Evolution of the eastern margin of Korea: Constraints on the opening of the East Sea (Japan Sea)

Seismic indicators of gas hydrate and associated gas in the Ulleung Basin, East Sea (Japan Sea) and implications of heat flows derived from depths of the bottom-simulating reflector

“…12 Ma) likely to have terminated the seafloor spreading, the oceanic crust in the northern part of the Ulleung Basin would not be younger than the Middle Miocene. Kim et al (1998) and Kim et al (2007) suggested that the thickerthan-normal oceanic crust in the Ulleung Basin was formed in a region of hotter than normal mantle temperature. The picritic basalts recovered from the Ulleung Basin are characterized by the highest percentage of MgO (N10%) and the lowest percentage of Na 2 O (N2.5%) in the entire East Sea (S'edin and Sato, 1996), indicating high asthenosphere temperatures (Kim et al, 2007).…”

“…Kim et al (1998) and Kim et al (2007) suggested that the thickerthan-normal oceanic crust in the Ulleung Basin was formed in a region of hotter than normal mantle temperature. The picritic basalts recovered from the Ulleung Basin are characterized by the highest percentage of MgO (N10%) and the lowest percentage of Na 2 O (N2.5%) in the entire East Sea (S'edin and Sato, 1996), indicating high asthenosphere temperatures (Kim et al, 2007). Vigorous shallow asthenospheric convection (Currie and Hyndman, 2006) may be responsible for the higher-than-normal heat flows in the Ulleung Basin.…”

Pore fluid chemistry from the Second Gas Hydrate Drilling Expedition in the Ulleung Basin (UBGH2): Source, mechanisms and consequences of fluid freshening in the central part of the Ulleung Basin, East Sea

“…may have been created from a hotter than normal mantle temperature (Kim et al, 1998(Kim et al, , 2007aLee et al, 2001;Cho et al, 2004;Horozal et al, 2009). It is also possible that intrusions of volcanic sills complexes occurred after the emplacement of acoustic basement in this basin, even as recent the middle Miocene (e.g., Chough and Lee, 1992;Cho et al, 2004;Kim et al, 2007a). Using the regional geothermal gradient of 76 C/km, the onset of smectite-to-illite transformation is predicted to occur at w800 mbsf, Figure 9.…”

“…Distribution maps of A) freshening ratios relative to seawater calculated from Cl À concentration, B) temperature estimated using the Mg 2þ eLi þ geothermometer of Fouillac and Michard (1981), C) deuterium isotopic composition (dD), and D) potassium concentration in deep fluids in the Ulleung Basin. may have been created from a hotter than normal mantle temperature (Kim et al, 1998(Kim et al, , 2007aLee et al, 2001;Cho et al, 2004;Horozal et al, 2009). It is also possible that intrusions of volcanic sills complexes occurred after the emplacement of acoustic basement in this basin, even as recent the middle Miocene (e.g., Chough and Lee, 1992;Cho et al, 2004;Kim et al, 2007a).…”

Lithofacies and architecture of a basinwide tuff unit in the Miocene Eoil Basin, SE Korea: Modes of pyroclastic sedimentation, changes in eruption style, and implications for basin configuration

“…1). They were produced in association with north-northwestsouth-southeast spreading of the East Sea (Sea of Japan) during the early to middle Miocene, involving east-west or northwest-southeast extension in an overall dextral strike-slip stress regime (Son, 1998;Kim et al, 2007). Most of these basins, including the Eoil Basin, were rifted during the early Miocene and fi lled by kilometer-thick successions of nonmarine to shallow-marine sediments together with abundant dacitic and basaltic volcanic deposits (Bahk and Chough, 1996;Son et al, 2000Son et al, , 2005, whereas the rest were extended further until the middle Miocene, when they were eventually fi lled by deep-marine sediments (Sohn et al, 2001;Sohn and Son, 2004 The Eoil Basin is one of the early Miocene basins, and it is ~12 km long and 5 km wide (Fig.…”