All ICDP Publications with Abstracts
From parent-sysfolder "Publications" + 2 folder-levels deep
1394.
DeepCHALLA: Two glacial cycles of climate and ecosystem dynamics from equatorial East Africa
Scientific Drilling
(15)
72-76
2013
ISSN: 181689571393.
Destructive and non-destructive density determination: Method comparison and evaluation from the Laguna Potrok Aike sedimentary record
Quaternary Science Reviews,
71147 – 153
2013
Keywords:▾
Argentina; Laguna Potrok Aike; Santa Cruz [Argentina]; Vitaceae; Density measurement (specific gravity); Fruits; Gamma rays; Scanning; Sedimentology; Sediments; Bulk density measurement; Continental scientific drillings; CT-scan; Density variabilities; High signal-to-noise ratio; ICDP-project PASADO; Sediment densities; XRF; bulk density; cost-benefit analysis; measurement method; resolution; sampling; sediment core; signal-to-noise ratio; X-ray fluorescence; Computerized tomography
Abstract: ▾ Density measurements play a central role in the characterization of sediment profiles. When working with long records (>100m), such as those routinely obtained within the frame of the International Continental Scientific Drilling Program, several methods can be used, all of them varying in resolution, time-cost efficiency and source of errors within the measurements. This paper compares two relatively new non-destructive densitometric methods, CT-Scanning and the coherent/incoherent ratio from an Itrax XRF core Scanner, to data acquired from a Multi-sensor core logger Gamma Ray Attenuation Porosity Evaluator (MSCL Grape) and discrete measurements of dry bulk density, wet bulk density and water content. Quality assessment of density measurements is performed at low and high resolution along the Laguna Potrok Aike (LPA) composite sequence. Giving its resolution (0.4mm in our study), its high signal to noise ratio, we conclude that CT-Scan provides a precise, fast and cost-efficient way to determine density variation of long sedimentary record. Although more noisy that the CT-Scan measurements, coherent/incoherent ratio from the XRF core scanner also provides a high-resolution, reliable continuous measure of density variability of the sediment profile. The MSCL Grape density measurements provide actual density data and have the significant advantage to be completely non-destructive since the acquisition is performed on full cores prior to opening. However, the quality MSCL Grape density measurements can potentially be reduced by the presence of voids within the sediment core tubes and the dry and bulk density measurements suffers from sampling challenges and are time-consuming. © 2012 Elsevier Ltd.
1392.
Detailed insight into Arctic climatic variability during MIS 11c at Lake El'gygytgyn, NE Russia
Climate of the Past,
9
(4)
1467-1479
2013
ISSN: 18149324Keywords:▾
climate modeling; climate variation; ice core; ice cover; interglacial; isotopic analysis; lake evolution, Chukchi; Elgygytgyn Lake; Russian Federation
Abstract: ▾ Here we present a detailed multi-proxy record of the climate and environmental evolution at Lake El'gygytgyn, Far East Russian Arctic during the period 430-395 ka covering the marine isotope stage (MIS) 12/11 transition and the thermal maximum of super interglacial MIS 11c. The MIS 12/11 transition at Lake El'gygytgyn is characterized by initial warming followed by a cold reversal implying similarities to the last deglaciation. The thermal maximum of MIS 11c is characterized by full and remarkably stable interglacial conditions with mean temperatures of the warmest month (MTWM) ranging between ca. 10-15 C; annual precipitation (PANN) ranging between ca. 300-600 mm; strong in-lake productivity coinciding with dark coniferous forests in the catchment; annual disintegration of the lake ice cover; and full mixis of the water column. Such conditions persisted, according to our age model, for ca. 27 ± 8 kyr between ca. 425-398 ka. The Lake El'gygytgyn record closely resembles the climate pattern recorded in Lake Baikal (SE Siberia) sediments and Antarctic ice cores, implying interhemispheric climate connectivity during MIS 11c. © 2013. CC Attribution 3.0 License.
1391.
