Structural Implications of Slickensides and the Juneau Icefield, Juneau, AK and Atlin, B.C.
A. J. ROMEO, Univ. of Florida, Dept. of Geology, Gainesville, 32611, and Foundation for Glacier and Environmental Research, Pacific Science Center, Seattle, WA 98019.
Slickensides of the Juneau Icefield record rapid early to mid-Tertiary uplift of the Coast Range batholith. Orientations of 225 slickensides reflect a regionally extensive set of ductile shear and brittle faults extending ~60 km southwest to northeast through the study area north of Juneau, Alaska. This shear zone contains near vertical eastward dipping slickensides with horizontal slickenlines recording right- and left-lateral strike-slip motion. This shear zone, informally named the Seratine shear zone, is in the northern extremities of the Coast shear zone and evolved from thrusting along the Coast Range Megalineament zone during rapid early-Tertiary uplift. No significant measurement of displacement was recorded in the Eocene granite and granodiorite plutons.
Funded in part by a grant from the National Science Foundation Research Experience for
Undergraduates (NSF-REU).
Here is one of my study areas: The Gilkey Trench. You can go
on this expedition yourself, surf to FGER.
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This animation shows the faulting process. The different fill patterns represent horizontal rock units. Can you see how one rock mass moves past another as they are faulted? It is along this fault line that the slickensides occur. |
This chunk of chalcedony and serpentine is host to the 'Mother of All Slickensides' (story) because it has some quality slickenlines [lines
etched on the rock face during tectonic activity]. The chalcedony vein (which contains the
slickenlines) was injected in to the serpentine country rock prior to the faulting
process. I've doctored-up the image to make the slickenlines more evident.
