A 500,000-year-long sediment archive drilled in eastern Anatolia

Sedimentary archives host a wealth of information that can be used to reconstruct paleoclimate as well as the tectonic and volcanic histories of specific regions. Long and continuous archives from the oceans have been collected in thousands of locations by scientific ocean drilling programs over the past 40 years. In contrast, suitable continental archives are rare because terrestrial environments are generally nondepositional and/or subject to erosion. Lake sediments provide ideal drilling targets to overcome this limitation if suitable lakes at key locations have existed continuously for a long time

The radiocarbon reservoir age of Lake Van, eastern Turkey

Lake Van is the largest soda lake in the world, located on the east Anatolian Plateau in Turkey. Its varved sediments provide an excellent archive of high-resolution paleoclimate record for the Near East. Varve-counting and radiocarbon methods are therefore important dating techniques for investigating the Lake Van sedimentary paleoclimate record

Marmesonet Cruise. R/V Le Suroit. Leg1

The MARMESONET cruise is part of the Marmara Demonstration Mission Program supported by ESONET Network of Excellence (European Seafloor Observatory Network), within the 6th European Framework Programme. Main partners are: Ifremer, CNRS/CEREGE, Istanbul Technical University, TUBITAK, Institute of Marine Science and Technology of Dokuz Eylül Universitesi (Izmir), INGV (Rom) and ISMAR (Bologna). Marmesonet is also the follow-on of the Franco-Turk collaborative programme that resulted in numerous cruises in the Sea of Marmara since 2000. The objectives of the MARMESONET cruise were: 1) to study the relationship between fluids and seismicity along the Sea of Marmara fault system ; 2) to carryout site surveys prior to the implementation of permanent seafloor observatories in the Marmara Sea through ESONET. The cruise is divided in 2 parts: Leg I (from november 4th to november 25th, 2009), mainly dedicated to: i) the high resolution bathymetry at potential sites of interest for future permanent instrumentation using the Autonomous Unmanned Vehicle (AUV)Asterx of Ifremer/Insu ; ii) the systematic mapping of the gas emissions sites on the Marmara seafloor ; iii) the deployment of the Bubble Observatory Module (BOB) in the Çinarçik basin. Leg II (from november 28th november to december 14th, 2009), for 3D, High Resolution Seismic imagery of the fluid conduits below the observatory site planned at the Western High. The present report only concerns Leg I. A total of 19 dives were completed during Leg I: 16 with the multibeam echosounder SIMRAD EM2000 (200 kHz), among which 12 were successful and 4 failed ;3 with the CHIRP sédiment penetrator (1 test dive and 2 operational, both were unfortunately with early stop recording). Main results are: The absence of recent, visible deformation on the segment south of Istanbul. Wether or not this segment is locked or creeping remains an open question. The site south of Istanbul thus requires a massive effort to assess the deformation, particularly through submarine geodesy and piezometry. The plausible presence of a 4 km, right-lateral offset on the Western High, between N30 oriented structures related to cold seeps. Gas emission sites aresystematically related tozones of High reflectivity mapped on the AUV imagery AUV imagery reveals the traces of intensive, human activity, which shows the necessity to ensure the security of the future cables by enforcing a clearance area Last but not least, the exact position of the future observatories is now established, at the Central High and at the Western High sites. Some chirp profiles suggest that the 1912 earthquake probably extended up to the Western High, but not the fault is not visible on all of them. Further work is needed. The SIMRAD EM-302 multibeam echosounder was used to map the water column, providing a complete coverage ofslopes foot and ofthe central shear zone. Results require further analysis to establish the correlation between acoustic anomalies and active faults, as gas emissions appear to be a common feature in the the Sea of Marmara. A noticeable feature is the important gas emission activity along the base of thewestern of slope of the Tekirdag Basin, suggesting that the gas réservoirs from the Thrace Basin are presently leaking out into the Sea of Marmara. In addition, shipboard CHIRP data were collected along with EM-302. 23 cores were taken (13 with gravity corer, 3 with Küllenberg and 7 with interface corers). A total of 24 additional heat flow measurementswere also collected. Finally, 2 OBSs were deployed to complete the coverage of the OBSs dropped with R/V Urania in september 2009. The assistance of the Turkish Coast Guard largely contributed to the success of the operation. We greatly acknowledge the Coast Guard, as well as SHOD, the Department for Hydrography and Oceanography of Turkey, who made the cruise possible in a heavy trafic area. The captain, Jean-René Gléhen, and all crew members of R/V Le Suroit, are also greatly acknowledged.La campagne constitue l’une des missions de démonstration soutenues par ESONET. Elle résulte d’un partenariat entre l’Ifremer, le CNRS, l’INSU, l’Université Technique d’Istanbul, l’Institut des Sciences Marines d’Izmir, le CNR-ISMAR (Bologne) et l’INGV (Rome). La plupart des objectifs du premier leg de la campagne Marmesonet, du 4 au 25 novembre 2009, ont été atteints, grâce à trois facteurs principaux: i) la météo exceptionnellement favorable ; ii) la bienveillance des garde-côtes de la Marine Turque ; iii) le professionnalisme des équipes (équipage et sédentaires)

