Possible forced folding in the Taurus–Zagros Belt of northern Iraq

Abstract

The folds in the Taurus–Zagros Belt of northern Iraq have generally been considered to be decollement buckle folds. This implies the presence of a decollement horizon at or near the base of the sedimentary cover, the ‘Infra-Cambrian Hormuz Salt’ and a passive role of the Precambrian basement in the tectonic evolution of the folded belt. Structural, stratigraphic, geophysical and remote sensing evidence suggests that forced folding, due to faulting in the basement, has played a significant role in the development of many of the folds in this region. This is clear from the substantial evidence of basement faulting, the lack of any convincing evidence for the presence of an extensive and regional decollement horizon (i.e. the Hormuz Salt) between the basement and the cover rocks, and the geometries of the folds and related mesostructures. The study shows that in the Taurus Foothills Zone, the folds are short, oval in plan shape, and arranged in an en echelon pattern along two sets of dislocation zones in the basement. However, the folds in the Zagros Foothills Zone are longer, linear and arcuate in plan shape. Many of the studied folds show similar features to those observed in the Rocky Mountains, U.S.A.

Orogenic plateau growth: Expansion of the Turkish‐Iranian Plateau across the Zagros fold‐and‐thrust belt

“…One end-member model emphasizes detachment of the cover from the basement, particularly along the Hormuz Series salt, but also on lateral equivalents where the evaporites are not known to exist [Stöcklin, 1968;McQuarrie, 2004;Yamato et al, 2011]. The other end-member links each exposed fold to a basement thrust [Ameen, 1991]. It is entirely feasible that both thick-skinned and thin-skinned styles of deformation occur in the range, with multiple detachments within the sedimentary cover, co-eval with basement thrusts [Blanc et al, 2003;Ahmadhadi et al, 2007;Casciello et al, 2009;Mouthereau et al, 2006;2007].…”

The Configuration of the Basement Beneath the Zagros Basin

“…2;Al Laboun, 1986;Alsharhan and Nairn, 1997). Such structures are referred to as lineaments, blind or hidden basement faults (Berberian, 1995), geo-flexures (Falcon, 1974), geowarps (Ameen, 1991(Ameen, , 1992, periclines (Alsharhan, 1989), drape folds (Edgell, 1991) or forced folds (Sattarzadeh et al, 2000). Most have had long histories of activity that began before the Late Palaeozoic (e.g.…”

The Effect of Basement Fault Reactivation on the Triassic – Recent Geology of Kurdistan, North Iraq

“…relating to the position of basement faults, may also control the distribution of the Hormuz salt within the Persian Gulf. The salt unit is absent in the Dezful Embayment in Iran, potentially present in the Lurestan Salient, and present in the Fars Salient (Ameen, 1991;Casciello et al, 2009). Diapirs within the Persian Gulf indicate that the Hormuz salt was remoblilized along Nabitahsystem faults (Alsharhan and Kendall, 1986;Edgell, 1996) during the Cretaceous.…”

“…a magnitude 5.1 event close to Erbil on July 18, 2009, as listed in the USGS catalogue) indicate that the area is still tectonically and seismically active. %DVHPHQW VWUXFWXUHV VSHFL¿FDOO\ WKH 1:6( WUHQGLQJ set, are considered to be involved in the deformation of the present-day Iraqi Zagros, given that earthquake focal depths appear to be located at depths greater than the total depth of the sedimentary pile (Ameen, 1991;Carruba et al, 2006;De Vera et al, 2009;Kent, 2010). Shortening across different sectors of the Zagros foldthrust belt is estimated at 16-30 % in Iran (Alavi, 2007), and at 33% in the Kirkuk Embayment (Ibrahim, 2009).…”