Area
Balanced
Crustal Cross-Section across the NW Zagros
Belt and Late Cretaceous Arabian Margin Reconstruction: Shortening and
Deformation Sequence
Vergés, Jaume 1; Saura, E. 1; Casciello, E. 1;
Fernàndez, M. 1; Villaseñor, A. 1; Jiménez-Munt, I. 1;
Garcìa-Castellanos, D. 1
(1)Group of Dynamics of the Lithosphere -
GDL, Barcelona, Spain.
New area balanced
and restored cross-sections are constructed
across the NW Zagros Fold Belt in Lurestan in Iran integrating new geological
observations and local and global geophysical datasets. The
balanced
cross-section is pinned in the Mesopotamian foreland (non-deformed Arabian
crust) near the Iraq-Iran border at 20 km to the south-west of the Mountain
Frontal Flexure. The top of the area
balanced
corresponds to the near top
Sarvak Formation (main HC reservoir, Late Cretaceous in age at around 90 Ma).
This level together with the Oligocene-Miocene Asmari level (main Tertiary HC
reservoir) show a fairly continuous outcrop along the study transect. The base
of the Arabian crust is defined in recently published receiver functions
results showing deepening of the Moho from about 42 km in the non-deformed
crust to 56 km below the inner regions of the Zagros. The present boundary
between Arabia and Eurasia plates is defined by new seismic tomographic
sections displaying a sharp contact, dipping about 50° to the north-east
separating a relatively fast lithosphere in the south-west (Arabia) and a slow
and warmer lithosphere beneath Iran. These four limits constrain a crustal area
of 10,800 km² that is used to determine the restored structure of the Arabian
margin before compression.
The quantified reconstruction of the Arabian margin during Late
Cretaceous times assumes area conservation through compressive deformation. In
addition, the Arabian margin is divided in 6 different tecto-sedimentary
domains according to their sedimentary facies and paleobathymetries and
assuming Airy isostasy. Using these constraints we reconstruct an Arabian
margin that extent about 169 km further to the north-east of the present
position of the Main Reverse Fault (MRF), which is considered the actual
boundary between Arabia and Iran.
The direct comparison between balanced
and restored cross-sections
indicates a much larger shortening than previously calculated using field data
only. The Arabian basement rocks shortened ~149 km (39%). Interestingly, the
Arabian cover rocks shortened about ~180 km (47%), which include all
compressive events from Late Cretaceous obduction through Miocene continental
collision, spanning about 90 Myr.
Line-length balancing technique applied to the near top Sarvak Formation in the Simply Folded Belt only determine 21 km of shortening (11%), which mostly accounts for the growth of the superbly developed whale-back anticlines from early Miocene to
AAPG Search and Discovery Article #90135©2011 AAPG International Conference and Exhibition, Milan, Italy, 23-26 October 2011.