Diversity and distribution of taxa in the genus Eunotia Ehrenberg (Bacillariophyta) in Macedonia
Phytotaxa,
86
(1)
1 – 117
2013
ISSN: 11793163Abstract: ▾ Within the past few decades Eunotia (Bacillariophyceae) has been confirmed as one of the most species rich diatom genera. The remarkable diversity of this genus has been well documented for the tropical region of South America, and its wide distribution comprehensively demonstrated for North America and Canada, Europe, East and Southeast Asia, as well as the Subantarctic region. Till present day only twenty eight taxa of Eunotia have been reported for Macedonia, mainly from the various aquatic habitats of different mountains. The main focus of the present study is the diversity, taxonomy and general distribution of taxa belonging to Eunotia in Macedonian mountain regions. The area investigated covers most of the mountains in the western, south-western, southern, central and eastern part. In total 53 taxa have been observed, among which six are described as new species (Eunotia atomus, E. fabaeformis, E. mariovensis, E. pseudominor, E. scardica and E. stojanovskii). The morphological features, as observed by light microscopy (LM), are comprehensively described for each taxon. The ultrastructure of the valve, as observed by scanning electron microscopy (SEM), is additionally described for most of the taxa. The general distributional pattern, locality, altitude and substrate preference, for every taxon is also included. The distinctive characters between similar taxa are discussed and taxonomical notes are as well provided. © 2013 Magnolia Press.
1390.
Chronology of Lake El’gygytgyn sediments – A combined magnetostratigraphic, palaeoclimatic and orbital tuning study based on multi-parameter analyses
Climate of the Past,
9
(6)
2413-2432
2013
ISSN: 18149324
Publisher: Copernicus GmbH
Abstract: ▾ A 318-metre-long sedimentary profile drilled by the International Continental Scientific Drilling Program (ICDP) at Site 5011-1 in Lake El’gygytgyn, Far East Russian Arctic, has been analysed for its sedimentologic response to global climate modes by chronostratigraphic methods. The 12 km wide lake is sited off-centre in an 18 km large crater that was created by the impact of a meteorite 3.58 Ma ago. Since then sediments have been continuously deposited. For establishing their chronology, major reversals of the earth’s magnetic field provided initial tie points for the age model, confirming that the impact occurred in the earliest geomagnetic Gauss chron. Various stratigraphic parameters, reflecting redox conditions at the lake floor and climatic conditions in the catchment were tuned synchronously to Northern Hemisphere insolation variations and the marine oxygen isotope stack, respectively. Thus, a robust age model comprising more than 600 tie points could be defined. It could be shown that deposition of sediments in Lake El’gygytgyn occurred in concert with global climatic cycles. The upper ∼ 160 m of sediments represent the past 3.3 Ma, equivalent to sedimentation rates of 4 to 5 cm ka−1, whereas the lower 160 m represent just the first 0.3 Ma after the impact, equivalent to sedimentation rates in the order of 45 cm ka−1. This study also provides orbitally tuned ages for a total of 8 tephras deposited in Lake El’gygytgyn. © Author(s) 2013.
1389.
Characterisation and isotopic evolution of saline waters of the Outokumpu Deep Drill Hole, Finland - Implications for water origin and deep terrestrial biosphere
Applied Geochemistry,
3237 – 51
2013
1388.
Dynamic diatom response to changing climate 0–1.2 Ma at Lake El'gygytgyn, Far East Russian Arctic
Climate of the Past,
9
(3)
1309-1319
2013
1387.
A pollen-based biome reconstruction over the last 3.562 million years in the Far East Russian Arctic – new insights into climate–vegetation relationships at the regional scale
Climate of the Past,
9
(6)
2759-2775
2013
1386.
Microsedimentological characterization using image analysis and μ-XRF as indicators of sedimentary processes and climate changes during Lateglacial at Laguna Potrok Aike, Santa Cruz, Argentina
Quaternary Science Reviews,
71191 – 204
2013
1385.
7.10 Chemical Characteristics of Sediments and Seawater
Reading the Archive of Earth’s Oxygenation: Volume 3: Global Events and the Fennoscandian Arctic Russia-Drilling Early Earth Project
1457--1514
2013
1384.
