Gilbert Kelling

Neogene tectonics and plate convergence in the eastern Mediterranean: New data from southern Turkey

Data reported here demonstrate that the Misis Complex of southern Turkey comprises a major olistostromic body, formed prior to the early Miocene and tectonically emplaced upon a structurally imbricated pile of deep and shallow marine sediments of early Miocene to Pliocene age. Magmatic rocks forming olistoliths in the Misis Complex have a back-arc geochemical signature, and variations in the facies, paleoenvironments, and paleotransport vectors within the associated sediments provide a record of Miocene collisional events in southeast Turkey. The pseudo-accretionary imbrication and structural style of the Misis Complex are attributed to continued collisional over-thrusting, but there is evidence within the imbricated stack of late sinistral strike-slip faulting that relates to post-Miocene inception of motion along the East Anatolian fault system. The new data favor these geodynamic models proposed for the Neogene evolution of the northeastern Mediterranean that involve oblique convergence and associated strike-slip adjustments.

Geochemistry and tectonic environment of basaltic rocks from the Misis ophiolitic mélange, south Turkey

Abstract The Miocene Misis tectonosedimentary melange was formed during the closing stages of the Neotethys in what is now the Adana basin of southern Turkey. A major part is characterized by large disorientated limestone blocks set in a predominantly volcanogenic matrix of bedded and chaotic units comprising basaltic pillow lavas, associated hyaloclastites, serpentinites and various acidic tuffs. All the basaltic rocks are mildly metamorphosed (zeolite facies), variably vesicular and differentially altered to smectite, chlorite, Fe-oxides, zeolites and carbonate. Petrographic and chemical data on the least altered pillow lavas indicate they were originally sparsely olivine-plagioclase-clinopyroxene-phyric tholeiites and minor amphibole-phyric basaltic andesites. The basaltic clasts in the melange matrix are genetically related to the pillow lava sequences, with the observed variation throughout the suite being governed by low-pressure fractional crystallization. As a group, the basalts are characterized by low Zr/Y (2–4), relatively high Th/Yb (0.5–0.7) and La/Nb (1.5–2.5) ratios, and moderate, chondrite-normalized, light REE enrichment [ ( La Yb ) N = 3 ] patterns. The basalts have a mildly enriched, subduction-related chemistry and were possibly formed initially in a back-arc basin setting. The supra-subduction zone characteristics of the Misis basaltic units are similar to other Tethyan basalts in eastern Mediterranean ophiolites.

Black Sea-Marmara Sea Quaternary connections: new data from the Bosphorus, Istanbul, Turkey

Abstract Previous studies concluded that the Bosphorus Strait was formed during the Quaternary by fluvial incision of a valley between the Black Sea, to the north, and the Marmara Sea in the south. Hitherto, however, few details of the evolution of this connection have been elucidated from the sediments deposited within the Bosphorus itself. We report here details of sedimentological and palaeontological evidence relating to this history, obtained from five boreholes drilled into the unconsolidated sediment fill in the north-central sector of the Bosphorus, together with nearby geophysical profiles. The Quaternary fill of this part of the Bosphorus comprises two major facies associations. Yellow arkosic sands dominate the lower Facies Association A: these are assigned a Middle to Late Pleistocene age and the contained faunas have a lagoonal to lacustrine character and a Black Sea provenance (Paratethyan affinities). The abruptly succeeding units of Facies Association B comprise fining and coarsening upwards units of coarse to fine shelly and clayey sands that alternate with shell-bearing green clays. These sediments were formed in a range of marine and coastal settings and biostratigraphic evidence and absolute dating demonstrate the Mid–Late Holocene age of this upper unit. Initially brackish faunal assemblages in this upper unit show an upward increase in marine and Mediterranean affinities. Integrating these new data with previously published observations from coeval deposits in the southern Bosphorus and Izmit Bay (NE Marmara Sea) we conclude that during the Late Pleistocene and Early Holocene a topographic barrier existed in the south-central sector of the Bosphorus, on both sides of which estuarine and lagoonal sediments accumulated, with distinctive Black Sea and Mediterranean faunas. During a significant rise in sea level, between 7000 and 5300 years ago, this barrier was finally submerged, permitting interchange of marine waters between the Mediterranean and the Black Sea and creating the present oceanographic situation. This evolution conflicts with the cataclysmic role of the Bosphorus in the early Holocene as postulated in the ‘Catastrophic Flood’ hypothesis of Ryan et al. [Mar. Geol. 138 (1997) 119–126; Annu. Rev. Earth Planet. Sci. 31 (2003) 525–554]. It also contrasts with the history recorded from the Gulf of Izmit, where intermittent connection between these two bodies of water throughout much of the Quaternary is evident.

