3:45 PM - 4:00 PM
[SCG57-30] Modeling and simulation for the development of Holocene marine terraces in the Boso peninsula
Keywords:Marine terrace, Sea level change, Steady land uplift, Erosion, Deposition
The evolution of coastal landscape can be described by the following conceptual equation: altitude change = - erosion + deposition + land uplift - sea-level rise. In modeling sea-land interaction at shore, we supposed that the erosion rate is proportional to the dissipation rate of wave energy (Anderson et al., 1999), and the deposition rate of the floating materials produced by erosion decays exponentially as they are transported seaward. In the numerical simulation of Holocene marine terraces in the southern Boso peninsula, we used the steady uplift rate (1-4 mm/yr) due to plate subduction (Hashimoto et al., 2004). For the Holocene sea-level changes, we used a fluctuation curve obtained from the time series data of mean sea-level altitudes based on deep-sea oxygen isotope ratios (Siddall, et al., 2003) by fitting with cubic B-splines.
A set of sea cliff and shore platform is rapidly formed about a stationary point of the sea-level fluctuation curve. The Holocene sea-level fluctuation curve (from 10 kyrBP to the present) has seven stationary points, and so basically seven marine terraces are formed one by one over the period. In the case of low uplift rate, however, most of older terraces sink beneath the present sea level, and so we cannot observe them. Even in the case of high uplift rate, the relationship between the age and the present altitude of terraces is not simple, because the overlap and/or reverse of older and younger terraces occur frequently. Endo and Miyauchi (JSAF 2011 Fall Meeting, Abstracts, P-06) have confirmed such complexity through the reexamination in ages and altitudes of Holocene emergent coastal geomorphology in the southern Boso peninsula. In the present numerical simulation, taking the uplift rate to be 3-4 mm/yr, we obtained four well-developed marine terraces, corresponding to the Numa I-IV terraces. Even in this case, it should be noticed that the highest terrace is not the oldest terrace.