USGS Professional Paper 1634
|The following field investigations were conducted between 1994 and 1997 in Lakes Pontchartrain, Maurepas, Borgne and the surrounding waterways, excluding the Mississippi River. An outline of the survey techniques, their task objective, and accomplishments to date will be followed by detailed descriptions of the methods involved in the techniques.|
|Field Investigation||Technique||Task Objectives|
|Data interpretation for geologic framework; modeling|
(3 surveys, >100 km)
Modeling temporal change
||High resolution sedimentation patterns; post-Pleistocene geologic framework|
|Boreholes (>100)||Regional sedimentation patterns; Pleistocene geologic framework|
|Box cores (>80)||Downcore geochronology; contaminant history; palynological studies|
|Grab samples (>100)||Regional surficial contaminant survey|
surficial sediment sampling
(2 surveys, 800 sites each)
|Regional surficial contaminant survey|
atmospheric flux and
To properly address the issues associated with sediment quality and shoreline dynamics of the Lake Pontchartrain Basin, it is necessary to understand the geologic evolution of the region as well as recent changes in the characteristics of the lake bottom and subsurface. To develop this understanding, a variety of field investigative techniques must be employed. Remote sensing provides a noninvasive, multi-dimensional survey of the lake bottom and subsurface that provides data for geologic framework interpretations, computer models of lake bottom and water column dynamics, and identification of features such as relic barriers, beach trends, fault lines and manmade structures. Subsurface sampling techniques such as vibracore, borehole drilling, and box cores provide a means to directly sample the sediments at depths and resolutions dependent on the type of investigation. Sediments obtained by these techniques yield information on Quaternary geologic framework, regional sedimentation patterns, downcore geochronology, palynology, and sediment contamination history. Finally, surficial sediment sampling such as grab samples and underway sampling are necessary to determine regional sedimentation and contaminant distribution and temporal changes in distribution during the length of the study.
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