SUMMARYA detailed palaeointensity study was performed using the modified Thellier method on 18 Qu... more SUMMARYA detailed palaeointensity study was performed using the modified Thellier method on 18 Quaternary and Neogene volcanic units, ages ranging from 0.08 to 5.98 Ma, in Central Anatolia, Turkey. Robust data, which were estimated from 12 lava units in the study area, significantly increase the database of palaeomagnetic data, directions and absolute palaeointensity for the Anatolian region covering the time window back to ∼6 Ma. Previous studies sensitively dated the samples, except for one site dated in this study. The palaeointensity (VDM) value from the upper Miocene site estimated as 48.6 ± 9.2 μT (10.1 × 1022 ± 1.9 Am2) fits well into the Neogene VDM range in the data archives. For Pliocene samples with an age of 4.7 Ma, the palaeointensity was calculated to be 21.0 ± 4.7 μT. For these samples, an inclination of +42.9° was determined, and together with the results of low palaeointensity and normal polarity, this corresponds to the Nunivak or Sidufjall subchrons. These are nor...
The surveys of the Istanbul Prehistoric Research Project that have been carried out since 2014 in... more The surveys of the Istanbul Prehistoric Research Project that have been carried out since 2014 in and around the Istanbul Büyükçekmece Lake, discovered not only prehistoric materials but also a considerable number of small findings, ceramics and architectural elements from the Classical Period. A great deal of effort was spent to identify the long wall, extending roughly along the lake"s ancient coast line, which surfaces during the years of drought when the lake"s water recedes considerably. Antique geographers mention the region in a line or two, as a small town named after Athyra(s), a river flowing into the Marmara Sea from the north. Procopius, an important historian of the 6th Century, informs us in his book "On Buildings"(Greek: ΠερὶΚτισμάτων, PerìKtismáton; Latin: De aedificiis) that Emperor Justinian built a reservoir at the request of people affected by drought in a town called Athyra, near Constantinople. At first glance, knowing that the lake now not ...
Istanbul Darulfununun icinde bir Heyet ve Jeofizik Enstitusu egitim amacli olarak Turk astronom F... more Istanbul Darulfununun icinde bir Heyet ve Jeofizik Enstitusu egitim amacli olarak Turk astronom Fatin Gokmen tarafindan 1926 yilinda acilir. Ayni yilin egitim programinda “Meteoroloji ve Jeofizik” dersi gorunmektedir. Jeofizik Enstitusu 1948 yilinda tekrar duzenlenir ve 1950-1960 arasinda Fen Fakultesi icinde Prof. I. Ozdogan, Prof. Dr. Fouche ve Prof.Dr. J. Coulomb (Fransiz jeofizikciler), Prof. J. Barthels (Alman Jeofizikci)’in gayretleri saglam temellerini olusturur. 1968 yilinda, bir Tatbiki Jeofizik Kursusu kurulmus ve Jeofizik yuksek muhendisligi diploma programi lisans duzeyinde baslatilmistir. Haziran 1978’de, Istanbul Universitesinde yer Bilimleri Fakultesi ve bu fakulte icinde Jeofizik Muhendisligi Bolumu kurulmustur. 1982’de Kimya ve Yer bilimleri Fakultelerinin birlestirilmeleri ile Muhendislik Fakultesi kulmus ve onun bir bolumu olarak Jeofizik Muhendisligi Bolumu egitim ogretime baslamistir.
Summary This project covers the investigation of the formation process of two peatlands in the Ma... more Summary This project covers the investigation of the formation process of two peatlands in the Marmara Region in terms of humic substances and to identify the palaeoclimatic process through the pollen analysis and mineral magnetic studies. Ground penetrating radar survey (GPR) is applied on one of the lake, called Danamandira and characteristics of inner parts of the lake was determined and bathymetry map was created during the first phase.
Element records of wet and dry sediment samples or fossil shells show intense count rates with th... more Element records of wet and dry sediment samples or fossil shells show intense count rates with their high concentrations in sediments as primer factor at natural settlement ambiance. Second important count rate factor is focused to geometry of sediment layers which earned lateraly related with basin gravitational and tectonic mass displacements as in seismic events, even sample preperation deformations during field sampling is included to this second classification. Third generalization covers storage and measurement conditions at the before and during laboratory works. All of that factors efficent on value changings. For relative value gain Copper (Cu), Carbon (C) and Aluminium (Al) slits can be used on elemental measurements for eliminate effects of neighbour shell coils for fossils and angular lineation of sediment layers. They provides continious calibration control for more sharp element identification at measurements. Carbon slit usage proved how important on comparative densi...
