Sediment infilling and geomorphological change of a mud-capped Raccoon Island dredge pit near Ship Shoal of Louisiana shelf

2020 ◽  
Vol 245 ◽  
pp. 106979 ◽  
Author(s):  
Haoran Liu ◽  
Kehui Xu ◽  
Carol Wilson
Keyword(s):  
Louisiana Shelf

Hydrodynamics, sediment transport, and water quality of two contrasting dredge pits on the Louisiana shelf

2021 ◽  
Vol 230 ◽  
pp. 104569
Author(s):  
Robert Bales ◽  
Kehui Xu ◽  
Guandong Li ◽  
Kanchan Maiti ◽  
Haoran Liu
Keyword(s):  
Water Quality ◽  
Sediment Transport ◽  
Louisiana Shelf

scholarly journals Parameterization of biogeochemical sediment–water fluxes using in situ measurements and a diagenetic model

2016 ◽  
Vol 13 (1) ◽  
pp. 77-94 ◽  
Author(s):  
A. Laurent ◽  
K. Fennel ◽  
R. Wilson ◽  
J. Lehrter ◽  
R. Devereux
Keyword(s):  
Water Column ◽  
Bottom Water ◽  
In Situ Measurements ◽  
Nutrient Loads ◽  
Water Fluxes ◽  
Overlying Water ◽  
Louisiana Shelf ◽  
Biogeochemical Models ◽  
Bottom Waters

Abstract. Diagenetic processes are important drivers of water column biogeochemistry in coastal areas. For example, sediment oxygen consumption can be a significant contributor to oxygen depletion in hypoxic systems, and sediment–water nutrient fluxes support primary productivity in the overlying water column. Moreover, nonlinearities develop between bottom water conditions and sediment–water fluxes due to loss of oxygen-dependent processes in the sediment as oxygen becomes depleted in bottom waters. Yet, sediment–water fluxes of chemical species are often parameterized crudely in coupled physical–biogeochemical models, using simple linear parameterizations that are only poorly constrained by observations. Diagenetic models that represent sediment biogeochemistry are available, but rarely are coupled to water column biogeochemical models because they are computationally expensive. Here, we apply a method that efficiently parameterizes sediment–water fluxes of oxygen, nitrate and ammonium by combining in situ measurements, a diagenetic model and a parameter optimization method. As a proof of concept, we apply this method to the Louisiana Shelf where high primary production, stimulated by excessive nutrient loads from the Mississippi–Atchafalaya River system, promotes the development of hypoxic bottom waters in summer. The parameterized sediment–water fluxes represent nonlinear feedbacks between water column and sediment processes at low bottom water oxygen concentrations, which may persist for long periods (weeks to months) in hypoxic systems such as the Louisiana Shelf. This method can be applied to other systems and is particularly relevant for shallow coastal and estuarine waters where the interaction between sediment and water column is strong and hypoxia is prone to occur due to land-based nutrient loads.

The effect of pressure on rock properties in the Gulf of Mexico: Comparison between compaction disequilibrium and unloading

2014 ◽  
Vol 2 (1) ◽  
pp. SB1-SB15 ◽  
Author(s):  
Hua Yu ◽  
Fred J. Hilterman
Keyword(s):  
Gulf Of Mexico ◽  
Rock Properties ◽  
Louisiana Shelf ◽  
Major Mechanism ◽  
Detailed Evaluation ◽  
Density Values ◽  
Pressure Regime ◽  
Relationship Of ◽  
The Relationship ◽  
Velocity Decrease

We used statistical methods on rock properties derived from more than 480 wells to catalog shale velocity and density trends in different pressure regimes in the Gulf of Mexico and evaluated the reasons for their variations. A detailed evaluation of the density and velocity trends revealed that in the northern part of the Louisiana shelf, unloading is the major mechanism of overpressure. The onset of overpressure occurs at depths around 3000 m where temperatures are normally greater than 70°C. The relationship of the temperature gradient increase and the velocity decrease to the smectite-illite transformation allowed us to believe that inelastic unloading may be the major mechanism for overpressure in this region. On the other hand, in the southern part of the Louisiana shelf, abnormal pore pressure is often caused by compaction disequilibrium where the sediment section has a low sand percentage. In this type of pressure regime, velocity and density values cease to change at the onset of overpressure and essentially remain at the same value below the onset.

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