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See detailLacustrine clay mineral assemblages as a proxy for land-use and climate changes over the last 4 kyr: The Amik Lake
El Ouahabi, Meriam ULg; Hubert, Aurelia ULg; Allan, Mohammed ULg et al

Poster (2017, May 10)

Lake sediments are sensitive to landscape changes and most of these changes seem to be modulated by land-use (anthropogenic factors) coupled to palaeoenvironmental/palaeoclimatic changes. In its detrital ... [more ▼]

Lake sediments are sensitive to landscape changes and most of these changes seem to be modulated by land-use (anthropogenic factors) coupled to palaeoenvironmental/palaeoclimatic changes. In its detrital fraction, the lacustrine sediments record the history of soil erosion within its catchment via the inputs of clays and others detrital products. Within a Mediterranean context, the study investigates the upper sediments infilling the central part of the Amik basin in southern Turkey. This tectonic basin was occupied and exploited by modern human at least since 6000-7000 BC. We focus on the clay mineralogy (x-ray diffraction on oriented aggregates) and magnetic susceptibility measurements (Bartington) of the sedimentary record in the area over the last 4000 years, to assess environmental changes in relation with the different land uses and/or weathering during the successive Bronze, Iron, Roman, Islamic/Ottoman and Modern civilizations. The clay fraction of Amik Lake sediments comprises smectite, kaolinite, illite, chlorite and chlorite/smectite mixed layers that are the inherited clay phases. A relative change in abundance and crystallinity and chemistry of illite attests that environmental conditions evolved in the Amik Plain from the Bronze to Modern Age in relation with climates and/or land-use changes. The history of the Amik Lake reveals different soil erosion episode. The most intense erosion phase occurred during the Bronze/Iron Ages as indicated by the clay and magnetic susceptibility proxies. The Roman period was an exceptional period with soil erosion products arriving from the watershed, probably due the water channelization. A reduction of soil erosion occurred during the post Roman period until nowadays. Significant pedogenesis transformations are evidenced, especially during the Islamic/Ottoman periods suggesting intense chemical weathering conditions related to climate change. [less ▲]

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See detailSedimentation influx and volcanic interactions in the Fuji Five Lakes: implications for paleoseismological records
Lamair, Laura ULg; Hubert, Aurelia ULg; Yamamoto, Shinya et al

Conference (2017, April 27)

The Fuji Fives Lakes are located at the foot of Mount Fuji volcano close to the triple junction, where the North American Plate, the Eurasian plate and the Philippine Sea Plate meet. These lakes are ... [more ▼]

The Fuji Fives Lakes are located at the foot of Mount Fuji volcano close to the triple junction, where the North American Plate, the Eurasian plate and the Philippine Sea Plate meet. These lakes are ideally situated to study Mount Fuji volcanism and the interaction between volcanism, changes in lake sedimentation rates and the ability of lakes to record paleoearthquakes. Here, we present newly acquired geological data of Lake Yamanaka and Lake Motosu, including seismic reflection profiles, gravity and piston cores. These two lakes and their respective watersheds were affected by several eruptions of Mount Fuji. Lake Yamanaka, a very shallow lake (max. depth 14 m), was heavily impacted by the scoria fall-out of the A.D. 1707 Hoei eruption of Mount Fuji. A detailed investigation of the effect of the Hoei eruption was conducted on short gravity cores, using high resolution XRD, C/N and 210Pb/137Cs analyses. The preliminary results suggest that the sedimentation rate of Lake Yamanaka drastically reduced after the Hoei eruption, followed by an increase until the present day. Similarly, lacustrine sedimentation in Lake Motosu (max. depth 122 m) was disturbed by Mount Fuji volcanism at a larger scale. The watershed of Lake Motosu was impacted by several lava flows and scoria cones. For example, the Omuro scoria cone reduced the catchment size of Lake Motosu and modified its physiography. The related scoria fall out covered an extensive part of the lake catchment and reduced terrigenous sedimentary influx to Lake Motosu. Within the deep basin of Lake Motosu, seismic reflection data shows two different periods that are distinguished by a major change in the dominant sedimentary processes. During the first period, sublacustrine landslides and turbidity currents were the dominant sedimentation processes. During the second one, the seismic stratigraphy evidences only deposition of numerous turbidites interrupting the hemipelagic sedimentation. Changes in sedimentary processes can be linked to the modification of the lake watershed by Mount Fuji volcanism, leading to a decrease in the sediment volume that can be remobilized, and therefore disappearance of large sublacustrine landslides. Turbidites are deposited due to surficial remobilization of lake slope sediments most probably as a result of earthquake shaking. When studying sedimentological records of lakes to define the paleoearthquake record, eruptions of nearby volcanoes should be taken into account. This study suggests that a large magnitude earthquake occurring few decades after a volcanic eruption (with large scale scoria fall-out), might not be recorded in a lake, or would only be fingerprinted in the sedimentary record by small turbiditic flows. References: Miyaji N., Kan'no A., Kanamaru T., Mannen K. 2011. High-resolution reconstruction of the Hoei eruption (AD 1707) of Fuji volcano, Japan. Journal of Volcanology and Geothermal Research 207, 113–129. [less ▲]

