Altama heavy mineral deposits in southeastern Georgia

E. I. Du Pont de Nemours and Co., Starke, FL, United States

The Altama heavy mineral deposits are present just north of Brunswick, Georgia, in northsouth-trending dune ridges of quartz sand that accumulated along a Pamlico shoreline in Pleistocene time. Most of the heavy minerals occur in very thin stringers disseminated throughout the dune sands, not as thick ribbons of black concentrates so characteristic of some storm line deposits. Principal component analysis reveals that ilmenite has an inverse relationship to lighter epidote, hornblende, and garnet. In addition, the analysis shows a strong positive relationship between the total heavy mineral content and the 3.5- to 4-o sand fraction. These relationships are considered to reflect sorting, reworking, and winnowing.The principal component analysis of the Altama sediments was compared to principal component analyses of essentially similar size sediments of dune ridges along present-day barrier islands of the northeastern Florida coast. As in the case of the Altama ridges, ilmenite in the more modern ridges has an inverse relationship to the lighter heavy minerals and the total heavy mineral content shows a strong positive relationship to the very fine sands. These similarities in statistical patterns lend strength to the interpretation of the Altama heavy mineral deposits as dune ridges developed along an ancient shoreline.

This record provided courtesy of AGI/GeoRef.