Influence of the middle and later holocen relative sealevel change on the coastal geomorphic evolution along the north eastern Shandong peninsula
WANG Qing (State Key Laboratory of estuarine & Coastal Sediment Dynamics and Morphodynamics, East China Normal University, Shanghai 200062, China)
Based on field work, dating,mapping, historical literature and predecessors' work, this paper has discussed the influence of the middle and later Holocene relative sealevel change on the coastal geomorphic evolution along the northeastern Shandong peninsula which stretches from Longkou to Shidao. Along the northeastern Shandong Peninsula, many large sized coastal deposition geomorphic bodies were developed, among which the Qimudao tombolo in Longkou city, Zhifudao tombolo in Yantai city and Shidao bay mouth barrier in Rongcheng city are the biggest in size and most typical in form. Among the three barriers above, which were formed in differeent physical geographic and geologic settings, there is not only remarkable difference in genetic type, barrier platform and sediment resource, but also difference in landfrom and deposition features. According to the analysis on the difference above, it is concluded that the coastal deposition geomorphic evolution has been deeply influenced by the middle and later Holocene relative sealevel change. The influencing mechanism is that the relative sealevel change results in the adjusting of the tranverse shore profile and longitudinal river-bed profile, then influences the intensity of beach drift and barrier evolution. Since the middle Holocene, there are five relativel change phases which include a static phase (6000～4000aBP), two rising phases (4000～2300aBP,1500～600aBP) and two falling phases(2300～1500aBP,600aBP～present). For the two rising phases, the average rising rates are 2.35mm/yr and 2.22mm/yr,which approach the low limit of the estimated relative sealevel rising rate during 1990～2100 A.D.. Based on the results of this paper, the future global sealevel rise will influence the the coastal geomorphic evolution along the rock mountain coast such as the northeastern Shandong peninsula.