Theses and Dissertations at Montana State University (MSU)
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Item Hydrothermal influences on the Holocene environmental history of central Yellowstone National Park(Montana State University - Bozeman, College of Letters & Science, 2020) Schiller, Christopher Michael; Chairperson, Graduate Committee: Cathy Whitlock; Cathy Whitlock, Kathryn L. Elder, Nels A. Iverson and Mark B. Abbott were co-authors of the article, 'Erroneously old radiocarbon ages from terrestrial pollen concentrates in Yellowstone Lake, Wyoming, USA' in the journal 'Radiocarbon' which is contained within this dissertation.; Rosine Cartier, Cathy Whitlock and Lisa A. Morgan were co-authors of the article, 'Multi-proxy record of Holocene paleoenvironmental conditions from Yellowstone Lake, Wyoming, USA' submitted to the journal 'Quaternary science reviews' which is contained within this dissertation.; Cathy Whitlock, Sabrina R. Brown and Petra Zahajska were co-authors of the article, 'Holocene geo-ecological evolution in Lower Geyser Basin, Yellowstone National Park' submitted to the journal 'Geological Society of America bulletin' which is contained within this dissertation.; Cathy Whitlock, Mio Alt and Lisa A. Morgan were co-authors of the article, 'Vegetation responses to Quaternary volcanic and hydrothermal disturbances in the northern Rocky Mountains and Greater Yellowstone Ecosystem' in the journal 'Palaeogeography, Palaeoclimatology, Plaeoecology' which is contained within this dissertation.The postglacial vegetation history of Yellowstone National Park is well established by past paleoecological studies, but the role of hydrothermal activity--pervasive in areas of the park--in that history is poorly understood. To address this unknown, pollen and charcoal records were examined from lake sediment cores at multiple sites in central Yellowstone National Park to reconstruct Holocene vegetation. First, radiocarbon ages obtained from pollen concentrates were compared with other age controls at Yellowstone Lake, revealing ages that were up to 4300 cal years too old. Erroneous ages were due to either old carbon contamination from magmatic or hydrothermally degassed CO 2 or old pollen reworked from an unknown source. Second, Holocene vegetation and fire history were reconstructed from a Yellowstone Lake sediment core. The record was characterized by gradually increasing closure or extent of Pinus contorta forest and increasing fire activity to the present, consistent with reduced summer insolation creating cooler, effectively wetter conditions in central Yellowstone National Park. No impact of hydrothermal activity was detected in the regional Holocene-long vegetation and fire histories. Third, Holocene vegetation and fire history were studied at Goose Lake in Lower Geyser Basin, an area with abundant modern hydrothermal activity. The vegetation and fire history diverged from the regional trend at 3800 cal yr BP, synchronous with geochemical indicators indicating reorganization of hydrothermal activity in the basin, suggesting an abrupt ecological response to shifting hydrothermal activity. Finally, a variety of volcanic and hydrothermal processes were investigated as disturbances in the Northern Rocky Mountains and Yellowstone National Park through high-resolution pollen analysis. Hydrothermal explosion deposits were found to be synchronous with conifer morality, in some records, indicating that the effects of hydrothermal explosions are local and short-lived. At a regional scale, it is evident that vegetation changes were chiefly responding to millennial-scale, insolation-driven climate change. However, the impacts of hydrothermal activity were locally important where pervasive, as in Lower Geyser Basin, and in areas recently affected by hydrothermal explosions.Item Late Holocene vegetation and fire history in subalpine forests of northwestern Montana(Montana State University - Bozeman, College of Letters & Science, 2020) Sly, Shelby Fulton; Chairperson, Graduate Committee: David McWethyMid-to high- elevation forests of the Northern Rocky Mountains are dynamic systems that change in time in response to climate, disturbance and human activities. Climate models suggest these ecosystems will experience warmer temperatures, decreased spring snowpack, drier summers, and longer fire seasons, highlighting a need to better understand how these systems respond to changing climatic conditions. Sediment cores were extracted from two lakes in the Mission and Reservation Divide Mountains of Montana and analyzed for pollen and macroscopic charcoal to reconstruct fire and vegetation histories. The records from Mud Lake and Three Lakes Peak span the last 5400 