A 350 ka record of climate change from Lake El'gygytgyn, Far East Russian Arctic: refining the pattern of climate modes by means of cluster analysis
Climate of the Past,
9
(4)
1559-1569
2013
ISSN: 18149324Keywords:▾
climate change; climate modeling; cluster analysis; hierarchical system; oxygen isotope; sediment core; statistical analysis, Arctic Ocean; Chukchi; Elgygytgyn Lake; Far East; Russian Federation
Abstract: ▾ Rock magnetic, biochemical and inorganic records of the sediment cores PG1351 and Lz1024 from Lake El'gygytgyn, Chukotka peninsula, Far East Russian Arctic, were subject to a hierarchical agglomerative cluster analysis in order to refine and extend the pattern of climate modes as defined by Melles et al. (2007). Cluster analysis of the data obtained from both cores yielded similar results, differentiating clearly between the four climate modes warm, peak warm, cold and dry, and cold and moist. In addition, two transitional phases were identified, representing the early stages of a cold phase and slightly colder conditions during a warm phase. The statistical approach can thus be used to resolve gradual changes in the sedimentary units as an indicator of available oxygen in the hypolimnion in greater detail. Based upon cluster analyses on core Lz1024, the published succession of climate modes in core PG1351, covering the last 250 ka, was modified and extended back to 350 ka. Comparison to the marine oxygen isotope (δ18O) stack LR04 (Lisiecki and Raymo, 2005) and the summer insolation at 67.5 °N, with the extended Lake El'gygytgyn parameter records of magnetic susceptibility (κLF), total organic carbon content (TOC) and the chemical index of alteration (CIA; Minyuk et al., 2007), revealed that all stages back to marine isotope stage (MIS) 10 and most of the substages are clearly reflected in the pattern derived from the cluster analysis. © Author(s) 2013.
1383.
A biomarker record of Lake El'gygytgyn, Far East Russian arctic: Investigating sources of organic matter and carbon cycling during marine isotope stages 1-3
Climate of the Past,
9
(1)
243-260
2013
ISSN: 18149324Keywords:▾
anoxic conditions; biomarker; carbon cycle; carbon isotope; climate change; glaciation; isotopic analysis; isotopic composition; lacustrine deposit; Last Glacial Maximum; marine environment; organic carbon; organic matter; paleoenvironment; sediment chemistry; water column, Chukchi; Elgygytgyn Lake; Russian Federation
Abstract: ▾ Arctic paleoenvironmental archives serve as sensitive recorders of past climate change. Lake El'gygytgyn (Far East Russian Arctic) is a high-latitude crater impact lake that contains a continuous sediment record influenced by neither glaciation nor glacial erosion since the time of impact 3.58 Ma ago. Prior research on sediments collected from Lake El'gygytgyn suggest times of permanent ice cover and anoxia corresponding to global glacial intervals, during which the sediments are laminated and are characterized by the co-occurrence of high total organic carbon, microscopic magnetite grains that show etching and dissolution, and negative excursions in bulk sediment organic matter carbon isotope (δ13C) values. Here we investigate the abundance and carbon isotopic composition of lipid biomarkers recovered from Lake El'gygytgyn sediments spanning marine isotope stages 1-3 to identify key sources of organic matter (OM) to lake sediments, to establish which OM sources drive the negative δ13C excursion exhibited by bulk sediment OM, and to explore if there are molecular and isotopic signatures of anoxia in the lake during glaciation. We find that during marine isotope stages 1-3, direct evidence for water column anoxia is lacking. A ∼4‰ negative excursion in bulk sediment δ13C values during the Local Last Glacial Maximum (LLGM) is accompanied by more protracted, higher magnitude negative excursions in n-alkanoic acid and n-alkanol δ13C values that begin 20 kyr in advance of the LLGM. In contrast, n-alkanes and the C30 n-alkanoic acid do not exhibit a negative δ13C excursion at this time. Our results indicate that the C24, C26 and C28 n-alkanoic acids do not derive entirely from terrestrial OM sources, while the C30 n-alkanoic acid at Lake El'gygytgyn is a robust indicator of terrestrial OM contributions. Overall, our results strongly support the presence of a nutrient-poor water column, which is mostly isolated from atmospheric carbon dioxide during glaciation at Lake El'gygytgyn. © 2013 Author(s).
1382.
A biomarker record of Lake El'gygytgyn, Far East Russian Arctic: investigating sources of organic matter and carbon cycling during marine isotope stages 1–3
Climate of the Past,
9
(1)
243-260
2013
1381.
