Nizamettin Kazanci

Abrupt environmental changes within a late Holocene lacustrine sequence south of the Marmara Sea (Lake Manyas, N-w Turkey): possible links with seismic events

Abstract A coring campaign in Lake Manyas (Kus Golu) on the southern coast of the Sea of Marmara (Turkey) has provided insights into basin infilling processes during the upper 11 metres of the sedimentary record. Combined sedimentary features between 5 and 4 m depth have been explained by a seismite. A brittle mixed layer (uniquely rich in seeds and ostracod valves) was widely detected at 4 m downcore. This has been interpreted as being the result of a seiche either through a salt inundation linked to a tsunami in the Sea of Marmara (the large-scale scenario) or a local hydrothermal fluid discharge (the small-scale scenario). Ostracod valves, which are usually not preserved in Lake Manyas sediment, are either incorporated here as tsunami debris (providing a spatially averaged snapshot of the regional assemblage) or are locally preserved following a temporary geochemical/hydrochemical change of the water of unknown duration (but probably several decades). The brittle mixed layer overlies cracks resulting from the direct effects of the seismic shock wave on slightly compacted sediment. At around 964 cm depth palynological and particle-size analyses indicate a change from backswamp to open lacustrine conditions. The end of the backswamp has been correlated with a decrease in the level of the Sea of Marmara from 4000 to 3000–2800 yr ago (uncal.), caused by regional tectonic movements. An age–depth model is presented based on two AMS radiocarbon dates, on the palynological detection of the end of the Beysehir Occupation Phase (130 cm above the event) and on maximal sedimentation accumulation rates obtained by radionuclide analyses. The entire study sequence covers the last 4300 yr. The paper examines the possibility of an Early Byzantine age for the seismic event. This may have been the historical event at AD 460 that destroyed Cyzicus (the ancient Erdek, 20 km north of the lake) and various villages in the interior and was felt widely in the then-known world. Other possibilities include various local and regional events in that same period: the Early Byzantine Tectonic Paroxysm and the large earthquake in AD 447 that affected the entire Sea of Marmara region.

Sea-level changes and related depositional environments on the southern Marmara shelf

Abstract Petrographic data obtained from 182 surface sediment samples together with the available bathymetric data are used to investigate the effects of the last major sea-level changes on shelf evolution in the southern Sea of Marmara. Grain-size analysis reveals the presence of at least three belts or zones which are rich in coarse-grained (sand and gravel) sediments. These coarse-grained belts which are up to 45 km long, 15 km wide, show up to 20 m of relief and are presently found at 40–80 m (average 60 m) water depths. Based on microscopic examination and residual analysis, the sediments from these belts are interpreted as indicators of high-energy shallow waters where detrital siliciclastics, with some benthic contribution, accumulated. The presence of a 62–65 m deep sill in the Canakkale Strait and the consideration of sea-level curves would suggest that the Marmara shelves must have been subaerially exposed down to −65 m water depths for about 10,000 yrs (22,000–12,000 yrs B.P.), sufficient time to modify former shelf topographies and form such bottom relief. While difficult to date, we believe that coarse-grained belts found on the southern Marmara shelf must be relict (i.e., former shorelines, beaches) and their formation is largely related to low stands of sea-level during the Late Pleistocene regression and early Holocene transgression. However, the available high-resolution seismic profiling data suggest that the neotectonism in this seismically active Sea of Marmara plays an important role to explain the raise of these older shorelines to their present levels on the sea-floor.

A Pleistocene, pyroclastic-poor maar from central Anatolia, Turkey: influence of a local fault on a phreatomagmatic eruption

In central Anatolia, the Late Pleistocene Narkoy maar formed on a fault zone. A 5-m-thick pyroclastic succession erupted from a crater 900 m in diameter. The presence of gas fumeroles, hot springs, and hydrothermal alteration zones indicates that the area is geothermally active. The products of the maar are large blocks and lapilli to coarse ash. Planar bedding and cross-stratification are well developed within coarse ash beds. The maar deposits were generated by a single period of phreatomagmatic explosion with two episodes. The first episode produced wet eruption clouds, while the second one was relatively dry in nature. The estimate of the volume of pyroclastic ejecta compared with the dimensions of the maar demonstrates a material deficiency, which is attributed to a large volume of gas emanated during the phreatomagmatic explosion along a fault presently cross-cutting the maar. In addition, a relatively small volume of magma intruded along the fault and mixed with meteoric water in the fault zone to produce the phreatomagmatic eruption. The existence of a hydrothermal system in the fault zone is important in affecting the eruption style and evolution of Narkoy maar.

