The goal of this project is to address relationships between foreland basins and their tectonic settings by combining detrital zircon isotope characteristics and sedimentological data. To accomplish this goal the PIs will develop a detailed geochronology and analyze Hf- and O-isotopes of detrital zircons in sandstones of the Devonian Taylor Group and the Permian-Triassic Victoria Group. These data will allow them to better determine provenance and basin fill, and to understand the nature of the now ice covered source regions in East and West Antarctica. The PIs will document possible unexposed/unknown crustal terrains in West Antarctica, investigate sub-glacial terrains of East Antarctica that were exposed to erosion during Devonian to Triassic time, and determine the evolving provenance and tectonic history of the Devonian to Triassic Gondwana basins in the central Transantarctic Mountains. Detrital zircon data will be interpreted in the context of fluvial dispersal/drainage patterns, sandstone petrology, and sequence stratigraphy. This interpretation will identify source terrains and evolving sediment provenances. Paleocurrent analysis and sequence stratigraphy will determine the timing and nature of changing tectonic conditions associated with development of the depositional basins and document the tectonic history of the Antarctic sector of Gondwana. Results from this study will answer questions about the Panthalassan margin of Gondwana, the Antarctic craton, and the Beacon depositional basin and their respective roles in global tectonics and the geologic and biotic history of Antarctica. The Beacon basin and adjacent uplands played an important role in the development and demise of Gondwanan glaciation through modification of polar climates, development of peat-forming mires, colonization of the landscape by plants, and were a migration route for Mesozoic vertebrates into Antarctica.
Broader impacts: This proposal includes support for two graduate students who will participate in the fieldwork, and also support for other students to participate in laboratory studies. Results of the research will be incorporated in classroom teaching at the undergraduate and graduate levels and will help train the next generation of field geologists. Interactions with K-12 science classes will be achieved by video/computer conferencing and satellite phone connections from Antarctica. Another outreach effort is the developing cooperation between the Byrd Polar Research Center and the Center of Science and Industry in Columbus.
The research in this collaborative project between the Ohio State University (OSU) and the University of Wisconsin-Milwaukee (UWM) was designed to investigate the late Paleozoic and Mesozoic tectonic and environmental history of Antarctica; to identify Antarctica’s importance to the tectonics of Gondwana; and to address how tectonics and basin development influenced Antarctica’s geologic, biologic, and climactic history. During the late Paleozoic and Mesozoic, Gondwana switched from continental assembly to crustal block dispersal. This interval included Earth’s last complete transition from an icehouse to a greenhouse (hothouse) state and Earth’s largest mass extinction event. This project consisted of a detailed study of the geochronology and Hf- and O-isotope characteristics of detrital zircons in Devonian, Permian, and Triassic sandstones to understand the provenance and tectonic nature of the source regions now covered by ice in Antarctica and/or rifted away from the continent (OSU), and basin and facies analyses to understand provenance, basin fill, basin evolution, and changing environmental conditions during the late Paleozoic and Mesozoic (UWM). During the late Paleozoic Ice Age (LPIA) and the ensuing transition into the late Permian and Mesozoic warm interval, Antarctica was located in a polar or near polar position. During that time, the Transantarctic Basin and adjacent uplands played an important role in the development and demise of Gondwana glaciation, modification of the polar climate, colonization of the post-glacial landscape by plants, development of peat-forming mires, and as a migration route for Mesozoic vertebrates into Antarctica. Results indicate that strata in the central Transantarctic Mountains (CTAM) record the evolution from a Devonian to Early Permian rift basin into a mid/late Permian-Triassic foreland basin. Formation and evolution of these basins resulted from convergent margin tectonism along the Panthalassan Margin with magmatism occurring from the late Carboniferous until the Triassic. This activity resulted in an influx of magmatic zircons as well as older zircons derived from uplifted and eroded terrains of the Ross Orogenic belt. During the Early Permian, back-arc rifting in CTAM produced several narrow, deep basins. At that time, climatic conditions favored the formation of numerous, small, ice sheets across polar Gondwana with nucleation of the glaciers on the rift shoulders at elevations above the Equilibrium Line Altitude (ELA; elevation above which snow persist from year to year). During the LPIA, the ELA was influenced by fluctuations in insolation driven by Earth’s orbital parameters, tectonism, precipitation, and upwelling of cold bottom waters along the margin of Gondwana. An abrupt rise in the ELA in the late Sakmarian (Early Permian) due to a rapid increase in atmospheric CO2 levels resulted in rapid deglaciation throughout polar Gondwana. Following this event, glaciers were absent in Antarctica until the late Cenozoic. However, glaciers continued to occur in eastern Australia at high elevations until the Capitanian (late Middle Permian). This discrepancy between mid-latitude glaciation and ice-free conditions in polar Gondwana indicates that major global cooling did not play a role in the development of the Australian glaciers. Although glacial and interglacial periods within an ice age are driven by orbitally driven changes in insolation, our results support the concept that icehouse to greenhouse climatic states are driven by changes in the level of greenhouse gasses within the atmosphere. Following the LPIA, CTAM basins shallowed upward from deep marine, to deltaic, to fluvial environments. Plants began colonizing the landscape immediately following glacial retreat. Continued tectonism resulted in the transformation of CTAM into a poorly drained elongate, trough-shaped, foreland basin in the Middle Permian. Although the basin margins were characterized by large braided streams, large lakes and extensive peat-forming mires developed along the basin axis. This wet hydroclimate allowed the Glossopteris flora to dominate. However, the setting was not conducive to establishment of vertebrates. During the latest Permian and into the Triassic, clastics filled the basin producing an alluvial plain that sloped steeply away from the orogenic belt. This change from an under-filled to an over-filled basin resulted in a change to a dryer/better drained hydroclimate, which allowed for colonization of CTAM by vertebrates. This research is providing geoscientists and society with a better understanding of the evolution of the Antarctic continent and a better understanding of global climate change. Our work is helping to understand the tectonic development of the Transantarctic depositional basins, the architecture and development of the Antarctic continent, the duration and extent of the Late Paleozoic Ice Age, and how future climate change may proceed as we move from an ice house to a greenhouse world. This grant has provided 5 graduate and 6 undergraduate students opportunities to work on timely topics associated with the evolution of the Antarctic continent and global environmental change. Normal 0 false false false EN-US X-NONE X-NONE
