DELTAIC HEADLAND EVOLUTION: TRANSITORY PHASES IN THE CONSTRUCTIONAL TO DESTRUCTIONAL DEPOSITIONAL SPECTRUM

Studies of the Mississippi River delta system have historically provided invaluable insight to the depositional character, stratigraphic framework, and evolution of modern as well as ancient deltaic systems. A fundamental process-response concept stemming from these studies has been the delta cycle model, consisting of constructional and destructional phases of sedimentation. During the constructional phase a deltaic depocenter progrades, expanding the deltaic plain distributary networks seaward. Conversely, during the destructional phase a deltaic headland is subjected to transgression and marine reworking as relative sea level rises across the headland due to the varying effects of curtailed sediment supply, fluvial avulsion, eustatic rise, and substrate subsidence. Consequently, the delta cycle paradigm explains the stacked and laterally offset framework of deltaic depocenters commonly comprising deltaic systems. Although much research has been conducted on the constructional and destructional phases and their associated stratigraphic architectures, few details exist concerning the style of deposition intermediate between these end member processes and resulting stratigraphy. Recent sand-resource studies along the Barataria barrier island complex of south-central Louisiana have resulted in a large stratigraphic database consisting of high-resolution seismic profiles, vibracores, and quantitative textural data, that can be used to examine the evolutionary continuum of deltaic headlands. The Barataria shoreline is located at the southern boundary of the interdistributary Barataria basin between the active Plaquemines delta lobe and the Lafourche delta headland. Each of these depocenters initially provided a sediment source for the formation of the Barataria barrier island complex. More recently, expansion of northern Barataria Basin due to extensive wetland loss has resulted in a larger tidal exchange and thus development and growth of tidal-inlets and fragmentation of the barrier shoreline. Concomitantly, depositional packages such as ebb tidal deltas have enlarged and become increasingly dominate within the nearshore stratigraphy. This sedimentary package represents a distinct, under examined depositional phase within the constructional to destructional spectrum.