A biomarker study of depositional paleoenvironments and source inputs for the massive formation of Upper Cretaceous lacustrine source rocks in the Songliao Basin, China
Palaeogeography, Palaeoclimatology, Palaeoecology,
385137-151
2013
ISSN: 00310182Keywords:▾
biomarker; carbon isotope; core analysis; Cretaceous; depositional environment; isotopic fractionation; kerogen; lacustrine deposit; lacustrine environment; organic matter; paleoenvironment; source rock; water column, China; Nen Basin; Songliao Basin, algae; Bacteria (microorganisms); Embryophyta
Abstract: ▾ The abundance and composition of total organic carbon, aliphatic and aromatic hydrocarbons including biomarkers, and the δ13C composition of total organic matter and individual compounds in core samples of the Nenjiang Formation from the SK-1 borehole of the Songliao Basin provide information on the paleoenvironmental conditions of lacustrine sediments formed during the Upper Cretaceous. The distribution of n-alkanes, and their δ13C composition, and 4-methylsteranes and dinosteranes in the first member of the Nenjiang Formation (K2n1) indicate that the organic matter largely originated from algal organisms and is dominated by types I and II kerogen. The occurrence of gammacerane, aryl isoprenoids isorenieratane and low pristane/phytane and diasterane/sterane ratios further suggest a salinity stratified water column associated with anoxic bottom waters, as well as possible photic zone oxygen depletion conditions during major source rock deposition of the K2n1. The organic geochemical data also indicate significantly different depositional environments for the second member of the Nenjiang Formation (K2n2) sediments, which are interpreted to have been deposited under a uniform salinity (non-stratified) oxic water column. Consequently, although the organic matter in the K2n2 sediments was largely derived from algal and bacterial sources, the kerogen types are dominantly IIb and III due to the oxidative degradation of organic matter, combined with a gradual increase in land-plant input. Furthermore, the occurrence and shift of two saw-toothed distribution patterns of the δ13C composition of C29 to C33 n-alkanes, with "W" and "M" patterns being isotopically heavy odd- and even-numbered alkanes, respectively, is suggestive of organic input shift or an unknown mechanism of carbon uptake or isotopic fractionation. In particular, the heavy even carbon numbered high molecular weight n-alkanes is rare and needs further investigation. © 2012 Elsevier B.V.
1380.
A late glacial to holocene record of environmental change from Lake Dojran (Macedonia, Greece)
Climate of the Past,
9
(1)
481 – 498
2013
1379.
A plan for a 5 km-deep borehole at Reykjanes, Iceland, into the root zone of a black smoker on land
Scientific Drilling
(16)
73-79
2013
ISSN: 18168957Keywords:▾
Contingency planning; Current production; Deep boreholes; Deep drilling; Iceland deep drilling projects; Scientific activity; Superheated steam; Technical aspects, Drilling fluids; Effluent treatment; Geothermal fields; Supercritical fluids, Boring
Abstract: ▾ A summary workshop report describing the progress made so far by the Iceland Deep Drilling Project (IDDP) is presented below. The report provides recommendations concerning technical aspects related to deep drilling, and invites international participation in both the engineering and the scientific activities of the next phase of the IDDP. No issues were identified at the workshop that should rule out attempting the drilling, sampling and testing of the proposed IDDP-2 well. Although technically challenging, the consensus of the workshop was that the drilling of such a hot deep well, and producing potentially hostile fluids, is possible but requires careful contingency planning. The future well will be explored for supercritical fluid and/or superheated steam beneath the current production zone of the Reykjanes geothermal field in SW Iceland. This deep borehole will provide the first opportunity worldwide to directly investigate the root zone of a magma-hydrothermal system which is likely to be similar to those beneath the black smokers on the worldencircling mid-ocean rift systems. © Author(s) 2013.
1378.