A revised stratigraphic framework for later Cenozoic sequences in the northeastern Mediterranean region

This study describes the lithostratigraphic character of mid-Cenozoic (Oligocene-Pliocene) sequences in different parts of the northeastern Mediterranean area and offers a detailed stratigraphic correlation for this region. The sequences concerned are drawn from the Camardi area (south-central Anatolia), the Adana Basin, the Misis Mountains and the Kyrenia Range (northern Cyprus) and the submerged Florence Rise (west of Cyprus). The stratigraphic relationships identified here indicate the following: (a) Following the middle Eocene (Lutetian) regression there was uplift throughout the entire region; (b) Episodes of fluvial and lacustrine deposition in intramontane settings ensued in most of this region during the late Eocene/early Miocene interval; (c) Following a regionally extensive phase of tectonic compression, major marine transgression commenced in the late Oligocene in northern Cyprus and in the early Miocene in adjacent southern Turkey, with the exception of the Ecemi§ Fault Zone where continental deposition continued; (d) These Oligo-Miocene transgressive sequences comprise a broadly diachronous complex of both shallow and deeper marine facies, including reefal carbonates, littoral clastics, basinal shales and fan-turbidites; (e) Deeper marine Miocene facies persisted longer in the Misis area and in northern Cyprus; (f) A regional regression occurred throughout most of the area during the late Serravallian to Tortonian interval and is marked by the abrupt, locally discordant appearance of extensive shallow marine, deltaic and fluvial deposits; (g) Continued regression in the Messinian led to the formation of significant evaporite deposits in the western and southern parts of the region, but localized uplift of the Misis area is attested by the initial deformation of the Neogene rocks there and the absence of Messinian sediments from this area; (h) In the Pliocene there was extensive emergence of the northern parts of the region interrupted by brief marine incursions. The present-day drainage pattern was established at this time; (i) Marine conditions persisted longer in northern Cyprus, where emergence occurred only in the latest Pliocene.

Tectonic controls on stratigraphic evolution of the Adana Basin, Turkey

The Neogene Adana Basin of SE Turkey was initiated after thrust emplacement of the Tauride Belt to the north of the basin. Seismic reflection profiles across the southern part of the Adana Basin provide information on structural and stratigraphic evolution of the basin. Based on seismic character and the identification of unconformities, three megasequences and two mega sequence boundaries are identified. The first megasequence is partly coincident with an early Miocene rifting event and it comprises reefs that have grown on fault footwall crests with fore and back-reef sediments in intervening lows. Subsequent rapid flexurally induced subsidence generated an underfilled basin which was then passively filled by turbiditic sediments (megasequence 2) showing aggradational character on seismic profiles. Further extensional faulting and coupled sinistral wrench faulting took place after the deposition of megasequence 2. Erosional truncation of its upper part is followed by the deposition of continental and shallow marine sediments of megasequence 3 which shows localized progradational sequences characteristic of shallow water deposition. Further minor extensional faulting took place after the deposition of megasequence 3.

Sedimentology of a Late Cenozoic collisional sequence: the Misis Complex, Adana, southern Turkey

Abstract This study is concerned with Miocene sequences formed within part of the Cukurova Basin of southern Turkey, a major downwarp created during the early stages of collision between the Afro-Arabian plate and the Tauride-Anatolian microplate assemblage. We report here the results of a combined stratigraphical, sedimentological, structure and geochemical study of the Misis Complex, a structurally elevated segment of Cukurova basin-fill. This analysis has demonstrated the structurally imbricated nature of the Misis sequences and the tectonic juxtaposition of originally well-separated coeval facies. The initial discernible phase of basin-filling (pre-Burdigalian) was marked by deep marine conditions and marginal tectonic instability (probably related to a late phase of Tauride nappe advance). The subsequent phase of crustal extension (Burdigalian/Early Tortonian) produced expansion of the Cukurova basin limits and an upwards-shoaling succession, in which sediment transport towards the southwest gradually became dominant, as a result of earlier suturing and uplift in northeasterly sectors of the collision zone. The Miocene arenites of the Misis Complex are petrographically diverse (with common siliciclastic and carbonate detrital admixtures) and mineralogically immature and their position in petrotectonic fields indicates a compound provenance from both recycled orogen and magmatic arc sources. A noteworthy petrographic feature is the compositional similarity of arenites from both shallow and deep marine facies. The general succession of Neogene facies observed in the Cukurova Basin and Misis Complex is consistent with their evolution within a perisutural foreland basin, but this interpretation is complicated by petrographic and geochemical features attributed to remnants of an older magmatic arc. Later stages of basin-filling are also marked by the local occurrence of “anomalous” palaeoenvironmental associations (including olistostromic units) attributed to contemporaneous intra-basinal tectonism.

