Environmental regime change at around 500Â BCE found in sediment cores from Lake Yogo, Japan: Possible impact of agricultural use

- This study analyzed sediment core from Lake Yogo, Japan.
- The hydrological regime shift occurred at around 2500 years ago in this region.
- The development of agricultural land use may be responsible for this shift.
- Trace of a disastrous event at 1600-1700 years ago is also identified.

Lake sediments record past environmental changes. Mineral grain size fluctuations found in sediment cores from the deepest basin of Lake Yogo, located north of Lake Biwa, are a good proxy for annual precipitation back to about 700 CE, when a hydrological regime shift is postulated. This study reports water, organic matter and biogenic silica contents and grain size for an additional core from Lake Yogo and together with a detailed chronological study published elsewhere, a new age model is established. Based on this new age model, we propose that the hydrological regime shift occurred about 2500 years ago. Agricultural use of the catchment area might be responsible for this regime shift, and resulted in the large overall average grain size. Several traces of disastrous events, possibly caused by earthquakes in the region, are also found in the core.