High-resolution palaeomagnetic record from Sea of Marmara sediments for the last 70 ka

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 due to early diagenesis, relative palaeointensity variations in the Sea of Marmara sediments correlate well with similar records derived from other regions, such as the nearby Black Sea and the GLOPIS-75 stack. The directional record derived from the Sea of Marmara cores exhibits typical palaeosecular variation patterns, with directional anomalies at 41 and 18 ka, representing the Laschamps and postulated Hilina Pali excursions, respectively. Both directional anomalies are also associated with palaeointensity minima. A further palaeointensity minimum at 34.5 ka is likely related to the Mono Lake excursion, with no directional deviation documented in the Sea of Marmara palaeomagnetic record so far.

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Preliminary paleomagnetic results from PS97 cores from the Drake Passage for the past 110 ka

10.5194/egusphere-egu2020-3292 ◽

2020 ◽

Author(s):

Jiabo Liu ◽

Norbert Nowaczyk ◽

Xufeng Zheng ◽

Qinsong Liu ◽

Helge Arz

Keyword(s):

Southern Ocean ◽

Geomagnetic Field ◽

Sediment Cores ◽

Drake Passage ◽

Mono Lake ◽

The Past ◽

Asymmetric Pattern ◽

Relative Paleointensity ◽

Globally Distributed ◽

Northern And Southern Hemispheres

Paleomagnetic records reconstructed from globally distributed marine sediments have greatly improved our understanding of long-term paleosecular variations and geomagnetic excursions. Nevertheless, questions regarding to the development of the geomagnetic field anomaly in the Southern Atlantic Ocean and the asymmetric geomagnetic field between Northern and Southern Hemispheres are not yet satisfactorily resolved. Paleomagnetic data, particularly from the Southern Hemisphere, is needed to better define the global geomagnetic field configurations spanning paleosecular variations and excursions. In this study, three sediment cores (PS97-085, PS97-84, PS97-079) recovered from the Drake Passage, Southern Ocean were subjected to detailed rock magnetic and paleomagnetic investigations. Preliminary age models were obtained by correlating their magnetic susceptibility to the &#7839;18O master record from Dome C, Antarctica. In addition, rock magnetic records of the studied PS97 cores were further correlated to that of core PS67/197-1 with AMS 14C age constraints. The results from PS97 cores are thus continuously covering the past about 110 ka. Rock magnetic results indicate titanomagnetite is the dominant magnetic carrier in the studied PS97 cores. Relative paleointensities (RPI) derived from these PS97 cores are comparable with the regional relative paleointensity records and the South Atlantic paleointensity stack (SAPIS). Additionally, anomalous inclinations at about 41 ka and 35 ka, observed in core PS97-085, are coeval with the Laschamps and the Mono Lake excursions, respectively. This study provides new paleomagnetic records from the Southern Ocean, though further age constrains are needed to consolidate the paleomagnetic interpretations. The up to now obtained paleomagnetic records, together with previous studies from the Southern Ocean, are aiming to clarify the asymmetric pattern of non-dipole geomagnetic field between Northern and Southern Hemispheres.

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High-resolution seismic profiling in the Sea of Marmara (northwest Turkey): Late Quaternary sedimentation and sea-level changes

Geological Society of America Bulletin ◽

10.1130/0016-7606(1995)107<0923:hrspit>2.3.co;2 ◽

1995 ◽

Vol 107 (8) ◽

pp. 923-0936 ◽

Cited By ~ 98

Author(s):

A. D. Smith ◽

T. Taymaz ◽

F. Oktay ◽

H. Yüce ◽

B. Alpar ◽

...

