New Techniques for Stratigraphic Analysis and Correlation--Fourier Grain Shape Analysis Louisiana Offshore Pliocene

Abstract

ABSTRACT Because quartz grain shape is sensitive to provenance and environmental processes, stratigraphic shape analysis may be a complementary technique to conventional correlation methods. To test the validity and practicality of such a technique, sidewall cores from an 11,000 foot unconsolidated Pliocene interval in West Delta Block 117 offshore Louisiana were sampled and analyzed by Fourier shape analysis. Approximately one hundred grains from each of nineteen samples were sufficient to subdivide the interval into distinct shape zones. Shape frequency distributions of all samples were polymodal. In most cases, sample differences are caused by the presence or absence of 20% or fewer characteristically shaped grains. Correlation based on quartz grain shape was successfully tested by sampling in detail two stratigraphically separated sands in one well and a correlating one of these with a sand in a second well over a mile away. Fourier shape analysis is amenable to a high degree of automation and could become an additional tool for subsurface stratigraphic correlation and analysis.