Covariation in macrostratigraphic and macroevolutionary patterns in the marine record of North America
Students of Earth history have long recog- nized the correlation between the quantity of preserved sedimentary rock and the diversity of life recorded as fossils. But paleontologists have yet to determine whether this pattern refl ects a causal relationship or a unidirec- tional sampling bias in fossil data imposed by preserved rock quantity. Distinguishing between these two alternatives has been com- plicated by the fact that many of the basic patterns of paleontologic and lithologic co- variation have yet to be quantifi ed rigorously. Here we present the fi rst analyses of the co- variation between the macrostratigraphic and macroevolutionary histories of North America based on geographically and tem- porally explicit co-occurrences of rocks and fossils. The analyses use independent quan- titative summaries of the stratigraphic and fossil records by integrating the Paleobiology Database (PaleoDB) and Macrostrat, a mac- rostratigraphy database for North America, which allows a more direct comparison of the stratigraphic and biological histories of the continent than has heretofore been possible. Within the Macrostrat database, the rock re- cord is divided into discrete packages of sedi- ment that are bound by hiatuses resolvable at the stage-level. Using per interval, per pack- age rates of sediment package initiation and truncation, and genus fi rst and last appear- ances (herein regional origination and extinc- tion), we fia substantially stronger positive correlation between sediments and biology for extinction-like parameters than we do for origination-like parameters. Four of the largest coincident pulses of regional extinc- tion and sediment truncation occur during the widely recognized end-Ordovician, late Permian, end-Triassic, and end-Cretaceous mass extinction intervals. A further compari- son of the global ranges of North American genera to North American macrostratigra- phy indicates that the regional and global extinction of genera are more likely to oc- cur in the same stage than are global and regional originations. Together, these results suggest that our general understanding of biodiversity dynamics from the fossil record may not be strongly biased by the preserva- tion of sediments and leaves open the pos- sibility that certain large perturbations to the Earth system are responsible for major changes of state in both the sedimentary and biological systems.