GSA Annual Meeting in Phoenix, Arizona, USA - 2019

Paper No. 183-27
Presentation Time: 9:00 AM-6:30 PM


BERGEL, Emily R. and RIEMERSMA, Peter E., Department of Geology, Grand Valley State University, 1 Campus Drive, Allendale, MI 49401

Florida beach sand plays a major role in Florida’s economy as over 18 million tourists come to visit the state’s coastlines each year. Our objective is to use beach sand as an opportunity to educate beach visitors about why the sands are different and the geologic story that the sand has to tell. We hope to provide insight into how the processes of erosion, transport and deposition and factors such as local outcrops, waves, currents and human impact affect beach sand composition and grain size. An example of how humans directly impact the coastline environment are the 30 active beach nourishment sites and over 90 permitted locations. A case study example of beach nourishment illustrates the importance of sand composition and grain size in successful project design and implementation. Changes in the character of introduced sand can also impact loggerhead turtles who need the beaches for nesting.

Twelve beach sand samples that were personally collected or donated were analyzed from Florida beaches along the east and west coastlines that included samples from the House of Refuge, Gulfstream, Fort Meyers, Tampa Bay, and Panama City. Samples were analyzed for grain size using a series of sieves and for composition by performing carbonate dissolution. The majority of samples are fine grained and moderately well sorted. Some samples were very well sorted (Panama City) and poorly sorted (Tampa Bay) with two more carbonate rich samples having mean grain sizes of medium to coarse. A common observation is that Florida beach sand is a mixture of quartz and carbonate shell fragments. We found the percentage of quartz in beach sand samples to range from 100 % to 28 %. The existence of quartz is significant because Florida is a carbonate platform and there are few local sources of quartz. The origin of quartz is from the erosion of the southern Appalachian Mountains and represents a fundamental change in transport and depositional conditions that occurred about 30 million years ago.

We’ll use a combination of photomicrographs and grain size distribution curves of the different beach sands to highlight visually and quantitatively differences observed between the beach sands. We want to help the public see sand through the eyes of a geologist.