Deciphering continental breakup in eastern Australia using low-temperature thermochronometers

Persano, C., Stuart, F.M., Bishop, P. and Dempster, T.J. (2005) Deciphering continental breakup in eastern Australia using low-temperature thermochronometers. Journal of Geophysical Research: Solid Earth, 110, B12405. (doi: 10.1029/2004JB003325)

Abstract

First-order topographical features at high-elevation passive margins have the potential to store information about the early stages of continental rifting, which are usually lost in the sediment record. In this study we present a new combination of apatite fission track and (U-Th)/He analyses from two coast-perpendicular traverses to decipher the time of formation and evolution of the escarpment at the southeastern Australian margin. A combination of inverse and forward modeling of the apatite fission track (AFT) and He data indicates that the coast experienced a rapid denudational event starting at 110 ± 10 Ma, at least 15 Myr before seafloor spreading (85 Ma), in agreement with the hypothesis that rifting at magma-poor margins evolves slowly. Thus the enhanced denudation is not related to the synbreakup base level drop, but it may have been related to a thermally driven transient surface uplift. Considerations on isostatic flexure and rigidity of the lithosphere indicate that unless significant synrift brittle movements are assumed to have occurred along margin-parallel faults that are no more visible, the coast must have experienced a higher geothermal gradient than normal. The evolution of the rest of the coastal plain may have taken up to ∼90 Myr, in agreement with numerical models of passive margins evolution. The (U-Th)/He ages across the coastal plain are consistent with an in-place-excavation scenario of a high rift shoulder, and they rule out the possibility of a constant retreat of the escarpment. AFT + He data from the plateau indicate that the highlands remained stable throughout continental breakup, experiencing rates of erosion of 5–10 m/Myr since, at least, 200 Ma.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Dempster, Dr Tim and Stuart, Professor Fin and Persano, Dr Cristina and Bishop, Professor Paul
• Authors: Persano, C., Stuart, F.M., Bishop, P., and Dempster, T.J.
• Subjects: G Geography. Anthropology. Recreation > GE Environmental Sciences
• College/School: College of Science and Engineering > Scottish Universities Environmental Research Centre; College of Science and Engineering > School of Geographical and Earth Sciences
• Journal Name: Journal of Geophysical Research: Solid Earth
• ISSN: 1934-8843
• ISSN (Online): 1934-2098