Abstract The ophiolites of NE Anatolia and of the Lesser Caucasus (NALC) evidence an obduction ov... more Abstract The ophiolites of NE Anatolia and of the Lesser Caucasus (NALC) evidence an obduction over ∼200 km of oceanic lithosphere of Middle Jurassic age (c. 175–165 Ma) along an entire tectonic boundary (>1000 km) at around 90 Ma. The obduction process is characterized by four first order geological constraints: (1) Ophiolites represent remnants of a single ophiolite nappe currently of only a few kilometres thick and 200 km long. The oceanic crust was old (∼80 Ma) at the time of its obduction. (2) The presence of OIB-type magmatism emplaced up to 10 Ma prior to obduction preserved on top of the ophiolites is indicative of mantle upwelling processes (hotspot). (3) The leading edge of the Taurides-Anatolides, represented by the South Armenian Block, did not experience pressures exceeding 0.8 GPa nor temperatures greater than ∼300 °C during underthrusting below the obducting oceanic lithosphere. (4) An oceanic domain of a maximum 1000 km (from north to south) remained between Taurides-Anatolides and Pontides-Southern Eurasian Margin after the obduction. We employ two-dimensional thermo-mechanical numerical modelling in order to investigate obduction dynamics of a re-heated oceanic lithosphere. Our results suggest that thermal rejuvenation (i.e. reheating) of the oceanic domain, tectonic compression, and the structure of the passive margin are essential ingredients for enabling obduction. Afterwards, extension induced by far-field plate kinematics (subduction below Southern Eurasian Margin), facilitates the thinning of the ophiolite, the transport of the ophiolite on the continental domain, and the exhumation of continental basement through the ophiolite. The combined action of thermal rejuvenation and compression are ascribed to a major change in tectonic motions occurring at 110–90 Ma, which led to simultaneous obductions in the Oman (Arabia) and NALC regions.
The reason for obduction, or tectonic transport of oceanic lithosphere onto continents, is invest... more The reason for obduction, or tectonic transport of oceanic lithosphere onto continents, is investigated by two‐dimensional thermo‐mechanical numerical modelling based on the geology of the Anatolia–Lesser Caucasus ophiolites. Heating of the oceanic domain and extension induced by far‐field plate kinematics appear to be essential for the obduction of ~80‐Ma‐old oceanic crust over distances exceeding 200 km. Heating of the oceanic lithosphere by mantle upwelling is evidenced by a thick alkaline volcanic series emplaced on top of the oceanic crust 10–20 Ma before obduction, at the onset of Africa–Eurasia convergence. Regional heating reduced the negative buoyancy and strength of the magmatically old lithosphere. Extension facilitated the propagation of obduction by reducing the mantle lithosphere thickness, which led to the exhumation of eclogite‐free continental crust previously underthrusted beneath the ophiolites. This extensional event is ascribed to far‐field plate kinematics resu...
Analysis of minors faults in the Colorado Plateau and determination of the displacement sense of ... more Analysis of minors faults in the Colorado Plateau and determination of the displacement sense of structures in southeastern Arizona lead to distinguishing two different directions of compression in the western United States ranging in age from Middle Cretaceous to Upper Eocene. New structural data indicate a first Upper Cretaceous event with a N065˚E direction of shortening, then a second one trending N115˚E, Paleogene in age. The Colorado Plateau was reactivated by brittle deformation even though its southern boundary was affected by tangential, then transcurrent deformations, remobilizing prior crustal structures
In the tectonic evolution of the Black Sea (BS) there are several unsolved questions: 1) the timi... more In the tectonic evolution of the Black Sea (BS) there are several unsolved questions: 1) the timing of the BS opening and 2) the timing of the Cenozoic shortening of the northern margin of the Eastern BS (EBS) basin. Mainly, the age-frame of the main compressional deformations is assumed as Oligo-Miocene, related to the Greater Caucasus (GC) basin inversion. The Crimean Mountains (CM) is one of the key areas to fix the tectonic evolution of the BS therefore, we focus on an integrated onshore/offshore transect from the Eastern CM to the Sorokin trough (north of EBS). We used newly collected stratigraphic and structural data from the Eastern CM, and a new interpretation of multichannel seismic lines. We define 1) the seismic stratigraphy and constrain the relative chronology of deformations, 2) the age of seismic units by correlation of the seismic data with the Subbotina-403 well log, and 3) we construct an on-and-off shore transect of the Eastern CM - North of the EBS region. Our re...