A pollen-based biome reconstruction over the last 3.562 million years in the Far East Russian Arctic – New insights into climate– vegetation relationships at the regional scale
Climate of the Past,
9
(6)
2759-2775
2013
ISSN: 18149324Keywords:▾
biome; climate variation; cold tolerance; deciduous forest; drought stress; fossil assemblage; Holocene; interglacial; palynology; Pliocene; reconstruction; vegetation history, Arctic; Chukchi; Elgygytgyn Lake; Russian Far East; Russian Federation
Abstract: ▾ The recent and fossil pollen data obtained under the frame of the multi-disciplinary international El'gygytgyn Drilling Project represent a unique archive, which allows the testing of a range of pollen-based reconstruction approaches and the deciphering of changes in the regional vegetation and climate. In the current study we provide details of the biome reconstruction method applied to the late Pliocene and Quaternary pollen records from Lake El'gygytgyn. All terrestrial pollen taxa identified in the spectra from Lake El'gygytgyn were assigned to major vegetation types (biomes), which today occur near the lake and in the broader region of eastern and northern Asia and, thus, could be potentially present in this region during the past. When applied to the pollen spectra from the middle Pleistocene to present, the method suggests (1) a predominance of tundra during the Holocene, (2) a short interval during the marine isotope stage (MIS) 5.5 interglacial distinguished by cold deciduous forest, and (3) long phases of taiga dominance during MIS 31 and, particularly, MIS 11.3. These two latter interglacials seem to be some of the longest and warmest intervals in the study region within the past million years. During the late Pliocene-early Pleistocene interval (i.e., ∼3.562-2.200 Ma), there is good correspondence between the millennial-scale vegetation changes documented in the Lake El'gygytgyn record and the alternation of cold and warm marine isotope stages, which reflect changes in the global ice volume and sea level. The biome reconstruction demonstrates changes in the regional vegetation from generally warmer/wetter environments of the earlier (i.e., Pliocene) interval towards colder/drier environments of the Pleistocene. The reconstruction indicates that the taxon-rich cool mixed and cool conifer forest biomes are mostly characteristic of the time prior to MIS G16, whereas the tundra biome becomes a prominent feature starting from MIS G6. These results consistently indicate that the study region supported significant tree populations during most of the interval prior to ∼2.730 Ma. The cold- and drought-tolerant steppe biome first appears in the reconstruction ∼3.298 Ma during the tundra-dominated MIS M2, whereas the tundra biome initially occurs between ∼3.379 and ∼3.378 Ma within MIS MG4. Prior to ∼2.800 Ma, several other cold stages during this generally warm Pliocene interval were characterized by the tundra biome. © Author(s) 2013. CC Attribution 3.0 License.
1377.
Age models for long lacustrine sediment records using multiple dating approaches - An example from Lake Bosumtwi, Ghana
Quaternary Geochronology,
1547 – 60
2013
ISSN: 18711014Keywords:▾
Ashanti; Ghana; Lake Bosumtwi; Bayesian analysis; chronology; climate variation; lacustrine deposit; paleoclimate; paleomagnetism; radiocarbon dating; sedimentary sequence; sedimentation; time series; uranium series dating
Abstract: ▾ The continuous 300-m long drill cores obtained from Lake Bosumtwi, Ghana represent one of the longest, continuous lacustrine sequences obtained from an extant lake, and contain an unprecedented record of late Quaternary climate change in West Africa. However, one of the main challenges associated with generating long paleoclimate time series from terrestrial records such as this is the development of accurate age-depth relationships because unlike marine records, lacustrine sequences cannot be tuned to global ice volume records via δ18O stratigraphy. The Lake Bosumtwi record thus offers an excellent case study for examining the potential and the challenges associated with different geochronological techniques in lacustrine systems. In the present study, we use a combination of radiocarbon, optically stimulated luminescence and U-series dating and paleomagnetic excursions to generate a chronology for the upper ca. 150 ka of sedimentation at Lake Bosumtwi and employ a Bayesian approach to generate a continuous age-depth relationship. The resultant chronology is then used to test the effectiveness of tuning of an environmental magnetic proxy for dust against a well-dated record of high latitude dust. Our approach highlights the advantages of using multiple dating approaches, and the dangers of relying on too few age constraints when dating long sedimentary sequences. However, the excellent agreement between the different approaches over most of the record suggest that well-constrained age-depth models for long sedimentary sequences can be produced using this combination of approaches. Furthermore, our data provide support for extending the chronology beyond the limit of radiocarbon, U-series and OSL in the future using paleomagnetic excursions/reversals and tuning against well-dated high latitude paleoclimate records. © 2012 Elsevier B.V.