and 4600 years respectively, and highlight the long-term persistence and relative stability of closed, mixed conifer/subalpine forests. During the mid-Holocene (approx. ca. 5000 yr BP), Pinus pollen percentages increased, suggesting closed forests which then transitioned to mesic forest of Pinus, Abies, and Picea over the last ca. 4000 years. Modern forests established between 3500-3000 cal yr BP at both sites. Both sites experience elevated fire activity during the Medieval Climate Anomaly c. 1000-900 cal yr BP which is consistent with other sites in the region. While relatively infrequent (2-4 fires per millennia), wildfires played a role in maintaining early successional vegetation (Poaeceae, Alnus spp.) and taxa that benefit from post-fire reduction in competition such as five-needle pines. Paleoenvironmental records from these two sites indicate subalpine forests of northwestern Montana persisted with relative stability throughout the mid to late-Holocene. With projections for increased warming, longer fire seasons and the possibility for increased occurance of short-interval fires in higher elevation ecosystems of the Northern Rocky Mountains, subalpine forests may become vulnerable to rapid transitions to different forest types or even non-forest systems.Item Late Holocene climate, fire, and vegetation history on the northern range, Yellowstone National Park(Montana State University - Bozeman, College of Letters & Science, 2019) Firmage, David Samuel; Chairperson, Graduate Committee: Cathy WhitlockYellowstone National Park is an iconic natural landscape that encompasses unique geologic features as well as a diverse and ecologically important flora and fauna. The ecological resilience of the Northern Range of the park, home to the park's ungulate herds, faces an uncertain future with a projected warming climate over the next century. Understanding the variability of vegetation organization in response to past changes in climate can help park managers plan for future climate scenarios. Lake sediment cores from two lakes were collected, analyzed for pollen type, charcoal accumulation and lithological components, and compared with other studies to highlight commonalities in fire-histories and vegetation trends across the Northern Range over the past 4000 cal yr BP. Foster Lake the records suggest fire-episodes and changes to lake productivity and between ~3500-2900 cal yr BP, large intense fire-episodes between ~2500-2150 cal yr BP, ~1000 cal yr BP and frequent large fire episodes from ~700 cal yr BP to the present day. Floating Island Lake records between ~4000-3000 cal yr BP suggest the site experienced infrequent, large fire episodes concurrent with periods of protracted drought and decreases in water level. Between ~3000-1500 low intensity fire episodes were common, punctuated by infrequent large fire episodes at ~2900, ~2250, ~2050 and ~1880 cal yr BP. During the last ~1ka two fire episodes were recorded at Floating Island Lake, at ~1030 cal yr BP coincident with the Medieval Climate Anomaly, and 270~ cal yr BP during the Little Ice Age. A comparison of fire histories from studies spanning the Northern Range shows that during periods of protracted drought large fire episodes are common across the landscape, and that during periods of moderate climate fire size and severity is likely modulated by local site controls such as topography and vegetation structure. This study shows that fire episodes in the Northern Range have occurred as a spatial and temporal mosaic, and are likely to continue to do so. Additionally, this study increases our understanding of how vegetation structure and fire regimes in the Northern Range have varied as a result of a range of climate conditions in the past. Such baseline information helps us anticipate some of the ecological responses that may occur in the decades ahead with global warming.Item Osteology, phylogeny, taphonomy, and ontogenetic histology of Oryctodromeus cubicularis, from the middle Cretaceous (Albian-Cenomanian) of Montana and Idaho(Montana State University - Bozeman, College of Letters & Science, 2017) Krumenacker, L. J.; Chairperson, Graduate Committee: David Varricchio; David J. Varricchio, Chris Organ, Clint Boyd and Brooks Britt were co-authors of the article, 'Osteology and phylogeny of the neornithischian dinosaur Oryctodromeus cubicularis from the middle Cretaceous (Albian-Cenomanian) of Montana and Idaho' submitted to the journal 'Journal of vertebrate paleontology' which is contained within this thesis.; David J. Varricchio, John Wilson and Ashley Ferguson were co-authors of the article, 'Taphonomy of Oryctodromeus cubicularis from the mid-Cretaceous (Albian-Cenomanian) of Idaho, and additional