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See detailThe role of natural hazards and human activities on change of sedimentation patterns: The case of Lake Yamanaka (Fuji Five Lakes, Japan)
Lamair, Laura ULg; Hubert, Aurelia ULg; El Ouahabi, Meriam ULg et al

Conference (2017, April 10)

The last eruption of Mt Fuji (Japan) occurred in A.D. 1707. The eruption lasted 16 days from 16 December 1707 to 1 January 1708 (Tsuya, 1955) and 1.8 km3 of volcanic materials were ejected in total ... [more ▼]

The last eruption of Mt Fuji (Japan) occurred in A.D. 1707. The eruption lasted 16 days from 16 December 1707 to 1 January 1708 (Tsuya, 1955) and 1.8 km3 of volcanic materials were ejected in total (Miyaji et al., 2011). Lake Yamanaka, a very shallow lake (max. 14. 3 m depth) located at the foot of the east-north-eastern flank of Mt Fuji, was heavily impacted by the eruption. A thick scoria layer entirely covered the catchment of Lake Yamanaka. The thickness of the deposit varies from 5 to 37 cm around Lake Yamanaka and reaches up to 149 cm at the south-west extremity of the catchment (Miyaji et al., 2011). In order to study the influence of Hoei eruption on Lake Yamanaka, 5 gravity cores were taken during the 2014 QuakeRecNankai campaign. The Hoei scoria was present at the bottom of the one core and in the core catcher of the four other cores. High resolution magnetic susceptibility, XRD, XRF, LOI, C/N and 210Pb/137Cs analyses were performed on the gravity cores. The results shows three distinct periods of sedimentation: (1) From Hoei eruption to A.D. 1900; (2) From A.D. 1900 to A.D. 1990; (3) From A.D. 1990 to A.D. 2014. The first period is characterized by a very low sedimentation rate (~0.07 cm/yr). During this period, the sediments of the catchment were trapped below the thick Hoei scoria layer. However, peaks of terrigenous input are recorded. We link such detrical signals with violent typhoons that hit the Fuji Five Lakes region. The water from the heavy rains percolated through the porous thick scoria layer and saturated it. As a result, surface runoffs carried the sediments from the catchment into Lake Yamanaka. The second period (from A.D. 1900 to A.D. 1990) is defined by an increase of the sedimentation rate (~0.16 cm/yr). The development of soil and the agriculture (e.g. pastureland, rice field, mulberry plantations) reduced the impact of Hoei scoria. The terrigenous inputs are higher than previously but remained more or less constant during this period of time. As the thickness of the scoria layer is partially reduced or covered by new soil, rains triggered by smaller typhoons could drain the sediments from watershed and transport them into the lake. The most recent period representing the last 27 years is characterized by a very high sedimentation rate (~1.036 cm/yr). The transition between period 2 and period 3 corresponds to the development of mass tourism and the urbanization around Lake Yamanaka. It is marked by an increasing of atmospheric pollution (Pb, Zn). In the upper part of the cores, a peak of 137Cs is observed. Such peak is related to cesium fall-out after Fukushima incident in 2011. In addition to the fingerprint of human impact, the lake also record a terrigenous signal related to the 2007 Fitow typhoon which provoked damage in the area. This study highlights the influence of eruptions and typhoons on the sedimentation of Lake Yamanaka. In the present day, the sedimentation recovery after a major eruption is accelerated by human activity. References: Miyaji N., Kan'no A., Kanamaru T., Mannen K. 2011. High-resolution reconstruction of the Hoei eruption (AD 1707) of Fuji volcano, Japan. Journal of Volcanology and Geothermal Research 207, 113–129. Tsuya, H. 1955. Geological and petrological studies of volcano, Fuji, V.: 5. on the 1707 eruption of Volcano Fuji. Bulletin of the Earthquake Research Institute 33, 341–383. [less ▲]

