Both fossil and living foraminifera have been investigated in this study. Late Cretaceous age foraminiferal assemblages have been used to examine the relationship between high-frequency sea level change, biotic response and paleoceanography, in the U.S. Western Interior Sea. Living planktic foraminifera were also studied in order to test a novel hypothesis on the evolution of cellular organelles known as fibrillar bodies. The major findings of this dissertation are: (1) The third-order Greenhorn tectono-eustatic cycle (late Cenomanian-middle Turonian) in the Cretaceous Western Interior Basin is superposed by fourth-order relative sea level cycles and fifth-order parasequences that are reflected in foraminferal assemblages and carbonate content of shales and mudrocks. The study interval includes the Cenomanian/Turonian (C/T) boundary event (93.3 Ma) and the highest stand of sea level in the western interior during early Turonian time. Calcareous benthic foraminiferal assemblages show marked shifts in taxon dominance which is interpreted as ecologic replacement indicating change from a food-controlled to an oxygen-controlled environment. Acmes of the genus Gavelinella are related to the initiation of fourth-order transgressive episodes early in the third-order transgression and late highstand phases of the Greenhorn Cycle. The rapid proliferation of this taxon is thought to be a response to pulses of food. Warm, oxygen-poor Tethyan waters spread across the WIS during the late transgression and highstand phases of the Greenhorn Cycle. A rapid ecologic shift to Neobulimina dominance is the benthic foraminiferal response to this Tethyan incursion. The relative abundance of Neobulimina shows a highly significant correlation to carbonate content (p $<$ 0.01), which is a proxy for warm, more normal marine water masses entering the WIS from the south. Tethyan water masses were replaced by those of Boreal affinity and agglutinated benthic foraminiferal assemblages during the regressive phase of the Greenhorn Cycle. Variations in benthic foraminiferal assemblage composition mirror changes in water mass salinity, oxygenation, circulation and productivity. Foraminiferal data from the western margin of the WIS support GCM models of estuarine circulation. (2) Fibrillar bodies are organelles present in the cytoplasm of all planktic foraminifera. I propose that they may have originated as symbiotic bacteria. Those in Pulleniatina obliquiloculata are squat to elongate ovoids and elongate rods with a length of 2-15 $\mu$m and a diameter of 2-5 $\mu$m. One, sometimes two such bodies (possibly products of binary fission) are bounded by a membrane-like vacuolar structure. They have an electron-lucent (DNA-containing?) central region, ribosome-like and storage-like granules, and are commonly enclosed within a vacuole. (Abstract shortened by UMI.)

The timing and mechanisms responsible for the expansion of C4 grasses have been a topic of considerable debate over the last two decades. Although abundant evidence indicates that there was a worldwide, rapid increase in C4 ecosystems (RICE) in the late Miocene, recent studies from the Great Plains and the Barstow Formation suggest that there may have been a significant amount of C4 biomass prior to the RICE event. This study examines stable carbon isotopic ratios of herbivore tooth enamel of 89 individuals from the Dove Spring Formation of southern California, which is geographically close to and geologically younger than the Barstow Formation. Taxa analyzed in this study include the Antilocapridae, Castoridae, Camelidae, Equidae, Gomphotheriidae, Merycoidodontidae, and Rhinocerotidae families. The enamel δ13C values of all taxa sampled are -10.1 ± 1.1 ‰ (n=89), ranging from -13.3 to -6.7 ‰. Most studies have used -8 ‰ as the cutoff for a pure C3 diet. However, a cutoff value of -8 ‰ for a pure C3 diet is reliant on the modern atmospheric δ13C value. Proxy data indicate that the δ13C value of atmospheric CO2, the carbon source of terrestrial plants, has varied significantly in the geologic past, leading to corresponding changes in the δ13C of plants and ultimately tooth enamel. The estimated δ13C value of atmospheric CO2 in the middle to late Miocene was -5.8 ± 0.2 ‰, making the pure C3 diet cutoff value higher than the modern value by ~2 ‰. With a higher end member δ13C value for a pure C3 diet, much of the reported evidence of an early spread of C4 grasses in areas such as the Great Plains and southern California may be a false signal from water-stressed C3 plants and the amount of C4 biomass in the geologic past may have been greatly over-estimated. After accounting for the changes in the δ13C of atmospheric CO2, enamel-δ13C values from the Dove Spring Formation indicate that late Miocene herbivores in the area had primarily C3 diets and lived in an environment dominated by C3 plants. Re-evaluation of previously published enamel-δ13C data from the nearby Barstow Formation to account for the carbon isotopic difference between the middle Miocene and modern atmospheric CO2 also shows that herbivores living in the area in the middle Miocene had C3-based diets. Serial isotope data from the teeth from the Dove Spring Formation revealed little or no intra-tooth δ13C variations, confirming that these ancient herbivores consumed C3 plants year round. The lack of seasonal signal in the carbon isotope data of the serial samples provides further evidence that there were little or no C4 plants in local habitats of southern California in the middle and late Miocene. If the C4 photosynthetic pathway did spread to southern California prior to the rapid increase in C4 ecosystems in the late Miocene the herbivore taxa sampled did not incorporate C4 biomass into their diets, possibly as a result of selective feeding. The results of the stable carbon isotopic analysis, along with the evidence from the rock record, the life habits of the fossil taxa present—both grazers and browsers—indicate that the area had a very different environment in the late Miocene. The carbon isotope data suggest that the environment in the El Paso Basin in the middle to late Miocene was likely consisted of diverse habitats including C3 grasslands, wooded C3 grasslands, and riparian forests. / A Thesis submitted to the Department of Earth, Ocean, and Atmospheric Science in partial fulfillment of the requirements for the degree of Master of Science. / Summer Semester 2015. / July 14, 2015. / C3/C4, enamel, Miocene, Mojave Desert, Paleodiet / Includes bibliographical references. / Yang Wang, Professor Directing Thesis; A. Leroy Odom, Committee Member; William C. Parker, Committee Member.

