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Introduction Malalignment and resulting complications are major challenges in total knee arthroplasty (TKA) which patient-specific instrumentation (PSI) is proposed to alleviate. Previous PSI meta-analyses of TKA outcomes typically do not differentiate between PSI systems and assess relatively few outcomes, so the value of their findings is limited. VISIONAIRE™ cutting guides (Smith + Nephew Inc., Memphis, TN, USA) is a PSI system based on preoperative magnetic resonance and X-ray imaging. A systematic literature review (SLR) and meta-analysis, focussed specifically on VISIONAIRE, were conducted to assess TKA accuracy, intraoperative outcomes, and postoperative outcomes, compared with conventional instrumentation (CI). Materials and methods The SLR was performed using PubMed, Embase, and Google Scholar databases to identify relevant studies published until March 2022. Depending on statistical heterogeneity, meta-analyses were performed for outcome measures with fixed effect (I2 I2 ≥ 50%). Dichotomous outcomes were reported as odds ratios and continuous outcomes were reported as mean differences. Descriptive analyses were performed for outcomes not amenable to meta-analysis. Results Outcomes for VISIONAIRE versus CI were reported in 25 studies. Compared with CI, VISIONAIRE reduced odds of mechanical outliers by 40% (p p = 0.02), 42% (p = 0.022), and 15.9% (p = 0.01), respectively), lowering the odds of blood transfusion by 53% (p = 0.01) and shortening patients’ hospital stays (11.1% reduction; p Conclusion Options for PSI in TKA differ substantially, and it is important to assess the outcomes of individual systems. The current findings suggest that VISIONAIRE guides can lead to improved alignment accuracy and surgical efficiency compared with CI, without compromising postoperative safety and return-to-function outcomes.

The Miocene to Pliocene (Neogene) occurred between 23.04 and 2.58 million years ago and includes intervals of peak global warmth where Earth’s average surface temperature was up to 8℃ warmer than present. Major cooling steps also occurred, across which Antarctica’s ice sheets advanced to the continental shelf for the first time and sea ice expanded across the Southern Ocean. Knowledge of Antarctic environmental change and ice sheet variability through this dynamic period in Earth history has advanced over the past 15 years. Major field and ship-based efforts to obtain new geological information have been completed and significant advances in numerical modelling approaches have occurred. Integration of ice proximal data and coupled climate-ice sheet model outputs with high-resolution reconstructions of ice volume and temperature variability from deep sea δ18O records now offer detailed insight into thresholds and tipping points in Earth’s climate system. Here we review paleoenvironmental data through key episodes in the evolution of Neogene climate to include the Miocene Climatic Optimum (MCO), Middle Miocene Climate Transition (MMCT), Tortonian Thermal Maximum (TTM), Late Miocene Cooling (LMC), and Pliocene Warm Period (PWP). This review shows that Antarctica’s climate and ice sheets remained dynamic throughout the Neogene. Given the analogous nature of warm episodes in the Miocene and Pliocene to future projections, the environmental reconstructions presented in this chapter offer a stark warning about the potential future of the AIS if warming continues at its current rate. If average global surface warming above pre-industrial values exceeds 2℃, a threshold will be crossed and AIS instabilities would likely be irreversible on multi-century timescales.

Oscillations in ice sheet extent during early and middle Miocene are intermittently preserved in the sedimentary record from the Antarctic continental shelf, with widespread erosion occurring during major ice sheet advances, and open marine deposition during times of ice sheet retreat. Data from seismic reflection surveys and drill sites from Deep Sea Drilling Project Leg 28 and International Ocean Discovery Program Expedition 374, located across the present-day middle continental shelf of the central Ross Sea (Antarctica), indicate the presence of expanded early to middle Miocene sedimentary sections. These include the Miocene climate optimum (MCO ca. 17–14.6 Ma) and the middle Miocene climate transition (MMCT ca. 14.6–13.9 Ma). Here, we correlate drill core records, wireline logs and reflection seismic data to elucidate the depositional architecture of the continental shelf and reconstruct the evolution and variability of dynamic ice sheets in the Ross Sea during the Miocene. Drill-site data are used to constrain seismic isopach maps that document the evolution of different ice sheets and ice caps which influenced sedimentary processes in the Ross Sea through the early to middle Miocene. In the early Miocene, periods of localized advance of the ice margin are revealed by the formation of thick sediment wedges prograding into the basins. At this time, morainal bank complexes are distinguished along the basin margins suggesting sediment supply derived from marine-terminating glaciers. During the MCO, biosiliceous-bearing sediments are regionally mapped within the depocenters of the major sedimentary basin across the Ross Sea, indicative of widespread open marine deposition with reduced glacimarine influence. At the MMCT, a distinct erosive surface is interpreted as representing large-scale marine-based ice sheet advance over most of the Ross Sea paleo-continental shelf. The regional mapping of the seismic stratigraphic architecture and its correlation to drilling data indicate a regional transition through the Miocene from growth of ice caps and inland ice sheets with marine-terminating margins, to widespread marine-based ice sheets extending across the outer continental shelf in the Ross Sea.

Deep sea geological records indicate that Antarctic ice-sheet growth and decay is strongly influenced by the Earth’s astronomical variations (known as Milankovitch cycles), and that the frequency of the glacial–interglacial cycles changes through time. Here we examine the emergence of a strong obliquity (axial tilt) control on Antarctic ice-sheet evolution during the Miocene by correlating the Antarctic margin geological records from 34 to 5 million years ago with a measure of obliquity sensitivity that compares the variance in deep sea sediment core oxygen-isotope data at obliquity timescales with variance of the calculated obliquity forcing. Our analysis reveals distinct phases of ice-sheet evolution and suggests the sensitivity to obliquity forcing increases when ice-sheet margins extend into marine environments. We propose that this occurs because obliquity-driven changes in the meridional temperature gradient affect the position and strength of the circum-Antarctic easterly flow and enhance (or reduce) ocean heat transport across the Antarctic continental margin. The influence of obliquity-driven changes in ocean dynamics is amplified when marine ice sheets are extensive, and sea ice is limited. Our reconstruction of the Antarctic ice-sheet history suggests that if sea-ice cover decreases in the coming decades, ocean-driven melting at the ice-sheet margin will be amplified. The sensitivity of the Antarctic ice sheet to obliquity increases when ice-sheet margins are exposed to the ocean, suggests an analysis of sediment core oxygen isotope records.

