OzSET – Australian Surface Elevation Tables and Marker Horizon Data Collection 

The Australian Surface Elevation Table (OzSET) dataset comprises ongoing measurements of surface elevation change and sediment accretion at coastal wetland sites across continental Australia. Surface elevation is recorded using Rod Surface Elevation Tables (RSETs), which measure net vertical displacement of the sediment surface relative to a deep benchmark rod. Sediment accretion is independently quantified using Marker Horizon (MH) feldspar plots, from which sediment cores are extracted to measure new deposition above a known reference layer. Together, these paired measurements allow decomposition of surface elevation change into surface accretion and subsurface processes such as compaction and root growth — critical indicators of coastal wetland resilience to sea level rise. This release presents RSET pin height and MH accretion data from five sites in the Moreton Bay region, Queensland, with collection ongoing and planned extension to additional sites across continental Australia. 

We at TERN acknowledge the Traditional Owners and Custodians throughout Australia, New Zealand and all nations. We honour their profound connections to land, water, biodiversity and culture and pay our respects to their Elders past, present and emerging. This data was collected historically by the authors. This work was partly funded by the Terrestrial Ecosystem Research Network (TERN), an Australian Government NCRIS-enabled project. 

The purpose of RSET is to measure the total surface elevation change relative to a fixed deep benchmark, and the marker horizon measures sediment accretion — the amount of new material deposited on top of the surface since a known reference time. This decomposition is especially important in coastal wetlands where sea level rise resilience depends not just on sediment supply (accretion) but on whether the whole soil column is keeping up through root biomass and other below-ground processes.  

Rod Surface Elevation Table: The RSET measures total surface elevation change relative to a fixed deep benchmark. A stainless steel rod is driven into the ground until it hits resistant substrate (often several metres deep), and a horizontal arm is attached to the top of that rod. From each arm, 9 measuring pins are lowered vertically until they just touch the sediment surface, and their heights above the arm are recorded in millimetres. Because the benchmark rod is anchored deep below any surface processes, changes in the pin readings over time reflect the net vertical movement of the surface; including compaction, swelling, root growth, subsidence, and sediment deposition or erosion. In this dataset, each SET has 4 arms at fixed compass bearings, and 5 direction codes (2, 4, 5, 6, 8); arm numbers are discrete positions on the instrument collar, each locked to a specific bearing (45 °, 315 °, 90 °, 270 °, depending on the plot). Marker Horizon The marker horizon measures sediment accretion only; the amount of new material deposited on top of the surface since a known reference time. A thin layer of white feldspar clay powder is spread on the sediment surface to create a bright, dateable horizon. On each subsequent visit, a small core or plug is extracted, and the thickness of new sediment above the white layer is measured in millimetres.In this dataset there are 12 MH stakes per SET plot (recorded in the separate "marker" sheets), each with its own MH_ID. Not all stakes survive every visit; roots, bioturbation, and erosion can destroy or obscure the feldspar layer, which is why the MH sheets have many null readings