--> ABSTRACT: Stratigraphic Controls on Water Table Variation in a Barrier Island Setting, Hatteras Island, North Carolina, by William P. Anderson Jr., David G. Evans, H. E. Mew Jr.; #91020 (1995).

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Stratigraphic Controls on Water Table Variation in a Barrier Island Setting, Hatteras Island, North Carolina

William P. Anderson Jr., David G. Evans, H. E. Mew Jr.

Variation in the water table elevation on barrier islands is determined by the interaction among several variables including groundwater recharge, groundwater density, and island stratigraphy. Models for water table elevation on barrier islands are particularly sensitive to stratigraphy because it affects how hydraulic energy is partitioned between the water table and the freshwater-saltwater transition zone. The surficial aquifer on Hatteras Island, NC, tends to be heterogeneous on the 1m to 10m scale due to 1) generally coarsening-upward barrier-island sand facies; and 2) laterally discontinuous fluvial channel, fluvial-estuarine, and swamp-peat facies. Details at this scale are apparent in ground-penetrating radar surveys and shallow cores. Pumping tests indicate that the aquifer is fairly homogeneous on the >10m scale. The aquifer is anisotropic at this scale due to small-scale heterogeneities.

Coarsening-upward stratigraphy gives rise to a general decrease in hydraulic conductivity with depth, making it difficult to identify the lower boundary of the surficial aquifer. Nonetheless, the hydraulic conductivity of the deep, fine-grained sediments is important to understanding the hydraulic behavior of the aquifer because it strongly influences how the aquifer responds to recharge and discharge events, and how deep, saline water is affected by pumping.

AAPG Search and Discovery Article #91020©1995 AAPG Annual Convention, Houston, Texas, May 5-8, 1995