Oryctodromeus burrows from Idaho and Montana' submitted to the journal 'Palaeogeography, palaeoclimatology, palaeoecology' which is contained within this thesis.; David J. Varricchio, John R. Horner and Kelli Taddy were co-authors of the article, 'Ontogenetic histology and growth of the neornithischian dinosaur Oryctodromeus cubicularis from the middle Cretaceous (Albian-Cenomanian) of Montana and Idaho' submitted to the journal 'Journal of vertebrate paleontology' which is contained within this thesis.Oryctodromeus is a small bipedal dinosaur known from middle Cretaceous (95-100 My) Wayan Formation of Idaho and the Vaughn Member of the Blackleaf Formation of Montana. This taxon is hypothesized to be a burrowing dinosaur, which cared for its young within these burrows. This dissertation is a broad three-part treatment of this taxon, and excepting the introductory and concluding chapters this dissertation consists of three main chapters. Chapter two describes the osteology and phylogenetic relationships of this animal. Notable features of the Oryctodromeus skeleton described include a network of ossified tendons along the vertebral column that completely ensheath the tail, a long tail that forms more than half the length of the animal, and unusual femoral heads whose morphology may be related to burrowing behavior. The first full skeletal and skull reconstructions of this animal are presented. Chapter three investigates patterns of preservation of Oryctodromeus. Data suggests that preservation of single to multiple individuals of this taxon typically occurred in burrows that may be difficult to impossible to recognize in the fossil record. New examples of burrows from Oryctodromeus from the Vaughn and Wayan, as well as additional evidence for social behavior, are also described. A third chapter details the ontogenetic histology, growth rates and patterns of skeletal fusion based on seven limb elements (femora and tibiae) from different individuals. Based on the data in this dissertation, three growth stages can be recognized in Oryctodromeus based on bone histology. Juveniles are defined by more rapidly growing fibrolamellar tissue, sub-adults are defined by a cortex of inner fibrolamellar tissue and outer zonal parallel fibered tissue, and near-adult individuals have tissue similar to sub adults with dense avascular bone in the outermost cortex that signals a decrease in growth rate. LAG's suggest a minimum age of six to seven years for more mature individuals. Patterns of neurocentral fusion in Oryctodromeus appear similar to those of crocodylians and some other small ornithischians, while the growth rates of Oryctodromeus appear slower than those of some dinosaurs, but similar to taxa such as Orodromeus and Tenontosaurus.Item Description and ontogenetic assessment of a new Jehol microraptorine(Montana State University - Bozeman, College of Letters & Science, 2014) Poust, Ashley William; Chairperson, Graduate Committee: David VarricchioFossils from the Jehol Group (Early Cretaceous, Liaoning Province, China) have greatly contributed to our understanding of the morphology and diversity of Paraves, the group of dinosaurs including sickle-clawed dromaeosaurs, large-brained troodontids, and avialians, the ancestors of modern birds. However, many taxa are represented by only a few specimens of unclear ontogenetic age. Without a thorough understanding of ontogeny, the evolutionary relationships and significance of character states may be obscured within paravian dinosaurs. A complete specimen of a new taxon of microraptorine dromaeosaur, Wulong bohaiensis gen. et sp. nov., from the Jiufotang Formation (upper Jehol Group) exhibits clearly juvenile morphology. The dinosaur is small and preserved in articulation on a single slab. It has microraptorine features such as a subarctometatarsalian foot, a short first manual digit, and a prominent tubercle on the pubis. Phylogenetic analysis substantiates this assignment. It also possesses more than 29 tail vertebrae, inclined pneumatic foramina on its dorsal vertebrae, and an unusually large coracoid fenestra, which with other features argue that it is a new taxon. This individual shows many osteological markers of immaturity identified in other archosaurs. Skull elements, all visible neurocentral sutures, pubes, and proximal tarsals remain unfused. Grainy surface texture of the cortical bone and poor ossification of long bone articular surfaces further supports an immature status. Histologic samples of the tibia, fibula, and humerus of this individual (the first microraptorine theropod to be sampled) confirm that it was around a single year in age and still growing at death, but that the growth had slowed. This slow down