13:45 〜 15:15
[MIS02-P01] REE and Sr-Nd-O isotope geochemistry of inorganic solid matter in the East Siberian ice wedges
キーワード：Siberia, ice wedge, dust provenance, paleoclimate
In East Siberia, permafrost is widely distributed, and ice wedges developed therein contain a large amount of soil material introduced at the time of formation. Using this, this study aims to investigate paleoenvironments and paleoclimate conditions through geochemical analysis of inorganic substances in the ice wedges. The ice wedges were collected from the Batagay and Yakutsk (Cyuie and Churapcha) areas in East Siberia. The samples are known to have formed during the Last Glacial Maximum (LGM), except for the lower ice complex in Batagay (estimated ~677 to 622 kyr). Rare earth element (REE) abundance and Sr-Nd isotope compositions of the samples were measured by an inductively coupled plasma-mass spectrometer (ICP-MS) and thermal ionization mass spectrometer (TIMS), respectively. Oxygen isotope compositions of quartz grains extracted from the samples were measured by a secondary ion mass spectrometer (SIMS).
The REE and Sr-Nd isotope analysis results show LREE enriched trend, 87Sr/86Sr ratios (0.715784 to 0.717291), and εNd(0) values(-8.3 to -17.9). This indicates that the solid material in the ice wedges generally originated from the upper continental crust (UCC). In addition, the above values are similar to those of suspended particulate matter in adjacent rivers (e.g., Lena and Yana) or sediment deposits in nearby seas (e.g., Laptev Sea and East Siberian Sea). Locally compared, the values of REE and Sr-Nd isotopes in the Batagay and Yakutsk samples are clearly distinguished, and the Batagay values are much closer to the aeolian deposits in northern China. Moreover, the δ18O (vs. V-SMOW) values for quartz grains generally show a distribution with two peaks: +10‰ and +15‰. The main peaks appear mainly around +10%, indicating the influx of local substances. On the other hand, it is estimated that the prominent peak around +15‰ in the Batagay samples is probably due to aeolian dust generated in the arid regions of northern China. Therefore, we suggest that dust storms from northern China during the Pleistocene may have affected eastern Siberia, particularly Batagay, and that dust particles were actively deposited with local materials during ice wedge formation.
The REE and Sr-Nd isotope analysis results show LREE enriched trend, 87Sr/86Sr ratios (0.715784 to 0.717291), and εNd(0) values(-8.3 to -17.9). This indicates that the solid material in the ice wedges generally originated from the upper continental crust (UCC). In addition, the above values are similar to those of suspended particulate matter in adjacent rivers (e.g., Lena and Yana) or sediment deposits in nearby seas (e.g., Laptev Sea and East Siberian Sea). Locally compared, the values of REE and Sr-Nd isotopes in the Batagay and Yakutsk samples are clearly distinguished, and the Batagay values are much closer to the aeolian deposits in northern China. Moreover, the δ18O (vs. V-SMOW) values for quartz grains generally show a distribution with two peaks: +10‰ and +15‰. The main peaks appear mainly around +10%, indicating the influx of local substances. On the other hand, it is estimated that the prominent peak around +15‰ in the Batagay samples is probably due to aeolian dust generated in the arid regions of northern China. Therefore, we suggest that dust storms from northern China during the Pleistocene may have affected eastern Siberia, particularly Batagay, and that dust particles were actively deposited with local materials during ice wedge formation.