Monte Carlo simulations are performed to predict the interfacial tension (IFT) for water/ n -dodecane, water/toluene, and water/(50 wt% n -dodecane + 50 wt% toluene) mixtures at a pressure of 1.83 MPa and temperatures ranging from 383.15 to 443.15 K. Simulations for the binary mixtures are performed in the N 1 N 2 p N A T ensemble and those for the ternary mixtures are performed in the N 1 μ 2 μ 3 p N A T ensemble. In order to control the composition of the organic phase for ternary mixture simulations, separate reservoirs for toluene and n -dodecane molecules are utilized, and the minimum and maximum numbers of these molecules in the interfacial box are monitored. Identity switch moves are applied to facilitate the sampling of the spatial distributions of the organic molecules. Calculations of the IFT for water/ n -decane and water/benzene mixtures are used to benchmark the force fields and to develop mixing rules. The combination of the TraPPE–UA force field and the TIP4P/2005 water model with Lorentz-Berthelot combining rules yields fairly accurate predictions at moderate temperatures for water/ n -decane, but appears to slightly overestimate the IFT at elevated temperatures. For the water/benzene mixtures, the TraPPE–EH//TIP4P/2005 combination significantly overestimates the IFT over the entire temperature range. Subsequent modifications of the energetic Lennard-Jones cross-interaction parameters yield good agreement between experimental and simulated IFT data of water/ n -decane and water/benzene. Using a preliminary set of modified cross-interaction parameters for the TraPPE–UA/EH//TIP4P/2005 combination, our predictions for the Industrial Fluid Properties Simulation Challenge yield satisfactory agreement with the benchmark data (mean signed errors of − 2.2 , − 5.1 , and − 0.1 dyn/cm for water/ n -dodecane, water/toluene, and water/(50 wt% n -dodecane + 50 wt% toluene), respectively). A new set of modified cross-interaction parameters developed later based on longer simulation trajectories and a larger set of experimental data is found to reduce the mean signed errors to − 0.1 , − 0.6 , and + 2.5 dyn/cm, respectively, for these three systems. Although a significant enrichment of toluene molecules at the interface is found for the ternary mixture, this enrichment is not sufficient to reproduce the experimental IFT data.

Monte Carlo simulations in the Gibbs ensemble were carried out to determine the mutual solubilities for water/n-alkane mixtures over a wide range of temperatures, pressures, and alkane chain length...

Arctic climate in the Late Cretaceous has long been recognized to have been warm and wet relative to the present, but quantitative assessments of paleoclimate have been challenging due, in part, to disagreements between proxies in marine and terrestrial environments. This study provides a first multiproxy evaluation of Late Cretaceous (~93–90 Ma to 73–72 Ma) paleoclimate and paleohydrology from Devon Island in the Canadian High Arctic (modern location: 76°17′N, 91°12′W; Late Cretaceous location: ~71°30′N, ~24°30′W). Surface temperatures are reconstructed at ~12.6 to 20.6 °C for the ocean and 11.7 to 16.9 °C over land, using glycerol dialkyl glycerol tetraether (GDGT) based proxies measured from marine (TEX86) and terrestrial samples (MBT′5ME). These proxies are likely skewed toward warm month temperatures, based on novel analysis and interpretation of biomarkers in sediment and co-occurring marine vertebrate coprolites. The hydrogen isotopic composition (δ2H) of precipitation is constrained to have varied from −123‰ to −82‰ (VSMOW) using evidence from n-alkanes likely derived from higher plants. δ18O of shelfal marine surface water is constrained to have been between −10.5‰ to −3.4‰, using phosphate oxygen isotopes of marine vertebrate teeth and coprolites. From these, marine salinity is modeled to have varied from 10 PSU and 30 PSU, indicative of periodic freshwater influx. These estimates indicate that large marine vertebrates lived and fed, at least intermittently, in near-shore brackish waters. Finally, the Arctic was similarly warm in both the Late Cretaceous and Paleocene/Eocene, but the Late Cretaceous isotopic composition of precipitation at Devon Island was enriched in the heavy isotope of hydrogen by up to +60 to +70‰ relative to Arctic Eocene sites. The combination of techniques used here reduces uncertainties related to the application of proxies to an environment without a modern analogue, providing novel paleoclimatic constraints on the Late Cretaceous Arctic region.

Background To help slow the rising costs associated with total joint arthroplasty (TJA), the Centers for Medicare and Medicaid Services introduced the Bundled Payments for Care Improvement (BPCI) initiative. The purpose of this study is to report our 1-year experience with BPCI in our 2 arthroplasty surgeon private practice. Methods In this series, a historical baseline group is compared with our first year under BPCI. We reviewed the cohorts with respect to hospital length of stay (LOS), readmission rates, discharge disposition, postacute care LOS, and overall savings on a per episode basis. Results The baseline group included 582 episodes from July 2009 to June 2012. The BPCI study group included 332 episodes from July 2015 to September 2016. We witnessed a substantial learning curve over the course of our involvement in the initiative. The total reduction in cost per episode for TJA was 20.0% (P = .10). Hospital LOS decreased from 4.9 to 3.5 days (P = .02). All-cause 90-day readmission rates decreased from 14.5% to 8.2% (P = .0078). Overall, discharges to home increased from 11.6% to 49.8% (P = .005). Conclusion Our small, private, 2 arthroplasty surgeon orthopedic practice has shown improvement in postoperative management for TJA patients in 1 year under the BPCI initiative, with increased discharges to home, decreased skilled nursing admissions, days in skilled nursing, and overall readmissions. Because BPCI includes fracture care arthroplasty, the model could be made more equitable if these patients were reimbursed a rate commensurate with their increased costs and risks.

First-principles molecular dynamics simulations in the canonical ensemble at temperatures of 333 and 363 K and at the corresponding experimental densities are carried out to investigate the behavior of the 1:2 choline chloride/urea (reline) deep eutectic solvent and its equimolar mixture with water. Analysis of atom-atom radial and spatial distribution functions and of the H-bond network reveals the microheterogeneous structure of these complex liquid mixtures. In neat reline, the structure is governed by strong H-bonds of the trans- and cis-H atoms of urea to the chloride ion. In hydrous reline, water competes for the anions, and the H atoms of urea have similar propensities to bond to the chloride ions and the O atoms of urea and water. The vibrational spectra exhibit relatively broad peaks reflecting the heterogeneity of the environment. Although the 100 ps trajectories allow only for a qualitative assessment of transport properties, the simulations indicate that water is more mobile than the other species and its addition also fosters faster motion of urea.

In 2006, D/V-Chikyu cruise CK06-06 drilled Hole C9001C at Site C9001 in the Northwest Pacific Ocean, 80 km east of the Shimokita Peninsula, Japan. An existing chronostratigraphic framework provides a continuous glacial-interglacial (G-I) climate record from which a diatom record of paleoenvironmental changes was developed across several G-I cycles. Species counts, diatom temperature values, and calculated sea-surface temperatures (SST) were produced for each sample and calibrated to prior diatom studies in this region. These features were used to characterize and compare interglacial maxima of Marine Isotope Stages (MIS) 1, 5e, 9 and 11 and transitions from the preceding glacial maxima. MIS 9 was the longest and warmest of the four interglacials examined, with a peak calculated temperature of 20.2 °C. Maximum temperature for MIS 1 of 14.9 °C is only 1 °C cooler than peak SSTs calculated for MIS 11 and 5e; however, the temperature trend for MIS 1 continues on a linear trajectory toward warmer modern temperatures to the top of the section. A lead/lag relationship between SST and the benthic oxygen isotope record of ice volume was observed at the onset and reversals of major G-I cycles.

The earliest known diatom fossils with well-preserved siliceous frustules are from Lower Cretaceous neritic marine deposits in Antarctica. In this study, we analyzed the cell wall structure to establish whether their cell and life cycles were similar to modern forms. At least two filamentous species (Basilicostephanus ornatus and Archepyrgus melosiroides) had girdle band structures that functioned during cell division in a similar way to present day Aulacoseira species. Also, size analyses of cell diameter indicated that the cyclic process of size decline and size restoration used to time modern diatom life cycles was present in five species from the Lower Cretaceous (B. ornatus, A. melosiroides, Gladius antiquus, Ancylopyrgus reticulatus, Kreagra forfex) and two species from Upper Cretaceous deposits (Trinacria anissimowii and Eunotogramma fueloepi) from the Southwest Pacific. The results indicate that the ‘Diatom Sex Clock’ was present from an early evolutionary stage. Other ecological adaptations included changes in mantle height and coiling. Overall, the results suggest that at least some of the species in these early assemblages are on a direct ancestral line to modern forms. This article is protected by copyright. All rights reserved.

