Centuries before New Orleans existed, what geographers have dubbed the Pine Island Trend looked very similar to Ship Island in Mississippi, Dauphin Island in Alabama, or even Grand Isle, Louisiana. This now-subterranean feature ran from what is modern-day Metairie through Lakeview and Gentilly and followed part of the I-10 route before veering off to the southern tip of St. Tammany.

Roughly 4500 years ago the Pearl River deposited sand in the Gulf of Mexico during a period of slow sea-level rise. Longshore currents swept the shoal westward, "sculpting it into an island." At about the same time, the Mississippi River jumped its channel near present-day Lafayette, lunged toward the east and began building the St. Bernard delta complex eastward, eventually burying the Pine Island Trend beach sands.

About 2000 years ago, the Mississippi River shifted its course back to the southwest of New Orleans and abandoned the St. Bernard distributary channels.

The complex contains an abundant and diverse marine molluscan fauna. As many as 130 species had been identified as of 1983. The sample indicates a shallowshelf environment. Species included are Mercenaria campechiensis, Dosinia discus, Distortio clathrate, Phalium granulatum, Argopecten gibbus, Noetia ponderosa, Anadara brasiliana and Anadara ovalis.