The record of the changing composition of planktonic foraminifer assemblages constitutes a record of changes in the hydrography of the upper water column. A priori knowledge of the ecology and paleoecology of prominent taxa is used to interpret past changes in the hydrography of the upper water column, particularly the position of the seasonal thermocline. In this study planktonic foraminifers have been counted at five sites in the equatorial Pacific (ODP Site 806, 807, 847 and 852) and Atlantic (ODP Site 925). The initial sampling interval at all sites is $\sim$9.5 m ($\sim$250 kyr) through approximately the last 6 m.y. In the first paper the results of low-resolution faunal counts of four sites are presented in the depth domain. In the upper Miocene both eastern and western samples contained 60% thermocline dwellers and 40% mixed-layer dwellers. At the western sites the mixed-layer dwellers increase until they constitute 80% of the assemblage in the Pleistocene. At ODP Site 847 thermocline dwellers increase in the Pleistocene to comprise $>$80% of the assemblage. In the second paper data from ODP Sites 806 and 847 was placed in the time domain and higher-resolution sampling ($\sim$20 cm = $\sim$10 kyr) was carried out through two intervals (4.35-4.10 Ma and 3.15-2.90 Ma). The disappearance of thermocline-dwelling Neogene globoturborotalitids at ODP Site 806 coincides with the reduction of late Miocene Antarctic ice volume and southeast tradewind strength, the end of the biogenic bloom in the Pacific and the beginning of the closing of the Central American Seaway. The expansion of thermocline dweller Neogloboquadrina dutertrei at ODP Site 847 follows the onset of large-scale Northern Hemisphere glaciaton. The third paper explores the relationship between isotopic data for three species (Globigerinoides sacculifer, Neogloboquadrina dutertrei and Globorotalia crassaformis) and faunal count data. Assemblage composition at ODP Site 925 is principally affected by the intensity of downwelling associated with the ITCZ, which moves steadily equatorward from the early Pliocene to the early Pleistocene due to the cooling of the Northern relative to the Southern Hemisphere.

Microwear analysis has been severely underutilized as a dietary technique due to numerous constraints involved in employing traditional scanning electron microscopy. A new methodology is described that greatly simplifies the assessment of microwear scar features for the discernment of the trophic adaptations of living and fossil taxa. A standard stereomicroscope and a fiber-optic light source have replaced specimen preparation tools such as venting and plating apparatus and the high-tech scanning electron microscope. Several new microwear variables supplement traditional quantification of pits and scratches. Significant niche partitioning in extant browsers, grazers, and mixed feeders is apparent and habitat differences within each broad trophic group are discernible by scoring relative pit sizes, scratch textures, and gouges in addition to quantifying scratches and pits. Variations in scratch number ranges, scratch textures, and relative pit sizes are the most useful variables for partitioning living ungulates into more refined trophic categories. Pit numbers and scratch textures are most effective for distinguishing fine versus coarse browsing, as well as leaf browsing versus fruit browsing. Scratch textural differences and scratch numbers distinguish fresh grass grazing versus coarse or mixed grass grazing; C3 versus C4 grazing, coarse bark and stem feeding, and seasonal or regional mixed feeding versus a meal-by-meal alternation between browse and grass. Heavy gouging is used to distinguish significant grit encroachment upon food items. Seasonal or regional mixed feeders have microwear that is more similar to browsers, whereas meal-by-meal mixed feeders have wear more similar to grazers. Three trophic phases are identified within extant ungulates by partitioning taxa into three potential raw scratch ranges: traditional browsing and grazing phases, comprised by surprisingly few species, and a browsing-to-grazing transitional phase where the majority of taxa are found, including all of the mixed feeders. The new microwear methodology is used to test two hypotheses regarding large shifts in dietary strategies in fossil ungulates from the North American Great Plains region: the supposed browsing-grazing transition in the fossil record of North American equids and the supposed shift to coarser browse in the fossil ruminant artiodactyl family known as the Dromomerycidae.

