Neogene sediments and modern depositional environments of the Zagros foreland basin system

Pirouz, Mortaza; Simpson, Guy; Bahroudi, Abbas; Azhdari, Ali

doi:10.1017/s0016756811000392

Cited by 79 publications

(38 citation statements)

References 58 publications

(115 reference statements)

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“…Based on a detailed facies analysis, a retrogradational shallowing‐up succession is proposed for the infilling of the Azanak Minibasin, which supports the regional shallowing‐upward sedimentary evolution determined in the Zagros foreland (e.g. Pirouz et al., ) that migrated from northeast to southwest (e.g. Vergés, ).…”

Section: Discussionsupporting

confidence: 61%

“…Ballato et al., ; Homke, Vergés, Garcés, Emami, & Karpuz, ; Homke et al., ; Khadivi et al., ; Madanipour et al., ; Mouthereau et al., ; Pirouz, Avouac, Hassanzadeh, Kirschvink, & Bahroudi, ; Ruh, Hirt, Burg, & Mohammadi, ). The evaporites of the lower—middle Miocene Gachsaran Formation are interpreted as having been deposited in a forebulge sabkha environment at the onset of deposition of the Zagros foreland succession (Pirouz, Simpson, Bahroudi, & Azhdari, ; Pirouz, Simpson, & Chiaradia, ). The Gachsaran Formation is composed of halite, gypsum, anhydrite, mudrock and thin‐bedded limestone, divided into seven members (of which the fourth is a thick salt unit), forming the most significant intermediate ductile horizon (the Upper Mobile Group) between the underlying Competent Group and the overlying Passive Group.…”

Section: Stratigraphy and Tectonics Of The North Dezful Embaymentmentioning

confidence: 99%

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Folding, thrusting and diapirism: Competing mechanisms for shaping the structure of the north Dezful Embayment, Zagros, Iran

et al. 2018

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Differentiating compressional growth strata from halokinetic sequences is not straightforward in foreland fold‐and‐thrust belts where compressional and diapiric processes were coeval. Although there are numerous studies on the role of salt layers in fold‐and‐thrust belts, very few focus on syntectonic evaporites where they are thick enough to develop diapirism. The tectonic structures of the northern Dezful Embayment, along the footwall of the Zagros Mountain Front Fault, show a complex evolution interpreted in this study by the concurrence of folding, thrusting and pre‐ and syn‐shortening diapirism of the lower Miocene Gachsaran evaporites. We explore this tectonic–diapiric–sedimentary interplay by combining field studies and remote‐sensing mapping, detailed stratigraphy and sedimentology, high‐quality seismic data, and step‐by‐step balanced tectono‐sedimentary restorations. Initial diapirism occurred soon after the deposition of at least 1.5 km thick Miocene Gachsaran evaporites during the sedimentation of up to 5 km thick Aghajari, Lahbari and Bakhtyari formations, which display syntectonic mixed growth strata and halokinetic sequences. These sedimentary sequences filled salt‐related minibasins, from which the Azanak Minibasin is the deepest, limited by growing salt walls and salt anticlines (Azanak thrust‐weld and the Saland–Lali anticline). Palaeocurrents and clasts compositions document fluvial diversions and exposure and erosion of Gachsaran evaporites along the active salt walls. Although, by further shortening, the precursor salt walls squeezed and reactivated as thrust‐welds structuring a duplex of overriding minibasins. During the deposition of the middle‐late Miocene Aghajari Formation, Kazhdumi and Pabdeh source rocks were buried to oil‐expulsion depths, and Sarvak and Asmari reservoirs were mildly folded in large and open anticlines. The Gachsaran system in the northern Dezful Embayment is collated with the structures of preshortening Hormuz salt and syn‐shortening Fars salt to highlight the important role of these ductile units in the tectonic evolution of the Zagros fold belt that is compared to syn‐compressional salt‐related Pyrenees, Carpathians, Sivas and Kuga fold belts.

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Section: Discussionsupporting

confidence: 61%

Section: Stratigraphy and Tectonics Of The North Dezful Embaymentmentioning

confidence: 99%

Folding, thrusting and diapirism: Competing mechanisms for shaping the structure of the north Dezful Embayment, Zagros, Iran

et al. 2018

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“…The Mesopotamian basin consists of an extensive, low relief flood plain occupied by several major meandering rivers, for example, Tigris and Euphrates to the northwest of the Persian Gulf. The sedimentary facies of the Neogene foreland basin deposits can be tracked to the surface and they remarkably match the modern sedimentary environments (Pirouz et al 2011).…”

Section: G E O L O G I C a L S E T T I N G O F N O Rt H E R N E D G Ementioning

confidence: 88%

“…This formation includes ca. 1 km of evaporitic deposits and variegated marl interbeds in Iran, which is thinner in Iraq and Syria, and has a clastic equivalent known as the Razak formation in the High Zagros and Fars areas (Motiei 1993;Pirouz et al 2011). This formation separates the overlying foreland basin deposits from the older platform carbonates, i.e.…”

