Heavy Minerals and Size Analysis of the Citronelle Formation of the Gulf Coastal Plain

Abstract

ABSTRACT The heavy minerals of the Citronelle Formation and fluviatile terraces of Louisiana were examined to determine the source of these sediments. Examination of samples indicates that an East Gulf Province heavy mineral suite (kyanite, staurolite, zircon, tourmaline), typical of the Cretaceous and Tertiary sediments of the Gulf Coastal Province is present throughout the Citronelle and older Louisiana terrace deposits. A Mississippi River province suite (epidote, dolomite, amphibole-pyroxene, garnet), presumably derived from the glacial deposits of the northern United States, is present in the younger Louisiana terrace deposits: the Holloway Praire, Port Hickey, and Irene. Based on previous work and heavy mineral and mechanical analysis data determined in this report, the Citronelle Formation appears to represent an alluvial apron formed by coalescing, braiding streams, in response to epeirogenic uplift of the continental interior during Late Pliocene to preglacial Pleistocene time. Encisement of the Mississippi River and other streams into Citronelle sediments has resulted in entrenched valleys containing fluviatile terraces which are mineralogically and lithologically similar to the Citronelle but are at lower elevations. Younger terrace deposits bearing a Mississippi River province heavy mineral suite are believed to have formed in response to fluctuating sea level during the Pleistocene.