Integrated Ocean Drilling Program (IODP) Expedition 337 drilled a new core in 2012 that extended the coring depth of Hole C9001D at Site C9001 below the 647 meters below seafloor (mbsf) that was penetrated in 2006 during the Chikyu Shakedown Cruise CK06-06. Drilling operations at Site C0020 (formerly Site C9001), located 80 km off the Shimokita Peninsula of northeastern Honshu, Japan, penetrated Hole C0020A to a total depth of 2466 mbsf. IODP Exp. 337 sought to explore a deep hydrocarbon system and coalbeds that, prior to drilling, were estimated to be of Eocene age. Combined shipboard diatom and palynological analyses, however, revealed unexpectedly thick sections of Pliestocene and Miocene sediments, an approximately 12–15 million year hiatus at 1086.5 mud depth below sea floor (m MSF), and coalbeds younger than originally predicted. New biostratigraphic results from Hole C0020A indicate the target coalbed is Early Miocene. The age of the youngest sediments obtained in Hole C0020A is revised from Late Pliocene to Early Pleistocene, and the basal age of Hole C9001C is confirmed as Early Pleistocene. The age of the deepest sediments obtained at Site C0020 is Late Oligocene-Early Miocene. All new data are integrated with the overlying interval obtained from Holes C9001C and C9001D to produce a composite chronostratigraphic framework for Site C0020.

The widespread occurrence of lower Eocene chert and porcellanite has been viewed as a major paleoceanographic issue since the advent of ocean drilling, and both biotic and abiotic forcings have been proposed to explain it. We present a reconstruction of indurated siliceous sediment (ISS) and preserved biosiliceous sediment (PBS) occurrences in the Atlantic Ocean through the Paleocene and Eocene (~66 through 34 Ma). ISS and PBS distributions reveal dissimilar temporal trends, with the peak of ISS occurrences coinciding with the Early Eocene Climatic Optimum, in line with previous studies. PBS occurrences show a generally increasing trend culminating between 44 and 43 Ma. The common co-occurrence of ISS and PBS, and their coherent geographic distribution lends strong support to the biogenic origin of the precursor to the widespread Paleogene ISS, and argues against an inorganic mode of early Cenozoic chert and porcellanite precipitation. Weight per cent biogenic opal records and trends in linear sedimentation rates indicate two plausible modes of silicification: 1) silicification due to prolonged exposure of biogenic opal-rich sediments to corrosive bottom waters; and 2) silicification due to elevated pressures and temperatures caused by rapid burial of biogenic opal-rich deposits. The confinement of ISS and PBS to proximal sites along continental margins points to the reliance of siliceous sedimentation through the Paleocene and Eocene on terrestrial supply of dissolved silicon. Consistent with this, quantitative siliceous microfossil assemblage records from the Blake Nose in the NW Atlantic indicate that the nutrient-rich marginal rather than oligotrophic pelagic settings hosted the majority of siliceous plankton production through the early Paleogene. The inorganic SiO2 precipitation model is unlikely to have been the dominant mechanism responsible for ubiquitous occurrences of early Paleogene ISS. We favor the biogenic ISS precursor scenario and reconcile it with the low-productivity early Cenozoic oceans by showing that large volumes of biogenic silica were supplied to the western North Atlantic Ocean from the North American margin through the Paleocene and Eocene. Dissolution of this surplus silica was facilitated by an early southwestward flow of young, SiO2-depleted waters from the North Atlantic. All these factors contributed to ISS and PBS focusing in the western North Atlantic through the early Paleogene.

Ocean Drilling Program (ODP) Site 1051 (Blake Nose, western North Atlantic) is of crucial importance for reconstructing diatom evolution and biosiliceous sedimentation patterns through the early Cenozoic period of extreme greenhouse warmth followed by the progressive global cooling. The magnetostratigraphy in Hole 1051A, however, has been subject to divergent interpretations resulting in multi-million-year age control uncertainties, especially for events surrounding the early to middle Eocene transition. To resolve these uncertainties, we compare the stratigraphy of Hole 1051A to the neighboring Holes 1050A, C. We compile the published biomagnetostratigraphic data for both sites and identify three possible magnetostratigraphic solutions for Hole 1051A, the difference being the number of hiati and their duration. In order to identify the most plausible magnetostratigraphic solution for Hole 1051A, we employ the graphic correlation method, in which we compare the depth of individual magnetic reversals in both study sites against an independent proxy, i.e., 49 diatom evolutionary events identified in Holes 1050A,C and 1051A. The distribution of diatom bioevents lends strong support to the presence of two major hiati in both study sites: the upper hiatus juxtaposes magnetozone C21n on C22n, and the lower hiatus juxtaposes magnetozone C23n on C24n, eliminating the record of the initial part of the Early Eocene Climatic Optimum. Diatom, calcareous nannofossil and foraminiferal biostratigraphic markers also indicate that Hole 1051A terminated within magnetozone C28n rather than C27n. This age interpretation is strongly supported by the alignment of high-resolution weight percent biogenic SiO2 records from both study sites. The revised age models developed here for Holes 1050A,C and 1051A have profound consequences for interpretations of western North Atlantic paleoceanographic and paleoclimatic history through the early Paleogene. We propose a revised labelling of the early Eocene carbon cycle perturbations identified to date in Hole 1051A, and show how published Blake Nose δ30Si records change when data from Sites 1050 and 1051 are rescaled to the age models proposed herein. We emphasize that these refinements to the stratigraphy of Sites 1050 and 1051 are based on a study of diatom bioevents, which are here identified and calibrated to the Geomagnetic Polarity Timescale. This successful application of diatom biostratigraphy is a substantial advance toward their future utility in providing high-resolution age control for Paleogene deep-sea sites.

Mercury capture is a major challenge in petroleum and natural gas processing. Recently, ionic liquids (ILs) have been introduced as mercury extractants from oil and gas. ILs yield very high mercury extraction efficiencies (>95%) from hydrocarbons, but their drawbacks include complex synthesis, toxicity, and difficult regeneration after mercury capture. In this work, a new technology using deep eutectic solvents (DESs) for elemental mercury (Hg0) extraction from hydrocarbons is demonstrated. DESs are an innovative class of designer solvents exhibiting similar properties as ILs, such as low vapor pressure and low flammability, but DESs are formed from inexpensive hydrogen-bond donor and acceptor compounds that are often biodegradable. In this work, four DESs were investigated including choline chloride:urea, choline chloride:ethylene glycol, choline chloride:levulinic acid, and betaine:levulinic acid, where the molar ratio is 1:2 in all cases. The DESs were tested for their thermal stability, density, and viscosity. Their performance for mercury extraction was assessed using saturated solutions in n-dodecane as the model oil. It was found that solvent to feed ratios of 1:1 and 2:1 at temperatures of 303.15 and 333.15 K and atmospheric pressure yield extraction efficiencies greater than 80% for all four DESs. First-principles molecular dynamics simulations probing the solvation in choline chloride:urea indicate a tight first coordination shell for mercury. Calculation of the Hg-Hg potential of mean force supports formation of a mercury-mercury polycation for a pair of Hg1+ ions, but not for pairs of Hg0 and Hg2+ species. Geometric analysis of the speciation and Mulliken population analysis support a redox reaction involving Hg2+ + 2Cl-.