Bulletin of the Geological Society of Greece, 2018
Micropalaeontological age evidence for the sedimentary cover of ophiolites is important to unders... more Micropalaeontological age evidence for the sedimentary cover of ophiolites is important to understand the palaeogeographic and geodynamic evolution of Tethyan realms. The Stepanavan ophiolitic suite of Northern Armenia consists of peridotites, gabbros, plagiogranite and lavas with a radiolarite sedimentary cover. It is regarded as the northern extension of the Sevan Akera ophiolitic zone and may be considered as the eastern extension of the Izmir-Ankara suture zone. It represents the relics of a slow-spreading mid oceanic ridge that was active between Eurasia and the South-Armenian Block of Gondwanian origin. Radiolaria extracted from radiolarites of the Stepanavan ophiolite provide for the first time a Late Jurassic (late Kimmeridgian to early Tithonian) age constraint for this part of Tethyan oceanic crust preserved in Lesser Caucasus.
... On the geological features of Transcaucasian ophiolitic zones. Izvestia Acad. Sci. Armen-ian ... more ... On the geological features of Transcaucasian ophiolitic zones. Izvestia Acad. Sci. Armen-ian SSR, Nauki o Zemle, 4-5: 13-26 (in Russian). Avagyan A., Sosson M., Philip H., Karakhanian A., Rolland YA, Melkonyan R., Rebai S. and Davtyan V., 2005. ...
The Tethyan geology of the Lesser Caucasus has a multiphase and complex history. The main lithote... more The Tethyan geology of the Lesser Caucasus has a multiphase and complex history. The main lithotectonic domains that can be individualized during the presence of a Tethyan oceanic branch in the region are (i) the South Armenian Block (SAB), a Gondwanian remain that is mainly known by its characteristic Middle to Upper Palaeozoic sedimentary sequences; (ii) ophiolitic units, including their sedimentary cover, which record a complex history of geodynamic, magmatic and sedimentary events, and (iii) the Eurasian active margin, known essentially from its Middle Jurassic – Upper Cretaceous volcano-sedimentary sequences. Following the obduction of ophiolites onto the SAB during the Coniacian-Santonian interval and the subsequent Palaeocene-Lower Eocene collision of the South Armenian Block against Eurasia, widespread volcanic activity took place during the middle to late Eocene. Impressive quaternary volcanoes and recent tectonic activity along active faults attest on the geodynamic activity in relation to the collision with the Arabian plate.
Geological Society, London, Special Publications, 2010
In the Lesser Caucasus three main domains are distinguished from SW to NE: (1) the autochthonous ... more In the Lesser Caucasus three main domains are distinguished from SW to NE: (1) the autochthonous South Armenian Block (SAB), a Gondwana-derived terrane; (2) the ophiolitic Sevan–Akera suture zone; and (3) the Eurasian plate. Based on our field work, new stratigraphical, petrological, geochemical and geochronological data combined with previous data we present new insights on the subduction, obduction and collision processes recorded in the Lesser Caucasus. Two subductions are clearly identified, one related to the Neotethys subduction beneath the Eurasian margin and one intra-oceanic (SSZ) responsible for the opening of a back-arc basin which corresponds to the ophiolites of the Lesser Caucasus. The obduction occurred during the Late Coniacian to Santonian and is responsible for the widespread ophiolitic nappe outcrop in front of the suture zone. Following the subduction of oceanic lithosphere remnants under Eurasia, the collision of the SAB with Eurasia started during the Paleocene...
... Version française abrégée. Introduction. Dans le Petit Caucase, les ophiolites de Stepanavan ... more ... Version française abrégée. Introduction. Dans le Petit Caucase, les ophiolites de Stepanavan (Fig. 1) appartiennent à la zone de suture entre la marge eurasienne et lebloc sud-arménien, d'origine gondwanienne [5], [9], [16], [17], [18] and [20]. ...
This paper investigates the structure of the northern margin of the Ararat depression in a study ... more This paper investigates the structure of the northern margin of the Ararat depression in a study area in SE Armenia. The depression is a Cenozoic intermontane basin located to the south of the Lesser Caucasus. The purpose is to improve understanding of the basin's structure and origin within a regional tectonic framework which has been dominated since the Late Cretaceous by the closure of Neotethys and the Arabia‐Eurasia collision. We suggest that the depression is not a graben controlled by normal faults; rather, based on detailed observations, structures in the study area are interpreted as oblique‐slip reverse and thrust faults activated in post Oligocene‐Miocene times. These compressional faults resulted in the formation of asymmetric fold structures including the Lanjanist and Urts anticlines which are well expressed in the surface relief to the north of the Ararat depression. In general the structural pattern is complicated by secondary normal faults which resulted in superimposed gravitational slope processes and erosion. Major structures in the study area originated in a compressional setting associated with the closure of Neotethys since the latest Cretaceous. Post‐collisional strike‐slip faulting was linked to convergence of the Arabian and Eurasian plate margins. Pliocene and Quaternary structures, some still active, show evidence of structural inheritance. The Armenian portion of the Ararat depression contains obduction‐related nappes, anticlines and thrust faults which have potential as structural traps for hydrocarbons. These should be investigated in detail using advanced geophysical methods including 2D and 3D seismic analyses.
