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The middle Claiborne Kosciusko Formation is one of the primary water supplies for much of central and northwestern Mississippi. The formation consists of fluvial and deltaic sand, clay, and lignite, all of which comprises of a complex depositional system. In west-central Mississippi, the Kosciusko Formation contains upper and lower aquifer sands. These sand bodies rank fourth among the eleven most valuable water-bearing units in the state. The formation varies in thickness from approximately 1,000 feet (305 meters) near the Mississippi River in western Claiborne County to approximately 250 feet (76 meters) in Clarke County before grading to shale southward. This depositional systems analysis maps the net sands within the Kosciusko Formation using high-quality geophysical logs where possible. Sand body geometries, based on the net sand maps within this these, are compared with those of modern depositional systems to find modern analogues that best characterize the Kosciusko Formation.

A gradual rise in Earth's surface temperature marks a transition from the late Paleocene to the early Eocene ca. 58-51 Ma. Paleocene/Eocene boundary (∼55.5 Ma) sediments deposited in the midst of this slow warming ubiquitously reveal evidence for a massive isotopically light carbon injection and an associated rapid but transient global warming event, or hyperthermal, that has been termed the Paleocene Eocene Thermal Maximum (PETM) and attributed to a carbon injection from multiple potential sources. The PETM has gained importance over the past two decades as a potential geologic analog to the modern anthropogenic carbon injection and climate change. However significant questions surrounding the nature of the carbon injection at the onset of the PETM remain. The Clarence River valley, located in the Marlborough region, South Island, New Zealand, contains a series of outcrops of lithified late Paleocene to early Eocene sediments originally deposited on a paleo-slope margin. Within these sections, the Lower Limestone Member of the Amuri Limestone Formation records the interval of interest. A Lower Limestone prominent recessed unit consisting of multiple marl-rich beds and recording a pronounced negative carbon isotopic excursion (CIE) marks the PETM at sections that have been bisected by tributaries to the Clarence River, including Mead Stream and Dee Stream. Here I detail and discuss Clarence valley Lower Limestone sections and relate these records to global trends with an emphasis on adding constraints to the PETM carbon injection. Specifically, I document the lithologic and carbon isotopic expression of the PETM and two younger paired sets of early Eocene events that, similar to the Mead Stream and Dee Stream PETM sections, reveal negative CIEs and expanded marl-rich units coincident to identical CIEs and condensed carbonate dissolution horizons in deep-sea sections. I further quantify the abundance of bioturbating macrofauna trace fossils through the PETM at both Mead Stream and Dee Stream and argue that New Zealand margin intermediate waters became hypoxic precisely coincident to the PETM carbon injection. In concert, these findings suggest a PETM carbon addition mechanism capable of both diminishing intermediate water dissolved oxygen and of repeated early Eocene injections. / U.S. National Science Foundation (NSF); Joint Oceanographic Institutions (JOI), Inc.

Proxy-based quantitative estimates of Eocene climates can be made from marine isotope records for ocean conditions or fossil plants for terrestrial environment. However, our understanding about Eocene terrestrial climates is derived mainly from North America and Europe, and little is known about East Asia. Previous qualitative paleoclimate studies briefly revealed three climatic regimes across China during the Eocene with a planetary wind-dominated subtropical to tropical arid zone in the central part (i.e., the subtropical highs), which was flanked by the subtropical climate zone in the north and tropical climate zone in the south. But such a pattern of paleoclimatic zonation still requires a test from quantitative study. Based on analyses of 66 plant assemblages, carefully selected from 37 fossil sites throughout China, we here report the first large-scale quantitative climatic results and discuss the Eocene climatic patterns in China. Our results demonstrate that the Eocene monsoonal climate must have been more or less developed over China, judging from the presence of apparent seasonality of both temperature and precipitation revealed by our quantitative estimation. This appears not to support the previously claimed Eocene planetary wind-dominated climate system, at least in the region of eastern China. In addition, the research indicates that, with a slight declining trend of MAT during the Eocene, the winter temperature substantially dropped in tropical southern China during the middle to late Eocene interval. This might be related to the development of a weak Eocene Kuroshio Current in the southwestern Pacific, and/or a significantly enhanced paleo-winter monsoon from Siberia.

