalts from the West Antarctic Rift and those associated with long-lived hotspot tracks. The geochemical signature of the mafic rocks is indeed typical of ocean island basalts (OIB), from a source with a tendency to high , i.e., high U/Pb (HIMU) mantle. However, these features cannot be exclusively interpreted in terms of a plume sampling very old slab material recycled at great depth for a long time (10 9 yr): a metasomatic event at a time on the order of 10 8 yr (i.e., Cretaceous) is sufficient to have produced the required source features.Geometric-chronological relationships between magmatism and local tectonic activity further constrain the scenario. In Victoria Land, the occurrence of plutons, dike swarms, and volcanic edifices since the Middle Eocene indicates that magma emplacement is guided by the dextral strike-slip fault systems that dissect the rift shoulder in this area. The faults were active at their Ross Sea termination in Cenozoic time, coeval with magma emplacement, as demonstrated by the ca. 34 Ma age of a pseudotachylyte generated in the right-lateral fault system exposed in northern Victoria Land. Middle Eocene activity is also inferred for the Pacific termination of the faults from apatite fission track thermochronology. In a wider perspective, these faults are in striking continuity with Southern Ocean fracture zones, and mantle tomography depicts a thermal anomaly of linear (not circular) shape overlapping the belt of the same fracture zones, suggesting that the anomaly is related to lithospheric geometry and movements rather than to deep plumes.The lack of any decisive evidence for plume activity is thus associated with the evidence that large-scale tectonic features drove magma emplacement: the Cenozoic fault systems reactivated Paleozoic tectonic discontinuities, and their activity is dynamically linked to the Southern Ocean fracture zones. As an alternative to both active (plume-driven) rifting and passive rifting, we propose that lithospheric strike-slip deformation could have promoted transtension-related decompression melting of a 435 *

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Shallow-source aeromagnetic anomalies observed over the West Antarctic Ice Sheet compared with coincident bed topography from radar ice sounding—new evidence for glacial “removal” of subglacially erupted late Cenozoic rift-related volcanic edifices

Cited by 28 publications

References 30 publications

Antarctic topography at the Eocene–Oligocene boundary

Antarctic topography at the Eocene–Oligocene boundary

Evidence for floatation or near floatation in the mouth of Kamb Ice Stream, West Antarctica, prior to stagnation

No plume, no rift magmatism in the West Antarctic Rift

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