Pollen analysis of organic sediments from vleis in upland areas of the Central and marginal Karoo has provided a vegetation history spanning the late Quaternary in the Winterberg, Sneeuberg, Nuweveldberg and Cederberg Mountains. Fossil pollen studies indicate moist conditions at the beginning of the Holocene, followed by a drier period. The second half of the Holocene (4 600 BP) is characterised by moister conditions, becoming drier towards the present and resulting in a decline in grasslands and an increase in Karoo-bushes. In the western Cape, the late Pleistocene (15 000 to 10 000 BP) was characterised by conditions moister than the present. This was followed by a drier period which ameliorated in the late Holocene. Although climatic fluctuations occurred, fynbos has been maintained in situ throughout the sedimentation period (14 600 BP), highlighting the dominant role of the substrate and secondary importance of climate. Climatic changes caused a shuffling of plant communities within the Fynbos Biome - this long uninterrupted history may be one reason for the high species diversity of fynbos. San hunter-gatherers, who occupied southern Africa prior to 4 000 BP, had a negligible impact on the vegetation. Khoi herders, who were first documented in the fossil record about 1 800 BP, had a slight impact on the vegetation, particularly by altering the fire regime. However, the arrival of European Trekboers some four hundred years ago had a significant effect on the environment. Although the general climatic trend in the Karoo is one of a drier phase, the decline in grasses and eastward movement of xeric Karroid elements has been accelerated due to mismanagement and sedentary farming techniques. An extensive contemporary pollen rain study has been undertaken to examine the representivity of these fossil pollen data. The investigation shows that contemporary pollen rain is a good reflection of the vegetation communities in the Karoo and Cederberg. Multiple discriminant analysis compares fossil pollen assemblages with contemporary pollen spectra and proved useful for determining whether modern analogues exist for the fossil pollen assemblages. TWISA confirmed the zones derived from discriminant analysis. Environmental changes have occurred in the Karoo during the late Quaternary, resulting in fluctuations and changes in vegetation patterns which have been accelerated in the recent past by human activity. Bibliography: pages 293-318.

To better constrain the timing of panda's dietary shift from omnivorous to bamboo-exclusive herbivores, this study analyzed stable isotopes of carbon and oxygen in tooth enamel samples from two pygmy pandas from Yanliang Cave (early Pleistocene), three baconi pandas from Gongjishan Cave (late middle Pleistocene to early late Pleistocene), and five giant pandas from Baxian Cave (late Pleistocene) in the Chongzuo Ecological Park of Guangxi Province in South China. In addition, the carbon and oxygen isotope compositions of enamel samples from other mammals associated with the pygmy panda at Yanliang Cave were also analyzed. The results show that the pygmy panda, Ailuropod microta, had the lowest enamel-δ13C values compared to other coexisting mammals at -19‰, suggesting that the pygmy panda had a pure C3 diet composed of plants growing in the understory of a closed-canopy forest. A pure C3 diet for the pygmy panda, if confirmed by more data, would be consistent with an already established dietary niche of bamboo (a C3 plant). Reconstructed δ13C values of diets for the Yanliang fauna range from -25.6 to -32.1‰, indicating that these early Pleistocene mammals ate predominantly C3 vegetation and lived in an environment dominated by C3 plants. This suggests that the area was comprised of wooded habitats ranging from closed canopy forests to woodlands. Significant intra-tooth δ13C variations observed in some grazing animals suggest that a small amount of C4 grasses may be present in patches of open areas in a predominantly forested landscape. The reconstructed δ18O values of meteoric water in the area during the early Pleistocene fall within the range of -7.6 to -7.8‰; lower than the present-day mean annual precipitation δ18O values in the region, suggesting a wetter climate or stronger monsoon season in the early Pleistocene than today. The baconi panda (Ailuropod baconi) and giant panda (Ailuropod melanoleuca), had less depleted δ13C values with an average of -16.7‰ and -17.2‰, respectively, compared to the early Pleistocene panda. Assuming they also consumed bamboo exclusively, this would suggest an ecologic shift to a more open woodland environment towards the end of the Pleistocene. / A Thesis submitted to the Department of Earth, Ocean, and Atmospheric Science in partial fulfillment of the requirements for the degree of Master of Science. / Spring Semester 2016. / April 6, 2016. / paleoclimate, paleodiet, panda, stable isotopes / Includes bibliographical references. / Yang Wang, Professor Directing Thesis; A. Leroy Odom, Committee Member; William C. Parker, Committee Member.