1376.
Carbon-isotope stratigraphy from terrestrial organic matter through the monterey event, Miocene, New Jersey margin (IODP Expedition 313)
Geosphere,
9
(5)
1303-1318
2013
ISSN: 1553040XKeywords:▾
carbon isotope; deposition; environmental factor; Miocene; mixing; organic matter; palynology; pyrolysis; shelf sediment; siliciclastic deposit; stratigraphy; strontium isotope, New Jersey; United States
Abstract: ▾ The stratigraphic utility of carbon-isotope values from terrestrial organic matter is explored for Miocene siliciclastic sediments of the shallow shelf, New Jersey margin, USA (Integrated Ocean Drilling Program [IODP] Expedition 313). These shallow marine strata, rich in terrestrial organic matter, provide a record of deposition equivalent to the Monterey event, a prolonged interval of time characterized by relatively positive carbon-isotope values recorded from foraminiferal carbonate in numerous oceanic settings. Coherent stratigraphic trends and short-term isotopic excursions are observed consistently in palynological preparation residues, concentrated woody phytoclasts, and individually picked woody phytoclasts obtained from the New Jersey sediments. A bulk organic matter curve shows somewhat different stratigraphic trends but, when corrected for mixing of marine-terrestrial components on the basis of measured C/N ratios, a high degree of conformity with the woody phytoclast record is observed. However, assuming that the correlations based on strontium-isotope values and biostratigraphy are correct, the carbon-isotope record from the New Jersey margin contrasts with that previously documented from oceanic settings (i.e., lack of positive excursion of carbonisotope values in terrestrial organic matter through the Langhian Stage). Factors that may potentially bias local terrestrial carbonisotope records include reworking from older deposits, degradation and diagenesis, as well as environmental factors affecting vegetation in the sediment source areas. These possible factors are assessed on the basis of pyrolysis data, scanning electron microscope observations, and comparison to palynological indices of environmental change. Some evidence is found for localized degradation and/or reworking of older woody phytoclasts, but where such processes have occurred they do not readily explain the observed carbon-isotope values. It is concluded that the overall carbon-isotope signature for the exchangeable carbon reservoir is distorted, to the extent that the Monterey event excursion is not easily identifiable. The most likely explanation is that phytoclast reworking has indeed occurred in clinoform toe-ofslope facies, but the reason for the resulting relatively heavy carbon-isotope values in the Burdigalian remains obscure. © 2013 Geological Society of America.
1375.
Amplified bioproductivity during Transition IV (332 000-342 000 yr ago): Evidence from the geochemical record of Lake El'gygytgyn
Climate of the Past,
9
(2)
679-686
2013
ISSN: 18149324Keywords:▾
climate change; data acquisition; geochemical cycle; ice core; lacustrine environment; marine isotope stage; paleoclimate; record; silica; titanium, Arctic; Chukchi; Elgygytgyn Lake; Greenland; Russian Federation
Abstract: ▾ To date, terrestrial archives of long-term climatic change within the Arctic have widely been restricted to ice cores from Greenland and, more recently, sediments from Lake El'gygytgyn in northeast Arctic Russia. Sediments from this lake contain a paleoclimate record of glacialinterglacial cycles during the last three million years. Lowresolution studies at this lake have suggested that changes observed during Transition IV (the transition from marine isotope stage (MIS) 10 to MIS 9) are of greater amplitude than any observed since. In this study, geochemical parameters are used to infer past climatic conditions thus providing the first high-resolution analyses of Transition IV from a terrestrial Arctic setting. These results demonstrate that a significant shift in climate was subsequently followed by a rapid increase in biogenic silica (BSi) production. Following this sharp increase, bioproductivity remained high, but variable, for over a thousand years. This study reveals differences in the timing and magnitude of change within the ratio of silica to titanium (Si/Ti) and BSi records that would not be apparent in lower resolution studies. This has significant implications for the increasingly common use of Si/Ti data as an alternative to traditional BSi measurements. © Author(s) 2013.
1374.
