2013 Spring Geologic Field Work, South Island of New Zealand
CWU Geology Professor Jeff Lee and colleague Nick Mortimer, GNS Science,
New Zealand spent parts of February and March, 2013 conducting field
studies to examine and document evidence for ductile and brittle
extensional exhumation of the Otago Schist in the central part of the
South Island. The Otago Schist is a metamorphosed accretionary prism,
similar to accretionary prism rocks exposed in the Olympic Mountains, that
developed within the eastern Gondwana subduction zone. Marine sediments
that were metamorphosed to ~25-30 km depth and ~500°C are the protolith
for the Otago Schist. Several different processes have been proposed for
the development of these strongly ductilely deformed and metamorphosed
rocks and for the exhumation of these rocks to the Earth’s surface. Jeff
and Nick are combining field studies, mesoscopic and microscopic
structural studies, and thermochronology to determine whether ductile and
brittle extensional deformation contributed to the formation of the schist
and to its exhumation history.
The tors on top of the Dunstan Range provide excellent exposure
of strongly ductilely extended (vertically thinned and horizontally
stretched) metamorphic rocks.
Jeff taking field notes besides strongly foliated metamorphic rocks
(foliation dips towards Jeff) cut by quartz veins.
The top of the Cairnmuir Mountains defines the hanging wall of a
normal fault and is underlain by less deformed rocks compared to those exposed in the
Incredible (remarkable?) folding in the The Remarkables.
The southerlies bring snow to the Dunstan Range during the summer
No rattlesnakes, no scorpions, and no predators to worry
about, but armed goats?