This dissertation presents biostratigraphic, taxonomic and paleoceanographic studies of sediment cores from low-latitude Ocean Drilling Program (ODP) Legs 154 (Site 929), 115 (Site 709), and 202 (Site 1237). Three major paleoceanographic events are featured: 1) the Oi-glacial events in the early-late Oligocene, 2) the Late Oligocene Warming Event (LOWE), and 3) the Oligocene/Miocene Boundary and Mi-1 glacial event. In Chapter Two, a new modified calcareous nannofossil zonation is proposed for the low latitudes that is composed of five major zones and three subzones between 24-30 Ma in age. The first occurrences of Sphenolithus avis, S. ciperoensis, Crassidiscus backmanii along with an increase in abundance of S. ciperoensis, and the last occurrences of S. predistentus, Crassidiscus backmanii and S. ciperoensis are synchronous and reliable throughout the tropics. The last occurrences of Sphenolithus distentus and S. avis are considered unreliable events due to a possible reworking of the former taxon and a diachronous occurrence of the latter. The last occurrences of Helicosphaera compacta and S. pseudoradians are only found in two out of three basins and thus are used as secondary events. The spatial and temporal distributions of calcareous nannofossil assemblages show major variations within the three tropical/subtropical sites. Sphenolithus taxa were found in low abundances in the Atlantic Ocean. Weak tolerance to low salinity is proposed since salinity declined in the Atlantic Ocean during the late Oligocene glacial events due to episodes of freshwater and terrigenous discharge from the Amazon River. This also lowered the δ18O values of seawater at Site 929 compared with the other sites. Furthermore, Site 929 was not far from its present-day position near the mouth of the Amazon River, thus, the low salinity levels best explains the observed major decline in Sphenolithus taxa. Calcareous nannofossil relative abundances (%) and bulk oxygen and carbon stable isotope data reveal a covariant response to glacial (Oi) events. During glacial events, temperate-, cool-water and eutrophic taxa dominated the tropical assemblage, whereas warm and oligotrophic taxa declined. This increase in temperate and cool-water taxa suggest that the tropical surface oceans witnessed a decrease in temperature that allowed cool-, and temperate-water taxa to extend their geographic range into the tropical zone. The Oligocene global glacial events (Oi-2*, Oi-2a, Oi-2b, and Oi-2c) were associated with accelerated upwelling in which eutrophic conditions prevailed and r-mode taxa dominated the total nannofossil abundance. Both Sphenolithus predistentus and Helicosphaera species show prominent increases during glacial (Oi) events. Unlike other Sphenolithus taxa that favored high salinity, S. predistentus increased in abundance during glacial events characterized by high δ18O and δ13C values. Similarly, Helicosphaera taxa show the same pattern with sporadic occurrences. This suggests that S. predistentus and Helicosphaera species were adapted to increased levels of nutrient (eutrophic or mesotrophic). Between 24-25 Ma, warm and oligotrophic taxa increased drastically and dominated the overall assemblage. However, bulk sediment δ18O and δ13C values at the three sites do not show a consistent decreasing trend similar to the global composite deep-sea isotopic record. Although the paleoecological group suggests oligotrophic conditions associated with dominate warm water, the paleotemperature of the sea surface during the LOWE was not as warm as during the Eocene hyperthermals. In Chapter Three, a new and significant late Oligocene Sphenolithus species is described from the tropical ODP materials. The new species, Sphenolithus avis, has a prominent short range spanning upper Zone NP23 to upper Zone NP25 with an age from ~29.9 Ma to 24.8 Ma. Sphenolithus avis is widely distributed and it differs from S. ciperoensis by more flaring proximal shields. In Chapter Four, high-resolution Oligocene/Miocene calcareous nannofossil biostratigraphy has revealed thirteen events, five of which are reliable and synchronous due to their similar ages in the Indian and Pacific Oceans. The synchronous events are: the last occurrences (LOs) of C. fenestratus and S. delphix, and first occurrence (FO) of S. disbelemnos and the beginning and ending of the S. conicus acme. The Sphenolithus conicus acme is documented in the Indian Ocean between 23.5 Ma and 22.8 Ma. This acme was first found in the Pacific Ocean across the Mi-1 glacial event which is characterized by high δ18O and δ13C values. This study supports a correlation of the S. conicus acme in the Indian Ocean with that of relatively similar age in the Pacific Ocean. / A Dissertation submitted to the Department of Earth, Ocean, and Atmospheric Sciences in partial fulfillment of the requirements for the degree of Doctor of Philosophy. / Spring Semester 2016. / April 15, 2016. / Biostratigraphy, Calcareous Nannofossils, Glacial events, Oligocene, Paleoecology, Taxonomy / Includes bibliographical references. / Sherwood W. Wise, Jr., Professor Directing Dissertation; Laura R. Keller, University Representative; William C. Parker, Committee Member; Yang Wang, Committee Member.