Keyword(s):

High Resolution ◽

Sea Level ◽

Late Quaternary ◽

Sea Of Marmara ◽

Sea Level Changes ◽

Seismic Profiling ◽

And Sea Level

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High-resolution magnetostratigraphy of four sediment cores from the Greenland Sea-I. Identification of the Mono Lake excursion, Laschamp and Biwa I/Jamaica geomagnetic polarity events

Geophysical Journal International ◽

10.1111/j.1365-246x.1997.tb01224.x ◽

1997 ◽

Vol 131 (2) ◽

pp. 310-324 ◽

Cited By ~ 46

Author(s):

Norbert R. Nowaczyk ◽

Martin Antonow

Keyword(s):

High Resolution ◽

Sediment Cores ◽

Mono Lake ◽

Greenland Sea ◽

Geomagnetic Polarity

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Late glacial to Holocene sea-level changes in the Sea of Marmara: new evidence from high-resolution seismics and core studies

Geo-Marine Letters ◽

10.1007/s00367-010-0211-1 ◽

2010 ◽

Vol 31 (1) ◽

pp. 1-18 ◽

Cited By ~ 26

Author(s):

Kürşad Kadir Eriş ◽

M. N. Çağatay ◽

Sena Akçer ◽

Luca Gasperini ◽

Yosi Mart

Keyword(s):

High Resolution ◽

Sea Level ◽

Late Glacial ◽

Sea Of Marmara ◽

Sea Level Changes ◽

New Evidence ◽

Holocene Sea Level

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Records of the Laschamps geomagnetic polarity excursion from Black Sea sediments: magnetite versus greigite, discrete sample versus U-channel data

Geophysical Journal International ◽

10.1093/gji/ggaa506 ◽

2020 ◽

Vol 224 (2) ◽

pp. 1079-1095

Author(s):

Norbert R Nowaczyk ◽

Jiabo Liu ◽

Helge W Arz

Keyword(s):

High Resolution ◽

Black Sea ◽

Geomagnetic Field ◽

Ice Cores ◽

Mono Lake ◽

Exclusion Criterion ◽

14C Dating ◽

Discrete Sample ◽

Palaeomagnetic Data ◽

Geomagnetic Polarity

SUMMARY Magnetostratigraphic investigation of sediment cores from two different water depths in the SE Black Sea based on discrete samples, and parallel U-channels in one of the cores, yielded high-resolution records of geomagnetic field variations from the past about 68 ka. Age constrains are provided by three tephra layers of known age, accelerator mass spectrometry 14C dating, and by tuning element ratios obtained from X-ray fluorescence scanning to the oxygen isotope record from Greenland ice cores. Sedimentation rates vary from a minimum of ∼5 cm ka−1 in the Holocene to a maximum of ∼50 cm ka−1 in glacial marine isotope stage 4. Completely reversed inclinations and declinations as well as pronounced lows in relative palaeointensity around 41 ka provide evidence for the Laschamps geomagnetic polarity excursion. In one of the investigated cores also a fragmentary record of the Mono Lake excursion at 34.5 ka could be revealed. However, the palaeomagnetic records are more or less affected by greigite, a diagenetically formed magnetic iron sulphide. By definition of an exclusion criterion based on the ratio of saturation magnetization over volume susceptibility, greigite-bearing samples were removed from the palaeomagnetic data. Thus, only 25–55 per cent of the samples were left in the palaeomagnetic records obtained from sediments from the shallower coring site. The palaeomagnetic record from the deeper site, based on both discrete samples and U-channels, is much less affected by greigite. The comparison of palaeomagnetic data shows that the major features of the Laschamps polarity excursion were similarly recovered by both sampling techniques. However, several intervals had to be removed from the U-channel record due to the presence of greigite, carrying anomalous directions. By comparison to discrete sample data, also some directional artefacts in the U-channel record, caused by low-pass filtering of the broad magnetometer response functions, averaging across fast directional and large amplitude changes, can be observed. Therefore, high-resolution sampling with discrete samples should be the preferred technique when fast geomagnetic field variations, such as reversals and excursions, shall be studied from sedimentary records in the very detail.

