Eastern Mississippi delta: late Wisconsin unconformity, overlying transgressive facies, sea level and subsidence

Stanley, Daniel Jean; Warne, Andrew G.; Dunbar, Joseph B.

doi:10.1016/s0013-7952(96)00022-1

Cited by 19 publications

(20 citation statements)

References 14 publications

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“…It is based on the data reported by Kolb [] on the elevation of the Pleistocene clay (squares) and Holocene clay (circles), by Stanley et al . [] for the Pleistocene clay (squares) and by Nittrouer et al . [, ] for the Mississippi River thalweg (grey dots) and for the elevation of the bedrock substrate (triangles).…”

Section: Model Validation On the Lowermost 500 Km Of The Mississippi mentioning

confidence: 99%

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Modeling flow and sediment transport dynamics in the lowermost Mississippi River, Louisiana, USA, with an upstream alluvial‐bedrock transition and a downstream bedrock‐alluvial transition: Implications for land building using engineered diversions

2015

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The lowermost Mississippi River, defined herein as the river segment downstream of the Old River Control Structure and hydrodynamically influenced by the Gulf of Mexico, extends for approximately 500 km. This segment includes a bedrock (or more precisely, mixed bedrock-alluvial) reach that is bounded by an upstream alluvial-bedrock transition and a downstream bedrock-alluvial transition. Here we present a one-dimensional mathematical formulation for the long-term evolution of lowland rivers that is able to reproduce the morphodynamics of both the alluvial-bedrock and the bedrock-alluvial transitions. Model results show that the magnitude of the alluvial equilibrium bed slope relative to the bedrock surface slope and the depth of bedrock surface relative to the water surface base level strongly influence the mobile bed equilibrium of low-sloping river channels. Using data from the lowermost Mississippi River, the model is zeroed and validated at field scale by comparing the numerical results with field measurements. The model is then applied to predict the influence on the stability of channel bed elevation in response to delta restoration projects. In particular, the response of the river bed to the implementation of two examples of land-building diversions to extract water and sediment from the main channel is studied. In this regard, our model results show that engineered land-building diversions along the lowermost Mississippi River are capable of producing equilibrated bed profiles with only modest shoaling or erosion, and therefore, such diversions are a sustainable strategy for mitigating land loss within the Mississippi River Delta.

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Section: Model Validation On the Lowermost 500 Km Of The Mississippi mentioning

confidence: 99%

“…[], data for the top of the Pleistocene clay are from Kolb [] and Stanley et al . [], and data for the top of the Holocene clay are from Kolb [].…”

Section: Model Validation On the Lowermost 500 Km Of The Mississippi mentioning

confidence: 99%

Modeling flow and sediment transport dynamics in the lowermost Mississippi River, Louisiana, USA, with an upstream alluvial‐bedrock transition and a downstream bedrock‐alluvial transition: Implications for land building using engineered diversions

2015

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“…The Mississippi River in the present survey reach is incised into consolidated, seaward‐dipping fluvio‐deltaic strata (Galler et al. , 2003); based on collection of cores from within 1 km of the modern Mississippi River channel, the age range of these sediments is from Late Pleistocene to Holocene (Stanley et al. , 1996).…”

Section: Settingmentioning

confidence: 99%

The lowermost Mississippi River: a mixed bedrock‐alluvial channel

Nittrouer¹,

Mohrig²,

Allison³

et al. 2011

Sedimentology

110

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In this study, the distribution of channel‐bed sediment facies in the lowermost Mississippi River is analysed using multibeam data, complemented by sidescan sonar and compressed high‐intensity radar pulse seismic data, as well as grab and core samples of bed material. The channel bed is composed of a discontinuous layer of alluvial sediment and a relict substratum that is exposed on the channel bed and sidewalls. The consolidated substratum is made up of latest Pleistocene and Early Holocene fluvio‐deltaic deposits and is preferentially exposed in the deepest thalweg segments and on channel sidewalls in river bends. The exposed substratum commonly displays a suite of erosional features, including flutes that are quantitatively similar in form to those produced under known laboratory conditions. A total of five bed facies are mapped, three of which include modern alluvial deposits and two facies that are associated with the relict substratum. A radius of curvature analysis applied to the Mississippi River centreline demonstrates that the reach‐scale distribution of channel‐bed facies is related to river planform. From a broader perspective, the distribution of channel‐bed facies is related to channel sinuosity — higher sinuosity promotes greater substratum exposure at the expense of alluvial sediment. For example, the ratio of alluvial cover to substratum is ca 1·5:1 for a 45 km segment of the river that has a sinuosity of 1·76 and this ratio increases to ca 3:1 for a 120 km segment of the river that has a sinuosity of 1·21. The exposed substratum is interpreted as bedrock and, given the relative coverage of alluvial sediment in the channel, the lowermost Mississippi River can be classified as a mixed bedrock‐alluvial channel. The analyses demonstrate that a mixed bedrock‐alluvial channel boundary can be associated with low‐gradient and sand‐bed rivers near their marine outlet.

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“…Limited accretion and erosion continues along banklines inside the artificial levees, and ephemeral muds are commonly deposited from suspension in shallow (<20 m water depth) bank areas during periods of low water discharge [ Galler , 2004]. Below Baton Rouge, Louisiana (RK 370), the Mississippi River channel incises into seaward dipping, highly consolidated fluvio‐deltaic strata that range from Pleistocene age upstream to <1000 years old near the Gulf of Mexico [ Stanley et al , 1996]. Below RK 164, channel bed sediment is primarily fine to medium sand.…”

Section: Settingmentioning

confidence: 99%

Bedform transport rates for the lowermost Mississippi River

2008

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[1] New methods of data collection and processing are developed to provide quantitative, reach-scale measurements of bedform transport mass within the tidally influenced Mississippi River. A multibeam swath profiler was used to collect daily bathymetry over a range of water discharges, and bed elevation changes induced by dune migration are measured. These values are coupled with bulk physical properties of the bed sediment to constrain mass flux, and annual bedform transport is estimated at 2.2 Â 10 6 metric tons (MT). The total annual sand flux from the Mississippi River, calculated by combining measured bedform transport rates and suspended sediment flux, is estimated to be 20 Â 10 6 MT. Survey data also provide information about the spatial distribution of dunes across the channel bottom. Straight reach segments are commonly mantled by dunes for the entire cross section, while bends are typically areas of focused scour devoid of bedforms. Presumably, any sediments associated with migrating dunes are propelled into suspension within bends before redepositing in the subsequent straight reach. Movement via suspension is therefore an important component for the downriver transport of bed materials in the lower Mississippi River.

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Eastern Mississippi delta: late Wisconsin unconformity, overlying transgressive facies, sea level and subsidence

Cited by 19 publications

References 14 publications

Modeling flow and sediment transport dynamics in the lowermost Mississippi River, Louisiana, USA, with an upstream alluvial‐bedrock transition and a downstream bedrock‐alluvial transition: Implications for land building using engineered diversions

Modeling flow and sediment transport dynamics in the lowermost Mississippi River, Louisiana, USA, with an upstream alluvial‐bedrock transition and a downstream bedrock‐alluvial transition: Implications for land building using engineered diversions

The lowermost Mississippi River: a mixed bedrock‐alluvial channel

Bedform transport rates for the lowermost Mississippi River

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