subglacial landform analysis and reconstruction of miocene paleotopography of marie byrd land perry...
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Subglacial Landform Analysis and Reconstruction of Miocene
Paleotopography of Marie Byrd Land
Perry Spector1,2, Christine Siddoway1, and Paul Morin2
1Dept Geology, Colorado College, Colorado Springs, CO2Antarctic Geospatial Information Center, University of Minnesota,
Minneapolis, MN
ANTscape• International group of Antarctic researchers and climate scientists
• ACE subcommittee on Antarctic Paleotopographic Maps
• 3 yr mission: Create a series of series of paleotopographic maps from Cretaceous to Present which:
• Show change in bedrock elevations, landforms, and geotectonic configuration of Antarctica over the past ~100 Ma.
• Visualizations of past landscapes
• Provide a geographical base for diverse paleo-environmental data:
• Cretaceous through Recent climate variations• Biological evolution and biodiversity • Glacial cycles and growth of continental ice sheets.
ANT scape
Time intervals for paleotopographic reconstructionFirst Priority:
1.~34 Ma• Landscape that supported first continental ice sheet when global
temperatures dropped from ~8 to ~4°C above present
2.~4 Ma• Pliocene warm period when global temperatures were ~3°C warmer
3.~50 Ma• Eocene warm peak (as distinct from the PETM at 55 Ma)• Warmest part of Greenhouse Earth (10-15°C warmer than present)• Will help address the question of formation of ABW in a Greenhouse
world
Time intervals for paleotopographic reconstructionSecond Priority:
4.14 Ma • Mid Miocene climate transition
5.~70 Ma • Antarctic margins were established once Gondwana breakup was
complete• The Late Cretaceous was a time of cool climate
6.~92 Ma• Continental separation had occurred on all but the West Antarctic
margin• Intracontinental extension underway in the WARS• Early Cretaceous was a time of warm climate (Miller et al, 2005)• ~20 m sea level drop observed in the oceanographic record is attributed
to glaciation
34 Ma restoration (Wilson and Luyendyk, GRL, 2009)
Image from Studinger and Barrett, 2009, Nature Geoscience
Factors accounted for:1.Loading from growth of ice sheets2.Subsidence from thermal contraction as a result of prior tectonic extension3.Erosion and sediment deposition4.Horizontal tectonic motion since 34 Ma
BEDMAP1_plus
WAIS initiation models / high topog
Pollard and DeConto, 2003
MBL Subaerial Volcano Ages
High summits and alpine areas absent at 34 Ma onset of continental Glaciation
17 Ma or younger (Mt Petras and Reynolds excepted)
LeMasurier and Rocchi, 2005
Glacial IncisionJamieson and Sugden, 2008:-Following mid-Miocene climate transition, Antarctica entered an arid period when extensive areas of the ice sheets became cold-based. Warm-based glacial erosion became focused within preexisting drainages at low elevation, leading to development of deeply incised outlet glacier troughs.
Red line --lithospheric boundary, inferred. Origin: intracontinental transform active in Cretaceous time.
Takahe, 3460m
Sidley, 4181 m
Hampton13.7 – 8.5 Ma
Perkins, 1178m c. 1.4 Ma
Siple, 3110 m
Petras29-25 Ma
Berlin, 3478m 2.5 Ma – 0 yr
Crary Mtns
Siddoway et al., 2005; Siddoway 2008; McFadden et al. 2009 in revision
Miocene Volcanoes and glacier streams
BEDMAP1_plus
WARS
Mt Takahe
Ford Ranges
~21 Ma Reconstruction
WARS
BEDMAP1_plus
Analyzed cross-sectional profiles of bedrock topography (BEDMAP1_plus) on a 40 km grid
BEDMAP1_plus
Analyzed cross-sectional profiles of bedrock topography (BEDMAP1_plus) on a 40 km grid
AssumptionsVolcanism - Interpret the majority of eastern MBL subglacial vertical relief to be a result of volcanism
• Close proximity to subaerial volcanoes • Topographically concentric morphology• Comparison with findings of numerous subglacial volcanoes from CWA geophysical surveys.
Glacial Incision – Certain deep, structurally-controlled troughs have been further deepened by glacial incision
Sedimentation - Deep, structural basins have been locations of deposition
Methods, assumptions, and reasoning - Volcanoes
Methods, Assumptions, and Reasoning - Incised glacial valleys
Methods, Assumptions, and Reasoning - Sediment volumes
For more in-depth treatment, see Wilson and Luyendyk, GRL, September 2009
Alpine glacier troughs in Executive Committee Range
Flexural Moat around Executive Committee Range
Conclusions
• ANTscape’s effort to create a series of paleotopographic maps of Antarctica over the past ~100 Ma
• MBL volcanoes are 17 Ma to present (Petras and Reynolds excepted) and thus were not present to serve as high elevation sites for ice cap nucleation during early history of WAIS.
• Alpine glacier troughs on 14 Ma and younger volcanoes of Executive Committee Range• Wet-based erosive features formed at high elevations after the mid-
Miocene climate transition (change to hyper arid climate and onset of cold-based mode of Antarctic glaciation (Jamieson and Sugden, 2008)) is a possible indication of elevated basal thermal conditions in the vicinity of the volcanoes.
• Volcanic moat on north and south margins of Executive Committee Range• Potentially show the need of accounting for volcanic rock in addition to ice
in isostatic corrections of WANT
Methods, Assumptions, and Reasoning
BEDMAP1_plus
Mt Takahe
WARS
Ford Ranges
~21 Ma Reconstruction
WARS