Use of high-resolution seismic reflection data for paleogeographical reconstruction of shallow Lake Yamanaka (Fuji Five Lakes, Japan)

Abstract

High-resolution seismic profiles, combined with the integration of published drilling data, provide a detailed paleoenvironmental history of Lake Yamanaka (Fuji Five Lakes, Japan). This study presents a detailed analysis of the different depositional stages of the area currently occupied by Lake Yamanaka (floodplain wetland, river and lake). From ca. 5500 cal yr BP to ca. 5050 cal yr BP, the Yamanaka basin was occupied by floodplain wetlands. During that period, the landscape was very stable and erosion on northeastern flank of Mt. Fuji was relatively limited. From ca. 5050 cal yr BP to ca. 3050 cal yr BP, the water level increased and the floodplain wetlands became a lake. From ca. 3050 cal yr BP to ca. 2050 cal yr BP, the water level progressively decreased, leading to a reduction in lake extent. During this lowering of the lake's water level, a 1 km 2 mass-transport deposit modified the physiography of the lake floor. From ca. 2050 cal yr BP to ca. 1050 cal yr BP, the lake disappeared and a river flowing towards the northwest occupied the depression. Ponds occupied morphological lows formed by masstransport deposits. From ca. 1050 cal yr BP to the present day, the lake water level rose again, connecting the ponds with the main lake. Since then, the lake water level has continued to rise to the current level. Lake water level fluctuations are the results of several factors that could be interconnected: (i) changes in precipitation rates; (ii) margin destabilization (the Yamanaka mass-transport deposit), (iii) changes in river inlets and therefore variation in water supplies, (iv) volcanic eruptions (scoria fallout and lava flows) and (v) changes in vegetation cover. This study highlights the importance of coupling sediment cores and high-resolution seismic reflection profiling to identify lateral variation and modification of sedimentary inputs through time.

Late Holocene Changes in Erosion Patterns in a Lacustrine Environment: Landscape Stabilization by Volcanic Activity Versus Human Activity

“…The absence of OM and silt intercalated within the scoria deposits suggest that the scoria has not been reworked. The primary deposit nature is also supported by high‐resolution seismic reflection profiling where the Hōei scoria deposits appear as undisturbed and continuous strong reflective horizons (Lamair et al, ). The boundary between unit D and unit C is defined by a change in lithology (from scoria to lacustrine sediments).…”

Understanding Wetlands Stratigraphy: Geophysics and Soil Parameters for Investigating Ancient Basin Development at Lake Duvensee

“…The application of seismics for geoarchaeological research is not widespread but has lately been intensified due to exemplary results [23,[42][43][44][45][46][47][48]. SH-wave seismics are directly sensitive to the rigidity of soil layers and are capable of resolving stratigraphic interfaces at much larger depths than GPR [42,49]. SH-wave sounding can identify and differentiate soft soils such as fine-grained lake sediments or swampy organic deposits [23], which are characterized by slow seismic velocities.…”