SUMMARY Magnetostratigraphic and geochemical analyses were performed on two sediment cores recove... more SUMMARY Magnetostratigraphic and geochemical analyses were performed on two sediment cores recovered from the Sea of Marmara to investigate geomagnetic field variations over the last 70 ka. A chronology for each of the two cores was developed from eight AMS 14C datings, tephrochronology, and tuning of Ca concentrations with stadials and interstadials observed in Greenland ice core oxygen isotope data. Based on the age models, cores MD01–2430 and MRS-CS19 reach back to 70 and 32 ka, respectively. High average sedimentation rates of 43 cm kyr–1 for core MD01–2430 and 68 cm kyr–1 for core MRS-CS19 allow high-resolution reconstruction of geomagnetic field variations for the Sea of Marmara. Mineral magnetic properties are sensitive to glacioeustatic sea level changes and palaeoclimate variations in this region, reflecting the variable palaeoenvironmental conditions of the Sea of Marmara during last 70 ka. Despite the impairment of the palaeomagnetic record in some stratigraphic intervals...
Here we present magnetic properties of tephra layers in the cores taken from Lake Van, Eastern An... more Here we present magnetic properties of tephra layers in the cores taken from Lake Van, Eastern Anatolia, Turkey. Lake Van is the fourth largest terminal Lake in the world by volume (607 km3). It is 460 m deep and has a salinity of 21.4 per mil and a pH of 9.81. It is located on the East Anatolian Plateau with present day water level of 1648 m.a.s.l., and surrounded by large stratovolcanoes Nemrut, Suphan, Tendurek, and Ararat to the west and north. It has accumulated varved-sediments with tephra units, which all provide important paleoenvironmental records. After a seismic survey, four different locations were selected for coring in Lake Van, with water depths varying between 60 m and 90 m. Four cores having between 3 and 4.8 m length were analyzed for for element geochemistry using XRF Core Scanner analysis. The sub-samples were taken into plastic boxes with a volume of 6.4 cm3 for mineral magnetic analysis. The mineral magnetic measurements included magnetic susceptibility (χ), an...
The study area is located in the W Pontides. This study aimed at understanding the tectonic evolu... more The study area is located in the W Pontides. This study aimed at understanding the tectonic evolution of different tectonic units of the W Pontides by obtaining paleo-magnetic data from the Upper Creatceous volcanic rocks exposed in the Istanbul and Istranca regions. Oriented rock samples were collected from the Upper Cretaceous volcanic rocks at 15 sites. The mean value of denclination and inclination for Upper Creataceus samples were found to be 187 0 /-46 0 in the Stranja Region and 348 0 /40 0 in the ˙ Istanbul Region. The corresponding mean paleolatitudes were determined to be 27.4 0 for the Stranja Region and 22.8 0 for the Istanbul Region. However, the Upper Cretaceous volcanic stratigraphy in the Istanbul Region allows us to determine palae-olatitude variation with time. The mean values of paleolatitude were found to be20 23ånd 26rom the oldest (Poyraz) to the youngest (Kı sı rkaya) intervals. Therefore, we hypothesise that the Istanbul Fragment moved from southerly latitude...
