Tectono-stratigraphic evolution of the intermontane Tarom Basin (NW
sectors of the Arabia-Eurasia collision zone): insights into the
vertical growth of the Iranian Plateau margin
Abstract
The intermontane Tarom Basin of NW Iran (Arabia-Eurasia collision zone)
is located at the transition between the Iranian Plateau (IP) to the SW
and the Alborz Mountains to the NE. This basin was filled by Late
Cenozoic synorogenic red beds that retain first-order information on the
erosional history of adjacent topography, the vertical growth of the
plateau margin and its lateral (orogen perpendicular) expansion. Here,
we perform a multidisciplinary study including magnetostratigraphy,
sedimentology, geochronology and sandstone petrography on these red
beds. Our data show that widespread Eocene arc volcanism in NW Iran
terminated at ~ 38-36 Ma, while intrabasinal synorogenic
sedimentation occurred between ~ 16.5 and <
7.6 Ma, implying that the red beds are stratigraphically equivalent to
the Upper Red Formation. After 7.6 Ma, the basin experienced
intrabasinal deformation, uplift and erosion in association with the
establishment of external drainage. Fluvial connectivity with the
Caspian Sea, however, was interrupted by at least four episodes of basin
aggradation. During endorheic conditions the basin fill did not reach
the elevation of the plateau interior and hence the Tarom Basin was
never integrated into the plateau realm. Furthermore, our provenance
data indicate that the northern margin of the basin experienced a
greater magnitude of deformation and exhumation than the southern one
(IP margin). This agrees with recent Moho depth estimates, suggesting
that crustal shortening and thickening cannot be responsible for the
vertical growth of the northern margin of the IP, and hence surface
uplift must have been driven by deep-seated processes.