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A comparison of annual layer thickness model estimates with observational measurements using the Berkner Island ice core, Antarctica

Antarctic Science ◽

10.1017/s0954102017000025 ◽

2017 ◽

Vol 29 (4) ◽

pp. 382-393

Author(s):

A. Massam ◽

S.B. Sneed ◽

G.P. Lee ◽

R.R. Tuckwell ◽

R. Mulvaney ◽

...

Keyword(s):

High Resolution ◽

Layer Thickness ◽

Inductively Coupled Plasma ◽

Ice Core ◽

Ultra Violet ◽

Analytical Techniques ◽

Inductively Coupled ◽

Annual Layer ◽

Icp Ms ◽

Chemical Profiles

AbstractA model to estimate the annual layer thickness of deposited snowfall at a deep ice core site, compacted by vertical strain with respect to depth, is assessed using ultra-high-resolution laboratory analytical techniques. A recently established technique of high-resolution direct chemical analysis of ice using ultra-violet laser ablation inductively-coupled plasma mass spectrometry (LA ICP-MS) has been applied to ice from the Berkner Island ice core, and compared with results from lower resolution techniques conducted on parallel sections of ice. The results from both techniques have been analysed in order to assess the capability of each technique to recover seasonal cycles from deep Antarctic ice. Results do not agree with the annual layer thickness estimates from the age–depth model for individual samples <1 m long as the model cannot reconstruct the natural variability present in annual accumulation. However, when compared with sections >4 m long, the deviation between the modelled and observational layer thicknesses is minimized to within two standard deviations. This confirms that the model is capable of successfully estimating mean annual layer thicknesses around analysed sections. Furthermore, our results confirm that the LA ICP-MS technique can reliably recover seasonal chemical profiles beyond standard analytical resolution.

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High-resolution isotope stratigraphy of the Lower Ordovician St. George Group of western Newfoundland, Canada: implications for global correlation

Canadian Journal of Earth Sciences ◽

10.1139/e09-032 ◽

2009 ◽

Vol 46 (6) ◽

pp. 403-423 ◽

Cited By ~ 14

Author(s):

Karem Azmy ◽

Denis Lavoie

Keyword(s):

High Resolution ◽

Sea Level ◽

Sea Level Changes ◽

Global Correlation ◽

Lower Ordovician ◽

Isotope Stratigraphy ◽

Platform Carbonates ◽

The Baltic ◽

Marine Platform ◽

Bottom To Top

The Lower Ordovician St. George Group of western Newfoundland consists mainly of shallow-marine-platform carbonates (∼500 m thick). It is formed, from bottom to top, of the Watts Bight, Boat Harbour, Catoche, and Aguathuna formations. The top boundary of the group is marked by the regional St. George Unconformity. Outcrops and a few cores from western Newfoundland were sampled at high resolution and the extracted micritic materials were investigated for their petrographic and geochemical criteria to evaluate their degree of preservation. The δ13C and δ18O values of well-preserved micrite microsamples range from –4.2‰ to 0‰ (VPDB) and from –11.3‰ to –2.9‰ (VPDB), respectively. The δ13Ccarb profile of the St. George Group carbonates reveals several negative shifts, which vary between ∼2‰ and 3‰ and are generally associated with unconformities–disconformities or thin shale interbeds, thus reflecting the effect of or link with significant sea-level changes. The St. George Unconformity is associated with a negative δ13Ccarb shift (∼2‰) on the profile and correlated with major lowstand (around the end of Arenig) on the local sea-level reconstruction and also on those from the Baltic region and central Australia, thus suggesting that the St. George Group Unconformity might have likely had an eustatic component that contributed to the development–enhancement of the paleomargin. Other similar δ13Ccarb shifts have been recorded on the St. George profile, but it is hard to evaluate their global extension due to the low resolution of the documented global Lower Ordovician (Tremadoc – middle Arenig) δ13Ccarb profile.

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