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See detailTectonic, human and climate signal over the last 4000 years in the Lake Amik record (southern Turkey)
El Ouahabi, Meriam ULg; Hubert, Aurelia ULg; Vander Auwera, Jacqueline ULg et al

Poster (2017, April)

This study investigates the upper sediments infilling the central part of the Amik Basin in Southern Turkey. The Amik Basin is located in a tectonically active area: it is crossed by the Dead Sea Fault, a ... [more ▼]

This study investigates the upper sediments infilling the central part of the Amik Basin in Southern Turkey. The Amik Basin is located in a tectonically active area: it is crossed by the Dead Sea Fault, a major neotectonic structure in the Middle East extending from the Red Sea in the South to the East Anatolian Fault Zone in the North. Continuous human occupation is attested since 6000-7000 BC in the Amik Basin. The study focuses on the sedimentary record of the Lake Amik occupying the central part of the Basin. Our objective is to constrain major paleo-environmental changes over the last 4000 years. The lake has been drained and progressively dried up since the mid-50s. The absence of water column during the summer season allows to collect lacustrine samples along a 5 meter depth trench with a sampling resolution of 1 to 2 cm. Diverse complementary methods were applied to characterize the sedimentary record: i.e. magnetic susceptibility, grain size, organic and inorganic matter by loss-of-ignition, mineralogy by X-ray diffraction and core scanner X-ray fluorescence (XRF) geochemistry. The age of the record is constrained combining radionuclide and radiocarbon datings. Structural disturbances observed in the lacustrine sediments record are linked with major historical earthquakes from the 6th to the 9th century AD due to the Hasipasa Fault rupture. In addition to the tectonic influence, the sedimentary record clearly shows two periods indicating strong soil erosion in the lake catchment: (1) the most recent erosion phase occurs over the Roman period to Present; (2) the oldest one would have occurred during the Late Bronze period. Such changes are most probably related to change in land use. In term of climate influences, the mineralogical and geochemical results allow to evidence variations in chemical weathering conditions in the watershed and lake water level fluctuations, respectively. The clay mineral assemblages attest for significant pedogenesis transformations, especially during the Islamic/Ottoman period. Based on XRF results, an increase in potassium is attributed to a lake development phase during a wet phase An overflow of the Orontes River would be responsible for clay deposition. By contrast, increased calcium and strontium rather correspond to a low lacustrine level and a drier period. The Bronze and Iron/Hellenistic periods are both characterized by low lake level with limited contribution from the watershed. To conclude, our multiproxy study of the Lake Amik allows to decipher between tectonic, human and climate influences over the last 4000 years. Further step would be to compare the Amik record with other regional archives to evidence local and regional events. [less ▲]

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See detailSoil erosion in relation to land use changes in the Amik Lake sediments near the Antioch antique city during the last 4kyr
El Ouahabi, Meriam ULg; Hubert, Aurelia ULg; Lebeau, Héléne et al

in The Holocene (2017)

The Amik Basin in the Eastern Mediterranean region occupied since 6000-7000 BC has sustained a highly variable anthropic pressure culminating during the Late Roman Period when the Antioch city reached its ... [more ▼]

The Amik Basin in the Eastern Mediterranean region occupied since 6000-7000 BC has sustained a highly variable anthropic pressure culminating during the Late Roman Period when the Antioch city reached its golden age. The present 6m long sedimentary record of the Amik Lake occupying the central part of the Basin constrains major paleo-environmental changes over the last 4000 years using a multi-proxy analyses (grain-size, magnetic susceptibility and XRF geochemistry). An age model is provided by combining short-lived radionuclides with radiocarbon dating. A lake/marsh prevailed during the last 4kyrs with a level increase at the beginning of the Roman Period possibly related to optimum climatic condition and water channelling. The Bronze/Iron Ages are characterized by a strong terrigenous input linked to deforestation, exploitation of mineral resources and the beginning of upland cultivation. The Bronze/Iron Age transition marked by the collapse of the Hittite Empire is clearly documented. Erosion continues during the Roman Period and nearly stopped during the Early Islamic Period in conjunction with a decreasing population and soil depletion on the calcareous highland. The soil-stripped limestone outcrops triggered an increase in CaO in the lake water, and a general decrease in ZrO2 released in the landscape that lasts until the present day. During the Islamic Period, pastoralism on the highland sustained continued soil erosion of the ophiolitic Amanus Mountains. The modern Period is characterized by a higher pressure particularly on the Amanus Mountains linked to deforestation, road construction, ore exploitation and the drying of the lake for agriculture practices. [less ▲]

