Subsidence of the Japan Sea: Stratigraphic Evidence from ODP Sites and Onshore Sections

Abstract

Abundant geologic, geophysical, and paleontologic evidence from ODP drilling in the Japan Sea and from adjacent continental and insular areas demonstrates that the sea has evolved rapidly over the past 32 m.y. and is now in an early stage of compressive destruction. Stratigraphic, geochronologic, and paleobathymetric data derived from ODP Sites 794, 795, 796,797, 798, and 799, offshore exploration wells, and uplifted and deformed Neogene stratigraphic sections exposed on the Korean Peninsula and the islands of Honshu, Hokkaido, and Sakhalin were used to analyze the timing and patterns of backarc subsidence characterizing each stage in the evolution of the Japan Sea. An extensional tectonic regime and subsidence dominate backarc evolution ca. 32 Ma to 10 Ma at which time regional uplift was initiated marking the onset of a compressional regime that continues to the present. Backstripping techniques were applied to five Neogene stratigraphic columns in contrasting depositional, crustal, and tectonic settings to derive estimates of variations in rates of total and tectonically driven subsidence, presumably reflecting fundamental changes in crustal behavior during backarc evolution. The five Neogene sequences analyzed include; (1) the Pohang onshore section on the southeastern Korean Peninsula, (2) the Dolgorae-1 offshore well in the southern Tsushima Basin, (3) the Oga Peninsula onshore section in northwestern Honshu, (4) ODP Site 794 at the juncture between the Japan and Yamato basins, and (5) the southern Sakhalin onshore section representing the northern margin of the Japan Sea. Initial rifting, extension, and thermal subsidence in the Japan Sea region commenced in late Oligocene time (ca. 32-25 Ma) at rates of < 150 m/m.y. accompanied by widespread deposition of non-marine sediment and volcanic units and probable early spreading in the Japan Basin. A period of accelerating subsidence (100-500 m/m.y.), backarc spreading, rift propagation, massive basaltic magmatism, and crustal extension began in the early Miocene ca. 24-23 Ma culminating in subsidence of the Japan, Yamato, and Tsushima basins to near their present depths (2-3 km) by 20-18 Ma. Slow subsidence persisted from 18 Ma to 16-15 Ma when a second episode of rapid subsidence occurred as rifts propagated into the arc, arc-flanks, and other areas of weakened continental crust around the perimeter of the sea creating numerous sub-basins accompanied by middle Miocene rotation of southwest Japan and a second pulse of basaltic magmatism. Maximum rates of tectonic subsidence during middle Miocene sub-basin formation exceeded 900 m/m.y. pointing to a pull-apart origin for these features which were initially sediment-starved and filled with pelagic and hemipelagic diatomaceous muds. Relatively low rates of subsidence (<200 m/m.y.) characterize the tectonically quiescent middle-late Miocene stage in the evolution of the sea from 12.5 to 10 Ma. Evidence of initial regional uplift (10-100 m/m.y.) appears in the southern Japan Sea ca. 11-10 Ma with compressional uplif...

Two Distinct Back-Arc Closure Phases of the East Sea: Stratigraphic Evidence From the SW Ulleung Basin Margin

“…The sea comprises three sedimentary basins, namely the Japan, Yamato, and Ulleung basins, that are demarcated by three topographic highs, namely the Korea Plateau, the Yamato Rise, and the Oki Bank (Figure 1A). It is broadly accepted that the back-arc extension of the East Sea was initiated at the Early Oligocene (c. 32 Ma) (Tamaki, 1986;Ingle, 1992). Lallemand and Jolivet (1986) proposed that two dextral shear zones along the eastern and western margins of the sea guided the pull-apart style back-arc opening.…”

“…The reconstruction of the subsidence history from the ODP Leg 127/ 128 suggests that the clockwise rotation of the southwestern Japanese islands ceased in the late Middle Miocene (c. 12 Ma). Thereafter, the entire East Sea subsided slowly by the thermal contraction of the back-arc lithosphere until the onset of the post-Miocene neotectonic phase of the sea (Ingle, 1992;Jolivet and Tamaki, 1992;Taira, 2001).…”

Discovery of Ancient Volcanoes in the Okhotsk Sea (Russia): New Constraints on the Opening History of the Kurile Back Arc Basin

“…Deep-sea drilling in the basins of the Japan Sea has provided accurate data about the composition and age of the crust. Based on these data the evolution of these basins has been constrained from 25 Ma to the present (Jolivet and Tamaki 1992;Ingle 1992 [76,77]). Active spreading in the Japan Basins began in the Early Miocene and ended 5-10 My.…”

Impact of SO2 on Alteration of Reservoir Rock with Ca-Deficient Conditions and Poor Buffering Capacity under a CO2 Geologic Storage Condition

“…Pohang Basin is one of the Cenozoic sedimentary basins which formed during back-arc spreading of the East Sea in the early Miocene [18][19][20]. The basin is bounded by a set of NNE-trending border faults in the west and opens towards the east.…”