OPEN-FILE REPORT 92


 Quaternary Beach Ridges and Dunes

 Sediments mapped as Quaternary beach ridges and dunes (Qbd) exhibit discernable
beach ridges and dune features. These sediments consist of unconsolidated, light gray to tan, fine
to medium quartz sand with variable percentages of organic material. They are only present in a
small area in the extreme south-central portion of the map area. The Quaternary beach ridges and
dunes (Qbd) sediments are part of the SAS (Southeastern Geological Society Ad Hoc Committee
on Florida Hydrostratigraphic Unit Definition, 1986).

 HYDROGEOLOGY

 The hydrogeology of the map area consists of (in ascending order) the Floridan aquifer
system (FAS), the intermediate aquifer system/intermediate confining unit (IAS/ICU), and the
surficial aquifer system (SAS) (Southeastern Geological Society Ad Hoc Committee on Florida
Hydrostratigraphic Unit Definition, 1986). The FAS, which is the primary source of drinking
water in the region, is generally comprised of carbonate units of the Avon Park Formation, the
Ocala Limestone, the Suwannee Limestone, and the St. Marks Formation. The sands, silts, clays
and carbonates of the Hawthorn Group comprise the IAS/ICU. The SAS is comprised of the
Miccosukee Formation, undifferentiated Quaternary sediments and Quaternary beach ridge and
dune sediments.
 Where siliciclastic sediments of the Hawthorn Group and Miccosukee Formation are
thick, they provide confinement for the FAS, but where the siliciclastic sediments of the
Hawthorn Group and younger units are thin or missing, karst features often occur. "Swallets"
(stream-to-sink features) are of particular concern to geoscientists and hydrogeologists in the
area. Several swallets occur along the edge of the Cody Scarp and in the southern half of the map
area and provide avenues for direct recharge to the FAS by surface water and runoff from
agricultural and urban areas (Figure 1 on OFMS 99-03).

 DERIVATIVE PRODUCTS

 Several derivative products will come from this project. During the mapping project, data
from several hundred wells (Appendix A) were analyzed. Formation picks, made on all available
wells, will allow for the creation of a structure contour map of the top of rock in the study area,
along with an isopach map of overburden for the area. Several Florida Geological Survey staff
members are working on an additional publication, which is beyond the scope of the original
project, which will depict these maps. Additional derivative data that is anticipated to come from
this mapping effort includes an aquifer vulnerability assessment map. Data derived from prior
STATEMAP products has often been used to augment other FGS and Florida Aquifer
Vulnerability Assessment (FAVA) projects in the state (Arthur et al., 2008 (in review); Baker et
al., 2007).

 FIELD HAZARDS

 The authors have been performing fieldwork in Florida for over 50 years between them.
Some of the things that the authors have always been cognizant of are the various hazards which
may pose a safety threat while doing field work in Florida. Among these are heat stroke,