Abstract Lake Van is the largest soda lake in the world, located on the east Anatolian Plateau in... more Abstract 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. We have studied 4.56 m (core VP0801) and 4.70 m (core VP0807) long cores recovered from −80 m and −65 m water depths located in SE and SW of Lake Van, respectively. The cores cover the last 8.4 ka and lithologically include three laminated sedimentary units. From top to the bottom, the units were dated 4.2 ka BP-present, 5.4–4.2 ka BP and older than 5.4 ka BP. According to carbon/nitrogen (atomic C/N values) the uppermost unit contains mainly organic matter of biodegraded soil origin and the middle and lower units C3 type vascular land-plant origin, suggesting decreased precipitation during 4.2 ka to present. We identified tephra layers previously dated by varve counting, and used the varve ages to obtain age models for the cores. We also obtained a total of eight Accelerator Mass Spectrometry (AMS) 14C dates from total organic carbon (TOC) in the two cores, close to the tephra layers. Comparison of the varve ages of the AMS 14C – dated samples with their corresponding AMS 14C dates indicates large differences, suggesting significant reservoir ages that range from 2.8 to 2.5 ka for 3.0–2.4 varve ka BP and from 2.8 to 3.3 ka for 8.0–5.9 varve ka BP. The results suggest that the reservoir age of the organic matter increases with the varve age of the sediments. This increase is mainly related to the rate of supply of “dead” carbon from the old carbonate rocks in the watershed of Lake Van, which was relatively higher during 8.4–5.9 ka than during 3.0–2.4 ka BP because of the higher atmospheric precipitation and higher rate of biochemical weathering during the former period.
Abstract Detailed magnetic analysis of the four sediment cores from Lake Van, Eastern Turkey dati... more Abstract 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.
ABSTRACT We present the results of mineral magnetic measurements (χ, SIRM, ARM, NRM) and geochemi... more ABSTRACT We present the results of mineral magnetic measurements (χ, SIRM, ARM, NRM) and geochemical XRF Core Scanner elemental analysis from four cores located in water depths of 60-80 m in different parts of Lake Van, eastern Turkey. Lake Van is the fourth largest terminal Lake in the world by volume (607 km 3). It is 460 m deep and has a salinity of 21.4 per mil and a pH of 9.81. It is located on the East Anatolian Plateau with present day water level of 1648 m.a.s.l., and surrounded by Quaternary Volcanoes (Nemrut and Süphan) to the west and north, and the Bitlis metamorphic rocks to the south. It has accumulated varved-sediments with tephra units, which all provide important paleoenvironmental records. The sediments extending back to 14570 a BP have been previously dated by varve counting (Landman et al., 1996). We have correlated our cores with the varve-dated cores of Landmann et al (1996) using the tephra units. Our cores extend back to 9.5 ka BP (varve years). We also obtained 10 AMS C-14 ages from total organic carbon in our cores, which indicate reservoir ages ranging from 2600 to 4275 a; the reservoir ages generally increase with the varve age of the sediments. Downcore profiles of all magnetic properties are highly correlatable between different cores, suggesting that the magnetic records are related to basinwide environmental changes rather than local effects. The magnetic properties of the cores are predominantly controlled by detrital paramagnetic minerals, with some contribution from small amount of ferrimagnetic minerals, all of which are derived from the catchment area. The tephra layers originating from Nemrut and Süphan volcanoes are characterized by strong ferrimagnetic minerals and high Zr, K, Si and Zn values. Downcore variation of magnetic properties and some geochemical elemental profiles (e.g., Fe, Ti, Zr, Ni, Ca) show good correlation .
The surveys of the Istanbul Prehistoric Research Project that have been carried out since 2014 in... more The surveys of the Istanbul Prehistoric Research Project that have been carried out since 2014 in and around the Istanbul Büyükçekmece Lake, discovered not only prehistoric materials but also a considerable number of small findings, ceramics and architectural elements from the Classical Period. A great deal of effort was spent to identify the long wall, extending roughly along the lake"s ancient coast line, which surfaces during the years of drought when the lake"s water recedes considerably. Antique geographers mention the region in a line or two, as a small town named after Athyra(s), a river flowing into the Marmara Sea from the north. Procopius, an important historian of the 6th Century, informs us in his book "On Buildings"(Greek: ΠερὶΚτισμάτων, PerìKtismáton; Latin: De aedificiis) that Emperor Justinian built a reservoir at the request of people affected by drought in a town called Athyra, near Constantinople. At first glance, knowing that the lake now not only supplies its ever-growing nearby population but also provides fresh water to Istanbul, the information given by Procopius didn"t seem to be convincing. The team focused its efforts to investigate if the embankment belongs to the mentioned dam, or not.The team consulted the historic records and also correlated with the other surface findings such as different artifacts, ceramics, and architectural elements to build a context. Underwater Side Scan Sonar, Geomorphological and Paleoclimatological work confirmed that the region, despite its ample fresh water sources available nowadays, was suffering a serious drought during the sixth century.