in growth is interesting in light of the presence of pennaceous feathers extending from the fore- and hind-limbs and, notably, two long plumes extending more than 12 cm from the tip of the caudal series. This indicates that presence of a variety of feather types, including filamentous feathers, pennaceous primaries, and long rectrices, likely used for ornamentation, preceded skeletal maturity and full adult size.Item Paleoenvironment and taphonomy of the fauna of the Tullock Formation (early Paleocene), McGuire Creek area, McCone County, Montana(Montana State University - Bozeman, College of Letters & Science, 1992) Katsura, YoshihiroItem Effects of depositional environment, asssemblage taphonomy and diagenesis on vertebrate skeletal preservation in a crevasse splay sandstone, upper Cretaceous Hell Creek Formation, eastern Montana(Montana State University - Bozeman, College of Letters & Science, 2013) Yamamura, Daigo; Chairperson, Graduate Committee: James G. SchmittAlthough a great deal of paleontological information is derived from analyzing fossilized skeletal remains, the fossilization process of vertebrate skeletal remains is poorly understood. Depositional environment, taphonomy and diagenesis of an assemblage of vertebrate skeletal elements from a sandstone in the Late Cretaceous Hell Creek Formation are investigated in order to decipher relations between sandstone diagenesis and skeletal element fossilization. Fieldwork included taphonomic data collection, section measurement and description as well as sample collection. The rock and fossil bone samples were analyzed by petrography, cathodoluminescence, scanning electron microscopy (SEM) and X-ray diffractometry (XRD). The depositional environment including the fossil assemblage is interpreted as a crevasse splay based on the facies association of repeating sequences of mudrock and fine sandstone overlying channel and levee deposits. Taphonomic data suggest the bones were exposed on the surface up to 15 years before burial, and the assemblage is time-averaged. Although sandstone including the fossil bones indicates physical compaction, fossil bones do not exhibit signs of compaction. Barite is an unusual authigenic mineral found in fossil bones, suggesting collagen degradation during early diagenesis facilitated unique diagenetic microenvironment within bones. Calcite and siderite cements were precipitated multiple times, suggesting alkaline pore-fluid conditions were common during diagenesis. However, oversized pores and highly altered grains indicate that porefluids were acidic during late diagenesis; acidic pore-fluid conditions are likely due to the organic acid produced by degradation of organic molecule at higher diagenetic temperatures. Fossil bone minerals are altered due to 1) early pore-fluid infiltration combined with dehydration/rehydration processes, 2) saline pore-fluid infiltration and 3) increased temperature and pressure during deeper burial. This study demonstrates that petrography, XRD and SEM/EDS together can help decipher the diagenetic history of fossilized bones. In order to maximize the information, not only the fossil bones, but surrounding rocks need to be analyzed because surrounding rocks record different sets of diagenetic processes such as calcite precipitation in the vadose zone, siderite precipitation in the phreatic zones, acidic pore-fluid condition during mesogenesis.Item Application of sequence stratigraphy to the nonmarine Upper Cretaceous Two Medicine Formation, Willow Creek anticline, northwestern, Montana(Montana State University - Bozeman, College of Letters & Science, 2007) Shelton, Jessica Anne; Chairperson, Graduate Committee: David W. BowenThe purpose of this research is to create a sequence stratigraphic framework for the Upper Cretaceous Two Medicine Formation exposed on the Willow Creek anticline along the western flank of the Sweetgrass Arch in Montana. The framework developed at this site was then correlated to the framework developed at the type section of the Two Medicine Formation located near Cut Bank, Montana. This research is significant because: 1) it provides a chronostratigraphically-significant framework within which Egg Mountain dinosaur nesting sites can be correlated, providing an important contribution to paleontologists interpreting this site, and 2) within this framework changes in fluvial style are related to relative sea level and a major change in tectonic style in western Montana (emplacement of the Boulder batholith and several volcanic events). In this study, surface outcrops were used to describe and correlate the Two Medicine Formation. The Willow Creek anticline area demonstrates similar changes in stratigraphic architecture