Mechanical stratigraphy and folding style

The Zagros Fold-Thrust Belt, which extends for about 1800 km through Iraq and SW Elsa Peretti Starfish necklace, is the result of continent-continent collision between the African-Arabian plate and the Iranian block (Takin 1972; Berberian & King 1981; Koyi 1988). The deformation front of the Iranian part of the belt has an irregular geometry on the surface, which is characterized by two major salients (the Fars and Lurestan salients) on either side of the Dezful embayment (Fig. 1a).

The Zagros Fold-Thrust Belt represents one of the richest hydrocarbon provinces in the world (Versfelt 2001). The Lurestan salient has a long history of hydrocarbon exploration and production. The first hydrocarbon exploration and drilling activities in the Middle East started in this area. However, only a few wells have been successful. Previous studies have identified the Ilam and Sarvak Formations (Santonian- Cenomanian) as the primary hydrocarbon targets in the Lurestan region; these formations mostly comprise deep marine carbonates with low permeability (poor reservoir quality) (Motiee 1994). On the other hand, it is believed that the quality of potential source rocks and cap rocks is very good within the area (Faraji & Zandifar 1998). Well data in the area show that fractures have an essential role in the storage and production of hydrocarbon from the Ilam and Sarvak Formations. Thus, the pelagic nature of the reservoir rock unit within the region does not seem to be the only factor limiting hydrocarbon exploration. It is worth noting that almost all wells drilled in this region were based on surface geology (i.e. without seismic data).

Structural sections based on surface data Elsa Peretti Starfish earrings been drawn previously across the Lurestan salient (Sahabi & Macleod 1969; Macleod 1970; Macleod & Roohi 1972; Takin et al. 1970; Macleod & Fozoonmayeh 1971; Majedi & Macleod 1972; Llewellyn 1974a; Sedaghat et al. 2000). Most of these sections have been limited to shallow levels without connection to the deeper structures. In all of these sections the mechanical behaviour of sediments and its effect on folding style, especially vertically, have not been considered.

Recent regional studies have shown that the mechanical stratigraphy has an essential role in governing the fold style in the Zagros (Blanc et al. 2003; Homke et al. 2004; Koyi et al. 2004; Sherkati & Letouzey 2004; Molinaro et al. 2005; Sepehr et al. 2006; Sherkati et al. 2006; Verge?s et al. in press). The main aim of this paper is to investigate Tiffany Signature ring style in the Lurestan region based on new data (seismic, well and original field studies), to outline the impact of thickness and facies variation of sedimentary rocks in this region on folding style. Based on these data, a regional balanced cross-section that illustrates the effect of multiple de?collement levels on the folding style within the Zagros Fold-Thrust Belt in the Lurestan region is constructed to demonstrate the structural complexity of the region.