Geological Society, London, Special Publications, 2015
Abstract The Eastern Pontides–Lesser Caucasus fold–thrust belt displays a peculiar northwards arc... more Abstract The Eastern Pontides–Lesser Caucasus fold–thrust belt displays a peculiar northwards arc-shaped geometry that was defined as an orocline in earlier studies. The Lesser Caucasus was affected by two main tectonic events that could have caused orocline formation: (1) Paleocene–Eocene collision of the South Armenian Block with Eurasia; and (2) Oligocene–Miocene Arabia–Eurasia collision. We tested the hypothesis that the Lesser Caucasus is an orocline and aimed to time the formation of this orocline. To determine the vertical axis rotations, 37 sites were sampled for palaeomagnetism in rocks of Upper Cretaceous–Miocene age in Georgia and Armenia. In addition, we compiled a review of c. 100 available datasets. A strike test was applied to the remaining datasets, which were divided into four chronological sub-sets, leading us to conclude that the Eastern Pontides–Lesser Caucasus fold–thrust belt forms a progressive orocline. We concluded that: (1) some pre-existing curvature must have been present before the Late Cretaceous; (2) the orocline acquired part of its curvature after the Paleocene and before the Middle Eocene as a result of South Armenian Block–Eurasia collision; and (3) about 50% of the curvature formed after the Eocene and probably before the Late Miocene, probably as a result of Arabia–Eurasia collision. Supplementary material: Results from rock magnetic experiments, reversal and fold tests and equal area projections of the characteristic remanent magnetizations for each site, as well as biostratigraphic ages and a table with palaeomagnetic results from the literature review (with assigned numbers referred to in the text) are available at http://www.geolsoc.org.uk/SUP18852.
Abstract The ophiolites of NE Anatolia and of the Lesser Caucasus (NALC) evidence an obduction ov... more Abstract The ophiolites of NE Anatolia and of the Lesser Caucasus (NALC) evidence an obduction over ∼200 km of oceanic lithosphere of Middle Jurassic age (c. 175–165 Ma) along an entire tectonic boundary (>1000 km) at around 90 Ma. The obduction process is characterized by four first order geological constraints: (1) Ophiolites represent remnants of a single ophiolite nappe currently of only a few kilometres thick and 200 km long. The oceanic crust was old (∼80 Ma) at the time of its obduction. (2) The presence of OIB-type magmatism emplaced up to 10 Ma prior to obduction preserved on top of the ophiolites is indicative of mantle upwelling processes (hotspot). (3) The leading edge of the Taurides-Anatolides, represented by the South Armenian Block, did not experience pressures exceeding 0.8 GPa nor temperatures greater than ∼300 °C during underthrusting below the obducting oceanic lithosphere. (4) An oceanic domain of a maximum 1000 km (from north to south) remained between Taurides-Anatolides and Pontides-Southern Eurasian Margin after the obduction. We employ two-dimensional thermo-mechanical numerical modelling in order to investigate obduction dynamics of a re-heated oceanic lithosphere. Our results suggest that thermal rejuvenation (i.e. reheating) of the oceanic domain, tectonic compression, and the structure of the passive margin are essential ingredients for enabling obduction. Afterwards, extension induced by far-field plate kinematics (subduction below Southern Eurasian Margin), facilitates the thinning of the ophiolite, the transport of the ophiolite on the continental domain, and the exhumation of continental basement through the ophiolite. The combined action of thermal rejuvenation and compression are ascribed to a major change in tectonic motions occurring at 110–90 Ma, which led to simultaneous obductions in the Oman (Arabia) and NALC regions.
