Origin and depositional environment of fine-grained sediments since the last glacial maximum in the southeastern Yellow Sea: evidence from rare earth elements

2015 ◽  
Vol 35 (6) ◽  
pp. 421-431 ◽  
Author(s):  
In Kwon Um ◽  
Man Sik Choi ◽  
Gwang Soo Lee ◽  
Tae Soo Chang
2020 ◽  
Author(s):  
Hyo Jin Koo ◽  
Hyen Goo Cho

Abstract. The sediment supply to the central Yellow Sea since the Last Glacial Maximum was uncovered through clay mineralogy and geochemical analysis of core 11YS-PCL14 in the Central Yellow Sea mud (CYSM). The core can be divided into four units: Unit 4 (700–520 cm; 15.5–14.8 ka), Unit 3 (520–280 cm; 14.8–12.1 ka), Unit 2 (280–130 cm; 12.1–8.8 ka), and Unit 1 (130–0 cm;


2017 ◽  
Vol 87 (2) ◽  
pp. 191-207 ◽  
Author(s):  
Jason R. Price ◽  
Joel Moore ◽  
Dalton Kerans

AbstractRare earth element (REE) release from weathering of accessory monazite [(REE)PO4] since the last glacial maximum at 18.1 ka was investigated in sediment recovered from an outlet lake within the glaciated Loch Vale watershed, Colorado, USA. Labile REEs in the sediments reveal monazite weathering increased during the Younger Dryas chronozone (YDC) 13.2 to 11.1 ka when alpine glaciers advanced as climate cooled and bedrock comminution increased. Monazite dissolution peaked at approximately the Pleistocene-Holocene transition ~10.5 ka. During the Holocene, REE concentrations decline, reflecting a reduction in monazite weathering. The REE cerium (Ce) may occur as trivalent or tetravalent cations, and the Ce anomaly (Cen/Ce*n) in sediment permits interpretations of paleoredox conditions. The Cen/Ce*n decreases from 18.1 ka to the Pleistocene-Holocene boundary. Initially, oxidizing conditions within the watershed increased because of enlargement of the proglacial area as the ice retreated. At the onset of the YDC, oxidation further escalated in response to enhanced chemical weathering associated with glacial advance. A more stable Holocene climate and landscape resulted in relatively small changes in Cen/Ce*n values. Slightly decreasing Cen/Ce*n values over the last several hundred years are consistent with present-day stream water values and may reflect the onset of present-day hydrobiogeochemical conditions.


2021 ◽  
pp. 10-17
Author(s):  
Oguz Turkozan

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.


2017 ◽  
Author(s):  
Brendon J. Quirk ◽  
◽  
Jeffrey R. Moore ◽  
Benjamin J. Laabs ◽  
Mitchell A. Plummer ◽  
...  

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