Conserving biodiversity in the current global ecological crisis requires a robust understanding of a multitude of abiotic and biotic processes operating at spatial and temporal scales that are nearly impossible to study on a human timescale and are therefore poorly understood. However, fossil data preserve a vast archive of information on past ecosystems and how they have changed through time. My PhD research is composed of three studies that look at biogeogaphic distribution, ecosystem structure, and trends in richness and diversity. Identifying organisms to the species level is a common practice in ecology when conducting community analyses. However, when species-level identification is not feasible, higher level taxonomic identifications are used as surrogates. This study tests the validity of supraspecific identifications for vertebrates in regional biogeography studies, using the recorded occurrences of terrestrial and aquatic taxa from 16 national parks on the Colorado Plateau and culling the data set based on a series of taphonomic processes to generated fossil assemblages. Changes in community structure as a result of increased magnitude and/or frequency of perturbations have been well documented in terrestrial and marine ecosystems. Unfortunately, the long-term effects of sea-level rise on vertebrate communities in coastal habitats are poorly understood and difficult to study on a human time scale. This study examines the long term effects of relative sea-level change on coastal plain ecosystems of the Belly River Group (Campanian) in southern Alberta using microvertebrate fossils. Most Cretaceous freshwater deposits in North America produce only a couple of articulated fish skeletons. Because of this preservational bias many workers suggested that freshwater teleosts were largely absent from North America until the Eocene or later. Late Cretaceous fish assemblages are of particular interest, because these assemblages undergo a major compositional change. Pre-Cretaceous fish assemblages are dominated by non-teleosts, while Paleogene assemblages are dominated by teleosts that are members of extant families. This study provides a first approach in characterizing long-term trends in richness and the distribution of Late Cretaceous, nonmarine actinopterygians of the Western Interior of North America.

No description available.

No description available.

The Upper Albian (mid-Cretaceous) sediments of the Anglo-Paris Basin display a range of condensation phenomena, including glauconitic and phosphoritic sands, glauconitic intraformational pebble beds, and mineralised nodular hardgrounds. These are interpreted as the result of sedimentation rate fluctuations controlled by small-scale relative sea-level changes of at least regional nature. The regional signal was modified by local tectonics, including occasional synsedimentary faulting and the development of thinned successions and complex condensation horizons over broad submarine highs. Candidate sequence boundaries, marine flooding surfaces and systems tracts are proposed. Episodic, high-energy storm events record a spectrum of storm intensities and periodicities in the Upper Greensand Formation. Storm processes interacted with early submarine lithification to produce a suite of pebble-shell beds, simple and amalgamated coquinas, and storm-scoured hardgrounds. Analysis of shell bed fabrics and taphonomy indicates the important role of high-energy storms in generating a distinct event stratigraphy. Stable isotope analysis has detected a positive secular change in carbon-isotopic ratios within carbonates of dispar zone age, resolved as two smaller positive shifts across nodular hardgrounds. This correlates with the development of organic-rich sediments in a range of settings world-wide. Analytical problems, including silica diagenesis, have been addressed by a series of parallel control studies. Geochemical and petrographic analysis has confirmed the widespread development of glauconitic minerals throughout the Upper Greensand, and has been used to investigate grain evolution in a range of lithologies. A review of the global development of the Cretaceous glauconitic facies has been used to compile depositional models for a range of settings. Volumetric calculations of Cretaceous glauconite production rates have shown secular changes, with peak Aptian to Santonian values linked to transgressions across the broad shelf seas which developed globally during this time of rising sea-levels and sea-level highstand.