The reason for obduction, or tectonic transport of oceanic lithosphere onto continents, is invest... more The reason for obduction, or tectonic transport of oceanic lithosphere onto continents, is investigated by two‐dimensional thermo‐mechanical numerical modelling based on the geology of the Anatolia–Lesser Caucasus ophiolites. Heating of the oceanic domain and extension induced by far‐field plate kinematics appear to be essential for the obduction of ~80‐Ma‐old oceanic crust over distances exceeding 200 km. Heating of the oceanic lithosphere by mantle upwelling is evidenced by a thick alkaline volcanic series emplaced on top of the oceanic crust 10–20 Ma before obduction, at the onset of Africa–Eurasia convergence. Regional heating reduced the negative buoyancy and strength of the magmatically old lithosphere. Extension facilitated the propagation of obduction by reducing the mantle lithosphere thickness, which led to the exhumation of eclogite‐free continental crust previously underthrusted beneath the ophiolites. This extensional event is ascribed to far‐field plate kinematics resu...
Analysis of minors faults in the Colorado Plateau and determination of the displacement sense of ... more Analysis of minors faults in the Colorado Plateau and determination of the displacement sense of structures in southeastern Arizona lead to distinguishing two different directions of compression in the western United States ranging in age from Middle Cretaceous to Upper Eocene. New structural data indicate a first Upper Cretaceous event with a N065˚E direction of shortening, then a second one trending N115˚E, Paleogene in age. The Colorado Plateau was reactivated by brittle deformation even though its southern boundary was affected by tangential, then transcurrent deformations, remobilizing prior crustal structures
In the tectonic evolution of the Black Sea (BS) there are several unsolved questions: 1) the timi... more In the tectonic evolution of the Black Sea (BS) there are several unsolved questions: 1) the timing of the BS opening and 2) the timing of the Cenozoic shortening of the northern margin of the Eastern BS (EBS) basin. Mainly, the age-frame of the main compressional deformations is assumed as Oligo-Miocene, related to the Greater Caucasus (GC) basin inversion. The Crimean Mountains (CM) is one of the key areas to fix the tectonic evolution of the BS therefore, we focus on an integrated onshore/offshore transect from the Eastern CM to the Sorokin trough (north of EBS). We used newly collected stratigraphic and structural data from the Eastern CM, and a new interpretation of multichannel seismic lines. We define 1) the seismic stratigraphy and constrain the relative chronology of deformations, 2) the age of seismic units by correlation of the seismic data with the Subbotina-403 well log, and 3) we construct an on-and-off shore transect of the Eastern CM - North of the EBS region. Our re...
Bulletin of the Geological Society of Greece, 2018
Micropalaeontological age evidence for the sedimentary cover of ophiolites is important to unders... more Micropalaeontological age evidence for the sedimentary cover of ophiolites is important to understand the palaeogeographic and geodynamic evolution of Tethyan realms. The Stepanavan ophiolitic suite of Northern Armenia consists of peridotites, gabbros, plagiogranite and lavas with a radiolarite sedimentary cover. It is regarded as the northern extension of the Sevan Akera ophiolitic zone and may be considered as the eastern extension of the Izmir-Ankara suture zone. It represents the relics of a slow-spreading mid oceanic ridge that was active between Eurasia and the South-Armenian Block of Gondwanian origin. Radiolaria extracted from radiolarites of the Stepanavan ophiolite provide for the first time a Late Jurassic (late Kimmeridgian to early Tithonian) age constraint for this part of Tethyan oceanic crust preserved in Lesser Caucasus.
... On the geological features of Transcaucasian ophiolitic zones. Izvestia Acad. Sci. Armen-ian ... more ... On the geological features of Transcaucasian ophiolitic zones. Izvestia Acad. Sci. Armen-ian SSR, Nauki o Zemle, 4-5: 13-26 (in Russian). Avagyan A., Sosson M., Philip H., Karakhanian A., Rolland YA, Melkonyan R., Rebai S. and Davtyan V., 2005. ...
The Tethyan geology of the Lesser Caucasus has a multiphase and complex history. The main lithote... more The Tethyan geology of the Lesser Caucasus has a multiphase and complex history. The main lithotectonic domains that can be individualized during the presence of a Tethyan oceanic branch in the region are (i) the South Armenian Block (SAB), a Gondwanian remain that is mainly known by its characteristic Middle to Upper Palaeozoic sedimentary sequences; (ii) ophiolitic units, including their sedimentary cover, which record a complex history of geodynamic, magmatic and sedimentary events, and (iii) the Eurasian active margin, known essentially from its Middle Jurassic – Upper Cretaceous volcano-sedimentary sequences. Following the obduction of ophiolites onto the SAB during the Coniacian-Santonian interval and the subsequent Palaeocene-Lower Eocene collision of the South Armenian Block against Eurasia, widespread volcanic activity took place during the middle to late Eocene. Impressive quaternary volcanoes and recent tectonic activity along active faults attest on the geodynamic activity in relation to the collision with the Arabian plate.