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See detailPaleoenvironmental implications in the dried lake sediments (Amik Lake, Southern Turkey)
El Ouahabi, Meriam ULg; Hubert, Aurelia ULg; Vander Auwera, Jacqueline ULg et al

Poster (2016, July)

The Amik Basin in the Eastern Mediterranean region has been continuously inhabited since 6000 – 7000 BC. The study focuses on the sedimentary record of the Amik Lake located in the central part of the ... [more ▼]

The Amik Basin in the Eastern Mediterranean region has been continuously inhabited since 6000 – 7000 BC. The study focuses on the sedimentary record of the Amik Lake located in the central part of the basin. Our objective is to constrain major paleo-environmental changes in the area over the last 4000 years and to unravel possible human impacts on the sedimentation. A diverse array of complementary methods was applied on the 6 m long record. Mineralogical (XRD), and geochemical (XRF) analyses were performed. The age of the record is constrained combining radionuclide and radiocarbon dating. A high sedimentation rate of 0.12 cm/yr was inferred at the studied site. The 4000 years (since ~1800 BC) long record shows that significant fluctuations of the lake level and the riverine system inflow into the Amik Lake occurred. The Late Bronze lowstand led to punctual dryings of the lake at the end of the Bronze/Iron Age transition. At that time, the rivers yielded a large terrigenous input linked to strong soil erosion related mainly to deforestation and exploitation of mineral resources. During the Roman and later periods, upland soils were partly depleted and the riverine system completely transformed by channelization (anthropic) that led to a marshification of the Amik Basin [1]. Chemical and mineralogical composition of sediments is quite diversified reflecting the significant geological variation of drainage basins. Periods with strong aggradation linked to major increase in erosion were identified and characterized by high amount of Cr, Ni and Zr. Levels relatively rich in fluorite, richterite, enstatite, hornblende and chrysotile are a result of the erosion of the ophiolitic rocks from the surrounding Amanos Mountains. These levels are interpreted as periods of relatively high physical erosion, while more humid periods led to more intensive weathering. Consequently, the dominance of kaolinite, muscovite/illite and talc indicates a climate with contrasting seasons. During the most recent period a marked increase in terrigenous minerals associated with a rise in dolomite indicates ungoing erosion as well as the drying-out of the lake. [1] T.J. Wilkinson, L. Rayne, Water History, 2, 115-144 (2010). [less ▲]

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See detailThe last millenia sedimentary record of Lago Esponja from Northern Chilean Patagonia
Fagel, Nathalie ULg; Alvarez, Denisse; Araneda, Alberto et al

Poster (2016, April 20)

We evaluate the climate and environmental variability of Northern Chilean Patagonia during the Last Millennia, using a multi-proxy analysis of a sediment core from Lago Esponja (45°09’S, 72°08’W). The ... [more ▼]

We evaluate the climate and environmental variability of Northern Chilean Patagonia during the Last Millennia, using a multi-proxy analysis of a sediment core from Lago Esponja (45°09’S, 72°08’W). The lake is located in the region of Aysen del General Carlos Ibanez del Campo, in NW Patagonia. The study focuses on a multiproxy analysis of sedimentary records. The longest core (150 cm long) was collected in 2014 at 40 m depth. The sediment, which is composed of light brown organic-rich clayey silt, was analyzed for sedimentology (grain size, magnetic susceptibility organic matter and biogenic silica content), mineralogy (X-ray diffraction) and geochemistry (elemental and isotopic analyses of C and N, XRF core-scaner at 1 mm resolution). The radiocarbon ages, measured on 3 macro-remains, demonstrate that the core covers the last 6.700 years. The sedimentation rate ranges between 0.1 mm/yr in the lower section (100-150 cm) and 0.4 mm/yr in the upper meter. Visual descriptions and Scopix radiographies show that the sediment record is finely laminated except a massive decimetric coarser and darker layer corresponding to a tephra (estimated age 700AD±50). Magnetic susceptibility (confirmed by scopix radiographies) highlights the presence of 8 additional millimetric tephra layers. The biogenic silica content of the sediment is low (mean 5%). Diatom assemblage is dominated by benthic and acidophilous species, with high saprobic values. None marked changes were observed regarding the dynamic of the lake. The high organic matter content (mean 15%) and its high C/N ratio (12.7) throughout the core indicate inputs of allochtonous and terrestrial organic matter. Such parameters present high sediment variability also marked by changes in the chemical composition. The laminations reflect changes in the allochtonous sedimentary inputs, with high terrestrial inputs during wetter conditions in relation with the Westerlies. The sedimentary records of Lago Esponja will be compared with Eastern lacustrine record from the same latitude in order to confirm the climate-driven record. [less ▲]