through time as have been described at the upper discontinuity of the Two Medicine Formation type section.Item Sequence stratigraphic analysis of the Fox hills and Hell creek formations (maastrichtian), eastern Montana and its relationship to dinosaur paleontology(Montana State University - Bozeman, College of Letters & Science, 2004) Flight, Jennifer Noel; Chairperson, Graduate Committee: James G. SchmittThe Upper Cretaceous Hell Creek Formation near the Fort Peck Reservoir, eastern Montana, has received significant investigation due to the large variety and exceptional preservation of included fossil material. Workers have focused mainly on taphonomic and paleontologic issues, but lack of a stratigraphic framework within which to place fossil finds in order to address questions of evolution, population diversity, and paleoecology. This study uses sequence stratigraphy to correlate within the Fox Hills and Hell Creek Formations such that paleontologic data can be interpreted in relation to a series of linked depositional environments and their relationship through time. Four key surfaces are present in the study area. First is a sequence boundary capping the Fox Hills marine shoreface strata. Incision occurs locally at this boundary and the resulting topography is filled by incised valley-fill strata of the Colgate Member of the Fox Hills Formation (lowstand and transgressive systems tracts). The second key surface is a flooding surface internal to the transgressive systems tract which is associated with extensive Skolithos burrows into the Colgate Member below (Glossifungites surface?). This flooding surface separates white, trough cross-stratified Colgate sandstone from thin carbonaceous, bioturbated and pedogenically altered units of the lower Hell Creek Formation. Capping this carbonaceous member is the maximum flooding surface which separates transgressive deposits below from highstand deposits above. Highstand deposition of the lower Hell Creek consists of the high accommodation, estuarine, inclined heterolithic sandstone which contains the most complete and associated Tyrannosaurus rex. The fourth key surface separates lower Hell Creek estuarine deposits from upper Hell Creek fluvial system deposits. These fluvial deposits consist of mixed sandstone, siltstone and mudstone which are interpreted to have formed on a flood plain through processes associated with meandering stream deposition and pedogenic alteration. These deposits reflect a return to low accommodation depositional patterns (lowstand systems tract). Changes in accommodation during Maastrichtian time, as interpreted from regional stacking patterns, facies changes and facies tract dislocations can be used in conjunction with taphonomic data from paleontologic sites in order to understand and predict the nature of preservation and distribution of fossil materialItem An ontogenetic series and population histology of the ceratopsid dinosaur Einiosaurus procurvicornis(Montana State University - Bozeman, College of Letters & Science, 2010) Reizner, Julie Ann; Chairperson, Graduate Committee: John R. HornerHistologic studies have been utilized in paleontology to determine rates of growth for several dinosaur taxa, but members of the otherwise relatively well-known family Ceratopsidae have largely been excluded. A monodominant bonebed containing remains of the centrosaurine ceratopsid Einiosaurus procurvicornis Sampson 1995, ranging from juveniles to putative adults, has been found in the Upper Cretaceous Two Medicine Formation of northwestern Montana. This bonebed represents a drought-induced assemblage, and is hypothesized to represent a single population. The full available range of sizes of tibiae (N = 16) were sectioned and bone histology examined. Tissue types and degrees of remodeling are discussed, and growth lines are used to determine ages at time of death of the individuals. The rate of growth for Einiosaurus peaks at about 3-5 years of age, at which time growth slows, suggesting that this may be the age that reproductive maturity is reached. The nature of the bone tissue suggests that growth in Einiosaurus is still relatively rapid in even the largest specimens, indicating that a fully adult tibia has not been recovered from the studied bonebed, and this bonebed is biased toward juveniles and subadults. Since the bonebed is a snapshot of a standing herd, population dynamics of Einiosaurus, such as survivorship and behavior, are assessed. This information on growth dynamics and life histories of a species has implications for future taxonomic resolution and morphometric studies of ceratopsid dinosaurs, and marks the first study on population histology of a large-bodied herbivorous dinosaur.