SUMMARYA detailed palaeointensity study was performed using the modified Thellier method on 18 Qu... more SUMMARYA detailed palaeointensity study was performed using the modified Thellier method on 18 Quaternary and Neogene volcanic units, ages ranging from 0.08 to 5.98 Ma, in Central Anatolia, Turkey. Robust data, which were estimated from 12 lava units in the study area, significantly increase the database of palaeomagnetic data, directions and absolute palaeointensity for the Anatolian region covering the time window back to ∼6 Ma. Previous studies sensitively dated the samples, except for one site dated in this study. The palaeointensity (VDM) value from the upper Miocene site estimated as 48.6 ± 9.2 μT (10.1 × 1022 ± 1.9 Am2) fits well into the Neogene VDM range in the data archives. For Pliocene samples with an age of 4.7 Ma, the palaeointensity was calculated to be 21.0 ± 4.7 μT. For these samples, an inclination of +42.9° was determined, and together with the results of low palaeointensity and normal polarity, this corresponds to the Nunivak or Sidufjall subchrons. These are nor...
The surveys of the Istanbul Prehistoric Research Project that have been carried out since 2014 in... more The surveys of the Istanbul Prehistoric Research Project that have been carried out since 2014 in and around the Istanbul Büyükçekmece Lake, discovered not only prehistoric materials but also a considerable number of small findings, ceramics and architectural elements from the Classical Period. A great deal of effort was spent to identify the long wall, extending roughly along the lake"s ancient coast line, which surfaces during the years of drought when the lake"s water recedes considerably. Antique geographers mention the region in a line or two, as a small town named after Athyra(s), a river flowing into the Marmara Sea from the north. Procopius, an important historian of the 6th Century, informs us in his book "On Buildings"(Greek: ΠερὶΚτισμάτων, PerìKtismáton; Latin: De aedificiis) that Emperor Justinian built a reservoir at the request of people affected by drought in a town called Athyra, near Constantinople. At first glance, knowing that the lake now not ...
Istanbul Darulfununun icinde bir Heyet ve Jeofizik Enstitusu egitim amacli olarak Turk astronom F... more Istanbul Darulfununun icinde bir Heyet ve Jeofizik Enstitusu egitim amacli olarak Turk astronom Fatin Gokmen tarafindan 1926 yilinda acilir. Ayni yilin egitim programinda “Meteoroloji ve Jeofizik” dersi gorunmektedir. Jeofizik Enstitusu 1948 yilinda tekrar duzenlenir ve 1950-1960 arasinda Fen Fakultesi icinde Prof. I. Ozdogan, Prof. Dr. Fouche ve Prof.Dr. J. Coulomb (Fransiz jeofizikciler), Prof. J. Barthels (Alman Jeofizikci)’in gayretleri saglam temellerini olusturur. 1968 yilinda, bir Tatbiki Jeofizik Kursusu kurulmus ve Jeofizik yuksek muhendisligi diploma programi lisans duzeyinde baslatilmistir. Haziran 1978’de, Istanbul Universitesinde yer Bilimleri Fakultesi ve bu fakulte icinde Jeofizik Muhendisligi Bolumu kurulmustur. 1982’de Kimya ve Yer bilimleri Fakultelerinin birlestirilmeleri ile Muhendislik Fakultesi kulmus ve onun bir bolumu olarak Jeofizik Muhendisligi Bolumu egitim ogretime baslamistir.
Summary This project covers the investigation of the formation process of two peatlands in the Ma... more Summary This project covers the investigation of the formation process of two peatlands in the Marmara Region in terms of humic substances and to identify the palaeoclimatic process through the pollen analysis and mineral magnetic studies. Ground penetrating radar survey (GPR) is applied on one of the lake, called Danamandira and characteristics of inner parts of the lake was determined and bathymetry map was created during the first phase.
Element records of wet and dry sediment samples or fossil shells show intense count rates with th... more Element records of wet and dry sediment samples or fossil shells show intense count rates with their high concentrations in sediments as primer factor at natural settlement ambiance. Second important count rate factor is focused to geometry of sediment layers which earned lateraly related with basin gravitational and tectonic mass displacements as in seismic events, even sample preperation deformations during field sampling is included to this second classification. Third generalization covers storage and measurement conditions at the before and during laboratory works. All of that factors efficent on value changings. For relative value gain Copper (Cu), Carbon (C) and Aluminium (Al) slits can be used on elemental measurements for eliminate effects of neighbour shell coils for fossils and angular lineation of sediment layers. They provides continious calibration control for more sharp element identification at measurements. Carbon slit usage proved how important on comparative densi...