An earthquake gap south of Istanbul
Nature Communications,
4
2013
ISSN: 20411723Keywords:▾
active fault; earthquake event; fault zone; Kocaeli earthquake 1999; microearthquake; nucleation; seismic hazard; seismograph, article; biological accident; correlation analysis; earthquake; Turkey (republic), Earthquakes; Geography; Humans; Islands; Oceans and Seas; Turkey, Istanbul [Turkey]; Sea of Marmara; Turkey
Abstract: ▾ Over the last century the North Anatolian Fault Zone in Turkey has produced a remarkable sequence of large earthquakes. These events have now left an earthquake gap south of Istanbul and beneath the Marmara Sea, a gap that has not been filled for 250 years. Here we investigate the nature of the eastern end of this gap using microearthquakes recorded by seismographs primarily on the Princes Islands offshore Istanbul. This segment lies at the western terminus of the 1999 Mw7.4 Izmit earthquake. Starting from there, we identify a 30-km-long fault patch that is entirely aseismic down to a depth of 10 km. Our evidence indicates that this patch is locked and is therefore a potential nucleation point for another Marmara segment earthquake - a potential that has significant natural hazards implications for the roughly 13 million Istanbul residents immediately to its north. © 2013 Macmillan Publishers Limited. All rights reserved.
1373.
Assessing the ratio of archaeol to caldarchaeol as a salinity proxy in highland lakes on the northeastern Qinghai-Tibetan Plateau
Organic Geochemistry,
5469 – 77
2013
ISSN: 01466380Keywords:▾
China; Qinghai-Xizang Plateau; Archaea; Degradation; Lakes; Lipids; Sedimentology; Surficial sediments; Archaeal; Degradation kinetics; Hypersaline; In-situ production; Northeastern Qinghai-Tibetan Plateau; Organic geochemistry; Polar lipids; Qinghai-Tibetan plateau; Surface sediments; Surrounding soils; Suspended particulate matters; correlation; dehydration; in situ measurement; in situ test; lake water; lipid; organic geochemistry; paleosalinity; saline lake; sampling; upland region; Salinity measurement
Abstract: ▾ The ratio of archaeol to caldarchaeol (the ACE index) has been proposed recently as an index for paleosalinity reconstruction and is based principally on archaeal core lipids (CLs) from coastal salt pans (Turich, C., Freeman, K.H., 2011. Archaeal lipids record paleosalinity in hypersaline systems. Organic Geochemistry 42, 1147-1157). We have examined possible relationships between salinity and ACE in both CLs and intact polar lipids (IPLs) from suspended particulate matter (SPM) and surface sediments of lakes and surrounding soils on the northeastern Qinghai-Tibetan Plateau. Our results showed that ACE values were positively correlated with salinity in all samples; however, CL ACE values were systematically higher than IPL ACE values, probably due to different degradation kinetics of intact polar (IP) archaeol and IP caldarchaeol. On the other hand, surface sediment ACE values from both CLs and IPLs were lower than SPM ACE values, probably due to enhanced production of caldarchaeol relative to archaeol in the sediment. Our results demonstrate that the ACE proxy reflects changes in salinity in diverse environments on the Qinghai-Tibetan Plateau, which is promising for paleosalinity reconstruction; however, caution should be used when applying the salinity proxy before we have a better understanding of degradation kinetics of archaeal IPLs and in situ production of caldarchaeol and archaeol in sediments. © 2012 Elsevier Ltd.
1372.
