Geology Reference
In-Depth Information
Fig. 2.10
Strike-slip plate
boundaries in the Scotia
Sea (
yellow lines
). The
arrows
represent direction
and magnitude of the
relative velocity field
between plates pairs.
Numbers are magnitudes
of velocity in mm/year
Fig. 2.11
Flower structures associated with left-lateral transcurrent motion (From Frisch et al.
2011
)
oceanic regions, only few examples can be
found that belong to this class of boundaries.
In the South America - Antarctica - Pacific
system, the northern, the southern, and part of
the western boundary of the Scotia plate are
classic examples of strike-slip plate boundaries
(Fig.
2.10
). Other important examples are the
Owen Fracture Zone in the Arabian Sea (Fournier
et al.
2001
), the Cayman Trough transform
system along the present day North America -
Caribbean plate boundary (Pindell et al.
1988
),
and
oceanic domain analogues, in the case of tran-
scurrent boundaries the opposite is generally true.
For example, the magnitude of strike-slip motion
along modern transcurrent faults like the San An-
dreas Fault in western US (Pacific - North Amer-
ica boundary) and the North Anatolian Fault
in Turkey (Anatolia - Eurasia boundary) is re-
spectively of
47 mm yr
1
and
29 mm yr
1
,
while less than 8 mm yr
1
and11mmyr
1
can be observed, respectively along the Owen
Fracture Zone and around the Scotia plate. From
the structural point of view, transcurrent bound-
aries are generally associated with characteristic
flower structures at the upper crustal level, whose
complexity arises from the necessity of accom-
modating transpressional or transtensional com-
ponents within a prevalent strike-slip kinematics.
Figure
2.11
illustrates the typical structural set-
ting along these boundaries.
the
McDougall
Ridge
in
the
southwest
Pacific (Lebrun et al.
2003
).
We have mentioned that the continental coun-
terparts of the oceanic plate boundaries are zones
of active rifting, collision, or transcurrent motion.
It is interesting to note that while the average
relative velocity along rifts and orogenic belts
is one order of magnitude less than along the
