Origin and Evolution of Stacked Cut-and-fill Structures On the Southwestern Margin of the Ulleung Basin, East Sea (Japan Sea)

Abstract

Multichannel seismic reflection profiles and well data were analyzed to unravel the origin and depositional history of stacked cut-and-fill structures (CF) in the southwestern margin of the Ulleung Basin, East Sea. The CFs in a syn-compressional megasequence are characterized by discontinuous, low-amplitude, chaotic, and transparent seismic reflections. They display both U-shaped and V-shaped morphologies along their lengths. The CFs are thickest and widest at the shelf edge and taper both landward and basinward. Based on the stratigraphic position, the CFs are found in three depositional sequences (DS8–DS10). Thirty CFs have been identified that range from 0.5 to 8.8 km in width and 58 to 453 m in thickness (assuming a 2000 m/s seismic velocity of the sediments). The larger and numerous CFs occurred in the middle depositional sequence. Seismic characteristics, spatial distribution, hundred-meter-scale incisions, and high gamma-ray responses indicate that the CFs were caused by submarine canyons. During the period of DS8, small CFs were formed locally on the shelf margin, and were little influenced by the deformation of the thrust-fold (Dolgorae Thrust Belt). Extensive and numerous CFs in DS9 developed in the oversteepened shelf margin, where uplift of both the thrust-fold and anticline (Gorae V structure) occurred simultaneously, and where a large volume of sediment was supplied. During the period of DS10, a general decreasing pattern in the occurrence and dimensions of the CFs resulted from waning tectonic activity of the thrust-fold that reduced sediment supply. Consequently, this study suggests that variation in contractional tectonic activity and sediment supply, associated with the back-arc closure of the East Sea, mainly controlled the evolution of the CFs rather than eustasy.

Tectonic control on mass‐transport deposit and canyon‐fed fan system in the Ulleung Basin, East Sea (Sea of Japan)

“…In the southwestern margin of the Ullueng Basin, many stacked ancient canyons occur in the margin and are filled with discontinuous transparent and low-amplitude reflections (Figure 4b). Park et al (2019) interpreted that these submarine canyons were mainly triggered by Gorae V structure-induced shelf oversteepening. In the dip-orientated seismic section, the internal seismic patterns of stacked canyons are characterised by outbuildings of oblique progradational configurations with toplap and stepwise morphologies at the canyon base (Figure 8a).…”

“…The DLCs were mainly fed by Late Miocene shelfincised canyons and slope channels during tectonic uplift of the Gorae V structure on the shelf (Figure 13c). At that time, retrogradational slumping created numerous large-scale canyons in the tectonically oversteepened shelf around the Gorae V structure (Figures 4, 8a, and 13c; Park et al, 2019). Park et al (2019) reported that palaeocanyons in the basin incise the shelf up to 24 km landward and are up to 8.8 km wide and 453 m thick.…”

“…At that time, retrogradational slumping created numerous large-scale canyons in the tectonically oversteepened shelf around the Gorae V structure (Figures 4, 8a, and 13c; Park et al, 2019). Park et al (2019) reported that palaeocanyons in the basin incise the shelf up to 24 km landward and are up to 8.8 km wide and 453 m thick. These results suggested that recurrent canyon wall slumping and collapse created numerous turbidity flows and could be one of the origins of slope channels and DLCs from the slope to the basin floor (Figure 13c).…”

“…(b) Correlation of the lithostratigraphy from the drilled well Dolgorae-I and seismic data. Seismic stratigraphic interpretation is from Lee and Kim (2002), Park et al (2019), and Kim et al (2020). The lithologic and biostratigraphic data are from Korea Institute of Energy and Resources (1982) and Lee (1994)…”

“…siliciclastic sediment(Figure 3b). Based on previous biostratigraphic and seismic studies, the age of SU1 corresponds to early-middle Late Miocene(Lee & Kim, 2002;Lee, 1994;Park et al, 2019).…”