Quantification of ichnological, paleoecological, paleohydrological, and paleoclimatological information from the Upper Jurassic Morrison Formation

This dissertation takes a multifaceted approach to interpreting paleoenvironments and paleoclimate represented by the strata of the Morrison Formation (MF). The MF has been the subject of geological and paleontological investigations for well over a century, but a number of confounding factors have limited interpretations. One problem with interpreting MF ichnology is uncertainty about the sedimentary conditions under which deep dinosaur tracks were made. To solve this problem, I developed new methods to measure trace fossils, including footprints. I used multistripe laser triangulation scanning to create three-dimensional digital models of traces, from which I improved precision of traditional ichnological techniques. I also performed neoichnological experiments with elephants to collect empirical trackmaking data, to which I applied multiple regression to derive a quantitative relationship between physical trackmaking variables. Results showed that many deep sauropod tracks were created in near saturated conditions.;Megafaunal track preservation was one factor taken into consideration when interpreting paleohydrology from moisture regimes represented by trace-fossil assemblages. I demonstrated the usefulness of ichnological moisture regimes by interpreting ichnocoenoses in MF avulsion deposits in the Bighorn Basin. I found a regular pattern of moisture profiles associated with crevassing that can be used to identify avulsion deposits in future ichnological studies.;Ichnological moisture regimes were incorporated with other pedogenic features to develop a soil moisture index that was combined with measures of carbonate content, carbonate mineralogy, total organic carbon, and stable isotopes of carbonates and organic carbon to construct a detailed vertical profile through the MF in the Henry Mountains, Utah. This profile is useful for paleoclimatic and paleoenvironmental interpretations as well as for correlation to marine isotope records. I compared the vertical profile to paleoecological patterns determined from food-web network analyses and found a possible correlation between a global shift in organic carbon isotopes and an episode of biotic turnover. I also found that MF food webs were extremely stable, a factor that may have contributed to the success of dinosaur-dominated ecosystems during the Mesozoic.