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See detailChemical and mineralogical proxies of erosion episodes in the dried lake sediments (Amik Lake, Southern Turkey): paleoenvironmental implications
El Ouahabi, Meriam ULg; Hubert, Aurelia ULg; Lebeau, Héléne et al

Poster (2016, April 17)

The Amik Basin in the Eastern Mediterranean region has been continuously occupied since 6000-7000 BC. The landscape has sustained with highly variable anthropic pressure culminating during the Late Roman ... [more ▼]

The Amik Basin in the Eastern Mediterranean region has been continuously occupied since 6000-7000 BC. The landscape has sustained with highly variable anthropic pressure culminating during the Late Roman Period when the Antioch city reached its golden age. The basin also sustained a high seismic activity (M≥7) as it is a releasing step-over along the Dead Sea Fault. The study focuses on the sedimentary record of the Amik Lake occupying the central part of the Basin. Our objective is to constrain major paleo-environmental changes in the area over the last 4000 years and to unravel possible human impacts on the sedimentation. A diverse array of complementary methods was applied on the 6 m long record. High resolution of mineralogical (XRD) and geochemical (XRF) analyses were performed. Quantitative mineralogical phases of sediments by the Rietveld method were computed using Topaz software. The age of the record is constrained combining radionuclide and radiocarbon dating, and checked using the correlation between the earthquake history and rapidly deposited layer identified. A high sedimentation rate of 0.12 cm/yr was inferred at the coring site. The 4000 years old record shows that significant fluctuations of the lake level and the riverine system inflow into the Amik Lake occurred. The Late Bronze lowstand leaded to punctual dryings of the lake at the end of the Bronze/Iron transition marked by the collapse of the Hittite Empire and during the Dark ages. At that time, the riverine was carrying a large terrigenous input linked to strong soil erosion related to deforestation, exploitation of mineral resources and the beginning of upland cultivation. During the Roman Period and in the later periods, upland soils were partly depleted and the riverine system completely transformed by channelization that leaded to a mashification of the Amik Basin. Chemical and mineralogical composition of sediments is quite diversified reflecting the significant geological variation of drainage basins. Abundant calcareous minerals, especially calcite, aragonite, dolomite and small amount of wollastonite characterize the different sedimentary levels recorded in the lake. Levels relatively rich in fluorite, richerite, enstatite, and wollastonite are a result of the erosion of the ophiolitic rocks from the surrounding Amanos Mountains. These levels are interpreted as corresponding to relatively high erosive periods, while more humid periods lead to more intensive weathering and consequently to the dominance of kaolinite, muscovite/illite and talc more advanced in the relative stability scale, indicating a climate with contrasting seasons. During the most recent Period a marked increase in terrigeneous minerals associated with a rise in dolomite indicates ungoing erosion as well as the drying-out of the lake. [less ▲]

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See detailEarthquake imprints on a lacustrine deltaic system: the Kürk Delta along the East Anatolian Fault (Turkey)
Hubert, Aurelia ULg; El Ouahabi, Meriam ULg; Garcia-Moreno, David et al

in Sedimentology (2016)

Deltas contain sedimentary records that are not only indicative of water level changes, but also particularly sensitive to earthquake shaking typically resulting in soft-sediment-deformation structures ... [more ▼]

