8 - Megabiases I: cycles of preservation and biomineralization

Summary

… your Father confessor trembles for you.

Charles Darwin to T. H. Huxley regarding Richard Owen (Desmond and Moore, 1991)

Introduction

The concept of scale and its effect on measurement of stratigraphic completeness was introduced in Chapter 7. Scale is no less important to the measurement of cyclic change recorded in the stratigraphic record. As a hypothetical example: for practical purposes one would not use a meter stick to measure a sine wave with a wavelength of several kilometers. More importantly, if one used a meter stick, it would only detect wavelengths of about the same length as the meter stick, and wavelengths of much shorter or longer duration would go undetected.

It is no less true of the study of cyclicity in the geological record. What if one were attempting to document cyclic climate change through time? If each cycle were of several million years duration, one would not even see any change if the measuring scale was one of human perception (one or a few generations). Although these cycles are highly appreciated in terms of sea-level and climate change, they may produce potential megabiases in the fossil record that have not been fully explored and many of which require much more documentation.

This is fundamentally why the geological record is so important: there are many cycles of various – and often interrelated – phenomena in the geological record and these cycles act, and interact, at different frequencies (wavelengths) or scales that are mostly undetectable over geologically short durations of time.