Georgia Journal of Science

Article Title

A Petrographic Analysis of Silica and other Cements in the Altamaha Formation, Central Georgia.**


Opaline and silica cements have been reported in Miocene sandstones of the central Georgia, Altamaha Formation. This study is an attempt to characterize these cements using both hand sample examination and petrographic analysis. Samples were collected from several locations in Georgia (from Ashburn, Georgia, to Soperton, Georgia in the Central Georgia Coastal Plain). The Altamaha formation is a well-indurated, poorly sorted, angular, arkosic to subarkosic, sandstone with abundant matrix and wide-spread silica cement. The sandstone is interpreted to be terrestrial based on the presence of terrestrial fossils as well as other depositional features. The cements are present in significant volumes and the origin of this abundance is uncertain. Preliminary analysis of thin sections indicates that much of the cement is opal, but other areas appear to be chalcedonic cement. In hand sample, the opaline cements are opaque white with conchoidal fracture, they do not show opaline luster. Additionally, very minor areas of clay cement and carbonate cement have also been observed. The goal here is to better understand the origin of the cements and the associated depositional environment. This work is currently in progress but should be completed soon.

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