The marine-based West Antarctic Ice Sheet (WAIS) is currently retreating due to shifting wind-driven oceanic currents that transport warm waters toward the ice margin, resulting in ice shelf thinning and accelerated mass loss of the WAIS. Previous results from geologic drilling on Antarctica's continental margins show significant variability in marine-based ice sheet extent during the late Neogene and Quaternary. Numerical models indicate a fundamental role for oceanic heat in controlling this variability over at least the past 20 My. Although evidence for past ice sheet variability has been collected in marginal settings, sedimentologic sequences from the outer continental shelf are required to evaluate the extent of past ice sheet variability and the associated oceanic forcings and feedbacks. International Ocean Discovery Program Expedition 374 drilled a latitudinal and depth transect of five drill sites from the outer continental shelf to rise in the eastern Ross Sea to resolve the relationship between climatic and oceanic change and WAIS evolution through the Neogene and Quaternary. This location was selected because numerical ice sheet models indicate that this sector of Antarctica is highly sensitive to changes in ocean heat flux. The expedition was designed for optimal data-model integration and will enable an improved understanding of the sensitivity of Antarctic Ice Sheet (AIS) mass balance during warmer-than-present climates (e.g., the Pleistocene "super interglacials," the mid-Pliocene, and the late early to middle Miocene). The principal goals of Expedition 374 were to • Evaluate the contribution of West Antarctica to far-field ice volume and sea level estimates; • Reconstruct ice-proximal atmospheric and oceanic temperatures to identify past polar amplification and assess its forcings and feedbacks; • Assess the role of oceanic forcing (e.g., sea level and temperature) on AIS stability/instability; • Identify the sensitivity of the AIS to Earth's orbital configuration under a variety of climate boundary conditions; and • Reconstruct eastern Ross Sea paleobathymetry to examine relationships between seafloor geometry, ice sheet stability/instability, and global climate. To achieve these objectives, we will • Use data and models to reconcile intervals of maximum Neogene and Quaternary Antarctic ice advance with far-field records of eustatic sea level change; • Reconstruct past changes in oceanic and atmospheric temperatures using a multiproxy approach; • Reconstruct Neogene and Quaternary sea ice margin fluctuations in datable marine continental slope and rise records and correlate these records to existing inner continental shelf records; • Examine relationships among WAIS stability/instability, Earth's orbital configuration, oceanic temperature and circulation, and atmospheric pCO2; and • Constrain the timing of Ross Sea continental shelf overdeepening and assess its impact on Neogene and Quaternary ice dynamics. Expedition 374 was carried out from January to March 2018, departing from Lyttelton, New Zealand. We recovered 1292.70 m of high-quality cores from five sites spanning the early Miocene to late Quaternary. Three sites were cored on the continental shelf (Sites U1521, U1522, and U1523). At Site U1521, we cored a 650 m thick sequence of interbedded diamictite, mudstone, and diatomite, penetrating the Ross Sea seismic Unconformity RSU4. The depositional reconstructions of past glacial and open-marine conditions at this site will provide unprecedented insight into environmental change on the Antarctic continental shelf during the early and middle Miocene. At Site U1522, we cored a discontinuous upper Miocene to Pleistocene sequence of glacial and glaciomarine strata from the outer shelf, with the primary objective to penetrate and date seismic Unconformity RSU3, which is interpreted to represent the first major continental shelf-wide expansion and coalescing of marine-based ice streams from both East and West Antarctica. At Site U1523, we cored a sediment drift located beneath the westerly flowing Antarctic Slope Current (ASC). Cores from this site will provide a record of the changing vigor of the ASC through time. Such a reconstruction will enable testing of the hypothesis that changes in the vigor of the ASC represent a key control on regulating heat flux onto the continental shelf, resulting in the ASC playing a fundamental role in ice sheet mass balance. We also cored two sites on the continental slope and rise. At Sit e U1524, we cored a Plio-Pleistocene sedimentary sequence on the continental rise on the levee of the Hillary Canyon, which is one of the largest conduits of Antarctic Bottom Water delivery from the Antarctic continental shelf into the abyssal ocean. Drilling at Site U1524 was intended to penetrate into middle Miocene and older strata but was initially interrupted by drifting sea ice that forced us to abandon coring in Hole U1524A at 399.5 m drilling depth below seafloor (DSF). We moved to a nearby alternate site on the continental slope (U1525) to core a single hole with a record complementary to the upper part of the section recovered at Site U1524. We returned to Site U1524 3 days later, after the sea ice cleared. W e then cored Hole U1524C with the rotary core barrel with the intention of reaching the target depth of 1000 m DSF. However, we were forced to terminate Hole U1524C at 441.9 m DSF due to a mechanical failure with the vessel that resulted in termination of all drilling operations and a return to Lyttelton 16 days earlier than scheduled. The loss of 39% of our operational days significantly impacted our ability to achieve all Expedition 374 objectives as originally planned. In particular, we were not able to obtain the deeper time record of the middle Miocene on the continental rise or abyssal sequences that would have provided a continuous and contemporaneous archive to the high-quality (but discontinuous) record from Site U1521 on the continental shelf. The mechanical failure also meant we could not recover sediment cores from proposed Site RSCR-19A, which was targeted to obtain a high-fidelity, continuous record of upper Neogene and Quaternary pelagic/hemipelagic sedimentation. Despite our failure to recover a shelf-to-rise transect for the Miocene, a continental shelf-to-rise transect for the Pliocene to Pleistocene interval is possible through comparison of the high-quality records from Site U1522 with those from Site U1525 an d legacy cores from the Antarctic Geological Drilling Project (ANDRILL).

Obtaining knowledge of the mutual miscibility of alkanes, surfactants, and water over a wide range of temperatures and pressures is of great relevance for the energy industry. Molecular simulations using advanced sampling techniques and transferable force fields can serve as a predictive method to study a variety of phase equilibria at different temperatures, pressures, and overall compositions. In this work, configurational-bias Monte Carlo simulations in the NpT Gibbs ensemble with the Transferable Potentials for Phase Equilibria (TraPPE) force field are applied to investigate the binary mixture of n -dodecane and ethanol at pressures of 0.1 and 100 MPa and the ternary mixture of these compounds with water at one state point. The simulations qualitatively reproduce the increase of the upper critical solution temperature (UCST) with increasing pressure, but the miscibility gap is overestimated at both pressures and the UCSTs are shifted up by about 50 K compared to the experimental values. The TraPPE model correctly shows a gradual decrease for the ethanol solubility in the n -dodecane-rich phase upon addition of water to the mixture.

