Quantifying vertical movements in fold and thrust belts: subsidence, uplift and erosion in Kurdistan, northern Iraq

Abstract

Traditional structural analysis in fold and thrust belts has focused on quantifying horizontal movements. In this paper, the importance of quantifying vertical movements is illustrated using a case study from Kurdistan, northern Iraq. The subsidence history of this area can be determined by analysis of the stratigraphic record from deep exploration wells. A phase of thermal subsidence from Middle Permian to Late Cretaceous (tectonic subsidence 1.8-1.9 km) was followed by flexural subsidence in the Late Cretaceous and Cenozoic (tectonic subsidence >0.6 km) in response to the closure of the Neo-Tethys Ocean. The main phase of continental collision during the Neogene resulted in the development of the Zagros fold and thrust belt; the amount of uplift at individual anticlines can be estimated from their amplitude (up to 3 km), but regional cross-sections indicate that approximately 1 km of additional basement-involved uplift is present NE of the Mountain Front. The timing of basement-involved uplift is interpreted to be coeval with the deposition of a Pliocene-Quaternary growth sequence adjacent to the Mountain Front. The amount of erosion resulting from the uplift can be estimated from vitrinite reflectance and cross-sections; these estimates show a similar pattern, with maximum erosion in the mountains NE of the Mountain Front (>1.5 km) and lesser erosion in the adjacent foreland basin (generally <0.8 km). The results provide a quantitative understanding of subsidence, uplift and erosion, and have been used to define prospective and high-risk areas for petroleum exploration.

Relative timing of uplift along the Zagros Mountain Front Flexure (Kurdistan Region of Iraq): Constrained by geomorphic indices and landscape evolution modeling

“…To account for the provision of sediment due to hillslope diffusion processes from slopes outside the river system, we used the hillslope diffusion equation (Culling, 1963;Tucker and Bras, 1998):…”

Late Miocene Deformation Kinematics Along the NW Zagros Fold‐Thrust Belt, Kurdistan Region of Iraq: Constraints From Apatite (U‐Th)/He Thermochronometry and Balanced Cross Sections

“…These differences in structural levels are well expressed in regional geologic maps, such that Cretaceous rocks are exposed in the internal hinterland, mostly Paleogene rocks in the more external hinterland, and dominantly Neogene rocks toward the foreland (Figure 2b). In addition, Neogene deposits in hinterland synclines are preserved at higher structural levels (higher elevation) compared to their foreland equivalents (Koshnaw et al, 2017; Le Garzic et al, 2019; Tozer et al, 2019). For both the Erbil and Sulaimani cross sections, using the top of the Neogene Fatha Formation and top of the Cretaceous rocks, the estimated structural elevation gain is ~2.5–3 km for a hinterland width of ~40–50 km over a ~200 km length.…”

“…Arrow vectors represent GPS-derived plate motion velocities of the Arabia and Anatolia relative to Eurasia (Authemayou et al, 2006). scale fault ramps beyond the seismogenic depth of brittle deformation (~25-30 km) (Abdulnaby et al, 2014;Engdahl et al, 2006;Karasözen et al, 2019;Nissen et al, 2019) to explain surface uplift (Tozer et al, 2019). Additionally, the mode of deformation advance has also been debated.…”

“…However, others invoke a hybrid thin‐ and thick‐skinned style of shortening (Allen et al, 2013; Leturmy et al, 2010; Mouthereau et al, 2006; Mouthereau, Lacombe, et al, 2007; Mouthereau, Tensi, et al, 2007; Oveisi et al, 2009; Sherkati et al, 2006), involving either in‐sequence (Saura et al, 2015; Vergés, Goodarzi, et al, 2011) or out‐of‐sequence deformation (Blanc et al, 2003; Molinaro, Leturmy, et al, 2005). In the Kurdistan region of Iraq, regional cross sections of the fold‐thrust belt and adjacent foreland variably show thin‐skinned (Hinsch & Bretis, 2015) or hybrid thin‐ and thick‐skinned geometries (de Vera et al, 2009; Le Garzic et al, 2019; Tozer et al, 2019; Zebari et al, 2020). Whereas others solely focused on the uppermost sedimentary cover with no interpretation of structures below Jurassic strata (e.g., Frehner et al, 2012; Reif et al, 2011).…”

Petroleum tectonic comparison of fold and thrust belts: the Zagros of Iraq and Iran, the Pyrenees of Spain, the Sevier of Western USA and the Beni Sub-Andean of Bolivia

“…Figure 6 shows the late Zagros deformation front (ZDF) in Lurestan does not advance much (short blue arrow) while the slope (α) increases. Additionally, to the north in Iraqi Kurdistan, Koshnaw et al (2017) and Tozer et al (2019) have documented a c. 5 Ma activation of the MFF, c. 80-100 km behind the low-taper deformation front. Furthermore, drainage reorganization and changes in the channel fill characteristics have likely been created by the increasing taper (Vergés 2007;Mouthereau et al 2012).…”