Mesozoic-Cenozoic accretionary complexes of the Greater Caucasus

Khain, V. E.

doi:10.1134/s1028334x07030129

Cited by 11 publications

(11 citation statements)

References 3 publications

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“…On the south flank of the western Greater Caucasus, Early‐Middle Jurassic volcanic and volcaniclastic rocks are widespread within dominantly siliciclastic Caucasus Basin strata, whereas Cretaceous and Cenozoic strata are primarily siliciclastic and carbonate sedimentary rocks (Adamia, Alania, et al., 2011; Gudjabidze, 2003; McCann et al., 2010; Saintot et al., 2006; Vincent et al., 2016). In the central and eastern Greater Caucasus, Jurassic igneous rocks are more sparsely distributed (Lordkipanidze et al., 1989), though there are Cretaceous volcaniclastic rocks within the Vandam zone of the eastern Greater Caucasus (Khain, 2007; Kopp & Shcherba, 1985; Safarov, 2006). Jurassic volcanic rocks exposed on the southern flank have been interpreted by some authors as arc rocks (Hässig et al., 2020; Hess et al., 1995; Mengel et al., 1987), but most studies view them as resulting from extension within the Caucasus Basin (e.g., Cowgill et al., 2016; Lordkipanidze et al., 1989; McCann et al., 2010; Saintot et al., 2006; Vincent et al., 2016).…”

Section: Geochronology and Geochemistry Of The Caucasus Arc‐back‐arc Systemmentioning

confidence: 99%

A Preliminary Framework for Magmatism in Modern Continental Back‐Arc Basins and Its Application to the Triassic‐Jurassic Tectonic Evolution of the Caucasus

Vasey

Cowgill

Cooper

2021

Geochem Geophys Geosyst

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Extension within a continental back‐arc basin initiates within continental rather than oceanic lithosphere, and the geochemical characteristics of magmatic rocks within continental back‐arcs are poorly understood relative to their intraoceanic counterparts. Here, we compile published geochemical data from five exemplar modern continental back‐arc basins—the Okinawa Trough, Bransfield Strait, Tyrrhenian Sea, Patagonia plateau, and Aegean Sea/Western Anatolia—to establish a geochemical framework for continental back‐arc magmatism. This analysis shows that continental back‐arcs yield geochemical signatures more similar to arc magmatism than intraoceanic back‐arcs do. We apply this framework to published data for Triassic‐Jurassic magmatic rocks from the Caucasus arc system, which includes a relict continental back‐arc, the Caucasus Basin, that opened during the Jurassic and for which the causal mechanism of formation remains debated. Our analysis of 40Ar/39Ar and U‐Pb ages indicates Permian‐Triassic arc magmatism from ∼260 to 220 Ma due to subduction beneath the Greater Caucasus and Scythian Platform. Late Triassic (∼220–210 Ma) collision of the Iranian block with Laurasia likely induced trench retreat in the Caucasus region and led to migration of the Caucasus arc and opening of the Caucasus Basin. This activity was followed by Jurassic arc magmatism in the Lesser Caucasus from ∼180 to 140 Ma and back‐arc spreading in the Caucasus Basin from ∼180 to 160 Ma. Trace element and Sr‐Nd isotopic data for magmatic rocks indicate that Caucasus Basin magmatism is comparable to modern continental back‐arcs and that the source to the Lesser Caucasus arc became more enriched at ∼160 Ma, likely from the cessation of back‐arc spreading.

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Section: Geochronology and Geochemistry Of The Caucasus Arc‐back‐arc Systemmentioning

confidence: 99%

A Preliminary Framework for Magmatism in Modern Continental Back‐Arc Basins and Its Application to the Triassic‐Jurassic Tectonic Evolution of the Caucasus

Vasey

Cowgill

Cooper

2021

Geochem Geophys Geosyst

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“…East of 46°E, the orogen is again singly vergent and south directed [ Forte et al ., ] but lacks exposed basement [ Ali‐Zade et al ., ; Nalivkin , ]. From north to south, main units here are Jurassic to Cretaceous clastic and carbonate deposits [ Kopp , ] structurally juxtaposed across the north dipping Zangi thrust [ Khain , ] against similarly aged andesitic lavas and associated coarse‐grained volcaniclastic rocks [ Abdulleyev and Samedova , ] of the Vandam zone. The foreland fold‐thrust belt exposes upper Miocene (Sarmatian) to Pleistocene (Apsheronian) strata [ Forte et al ., , , ; Nalivkin , ].…”

Section: Tectonic Settingmentioning

confidence: 99%

“…This contrast in provenance reflects derivation from distinct sources on opposite sides of an intervening ocean basin that has since closed. These two sources are perhaps best exposed along the Girdiman Caj (River) in eastern Azerbaijan (approximately at location of sample SE‐GC in Figure a), where two sections of Albian‐Cenomanian strata are juxtaposed across the Zangi thrust [e.g., Khain , ]. To the north, the Cretaceous strata consist of deep‐marine fine‐grained carbonaceous sandstone and shale [ Kopp , ], while to the south, the same age strata comprise andesitic lavas and associated coarse‐grained volcaniclastic rocks [ Abdulleyev and Samedova , ].…”

