Testing Models of Cenozoic Exhumation in the Western Greater Caucasus

Vincent, Stephen J.; Somin, M. L.; Carter, Andrew; Vezzoli, Giovanni; Fox, Matthew; Vautravers, B. P. H.

doi:10.1029/2018tc005451

Cited by 59 publications

(108 citation statements)

References 117 publications

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“…During latest Miocene to Pliocene time, structural changes within the orogen intensified, coinciding with changes in foreland basin sediment routing. Thermochronometry data suggest that exhumation of the Greater Caucasus increased by a factor of 10, to ∼1 mm/yr, at 7-5 Ma (Avdeev & Niemi, 2011;Vincent et al, 2020), likely reflecting accretion of lower plate material as predicted by some models in the early stages of collision (Toussaint et al, 2004, Figure 11b). Pliocene to Quaternary time is reported as the period of major activity on retro-and pro-wedge fold and thrust structures that first developed in Late Miocene time (Banks et al, 1997;Sobornov, 1994, Figure 11b).…”

Section: Transition From Subduction To Collisionmentioning

confidence: 77%

“…By comparing source age signatures to detrital zircon ages in samples from three foreland basin sections distributed along strike, we investigate the dispersal of sediment from upland sources into the basin between the Greater and Lesser Caucasus from the Oligocene to Quaternary. We combine this zircon U-Pb age dataset with published stratigraphy for the three sampled sections and published thermochronometric (Avdeev & Niemi, 2011;Vincent et al, 2020), geodetic (Kadirov et al, 2012(Kadirov et al, , 2015Reilinger et al, 2006;Sokhadze et al, 2018) and structural (Banks, Robinson, & Williams, 1997;Cowgill et al, 2016;Forte, Cowgill, Murtuzayev, Kangarli, & Stoica, 2013;Sobornov, 1994) records to correlate sedimentary changes with the structural evolution of the orogen and explore implications for collision. We also discuss zircon age distributions of regional basement domains and implications for the distribution of sutures along the southern margin of Eurasia, which may have guided later localization of deformation.…”

Section: Introductionmentioning

confidence: 99%

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Sedimentary response to a collision orogeny recorded in detrital zircon provenance of Greater Caucasus foreland basin sediments

et al. 2020

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The Greater Caucasus orogen on the southern margin of Eurasia is hypothesized to be a young collisional system and may present an opportunity to probe the structural, sedimentary and geodynamic effects of continental collision. We present detrital zircon U-Pb age data from the Caucasus region that constrain changes in sediment routing and source exposure during the late Cenozoic convergence and collision between the Greater Caucasus orogen and the Lesser Caucasus, an arc terrane on the lower plate of the system. During Oligocene to Middle Miocene time, following the initiation of deformation within the Greater Caucasus, marine sandstones and shales were deposited between the Greater and Lesser Caucasus, and detrital zircon age data suggest no mixing of Greater Caucasus and Lesser Caucasus detritus. During Middle to Late Miocene time, Greater Caucasus detritus was deposited onto the Lesser Caucasus basin margin, and terrestrial, largely conglomeratic, sedimentation began between the Greater and Lesser Caucasus. Around 5.3 Ma, upper plate exhumation rates increased and shortening migrated to pro-and retro-wedge fold-thrust belts, coinciding with the initiation of foreland basin erosion. Sediment composition, provenance and structural data from the orogen together suggest the existence of a wide (230-280 km) marine basin that was progressively closed during Oligocene to Late Miocene time, probably by subduction/lithospheric underthrusting beneath the Greater Caucasus, followed by initiation of collision between the Lesser Caucasus arc terrane and the Greater Caucasus in Late Miocene to Pliocene time. The pace of the transition from hypothesized subduction to collision in the Caucasus is consistent with predictions from numerical modeling for a system with moderate convergence rates (<13 mm/yr) and hot lower plate continental lithosphere. Basement crystallization histories implied by our detrital zircon age data suggest the presence of two pre-Jurassic sutures between stable Eurasia and the Lesser Caucasus, which likely guided later deformation.

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Section: Transition From Subduction To Collisionmentioning

confidence: 77%

Section: Introductionmentioning

confidence: 99%

Sedimentary response to a collision orogeny recorded in detrital zircon provenance of Greater Caucasus foreland basin sediments

et al. 2020

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“…Final closure of the Caucasus Basin and collision between the Lesser and Greater Caucasus basements occurred in the Miocene‐Pliocene, causing accelerated exhumation and growth of the present‐day Greater Caucasus Mountains (Figure d; e.g., Mitchell & Westaway, ; Ershov et al, ; Mosar et al, ; Avdeev & Niemi, ; Cowgill et al, ; Vincent et al, ), although Oligocene growth of the range has also been argued for based on sedimentological data (Vincent et al, , ). Present‐day shortening appears to be dominantly concentrated in a south‐directed foreland fold‐thrust belt that deforms Mesozoic‐Cenozoic strata along the southern margin of the Greater Caucasus in the Rioni, Kartli, Alazani, and Kura basins, with north‐directed deformation on the north side of the range restricted to the central and eastern parts of the mountain belt (Figure b; e.g., Dotduyev, ; Banks et al, ; Mosar et al, ; Forte et al, , , ; Adamia et al, 2011; Trexler, ).…”

