Introduction

For a century or so the purpose of making grain size measurements was to determine the diameter of a representative particle. This is useful when one is studying reduction in grain size along a river (e.g. Sternberg, 1875). But it is a simplistic approach, and one is entitled to ask: Is the mean diameter the only information that we wish to get? Or does the simplicity of this first step make us think that we have now described the sand pool?

When we measure grain size, what do we really want to know? This does not refer to whether we measure the long axis or the short axis of a nonspherical particle, or whether we approximate the diameter by measuring a surrogate (such as fall velocity). Rather, we ask this question in order to get a glimpse of how far research has come in understanding transport agencies or conditions of deposition, and of the degree to which we might reasonably expect to improve our methods of environmental discrimination.

Can a set of parameters that describe a size spectrum for one sample permit us to compare this sample with some other, perhaps from a different transport or depositional environment? A positive response implies that a single sample may be adequate to describe the parent sand body.

Do we want to know about variability within the sand body, thereby requiring a suite of samples?