The Mississippi River source-to-sink system: Perspectives on tectonic, climatic, and anthropogenic influences, Miocene to Anthropocene

Abstract

The Mississippi River fluvial-marine sediment-dispersal system (MRS) has become the focus of renewed research during the past decade, driven by the recognition that the channel, alluvial valley, delta, and offshore regions are critical components of North American economic and ecological networks. This renaissance follows and builds on over a century of intense engineering and geological study, and was sparked by the catastrophic Gulf of Mexico 2005 hurricane season, the 2010 Deep Water Horizon oil spill, and the newly recognized utility of source-to-sink concepts in hydrocarbon exploration and production. With this paper, we consider influences on the MRS over Neogene timescales, integrate fluvial and marine processes with the valley to shelf to deepwater regions, discuss MRS evolution through the late Pleistocene and Holocene, and conclude with an evaluation of Anthropocene MRS morphodynamics and source-to-sink connectivity in a time of profound human alteration of the system. In doing so, we evaluate the effects of tectonic, climatic, and anthropogenic influences on the MRS over multiple timescales. The Holocene MRS exhibits autogenic process-response at multiple spatial and temporal scales, from terrestrial catchment to marine basin. There is also ample evidence for allogenic influence, if not outright control, on these same morphodynamic phenomena that are often considered hallmarks of autogenesis in sedimentary systems. Prime examples include episodes of enhanced Holocene flooding that likely triggered avulsion, crevassing, and lobe-switching events at subdelta to delta scales. The modern locus of the Mississippi fluvial axis and shelf-slope-fan complex was established by Neogene crustal dynamics that steered sediment supply. Dominant Miocene sediment supply shifted west to east, due to regional subsidence in the Rockies. Then, drier 3 conditions inhibited sediment delivery from the Rocky Mountains, and Appalachian epeirogenic uplift combined with wetter conditions to enhance sediment delivery from the Appalachians. Climatic influences came to the forefront during Pleistocene glacial-interglacial cycles. The fluvial system rapidly responded to sea-level rises and falls with rapid and extensive floodplain aggradation and fluvial knickpoint migration, respectively. More dramatically, meltwater flood episodes spanning decades to centuries were powerful agents of geomorphic sculpting and source-to-sink connectivity from the ice edge to the deepest marine basin. Differential sediment loading from alluvial valley to slope extending from Cretaceous to present time drove salttectonic motions, which provided additional morphodynamic complexity, steered deep-sea sediment delivery, diverted and closed canyons, and contributed to modern slope geometry. Despite the best efforts from generations of engineers, the leveed, gated, and dammed Mississippi still demonstrates the same tendency for self-regulation that confronted 19 th century engineers. This is most apparent in the bed-level aggradation and scour associated wit...

Using climate to relate water discharge and area in modern and ancient catchments

“…The extent and quality of geomorphological and subsurface data sets has increased greatly in recent decades, and has made it possible to attempt to reconstruct ancient sedimentary systems from source to sink (e.g. Sømme et al ., ; Galloway et al ., ; Allen et al ., ; Michael et al ., ; Hampson et al ., ; Holbrook & Wanas, ; Bentley et al ., ). The goals of such studies are to understand the coupling between sediment producing catchments (or source areas), sediment‐storing sedimentary basins (or sinks) , the sediment routing systems connecting these systems, and how these interact to record Earth history (e.g.…”

The distribution of rivers to terrestrial sinks: Implications for sediment routing systems

“…In fact, Castelltort and Van Den Driessche (2003) calculated a transport zone (including its terrestrial sink) N300 km can diffuse even millenial scale pertubations before sedimentation occurs at the marine realm. Furthermore, sea level fluctuations will introduce variability by not only remobilizing floodplain deposits but causing upstream catchment denudation as the fluvial system responds to base level change (Schumm, 1993;Bentley et al, 2016) and fluvial systems potentially extend basinward, reaching the shelf edge and causing sediment bypass to the basin floor (see Shanmugam, 2016). The Indus (Clift and Giosan, 2014), Ganges/Bahramputra (Goodbred and Kuehl, 1999) and Missisippi River basins (Bentley et al, 2016) are examples where changes to deep water deposition have been attributed to sea-level flucations as opposed to changes affecting sediment discharge from source catchment change (Shanmugam et al, 2015;Romans et al, 2016).…”

Implications of Texture and Erodibility for Sediment Retention in Receiving Basins of Coastal Louisiana Diversions

“…Its subdelta started to develop around 1839 due to a flood break in the river levee and led to rapid development of land until 1932. After 1932, subsidence, sea-level rise, storms and reduced sediment deposition all contributed to land deterioration and formed the current open water body [12,15,27]. In order to restore vegetated wetlands and create land, since 2003 water and sediment have been diverted from a non-gated crevasse at a 120˝angle along the west bank of the Mississippi River 7.6 km upstream of the Head of Passes of MRD (Figure 2A).…”

“…Its subdelta started to develop around 1839 due to a flood break in the river levee and led to rapid development of land until 1932. After 1932, subsidence, sea-level rise, storms and reduced sediment deposition all contributed to land deterioration and formed the current open water body [12,15,27]. West Bay was selected as one of our study areas because it is the only operational artificial diversion to date designed specifically for land building in coastal Louisiana [10].…”

“…The lack of field erodibility data poses a challenge to the ongoing modeling work of Louisiana CPRA to predict land growth and sediment retention in receiving basins for future large diversions. Although the Mississippi River deltaic plain has been the subject of abundant research over recent decades [12], few studies have quantified erodibility and high-resolution grain size distribution, both of which control the sediment retention rate in receiving basins.…”