Section: Introductionmentioning

confidence: 99%

Relict basin closure and crustal shortening budgets during continental collision: An example from Caucasus sediment provenance

et al. 2016

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Comparison of plate convergence with the timing and magnitude of upper crustal shortening in collisional orogens indicates both shortening deficits (200–1700 km) and significant (10–40%) plate deceleration during collision, the cause(s) for which remains debated. The Greater Caucasus Mountains, which result from postcollisional Cenozoic closure of a relict Mesozoic back‐arc basin on the northern margin of the Arabia‐Eurasia collision zone, help reconcile these debates. Here we use U‐Pb detrital zircon provenance data and the regional geology of the Caucasus to investigate the width of the now‐consumed Mesozoic back‐arc basin and its closure history. The provenance data record distinct southern and northern provenance domains that persisted until at least the Miocene. Maximum basin width was likely ~350–400 km. We propose that closure of the back‐arc basin initiated at ~35 Ma, coincident with initial (soft) Arabia‐Eurasia collision along the Bitlis‐Zagros suture, eventually leading to ~5 Ma (hard) collision between the Lesser Caucasus arc and the Scythian platform to form the Greater Caucasus Mountains. Final basin closure triggered deceleration of plate convergence and tectonic reorganization throughout the collision. Postcollisional subduction of such small (102–103 km wide) relict ocean basins can account for both shortening deficits and delays in plate deceleration by accommodating convergence via subduction/underthrusting, although such shortening is easily missed if it occurs along structures hidden within flysch/slate belts. Relict basin closure is likely typical in continental collisions in which the colliding margins are either irregularly shaped or rimmed by extensive back‐arc basins and fringing arcs, such as those in the modern South Pacific.

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“…Folded PNtb strata are truncated to the north by the north‐dipping Zangi thrust, which carries Lower to Upper Cretaceous strata in the hanging wall (Figures 3b and 7; Khain, 2007; Khain & Shardanov, 1960; Nalivkin, 1976). The Zangi thrust is marked by a >500 m thick package of chaotically folded red and blue mudstone with brecciated sandstone interlayers (K2mfb; Figure 7; Khain, 2007; Khain & Shardanov, 1960; Nalivkin, 1976). Overlying units include Lower Cretaceous black shale and thin‐bedded, turbiditic sandstone (K1tb), mid‐Cretaceous, thin‐bedded, blue sandstone and shale (K2ss2), Upper Cretaceous red and blue shale (K2m), and Upper Cretaceous, thin‐bedded, blue‐gray sandstone and shale (K2ss2; Figures 3b and 7; Khain & Shardanov, 1960; Nalivkin, 1976).…”

Section: Structural and Thermochronometric Results And Interpretationmentioning

confidence: 99%

Diverse Deformation Mechanisms and Lithologic Controls in an Active Orogenic Wedge: Structural Geology and Thermochronometry of the Eastern Greater Caucasus

Cowgill

et al. 2022

Tectonics

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Orogenic wedges are common at convergent plate margins and deform internally to maintain a self‐similar geometry during growth. New structural mapping and thermochronometry data illustrate that the eastern Greater Caucasus mountain range of western Asia undergoes deformation via distinct mechanisms that correspond with contrasting lithologies of two sedimentary rock packages within the orogen. The orogen interior comprises a package of Mesozoic thin‐bedded (<10 cm) sandstones and shales. These strata are deformed throughout by short‐wavelength (<1 km) folds that are not fault‐bend or fault‐propagation folds. In contrast, a coeval package of thick‐bedded (up to 5 m) volcaniclastic sandstone and carbonate, known as the Vandam Zone, has been accreted and is deformed via imbrication of coherent thrust sheets forming fault‐related folds of 5–10 km wavelength. Structural reconstructions and thermochronometric data indicate that the Vandam Zone package was accreted between ca. 13 and 3 Ma. Following Vandam Zone accretion, thermal modeling of thermochronometric data indicates rapid exhumation (∼0.3–1 mm/yr) in the wedge interior beginning between ca. 6 and 3 Ma, and a novel thermochronometric paleo‐rotation analysis suggests out‐of‐sequence folding of wedge‐interior strata after ca. 3 Ma. Field relationships suggest that the Vandam Zone underwent syn‐convergent extension following accretion. Together, the data record spatially and temporally variable deformation, dependent on both the mechanical properties of deforming lithologies and perturbations such as accretion of material from the down‐going to the overriding plate. The diverse modes of deformation are consistent with the maintenance of critical taper.

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Mesozoic-Cenozoic accretionary complexes of the Greater Caucasus

Cited by 11 publications

References 3 publications

A Preliminary Framework for Magmatism in Modern Continental Back‐Arc Basins and Its Application to the Triassic‐Jurassic Tectonic Evolution of the Caucasus

A Preliminary Framework for Magmatism in Modern Continental Back‐Arc Basins and Its Application to the Triassic‐Jurassic Tectonic Evolution of the Caucasus

Relict basin closure and crustal shortening budgets during continental collision: An example from Caucasus sediment provenance

Diverse Deformation Mechanisms and Lithologic Controls in an Active Orogenic Wedge: Structural Geology and Thermochronometry of the Eastern Greater Caucasus

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