Publications
° Daczko, N.R., Mosher, S., Coffin, M.F. and Meckel, T.A., 2005.
Tectonic implications of fault-scarp-derived volcaniclastic deposits on Macquarie
Island: Sedimentation at a fossil ridge-transform intersection? Geological
Society of America Bulletin, 117, 18-31.
Abstract
Upper Miocene to lower Pliocene sedimentary rocks on Macquarie Island are
dominantly volcaniclastic breccia, sandstone, and siltstone produced by the
physical disintegration and tectonic abrasion of oceanic crust in fault zones,
and mass wasting of these tectonic features. They represent small debris
fans and small-scale turbidites deposited at the base of active fault scarps,
related to Late Miocene to Early Pliocene seafloor spreading. Most of the
sediment is derived from basalts, but diabase and gabbro clasts in some sedimentary
rocks indicate that middle and lower oceanic crust was exposed to erosion
on the sea floor. A lack of exotic clasts and a low degree of clast roundness
are consistent with a local source for the sediment and no input from continental
rocks. Spatial relationships between sedimentary rocks and major faults associated
with seafloor spreading on the island and correlation between sedimentary
clast and adjacent up-thrown block compositions allow us to infer paleo-tectonic
relief for Macquarie Island crust during deposition. Our data support a model
involving the deposition of these rocks at the inside corner of a ridge-transform
intersection. Furthermore, a tectonic reconstruction of the Australian-Pacific
plate boundary for the approximate time that Macquarie Island crust formed
(10.9 Ma) also shows that Macquarie Island crust most likely formed near
to a ridge-transform intersection. This paper describes sedimentation associated
with active faulting at a ridge-transform intersection that has been uplifted
in situ above sea level along with the surrounding oceanic crust, and demonstrates
that high-angle faults have the most pronounced influence, compared with
low-angle faults, on sedimentation in this tectonic environment.
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ARC Centre of Excellence for Core to Crust Fluid Systems