Tectonic and wave controls on the generation and preservation of marine terraces

• Applicants: Dr. Luca Malatesta; Professorin Dr. Sumiko Tsukamoto
• Subject Area: Geology
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 524080107

The coastal landscapes of tectonically active regions are shaped by the cumulative work of wave erosion during the glacial-interglacial sea level seesaw and by rock uplift progressively moving formerly submerged land out of the sea. In these landscapes, marine terraces provide the opportunity to constrain when the sea last occupied that datum and how high it has been uplifted since. Successive terraces are commonly tied to successive past sea level high stands despite recent evidence that the cumulative work of wave erosion can efficiently dissociate the two. We seek to develop an understanding of coastal topography - beyond discrete well-defined terraces - that yields a greater amount of information about rock uplift rate and past sea levels than prior approaches focused on attributing high stand ages to unique terraces. For this we propose to establish a mechanistic relationship between the environmental constraints controlling the efficiency of wave erosion and the resulting coastal topography. To do so, we will rely on an extraordinary field site in Central Japan: the Noto Peninsula and neighboring Sado Island. Preliminary work shows that the power of waves reaching the coast covers 2 orders of magnitude and rock uplift rate varies from 0.15 to 1.3 mm/yr. Well preserved flights of marine terrace reaching back to 1 Ma lie close to steep coasts devoid of any terraces. The diversity in marine terrace distribution and abundance at these sites (and eventually the world’s) can be captured in a phase space that is a function of the erosive driver (erosional efficiency of waves) and the preserving driver (rock uplift transporting terraces up and away from further erosion). The essential processes driving the phase space will be captured in a numerical model for wave erosion and landscape evolution. The numerical model will rely on two autonomous research topics themselves. First, an extensive morphological study tracking the distribution and geometric attributes of terraces as a function of varying rock uplift rates and of changing wave power at the field sites. This will allow an unprecedented inspection of the isolated effect of variations of key driving variables on the resulting coastal topography. Second, we will sample terrace deposits for luminescence and cosmogenic radionuclide dating in order to verify and constrain the precise chronology of a terrace series that is supposedly as old as ~1.03 Ma. This would make this site one of the world’s most detailed and extensive record of past sea level in erosive terraces. The numerical model and the associated phase space can be used for forward predictions and to retrieve tectonic and sea level information from existing landscapes in an inverse exercise. Having a master model linking environmental conditions and resulting topography will move the community beyond the punctual use of discrete marine terraces.

• DFG Programme: Research Grants
• International Connection: Japan
• Cooperation Partners: Professor Dr. Yuki Matsushi; Dr. Shigeru Sueoka