GSA Connects 2021 in Portland, Oregon

Paper No. 177-1
Presentation Time: 1:35 PM


CRAMER, Bradley, Department of Earth and Environmental Sciences, University of Iowa, 115 Trowbridge Hall, Iowa City, IA 52242

A single sentence from the International Stratigraphic Guide has become the central impediment to integrated high-temporal-resolution study of the stratigraphic record.

Whenever the lowest appearance of successive segments of an evolutionary lineage (FAD) over the area of their distribution can be considered as essentially synchronous, lineage zones have strong time significance and approach chronostratigraphic units

Whereas this sentence may have been valid decades ago when there were no non-biostratigraphic, chronostratigraphic tools available to test the synchronicity of biostratigraphy, and therefore test this hypothesis, this sentence is increasingly problematic. First, the International Commission on Stratigraphy, and its component subcommissions have tried extremely hard to utilize primarily cosmopolitan species as important boundary markers. As such, the “area of their distribution” is closer to global than regional for most species used as tools for correlation of GSSPs, yet an a priori assumption has developed over the past fifty years that somehow chronostratigraphically important species reach nearly global distribution instantaneously, even when integrated high-resolution studies demonstrate this to be patently untrue.

Biostratigraphy is, and will remain, the primary tool of global correlation because it is the only chronostratigraphic tool that provides unique information. All other tools are either binary (paleomagnetism), or wiggles (geochemistry). However, the potential temporal resolution of these tools is necessarily better than biostratigraphy and absolutely must be fully, and correctly, integrated into chronostratigraphic studies. The solution is not a question of which tool is “right”, the point of the exercise is to study the EVENT in Earth history, and it is only through detailed, systematic, integration of all chronostratigraphic tools and operating from an equal understanding of all disciplines that we can unlock the finest detail from the stratigraphic record.