GPR-BASED MODEL OF A DUNE PALEOSOL: AN EXAMPLE FROM HOLLAND, MICHIGAN, USA

Extensive coastal dune fields occur along the southeastern shoreline of Lake Michigan and numerous paleosols have been observed within the aeolian deposits. Paleosols have been used to infer shoreline paleoenvironmental conditions and have generated hypotheses about past shoreline morphology, however most paleosols are observed as exposures in dune faces, or through trenching, and knowledge of paleosol distribution and topography remains elusive. Ground penetrating radar (GPR) was used to study the internal structure of a bluff top aeolian environment at Tunnel Park (TP), Holland, Michigan to determine the internal structure of a bluff top dune. GPR data shows a semi-continuous strong reflector ranging from 1.8 to 7.6 m below the surface on three intersecting transects. Using the depth data from three GPR transects, a GIS-derived 3D model of the reflector was generated. A hand auger was used to collect sediment from the reflector and analyzed for moisture content, organic content, grain size, and chronology. One radiocarbon date on bulk sediment from the buried soil dates to 960 - 1012 years BP (2σ calibrated age) and this age is consistent with other well-dated paleosols in shoreline dunes. The modeled reflector surface reveals a parabolic dune blowout-type topography unlike the modern surface at Tunnel Park, which is a relatively flat, continuous dune ridge. The 3D model of the dune paleosol surface gives a ‘snapshot’ of the dune topography at the time of the paleosol, and combined with the nascent TP paleosol age data, indicates that some time during the last 1,000 years the dune blowout-type environment was completely buried. Thus, the GPR-based 3D model of the TP paleosol is an improvement over the 2D GPR transects for studying aeolian landscape change along the Lake Michigan shoreline.