Discrimination of Holocene tephra units in Lake Van using mineral magnetic analysis

Detailed magnetic analysis of the four sediment cores from Lake Van, Eastern Turkey dating back to 9.4 cal ka BP were carried out for discriminating and correlating tephras and laminated sediments in four different cores. Six tephra units (T0, T1, T2, T3, T4 and T5) with distinct magnetic properties were identified in the cores. The tephra units are characterized by ferrimagnetic material, with a grain size in the pseudo single domain (PSD) range. There is no significant correlation between magnetic susceptibility peaks of the different tephra units except for the tephra T1 and T2. On the contrary ARM profiles show significant correlations as remanent magnetization indicators. The tephra units T1 and T2, have a higher magnetic susceptibility and a higher intensity of remanent magnetization, and finer grain size than the other tephra units. The results suggest that there is a clear difference between the magnetic properties of the different tephra units and the lake sediments. Our findings show that also differential deposition of volcanic material including magnetic mineral occurs during the transport with distance from the volcanic source. (C) 2018 Elsevier Ltd and INQUA. All rights reserved

A 3800 yr paleoseismic record (Lake Hazar sediments, eastern Turkey): Implications for the East Anatolian Fault seismic cycle

The East Anatolian Fault (EAF) in Turkey is a major active left-lateral strike-slip fault that was seismically active during the 19th century but mostly quiet during the 20th century. Geodetic data suggests that the fault is creeping along its central part. Here we focus on its seismic history as recorded in the sediments of Lake Hazar in the central part of the EAF. Sediment cores were studied using X-ray imagery, magnetic susceptibility, grain-size, loss-on-ignition and X-ray fluorescence measurements. Recurring thin, coarse-grained sediment units identified as turbidites in all cores were deposited synchronously at two deep study sites. The turbidite ages are inferred combining radiocarbon and radionuclide (Cs-137 and Pb-210) dating in an Oxcal model. A mean recurrence interval of similar to 190 yrs is obtained over 3800 yrs. Ages of the recent turbidites correspond to historical earthquakes reported to have occurred along the EAF Zone or to paleoruptures documented in trenches just northeast of Lake Hazar. The turbidites are inferred to be earthquake-triggered. Our record demonstrates that Lake Hazar has been repeatedly subjected to significant seismic shaking over the past 3800 yrs. The seismic sources are variable: similar to 65% of all turbidites are associated with an EAF source. The seismic cycle of central EAF is thus only partly impacted by creep

Free gas and gas hydrates from the Sea of Marmara, Turkey: chemical and structural characterization

Gas hydrates and gas bubbles were collected during the MARNAUT cruise (May–June 2007) in the Sea of Marmara along the North Anatolian Fault system, Turkey. Gas hydrates were sampled in the western part of the Sea of Marmara (on the Western High), and three gas-bubble samples were recovered on the Western High, the Central High (center part of the Sea of Marmara) and in the Çinarcik Basin (eastern part of the Sea of Marmara). Methane is the major component of hydrates (66.1%), but heavier gases such as C2, C3, and i-C4 are also present in relatively high concentration. The methane contained within gas hydrate is clearly thermogenic as evidenced by a low C1/C2 + C3 ratio of 3.3, and carbon and hydrogen isotopic data (δ13CCH4 of − 44.1‰ PDB and δDCH4 of − 219‰ SMOW). A similar signature is found for the associated gas bubbles (C1/C2 + C3 ratio of 24.4, δ13CCH4 of − 44.4‰ PDB) which have the same composition as natural gas from K. Marmara-af field. Gas bubbles from Central High show also a thermogenic origin as evidenced by a C1/C2 + C3 ratio of 137, and carbon and hydrogen isotopic data (δ13CCH4 of − 44.4‰ PDB and δDCH4 of − 210‰ SMOW), whereas those from the Çinarcik Basin have a primarily microbial origin (C1/C2 + C3 ratio of 16,600, δ13CCH4 of − 64.1‰ PDB). UV-Raman spectroscopy reveals structure II for gas hydrates, with CH4 trapped in the small (512) and large (51264) cages, and with C2H6, C3H8 and i-C4H10 trapped in the large cages. Hydrate composition is in good agreement with equilibrium calculations, which confirm the genetic link between the gas hydrate and gas bubbles at Western High and the K.Marmara-af offshore gas field located north of the Western High. We calculate the characteristics of the hydrate stability zone at Western High and in the Çinarcik Basin using the CSM-GEM computer program. The base of the structure II hydrate stability field is at about 100 m depth below the seafloor at the Western High site, whereas in the Çinarcik Basin, P–T conditions at the seafloor correspond to the uppermost range for structure I hydrate formation from microbial gas