METHODS OF MICROVERTEBRATE SAMPLING AND THEIR INFLUENCES ON TAPHONOMIC INTERPRETATIONS

Abstract

Localized accumulations of small vertebrate fossils are relatively common in the Hell Creek Formation (latest Maastrichtian–Paleocene) and have traditionally been collected using nonstandardized field methods. The lack of established protocols has resulted in biased datasets and assemblage interpretations. Two commonly used collection methods were compared from two different microvertebrate localities in the Upper Cretaceous part of the Hell Creek Formation of southeastern Montana in order to identify their influence on taphonomic interpretations. The first of these methods was surface collection, in which weathered specimens were picked from the surface of the rock and in talus piles. This method commonly involves the selection and collection of larger and more easily identifiable specimens. The second method used in this study was quarrying and disaggregation, which requires excavation, collection, and total screen rinsing of a large volume of rock; this method was utilized in order to recover all fossils present. Both methods were applied at a sandstone-dominated and a mudstone-dominated site to assess an absolute concentration of fossils for each technique. Results of a quantitative analysis of these two common collection methods demonstrate how each one influences fossil recovery according to shape and size by skewing the characteristics of collected fossil assemblages and the taphonomic interpretations of microvertebrate accumulations. Although the study sites reflect only two possible types of microvertebrate localities, the results are applicable to many microvertebrate studies.