Unearthing sea level records from Down Under: GPR, OSL, and LiDAR (GOaL) resolve small fluctuations in sea-level and coastal change over large spatial- and temporal-scales

Abstract:

Refined records of Holocene and Pleistocene sea-level as well as coastal evolution are needed to forecast changes in the Anthropocene. The sensitivity of sandy barriers to sea level that makes them vulnerable to future rise also means that they have the potential to record past changes. While eroding barrier islands preserve records of past sea level within the estuarine muds behind or beneath them, those that prograded during interglacial periods preserve a history of sea level and coastal evolution within their stratigraphy. High-resolution geophysics unearthed sea-level records from the US coast 20 years ago, yielding curves similar to those extracted from estuarine sediments. Recent reconstructions from prograded barriers show agreement with glacial isostatic adjustment (GIA) models in near- and intermediate- field sites. Despite the potential of extracting sea level records from prograded barriers utilizing Ground-Penetrating Radar (GPR), Light Detecting and Ranging (LiDAR), and Optically Stimulated Luminescence (OSL); this is still a relatively underutilized method that is in its infancy compared to established techniques such as erosional notches or intertidal deposits. Here we present an optimal methodology using GPR, OSL, and LiDAR (GOaL) that adheres to rigorous existing protocol for mapping sea level indicator points in order to untap this exceptional archive of past sea level. Data from over a dozen far-field sites along the tectonically quiet northern coast of New Zealand and the east coast of Australia; extending to intermediate-field sites in Tasmania. Ultimately, the aim is that this research will culminate in a comprehensive sea-level database for Down Under that is similar to those from the UK (Shennan and Horton, 2002) and East Coast of the US (Engelhart and Horton, 2012). Given the abundance of 300+ prograded systems around the world and their existence in near- to far-field locations of varying climatic as well as geologic setting; unearthing this archive has the potential to add to the global atlas of sea level (Khan et al. 2019) by filling in gaps where there is limited or debated records.