Enigmatic new ungulates from the Early Middle Eocene of central Anatolia, Turkey

Abstract Four new ungulate species described here from the early middle Eocene Uzunçarsidere Formation, near Ankara, Turkey present a phylogenetic and biogeographic puzzle. The four species, known from jaws, teeth, and skull and postcranial fragments, share a suite of diagnostic dental features (selenolophodont molars, all lower molars lacking hypoconulids, premolars with metacones small or absent, and narrow, short premolar talonids) and are included in a single new genus, Hilalia. Hilalia saribeya, H. selanneae, H. sezerorum, and H. robusta are distinguished from each other by size and details of premolar morphology. Cladistic analysis indicates that although Hilalia shares a common ancestor with perissodactyls, hyracoids and some “condylarths” to the exclusion of artiodactyls, its position relative to those taxa is unresolved—the calcaneum lacks derived features of artiodactyl, perissodactyl or hyracoid calcanea, some features of Hilalias molar morphology are convergent with features in some hyracoids, perissodactyls, and selenolophodont “condylarths”, and Hilalia has more primitive premolars than most members of those groups. The affinities of some other members of the Uzunçarsidere mammal fauna, including an embrithopod, marsupials, and a possible proboscidean, have suggested that central Anatolia may have served as a biogeographic crossroads for mammalian dispersal among Asia, Africa, and Europe during the early Paleogene. However, the absence of convincing links between Hilalia and any of the increasingly well-known Paleogene ungulates of Asia, Indo-Pakistan, and Africa, or those of Europe and North America suggests that our understanding of early Paleogene ungulate evolution and biogeography is far from complete.

Development of a mass flow-dominated fan-delta complex and associated carbonate reefs within a transgressive Paleocene succession, central Anatolia, Turkey

Abstract A Paleocene basin-fill succession (Dizilita¢ler Formation) has been studied in an area north of Ankara, Turkey. This basin-margin elastic succession comprises basal alluvial deposits (250 m thick), few vertically stacked marine fan-delta sequences (450 m), and sandy turbiditic deposits (650 m) at the top. The overall stratigraphic facies pattern is transgressive, but the fan-delta sequences represent major regressive (shoreline progradation) pulses. Fringing and patchy carbonate reefs separate these sequences, marking the favourable climate and a reduction in clastic influx during the episodes of fan-delta drowning due to relative rises of sea level. The fan-delta system was persistently dominated by gravelly mass flows, with subordinate braided-stream distributaries. The morphology, particularly slope inclination, of the successive fan-delta wedges was each determined largely by the magnitude of the preceding sea-level rise (actual water depth) which itself controlled the type of reefs. The basin was subsiding, and the five pulses of coarse-clastic influx separated by abrupt sea-level rises are attributed to active faulting at the basin margin. Broader down-faulting and basin expansion promoted deeper-marine turbiditic sedimentation.

Sedimentology of the Miocene evaporitic succession in the north of Çankiri-Çorum basin, central Anatolia, Turkey

The upper Miocene non-marine sediments of the Çankiri-Çorum basin in central Anatolia, have both evaporitic and non-evaporitic successions. These sediments were deposited in an evaporitic lake which had temporary episodes of palustrine conditions in response to seasonal or climatic changes. The successions show different facies such as sulfates, carbonates and siliciclastics. The sulfates comprise primary, reworked and diagenetic gypsum. The primary deposits are predominantly laminated gypsum, bedded gypsum and selenite. The reworked (detrital) gypsum comprises gypsite, gypsarenite, gypsrudite and breccias. The diagenetic type comprises micro- and macrogypsum nodules. The carbonates mainly include clayey limestone, oolitic limestone and dolomite. The siliciclastics comprise red beds and both channel and non-channel, conglomerates and mudstones.Laminated gypsum, composed of alternating gypsum and dolomite, was a result of environmental schizohalinity. Bedded gypsum was precipitated in the deeper part of the lake during high evaporation periods. Chevron-type selenite crystals formed on saline mud flats during the times of aridity, whereas the discoidal-type seen in the organic-rich mudstones occurred in the gypsiferous marshes during the times of humidity. Reworked (detrital) gypsum dominates the lake margin. These formed during periodic wet episodes that caused reworking of primary gypsum. Gypsum nodules occurred as both early and late diagenetic products. Carbonates and siliciclastics were deposited during the freshening periods of the lake.Climatic or seasonal changes were the main causes of the depositional styles of the upper Miocene evaporitic and non-evaporitic lacustrine deposits in Çankiri-Çorum basin. Additionally, the transition upward from alluvial to lake environment implies an important change in drainage patterns that likely occurred as a result of marginal fault activity.