The phosphatic chalks of the Anglo-Paris Basin are granular phosphorites of Santonian to early Campanian age. They were deposited in erosional cuvettes up to 1 km long, 250 m wide and 30 m deep, incised into white chalks. Most are situated in the Picardy region of northern France. Cuvettes are floored by strongly indurated and mineralized basal hardgrounds developed in intraclastic sediments. The hardgrounds are penetrated by prominent phosphatic-chalk filled Thalassinoides burrows and overlain by intraclast-pebble lags containing 'Terebella' phosphatica Leriche, Diblasus arborescens Parent and Lopha semiplana (J. Sowerby). Lithification occurred a few centimetres below the sediment/water interface in a sediment of increased permeability, and is geochemically discernible ~90 cm below the hardground surface. Glauconitization was restricted to replacement of clay minerals during the early development of the hardground, later phosphatization replacing carbonate. Actinocamax verus Miller occurs in basal phosphatic chalks and a bed of Gonioteuthis quadrata quadrata (Blainville) occurs at the summit. The Gonioteuthis Bed is commonly underlain by, but separated from, a bed of Offaster pilula (Lamarck). The proportion of faecal pellets, phosphatic ooliths, echinoderm fragments and benthonic foraminiferans decline above the basal hardgrounds as the phosphorites become finer-grained and less phosphatic. Inoceramid prisms or pelagic foraminiferans are the dominant component of poorer phosphatic chalks. Intraformational slump folds and hardground mélanges occur at the base of some successions. The palaeobiology of belemnites is considered in detail and it is concluded that the Gonioteuthis Beds were the products of massmortalities accompanying reproduction. Pelletal phosphate was formed by the replacement of carbonate during early diagenesis in an organic-rich, anoxic environment and water depths of <150 m. Current activity and subsurface anoxia were intermittent; colonization, bioturbation and winnowing alternating with quiescent, anoxic phases of mineralization. Phosphatic chalk cuvettes were eroded by a proto-Gulf Stream during a eustatic regression. Upwelling of this current was the main source of phosphate in the phosphatic chalks.

Thesis (Ph.D.)--University of Rhode Island, 2007. / Includes bibliographical references (leaves 233-245).

Global warming in response to increasing levels of atmospheric CO2 concentration (pCO2) has generated concern over the effects of increasing surface temperature on the hydrologic cycle. Investigating precipitation dynamics during past ‘greenhouse’ intervals provide important insights necessary to better constrain potential future climate scenarios. The Late Cretaceous greenhouse is characterized by elevated pCO2 and surface temperatures, with a prolonged cooling trend which initiated in the late Campanian and an associated 4th-order sea-level regression recorded in the Western Interior Seaway (WIS), providing an opportunity to examine the hydrologic cycle under conditions of changing temperature and sea-level. This study uses a sclerochronologic approach to examine δ18O and δ13C values in freshwater bivalves collected from two horizons separated by ~800 ka, to reconstruct the late Maastrichtian hydrology at a locality along the western shoreline of the WIS. To ensure the presence of primary calcium carbonate, valves were examined using Scanning Electron Microscopy (SEM). Bivalve δ18O and δ13C values reflecting coastal river compositions range from -10.5 to -2.8‰ and -8.2 to 5.6‰, respectively. A positive correlation between δ18O and δ13C values found in specimens lower in the section, reveals that the lowest δ18O values occurred during times of peak summer soil respiration, whereas the highest δ13C values of 5.6‰ record a marine influence, supporting rainout during a summer monsoon as the cause for the lowest δ18O values recorded in this group. The valves collected higher in the section have an alternating correlation between δ18O and δ13C and plot closer to high elevation precipitation values on a mixing diagram. The loss of the summer monsoon between the two unionid groups is likely in response to decreasing surface temperatures and the retreat of the seaway, providing insight into the potential for increased intensity of modern monsoons in response to increasing surface temperatures and sea-level rise.

The extinct oyster Exogyra (Ostreoida: Gryphaeidae) thrived during the Cretaceous Period. The Genus was especially abundant in the southern parts of the United States, as these areas were once covered under a shallow sea. Left (lower) valves of the species Exogyra costata (Say, 1820), show different variations of the shells including differences in size and scarring of the scar remaining from the point of substrate attachment. The scars are often created by attaching to another organism, leaving an impression of it via a process called bioimmuration. This research analyses specimens from three sites within two different geological formations (Owl Creek Formation, Prairie Bluff Formation). Statistical analysis of attachment frequencies of collected specimens, as well as the analysis of the overall substrate availability reveals certain patterns of attachment, in addition to variations in lithologies of the study areas.

No description available.

The taphonomy and paleoecology of a well-preserved mosasaur (DSM 10716) are reported from Oktibbeha County, Mississippi. The mosasaur was recovered from the Prairie Bluff Chalk, the exact stratigraphic position and age confirmed using established foraminiferal zonation for the Late Cretaceous of the U. S. Gulf Coastal Plain. A species identification of Mosasaurus cf. hoffmanni Mantell is given using shape and structure of the quadrate and jugal, as well as tooth counts for the dentary, maxilla, and pterygoid. DSM 10716 exhibits well-preserved trace fossils including feeding traces and the remains of encrusting bivalves. The associated fossils are probed for similar phenomena to modern whale falls and other ancient carcass falls. Based on associated fossils present on DSM 10716, evidence for a mobile scavenger stage, a possible enrichment opportunist stage, and a reef stage is established. No chemosynthetic organisms were detected to suggest the existence of a sulfophilic stage.