The range-through method and first-last appearance data in paleontological surveys

Abstract

The quality of the information yielded by stratigraphic and paleoecologic studies based on microfossils is often poor due to spotty recovery of taxa. Thus, downcore sequences contain many null records between the first appearance (FA) and the last appearance (LA) of the species. Cheetham and Deboo (1963) suggested the use of the range-through method (i.e., a species is considered present in a sample if found both above and below it, even if it was not found within the sample) as a means of smoothing these spotty data sets and, when biostratigraphic conclusions are sought, to counteract the effect of environmental influences (Hazel, 1970). The technique was subsequently adopted in many reports and incorporated in numerical methods for biostratigraphic work (e.g., see review in Brower, 1985).