Astrochronology of the Early Turonian-Early Campanian terrestrial succession in the Songliao Basin, northeastern China and its implication for long-period behavior of the Solar System
Palaeogeography, Palaeoclimatology, Palaeoecology,
38555-70
2013
ISSN: 00310182Keywords:▾
amplitude; astronomy; astrophysics; borehole; Campanian; cyclostratigraphy; eccentricity; geomagnetic field; lacustrine environment; magnetic susceptibility; Milankovitch cycle; orbital forcing; paleoenvironment; secular variation; solar system; spectral analysis; stratigraphic correlation; timescale; Turonian; uranium-lead dating, China; Nen Basin; Songliao Basin
Abstract: ▾ The first complete Early Turonian-Early Campanian lacustrine succession has been recovered from the SK-I south (SK-Is) borehole in the Songliao Basin (SLB), northeastern China. We conducted a detailed cyclostratigraphic study of natural gamma-ray (GR) log, thorium (Th) log, and magnetic susceptibility (MS) data from this core. Spectral analysis of the upper Quantou Formation (K2q3+4), Qingshankou Formation (K2qn), Yaojia Formation (K2y), and lower Nenjiang Formation (K2n1+2) reveals a hierarchy of meter- to decameter-scale cycling in the data. The wavelength ratios of the cycles in these stratigraphic units are ~20:5:2:1, corresponding with those of Milankovitch cycle periods of 405kyr (long eccentricity):100kyr (short eccentricity):37kyr (obliquity):20kyr (precession), indicating astronomical control on sedimentation. An astronomical time scale (ATS) was established by tuning interpreted 405kyr cycles to a 405kyr orbital eccentricity target curve, and to four SIMS U-Pb zircon radioisotope ages. This 'absolute' ATS provides precise numerical ages for stratigraphic boundaries, biozones, geological and geophysical events, and serves as a basis for correlation of strata and events between marine and terrestrial systems. The ages of the C33r/C34n geomagnetic polarity boundary in K2n2 and three short reversal events in K2y are estimated as 83.633Ma, 84.819-84.862Ma, 84.982-85.092Ma and 85.240-85.629Ma, respectively. Long-period amplitude modulations in the obliquity and eccentricity bands of the 405-kyr-tuned GR-Th series provide strong evidence that long-period orbital forcing influenced climate change and depositional processes in the SLB. The extracted amplitude modulations provide evidence that the orbits of Earth and Mars were not in secular resonance, and were undergoing chaotic interactions during this time, although the modulations do not match those of recent astronomical models. © 2012 Elsevier B.V.
1371.
Atmospheric simulations of southern South America's climate since the Last Glacial maximum
Quaternary Science Reviews,
71219 – 228
2013
1370.
Autecology of the extant ostracod fauna of Lake Ohrid and adjacent waters - A key to paleoenvironmental reconstruction
Belgian Journal of Zoology,
143
(1)
42 – 68
2013
ISSN: 07776276Abstract: ▾ Understanding the ecology of bioindicators such as ostracods is essential in order to reconstruct past environmental and climate change from analysis of fossil assemblages preserved in lake sediment cores. Knowledge of the ecology of ancient Lake Ohrid's ostracod fauna is very limited and open to debate. In advance of the Ohrid ICDP-Drilling project, which has potential to generate high-resolution long-term paleoenvironmental data of global importance in paleoclimate research, we sampled Lake Ohrid and a wide range of habitat types in its surroundings to assess 1) the composition of ostracod assemblages in lakes, springs, streams, and shortlived seasonal water bodies, 2) the geographical distribution of ostracods, and 3) the ecological characteristics of individual ostracod species. In total, 40 species were collected alive, and seven species were preserved as valves and empty carapaces. Of the 40 ostracod species, twelve were endemic to Lake Ohrid. The most common genus in the lake was Candona, represented by 13 living species, followed by Paralimnocythere, represented by fve living species. The most frequent species was Cypria obliqua. species with distinct distributions included Heterocypris incongruens, Candonopsis kingsleii, and Cypria lacustris. The most common species in shallow, fooded areas was H. incongruens, and the most prominent species in ditches was C. kingsleii. C. lacustris was widely distributed in channels, springs, lakes, and rivers. statistical analyses were performed on a "Lake Ohrid" dataset, comprising the subset of samples from Lake Ohrid alone, and an "entire" dataset comprising all samples collected. The unweighted pair group mean average (UPGMA) clustering was mainly controlled by species-specifc depth preferences. Canonical Correspondence Analysis (CCA) with forward selection identifed water depth, water temperature, and pH as variables that best explained the ostracod distribution in Lake Ohrid. The lack of signifcance of conductivity and dissolved oxygen in CCA of Ohrid data highlight the uniformity across the lake of the well-mixed waters. In the entire area, CCA revealed that ostracod distribution was best explained by water depth, salinity, conductivity, pH, and dissolved oxygen. salinity was probably selected by CCA due to the presence of Eucypris virens and Bradleystrandesia reticulata in short-lived seasonal water bodies. Water depth is an important, although indirect, infuence on ostracod species distribution, which is probably associated with other factors such as sediment texture and food supply. some species appeared to be indicators for multiple environmental variables, such as lake level and water temperature.