Modern silicoflagellates are known to produce double skeletons, which are considered as pre-division stages; members of modern doublets are aligned at basal corners, using either pikes or organic material between the abbasal surfaces of the basal rings to hold together. In contrast, fossil doublets from the Cretaceous and Paleogene often have the corners of each skeleton oriented between those of the paired member in what is known as the Star-of-David configuration. Until recently, however, virtually nothing was known about the fine structure of fossil double skeletons. As a follow-up to our recent study on extant silicoflagellate doublets, we present a compilation of data on the fossil record of silicoflagellate double skeletons, with particular focus on the Cretaceous and Paleogene. Fossil silicoflagellate double skeleton specimens are extremely rare, with the oldest being from the late Santonian–early Campanian. In order to test whether silicoflagellates may have produced doublets prior to that time, we have constructed three-dimensional computer models of silicoflagellate double skeleton morphologies. Our findings indicate that doublet formation was part of the silicoflagellate reproductive cycle already since early in the evolutionary history of the group, before the development of the basal ring. Two distinct double skeleton configurations developed at some point in this evolution, with the Star-of-David group likely becoming extinct in the Oligocene, and the corner-aligned group represented by the Neogene and modern silicoflagellates. At present, the doublet configuration in fossil silicoflagellates can only be determined confidently with paired skeletons, but the occurrence, position and orientation of pikes may offer useful clues to interpret the doublet configuration from single skeletons. Unusual pike morphologies of some silicoflagellates from the Eocene strongly suggest a Star-of-David configuration. Silicoflagellate skeletal morphologies with pikes appear to be less abundant in the fossil record as double skeletons, and may disassociate more readily than morphologies that lack pikes and are instead held together by organic material between the basal rings.

The ANtarctic geological DRILLing Program (ANDRILL)is currently a consortium of five nations (Germany, Italy, New Zealand, the United Kingdom, a and the United States of America). By drilling, coring and analyzing stratigraphic archives along the Antarctic continental margin, ANDRILL pursues its primary goal of better understanding the role the Antarctic cryosphere plays in the global climate system (Harwood et al., 2006). The ANDRILL drilling system was developed to operate on both ice shelf and sea-ice platforms (Harwood et al., 2006; Falconer et al., 2007; Naish et al., 2007; Florindo et al., 2008). While thick multiyear sea ice provides stable and safe drilling platforms, identifying drilling targets in regions where these sea-ice conditions occur can be problematic due to a paucity of marine seismic reflection data because near-constant sea ice limits ship access (Fig. 1). In response to this problem ANDRILL developed new over-sea-ice seismic methods to extend seismic reflection data coverage to regions of multiyear sea ice.

Two of the oldest known silicoflagellate-bearing sediments, lower Albian at Ocean Drilling Program Site 693 in the Weddell Sea of Antarctica and Santonian in the Devon Island sequence of the Canadian Archipelago, are re-examined with a focus on silicoflagellate genera Variramus, Cornua, and Gleserocha that lack basal rings, a feature appearing during late Santonian/early Campanian time within the genus Corbisema. The extraordinary variability of Variramus aculeifera is studied, and a new genus Gleserocha is proposed for taxa with apical structures made of three struts, but without pikes. This new genus includes previously described Variramus wisei and Cornua tapiae and new species G. harrisonii, and is here proposed as a genus transitional between Variramus and Cornua. Two unusual new species of Cornua, C. deflandrei and C. witkowskiana, are also described and a revised terminology is proposed for the skeletal components of Cornua and closely related genera.

The Middle Eocene Climatic Optimum (MECO; ~ 40 million years ago [Ma]) is one of the most prominent transient global warming events in the Paleogene. Although the event is well documented in geochemical and isotopic proxy records at many locations, the marine biotic response to the MECO remains poorly constrained. We present new high-resolution, quantitative records of siliceous microplankton assemblages from the MECO interval of Ocean Drilling Program (ODP) Site 1051 in the subtropical western North Atlantic Ocean, which are interpreted in the context of published foraminiferal and bulk carbonate stable isotope (δ18O and δ13C) records. High diatom, radiolarian and silicoflagellate accumulation rates between 40.5 and 40.0 Ma are interpreted to reflect a ~ 500 thousand year (kyr) interval of increased nutrient supply and resultant surface-water eutrophication that was associated with elevated sea-surface temperatures during the prolonged onset of the MECO. Relatively low pelagic siliceous phytoplankton sedimentation accompanied the peak MECO warming interval and the termination of the MECO during a ~ 70 kyr interval centered at ~ 40.0 Ma. Following the termination of the MECO, a ~ 200-kyr episode of increased siliceous plankton abundance indicates enhanced nutrient levels between ~ 39.9 and 39.7 Ma. Throughout the Site 1051 record, abundance and accumulation rate fluctuations in neritic diatom taxa are similar to the trends observed in pelagic taxa, implying either similar controls on diatom production in the neritic and pelagic zones of the western North Atlantic or fluctuations in sea level and/or shelf accomodation on the North American continental margin to the west of Site 1051. These results, combined with published records based on multiple proxies, indicate a geographically diverse pattern of surface ocean primary production changes across the MECO. Notably, however, increased biosiliceous accumulation is recorded at both ODP Sites 1051 and 748 (Southern Ocean) in response to MECO warming. This may suggest that increased biosiliceous sediment accumulation, if indeed a widespread phenomenon, resulted from higher continental silicate weathering rates and an increase in silicic acid supply to the oceans over several 100 kyrs during the MECO.

New paleomagnetic results from lower-to-middle Miocene samples from Ocean Drilling Program (ODP) Holes 744A and 744B, cored during ODP Leg 119 on the southern Kerguelen Plateau (Indian Ocean sector; Southern Ocean), provide a chronostratigraphic framework for an existing and under-utilized paleoclimate archive during a key period of Antarctic climate and ice sheet evolution. Site 744 is strategically positioned for high-latitude paleoceanographic and paleoclimatic studies because it lies within the southern domain of the Antarctic Circumpolar Current (ACC) and in proximity to the large and active Lambert Glacier-Amery Ice Shelf drainage system of the East Antarctic Ice Sheet. Magnetostratigraphic results were reported previously for this site, but technical difficulties and limited sampling prevented confident correlation of the magnetic polarity record with the geomagnetic polarity timescale. Our results, which are constrained by new semi-quantitative analyses of diatom assemblages and radiolarian first and last appearance events that are evaluated within a regional Southern Ocean biostratigraphic dataset through Constrained Optimization (CONOP) model runs, permit significant refinement of previous age models for the lower-to-middle Miocene sequence recovered at Site 744 (spanning the interval from ~ 21 to 13.7 Ma). An extended record of sediment accumulation, with average sedimentation rates of ~ 0.7–0.9 cm/kyr, is interrupted by a series of hiatuses in the middle Miocene. These disruptions in sediment supply, or erosional events, could mark a local response of north–south fluctuations in the location and/or strength of the Antarctic Circumpolar Current during transient glacial events within the Mid-Miocene Climate Optimum (MMCO; ~ 17 to 14.45 Ma). With the enhanced age control provided by this study, combined with a refined chronostratigraphy for the underlying upper Eocene to Oligocene strata, Site 744 becomes a good candidate for future high-resolution stable isotope and microfossil paleoecological work, which will further elucidate the late Paleogene and early Neogene paleoenvironmental history of the Southern Ocean.

