Tales from two shell beds: The role of sedimentation regime in the preservation of high-productivity skeletal concentrations
Dr. Madeline Marshall
Albion College
Abstract
High-productivity systems are known to host a diversity of life, along with distinctive sediments such as phosphorites, organic-rich muds, and glauconitic sands. Additionally, elevated productivity has the potential to influence concentrations of skeletal material through multiple interacting ecological, taphonomic, and diagenetic effects in the seabed. Previous study of the Permian Phosphoria Rock Complex (PRC) of the Intermountain West has focused on these variables, finding preservation of skeletal concentrations to be dictated largely by the sequence stratigraphic context and duration of hiatuses in sedimentation. The current study considers another key component to more fully understanding the problem of preservation in high-productivity systems: sedimentation regime and input of clastics. Variation in the amount of dilution by clastics that high-productivity systems experience can have profound impacts on the subsequent preservation of fossil material: sediment starvation often occurs in tandem with low-energy and dysoxic conditions, while systems rich in clastic input are typically higher energy and better oxygenated. A comparative analysis of the sediment-starved Permian PRC and the sediment-rich late Jurassic record of the southern Morondava Basin, Madagascar, is a first step in tackling this problem.
BIO
Madeline joined the faculty of Albion College in Michigan as Assistant Professor of Earth & Environment in 2019, and is greatly enjoying teaching in the classroom and field and leading research in sedimentology/stratigraphy and paleobiology with undergraduates. Currently, she is actively working with student researchers on (1) detailed sedimentology, paleontology, and diagenesis of the Cretaceous record from Ampolipoly, western Madagascar, (2) stratigraphic correlation within the Cretaceous Morondava Basin, Madagascar, involving translation of historic data from French, and (3) description and identification of fossils from the Permian Phosphoria Rock Complex of Idaho. Another recent project was a comparative sedimentology study of phosphorite hard grounds from the Permian Phosphoria Rock Complex and recent offshore California, and her lab group presented on much of this work at GSA Connects 2021 in Portland. After completing her Ph.D. in stratigraphy and paleobiology in the Department of the Geophysical Sciences at The University of Chicago, working with Susan Kidwell, she was a visiting lecturer in the Geology Department at Cornell College in Mount Vernon, Iowa for 2018-2019.