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Tectonics of the West Antarctic Rift System: New Light on the History and Dynamics of Distributed Intracontinental Extension--C. S. Siddoway
Tectonics of the West Antarctic Rift System: New Light on the History and Dynamics of Distributed Intracontinental Extension--C. S. Siddoway
Pages 91-114
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From page 91... ...
includes Antarctica and New Zealand. New structural, petrological, the Ross Sea and Ross Ice Shelf, the West Antarctic ice sheet and geochronological data from Marie Byrd Land reveal (WAIS)
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From page 92... ...
The as labeled, corresponds to the western tectonic boundary of the West aim of this paper is to summarize the tectonic evolution of Antarctic Rift System. FM = Fosdick Mountains; EP = Edward VII western Marie Byrd Land (MBL)
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From page 93... ...
. Lower Paleozoic Swanson Formation The region corresponding to the Cretaceous WARS includes represents one of the packages of voluminous quartz-rich the Ross Sea and Ross Ice Shelf, the area of the WAIS, and turbidites deposited in regionally extensive clastic fans shed Marie Byrd Land (Behrendt, 1991, 1999; Behrendt et al., from the Ross-Delamerian Orogen (Fergusson and Coney, 1991; Cooper et al., 1991a,b; Storey et al., 1999; Trey et 1992)
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From page 94... ...
Mo it o nt u ain s 1000 l im 500 ed err 0 Inf -80 FIGURE 2 Eastern Ross Sea and western Marie Byrd Land location map. Inferred limits of extended crust and a subglacial volcanic field, determined from airborne geophysics (Luyendyk et al., 2003)
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From page 95... ...
, Fosdick gneiss dome in Marie Byrd Land (MBL) , and detachment systems are marked by ellipses.
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From page 96... ...
L= 5 F n = 16 E n=6 D n = 21 0 10 20 30 40 50 km Key to Units Q Basalt, Pleistocene K Byrd Coast Granite K Fosdick migmatite D-C Ford Granodiorite ePz Swanson Formation FIGURE 4 Structural-geological map of the Ford Ranges, western Marie Byrd Land. Inferred faults that are concealed by ice are mapped on the basis of contrasts in metamorphic grade between ranges, geophysical lineaments or boundaries, and zones of penetrative brittle deformation in rock exposures.
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From page 97... ...
Lateral flow of hot, weak, partially molten lower crust is accompanied by brittle deformation in shallow upper crust. Strain perturbation along faults allows localized gravity-driven vertical flow of lower-density migmatite-diatexite and formation of gneiss dome(s)
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From page 98... ...
New GEOLOGICAL STRUCTURE OF THE FORD RANGES, U-Pb SHRIMP zircon studies (Siddoway et al., 2004b, 2006; MARIE BYRD LAND: DATA BEARING ON TECTONISM McFadden et al., 2007) and isotope geochemistry (Saito et IN THE WEST ANTARCTIC RIFT SYSTEM al., 2007)
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From page 99... ...
. The leucogranites exhibit compositional layering and igneous microstructures, such as euhedral grains and til- 30 Bins, 2 Ma ing of large feldspars; together with evidence of magmatic solid-state deformation (Blumenfeld and Bouchez, 1988; 25 Fosdick Mountains, U-Pb zircon Weinberg, 2006)
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From page 100... ...
associated with inferred Cenozoic faults that trend NE-SW Outside of the Fosdick Mountains migmatite dome and offset the Fosdick Mountains gneiss dome (Figure 4, most exposures of crystalline rocks in the Ford Ranges lack inset B)
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From page 101... ...
They are generally southern Ford Ranges and Edward VII Peninsula appear to be parallel to the NNW-oriented, normal-sense and NE-striking, controlled by the NNW trend (Luyendyk et al., 2001; Wilson sinistral-sense, second generation shear fractures measured and Luyendyk, 2006; Sorlien et al., 2007) , and have a narrow, throughout the Ford Ranges and to the mafic dike array.
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From page 102... ...
AFT data existed at depth. Furthermore, no Late Cretaceous-Eocene fall within two age populations of 97-88 Ma and 80-70 Ma, sedimentary or volcanic strata crop out in Marie Byrd Land each characterized by long track lengths indicative of rapid (see Pankhurst et al., 1998)
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From page 103... ...
No geometrical or kinematic -76 -7 8° ° D U -7 9° D U ° 55 D -1 U ° D U U D -8 0° ° 50 -1 N 5° 0° -77 -14 -14 ° Swanson Formation High-gradient magnetic Low-density layer in metasedimentary outcrop anomaly (volcano) gravity model > 500 m Plutonic rock outcrop Low-gradient Ford | Byrd Coast magnetic anomaly Low-density bed topography FIGURE 7 Summary diagram of potential fields data and modeling (Luyendyk et al., 2003)
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From page 104... ...
. belt exemplifies this type of orogen as it has undergone In summary, examination of AFT data together with multiple cycles of contractional orogeny and extensional mapped structures shows that the early stage of rapid cool- collapse involving HT metamorphism (Foster et al., 1999; ing in western Marie Byrd Land at 95-85 Ma was localized Collins, 2002a,b; Gray and Foster, 2004; Fergusson et al., upon high-angle conjugate wrench zones.
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From page 105... ...
. Further cogranite derived from constituent gneisses of the Fosdick effects could arise from infiltration of fluids into the over- dome (phases of Ford Granodiorite, Swanson Formation)
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From page 106... ...
. Dominant wrench deformation is documented in Marie Byrd Land, and prevalent normal faulting is inferred in the Ross Sea.
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From page 107... ...
. faults in western Marie Byrd Land are viewed as contemThe association of the Fosdick Mountains gneiss dome with poraneous conjugate structures whose motion aided ENEthe Balchen Glacier fault, which is known to be an inherited WSW dextral transtension in the eastern WARS (Figure 4)
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From page 108... ...
. The stretching direction for the eastern WARS in Marie Byrd Land is consistent with the eastern WARS in MBL is generally parallel to that predicted current picture of tectonic plate interactions at the Phoenixfrom the orientation and geometry of basement grabens in the East Gondwana (Pacific sector)
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From page 109... ...
Journal of the Geo of Marie Byrd Land, West Antarctica, and correlation with northern logical Society of London 164:709-730. Victoria Land, East Antarctica and the South Island, New Zealand.
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From page 110... ...
1982. The reconstruction of New Zealand, over western Marie Byrd Land provide insight into magmatic arc base- Australia and Antarctica.
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From page 111... ...
Geochemistry Geophysics Geosystems, the Fosdick Migmatite Dome, Marie Byrd Land, West Antarctica.
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From page 112... ...
Origin and emplacement of a middle Cretaceous gneiss dome, superterranes in Marie Byrd Land, Antarctica. Journal of Geophysical Fosdick Mountains, West Antarctica.
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From page 113... ...
Burlini. of Edward VII Peninsula, Marie Byrd Land: Anorogenic magmatism Geological Society of London Special Publication 245:39-64.
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From page 114... ...
Magnetobiostratigraphic chronology of the Eocene-Oligocene West Antarctic rift system and Marie Byrd Land hotspot. Geology transition in the CIROS-1 core, Victoria Land margin, Antarctica; impli- 32:977-980.
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