Use of Rubidium to Date Loess and Paleosols of the Louchan Sequence, Central China

2000 ◽  
Vol 54 (2) ◽  
pp. 198-205 ◽  
Author(s):  
Jun Chen ◽  
Junfeng Ji ◽  
Yang Chen ◽  
Zhisheng An ◽  
John A. Dearing ◽  
...  
Keyword(s):  
Sedimentation Rate ◽  
Time Scale ◽  
Winter Monsoon ◽  
Central China ◽  
Early Pleistocene ◽  
Monsoon Climate ◽  
The Past ◽  
Pleistocene Climate ◽  
Curvilinear Relation ◽  
The Last Glacial

Rb concentrations, analyzed at 20-cm intervals from the Luochuan sequence of loess and paleosols, are sensitive to the loess–paleosol alternation controlled by monsoon climate. Because it is geochemically immobile, Rb can be well preserved in the loess–paleosol sequence after deposition, and its concentration depends mainly on properties of the winter monsoon-blown dust and on intensity of the summer monsoon-induced pedogenesis. A curvilinear relation has been developed between the measured Rb-concentration and the apparent sedimentation rate for the last glacial–interglacial cycle. This relation provides a time scale that corresponds well with the presently accepted ages for paleomagnetic reversals of Brunhes/Matuyama and Jaramillo events. With allowance for reduced Rb concentrations caused by early Pleistocene climate, the Rb-based time scale is also consistent with the boundary ages of other major paleomagnetic reversals of the past 2.58 myr.

scholarly journals Ventilation changes in the western North Pacific since the last glacial period

2011 ◽  
Vol 7 (4) ◽  
pp. 2719-2739 ◽  
Author(s):  
Y. Okazaki ◽  
T. Sagawa ◽  
H. Asahi ◽  
K. Horikawa ◽  
J. Onodera
Keyword(s):  
Sedimentation Rate ◽  
North Pacific ◽  
Western North Pacific ◽  
Glacial Period ◽  
High Quality ◽  
Last Glacial Period ◽  
The Past ◽  
High Sedimentation ◽  
The Last Glacial

Abstract. We reconstructed the ventilation record of deep water at 2100 m depth in the mid-latitude western North Pacific over the past 25 kyr from radiocarbon measurements of coexisting planktic and benthic foraminiferal shells in sediment with a high sedimentation rate. The 14C data on fragile and robust planktic foraminiferal shells were concordant with each other, ensuring high quality of the reconstructed ventilation record. The radiocarbon activity changes were consistent with the atmospheric record, suggesting that no massive mixing of old carbon from the abyssal reservoir occurred throughout the glacial to deglacial periods.

Quaternary structural partitioning within the rigid Tarim plate inferred from magnetostratigraphy and sedimentation rate in the eastern Tarim Basin in China

2014 ◽  
Vol 81 (3) ◽  
pp. 424-432 ◽  
Author(s):  
Hong Chang ◽  
Zhisheng An ◽  
Weiguo Liu ◽  
Hong Ao ◽  
Xiaoke Qiang ◽  
...  
Keyword(s):  
Tarim Basin ◽  
Sedimentation Rate ◽  
Structural Evolution ◽  
Early Pleistocene ◽  
Tectonic Activity ◽  
Geological Time ◽  
Geological Time Scale ◽  
Abrupt Decrease ◽  
Accommodation Space ◽  
Pleistocene Climate

AbstractIt has been proposed that within the Tarim Basin tectonic activity has been limited since Triassic time. However, on the basis of magnetostratigraphy from the eastern Tarim Basin, which defines the chronology of sedimentation and structural evolution of the basin, we show that the basin interior has been uplifted and partitioned during Quaternary. The magnetostratigraphy was constructed from 2228 samples that yielded acceptable inclination values. Characteristic remnant magnetization (ChRM) with both normal (N1–N11) and reversed (R1–R11) polarity was isolated by thermal demagnetization. The data correlate best with polarity chrons C3r to C1n, which range from 5.39 Ma to recent on the geological time scale 2004 (GTS2004). An abrupt decrease in the sedimentation rate is observed at 1.77 Ma in the Ls1 core. This change does not overlap with known Pleistocene climate-change events. We attribute this sedimentation rate decrease to a structurally controlled local decrease in accommodation space where basin basement uplifts occur. This period of sedimentary environmental change reveals that structural partitioning in the basement of the Tarim Basin occurred since ~ 1.77 Ma, and we speculate that tilting of the Southeast Uplift (a sub-basin unit) within the Tarim Basin began in early Pleistocene time.

