Salinity variation as an indicator of fluid flow in the lower Ellesmerian Sequence, North Slope, Alaska
Louisiana State University, Shreveport
59 p., Illus., Maps
Previous studies have shown the existence of a topographically driven recharge system in the North Slope foreland basin, Alaska. The Lower Ellesmerian Sequence represents the lowest most flow pathway in the stratigraphic sequence. Limestones and dolomites of the Lisburne Group and sands and shales of the Endicott Group represent laterally extensive pathways for flow. Salinities calculated from spontaneous potential response in the Lower Ellesmerian range from less than 10 gL-1 to over 150 gL-1. Low salinities calculated for the Lower Ellesmerian indicate the displacement of connate marine waters throughout the history of the North Slope foreland basin. Flushing of connate waters likely occurred during the Pennsylvanian through Permian and in the Early Cretaceous when Lower Ellesmerian sediments were subaerially exposed on topographic highs such as the ancestral Barrow Arch. Flow direction during this time was likely in a north to south (present day) orientation due to the reversal of topographic gradient that existed early in the history of the basin. Present day fluid flow in the Lower Ellesmerian likely exists. Active or very recent fluid flow may be the case for structures proximal to the southeast Brooks Range where outcropping Lower Ellesmerian sediments act as recharge points. Salinities in these structures are less than 12 gL-1. Active fluid flow in these structures is indicated by variations in temperature and hydraulic head. Ongoing fluid flow may be occurring in the interior part of the North Slope foreland basin, specifically in the Endicott Group.
Minerals Data and Information Rescue in Alaska (MDIRA)