V-SHAPED PITS AS INDICATORS OF SPECIFIC DEPOSITIONAL ENVIRONMENTS

Before the introduction of SEM, the use of a standard microscope provided a basic view of grains showing textures such as frosting and polishing and interpretations of paleoenvironments were interpreted from these data. Mathematical methods, such as Fourier analyses, have also been used in an attempt to determine the environment of deposition. At best this method can only see large-scale features, roughly 7.5 degrees from the center of the grain or larger, which are not particularly useful in determining all paleoenvironments.

The use of the Scanning Electron Microscope (SEM) has greatly advanced studies in sedimentary geology, giving clear views of sediments at extremely high magnifications to see microtextures on the grain surfaces. Surficial Grain Analysis (SGA) is one of many techniques used to describe grain texture, the goal of which is to categorize these different microtextures and determine the environment in which these features were formed (Boggs, 2003).

With the SEM, surficial grain analyses are generally performed on quartz grains because of the mineral's chemical stability and hardness which preserves the microtextures from multiple weathering and transporting events. Work by Mahaney (2002) has resulted in the combination of these analyses and resulting interpolations into an SGA atlas that identifies 41 separate microtextures. Some of these microtextures have been used to infer a unique depositional environment or transporting agent. One particular microtexture, V-shaped pits, has sparked debate as to which specific environment they are related.

The goal of this study is to analyze samples of sand from a wide range of environments to obtain specimens which exhibit these V-shaped pits. Once found, these samples will be subjected to statistical analyses to determine if their presence is evidence that supports the interpretation that they indicate one unique depositional environment.