Style, scale and significance of sand bodies in the Northern and Central Belts, southwest Southern Uplands

Sedimentological and biostratigraphical data from the Rhinns of Galloway and adjacent areas in SW Scotland confirm that deep-water depositional systems consistently operated along, and were sourced from, the northwestern margin of an asymmetrical basin during the late Ordovician and early Silurian, while pelagic facies accumulated simultaneously to the SE, providing a scenario analogous to many modern trench systems. Most of the observed sedimentological anomalies, with regard to this general model, can be explained within the context of the varied styles of trench-filling depositional systems, briefly reviewed here, and the major stratigraphic and sedimentologic features can be best explained in terms of a geotectonically evolving fore-arc region. Two main phases of development are recognized: (a) Llandeilo-late Ashgill: during this time interval the fore-arc trench region was tectonically juxtaposed against an active continental margin arc. Small- to medium-scale, SE-prograding sand-rich fans were formed within a relatively narrow trench, leading to axial diversion of the fans, initially to NE but later mainly to SW. Simultaneously a coarse volcanilithic sediment apron, flanking the arc, migrated gradually northeastwards, probably in response to relative fault displacement of the arc and trench; (b) Llandovery: during this time interval the fore-arc trench region was dominated by a variety of mainly fan-type depositional systems which were exclusively sourced (at least until the uppermost Llandovery) from the northwestern margin. The juxtaposition of coeval depositional systems differing significantly in sedimentological style and composition strongly suggests that the Llandovery sedimentation in this region occurred in several structurally separated sub-basins within the main trench system.

Tectonic connection of the Hellenic and Cyprus arcs and related geotectonic elements

Abstract The Cyprus Arc System forms part of a well-defined, presently active, plate boundary and is a critical area for understanding the evolution of the Eastern Mediterranean Sea. The available seismic reflection profiles are utilised in order to establish the nature and origin of the main tectonic features of the arc, which include: 1. (a) The Cyprus Trench, displaying evidence of underthrusting and morphostructural features typical of subduction zones. 2. (b) The Pytheus Trench, associated with right-lateral strike-slip movement and connecting the western end of the Cyprus Trench to the Strabo Trench sector of the Hellenic Trench System. 3. (c) A predominantly transtensional fault zone connecting the easternmost part of the Cyprus Trench via the Baer Bassit overthrust zone in Syria to the Dead Sea Transform Fault System. 4. (d) A zone of complex deformation, involving thrust and transform elements, running from the Misis Mountains of southeast Turkey through the Kyrenia Range in Cyprus to the Gulf of Antalya and transected by roughly N-S major shears (notably the Cape Gelidonya-Anaximander Mountains strike-slip zone), which appears to form the western boundary of the present active system of the Cyprus Arc. The nature of the shallow structures associated with the Cyprus Arc is consistent with a geotectonic model involving some post-Miocene rotation of the South Anatolian-Cyprus Block, probably induced by “escape dynamics” resulting from continent-continent collision in eastern Turkey and the development of the Maras triple junction in southeastern Turkey. The alternation of plate boundary sectors respectively characterised by thrusting and strike-slip displacement suggests that the shallow crust in this part of the eastern Mediterranean is in a compartmented and relatively brittle state, allowing accumulated boundary stresses to be accommodated largely by displacements and deformation along secondary features.

Sand body geometry in a sand-rich, deep-water clastic system, Miocene Cingöz Formation of southern Turkey

Abstract Three types of sandstone bodies, canyon-fill, tongues and lobes are recognized, and their geometry and spatial organization described within an elongate, W–E trending deep-water clastic system. The canyon-fill comprises sheet-like, fining upward packages that pinch-out rapidly (over 20 m laterally) where they onlap against the basin margin slope to the north. To the south, bed packages pinch-out more gradually over 400–500 m where they are confined by basin floor topography that forms one margin to the canyon. Down-system from the canyon, tongues form narrow and elongate (0.5–1 km wide and 25 km long) sandstone bodies. They are non-erosive, and are thus not channels, but sedimentation is focused within palaeotopographic lows formed by basement structure and differential compaction. Lobes occur close to the mouth of the canyon, overlying the tongues. Packages of lobes (net sandstone ∼80%) and interlobe deposits (net sandstone ∼40%) are cut by distributary channels that allow sediment to bypass the lobes. The overall asymmetric geometry and elongate nature of this sand-rich deep-water clastic system, and consequently sandstone distribution and architecture, are controlled by the basin margin slope and basin floor palaeotopography.

Basaltic tephra: potential new resource for ceramic industry

Abstract This preliminary study reveals that basaltic tephra(pumice) is a material suitable for the production of high quality ceramics and also provides important evidence concerning the transfer of the process of manufacture from the laboratory to commercial production. Specifically, the shapes of pores and the uniformity of the pore size frequency distributions in the basaltic ceramic preparations are the major textural properties controlling compressive strength, whereas the contents and textures of fibrous minerals occupying the pores appear to be less significant in determining the physical properties of these ceramics.