• Journal of the korean society of oceanography
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• v.35 no.2
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• pp.98-108
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• 2000

A geochemical study on a hemipelagic core sediment taken from the northwest Pacific Ocean (eastern edge of the Shikoku Basin) was conducted to use of excess barium (Ba(ex)) for evaluate the paleoceano-graphic changes. Also, the excursion of sedimentary Ba(ex) was compared with those of biogenic opal, carbonate and organic carbon content in the sediment during the last glacial and interglacial periods. The calculated Ba(ex) derived from the major and minor element shows a distinctive glacial-interglacial variations, and the mass accumulation rate (MAR) of Ba(ex) shows coincident variations with the MARs of biogenic fractions. Especially, strong positive correlation (r$^2$=0.85) between the MAR of Ba(ex) and the MAR of biogenic carbonate is recognized. Based on the strong positive correlation(r$^2$=0.85) between the MAR of Ba(ex) and the MAR of carbonate content, we estimated the degree of carbonate dissolution rate during the glacial and interglacial periods. Assuming the proportional variation and the refractory nature of barium exist between two factors, the variation of index Ca/Ba ratio in sediment indicates the degree of carbonate dissolution. Sedimentary Ca/Ba ratios index clearly show a striking fluctuation between the glacial and interglacial periods with higher positive correlation during glacial and lower correlation during interglacial. This fact indicates enhanced carbonate dissolution during interglacial period. Thus, the sedimentary Ca/Ba ratio in sedimentary records can be used as one of the useful tools for estimation of the relative degree of carbonate dissolution. The excursion of Ba(ex) and the sedimentary Ca/Ba ratio follows the typical pacific carbonate dissolution type(enhanced dissolution during interglacial and reduced dissolution during glacial time) as suggested by previous work (e.g., Wu et al., 1990). Variation in sedimentary Ca/Ba ratio thus strongly supports that glacial-interglacial fluctuation in carbonate dissolution has been prevailed in the northwest Pacific Ocean.

• Ocean and Polar Research
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• v.41 no.4
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• pp.265-274
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• 2019

To trace the provenance of fine-grained sediments in response to the growth and retreat of glaciers (i.e., Ross Ice Sheet) that affects the depositional process, various kinds of analyses including magnetic susceptibility, granulometry, and clay mineral composition with AMS ¹⁴C age dating were carried out using a gravity core KI-13-GC2 obtained from the Central Basin of the Ross Sea continental margin. The sediments mostly consist of silty mud to sand with ice-rafted debris, the sediment colors alternate repeatedly between light brown and gray, and the sedimentary structures are almost bioturbated with some faint laminations. Among the fine-grained clay mineral compositions, illite is highest (59.1-76.2%), followed by chlorite (12.4-21.4%), kaolinite (4.1-11.6%), and smectite (1.2-22.6%). Illite and chlorite originated from the Transantarctic mountains (metamorphic rocks and granitic rocks) situated to the south of the Ross Sea. Kaolinite might be supplied from the sedimentary rocks of Antarctic continent underneath the ice sheet. The provenance of smectite was considered as McMurdo volcanic group around the Victoria Land in the western part of the Ross Sea. Chlorite content was higher and smectite content was lower during the glacial periods, although illite and kaolinite contents are almost consistent between the glacial and interglacial periods. The glacial increase of chlorite content may be due to more supply of the reworked continental shelf sediments deposited during the interglacial periods to the Central Basin. On the contrary, the glacial decrease of smectite content may be attributed to less transport from the McMurdo volcanic group to the Central Basin due to the advanced ice sheet. Although the source areas of the clay minerals in the Central Basin have not changed significantly between the interglacial and glacial periods, the transport pathways and delivery mechanism of the clay minerals were different between the glacial and interglacial periods in response to the growth and retreat of Ross Ice Sheet in the Ross Sea.

• Journal of Astronomy and Space Sciences
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• v.34 no.3
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• pp.207-212
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• 2017

During the last glacial-interglacial transition, there were multiple intense climatic events such as the Bølling-Allerød warming and Younger Dryas cooling. These events show abrupt and rapid climatic changes. In this study, the climate events and cycles during this interval are examined through wavelet analysis of Arctic and Antarctic ice-core $^{18}O$ and tropical marine $^{14}C$ records. The results show that periods of ~1383-1402, ~1029-1043, ~726-736, ~441-497 and ~202-247 years are dominant in the Arctic region, whereas periods of ~1480, ~765, ~518, ~311, and ~207 years are prominent in the Antarctic TALDICE. In addition, cycles of ~1019, ~515, and ~209 years are distinct in the tropical region. Among these variations, the de Vries cycle of ~202-209 years, correlated with variations in solar activity, was detected globally. In particular, this cycle shows a strong signal in the Antarctic between about 13,000 and 10,500 yr before present (BP). In contrast, the Eddy cycle of ~1019-1043 years was prominent in Greenland and the tropical region, but was not detected in the Antarctic TALDICE records. Instead, these records showed that the Heinrich cycle of ~1480 year was very strong and significant throughout the last glacial-interglacial interval.