The Late Miocene brought a sudden increase in the biomass of C4 plants that resulted in an expansion of grassland habitat and markedly changed the diets of vertebrate fauna in many places around the world. Concurrently, early pulses of Great American Biotic Interchange (GABI) migrations are evidenced by early first appearances of immigrant taxa in the fossil record, leading into the major GABI pulses in the Early Pliocene. The causes and environmental context of GABI migrations, however, are not well understood. Vertebrate fossils from Yepómera, western Chihuahua, represent one of the richest assemblages in Mexico and are a valuable paleo-environmental archive. This study examined the stable isotope compositions of tooth enamel samples of this fauna to provide broad insight into the environmental conditions of this region between 4.89 to 5.23 Ma, just after the arrival of C4 plants in North and South America and before the first major migration of GABI. The enamel carbon and oxygen isotope data suggest a relatively dry, open habitat (similar to savanna or prairie environments) with a strong C4 vegetation component, a mean annual temperature of 18 ± 10°C and a moderate annual precipitation of 657 ± 93 mm/yr. At Yepómera, there was distinct niche partitioning into pure C3 diets, mixed diets, and pure C4 diets. As such, C4 vegetation must have been a major component of the environment during the Late Miocene-Early Pliocene. Despite expectations, no niche partitioning between equid species (Dinohippus mexicanus, Nannippus aztecus, Astrohippus stockii, and Neohipparion eurystyle) can be determined from carbon isotope ratios. All four fossil horse species found in Yepómera had pure or nearly pure C4 diets, suggesting that they were hyper grazers or primarily grazers, consistent with the inference from their dental morphology. Pure C3 consumption was rare to absent in all other genera analyzed except for the genus Camelops, for which C3 vegetation was the dominant diet. Samples from Hemiauchenia varied between pure C3 diet and a mixed diet depending on the individual. The other genera in this study site (Gomphotheriidae, Hexobelomeryx fricki, and Platygonus) were primarily mixed feeders. Assuming a carnivorous life habit (based on dentition), Agriotherium schneideri, an immigrant large ursid, appears to have consumed primarily equids or an unsampled taxon with predominantly C4 diet. However, the enamel isotope data cannot exclude the possibility of an omnivorous life habit. Migrations are evidenced in the oxygen isotope ratios of several specimens indicating that there was mobility in these taxa before the GABI, with diets remaining consistent throughout this migration (suggesting strong dietary preferences and niche specialization). The carbon and oxygen isotope ratios of the Yepómera fauna are consistent with both the holding pen hypothesis for the GABI and a Central American rise in C4 biomass at least close in time to the expansion of C4 biomass in North America. Through adaptation to this ecosystem, these taxa would be well prepared to exploit and compete for the grassland habitats proposed to have developed on the Panama Isthmus. This could explain how equids, peccaries, gomphotheres, and short-faced bears related to these taxa had such success in arriving and diversifying in the South American mainland, where a similar habitat is believed to have expanded around the time of the exchange. Future work in this area will lead to a more complete understanding of biologic responses to changing climate and population dynamics. / A Thesis submitted to the Department of Earth, Ocean, and Atmospheric Science in partial fulfillment of the requirements for the degree of Master of Science. / 2019 / November 14, 2019. / Diet, Enamel, GABI, Mexico / Includes bibliographical references. / Yang Wang, Professor Directing Thesis; William C. Parker, Committee Member; Jeremy Owens, Committee Member; Gregory M. Erickson, Committee Member.

No description available.

No description available.