Lake Weir, in southcentral Marion county, is situated along the edge of the Ocala Uplift in the Central Lakes District. This area is comprised of sand hills with water table lakes filling their interstices (Brooks and Merritt, 1981). These sand hills comprise part of the thick, undifferentiated sediments that overlie the Hawthorn Group, which occurs at about sea level in this area (Scott, 1988). The lake wraps around the southern extent of one of these hills to form Little Lake Weir to the west. Lake elevation at the time of the seismic survey was ~16.7 m (55 ft) NGVD. Lake Weir is roughly circular in shape with a perimeter of approximately 35 km and an area of 31km². To the north, the lake is connected via drainage canal to Marshall Swamp which occupies the large Oklawaha valley and river system.