USGS Professional Paper 1634
Chapter B

New Field Sampling Techniques and Data Description

¹ USGS
² University of New Orleans
³ University of Georgia, Center for Applied Isotope Studies

Introduction

In 1994, the United States Geological Survey (USGS) began a multidisciplinary evaluation of the geology, geomorphology, coastal processes, and environmental quality of the Pontchartrain Basin. The primary issues involved in the study include the environmental quality of the sediments and wetland loss. The sediments in Lake Pontchartrain have a long history of contamination from surface runoff. More recently, the northern and western shorelines of the lake are undergoing erosion, along with subsidence and loss of diversity in vegetation. To adequately assess the impact of these issues, various field investigations were employed (see table 1 below). 

Investigations

Table 1. Field investigations used in the Lake Pontchartrain Basin study.

Summary

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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