The Ulleung Basin, East Sea/Japan Sea, is a Neogene back-arc basin and occupies a tectonically crucial zone under the influence of relative motions between Eurasian, Pacific and Philippine Sea plates. However, the link between tectonics and sedimentation remains poorly understood in the back-arc Ulleung Basin, as it does in many other back-arc basins as well, because of a paucity of seismic data and controversy over the tectonic history of the basin. This paper presents an integrated tectonostratigraphic and sedimentary evolution in the deepwater Ulleung Basin using 2D multichannel seismic reflection data. The sedimentary succession within the deepwater Ulleung Basin is divided into four second-order seismic megasequences (MS1 to MS4). Detailed seismic stratigraphy interpretation of the four megasequences suggests the depositional history of the deepwater Ulleung Basin occurred in four stages, controlled by tectonic movement, volcanism, and sea-level fluctuations. In Stage 1 (late Oligocene through early Miocene), syn-rift sediment supplied to the basin was restricted to the southern base-of-slope, whereas the northern distal part of the basin was dominated by volcanic sills and lava flows derived from initial rifting-related volcanism. In Stage 2 (late early Miocene through middle Miocene), volcanic extrusion occurred through post-rift, chain volcanism in the earliest time, followed by hemipelagic and turbidite sedimentation in a quiescent open marine setting. In Stage 3 (late middle Miocene through late Miocene), compressional activity was predominant throughout the Ulleung Basin, resulting in regional uplift and sub-aerial erosion/denudation of the southern shelf of the basin, which provided enormous volumes of sediment into the basin through mass transport processes. In Stage 4 (early Pliocene through present), although the degree of tectonic stress decreased significantly, mass movement was still generated by sea-level fluctuations as well as compressional tectonic movement, resulting in stacked mass transport deposits along the southern basin margin. We propose a new depositional history model for the deepwater Ulleung Basin and provide a window into understanding how tectonic, volcanic and eustatic interactions control sedimentation in back-arc basins. 相似文献
Marine Geophysical Research - This study entails the characterization of the depositional environment of the Hupo Basin shelf. By means of sedimentary structure analysis, grain size, textures,... 相似文献
High-resolution seismic survey and sediment core sampling were conducted to investigate acoustic characteristics of gas-bearing sediments in Jinhae Bay, the southeast of Korea. The sediment in Jinhae Bay is mostly homogenous mud deposited after the Holocene transgression. Along with the 410 km of chirp seismic profiling, five piston core samples were collected on the track lines. Gassy sediments are common and occur widely in the bay. Core samples were analyzed for sediment texture, physical properties (porosity, water content, bulk density, and grain density), acoustic properties (compressional wave velocity and attenuation), and electrical resistivity. X-radiograph image analysis was also performed to observe the shape of degassing cracks. There is no significant downcore variation on physical and sediment textures regardless of existence of gas bubbles. However, compressional wave velocity dramatically decreases from average 1480 to 1380～739 m/s for the cores that penetrate the gas-bearing zones. This is probably due to degassying cracks that developed by escaping gases and free gas bubbles that are still trapped in the cores. Electrical resistivity is the only geotechnical property that increases in the gas-bearing zone where compressional wave velocity abruptly decreases. This indicates the possibility of using both electrical resistivity as an index variable as well as to compressional wave velocity to identify gassy sediment microstructure because there are little changes in texture and composition of sediment. 相似文献
Analysis of high-resolution seismic reflection profiles and sediment samples has revealed the evolution and sediment budget of the southeastern Yellow Sea mud belt (SEYSM) along the southwestern Korean Peninsula. The SEYSM, up to 50 m thick, over 250 km long and 20–55 km wide, can be divided into three stratigraphic units (A1, A2, and B, from oldest to youngest). Unit A1, overlying the acoustic basement, comprises the northern part of the SEYSM. Unit A2 comprises the southern part of the SEYSM; much of unit A2 is exposed at the seafloor. Unit B completely covers unit A1 and pinches out southward.
14C data suggest that evolution of each unit is closely related to the postglacial sea-level changes. Unit A1 consists of estuarine/deltaic or shallow-water muds deposited during the early to middle stage of postglacial sea-level rise (ca. 14,000–7000 yr B.P.). Unit A2 corresponds to relict muds deposited during the last, deceleration stage of sea-level rise (ca. 7000–3.500 yr B.P.). Unit B consists of shelf muds deposited during the recent sea-level highstand (ca. <3500 yr B.P.).
Very low background activities of 210Pb of the surface sediment of unit A2 suggest that the present-day sediment accumulation is negligible in the southern SEYSM. On the other hand, 210Pb excess activity profiles in unit B yield an average sediment accumulation rate of 3.9 mm/yr, indicating active sediment accumulation in the northern SEYSM. The annual sink (3.0×107tons/yr) of fine-grained sediment in unit B is about an order of magnitude greater than can be explained by the sediment input from the Korean rivers alone. We propose that reworking of unit A2 has provided large volumes of muds to unit B, resulting in excessive sediment accumulation in the northern SEYSM. Much of unit A2, in turn, is likely to have originated from erosion of unit A1 in the north. This rather unique erosional/depositional regime of the SEYSM is probably owing to the tidal and regional currents characteristic in the southeastern Yellow Sea. 相似文献
