금강 중류 하상 퇴적층의 기원과 형성시기 및 퇴적율 = Origin, Age and Sedimentation Rate of Mid-Geum River Sediments

국문 초록 (Abstract)

금강의 지류인 유구천과 정안천은 공주시 일대에서 금강 본류에 합류하는데 금강 중류는 현하상과 구하상에 모래를 많이 포함하는 하천 퇴적물이 널리 분포하고 있다. 금강 중류유역에서는 풍화에 상대적으로 약한 중생대의 화강암이 주요한 기반암이지만 금강 상류로 갈수록 풍화에 강한 선캠브리아기의 편마암이 기반암을 형성한다. 하천퇴적물의 주요 기원암은 연구지역 일대의 유구천과 정안천 하류를 포함하는 금강 중류수계 주변에 분포하는 선캠브리아기의 편마암과 중생대의 화강암이며, 석영과 장석이 우세한 특징을 보인다. 금강중류에 분포하는 조립질 퇴적물은 기후가 온난 다습해지는 기후조건하에서 강우량 증가에 따라 하상을 따라 운반된 퇴적물과 금강 본류와 지류들의 합류부 주변에서 조성된 범람환경하에서 형성되었다. $^{14}C$ 연대분석을 통하여 금강중류 유역의 가장 오래된 니질퇴적층의 연대가 약 9,430 yr BP임을 확인하였으며, 이에 따라 더 하부에 분포하는 사질퇴적층은 플라이스토세말에서 홀로세 초기에 퇴적된 것으로 판단된다. 그러나 대부분 현하상에 분포하는 퇴적층은 3,000-6,000 yr BP로 나타나며, 이는 그 형성시기가 홀로세 중기와 그 이후로서 기후변화로 인해 여름몬순(summer monsoon) 이 강하게 작용했던 시기이다. 금강중류의 하상과 범람원 퇴적층의 퇴적율을 보면, 하상사질층은 KJ-29 시추공에서 0.12 cm/yr-0.16 cm/yr, KJ-28 시추공의 범람원 퇴적층은 0.02 cm/yr-0.09 cm/yr로 각각 산정되었으며, 범람원보다 현하상에 가까울수록 퇴적율이 높게 나타났다.

다국어 초록 (Multilingual Abstract)

Fluvial sediments are widely distributed in present and old river-beds of the mid-Keum River, the tributaries of which are the Yugu and Jeongan Rivers. The basement of the mid-Keum River area consists of Mesozoic granites which are easily eroded compared to Precambrian gneisses, which are exposed in the upper-Keum River area. The provenance of the fluvial sediments includes both the Precambrian gneisses and Mesozoic granites, which occur in the catchment of the mid-Keum River. The coarse-grained sediments were probably transported from the river-beds and the overbank floodings of the main Keum River and its tributaries when the climate was warm and wet. The oldest mud deposits were dated at ca. 9,400 yr BP by the radiocarbon method. It has been estimated that the sand deposits below the dated muds were formed in a period from the Late Pleistocene to the Early Holocene. However we have revealed that the major part of the present river-bed sediments was formed at ca. 3,000-6,000 yr BP, i.e., in the mid- to late Holocene, when summer monsoon was very strong due to climatic changes. We have calculated fluvial sedimentation rates of 0.12-0.16 cm/yr and 0.02-0.09 cm/yr for borehole KJ-29 river-bed sediments and borehole KJ-28 floodplain deposits, respectively. We conclude that the sedimentation rate is higher near the present stream channel than near the floodplain.

참고문헌 (Reference)

1 Oh, K.C., "assessment of the sand resources in old riverbeds and flood plain deposits within a branch of the Geum River, South Korea" 176 (176): 156-171, 2008

2 Williams, M.A.J., "River response to Quaternary climatic fluctuations: evidence from the Son and Belan valleys, north-central India" 25 : 2619-2631, 2006

3 Kim, J.Y., "Quaternary geology and assessment of aggregate resources of Korea for the national industrial resources exploration and development" 82 : 87-100, 2001

4 Ryu, E., "Paleoenvironmental studies of the Korean peninsula inferred from diatom assemblages" 176 (176): 36-45, 2008

5 Yi, S., "Mid- and Late-Holocene palynofloral environmental change of Korean central region" 176 (176): 112-120, 2008

6 Srivastava, P., "Luminescence chronology of incision and channel pattern changes in the River Ganga, India" 51 : 259-268, 2003

7 Vital, H., "Lowermost Amazon River: evidence of late Quaternary sea-level fluctuations in a complex hydrodynamic system" 72 : 53-60, 2000

8 Nahm, W.H., "Late Quaternary stratigraphy of the Yeongsan Estuary, Southwestern Korea" 176 (176): 13-24, 2008

9 Zong, Y., "Late Quaternary environmental changes in the Pearl River mouth region, China" 206 : 35-45, 2009

10 Hanson, P.R., "Late Holocene dune activity in the Eastern Platte River Valley, Nebraska" 103 : 555-561, 2009

11 Pratt-Sitaula, B., "Landscape disequilibrium on 1000-10000 year scales Marsyandi River, Nepal, central Himalaya" 58 : 223-241, 2004

12 Huang, C.C., "Impact of monsoonal climatic change on Holocene overbank flooding along Sushui River, middle reach of the Yellow River, China" 26 : 2247-2264, 2007

13 Yang, D.Y., "Holocene wetland environmental change based on major element concentrations and organic contents from the Cheollipo coast, Korea" 176 (176): 143-155, 2008

14 Yum, J.G., "Holocene evolution of the outer lake of Hwajinpo Lagoon on the eastern coast of Korea : Environmental changes with Holocene sea-level fluctuation of the East Sea(Sea of Japan)" 46 : 797-808, 2004

15 Gingele, F.X., "Holocene climatic optimum in southwest Africa-Evidence from the marine clay mineral record" 122 : 77-87, 1996

16 Kroonenberg, S.B., "Geochemistry of Quaternary fluvial sands from different tectonic regimes" 28-, 1990

17 Liu, J.P., "Flux and fate of Yangtze River sediment delivered to the East China Sea" 85 : 208-224, 2007

18 Knox, J.C., "Floodplain sedimentation in the Upper Mississippi Valley: Natural versus human accelerated" 79 : 286-310, 2006

19 Brooks, G.R., "Floodplain Chronology and Vertical Sedimentation Rates Along the Red River, Southern Manitoba" 56 : 171-180, 2002

20 Eitel, B., "Environmental changes at the eastern Namib Desert margin before and after the Last Glacial Maxium: New evidence from fluvial deposits in the upper Hoanib River catchment, northwestern Namibia" 234 : 201-222, 2006

21 Srivastava, P., "Depositional environment and OSL chronology of the Homeb site deposits, Kuiseb River, Namibia" 65 : 478-491, 2006

22 Lair, G.J., "Dating of soil layers in a young floodplain using iron oxide crystallinity" 4 : 260-266, 2009

23 Li, Z., "Climate change and human impact on the Song Hong (Red River) Delta, Vietnam, during the Holocene" 144 : 4-28, 2006

24 KIGAM, "Aggregate Resources Investigation(Naju Area)" KIGAM Research 2009

25 KIGAM, "Aggregate Resources Investigation (Yengi and Muan Areaa)" KIGAM Research 2008

26 KIGAM, "Aggregate Resources Investigation (Gongju and Wanju Areas)" KIGAM Research 2007

27 Colls, A.E., "Age limits on the Late Quaternary evolution of the upper Loire River" 20 : 743-750, 2001