Aspects of the evolution of the West Antarctic margin of Gondwanaland

Miscellaneous · Sun Jan 01 00:00:00 EST 1989

OSTI ID:6742341

Grunow, A M

A combination of paleomagnetism, structural field mapping, microprobe analysis, microfabric analysis and {sup 40}Ar/{sup 39}Ar geochronology was used to elucidate the history of the West Antarctic crustal block and the evolution of subduction complexes along the Scotia Ridge. West Antarctica is composed of four crustal blocks whose relationship to East Antarctica and to each other throughout the Phanerozoic is not well known. These blocks are: the Ellsworth-Whitmore Mountains (EWM); the Antarctic Peninsula (AP); Thurston Island (TI); Marie Byrd Land (MBL). Paleomagnetic sampling and analysis were conducted on rocks from the EWM and TI blocks in the hope of constraining the motion of these blocks and the opening history of the Weddell Sea. The paleomagnetic results suggest that the AP, EWM, and TI blocks have moved relative to East Antarctica prior to the mid-Cretaceous and that the main opening of the Weddell Sea was between the Early and mid-Cretaceous. Detailed field mapping was conducted on the subduction complexes of the Scotia Metamorphic Complex (SMC) on Smith Island and Elephant Island (Antarctica). Polyphase ductile deformation characterizes the Smith Island and Elephant Island tectonites. Microprobe analyses indicate that the blue amphiboles from both areas are primary crossite. Pressure-temperature estimates for Smith Island blueschist metamorphism are {approximately}350 C at 6-7 kbars. The {sup 40}Ar/{sup 39}Ar geochronology indicates a complex thermal evolution for the SMC. The north to south increase in intensity of deformation and metamorphism on Elephant Island corresponds to decrease in {sup 40}Ar/{sup 39}Ar age. Uplift of the Smith Island blueschists occurred since 47 Ma while most of the uplift on Elephant Island occurred since {approximately}102 Ma.

• Research Organization: Columbia Univ., New York, NY (USA)
• OSTI ID: 6742341
• Resource Relation: Other Information: Thesis (Ph. D.)
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
ANTARCTICA
CONTINENTAL CRUST
GEOLOGIC HISTORY
ANDES
ARGON 39
ARGON 40
DEFORMATION
ELECTRON MICROPROBE ANALYSIS
GEOLOGIC AGES
GEOLOGIC STRUCTURES
ISLANDS
ISOTOPE DATING
ISOTOPE RATIO
MAPPING
METAMORPHISM
MINERALOGY
MOUNTAINS
PALEOMAGNETISM
PLATE TECTONICS
SUBDUCTION ZONES
AGE ESTIMATION
ANTARCTIC REGIONS
ARGON ISOTOPES
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
CHEMICAL ANALYSIS
EARTH CRUST
EVEN-EVEN NUCLEI
EVEN-ODD NUCLEI
ISOTOPES
LIGHT NUCLEI
MAGNETISM
MICROANALYSIS
NUCLEI
POLAR REGIONS
RADIOISOTOPES
STABLE ISOTOPES
TECTONICS
YEARS LIVING RADIOISOTOPES
580000* - Geosciences