The proposed study examines the late Cretaceous terrestrial deposits of Montana for evidence of an impact event. Analysis of the 74 Ma Manson Impact Structure in central Iowa suggests a low-angle, oblique trajectory from the southeast predicting significant devastation in the downrange direction, i.e. towards Montana. At the time, a broad coastal plain with a diverse dinosaur fauna occupied much of the state. Today the Two Medicine and Judith River Formations represent these terrestrial environments.
Initially, the study focuses on a single, anomalous dinosaur bonebed of extraordinary size. This horizon represents a single depositional event, contains an abundance of soot, and displays a unique chemical signature. Research will examine this bonebed for a possible association with the Manson Impact. Analyses necessary to test this hypothesis include: examination of the locality for impact evidence, e.g. shocked quartz, tektites and Ir-anomaly; tracking changes in the local flora through palynological studies; survey of the bone condition for clues to their post-mortem history; and establishment of age correlations through radiometric dating and stratigraphic work. Further research extends these analyses to other promising impact-related horizons. Potential results include a better understanding of the distal effects and biotic consequences of Manson-sized impacts, a more definitive interpretation of this unusual dinosaur bonebed, a fuller description of the Cretaceous flora of the region, and opportunities to increase public awareness of the significance of impacts in the past and future.
Mail: | Dr. David J. Varricchio |
Earth Sciences Department | |
Montana State University | |
Bozeman, MT 59717 |
E-mail: | djv@montana.edu |
Phone: | (406) 994-6907 |
FAX: | (406) 994-6923 |