THERE IS NO PHANEROZOIC ROCK RECORD BIAS

Sedimentary rocks host most of the Earth’s energy resources and provide a rich long-term archive of global climate change, biological evolution, and many aspects of how plate tectonics processes have operated over time. Nevertheless, ever since Darwin famously described the geological record as a “history of the world imperfectly kept” and, as a corollary, proclaimed the fossil record to be inadequate for studying the evolutionary history of life, many paleontologists and geologists have viewed the sedimentary rock record with considerable trepidation. Over the past 36 years, many studies have seemingly supported this pessimistic view of the geologic record by demonstrating a significant positive correlation between short- and long-term patterns of biodiversity among marine animals, estimated on the basis of the first and last appearances of taxa in the fossil record, and the amount of preserved sedimentary rock. With very few recent exceptions, these correlations have been interpreted entirely within the confines of Darwin’s “tattered manuscript” simile, namely that there is as a dominant signal of degradation that is imposed after the formation of what was once a much more complete rock record.

Although it is inevitable that the amount of rock originally deposited in a geological time interval must decline over time because any rock, once formed, can be destroyed by weathering and erosion or be completely transformed by metamorphism, it is not necessarily the case that degradation processes are the dominant signal in the surviving rock record, or even that temporal variability in the amount of sedimentary rock serves as a significant source of “bias” in our sampling of the fossil record. Here we address the long-standing, but largely untested, assumption that there is a dominant signal of degradation in the marine sedimentary rock record and that this degradation has imposed a significant source of bias in the preservation of Earth’s surface environment generally, and in estimates of marine animal biodiversity specifically. We demonstrate a Phanerozoic trend of decreasing marine sediment quantity that reflects true changes in the extent of marine flooding of the craton. We also use partial correlation to show that the extent of marine flooding influences generic marine diversity independent of sampling effects.