Late Palaeozoic and Mesozoic evolution of the Amu Darya Basin (Turkmenistan, Uzbekistan)

Abstract

The Amu Darya Basin (ADB) has been studied primarily for its important hydrocarbon reserves and to a lesser extent for its geodynamic evolution. The ADB is located on the SE portion of the Turan Platform, between the sutures of the Turkestan and Palaeo-Tethys oceans, which closed during the Late Palaeozoic and Early Mesozoic, respectively. Blocks and island arcs accreted to Eurasia during the Palaeozoic form a poorly defined, heterogeneous basement underlying the ADB. They played an important role in shaping its composite structure into variously orientated sub-basins and highs. In this paper, depth–structure and isopach maps, and regional cross-sections, are analysed to unravel the location and origin of the main structural elements and to characterize the subsidence evolution of the ADB. The main tectonic events leading to the formation and evolution of the ADB took place: (1) in the Late Palaeozoic–Early Triassic (back-arc, rollback and extension/strike-slip); (2) from the Middle Triassic to the Triassic–Jurassic boundary (Eo-Cimmerian collision of Gondwana-derived continental blocks with Eurasia); and (3) during the Early–Middle Jurassic (post-collision extensional event). The last part of this evolution reflects shortening and flexure due to Cenozoic collisions to the south. Palaeotectonic maps are used to relate these events to the geodynamics of the Tethyan domain.

Facies analyses and depositional setting of the Lower Cretaceous Shurijeh–Shatlyk formations in the Kopeh Dagh–Amu Darya Basin (Iran and Turkmenistan)

“…Subsidence in the KDADB began along ENE–WSW longitudinal faults during the Middle Jurassic (Afshar‐Harb, ; Brunet et al, ). Synrift sediments rest with an angular unconformity on Devonian to Triassic sedimentary and arc, back‐arc volcanic rocks, which are exposed in the Aghdarband erosional window (eastern Kopeh Dagh Foldbelt), as well as north of Afghanistan (Brookfield & Hashmat, ; Ruttner, , ; Zanchetta et al, ).…”

“…Relatively continuous deposition of sedimentary rocks in the KDADB began during Middle Jurassic rifting near the Pamir region (Figure a), in the east to the Caspian Basin to the west of the study area and continued through to Miocene time (Klett et al, ; Moussavi‐Harami & Brenner, ; Ulmishek, ). However, there are several hiatuses within the Cretaceous–Palaeocene succession in the south‐western part of the basin (Figure , and see Brunet et al, ; Robert et al, ). Based on depth‐structural and isopach maps (Brunet et al, ), depocentres in the KDADB are mostly oriented WNW–ESE.…”

“…However, there are several hiatuses within the Cretaceous–Palaeocene succession in the south‐western part of the basin (Figure , and see Brunet et al, ; Robert et al, ). Based on depth‐structural and isopach maps (Brunet et al, ), depocentres in the KDADB are mostly oriented WNW–ESE. Compression occurred during the Alpine Orogeny and closure of the Neotethys Ocean during Neogene–Quaternary time (Robert et al, ).…”

“…This basin hosts several giant and small gas fields such as Galkynysh (the largest gas field in the basin), Dauletabad, Shaltyk, Khangiran, and Gonbadli (Figure a: Afshar‐Harb, ; Kavoosi, Lasemi, Sherkati, & Mossavi‐Harami, ; Klett et al, ; Moussavi‐Harami & Brenner, ; Ulmishek, ). The KDADB formed after closure of the Palaeotethys Ocean between Eurasia and Gondwana during the Cimmerian Orogeny (Brunet et al, ; Garzanti & Gaetani, ). The Palaeotethys suture zone forms the southern basin boundary (Brunet et al, ; Robert et al, ; Sheikholeslami & Kouhpeyma, ; Stocklin, ; Wilmsen, Fürsich, Emami, Majidifard, & Taheri, ) which is exposed in north‐east Iran and north Afghanistan (Figure b).…”

“…The KDADB formed after closure of the Palaeotethys Ocean between Eurasia and Gondwana during the Cimmerian Orogeny (Brunet et al, ; Garzanti & Gaetani, ). The Palaeotethys suture zone forms the southern basin boundary (Brunet et al, ; Robert et al, ; Sheikholeslami & Kouhpeyma, ; Stocklin, ; Wilmsen, Fürsich, Emami, Majidifard, & Taheri, ) which is exposed in north‐east Iran and north Afghanistan (Figure b).…”