Introduction

Geologists have studied most aspects of sediments in order to elucidate characteristics significant in determining the environment of deposition. Traditionally the lithotype + biotype = rock approach has led to the concept of lithotopes and biotopes (environmental derivatives of lithotype and biotype), and the very successful concepts of lithostratigraphy, biostratigraphy and chronostratigraphy. It is clear that no single parameter can be used to distinguish all depositional environments, but if a number of parameters are measured, chances of error may be reduced. Unfortunately, which parameters are of most importance is unclear. Much of this uncertainty exists because sampling of the environments has been inadequate, and available data bases are poorly defined. Moreover, conclusions are rarely based upon the principles of experimental design and hypothesis testing.

The accessibility of samples strongly influences the choice of a sampling design, and, for the determination of depositional environment this is a particularly significant constraint. If outcrops are studied, a wealth of information relating to paleoenvironments becomes available; if conventional cores are studied the quantity of possible information is reduced, and even further so by sidewall cores. Unfortunately, the most abundant kind of sample available to the subsurface geologist is the collection of cuttings from the rotary bore. The information available from cuttings is indeed minimal, and even with good samples the derived information may be of reduced value due to caving and other problems connected with taking samples. Unfortunately for the subsurface geologist well cuttings with occasional sidewall cores are the rule rather than the exception.