GSA Connects 2021 in Portland, Oregon

Paper No. 22-2
Presentation Time: 9:00 AM-1:00 PM


DOYLE, Kevin, 11632 Stonecreek Cir, Fort Myers, FL 33913-9083

Dickman’s Point Beach is the northern-most barrier island in a four mile-long trend of barrier/mangrove islands that extends southeast to Cape Romano in the Ten Thousand Islands chain, Collier County, Southwest Florida. Because it is located within the Rookery Bay National Estuarine Research Reserve, Dickman’s Point Beach has been protected from development, facilitating the study of its natural sedimentary processes and geomorphological development.

Field work was conducted in February 2020 and data collection included surface grab sample, sediment cores (0-2 feet in depth) and Ground Penetrating Radar (GPR) transects. These data were complimented with Lidar, historical aerial photographs and satellite imagery.

Analysis of these datasets (Ibarra et al, 2020) showed how natural and human influences have impacted the geomorphology of Dickman’s Point Beach with natural processes at work between 1926 and 1962 and a combination of natural and man-made influences after 1962.

Sedimentary facies were interpreted on the GPR profiles by 1) identifying packages of GRP reflection geometries and 2) matching them to sedimentary geometries and associated depositional environments. Where possible, sedimentary structures in the sediment cores were integrated into the reflection geometries.

The interpretation of GPR-based sedimentary facies on Dickman’s Point Beach suggests dynamic geomorphology over time, including: 1) Inclined/shingled geometries = lateral accretion = progradation to the northwest, 2) Scour/fill geometries = high energy storm related channeling = erosion of southern margin, 3) Parallel geometries = wind/wave planar sediment movement = west-facing beaches, 4) Onlap/truncation geometries = deposition adjacent to an exposed surface = southwestern beaches.

Follow-up studies will include the collection of vibracores to allow more extensive core-based sedimentary facies to be correlated to GRP-based geometries.