MAPPING THE GEOLOGIC FRAMEWORK OF PADRE ISLAND NATIONAL SEASHORE USING GEOPHYSICAL SURVEYS

Framework geology has been demonstrated to influence barrier island geomorphology and resiliency. It is vital that we understand the framework geology before we can accurately assess the vulnerability and resiliency of the coast. Ground-penetrating radar (GPR) and electromagnetic inductance (EMI) surveys were collected along Padre Island National Seashore (PAIS) to map variations in the subsurface geologic framework. The most extensive published survey of PAIS framework geology was conducted in the 1950s as part of dredging the Intracoastal Waterway through Laguna Madre. Using cores and seismic surveys, the previous study identified a series of relict infilled paleochannels in dissecting PAIS. The GPR and EMI surveys presented in this poster were collected in fall 2014 and 2016. Utilizing both surveys will be useful in more precisely locating paleochannels in the subsurface of PAIS for further geologic study (e.g. sediment cores). Validating subsurface framework geology features (i.e. infilled paleochannels) is valuable to accurately predicting future changes affecting the environmental and economic longevity of PAIS. Therefore, future research needs of this project include sediment core collection and analysis from areas on the island surveyed here in an effort to assess how other island factors (e.g. vegetation dynamics and hydrology) operate in conjunction with the geologic framework to influence coastal geomorphology. Sediment cores collected in spring 2017 will be used to both validate the geophysical survey data and provide valuable insight into the geochronological evolution history of PAIS and similar barrier islands.