SUMMARY Magnetostratigraphic and geochemical analyses were performed on two sediment cores recove... more SUMMARY Magnetostratigraphic and geochemical analyses were performed on two sediment cores recovered from the Sea of Marmara to investigate geomagnetic field variations over the last 70 ka. A chronology for each of the two cores was developed from eight AMS 14C datings, tephrochronology, and tuning of Ca concentrations with stadials and interstadials observed in Greenland ice core oxygen isotope data. Based on the age models, cores MD01–2430 and MRS-CS19 reach back to 70 and 32 ka, respectively. High average sedimentation rates of 43 cm kyr–1 for core MD01–2430 and 68 cm kyr–1 for core MRS-CS19 allow high-resolution reconstruction of geomagnetic field variations for the Sea of Marmara. Mineral magnetic properties are sensitive to glacioeustatic sea level changes and palaeoclimate variations in this region, reflecting the variable palaeoenvironmental conditions of the Sea of Marmara during last 70 ka. Despite the impairment of the palaeomagnetic record in some stratigraphic intervals...
Here we present magnetic properties of tephra layers in the cores taken from Lake Van, Eastern An... more Here we present magnetic properties of tephra layers in the cores taken from Lake Van, Eastern Anatolia, Turkey. Lake Van is the fourth largest terminal Lake in the world by volume (607 km3). It is 460 m deep and has a salinity of 21.4 per mil and a pH of 9.81. It is located on the East Anatolian Plateau with present day water level of 1648 m.a.s.l., and surrounded by large stratovolcanoes Nemrut, Suphan, Tendurek, and Ararat to the west and north. It has accumulated varved-sediments with tephra units, which all provide important paleoenvironmental records. After a seismic survey, four different locations were selected for coring in Lake Van, with water depths varying between 60 m and 90 m. Four cores having between 3 and 4.8 m length were analyzed for for element geochemistry using XRF Core Scanner analysis. The sub-samples were taken into plastic boxes with a volume of 6.4 cm3 for mineral magnetic analysis. The mineral magnetic measurements included magnetic susceptibility (χ), an...
The study area is located in the W Pontides. This study aimed at understanding the tectonic evolu... more The study area is located in the W Pontides. This study aimed at understanding the tectonic evolution of different tectonic units of the W Pontides by obtaining paleo-magnetic data from the Upper Creatceous volcanic rocks exposed in the Istanbul and Istranca regions. Oriented rock samples were collected from the Upper Cretaceous volcanic rocks at 15 sites. The mean value of denclination and inclination for Upper Creataceus samples were found to be 187 0 /-46 0 in the Stranja Region and 348 0 /40 0 in the ˙ Istanbul Region. The corresponding mean paleolatitudes were determined to be 27.4 0 for the Stranja Region and 22.8 0 for the Istanbul Region. However, the Upper Cretaceous volcanic stratigraphy in the Istanbul Region allows us to determine palae-olatitude variation with time. The mean values of paleolatitude were found to be20 23ånd 26rom the oldest (Poyraz) to the youngest (Kı sı rkaya) intervals. Therefore, we hypothesise that the Istanbul Fragment moved from southerly latitude...