Erosion beveled the Laramide Front Range uplift in Colorado to a surface of low relief by the end of the Eocene. This study uses paleobotanic climate analysis techniques to determine the paleoelevation of this regional surface by examining the overlying 34.9 Ma Florissant flora. Multiple regression models explaining 93.4% of the variance in mean annual temperature (MAT), 86.1% of the variance in growing season precipitation (GSP) and 65.7% of the variance in rainfall distribution were derived from J. A. Wolfe's dataset of 31 leaf physiognomic character states from 86 modern vegetation sites. When applied to a new collection of 29 species from the Florissant flora, estimates of MAT = 10.7 ± 1.5°C, and GSP = 55.6 ± 12.5 cm, with precipitation occurring mostly during the growing season, are derived. This paleoclimate estimate is corroborated by data from late Eocene Sequoia affinis from Florissant. Higher mean ring width of the fossil trees as compared to modern counterparts can be explained by a climate with summer mean monthly temperatures ≥ 14°C and summer mean monthly rainfall >1.5 cm. The estimated MAT, when combined with coeval sea level MAT and terrestrial lapse rate, implies an elevation of 2.3-3.3 km for Florissant, which is indistinguishable from the modern elevation of 2.5 km. The elevation of Florissant is tied to that of the Great Plains by the Wall Mountain Tuff, so the Great Plains were also high. The elevation was created either by underplating and/or mass transfer in the Laramide, or by mantle uplift of crust thickened by pre-Laramide tectonics. This elevation estimate implies that: (1) Pliocene uplift is not required to explain the present elevation. Thus, late Tertiary plateau uplift in the western US was not a contributing factor to the marked global cooling since 15 Ma; and (2) in the late Eocene, regional surfaces of planation could be formed at elevations significantly above sea level but below tree line. The surface was possibly formed from a lack of storminess; a preponderance of small storm events will diffusively smooth topography.

Through isotopic analysis of Viviparus lentus (V. lentus) a high resolution record of stepwise changes in δ18O and δ13C across the Eocene / Oligocene transition and Oi-1 glacial maximum has been produced for the continental Solent Group strata, Isle of Wight (UK). Comparison of this V. lentus δ18Ocarb. record with high resolution marine δ18Ocarb. records shows that similar isotopic shifts exist in the near coastal continental and marine realms. In order to calculate palaeotemperatures from this new continental record an investigation into the biology of modern Viviparus and its effect on the isotopic composition of its shell carbonate was undertaken. Experimental measurements of the 18O/16O isotope fractionation between the biogenic aragonite of Viviparus and its host freshwater were undertaken on samples derived from the Somerset Levels in order to generate a genus specific thermometry equation. The results from using this new Viviparus equation on fossil V. lentus shell fragments suggests that aquatic and terrestrial biota were being affected by climate change associated with the Late Eocene Event. This conicides with a decrease in mammal species richness in the Osborne Member, reaching its climax at the end of the Osborne / Seagrove Bay Members. This event is followed by a brief warming in the Bembridge Limestone which was marked by a within-Europe mammal turnover involving dispersal from the south and an increase in species richness, concurrent with this is an increase in size of Harrisichara gyrogonites. An additional investigation into seasonal isotopic variability using whole well preserved V. lentus specimens has also revealed a shift from tropical /subtropical to temperate climatic zones occurring before the Eocene /Oligocene boundary and Oi-1 glacial maximum. Overall the evidence provided by these investigations would suggest that climatic change was already in progress prior to the build up of glacial ice on Antarctica.