Deltas contain sedimentary records that are not only indicative of water level changes, but also particularly sensitive to earthquake shaking typically resulting in soft-sediment-deformation structures. The Kürk lacustrine delta lies at the south-western extremity of Lake Hazar in eastern Turkey and is adjacent to the seismogenic East Anatolian Fault (EAF), which has generated earthquakes of magnitude 7. In this paper we have reevaluated water level changes and earthquake shaking that have affected the Kürk Delta combining geophysical data (seismic-reflection profiles and side-scan sonar), remote sensing images, historical data, onland outcrops and offshore coring. The history of water level changes provides a temporal framework for the depositional record. In addition to the commonly soft-sediment-deformation documented previously, onland outcrops reveal a record of deformation (fracturing, tilt and clastic dykes) linked to large earthquake-induced liquefactions and lateral spreading. The recurrent liquefaction structures can be used to obtain a paleoseismological record. Five event horizons were identified that could be linked to historical earthquakes occurring in the last 1000 years along the EAF. Sedimentary cores sampling the most recent subaqueous sedimentation revealed the occurrence of another type of earthquake indicator. Based on radionuclide dating (137Cs and 210Pb), two major sedimentary events were attributed to the 1874-1875 EAF earthquake sequence. Their sedimentological characteristics were determined by X-ray imagery, XRD, LOI, grain-size distribution and geophysical measurements. The events are interpreted to be hyperpycnal deposits linked to post-seismic sediment reworking of earthquake-triggered landslides. [less ▲]

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See detailSubmarine Paleo-earthquake record of the Cinarcik segment of the North Anatolian Fault in the Marmara Sea (Turkey)
Drab, Laureen; Hubert, Aurelia ULg; Schmidt, Sabine et al

in Bulletin Seismological Society of America (2015), 105

The submarine part of the North Anatolian Fault (NAF) in the Marmara Sea is a significant hazard for the city of Istanbul (Turkey). The use of paleoseismological data to provide an accurate seismic risk ... [more ▼]

The submarine part of the North Anatolian Fault (NAF) in the Marmara Sea is a significant hazard for the city of Istanbul (Turkey). The use of paleoseismological data to provide an accurate seismic risk assessment for the area is constrained by the fact that the NAF system is submarine near Istanbul; thus a history of paleoearthquakes can be inferred only by using sediment cores. Here a record of turbidites was obtained in two cores and used to reconstruct the earthquake history along a main branch of the NAF, the Cinarcik Segment. Kullenberg core Klg04 (4 m long) was collected during Marmarascarps mission from a berm north of the fault and a second core (Klg03, 3.5 m long) was positioned in the Cinarcik Basin, 3 km south of the fault. Sedimentary sequences in the two cores were correlated using variations in Ca/Ti ratio, which reflect the local aquatic productivity compared with more terrigenous input. The turbidites between the two cores were then classified to distinguish the synchronous ones from the other ones. Radionuclide measurements suggest that the most recent turbidite recorded in both cores was triggered by the M=7.3 1894 earthquake. We conclude that the turbidites are earthquake-generated, based on: 1) their distinctive sedimentological and geochemical signatures, previously described and applied in the Marmara Sea; 2) the correlation of turbidites between cores at berm and basin sites; 3) the match of the most recent turbidites with a 19th century historical earthquake; and 4) the elimination of others processes. Because of its specific geomorphological location, core Klg04 likely records only mass wasting events related to the rupture on the Cinarcik Segment. To date older turbidites, we used 14C and paleomagnetic data to build an OxCal age model with a local reservoir correction (ΔR) of 400±50 yr. The Cinarcik Segment is found to have ruptured in AD1894, AD1509, sometime in the 14th century, AD989, AD740 and in the 5th century and have a mean recurrence interval of rupture between 243 and 396 years. Following the age model obtained we finally used the earthquake record history of the Cinarcik Segment to infer the rupture history of adjacent segments of the North Anatolian Fault during six earthquake cycles over the past 1500 years. [less ▲]

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See detailSeismically-triggered organic-rich layers in recent sediments from lake Gollukoy (North Anatolian Fault, Turkey
Avşar, Ulaş; Hubert, Aurelia ULg; De Batist, Marc et al

in Quaternary Science Reviews (2014), 103

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See detailThe earthquake sedimentary record in the the Sea of Marmara, Turkey
Hubert, Aurelia ULg; Drab, Loreen; Schmidt, Sabine et al

Conference (2012, October)

The submarine part of the North Anatolian Fault (NAF) is a very significant hazard for the 12 million people living in Istanbul (Turkey). An accurate seismic risk assessment necessitates ... [more ▼]