It is not clear how Southern Ocean phytoplankton communities, which form the base of the marine food web and are a crucial element of the carbon cycle, respond to major environmental disturbance. Here, we use a new model ensemble reconstruction of diatom speciation and extinction rates to examine phytoplankton response to climate change in the southern high latitudes over the past 15 My. We identify five major episodes of species turnover (origination rate plus extinction rate) that were coincident with times of cooling in southern high-latitude climate, Antarctic ice sheet growth across the continental shelves, and associated seasonal sea-ice expansion across the Southern Ocean. We infer that past plankton turnover occurred when a warmer-than-present climate was terminated by a major period of glaciation that resulted in loss of open-ocean habitat south of the polar front, driving non-ice adapted diatoms to regional or global extinction. These findings suggest, therefore, that Southern Ocean phytoplankton communities tolerate “baseline” variability on glacial–interglacial timescales but are sensitive to large-scale changes in mean climate state driven by a combination of long-period variations in orbital forcing and atmospheric carbon dioxide perturbations.

Stratigraphic drilling from the McMurdo Ice Shelf in the 2006/2007 austral summer recovered a 1284.87 m sedimentary succession from beneath the sea floor. Key age data for the core include magnetic polarity stratigraphy for the entire succession, diatom biostratigraphy for the upper 600 m and 40Ar/39Ar ages for in-situ volcanic deposits as well as reworked volcanic clasts. A vertical seismic profile for the drill hole allows correlation between the drill hole and a regional seismic network and inference of age constraint by correlation with well‐dated regional volcanic events through direct recognition of interlayered volcanic deposits as well as by inference from flexural loading of pre‐existing strata. The combined age model implies relatively rapid (1 m/2–5 ky) accumulation of sediment punctuated by hiatuses, which account for approximately 50% of the record. Three of the longer hiatuses coincide with basin‐wide seismic reflectors and, along with two thick volcanic intervals, they subdivide the succession into seven chronostratigraphic intervals with characteristic facies: 1. The base of the cored succession (1275–1220 mbsf) comprises middle Miocene volcaniclastic sandstone dated at approx 13.5 Ma by several reworked volcanic clasts; 2. A late-Miocene sub-polar orbitally controlled glacial–interglacial succession (1220–760 mbsf) bounded by two unconformities correlated with basin‐wide reflectors associated with early development of the terror rift; 3. A late Miocene volcanigenic succession (760–596 mbsf) terminating with a ~1 my hiatus at 596.35 mbsf which spans the Miocene–Pliocene boundary and is not recognised in regional seismic data; 4. An early Pliocene obliquity-controlled alternating diamictite and diatomite glacial–interglacial succession (590–440 mbsf), separated from; 5. A late Pliocene obliquity-controlled alternating diamictite and diatomite glacial–interglacial succession (440–150 mbsf) by a 750 ky unconformity interpreted to represent a major sequence boundary at other locations; 6. An early Pleistocene interbedded volcanic, diamictite and diatomite succession (150–80 mbsf), and; 7. A late Pleistocene glacigene succession (80–0 mbsf) comprising diamictite dominated sedimentary cycles deposited in a polar environment.

Understanding of Neogene climate in Antarctica has been an intractable problem for over 20 years. Competing models of the effect of Pliocene climatic warmth have not yet been reconciled. New sedimentological and paleontological data from Dry Valley Drilling Project core (DVDP-10) demonstrate a dynamic climate regime for the early and mid-Pliocene record preserved in the floor of Taylor Valley. This succession of interbedded mudrocks, sandstones, conglomerates and diamictites includes evidence for times when the coastal plain landscape of Taylor Valley may have been vegetated by higher land plants. Biostratigraphic data from DVDP-10 are utilized to correlate to the more detailed and finely resolved record in the AND-1B core in southern McMurdo Sound. Accordingly, the interval in DVDP-10 that records dynamic environmental fluctuations with a possible vegetated coastal plain land system is bracketed at 4.92–4.25 Ma. These data suggest that low altitude terrains of the Dry Valleys during the Early Pliocene were subjected to glacial-interglacial cycles in which some interglacials were largely ice-free.

Interpretation of glacimarine sedimentary records from Antarctic shelf drillholes has been hampered by the ambiguous age of strata where erosional unconformities and coarse diamictite deposits truncate or omit the magnetostratigraphic and biostratigraphic units used for correlation. However, new quantitative biostratigraphic techniques enable the correlation of sparse, incomplete, and often reworked Plio-Pleistocene records of Ross Sea fossil diatom flora with the more extensively documented but potentially diachronous offshore history of species' first and last appearance datums (FADs and LADs). The approach uses comprehensive regional databases of fossil records and computer-automated search algorithms to find the multidimensional line of correlation (LOC) that best fits local observations, and to identify regionally isochronous biostratigraphic markers. Different model configurations can be used to produce LOCs that represent alternative working hypotheses regarding reworking and other sources of misfit in the biostratigraphic record, and that together provide an envelope of uncertainty for age interpretation. An integrated, quantitative chronostratigraphic model for the ANDRILL-1B drillcore was developed iteratively: an initial age model was constructed solely from preliminary on-ice observations of fossil diatom highest and lowest occurrences (HOs and LOs) and their correlation with a database of other local event records from 24 DVDP, CIROS, and IODP drillcore sections. The model was subsequently updated as off-ice work yielded additional biostratigraphic marker events and revised event horizons, Ar/Ar ages for volcanic material, better-constrained magnetostratigraphic interpretation, and refinements to computational/analytical methodology. The current quantitative biostratigraphic age model for the AND-1B hole integrates the local ranges of 29 diatom taxa, five dated volcanic samples, and independently constrained ages of five paleomagnetic reversals. During analysis, three model families were compared, each of which make different assumptions about the scale and influence of reworking and caving on observed biostratigraphic ranges, varying from assumption of no reworking/caving to widespread reworking/caving. Of these, the Hybrid Range Model, which allows for intermediate levels of reworking expected in a glaciomarine depositional environment, was found to give the most robust and reliable single LOC, even with immature input biostratigraphic data. However, alternative models used together provide an envelope of uncertainty around this preferred LOC. Results corroborate almost all of the on-ice geomagnetic polarity reversal age interpretations, but identify a previously unrecognized disconformity (~ 800 kyr hiatus) near 440 mbsf. In spite of substantial augmentation and progressive refinement of the AND-1B input dataset, successive versions of the output LOC retain the same fundamental structure and shape with only relatively minor, fine-scale differences. The age model's remarkable stability indicates that quantitative biostratigraphic analysis is capable of constructing robust and reliable regional correlation schemes and local section chronologies, even in cases of discontinuous stratigraphy and with relatively immature or incomplete datasets.

