Ground Penetrating Radar (GPR) and Standard Penetration Test (SPT) records of a regressive barrier in southern Brazil

The Pinheira coastal barrier is a prograded complex barrier that shows two main and distinct morphologies: relict swales and foredune ridges, and some suites of discrete parabolic dunes. In the last 7-6 ka this barrier prograded 5 km. Ground Penetrating Radar (GPR) combined with the Standard Penetration Test (SPT) drilling system revealed the regressive stratigraphy of the Pinheira barrier. The most important physical limits (contacts) between the identified facies were determined by both GPR and SPT records, with minor differences on their depth limits. Compaction property was very useful in distinguishing between Foredune ridge/swale and Backshore/foreshore facies, and between Backshore/foreshore and Upper shoreface facies. ¹⁴C dating indicates that deposition of sands and mud of the Middle/lower shoreface facies started at around 4,910 - 4,790 cal years BP at the SPT drilling site, located 1.2 km landwards of the beach. At around 2,460 - 2,270 cal years BP sands of the Upper shoreface facies were deposited, and close to 1,230 - 1,040 cal years BP the coastline was positioned near the drilling site, when Foreshore/backshore facies were being formed.