The South Armenian
Block (SAB) rifted away from the African margin in early to middle Jurassic
times, ~200-160 million years ago. It collided with the Eurasian margin
in the late Cretaceous (~83-70 million years ago), where it is still positioned.
The ages of rifting and collision are mainly based on geological evidence,
and a single paleomagnetic study, which is unsatisfactory for plate reconstructions.
The position of the
SAB with respect to the African and Eurasian margins that were separated
by a 3300 km wide ocean in the ~80-40 million years following rifting,
is not determined at all. Paleomagnetic research, that is based on magnetic
particles in rocks that align with the Earth’s dipolar magnetic field at
the time of deposition, is the only way to quantitatively provide paleolatitudes,
and should therefore be conducted in the region of the SAB to enable the
construction of paleogeographic reconstructions of the Tethys ocean.
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The
collision of the SAB with Eurasia in late Cretaceous times (~83 to 70 million
years ago) occurs much earlier than the accommodation of shortening in
the Kura fold-and-thrust belt that results from collision of Arabia, which
is very recent (only the last 5 million years!).
Both mechanisms however,
could explain the arc-shaped geometry north of the SAB. Using paleomagnetic
data, that provide not only paleolatitudes, but also rotational data, we
can exactly pinpoint the timing of formation of this arc-shaped geometry,
and therefore conclude what the responsible mechanism is. |
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