Abstract Lake Van is the largest soda lake in the world, located on the east Anatolian Plateau in... more Abstract 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. We have studied 4.56 m (core VP0801) and 4.70 m (core VP0807) long cores recovered from −80 m and −65 m water depths located in SE and SW of Lake Van, respectively. The cores cover the last 8.4 ka and lithologically include three laminated sedimentary units. From top to the bottom, the units were dated 4.2 ka BP-present, 5.4–4.2 ka BP and older than 5.4 ka BP. According to carbon/nitrogen (atomic C/N values) the uppermost unit contains mainly organic matter of biodegraded soil origin and the middle and lower units C3 type vascular land-plant origin, suggesting decreased precipitation during 4.2 ka to present. We identified tephra layers previously dated by varve counting, and used the varve ages to obtain age models for the cores. We also obtained a total of eight Accelerator Mass Spectrometry (AMS) 14C dates from total organic carbon (TOC) in the two cores, close to the tephra layers. Comparison of the varve ages of the AMS 14C – dated samples with their corresponding AMS 14C dates indicates large differences, suggesting significant reservoir ages that range from 2.8 to 2.5 ka for 3.0–2.4 varve ka BP and from 2.8 to 3.3 ka for 8.0–5.9 varve ka BP. The results suggest that the reservoir age of the organic matter increases with the varve age of the sediments. This increase is mainly related to the rate of supply of “dead” carbon from the old carbonate rocks in the watershed of Lake Van, which was relatively higher during 8.4–5.9 ka than during 3.0–2.4 ka BP because of the higher atmospheric precipitation and higher rate of biochemical weathering during the former period.
Abstract Detailed magnetic analysis of the four sediment cores from Lake Van, Eastern Turkey dati... more Abstract 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.
ABSTRACT We present the results of mineral magnetic measurements (χ, SIRM, ARM, NRM) and geochemi... more ABSTRACT We present the results of mineral magnetic measurements (χ, SIRM, ARM, NRM) and geochemical XRF Core Scanner elemental analysis from four cores located in water depths of 60-80 m in different parts of Lake Van, eastern Turkey. Lake Van is the fourth largest terminal Lake in the world by volume (607 km 3). It is 460 m deep and has a salinity of 21.4 per mil and a pH of 9.81. It is located on the East Anatolian Plateau with present day water level of 1648 m.a.s.l., and surrounded by Quaternary Volcanoes (Nemrut and Süphan) to the west and north, and the Bitlis metamorphic rocks to the south. It has accumulated varved-sediments with tephra units, which all provide important paleoenvironmental records. The sediments extending back to 14570 a BP have been previously dated by varve counting (Landman et al., 1996). We have correlated our cores with the varve-dated cores of Landmann et al (1996) using the tephra units. Our cores extend back to 9.5 ka BP (varve years). We also obtained 10 AMS C-14 ages from total organic carbon in our cores, which indicate reservoir ages ranging from 2600 to 4275 a; the reservoir ages generally increase with the varve age of the sediments. Downcore profiles of all magnetic properties are highly correlatable between different cores, suggesting that the magnetic records are related to basinwide environmental changes rather than local effects. The magnetic properties of the cores are predominantly controlled by detrital paramagnetic minerals, with some contribution from small amount of ferrimagnetic minerals, all of which are derived from the catchment area. The tephra layers originating from Nemrut and Süphan volcanoes are characterized by strong ferrimagnetic minerals and high Zr, K, Si and Zn values. Downcore variation of magnetic properties and some geochemical elemental profiles (e.g., Fe, Ti, Zr, Ni, Ca) show good correlation .
The surveys of the Istanbul Prehistoric Research Project that have been carried out since 2014 in... more The surveys of the Istanbul Prehistoric Research Project that have been carried out since 2014 in and around the Istanbul Büyükçekmece Lake, discovered not only prehistoric materials but also a considerable number of small findings, ceramics and architectural elements from the Classical Period. A great deal of effort was spent to identify the long wall, extending roughly along the lake"s ancient coast line, which surfaces during the years of drought when the lake"s water recedes considerably. Antique geographers mention the region in a line or two, as a small town named after Athyra(s), a river flowing into the Marmara Sea from the north. Procopius, an important historian of the 6th Century, informs us in his book "On Buildings"(Greek: ΠερὶΚτισμάτων, PerìKtismáton; Latin: De aedificiis) that Emperor Justinian built a reservoir at the request of people affected by drought in a town called Athyra, near Constantinople. At first glance, knowing that the lake now not only supplies its ever-growing nearby population but also provides fresh water to Istanbul, the information given by Procopius didn"t seem to be convincing. The team focused its efforts to investigate if the embankment belongs to the mentioned dam, or not.The team consulted the historic records and also correlated with the other surface findings such as different artifacts, ceramics, and architectural elements to build a context. Underwater Side Scan Sonar, Geomorphological and Paleoclimatological work confirmed that the region, despite its ample fresh water sources available nowadays, was suffering a serious drought during the sixth century.
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