The submarine part of the North Anatolian Fault (NAF) is a very significant hazard for the 12 million people living in Istanbul (Turkey). An accurate seismic risk assessment necessitates paleoseismological data, which can be retrieved in the Marmara Sea by using sedimentary cores. We present here a record of turbidites obtained in cores spanning the Tekirdag ̆ Basin, the Western High, the Central Basin, and the Cinarcik Basin. In the Tekirdag and Western High the turbidites are synchronous pointing to shaking by earthquakes as a triggering mechanism. Generally seismoturbidites in the Marmara Sea are distinguished from other turbidites based in their large extension, their particular granulometric and their particular geochemical characteristics. The 210Pb and 137Cs radionucleides measurements have also shown that the M=7.4 1912 Mürefte earthquake and the M=7.3 1894 Prince's Island earthquake have left a distinctive sedimentary imprint at the top of the studied cores. The chronology of other seismoturbidites is built combining radiocarbon dating and secular variation patterns of paleo-declination and paleo-inclination. Finally the obtained record is compared to the historical seismicity record. [less ▲]

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See detailLast millenium environmental changes in Lake Bertrand sediments, Chilean Patagonia
Sacré, Vincent ULg; Fagel, Nathalie ULg; Schmidt, Sabine et al

Poster (2012, April 23)

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See detailThe earthquake sedimentary record in marine sediment from cores in the western part of the Marmara Sea, Turkey
Drab, Laureen; Hubert, Aurelia ULg; Schmidt, Sabine et al

Conference (2012, April)

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See detailThe earthquake sedimentary record in the Western part of the Sea of Marmara, Turkey
Drab, Laureen; Hubert, Aurelia ULg; Schmidt, Sabine et al

in Natural Hazards & Earth System Sciences (2012)

The submarine part of the North Anatolian Fault (NAF) is a very significant hazard for the 12 million people living in Istanbul (Turkey). An accurate seismic risk assess- ment necessitates ... [more ▼]

The submarine part of the North Anatolian Fault (NAF) is a very significant hazard for the 12 million people living in Istanbul (Turkey). An accurate seismic risk assess- ment necessitates paleoseismological data, which can be re- trieved in the Sea of Marmara only using sedimentary cores. Here a record of turbidites was obtained in five cores span- ning the Tekirdag ̆ Basin, the Western High and the Central Basin linked by the Tekirdag ̆ Fault Segment. The turbidites are synchronous at different sites across basins and structural highs. The only possible triggering mechanism is thus shak- ing related to major earthquakes. In particular the M=7.4 1912 Mu ̈refte earthquake has let a distinctive sedimentary imprint in all the studied cores. Radiocarbon dating implies a turbidite recurrence interval of about 300 years. In addi- tion the low number of turbidites documented in the Central Basinsuggestsquasi-synchronousrupturesoftheTekirdag ̆ Segment and the adjacent Central Segment of the NAF or a partial seismic slip on the Central Segment. Both scenarii have implications regarding seismic hazard. Finally through we obtained a reliable paleoseismological record of the rup- tures along the Tekirdag ̆ Segment, further chronological con- straints are needed to accurately date the events and correlate them with known historical earthquakes. [less ▲]

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See detailTurbiditic sedimentary record in the different basins of the Sea of Marmara
Hubert, Aurelia ULg; Drab, Laureen; Schmidt, Sabine et al

Conference (2011, June 13)

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See detailParticulate carbon export during a bloom of Emiliania huxleyi in the Northwest European continental margin (northern Bay of Biscay)
Schmidt, Sabine; Harlay, Jérôme ULg; Borges, Alberto ULg et al

Poster (2011, April 03)

Coccolithophores, the dominant pelagic calcifiers in the oceans, play a key role in the marine carbon cycle through calcification, primary production and carbon export, the main drivers of the biological ... [more ▼]