Section: G E O L O G I C a L S E T T I N G O F N O Rt H E R N E D G Ementioning

confidence: 99%

Flexural bending of the Zagros foreland basin

Pirouz¹,

Avouac²,

Gualandi³

et al. 2017

Geophysical Journal International

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S U M M A R YWe constrain and model the geometry of the Zagros foreland to assess the equivalent elastic thickness of the northern edge of the Arabian plate and the loads that have originated due to the Arabia-Eurasia collision. The Oligo-Miocene Asmari formation, and its equivalents in Iraq and Syria, is used to estimate the post-collisional subsidence as they separate passive margin sediments from the younger foreland deposits. The depth to these formations is obtained by synthesizing a large database of well logs, seismic profiles and structural sections from the Mesopotamian basin and the Persian Gulf. The foreland depth varies along strike of the Zagros wedge between 1 and 6 km. The foreland is deepest beneath the Dezful embayment, in southwest Iran, and becomes shallower towards both ends. We investigate how the geometry of the foreland relates to the range topography loading based on simple flexural models. Deflection of the Arabian plate is modelled using point load distribution and convolution technique. The results show that the foreland depth is well predicted with a flexural model which assumes loading by the basin sedimentary fill, and thickened crust of the Zagros. The model also predicts a Moho depth consistent with Free-Air anomalies over the foreland and Zagros wedge. The equivalent elastic thickness of the flexed Arabian lithosphere is estimated to be ca. 50 km. We conclude that other sources of loading of the lithosphere, either related to the density variations (e.g. due to a possible lithospheric root) or dynamic origin (e.g. due to sublithospheric mantle flow or lithospheric buckling) have a negligible influence on the foreland geometry, Moho depth and topography of the Zagros. We calculate the shortening across the Zagros assuming conservation of crustal mass during deformation, trapping of all the sediments eroded from the range in the foreland, and an initial crustal thickness of 38 km. This calculation implies a minimum of 126 ± 18 km of crustal shortening due to ophiolite obduction and post-collisional shortening.

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“…The Zagros foreland exhibits a variety of active depositional environments. From the Arabian plate towards the Zagros Mountains, a transition from sabkha and supratidal environments to carbonate ramp (distal foredeep), marine basin and coastal plain (foredeep) and finally to meandering and braided river systems (wedge-top) can be noticed (Pirouz et al, 2011). According to Sepehr and Cosgrove (2005), after the Permo-Triassic rifting event leading to the JurassicMiddle Cretaceous setting of the Arabian Tethyan margin and the Zagros passive continental margin, the Late Cretaceous tectonic evolution was governed by the obduction of the Tethyan ophiolites onto the Arabian margin.…”

Section: Geological Setting and Previous Workmentioning

confidence: 99%

Facies analysis and sequence stratigraphy of the Asmari Formation in the northern area of Dezful Embayment, south-west Iran

Zoeram¹,

Vahidinia²,

Mahboubi³

et al. 2013

Studia UBB Geologia

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Abstract. This paper deals with the sequence stratigraphy of the Oligocene (Rupelian-Chattian)-Early Miocene (Burdigalian) Asmari Formation based on microfacies analysis of the sediments in the Ghale Nar Oilfield, central area of Zagros fold-thrust belt. Fourteen facies types typical for upward shallowing trend from open marine (MF 1-3), to shoal (MF 4-5), semi-restricted and restricted lagoon , and finally to near-shore lagoon (MF 13-14) depositional environments were identified. Based on the environmental interpretations, we reconstructed a homoclinal ramp mainly represented by its inner and middle sectors. Facies types MF 4-14 are characterized by the occurrence of large and small porcelaneous benthic foraminifera representing a shallow-water setting of an inner ramp influenced by wave-and tide-related processes. MF1 (Pabdeh Formation), and 2-3 with planktonic, large and small hyaline benthic foraminifera represent between fair weather wave base (FWWB) and storm wave base (SWB). Four third-order depositional sequences were recognized. In order to better correlate the identified sequences with those pre-defined of the Asmari Formation in the Dezful Embayment and the Izeh zone that are chronologically well-known, we use their number instead of their name. Sequence 2 mainly consists of an open marine environment in the base, followed by semi-restricted to restricted lagoonal facies. Sequences 36 are characterized by semi-restricted to restricted lagoonal facies. Moreover, the regional relative sea-level change curves correlate well with the global sea-level change curves.

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Neogene sediments and modern depositional environments of the Zagros foreland basin system

Cited by 79 publications

References 58 publications

Folding, thrusting and diapirism: Competing mechanisms for shaping the structure of the north Dezful Embayment, Zagros, Iran

Folding, thrusting and diapirism: Competing mechanisms for shaping the structure of the north Dezful Embayment, Zagros, Iran

Flexural bending of the Zagros foreland basin

Facies analysis and sequence stratigraphy of the Asmari Formation in the northern area of Dezful Embayment, south-west Iran

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