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박장준,엄인권,신경훈 한국지질과학협의회 2019 Geosciences Journal Vol.23 No.6
This study details sedimentary and compositional characteristics of the Middle to Late and Early Pleistocene calcareous clay units recovered from Site U1453 in the middle Bengal Fan. The sedimentary characteristics reveal that the calcareous clay units consist of calcareous hemipelagic muds and terrigenous hemiturbidite muds which represent intervening periods of hemipelagic sedimentation sensu stricto and a slow sedimentation from suspension clouds of low-concentration turbidity currents on the fan surface, otherwise dominated by sand and mud turbidites. Variations in compositions, such as organic and inorganic carbon contents and δ13C of bulk organic matters of the calcareous hemipelagic muds, indicate the glacial-interglacial climate forcing of carbonate dissolution, surface marine productivity, and sources of particulate organic matters in the middle Bengal Fan during the Middle to Late Pleistocene. The glacial-interglacial climate forcing on hemipelagic sedimentation seems to be much obscure during the Early Pleistocene because of dilution by terrigenous clay inputs. Grain-size distribution of bulk sediments suggests the presence of coarse foraminifer and finer nannofossil modes in the calcareous clay units and the size of dominant foraminifer species could have been finer in the Early Pleistocene.
박장준,Kyung Eun Lee,Sung Kwun Chough 한국지질과학협의회 2005 Geosciences Journal Vol.9 No.4
Records of redox-sensitive elements (Mo, Cd, Cu, Vand U), δ18O of planktonic foraminifera (δ18Opf), and organic car-bon and biogenic opal contents in dark laminated mud (DLM)layers of the East/Japan Sea reveal relative role of primary pro-ductivity versus bottom-water stagnation for the formation ofthese layers during the last 25,000 years. Enrichments of redox-sensitive elements in these layers indicate that bottom waters werereduced during the formation of the lower DLM (22,500-15,00014C yr B.P.) and the upper DLM (10,400-10,200 14C yr B.P.), prob-ably to a greater extent in the lower layer. Anomalous low δ18Opfvalues and minimal contents of both organic carbon and biogenicopal suggest that bottom-water stagnation due to density-stratifiedwater column could be more important than primary productivityfor the lower DLM formation. In contrast, the relatively high con-tents of the organic carbon in the upper DLM invoke a primaryrole of enhanced productivity in the formation. This inference is,however, questioned by the absence of comparable increase in bio-genic opal contents which is expected from generally coupled pro-duction of organic carbon and opal in surface water. The discrepancybetween the organic carbon and opal records suggests that a bot-tom-water stagnation, which might have caused the preferentialpreservation of organic carbon in the reducing bottom-water con-dition, could be also more important than primary productivityfor the upper DLM formation.
박장준,Sang-Joon Han,김부근 한국지질과학협의회 2004 Geosciences Journal Vol.8 No.4
In order to examine the variations of terrigenousdetrital components in the core (97PC-19) sediments from thesouthern margin of the Ulleung Basin, we detail changes in grain-size composition and contents of major elements such as detritalSiO2 (detSiO2), TiO2, Al2O3, MgO and K2O since the Last GlacialMaximum (LGM). The variations of detrital components are charac-terized by the significant elevations of detSiO2/Al2O3 and TiO2/Al2O3ratios with the concomitant increase of silt to clay ratios during thelast deglaciation (1015 ka). Such a prominent increase suggestsan enhanced flux of detrital quartz and Ti-bearing minerals rel-ative to Al-rich clay minerals which can be attributed to eitheraeolian transport or hemipelagic advection. Similar variations ofdetrital components during the last deglaciation are much morepronounced in the core 95PC-1, located more proximal to the KoreaStrait, as evidenced by the high sedimentation rate and sand andsilt contents. However, this temporal variation is not clearly observedin ODP site 797 far from the Korea Strait. The spatial change ofthe detrital components among the cores suggests a primary con-trol of hemipelagic fluxes of riverine sediments relative to aeoliandust fluxes on the variations of detrital components since the LGM.The hemipelagic fluxes were mostochannels of the Nakdong River that extended onto the shelf mar-gin of the Korea Strait during the last sea-level lowstand andincreased by shore-parallel transport of paleocurrents through theKorea Strait during the early stage of the postglacial transgression.
박장준,유동근,In kwon Um,이상훈,우경식 한국지질과학협의회 2013 Geosciences Journal Vol.17 No.2
Detailed analysis of core sediments and acoustic characteristics of Chirp sub-bottom profiles from a submarine ridge in the southern slope of the Ulleung Basin, East Sea, Korea, reveals changes in sedimentary processes and deformation of sedimentary sequence induced by seafloor mound formation since the Last Glacial Maximum (LGM). The core sediments consist generally of four sedimentary facies which represent hemipelagic sedimentation under a poorly-oxygenated bottom-water condition during the LGM (crudely laminated mud), shoreface erosion and seaward transport off the shelf break during the post-glacial transgression (bioturbated sandy mud or muddy sand), hemipelagic sedimentation under generally well-oxygenated bottom-water condition after the sea-level rise (bioturbated mud), and episodic precipitation of authigenic carbonates by methane venting since the LGM (authigenic carbonate-bearing mud), respectively. The formation of authigenic carbonate-bearing mud facies and associated accumulation of near-seafloor gas hydrates might have led to up-warping of the sediment cover since the LGM that resulted in the seafloor mounds protruding along the crest line of the ridge. The effects of up-warping by expansion of the subsurface gas hydrates are firstly manifested in this paper by the abrupt lateral changes in the sedimentary facies distribution and uplifted acoustic reflectors between the mounds and the background seafloor.