Facies changes and high calorific peat formation in a quaternary maar lake, central Anatolia, Turkey: the possible role of geothermal processes in a closed lacustrine basin

Abstract The sedimentary infill of the Acigol maar lake, one of the volcanic centres in the Cappadocia district of Anatolia, contains unusual, high-calorific sub-Recent peat deposits, of which the origin is attributed to geothermal processes. The sedimentary facies record is analyzed to reconstruct the lakes depositional history and to disentangle the combined signal of climatic and geothermal factors. The facies succession comprises: a lake-fringe clastic apron shed from the maar walls; early-stage, coarse-grained tuffaceous deposits of the lake proper, intercalated with brecciated mudstones and limestones; and final-stage, fine-grained tuffaceous deposits of the lake proper, intercalated with peats and plant-bearing clastics and with some terminal travertines. The closed lake was highly dependent on climate, particularly precipitation, and the depositional conditions were further controlled by a connective hydrothermal system which itself was driven by the input of meteoric water. The associated heat flow played an important role by creating a microclimatic niche, where even the impoverished late-Quaternary (cold regional climate) vegetation could flourish and form substantial peats. The varying hydrological budget of the lake was the main “switching” mechanism for the peat-forming conditions, with two water-depth thresholds involved. If the lake level rose too high, the low vegetation was drowned and hemipelagic clastic sedimentation prevailed. If the lake level fell too low, the vegetation was killed and formation of travertine took place. The heat flow through the pore water and clastic sediments was crucial to the high maturation of the peat deposits.

Geology of a new Late Miocene mammal locality in central Anatolia, Turkey

Abstract The new mammal locality of Akkasdagi yielded a rich fauna dated as Middle Turolian. It is situated in the southern part of the Cankiri-Corum Basin in central Anatolia. In the Akkasdagi area, the sedimentary deposits, mapped as the Kizilirmak Formation, consist of tuffs and lacustrine limestones intercalated with clastic deposits, whilst in its type section situated to the north near Kizilirmak town, this formation is mainly formed of fluviatile deposits. Facies distribution and geological observations led to conclude that during the Miocene, depositional centers migrated from the north to the south of this basin.

Genetic framework of Neogene–Quaternary basin closure process in central Turkey

Central Turkey represents the only orogenic plateau in the Mediterranean region. Also, the largest closed drainage basin and the largest intracontinental basin of Turkey, the Lake Tuz Basin, is located in this region. Results from a three-dimensional (3-D) computer modeling study of the Lake Tuz Basin indicate a southward-deepening freshwater lake basin with great depth in the Mio–Pliocene, which regressed toward the north during the Plio–Quaternary into the shallow saline lake basin it is today. The spatio-temporal variations of Neogene and Quaternary deposits reflect the main effects of internal forces (isostasy>volcanism>faulting) that were caused by lithospheric slab breakoff and subsequent asthenospheric upwelling under central Turkey. Climatic change played a relatively minor role during these periods and was closely associated with the results of internal forces.

GÜNEY MARMARA BÖLGESİNDEKİ BÜYÜK VADİLERİN OLASI DEŞİLME ZAMANI

Surface water and sediments derived from the southern Marmara region (= SusurlukDrainage basin- SDH) transport to lakes Manyas and Ulubat first and then go to the Sea ofMarmara via the Kocasu River only. The present drainage system of the SDH provides a goodopportunity to study erosion rate and subsequently occurrence times of large-scale valleys inthe region. To achieve it, depositional characteristics and ion contents of the ancientlacustrine sediment has been investigated and re-interpreted using cores taken from LakeUlubat. The boron content of these sediments increased upward suddenly at the 4 m level,most probably due to starting of erosion at Emet borate beds in the drainage basin. Takinginto consideration equilibrium between natural erosion and sedimentation, the incision ratein the Emet valley was found 1.4 cm.yr-1. From here one can calculate a time span of 75 kyfor the formation of the whole valley itself. However, it is known that working of the geologicalprocesses was not monotonous in the past; hence, this date is not absolute. Newertheless,formation of the large valleys of the southern Marmara region shouldn’t be older than 300kyrs. An important reason on rapid erosion was likely lowered base-level as the Marmara Seawas a closed lake during the last Glacial Period. High altitudinal difference between sourceand depositional areas caused acceleration of the erosion.1. Girifl