The ANDRILL AND-1B drillcore in southern Victoria Land Basin, Antarctica recovered an upper Miocene to early Pleistocene continental shelf stratigraphic section, including a spectacular Pliocene and Pleistocene sequence of alternating diamictite and diatom-rich sediments. This punctuated sequence reflects variation between glacial sediments deposited by ice advance over the site and open-marine diatom productivity and sedimentation. An early Pliocene age for the base of diatom-rich sediment is constrained through integrated diatom biostratigraphy and magnetostratigraphy. The presence of marine diatom Shionodiscus tetraoestrupii from the top of the core to 583.64 mbsf indicates the lowest diatom-bearing sediments are younger than 5 Ma. This drillcore provides important new chronostratigraphic control for paleoenvironmental changes also recorded in three drillcores from the western coast of the McMurdo Sound area, DVDP-10 and -11 in Taylor Valley and CIROS-2 from the seaward edge of Ferrar Fjord. The refined continental shelf biostratigraphy developed from AND-1B provides a framework for regional correlation to understand better the timing and character of large paleoenvironmental changes in the western Ross Sea that involve the history of the West Antarctic Ice Sheet (WAIS). Multivariate analysis, along with traditional biostratigraphic approaches, enables the correlation and comparison of coeval intervals in these drillcores. A composite stratigraphic sequence from these four cores suggests the early and mid-Pliocene Ross Sea experienced extended intervals of open-marine conditions with minimal sea-ice cover and high diatom production and sedimentation. This new information provides important constraints on Antarctic paleoclimate and ice sheet history during an important interval when global climate was warmer than today. The history preserved in these four drillcores will be an important tool to guide and test future ice sheet and climate models.

The near-shore open-marine diatom record recovered in the ANtarctic geological DRILLing (ANDRILL) McMurdo Ice Shelf Project (MIS) AND-1B drillcore, McMurdo Sound, Antarctica, advances our understanding of the marine conditions present in the southern Ross Sea during the Pliocene and early Pleistocene. This diatom history is recorded within alternating diamictite and diatomite that reflect alternating glacial activity and high marine primary productivity. The diatomite units were deposited in a continental shelf open-marine setting during periods of reduced ice cover in West Antarctica. A new diatom biostratigraphic scheme spanning the last ca. 5 Ma is proposed for the Antarctic near-shore area, based on prior work from high latitude drillcores. Four new zones are proposed for the Pliocene/Pleistocene, with eight in total for the new zonal scheme, utilizing Actinocylus fasciculatus , Actinocyclus maccollumii , Fragilariopsis bohatyii , Rouxia antarctica , and Thalassiosira fasciculata as new zonal markers. The early Pliocene shares the most assemblage commonality with that of the Southern Ocean with greater numbers of endemic species observed in the late Pliocene and early Pleistocene; a group of related Fragilaripsis species characterizes much of this later part of the time column. Two new species are proposed, Fragilariopsis tigris sp. nov. Riesselman and Thalassiosira teres sp. nov. Winter; a formal name is also proposed for another species, Rhizosolenia harwoodii sp. nov. Winter. The new zonation is tied to a robust chronology utilizing diatom biostratigraphy, volcanic 40 Ar/ 39 Ar ages and magnetostratigraphy.

The purpose of this quasi-experimental study was to determine the effects of a field-based, inquiry-focused course on pre-service teachers’ geoscience content knowledge, attitude toward science, confidence in teaching science, and inquiry understanding and skills. The field-based course was designed to provide students with opportunities to observe, compare, and investigate geological structures in their natural environment and to gain an understanding of inquiry via hands-on learning activities designed to immerse students in authentic scientific investigation. ANCOVA and MANCOVA analyses examining differences in outcome measures between students in the field experience (n = 25) and education students enrolled in the traditional, classroom-based course (n = 37) showed that students in the field course generally had significantly higher scores. Results provide evidence of the value of the field and inquiry-based approach in helping pre-service teachers develop the needed skills and knowledge to create effective inquiry-based science lessons.

The Middle Eocene Climatic Optimum (MECO) is a major transient warming event that occurred at ~ 40 Ma and reversed a long-term cooling trend through the early and middle Eocene. We report the results of a high-resolution, quantitative study of siliceous microfossils at Ocean Drilling Program Sites 748 and 749 (Southern Kerguelen Plateau, Southern Ocean, ~ 58°S) across a ~ 1.4 myr interval spanning the MECO event. At both sites, a significant increase in biosiliceous sedimentation is associated with the MECO event. Rich siliceous planktonic microfossil assemblages in this interval are unusual in that they are dominated by ebridians, with radiolarians as a secondary major component. Silicoflagellates and diatoms comprise only a minor fraction of the assemblage, in contrast to siliceous microfossil assemblages that characterize modern Southern Ocean sediments. Based on our new siliceous microfossil records, we interpret two ~ 300 kyr periods of elevated nutrient availability in Southern Ocean surface waters which span the peak warming interval of the MECO and the post-MECO cooling interval. A diverse assemblage of large silicoflagellates belonging to the Dictyocha grandis plexus is linked to the rapid rise in sea-surface temperatures immediately prior to peak warmth, and a pronounced turnover is observed in both ebridian and silicoflagellate assemblages at the onset of peak warming. The interval of peak warmth is also characterized by high abundance of cosmopolitan ebridians (e.g., Ammodochium spp.) and silicoflagellates (e.g., Naviculopsis spp.), and increased abundance of tropical and subtropical diatom genera (e.g., Asterolampra and Azpeitia). These observations confirm the relative pattern of temperature change interpreted from geochemical proxy data at multiple Southern Ocean sites. Furthermore, rapid assemblage changes in both autotrophic and heterotrophic siliceous microfossil groups indicate a reorganization of Southern Ocean plankton communities in response to greenhouse warming during the MECO event.

Late Neogene stratigraphy of southern Victoria Land Basin is revealed in coastal and offshore drill cores and a network of seismic data in McMurdo Sound, Antarctica. These data preserve a record of ice sheet response to global climate variability and progressive cooling through the past 5 million years. Application of a composite standard age model for diatom event stratigraphy to the McMurdo Sound drill cores provides an internally precise mechanism to correlate stratigraphic data and derive an event history for the basin. These marine records are indirectly compared to data obtained from geological outcrop in the Transantarctic Mountains to produce an integrated history of Antarctic Ice Sheet response to climate variability from the early Pliocene to Recent. Four distinct chronostratigraphic intervals reflect stages and steps in a transition from a relatively warm early Pliocene Antarctic coastal climate to modern cold polar conditions. Several of these stages and steps correlate with global events identified via geochemical proxy data recovered from deep ocean cores in mid to low latitudes. These correlations allow us to consider linkages between the high southern latitudes and tropical regions and establish a temporal framework to examine leads and lags in the climate system through the late Neogene and Quaternary. The relative influence of climate–tectonic feedbacks is discussed in light of glacial erosion and isostatic rebound that also influence the history along the Southern Victoria Land coastal margin.

We present four genera of bipolar centric diatoms with linking structures located on the valve face: Rutilaria (including two new species from the Cretaceous), Spinivinculum, Pseudorutilaria and Kisseleviella, which are commonly classified in the family Rutilariaceae. Functional comparison of their linking structures and modes of chain formation shows considerable diversity and does not support a close phylogenetic relationship among them. In order to reflect the probable phylogeny of this group, the Rutilariaceae is retained as a monotypic family, while Kisseleviella is transferred to the Cymatosiraceae. Rymariopsis gen. nov. is proposed as a possible link between the Hemiaulaceae and the Rutilariaceae. Based on the comparison of the stratigraphic ranges of these taxa with other diatoms, we explore the possibility of a close phylogenetic relationship between bipolar centric diatoms with centrally located linking structures and pennate diatoms, as suggested by recent molecular phylogenies. As a consequenc...

