하남시 일대 한강 하류 하천 퇴적층의 연구 2 - 퇴적층의 층서에 대한 고찰 -

Abstract

Valley floor sediments from the Pungsan land development area of Hanam, east of Seoul, provide evidence depositional conditions of lower Han River during Pleistocene and Holocene. Based on the results from boring core data set, 4 different geomorphic zones are recognized. Hilly area around the floodplain is classified as weathering-denudation dominant zone, which has little evidence of fluvial deposition. Tors are found from the top of the hill and most of area is covered with reddish soil and saprolites. These materials are in-situ weathered things. Valley fill deposits between the hills are also found. this sedimentary units has no fluvitile gravels at the bottom or middle of sedimentary body. Most of flood plain area has basal gravel layer covers weathered basal surface. It means this zone experienced the period of bedrock river and transit to gravel bed river, so this area classified as fluvial terrace zone. There is a transition zone between the area of gravel (typical terrace deposits) and the area of valley fill deposit. In-situ weathered basal surface found from 0-10m from current mean sea level. This result is supported from the drilling results from Paldang bridge construction sites. Up to 5m thick sand layer overlays the gravel layer. The burial age of this sand layer determined as 59±3.6ka BP with OSL dating. It can be interpreted that this layer deposited during MIS 3 and there was only limited effect of sea level changes on sedimentary environment during the last glacial period in this area. Clays and silts are main forming materials of the upper most part of deposits. There are imbedded peat layers within this layer, but spatial pattern of peat deposits should be investigated in detail as a further research. The age of each peat layers will be measured with proper measurement methods, including 14C. The pollen and diatom analysis also will be performed to reconstruct the climate after 59±3.6 ka BP.