• Ocean and Polar Research
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• v.33 no.3
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• pp.211-221
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• 2011

Contents of biogenic components [opal, $CaCO_3$, TOC (total organic carbon)] were measured in Core LHB-3PC sediments collected off Lutzow-Holm Bay, in order to understand glacial-interglacial cyclic variation of the high-latitude surface-water paleoproductivity, in the Indian Sector of the Southern Ocean. An age model was established from the correlation of ARM/IRM ratios of Core LHB-3PC with LR04 stack benthic ${\delta}^{18}O$ records, in complement with radiocarbon isotope ages and biostratigraphic Last Appearance Datum (LAD). The core-bottom age was estimated to be about 700 ka. Although the $CaCO_3$ content is very low less than 1.0% throughout the core, the opal and TOC contents show clear glacial-interglacial cyclic variation such that they are high during the interglacial periods (7.2-50.3% and 0.05-1.00%, respectively) and low during the glacial periods (5.2-25.2% and 0.01-0.68%, respectively). According to the spectral analysis, the variation of opal content is controlled mainly by eccentricity forcing and subsequently by obliquity forcing during the last 700 kyrs. The opal contents of Core LHB-3PC also represent the apparent Mid-Pleistocene Transition (MPT)-related climatic variation in the glacial-interglacial cycles. In particular, the orbital variation of the opal contents shows increasing amplitudes since marine isotope stage (MIS) 11, which defines one of the important paleoclimatic events during the late Quaternary, called the "Mid-Brunhes Event". Based on the variation of the opal contents in Core LHB-3PC, we suggest that the surface-water paleoproductivity in the Indian Sector of the Southern Ocean followed the orbital (glacial-interglacial) cycles, and was controlled mainly by the extent of sea ice distribution during the last 700 kyrs.

• Journal of the korean society of oceanography
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• v.31 no.4
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• pp.207-216
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• 1996

A geochemical study of three piston cores (ST.4, ST.6 and ST.20) taken from the Northwest Pacific (eastern edge of Shikoku Basin) provides information about changes in surface water paleoproductivity and sedimentation during the last 127 kys. Paleoproductivity variations were estimated on the basis of total organic carbon content and carbonate mass accumulation rate. The paleoproductivity based on total organic carbon shows significant spatial variations between glacial and interglacial periods. During the last glacial maximum (LGM) paleoproductivity increased about 1.5 times with deglaciation decrease compared with those of the Holocene at inner side of the Shikoku Basin (ST.4 and ST.6). On the other hand, paleoproductivity at outer side of Shikoku Basin (ST.20) indicating not distinctive increase but deglaciation increase. The C/N ratios fall below 10 for cores ST.4 and ST.6, but C/N ratios between 100 ka and 80 ka in ST.20 which show around 10 or larger values suggest a predominance of marine organic carbon with some admixture of terrigenous materials. The carbonate mass accumulation rate of three cores show different patterns of calcareous record with respect to organic carbon based paleoproductivity variation. In the inner side of Shikoku Basin (ST.4 and ST.6) the carbonate mass accumulation rate decreased during last glacial maximum, and significant increase of carbonate mass accumulation rate is recognized at outer side of Shikoku Basin (ST.20). Thus, this set of data reveals that spatial paleoproductivity variations between inner and outer side of Shikoku Basin during the glacial and interglacial periods.

• Journal of the korean society of oceanography
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• v.33 no.3
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• pp.80-89
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• 1998

Three cores were taken from the northwest Pacific Ocean (Shikoku Basin) to determine the accumulation rates of both biogenic and terrigeneous fractions since the last penultimate interglacial period. The sediment is characterized by large amounts of terrigenous materials with low biogenic fractions and intermittent volcanic-ash layers, suggesting a hemipelagic origin. Composition of major elements shows no significant differences among sites. Relatively small variation of TiO$_2$/Al$_2$O$_3$ ratios with respect to SiO$_2$ content is the strong evidence for the common origin of terrigenous materials. The fraction of biogenic carbonates varies from near 0% in ash layers to about 35%, with a gradual increase toward the south (St. 4 through St. 6 to St. 20). However, carbonate contents show step-wise increasing tendency from St. 4 through St. 6 to St. 20, which suggests a southward increase of carbonate production. The color reflectance indicates that the sediment of the southern sites contains relatively higher amounts of biogenic carbonates. The mass accumulation rate of terrigenous fractions during the glacial period was 2-3 times higher than that of interglacial period. This enhanced mass accumulation rate of terrigenous materials was concomitant with the high accumulation rate of biogenic fractions. The total sediment accumulation rate is considered as the most important factor controlling mass accumulation rates of the biogenic and terrigenous materials. The enhanced sediment accumulation during the glacial periods is interpreted as a consequence of climate-induced change in the supply of eolian dust from the Asian continent. Enhanced wind strength during the glacial time may have increased transportation of terrigenous materials to the ocean. Thus, variation of sediment accumulation is highly linked with climatic variations.

