Holocene relative sea-level change along the tectonically active Chilean coast

Abstract

We present a comprehensive relative sea-level (RSL) database for north, central, and south-central Chile (18.5 S e 43.6 S) using a consistent, systematic, and internationally comparable approach. Despite its latitudinal extent, this coastline has received little rigorous or systematic attention and details of its RSL history remain largely unexplored. To address this knowledge gap, we re-evaluate the geological context and age of previously published sea-level indicators, providing 78 index points and 84 marine or terrestrial limiting points spanning from 11 ka to the present day. Many data points were originally collected for research in other fields and have not previously been examined for the information they provide on sea-level change. Additionally, we describe new sea-level data from four sites located between the Gulf of Arauco and Valdivia. By compiling RSL histories for 11 different regions, we summarise current knowledge of Chilean RSL. These histories indicate mid Holocene sea levels above present in all regions, but at highly contrasting elevations from~30 m to <5 m. We compare the spatiotemporal distribution of sea-level data points with a suite of glacial isostatic adjustment models and place firstorder constraints on the influence of tectonic processes over 10 3 e10 4 year timescales. While seven regions indicate uplift rates <1 m ka À1 , the remaining regions may experience substantially higher rates. In addition to enabling discussion of the factors driving sea-level change, our compilation provides a resource to assist attempts to understand the distribution of archaeological, palaeoclimatic, and palaeoseismic evidence in the coastal zone and highlights directions for future sea-level research in Chile.

Seismo‐Turbidites in Aysén Fjord (Southern Chile) Reveal a Complex Pattern of Rupture Modes Along the 1960 Megathrust Earthquake Segment

“…This shows that steady propagation of the Aysén River Delta must have been occurring at least since ~5 ka and probably already sooner. Additionally, after a rapid Early‐Holocene sea level rise following deglaciation, relative sea level in southern Chile has shown a relatively stable decline since ~7 ka (Dura et al, 2016; Garrett et al, 2020). Therefore, the time window in which a stable turbidite‐based paleoseismic record can be obtained is limited to the last 7,000 years.…”

Did a 3800-year-old M w ~9.5 earthquake trigger major social disruption in the Atacama Desert?

“…Taking into account the maximum inferred elevation of global sea level during the Early and Mid-Holocene ( 31 ), and that it was higher than contemporary levels according to regional models ( 32 ), our field observations provide evidence for coastal uplift along the major northern Chile seismic gap since the Late Holocene ( Figs. 1D and 2A ).…”

The giant 1960 tsunami in the context of a 6000‐year record of paleotsunamis and coastal evolution in south‐central Chile

“…Under this scenario, we interpret the grey sand in Stratigraphic Zone #3 throughout Queule as having been deposited in an open shallow marine embayment, probably from the early Holocene (Figure 8, Time 1). Stratigraphic Zone #2 represents shallow sub-tidal and tidal marsh sediment older than 6000 years BP, during and immediately after the sea-level high stand (Figure 8; Dura et al, 2016;Garrett et al, 2020).…”

“…The deposition from a tsunami depends on multiple, often interconnected factors, including: (1) tsunami height; (2) site exposure to inundation; (3) sediment availability; (4) preservation potential of deposits; (5) changes in relative sea level (RSL) in the Holocene; and (6) geomorphic evolution of the coast (Dura et al, 2016; Szczuciński, 2012). Although these factors pose challenges for reconstructing events at individual sites, multiple sites with independent earthquake histories can help constrain the locations and timing of source earthquakes and increase understanding of the role of the geomorphic evolution of the coast (Garrett et al, 2020; Nelson et al, 2021; Philibosian & Meltzner, 2020; Sawai, 2020; Shennan et al, 2014).…”