COASTAL LAND LOSS AND LANDSCAPE LEVEL PLANT COMMUNITY SUCCESSION; AN EXPECTED RESULT OF NATURAL TECTONIC SUBSIDENCE AND FAULT MOVEMENT

The signature of tectonic subsidence is present at Goose Point. This paper discusses possible fault-driven subsidence along the Baton Rouge Fault System as the primary driving mechanism for both vegetation change and marsh loss at Goose Point.

Goose Point, Louisiana, is on the north shore of Lake Pontchartrain about 32 kilometers (20 miles) north of New Orleans, Louisiana. In the 1950's Goose Point was a stopover for geese migrating through the north shore of Lake Pontchartrain. The vast acres of Three Cornered Grass (Shoenoplexus americanus) (Glockner 2008) that attracted those flocks has now been replaced by Salt Meadow Cord Grass (Spartina patens). The shift in the marsh plant community is likely driven by more water on the marsh, not more salt in the water. The aerial signature of Goose Point is indistinguishable from other degraded, subsiding coastal marshes across southeast Louisiana.

What makes Goose Point interesting from a coastal land loss/subsidence standpoint is what is not present. Typical major factors put forward to explain Louisiana's coastal land loss include erosion, herbivory (nutria), Holocene sediment compaction, levees, water/oil extraction, and E&P canals. Absent these factors' presence, or at magnitudes capable of impacting the regional landscape, the responsible cause(s) for marsh loss and inland plant community migration must be something else; perhaps something bigger and deeper. Tectonic deformation associated with crustal deformation due to Mississippi River delta deposits, transforms, and - perhaps more directly at this locality - faulting associated with onshore segments of the Baton Rouge Fault better explain these changes.

The Baton Rouge Fault System trends northwest - southeast along the north shore of the lake with active fault segments through the lake (Lopez 1996). Prominent lineaments have been mapped as onshore components of the Baton Rouge Fault System (Saucier 1994, Gagliano et al. 2003).

The general lack of geological input in land loss studies and coastal restoration projects throughout coastal Louisiana is glaring. Until regional tectonics and local faulting is integrated into land loss models, coastal restoration efforts will continue to under-perform or fail.