Assessing Invertebrate Fossils In Developing Mitigation Plans

Abstract

Various federal, state, and local regulations have been enacted to protect fossils as important public cultural resources that provide valuable insights into the evolution of the Earth and biosphere. However, the language on nearly all these laws and statutes specify protection of vertebrate fossils; some note protection of invertebrates and plants only if the find is significant. This dichotomy exists because of the natural disparity in distribution. Invertebrates are much more common in the rock record due to the abundance of marine facies, skeleton composition (calcite and silica), and previous research focus. Furthermore, the issue may be raised on how to define and value “significance” with regards to invertebrate fossils. Most mitigation projects in California, Arizona, and Nevada impact Quaternary to late Neogene deposits and these formations tend to be more vertebrate-rich than the older units, albeit fossils are still not abundant. The majority of these units are terrestrial and comprise a variety of facies including high-sedimentation alluvial, fluvial, lacustrine, and marginal glacial. These units, in comparison to the marine realm, have a much more poorly understood invertebrate fossil record, dominated by molluscs and micro-arthropods. Therefore, the potential to gain valuable scientific data from invertebrates is proportionally higher and should be considered in developing mitigation plans. Factors to consider for defining “significance” and establishing the level of mitigation fall into four categories. First, the higher taxonomic understanding of the invertebrate phyla may not be known or may be erroneous and further collection would clarify phylogenetic relationships. Second, the resolution of biostratigraphy of the interval may be able to be refined with additional invertebrate data. Third, many of these units, in particular pedogenic horizons, may yield unique taphonomic attributes. Finally, invertebrates can yield important facies information that will become even more critical as scientists look to the rock record to understand the impact of climate change and constraints on the “Anthropocene.”

AAPG Datapages/Search and Discovery Article #90215 © 2015 Pacific Section AAPG Convention, Oxnard, California, May 3-6, 2015