The clade Kinosternoidea consists of the extant mud and musk turtles (Kinosternidae) and the Central American river turtle Dermatemys mawii. Baptemys, an Eocene turtle taxon from North America, has historically been allied to D. mawii within Dermatemydidae, but this relationship has never been rigorously tested in a global analysis. Molecular data and multiple morphological characters support monophyly of Kinosternoidea, but kinosternids and D. mawii are vastly different in their morphology, and the relationships of Dermatemys are controversial. Dermatemys mawii is highly adapted to consuming aquatic vegetation and is thus much more similar in gestalt to some emydids than to kinosternids. Dermatemys mawii was historically placed among tortoises (Testudinoidea) by a number of traits pertaining to their fully ossified shell and the development of a secondary palate. Different placements of D. mawii indicate radically different historical biogeographic scenarios and sequences of character evolution. Few relevant morphological characters have been used in global analyses of turtle relationships, and several fossil taxa are known that could prove critical to resolving this debate. Baptemys wyomingensis is the best-sampled fossil dermatemydid. A detailed description of B. wyomingensis, along with a consideration of its phylogenetic relationships, indicates additional morphological support for a close relationship with Dermatemys and a placement for D. mawii and Baptemys within Kinosternoidea, as well as an unexpected close relationship with Hoplochelys and Agomphus to the exclusion of the Kinosternids. A review of the alpha taxonomy of Baptemys reveals that the relationships between the species, other than B. wyomingensis and B. garmanii remain unclear due to a lack of published descriptions and it appears likely that Baptemys may be paraphyletic in regard to D. mawii.

Borealosuchus Brochu 1997 was erected for a group of Late Cretaceous through early Eocene eusuchian crocodyliform species formerly assigned to Leidyosuchus Lambe 1907. Borealosuchus wilsoni was originally described by Mook (1959) based solely on a dorsoventrally crushed skull from the early Eocene (Wasatchian) Green River Formation of Wyoming, and assigned to Leidyosuchus. Later analyses referred specimens from the late Paleocene and middle Miocene to the species (Brochu, 1997). In phylogenetic analyses, Borealosuchus has been retrieved as either a basal crocodylian (e.g., Salisbury and Willis, 1996; Brochu, 1997; Wu et al., 2001; Buscalioni et al., 2011; Brochu et al., 2012; Narváez et al., 2016) or a close crocodylian outgroup (e.g. Benton and Clark, 1988; Pol et al., 2009; Turner and Pritchard, 2015). More exact phylogenetic placement of Borealosuchus remains unclear. Borealosuchus wilsoni is stratigraphically the youngest species of Borealosuchus, and one of the most completely known, and as such, it figures prominently in ongoing debates over the phylogenetic relationships and origin of crown group Crocodylia. Given its long stratigraphic range in the literature, the question of whether specimens currently referred to B. wilsoni all pertain to a single species is open. This study focuses on a more thorough description of the skeletal morphology of Eocene Borealosuchus, and a revision of the taxonomy of this assemblage, including the conspecific nature of Wasatchian Borealosuchus wilsoni and middle Eocene (Bridgerian) fossils referred to Borealosuchus wilsoni, including material of Diplocynodon stuckeri Mook 1960. A phylogenetic re-assessment of B. wilsoni will hopefully provide further resolution within Borealosuchus and among other closely related taxa. Specimens were coded with a matrix of 190 morphological characters and subjected to phylogenetic analysis. The diversity of Borealosuchus during the Eocene has been underestimated and specimens from the Bridgerian are diagnosable and distinct from those of the preceding Wasatchian stage. A new species will be erected to contain this material. The erection of a new species of Eocene Borealosuchus renders the holotype of D. stuckeri non-diagnostic at the species level, and a new holotype USNM 12990 is designated for Bridgerian Borealosuchus. Some specimens assigned to Brachyuranochampsa eversolei and Crocodylus affinis may also be referable to Borealosuchus. The addition of new material to Borealosuchus increases the diversity of this group during the Eocene.