Link to USGS home page
Coastal and Marine Geology Program
Coastal & Marine Geology Program > St. Petersburg Coastal and Marine Science Center > Lake Pontchartrain Basin

Geologic Framework and Processes of the Lake Pontchartrain Basin

Lake Pontchartrain Basin Home
Field Methods
Topics of Investigation
Geologic Framework
Wetland Change
Water Circulation
Satellite Imagery
Bonnet-Carré Spillway Event
Water Turbidity
Sea-Surface Temperature
1997 Algal Bloom
Project Contact:
Jim Flocks

Geologic Framework

The geologic framework is an assessment of how the sediments were deposited in the area during the geologic past. The sedimentary layers below the lake bottom were imaged using a radar-like device called high-resolution seismic profiling. Sidescan-sonar images of the lake floor also were collected. These images are similar to aerial photographs of the land. Sediment samples were collected to analyze their composition and determine how they were deposited.

An evolutionary model (A-E, at right) for the Lake Pontchartrain area was developed using seismic and sedimentological data.Following the late Wisconsin sea-level lowstand (~18,000 years ago), sea level rose and flooded the area (A-B). By 6,000 years ago, sea-level rise slowed, and longshore transport developed a barrier-beach system (B). As sea level continued to rise, the barrier system was bypassed, forming the Pine Island Barrier trend, while flooding created the Pontchartrain Basin embayment (C). By 4,500 years ago, the Mississippi River moved into the area and began depositing the St.Bernard Delta lobe enclosing the embayment (D). Modern stabilization and subsidence of the delta lobe began by 2,000 years ago,developing Lakes Maurepas, Pontchartrain, and Borgne, and creating the land surface seen today.

  18,000 years ago
model, part A
6,000 years ago
model, part B
5,000 years ago
model, part C
4,500 - 2,000 years ago
Evolutionary model, part D
Present day
model, part E

Additional Geologic Characterization Figures:
seismic profile
seismic profile
seismic profile
seismic profile
3-D subsurface model
dredge pit
dredge pit
south shore
south shore
Pleistocene channel seismic profile
Pleistocene channel seismic profile

  top of page

Coastal & Marine Geology Program > St. Petersburg Coastal and Marine Science Center > Lake Pontchartrain Basin U. S. Department of the Interior | U.S. Geological Survey
Center for Coastal & Regional Marine Studies

email Feedback | USGS privacy statement | Disclaimer | Accessibility

This page is
Updated December 05, 2016 @ 11:25 AM (THF)