Section: Tectonic Settingmentioning

confidence: 99%

Evolution of the Greater Caucasus Basement and Formation of the Main Caucasus Thrust, Georgia

et al. 2020

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Along the northern margin of the Arabia-Eurasia collision zone in the western Greater Caucasus, the Main Caucasus Thrust (MCT) juxtaposes Paleozoic crystalline basement to the north against Mesozoic metasedimentary and volcaniclastic rocks to the south. The MCT is commonly assumed to be the trace of an active plate-boundary scale structure that accommodates Arabia-Eurasia convergence, but field data supporting this interpretation are equivocal. Here we investigate the deformation history of the rocks juxtaposed across the MCT in Georgia using field observations, microstructural analysis, U-Pb and 40 Ar/ 39 Ar geochronology, and 40 Ar/ 39 Ar and (U-Th)/He thermochronology. Zircon U-Pb analyses show that Greater Caucasus crystalline rocks formed in the Early Paleozoic on the margin of Gondwana. Low-pressure/temperature amphibolite-facies metamorphism of these metasedimentary rocks and associated plutonism likely took place during Carboniferous accretion onto the Laurussian margin, as indicated by igneous and metamorphic zircon U-Pb ages of~330-310 Ma. 40 Ar/ 39 Ar ages of~190-135 Ma from muscovite in a greenschist-facies shear zone indicate that the MCT likely developed during Mesozoic inversion and/or rifting of the Caucasus Basin. A Mesozoic 40 Ar/ 39 Ar biotite age with release spectra indicating partial resetting and Cenozoic (<40 Ma) apatite and zircon (U-Th)/He ages imply at least~5-8 km of Greater Caucasus basement exhumation since~10 Ma in response to Arabia-Eurasia collision. Cenozoic reactivation of the MCT may have accommodated a fraction of this exhumation. However, Cenozoic zircon (U-Th)/He ages in both the hanging wall and footwall of the MCT require partitioning a substantial component of this deformation onto structures to the south. Plain Language Summary Collisions between continents cause deformation of the Earth's crustand the uplift of large mountain ranges like the Himalayas. Large faults often form to accommodate this deformation and may help bring rocks once buried at great depths up to the surface of the Earth. The Greater Caucasus Mountains form the northernmost part of a zone of deformation due to the ongoing collision between the Arabian and Eurasian continents. The Main Caucasus Thrust (MCT) is a fault juxtaposing old igneous and metamorphic (crystalline) rocks against younger rocks that has often been assumed to be a major means of accommodating Arabia-Eurasia collision. This study examines the history of rocks along the MCT with a combination of field work, study of microscopic deformation in rocks, and dating of rock formation and cooling. The crystalline rocks were added to the margins of present-day Eurasia about 330-310 million years ago, and the MCT first formed about 190-135 million years ago. The MCT is likely at most one of many structures accommodating present-day Arabia-Eurasia collision.

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“…The study of Herman et al (2013), like any study, could be improved. With the insights of more than 6 years of additional work using the inversion method, we have learned much that could be applied to the global assessment (Ballato et al, 2015;Herman and Brandon, 2015;Fox et al, 2015Fox et al, , 2016Margirier et al, 2015;Yang et al, 2016;Bertrand et al, 2017;Jiao et al, 2017;Siravo et al, 2019;Vincent et al, 2019). However, the substantive changes that we would make would be to the way we handled the post-processing of the results.…”

Section: Summary Of Problems In the Study Of Herman Et Al (2013)mentioning

confidence: 99%

Bias and error in modelling thermochronometric data: resolving a potential increase in Plio-Pleistocene erosion rate

Willett¹,

Herman²,

Fox³

et al. 2020

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Abstract. Thermochronometry provides one of few methods to quantify rock exhumation rate and history, including potential changes in exhumation rate. Thermochronometric ages can resolve rates, accelerations, and complex histories by exploiting different closure temperatures and path lengths using data distributed in elevation. We investigate how the resolution of an exhumation history is determined by the distribution of ages and their closure temperatures through an error analysis of the exhumation history problem. We define the sources of error, defined in terms of resolution, model error and methodological bias in the inverse method used by Herman et al. (2013) which combines data with different closure temperatures and elevations. The error analysis provides a series of tests addressing the various types of bias, including addressing criticism that there is a tendency of thermochronometric data to produce a false inference of faster erosion rates towards the present day because of a spatial correlation bias (Schildgen et al., 2018). Tests based on synthetic data demonstrate that the inverse method used by Herman et al. (2013) has no methodological or model bias towards increasing erosion rates. We do find significant resolution errors with sparse data, but these errors are not systematic, tending rather to leave inferred erosion rates at or near a Bayesian prior. To explain the difference in conclusions between our analysis and that of Schildgen et al. (2018), we examine their paper and find that their model tests used an incorrect geotherm calculation, invalidating their models. We also found that Schildgen et al. (2018) applied a biased operator to the results of Herman et al. (2013) thereby distorting the original results producing a bias that was falsely attributed to the original inverse model. Our reanalysis and interpretation show that the original results of Herman et al. (2013) are correct and there is no evidence for a systematic bias.

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Testing Models of Cenozoic Exhumation in the Western Greater Caucasus

Cited by 59 publications

References 117 publications

Sedimentary response to a collision orogeny recorded in detrital zircon provenance of Greater Caucasus foreland basin sediments

Sedimentary response to a collision orogeny recorded in detrital zircon provenance of Greater Caucasus foreland basin sediments

Evolution of the Greater Caucasus Basement and Formation of the Main Caucasus Thrust, Georgia

Bias and error in modelling thermochronometric data: resolving a potential increase in Plio-Pleistocene erosion rate

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