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Al-Saad, D., Sawaf, T., Gebran, A., Barazangi, M., Best, J. A., and Chaimov, T. A.
Crustal structure of central Syria: The intracontinental Palmyride Mountain belt
Tectonophysics, 207, 345-358, 1992.
Along a 450 km transect across central Syria seismic reflection data, borehole
information, potential field data and surface geologic mapping have been combined to
examine the crustal structure of the northern Arabian platform beneath Syria. The transect
is surrounded by the major plate boundaries of the Middle East, including the Dead Sea
transform fault system along the Levantine margin to the west, the Bitlis suture and East
Anatolian fault to the north, and the Zagros collisional belt to the northeast and east. Three
main tectonic provinces of the northern Arabian platform in Syria are crossed by this
transect from south to north: the Rutbah uplift, the Palmyra fold-thrust belt, and the
Aleppo plateau. The Rutbah uplift in southern Syria is a broad, domal basement-cored
structure with a thick Phanerozoic (mostly Paleozoic) cover of 6-7 km. Isopachs based on
well and seismic reflection data indicate that this region was an early Paleozoic depocenter.
The Palmyra fold-thrust belt, the northeastern arm of the Syrian Arc, is a northeast-
southwest trending intracontinental mountain belt that acts as a mobile tectonic zone
between the relatively stable Rutbah uplift to the south and the less stable Aleppo plateau to
the north. Short wavelength en echelon folds characterized by relatively steep, faulted
southeast flanks dominate in the southwest, most strongly deformed segment of the belt,
while a complex system of deeply rooted faults and broad folds characterize the northeast
region, described in this study. The Aleppo plateau lies immediately north of the Palmyride
belt, with a combined Paleozoic and Mesozoic sedimentary section that averages 4-5 km in
thickness. Although this region appears relatively undeformed on seismic reflection data
when compared to Palmyride deformation, a system of near vertical, probable strike-slip
faults crosscut the region in a dominantly northeasterly direction.
Gravity and magnetic modeling constrains the deep crustal structure along the transect.
The crustal thickness is estimated to be approximately 38 km. Interpretation of the gravity
data indicates two different crustal blocks beneath the Rutbah uplift and the Aleppo plateau,
and the presence of a crustal-penetrating, high-density body beneath the northeast
Palmyrides. The two distinct crustal blocks suggest that they were accreted possibly along
a suture zone and/or a major strike-slip fault zone located approximately in the present-day
position of the Palmyrides. The age of the accretion is estimated to be Proterozoic or early
Cambrian, based on the observation of a pervasive reflection (interpreted as the Middle
Cambrian Burj limestone) in the Rutbah uplift and in the Aleppo plateau and by analogy
with the well-mapped Proterozoic sutures of the Arabian shield to the south.
Key Figures and Captions
Map showing the western part of
including generalized geology of the Palmyride fold belt and location of the
transect that is the subject of this paper. Circles represent wells used for
seismic reflection profiles (narrow lines).
Portion of seismic line SB 13 showing the thickening of Mesozoic
strata (upper 0.5 sec) in the direction of the Euphrates depression to the east
and the onlap
of Silurian and Upper Ordovician rocks onto the Lower Ordovician. See Figure 1
Paleozoic extension. The nature of the difference between the Rutbah and
Aleppo crusts is uncertain because of the ambiguity plateau is either thinner
or denser than Rutbah crust.
Interpretive cross section to Moho (see Fig. 1 for location of transect).
The high-density intrusive body may be associated with early Paleozoic
extension. The nature of the difference between the Rutbah and Aleppo
crusts is uncertain because of the ambiguity plateau is either thinner
or denser than Rutbah crust.
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