Systematic Relaxation of Geomorphic Features: Application on the South East Queensland Dune Fields, Australia
Abstract
Landscapes are built and they are destroyed. These abrupt and chaotic events that create landforms (i.e. orogenic uplift, glaciation, or sea level rise and fall) give way to a phase of relaxation. In this time, "rough" topography is eroded and transported to depositional low regions, giving way to uniform and smooth landscapes. But how long do these processes take to form the landscapes we see today? Do all landforms within the same region experience identical erosional history? Whether they do or do not, what information can we obtain? Here we present a predictive age model of coastal dunes in south east Queensland, Australia utilizing surface roughness (standard deviation of hillslope curvature) as a proxy for age since dune emplacement. These dune fields provide an ideal natural laboratory setting for studying landscape evolution because each dune was initially emplaced near the angle of repose comprise of identical starting sediments, and there is a well established chronology for the features. We selected 14 dunes that were previously dated using optically stimulated luminescence (OSL) spanning the entire Holocene. Each dune was delineated using high-resolution elevation data and the surface roughness was calculated using the zonal statistics tool in ArcGIS. Here we show a strong exponential relationship (r2 = 0.88 and RMSE = 1.2 ka) between surface roughness and age since dune emplacement. Indeed, we observe that each dune systematically smooths and evolves towards planar surfaces (0 m-1) in a predictable way. Together, our results indicate that these coastal dunes are approaching a topographic steady-state within ~12 ka and that deviations in geomorphic expressions are possibly a reflection of larger, regional climate shifts. We infer that our technique utilizing surface roughness as an age proxy is not just limited to dunes but could be broadened to other landform such as terraces, moraines, and hillslopes; future work will expand on this and place it in the context of the geomorphological cycle.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMEP11E2092P
- Keywords:
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- 3020 Littoral processes;
- MARINE GEOLOGY AND GEOPHYSICS;
- 4315 Monitoring;
- forecasting;
- prediction;
- NATURAL HAZARDS;
- 4316 Physical modeling;
- NATURAL HAZARDS;
- 4217 Coastal processes;
- OCEANOGRAPHY: GENERAL