Abstract Two new and relatively well-preserved radiolarian faunas were extracted from blocks included in the Cretaceous ophiolitic mélange unit that crops out in the Erakh area south of Yerevan, Armenia. One of these radiolarian assemblages was extracted from cherts that are in stratigraphic contact with variolitic lavas. This radiolarian assemblage suggests a late Aalenian to middle Bajocian age (Unitary Association Zones 2–3) based on the co-occurrence of the species Parasaturnalis diplocyclis (Yao) and Transhsuum hisuikyoense (Isozaki & Matsuda). A second radiolarian assemblage was obtained from a block, several metres thick, of alternating pelagic limestones and cherts. It was characterized by the co-occurrence of the species Hemicryptocapsa capita Tan and Dicerosaturnalis dicranacanthos (Squinabol). The presence of these two species within the same assemblage correlates with Unitary Association Zone 17 and these samples are therefore assigned to the late Valanginian. These results suggest that submarine volcanic activity took place during the late Aalenian–middle Bajocian interval and that mixed carbonate and siliceous ooze accumulated during the late Valanginian. Previous biochronological data on Radiolaria from the Erakh mélange and the Vedi ophiolite are reviewed and their implications for the geodynamic and palaeoenvironmental evolution of the Tethyan ocean in Armenia are discussed.

Abstract Over the past 15 years, significant progress has been achieved in our understanding of Lower Palaeozoic radiolarian faunas. However, description of biogeographical patterns of Ordovician Radiolaria is hampered by the paucity of known occurrences as well as possible taphonomic influences. The distribution of all known assemblages is analysed in time and space. Lower Ordovician (especially Tremadocian) Radiolaria are known from two distinct tropical localities of Laurentia. Geographical coverage is much better for the Middle Ordovician (Darriwilian). However, data are concentrated in tropical palaeolatitudes (between 30°N and 30°S). The absence of data from mid/high-latitude localities limits any biogeographical insights. In addition to this there are taphonomic and taxonomic biases. Data are also sparse for the Upper Ordovician. However, comparison between Australian and Nevadan material of Katian age shows strong similarities, suggesting the presence of a coherent tropical radiolarian bioprovince, as in the modern ocean.

Abstract 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, producing 1) folding of ophiolites, arc and Upper Cretaceous formations (Transcaucasus massif to Karabakh); 2) thrusting toward SW; and 3) a foreland basin in front of the belt. Upper–Middle Eocene series unconformably cover the three domains. From Eocene to Miocene as a result of the Arabian plate collision with the SAB to the South, southward propagation of shortening featured by folding and thrusting occurred all along the belt. These deformations are sealed by a thick sequence of unconformable Miocene to Quaternary clastic and volcanic rocks of debated origin.

Abstract In order to improve our understanding of the palaeogeographic and geodynamic evolution of the Tethyan realms preserved in the Lesser Caucasus we here review the existing data for the sedimentary cover of ophiolites preserved in Armenia. Particular attention is given to those dated sedimentary rocks that are in direct genetic contact with ophiolitic lavas, as they provide constraints for submarine oceanic activity. The oldest available ages come from the Sevan–Akera suture zone that point to a Late Triassic oceanization. Data from both the Sevan and Vedi ophiolites provide evidence for Middle Jurassic (Bajocian) submarine activity, that continued until at least the Late Jurassic (Mid/Late Oxfordian to Late Kimmeridgian/Early Tithonian), as dated recently in Stepanavan and in this study for the Vedi ophiolite.

Abstract New radiolarian ages for blocks of radiolarian cherts associated with other blocks of distal pelagic facies and ophiolitic lithologies within the Lycian Mélange, SW Turkey, indicate deposition during Mid-Jurassic to Early Cretaceous time. Radiolarites overlying pink pelagic limestones of an allochthonous carbonate unit accumulated during the Mid- to Late Jurassic. On the basis of structural evidence the Lycian Mélange is inferred to have been rooted within the Northern Neotethys, to the north of the Tauride–Anatolide microcontinent. The Lycian radiolarites can be compared with other dated radiolarites from the Izmir–Ankara suture, the root zone of the Northern Neotethyan ocean. Based on all the available radiolarian data it is inferred that radiolarites accumulated within the Northern Neotethys in western Turkey from Late Triassic (Mid-Carnian to Late Norian) to Mid-Cretaceous (Cenomanian) time. The radiolarites were later detached from their inferred oceanic basement and accreted within a subduction complex during the Late Cretaceous (Turonian–Maastrichtian) and emplaced over the northern margin of the Tauride–Anatolide continent together with slices of continental margin and ophiolitic lithologies.