East Asia winter monsoon variations on a millennial time-scale before the last glacial-interglacial cycle

1999 ◽  
Vol 14 (2) ◽  
pp. 101-110 ◽  
Author(s):  
Huayu Lu ◽  
Ko Van Huissteden ◽  
Zhisheng An ◽  
Govert Nugteren ◽  
Jef Vandenberghe
Keyword(s):  
East Asia ◽  
Time Scale ◽  
Winter Monsoon ◽  
Last Glacial ◽  
Millennial Time Scale ◽  
The Last Glacial

scholarly journals Ventilation changes in the western North Pacific since the last glacial period

2012 ◽  
Vol 8 (1) ◽  
pp. 17-24 ◽  
Author(s):  
Y. Okazaki ◽  
T. Sagawa ◽  
H. Asahi ◽  
K. Horikawa ◽  
J. Onodera
Keyword(s):  
Sedimentation Rate ◽  
North Pacific ◽  
Western North Pacific ◽  
Glacial Period ◽  
High Quality ◽  
Last Glacial Period ◽  
The Past ◽  
High Sedimentation ◽  
The Last Glacial

Abstract. We reconstructed the ventilation record of deep water at 2100 m depth in the mid-latitude western North Pacific over the past 25 kyr from radiocarbon measurements of coexisting planktic and benthic foraminiferal shells in sediment with a high sedimentation rate. The 14C data on fragile and robust planktic foraminiferal shells were concordant with each other, ensuring high quality of the reconstructed ventilation record. The radiocarbon activity changes were consistent with the atmospheric record, suggesting that no massive mixing of old carbon from the abyssal reservoir occurred throughout the glacial to deglacial periods.

Peatland evolution and associated environmental changes in central China over the past 40,000 years

2015 ◽  
Vol 84 (2) ◽  
pp. 255-261 ◽  
Author(s):  
Yuxin He ◽  
Cheng Zhao ◽  
Zhuo Zheng ◽  
Zhonghui Liu ◽  
Ning Wang ◽  
...  
Keyword(s):  
Summer Monsoon ◽  
Environmental Changes ◽  
Central China ◽  
The Past ◽  
Monsoonal Precipitation ◽  
Moisture Balance ◽  
History Of ◽  
Precipitation Changes ◽  
Dajiuhu Peatland ◽  
The Last Glacial

Central China has experienced stronger summer monsoon during warm periods such as Marine Isotope Stages (MIS) 1 and 3, and weaker summer monsoon during cool periods such as MIS 2. The evolution history of Dajiuhu subalpine peatland in central China can help investigate how the expansion and shrinkage of peatland were associated with monsoonal strength over the last glacial–interglacial cycle. Here we apply bulk organic carbon and molecular biomarkers (hopane and n-alkane) to reconstruct the evolution history for the Dajiuhu peatland over the past 40,000 yr. The results indicate fluctuations between lacustrine and peat-like deposition during MIS 3, steady lacustrine deposition during MIS 2, and peatland initiation and expansion during MIS 1 in the Dajiuhu peatland. Therefore, at the glacial–interglacial scale, warmer summer and cooler winter conditions in interglacial periods are crucial to trigger peat deposition, whereas reduced evaporation in glacial period instead of decreased monsoonal-driven precipitation would have played a predominant role in the regional effective moisture balance. However, within the Holocene (MIS 1), monsoonal precipitation changes appear to be the main controller on millennial-scale variations of water-table level of the Dajiuhu peatland.

Reconstructions of the past distribution of Testudo graeca mitochondrial lineages in the Middle East and Transcaucasia support multiple refugia since the Last Glacial Maximum

2021 ◽  
pp. 10-17
Author(s):  
Oguz Turkozan
Keyword(s):  
Middle East ◽  
Last Glacial Maximum ◽  
Glacial Maximum ◽  
Testudo Graeca ◽  
Last Glacial ◽  
The Past ◽  
Precipitation Seasonality ◽  
Multiple Refugia ◽  
The Last Glacial Maximum ◽  
The Last Glacial

A cycle of glacial and interglacial periods in the Quaternary caused species’ ranges to expand and contract in response to climatic and environmental changes. During interglacial periods, many species expanded their distribution ranges from refugia into higher elevations and latitudes. In the present work, we projected the responses of the five lineages of Testudo graeca in the Middle East and Transcaucasia as the climate shifted from the Last Glacial Maximum (LGM, Mid – Holocene), to the present. Under the past LGM and Mid-Holocene bioclimatic conditions, models predicted relatively more suitable habitats for some of the lineages. The most significant bioclimatic variables in predicting the present and past potential distribution of clades are the precipitation of the warmest quarter for T. g. armeniaca (95.8 %), precipitation seasonality for T. g. buxtoni (85.0 %), minimum temperature of the coldest month for T. g. ibera (75.4 %), precipitation of the coldest quarter for T. g. terrestris (34.1 %), and the mean temperature of the driest quarter for T. g. zarudyni (88.8 %). Since the LGM, we hypothesise that the ranges of lineages have either expanded (T. g. ibera), contracted (T. g. zarudnyi) or remained stable (T. g. terrestris), and for other two taxa (T. g. armeniaca and T. g. buxtoni) the pattern remains unclear. Our analysis predicts multiple refugia for Testudo during the LGM and supports previous hypotheses about high lineage richness in Anatolia resulting from secondary contact.