Geological Society, London, Special Publications, 2010
In the Lesser Caucasus three main domains are distinguished from SW to NE: (1) the autochthonous ... more In the Lesser Caucasus three main domains are distinguished from SW to NE: (1) the autochthonous South Armenian Block (SAB), a Gondwana-derived terrane; (2) the ophiolitic Sevan–Akera suture zone; and (3) the Eurasian plate. Based on our field work, new stratigraphical, petrological, geochemical and geochronological data combined with previous data we present new insights on the subduction, obduction and collision processes recorded in the Lesser Caucasus. Two subductions are clearly identified, one related to the Neotethys subduction beneath the Eurasian margin and one intra-oceanic (SSZ) responsible for the opening of a back-arc basin which corresponds to the ophiolites of the Lesser Caucasus. The obduction occurred during the Late Coniacian to Santonian and is responsible for the widespread ophiolitic nappe outcrop in front of the suture zone. Following the subduction of oceanic lithosphere remnants under Eurasia, the collision of the SAB with Eurasia started during the Paleocene...
... Version française abrégée. Introduction. Dans le Petit Caucase, les ophiolites de Stepanavan ... more ... Version française abrégée. Introduction. Dans le Petit Caucase, les ophiolites de Stepanavan (Fig. 1) appartiennent à la zone de suture entre la marge eurasienne et lebloc sud-arménien, d'origine gondwanienne [5], [9], [16], [17], [18] and [20]. ...
This paper investigates the structure of the northern margin of the Ararat depression in a study ... more This paper investigates the structure of the northern margin of the Ararat depression in a study area in SE Armenia. The depression is a Cenozoic intermontane basin located to the south of the Lesser Caucasus. The purpose is to improve understanding of the basin's structure and origin within a regional tectonic framework which has been dominated since the Late Cretaceous by the closure of Neotethys and the Arabia‐Eurasia collision. We suggest that the depression is not a graben controlled by normal faults; rather, based on detailed observations, structures in the study area are interpreted as oblique‐slip reverse and thrust faults activated in post Oligocene‐Miocene times. These compressional faults resulted in the formation of asymmetric fold structures including the Lanjanist and Urts anticlines which are well expressed in the surface relief to the north of the Ararat depression. In general the structural pattern is complicated by secondary normal faults which resulted in superimposed gravitational slope processes and erosion. Major structures in the study area originated in a compressional setting associated with the closure of Neotethys since the latest Cretaceous. Post‐collisional strike‐slip faulting was linked to convergence of the Arabian and Eurasian plate margins. Pliocene and Quaternary structures, some still active, show evidence of structural inheritance. The Armenian portion of the Ararat depression contains obduction‐related nappes, anticlines and thrust faults which have potential as structural traps for hydrocarbons. These should be investigated in detail using advanced geophysical methods including 2D and 3D seismic analyses.
Geological Society, London, Special Publications, 2015
Abstract The Eastern Pontides–Lesser Caucasus fold–thrust belt displays a peculiar northwards arc... more Abstract The Eastern Pontides–Lesser Caucasus fold–thrust belt displays a peculiar northwards arc-shaped geometry that was defined as an orocline in earlier studies. The Lesser Caucasus was affected by two main tectonic events that could have caused orocline formation: (1) Paleocene–Eocene collision of the South Armenian Block with Eurasia; and (2) Oligocene–Miocene Arabia–Eurasia collision. We tested the hypothesis that the Lesser Caucasus is an orocline and aimed to time the formation of this orocline. To determine the vertical axis rotations, 37 sites were sampled for palaeomagnetism in rocks of Upper Cretaceous–Miocene age in Georgia and Armenia. In addition, we compiled a review of c. 100 available datasets. A strike test was applied to the remaining datasets, which were divided into four chronological sub-sets, leading us to conclude that the Eastern Pontides–Lesser Caucasus fold–thrust belt forms a progressive orocline. We concluded that: (1) some pre-existing curvature must have been present before the Late Cretaceous; (2) the orocline acquired part of its curvature after the Paleocene and before the Middle Eocene as a result of South Armenian Block–Eurasia collision; and (3) about 50% of the curvature formed after the Eocene and probably before the Late Miocene, probably as a result of Arabia–Eurasia collision. Supplementary material: Results from rock magnetic experiments, reversal and fold tests and equal area projections of the characteristic remanent magnetizations for each site, as well as biostratigraphic ages and a table with palaeomagnetic results from the literature review (with assigned numbers referred to in the text) are available at http://www.geolsoc.org.uk/SUP18852.
Uploads
Papers by m sosson