Coccolithophores, the dominant pelagic calcifiers in the oceans, play a key role in the marine carbon cycle through calcification, primary production and carbon export, the main drivers of the biological CO2 pump. Massive blooms of Emiliania huxleyi are observed each year at the continental margin of the Bay of Biscay. The BG02/11 cruise (RV Belgica), supported by near-real time remote sensing data, was conducted in early May 2002, along a transect on the outer shelf of the Northern Bay of Biscay between the La Chapelle Bank (southern region of the transect) and Goban Spur (northern region of the transect) (47.0°-50.5°N, 5.0°-11.0°W). Biogeochemical variables including primary production, calcification, partial pressure of CO2 (pCO2), chlorophyll-a (Chl-a), particle load, particulate organic and inorganic carbon (POC, PIC), Th-234 were measured in surface waters to assess particle dynamics, and carbon export in relation to the development of a coccolithophore bloom. We observed a marked northward decrease in water irradiance, Chl-a concentration and calcification rates: the bloom exhibited lower values and may have been less well developed in the Goban Spur area. There was also a large northward decrease in particulate 234Th settling fluxes along the transect from La Chapelle Bank to Goban Spur. The export fluxes of POC and PIC from the top 80 m, determined using the ratios of POC and PIC to Th-234 of particles, ranged from 81 to 323 mgC m-2 d-1 and from 30 to 128 mgC m-2 d-1, respectively. The highest fluxes were observed in waters presenting a well-developed coccolithophore bloom, as shown by high reflectance of surface waters. Despite the high calcification rates at the southernmost stations, surface waters were a net sink of atmospheric CO2 during this cruise. These results tend to demonstrate the enhancement of coccolithophore blooms on the efficiency of the surface community to export carbon to deep ocean. However, improvements in the estimation of POC and PIC export during coccolithophore blooms are needed to not only understand the present calcification to primary production (C:P) ratio, but also to help understand future sequestration of organic and inorganic carbon to the deep ocean. [less ▲]

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See detailBenthic remineralization in the northwest European continental margin (northern Bay of Biscay)
Suykens, Kim; Schmidt, Sabine; Delille, Bruno ULg et al

in Continental Shelf Research (2011), 31

We report a dataset of sediment characteristics and biogeochemical fluxes at the watersediment interface at the northwest European continental margin (northern Bay of Biscay). Cores were obtained in June ... [more ▼]

We report a dataset of sediment characteristics and biogeochemical fluxes at the watersediment interface at the northwest European continental margin (northern Bay of Biscay). Cores were obtained in June 2006, May 2007 and 2008, at 18 stations on the shelf break (120 to 180 m), and at 2 stations on the continental slope (520 m and 680 m). Water-sediment fluxes of dissolved oxygen (O2), total alkalinity (TA), nitrate (NO3-), and dissolved silicate (DSi) were measured at a total of 20 stations. Sediment characteristics include: grain size, chlorophyll-a (Chl-a) and phaeopigment (Phaeo) content, particulate organic (POC) and inorganic (PIC) carbon content, and lead-210 (210Pb) and thorium-234 (234Th) activities. Sediments were sandy (fine to coarse) with organic matter (OM) (1.0 - 4.0 %) and Chl-a (0.01 - 0.95 μg g-1) contents comparable to previous investigations in the same region, and a relatively high PIC fraction (0.8 - 10.2 %). Water-sediment O2 fluxes (-2.4 to -8.4 mmol O2 m-2 d-1) were low compared to other coastal environments and correlated well with OM and Chl-a content. 234Th activity profiles indicated that Chl-a sediment content was mainly controlled by physical mixing processes related to local hydrodynamics. The correlation between water-sediment fluxes of O2 and NO3- indicated a close coupling of nitrification/denitrification and total benthic organic carbon degradation. Dissolution of biogenic silica (0.05 to 0.95 mmol m-2 d-1) seemed uncoupled from organic carbon degradation, as characterized by water-sediment O2 fluxes. The link between water-sediment fluxes of TA and O2 indicated the occurrence of metabolic driven dissolution of calcium carbonates (CaCO3) in the sediments (~ 0.33 ± 0.47 mmol m-2 d-1) which represented ~ 1 % of the pelagic calcification rates due to coccolithophores measured during the cruises. These CaCO3 dissolution rates were below those reported in sediments of continental slopes and of the deep ocean, probably due to the high over-saturation with respect to CaCO3 of the water column overlying the continental shelf sediments of the northern Bay of Biscay. Rates of total benthic organic carbon degradation were low compared to water column rates of primary production and aphotic community respiration obtained during the cruises. [less ▲]

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See detailSedimentological fingerprints of paleoseimic activity revealed from lake sediments: a case study from the North Anatolian Fault (NAF), Turkey
Avsar, Ulas; Hubert, Aurelia ULg; Fagel, Nathalie ULg et al

in Abstracts with Programs - Geological Society of America (2010, October)

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