Spatial variation of East Asian winter monsoon evolution between northern and southern China since the last glacial maximum

2021 ◽  
pp. 1-14
Author(s):  
Qin Li ◽  
Haibin Wu ◽  
Jun Cheng ◽  
Shuya Zhu ◽  
Chunxia Zhang ◽  
...  
Keyword(s):  
East Asian Winter Monsoon ◽  
Southern China ◽  
Ice Sheets ◽  
Northern China ◽  
Winter Monsoon ◽  
Asian Winter Monsoon ◽  
Spatial Differences ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Abstract The East Asian winter monsoon (EAWM) is one of the most dynamic components of the global climate system. Although poorly understood, knowledge of long-term spatial differences in EAWM variability during the glacial–interglacial cycles is important for understanding the dynamic processes of the EAWM. We reconstructed the spatiotemporal characteristics of the EAWM since the last glacial maximum (LGM) using a comparison of proxy records and long-term transient simulations. A loess grain-size record from northern China (a sensitive EAWM proxy) and the sea surface temperature gradient of an EAWM index in sediments of the southern South China Sea were compared. The data–model comparison indicates pronounced spatial differences in EAWM evolution, with a weakened EAWM since the LGM in northern China but a strengthened EAWM from the LGM to the early Holocene, followed by a weakening trend, in southern China. The model results suggest that variations in the EAWM in northern China were driven mainly by changes in atmospheric carbon dioxide (CO2) concentration and Northern Hemisphere ice sheets, whereas orbital insolation and ice sheets were important drivers in southern China. We propose that the relative importance of insolation, ice sheets, and atmospheric CO2 for EAWM evolution varied spatially within East Asia.

East Asian winter monsoon variation during the last 3000 years as recorded in a subtropical mountain lake, northeastern Taiwan

The Holocene ◽  
2021 ◽  
pp. 095968362110190
Author(s):  
Tsai-Wen Lin ◽  
Stefanie Kaboth-Bahr ◽  
Kweku Afrifa Yamoah ◽  
André Bahr ◽  
George Burr ◽  
...  
Keyword(s):  
Grain Size ◽  
East Asian Winter Monsoon ◽  
East Asian ◽  
Winter Monsoon ◽  
Mountain Lake ◽  
Sediment Grain Size ◽  
Global Monsoon ◽  
Asian Winter Monsoon ◽  
The Past ◽  
Monsoon System

The East Asian Winter Monsoon (EAWM) is a fundamental part of the global monsoon system that affects nearly one-quarter of the world’s population. Robust paleoclimate reconstructions in East Asia are complicated by multiple sources of precipitation. These sources, such as the EAWM and typhoons, need to be disentangled in order to understand the dominant source of precipitation influencing the past and current climate. Taiwan, situated within the subtropical East Asian monsoon system, provides a unique opportunity to study monsoon and typhoon variability through time. Here we combine sediment trap data with down-core records from Cueifong Lake in northeastern Taiwan to reconstruct monsoonal rainfall fluctuations over the past 3000 years. The monthly collected grain-size data indicate that a decrease in sediment grain size reflects the strength of the EAWM. End member modelling analysis (EMMA) on sediment core and trap data reveals two dominant grain-size end-members (EMs), with the coarse EM 2 representing a robust indicator of EAWM strength. The downcore variations of EM 2 show a gradual decrease over the past 3000 years indicating a gradual strengthening of the EAWM, in agreement with other published EAWM records. This enhanced late-Holocene EAWM can be linked to the expansion of sea-ice cover in the western Arctic Ocean caused by decreased summer insolation.

Absence of Last Glacial Maximum Records in Lowland Tropical Forests

1998 ◽  
Vol 49 (2) ◽  
pp. 233-237 ◽  
Author(s):  
Marie-Pierre Ledru ◽  
Jacques Bertaux ◽  
Abdelfettah Sifeddine ◽  
Kenitiro Suguio
Keyword(s):  
South America ◽  
Tropical Forests ◽  
Last Glacial Maximum ◽  
Sedimentation Rate ◽  
Glacial Maximum ◽  
Radiocarbon Dates ◽  
Last Glacial ◽  
The Last Glacial Maximum ◽  
Pollen Records ◽  
The Last Glacial

Environmental conditions of the lowland tropical forests during the last glacial maximum (LGM) between ca 20,000 and 18,000 14C yr B.P., are reevaluated in terms of dating control and lithology analyzed in seven pollen records from South America. The reevaluation shows that probably in none of the published records are LGM sediments present or abundant. This conclusion is based on the occurrence of abrupt lithologic changes coupled with changes in sedimentation rate interpolated from radiocarbon dates. These findings suggest that the LGM was represented probably by a hiatus of several thousand years, indicative of drier climates than before or after.

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