TerraceM: A MATLAB® tool to analyze marine and lacustrine terraces using high-resolution topography

Abstract

High-resolution topographic data greatly facilitate the remote identification of geomorphic features, furnishing valuable information concerning surface processes and characterization of reference markers for quantifying tectonic deformation. Marine terraces have been used as long baseline geodetic markers of relative past sea-level positions, reflecting the interplay between vertical crustal movements and sea-level oscillations. Uplift rates may be determined from the terrace age and the elevation of its shoreline angle, a geomorphic feature that can be correlated with past sea-levels positions. A precise definition of the shoreline angle in time and space is essential to obtain reliable uplift rates with coherent spatial correlation. To improve our ability to rapidly assess and map shoreline angles at regional and local scales, we have developed TerraceM, a MATLAB® graphical user interface that allows the shoreline angle and its associated error to be estimated using high-resolution topography. TerraceM uses topographic swath profiles oriented orthogonally to the terrace riser. Four functions are included to analyze the swath profiles and extract the shoreline angle, from both staircase sequences of multiple terraces and rough coasts characterized by eroded remnants of emerged terrace surfaces. The former are measured by outlining the paleocliffs and paleoplatforms and finding their intersection by extrapolating linear regressions, whereas the latter are assessed by automatically detecting peaks of sea-stack tops and back-projecting them to the modern sea cliff. In the absence of rigorous absolute age determinations of marine terraces, their geomorphic age may be estimated using previously published diffusion models. Postprocessing functions are included to obtain first-order statistics of shoreline-angle elevations and their spatial distribution. TerraceM has the ability to process series of profiles from several sites in an efficient and structured workflow. Results may be exported in Google Earth and ESRI shapefile formats. The precision and accuracy of the method have been estimated from a case study at Santa Cruz, California, by comparing TerraceM results with published field measurements. The repeatability was evaluated using multiple measurements made by inexperienced users. TerraceM will improve the efficiency and precision of estimating shoreline-angle elevations in wave-cut terraces in both marine and lacustrine environments.

Rise of the central Andean coast by earthquakes straddling the Moho

“…Marine terraces are formed by retreat of the coastal cliff by wave erosion 51 . They commonly consist of a low-relief surface abrasion platform, the shoreline angle or cliff foot, which marks the past position of mean sea level, and a steep cliff at the back.…”

Lithospheric flexure and rheology determined by climate cycle markers in the Corinth Rift

“…Contours around those surfaces were drawn manually using a combination of satellite imagery, slope maps and hillshade images of the DSM. The slope of the Holocene seacliff was measured at 48 locations and its value ±1σ was used to estimate the horizontal and vertical position of the shoreline angles for ~700 palaeocliffs with TerraceM 56,57 ( Supplementary Figs 2 and 9). To reduce the influence of fluvial and SCIENTIFIC REPORTS | (2019) 9:4260 | https://doi.org/10.1038/s41598-018-36377-1…”

“…gravitational erosion, we used the maximum topography of 100 m-wide swath profiles perpendicular to the cliffs, the size preferred by Jara-Muñoz et al 57 . All swath profile and shoreline angle locations are included as supplementary Google Earth and ESRI Shapefile data files.…”

How do sea-level curves influence modeled marine terrace sequences?

“…To determine shoreline angles, the intersection between the marine terrace and its associated fossil sea-cliff, we used a 2-m resolution Digital Surface Model (DSM) developed from Pleiades satellite imagery (De Gelder et al, 2015. From the DSM we calculated 100-m-wide swath profiles perpendicular to the fossil sea-cliffs and determined the shoreline angle positions and elevations using the fixed-slope method of TerraceM (Jara-Muñoz et al, 2016). We used the maximum swath profile topography and the modern sea-cliff slope angle of 39 ±10 (De Gelder et al, 2019) as a proxy for the slope of the paleo sea-cliff (Dataset S1).…”