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Unconformable stratigraphy in East Antarctica: Part I. Large firn cosets, recrystallized growth, and model evidence for intensified accumulation

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Abstract:

Unconformable firn stratigraphy exists throughout a 650 km long radar profile that we recorded down-flow of megadune fields in the Byrd Glacier (East Antarctica) catchment. Profile segments reveal cosets of prograding bedding sequences up to 90 m thick and with lateral, along-crest dimensions up to tens of kilometers. We profiled them in oblique section and nearly parallel to the prevailing wind. The prograding snow accumulates on broad, low windward slopes located above ice-bed depressions, which implies long-term slope stability. The apparent subglacial control implies that the accumulation progrades in balance with ice velocity, which we measured at ∼30 m a–1. The sequences prograde over intensely modified and recrystallized wind-glaze firn, visible in the profiles as unstratified layers and zones up to several tens of meters thick. The intense recrystallization eliminates density stratification, and the altered layers appear to thicken into a connected network. Modeling of coset formation using wind and ice flow reproduces their dimensions and morphology. However, accumulation rates well above current regional estimates and existing data for megadunes are required because of the measured ice speed and required slope stability. The consistent unconformable strata along our traverse show that coset and recrystallized morphology extend far beyond the megadune fields.

Document Type: Research Article

DOI: http://dx.doi.org/10.3189/2012JoJ11J044

Publication date: April 1, 2012

More about this publication?
  • The Journal of Glaciology is published six times per year. It accepts submissions from any discipline related to the study of snow and ice. All articles are peer reviewed. The Journal is included in the ISI Science Citation Index.
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