Coastal switching of dominant depositional processes driven by decreasing rates of Holocene sea-level rise along the macrotidal coast of Gochang, SW Korea

Abstract

Decreasing rates of eustatic sea-level rise during the Holocene accompanied the deposition of transgressive coastal deposits worldwide. However, unraveling how transgressive deposition varies in response to different rates of relative sea-level (RSL) rise is limited by the scarcity of long (10+ m) well-dated cores spanning the entire middle to late Holocene record along macrotidal coasts. To investigate the sedimentary response of this macrotidal coast to decreasing rates of RSL rise, we acquired four cores up to 32 m in length and Chirp seismic profiles along the west coast of Korea. Core sediments were analyzed in terms of sedimentary texture, structure, and facies. Nineteen optically stimulated luminescence (OSL) and fourteen 14C accelerated mass spectrometry (AMS) ages constrain the timing of deposition of the sandy sediments. This relatively dense distribution of ages is used to determine how deposition rates changed through time. We also use a compilation of previously published RSL indices for the southwestern Korean coast in order to better constrain RSL changes through time. Results show that the evolution of the Gochang coastline switched from a tide-dominated environment to a wave-dominated environment during the latter stage of transgression as the rate of the sea-level rise decreased. Rugged antecedent topography likely led to the development of tidal currents and the formation of a tide-dominated tidal flat during rapid RSL rise from 10 to 6 ka. As the tidal channels filled with fine-grained sediments from 6 to 1 ka, tidal amplification likely waned leading to a greater role of wave energy in shaping the formation of the sandy open-coast tidal flat. Since 1 ka, wave-dominated environments formed sand-rich tidal beaches and flats. Decreasing changes in rates of the RSL rise resulted in changes in depositional environments from a tide-dominated intertidal flat to an open-coast tidal flat and finally a wave-dominated tidal beach. This study highlights the important role that rates of RSL rise play on not only sedimentation rates in a shelf setting but also playing a role in the switch from a tide-dominated to a wave-dominated setting.

Distribution, Preservation Characteristics of Land and River Natural Aggregates in Nonsan City, Korea

“…골재는 연간 약 1억5천만㎥, 중량으로는 약 2억4 천만ton 내외의 막대한 양이 주택건설, 토목, 도로 등의 건설사업에 사용되며 사용량이 점차 증가하는 추세이다 (Hong and Lee, 2021). (Kim et al, 1999;Yang et al, 2006;Chang et al, 2014;Yoon et al, 2023). 큰 하천은 육상에서 공급되는 퇴적물을 연안으로 공급하는 통로이기도 하지만 조석의 영향이 큰 지역에서는 바다의 조석에 의해 부유된 퇴적 물을 육상 지역으로 공급하는 역할을 하기도 한다 (Klein, 1985).…”