VOLUMETRIC-ANALYSIS OF A NEW-ENGLAND BARRIER SYSTEM USING GROUND-PENETRATING-RADAR AND CORING TECHNIQUES

Ground-penetrating-radar (GPR) profiles calibrated with core data allo w accurate assessments of coastal barrier volumes. We applied this pro cedure successfully to the barrier system along Saco Bay, Maine (USA), as part of a sediment-budget study that focused on present-day sand v olumes in various coastal, shoreface, and inner-shelf lithosomes, and on sand fluxes that have affected the volume or distribution of sand i n these sediment bodies through time. On GPR profiles, the components of the barrier lithosome are readily differentiated from other facies, except where the radar signal is attenuated by brackish or salty grou ndwater. Significant differences between dielectric properties of the barrier lithosome and other units commonly result in strong boundary r eflectors. The mostly sandy barrier sediments allow deep penetration o f GPR waves, in contrast to finer-grained strata and till-covered bedr ock. Within the Saco Bay barrier system, 22 +/- 3 x 10(6) m(3) of sedi ment are unevenly distributed. Two-thirds of the total barrier volume is contained within the northern and southern ends of the study area, in the Pine Point spit and the Ferry Beach/Goosefare complex, respecti vely. The central area around Old Orchard Beach is locally covered by only a thin veneer of barrier sand, averaging <3 m, that unconformably overlies shallow pre-Holocene facies. The prominence of barrier-spit facies and the distribution pattern of back-barrier sediments indicate that a high degree of segmentation, governed by antecedent topography , has affected the development of the Saco Bay barrier system. The pre sent-day configuration of the barrier and back-barrier region along Sa co Bay, however, conceals much of its early compartmentalized characte r.