Holocene coastal landforms and Quaternary sea level flucutations

Coastal landforms are routinely used as “Sea Level Index Points” (SLIP). Among those, owing to their outstanding morphologies, stacks of Quaternary coral reefs are most noticeable. Yet, on top of sea level fluctuations, their morphogenesis is indiscriminately affected by vertical land motion and biological factors. Deciphering their respective influence requires understanding the morphogenesis of individual landforms within their sequences. Here we numerically model the morphogenesis of Quaternary coastal landforms to explore the sensitivity of the morphology of individual terraces to earlier sea-level fluctuations, but also tectonics and biological factors. We focus on Holocene terraces, show that their morphologies depend at first order on vertical land motion, and identify a series of regimes that depend on the morphogenesis of earlier reef units. Biological properties of reef growth mostly modulate the general pattern, albeit occasionally triggering alternative morphogenetic behaviors. Regarding the potential use of landforms as “SLIP”, predictions with different sea level curves reveal that Holocene landforms are sensitive to sea level fluctuations to a lesser extent than to vertical land motion. Last, we extrude our analysis to earlier interglacials, revealing how the morphologies of earlier coral reefs may differ from their modern/Holocene analogues.