• Journal of the Mineralogical Society of Korea
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• v.32 no.3
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• pp.173-184
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• 2019

Variations in grain size distribution and clay mineral assemblage are closely related to the sedimentary facies that reflect depositional conditions during the glacial and interglacial periods. Gravity cores BS17-GC15 and BS17-GC04 were collected from the continental shelf and rise in the eastern Bellingshausen Sea during a cruise of the ANA07D Cruise Expedition by the Korea Polar Research Institute in 2017. Core sediments in BS17-GC15 consisted of subglacial diamicton, gravelly muddy sand, and bioturbated diatom-bearing mud from the bottom to the top sediments. Core sediments in BS17-GC04 comprised silty mud with turbidites, brownish structureless mud, laminated mud, and brownish silty bioturbated diatom-bearing mud from the bottom to the top sediments. The clay mineral assemblages in the two core sediments mainly consisted of smectite, chlorite, illite, and kaolinite. The clay mineral contents in core GC15 showed a variation in illite from 28.4 % to 44.5 % in down-core changes. Smectite contents varied from 31.1 % in the glacial period to 20 % in the deglacial period and 25.1 % in the interglacial period. Chlorite and kaolinite contents decreased from 40.5 % in the glacial period to 30.3 % in the interglacial period. The high contents of illite and chlorite indicated a terrigenous detritus supply from the bedrocks of the Antarctic Peninsula. Core GC04 from the continental rise showed a decrease in the average smectite content from 47.2 % in the glacial period to 20.6 % in the interglacial period, while the illite contents increased from the 21.3 % to 43.2 % from the glacial to the interglacial period. The high smectite contents in core GC04 during the glacial period may be supplied from Peter I Island, which has a known smectite-rich sediment contributed by Antarctic Circumpolar Currents. Conversely, the decrease in smectite and increase in chlorite and illite contents during the interglacial period was likely caused by a higher supply of chlorite- and illite-enriched sediment from the eastern Bellingshausen Sea shelf by the southwestward flowing contour current.

• The Korean Journal of Quaternary Research
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• v.7 no.1
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• pp.1-26
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• 1993

The estimation of the Last Interglacial sea level was made by using the thalassostatic terrace which had been developed in the lower reach of Namdaechon river in Kangneung, eastern coastal area of Korea. The fluvial terraces, which have been developed since late Pleistocene, were investigated. The main findings were as follows; 1) That Kangneung terrace I had been formed in the climax period of the Last Interglacial (Oxygen isotope stage 5e) was revealed. It was estimated that Kangneung terrace II had been formed during a certain warmer period between the climax period of the Last Interglacial and the early Last Glacial(probably Oxygen isotope stage 5c or 5a). 2) Being judged from the relative heights of the Kangneung terrace I and II, the sea levels of the formation periods of these terraces were estimated to have been relatively 17~20m and l0m higher than the present sea level, respectively. 3) The formation periods of the Wangsan terrace I and II were supposed to be the early and late Last Glacial respectively, being judged from the following 3 details ; a) the characteristics of the terrace deposits, b) the relation Wangsan terrace II to the buried valley floor, and c) the cross phenomena of the above two terraces to the Kangneung terraces. 4) The formation period of the pseudogleyed red soil in the Kangneung terrace I was estimated to be the middle or late period of the Last Interglacial.

• Journal of the Korean earth science society
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• v.42 no.6
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• pp.677-687
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• 2021

In this study, we analyzed diatoms from core RS15-GC41 collected in Iselin Bank, Ross Sea. A total of 24 genera and 35 species of diatoms are identified, and the having valve abundance of diatoms varies from 0.2 to 28.6×10⁶/g. Four diatom assemblage zones are established by the vertical distribution of diatoms, and changed with a cycle of 100 kyrs. RS15-GC41 were deposited over the last 400 kyrs (corresponding to Marine Isotope Stages 1-11). The open-water species Fragilariopsis kerguelensis, Rhizosolenia styliformis, and Thalassionema nitzschioides abundantly occurred in interglacial periods. Whereas, Actinocyclus actinochilus abundantly dominant during the glacial periods. The distribution of these diatoms indicated, it can be seen that the sea-ice extent was larger and lasted longer during MIS 7, 9, and 11 than that of MIS 1, 3, and 5. Moreover, Paralia sulcata was abundantly predominant in MIS 7, 9, and 11; this finding suggests likely indicating that P. sulcata was transported from the coastal/inner shelf area to the study site, during accumulated in the sediments, reworked with the influx of ice-rafted debris by the currents

• The Journal of the Petrological Society of Korea
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• v.23 no.3
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• pp.249-259
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• 2014

Proxies for paleo-circulation are drawing much interest with the recognition that ocean circulation plays an important part in the redistribution of heat and climate change on orbital and millennial timescales. In this review, we will introduce how neodymium isotope ratios of the authigenic fraction of marine sediments can be used as a proxy for ocean circulation along with analytical methods and two case studies. The first case study shows how the North Atlantic Deep Water (NADW) has varied over the glacial-interglacial and stadial-interstadial periods. The second case study shows how the freshwater budget and water circulation within the Arctic Ocean can be reconstructed for the last glacial period.