HR: 17:30h
AN: H44D-07    [Abstracts]
TI: Fluvial stratigraphy and palaeoenvironments of River Han: Preliminary results from Hanam, Korea
AU: * Kim, J
EM: jkimglasgow@hotmail.com
AU: Kim, J
H44D-07 AU: Yang, D
H44D-07 AU: Rhee, S
H44D-07 AB: Valley floor sediments from the Pungsan land development area of Hanam, east of Seoul, provide evidence for Pleistocene and Holocene floodplain conditions of lower Han River. Two terrace surfaces are present in studied area. The upper terrace (30m above current channel bed) has been regarded as remnant of dissected pediment. However, it should be mentioned that severely weathered fluvial sediment particles were found from the top of the hill. So, theses features could be originated from fluvial action rather than other processes. The lower terrace, alluvial deposits, has been thought to be formed during the Pleistocene. Using 125 boring core samples, fluvial stratigraphy of the area is reconstructed and a 3 dimensional map is presented. In situ weathered basal surface found from 0-10m from current mean sea level (Stage 1). This weathered layer could be bedrock surface rather than weathered surface when it formed in the time of lower sea level. About 10m thick gravel with sand matrix layer covers the bedrock surface (Stage2). This layer interpreted as channel bed sediment. The thickness of this gravel dominant layer increases northward (towards current river channel). Transition from stage 1 to stage 2 could be related with sea level rising. Up to 5m thick sand layer overlays the gravel layer (Stage 3). The change from the gravel layer to sand layer is abrupt rather than gradual. This change could happen with channel shifting northward. The colour of the sand deposits is dark brown to brown when it overlays thick gravel layer (up to 10m), but greenish grey to grey when it covers weathered bedrock surface or thin (up to 2m) gravel deposits. Upper most part of deposits consists with clay and silt (up to 7m in thickness). Peat layers imbedded in this layer with various thickness. Physical characteristics of greenish grey silt and clay deposits similar with marine sediments found from the coast of Yellow sea. It is too early to say the origin of these deposits but further chemical and biological analysis will provide better information on the origin. The age of each layer will be measured with proper measurement methods, including 14C and OSL. Results from pollen and diatom analysis also will be performed to reconstruct the climate of past and changes.
DE: 1105 Quaternary geochronology
DE: 1130 Geomorphological geochronology
DE: 1825 Geomorphology: fluvial (1625)
SC: Hydrology [H]
MN: Fall Meeting 2005