Present understanding of Antarctic climate change during the Early to Mid-Miocene, including major cycles of glacial expansion and contraction, relies in large part on stable isotope proxies from deep sea core drilling. Here, we summarize the lithostratigraphy of the ANDRILL Southern McMurdo Sound Project drillcore AND-2A. This core offers a hitherto unavailable ice-proximal stratigraphic archive from a high-accommodation continental margin setting, and provides clear evidence of repeated fluctuations in climate, ice expansion/contraction and attendant sea-level change over the period c. 20.2–14.2 Ma, with a more fragmentary record of Late Miocene and Pliocene time. The core is divided into seventy-four high-frequency (fourth- or fifth-order) glacimarine sequences recording repeated advances and retreats of glaciers into and out of the Victoria Land Basin. The section can be resolved into thirteen longer-term, composite (third-order) sequences, which comprise packages of higher frequency sequences that show a consistent stratigraphic stacking pattern (Stratigraphic Motif). The distribution of the six recognized motifs indicates intervals of less and more ice-proximal, and temperate to subpolar/polar climate, through the Miocene period. The core demonstrates a dynamic climate regime throughout the Early to Mid-Miocene that may be correlated to some previously-recognized events such as the Mid-Miocene Climatic Optimum, and provides a detailed reference point from which to evaluate stable isotope proxy records from the deep-sea.

Devon and Ellef Ringnes islands in the Canadian Arctic Archipelago contain well-preserved Santonian through early Campanian silicoflagellates. These occur in three unusual assemblages, which comprise three biostratigraphic zones. The oldest, the Vallacerta tumidula Partial Range Zone of Santonian age, contains an extremely variable microflora that includes species of the poorly-known genus Variramus, two new species of Cornua, and a new genus Umpiocha. The Schulzyocha ruppelii Range Zone of early Campanian age includes several species of the new genus Schulzyocha, reflecting quadrate silicoflagellate skeletal morphologies that lack a basal structure. The youngest assemblage includes the poorly-known species Cornua trifurcata, the nominative taxon of the C. trifurcata Partial Range Zone (proposed by McCartney et al., in press c ; emended herein), which allows a correlation with a silicoflagellate-bearing sequence from the Horton River area, Northwest Territories of Canada. This report presents information on 24 silicoflagellate taxa, proposes 2 new genera, Schulzyocha and Umpiocha, and describes 13 new species and 1 new combination. All of these new taxa disappear by the top of the Campanian Cornua trifurcata Partial Range Zone. These assemblages reveal a new history of silicoflagellate evolution prior to the late Campanian, the period from which most of our prior knowledge about Cretaceous silicoflagellates was derived. The assemblages show progressive change from skeletons with highly variable morphologies to more stable silicoflagellate skeletal geometry. Two important Corbisema species, C. apiculata and C. archangelskiana, appear to be derived from separate lines within Cornua in the latest Santonian and early Campanian. The important Cretaceous genus Lyramula makes its first appearance at the beginning of the Campanian.

Recent studies of Santonian and Campanian sediments from several sites in northern Canada identified two new silicoflagellate genera, many new and unusual species, a Santonian assemblage of Variramus and abundant specimens of the poorly known genus Cornua. This allowed a reassessment of Variramus with information from three new species, and transfer of V. loperi into the new genus Schulzyocha, along with five new species that form an unusual assemblage in the early Campanian. A second new and unusual genus, Umpiocha, and two new species of Cornua provide knowledge of a previously unknown diversity of silicoflagellates in the Santonian. The first appearance of Lyramula is now dated as early Campanian. The occurrence of C. poretzkajae in early Campanian offers new information on the early history and timing of the transition from Cornua to Corbisema. Sediments from higher in the Campanian show development of Corbisema apical plates, and unusual new skeletal morphologies of Arctyocha. These and other discoveries present an improved understanding of early silicoflagellate evolution. Most of the recently described species lack a basal ring, though many of the skeletal morphologies allow for interpretation of a basal plane. Variramus lacks an obvious basal plane, suggesting a more primitive skeletal symmetry, which is interpreted to have given rise to Lyramula (also lacking an apparent basal plane and not known to produce double skeletons). Recent discoveries of rare double skeletons for Corbisema, Schulzyocha and Vallacerta show the skeletons rotated with respect to known Cenozoic configurations. This information, along with a better understanding of Cornua and knowledge of the enigmatic Umpiocha, provides an opportunity to fill part of the 35–40 million year gap between the previously known Albian and late Campanian/Maastrichtian silicoflagellate occurrences. These new interpretations of early silicoflagellate evolution are presented in the context of studies by Deflandre, Gleser and other previous research.

Two new genera of fossil diatoms, Blochia gen. nov. and Nikolaevia gen. nov., are proposed from Kanguk Formation (Upper Cretaceous) outcrops on Devon Island, Canadian Arctic margin. Both genera display morphological features suggesting a relationship with Stellarima Hasle & Sims. Nikolaevia is unusual in having an external opening of the rimoportula in the form of an arcuate canal. Blochia is a genus of large diatoms that are ornamented with spines, and bear a centrally positioned rimoportula with a prominent external tube. Inferred vegetative and resting stages are presented for Nikolaevia symbolica sp. nov., while Blochia magna sp. nov. is considered a resting spore. Observations summarized in the present paper further document the diversity of the Stellarimaceae in one of the oldest available fossil localities providing well-preserved material.

A recently discovered deposit of Late Cretaceous diatoms on Devon Island contains exceptionally well-preserved siliceous microfossils. Two diatom taxa from this deposit, previously identified as belonging to the genera Actinodictyon and Lepidodiscus, were examined with light and scanning electron microscopy. The present study revealed that these two taxa belong to the genus Lepidodiscus. Both were found to display an extremely complex structure of their radially and concentrically undulate valves, involving porous canals, hyaline areas and an external network of thick costae locally thickened to form tubercles. Different number of alternating depressed and elevated sectors located in the marginal zone of the valve, and different structures associated with the external openings of marginal rimoportulae were found to be a sufficient basis for erecting a new species, Lepidodiscus annamariae sp. nov. The excellent preservation of the Devon Island material also allowed for a documentation of the structure of the girdle, composed of multiple open bands.

Our study characterizes glacial and interglacial deposition on two Antarctic margins in order to discriminate between regional and continent-wide early to middle Pliocene warm intervals that caused sea-ice reduction and continental ice sheet retreat. We use a multi-proxy (i.e., sediment facies and grain size, siliceous microfossils, biogenic opal, geochemical composition and clay mineralogy) approach to examine sediments recovered in drill holes from the West Antarctic Peninsula and the East Antarctic Prydz Bay margins, focusing on the climatic record between 4 and 3.5 Ma. Warm conditions in both East and West Antarctica are recorded, which based on our age model correspond to periods of prolonged or extreme warmth correlated with isotopic stages Gi5, Gi1, MG11 and MG7. For the Gi5 interglacial our data corroborates the 60% Dictyocha percentage at 34.60 mbsf previously reported from Prydz Bay and interpreted to indicate a SSST of about 5.6 °C above present. Our higher-resolution sampling interval shows Dictyocha percentages up to 87.5%, suggesting even higher SSSTs above present levels. During MG11, which coincides with the section dated by the magnetic polarity reversal Gilbert-Gauss at 3.58 Ma, SSSTs were tentatively 2.5°–4° warmer than present, and reduced sea-ice cover in Prydz Bay and probably also west of the Antarctic Peninsula is indicated by increased primary productivity. In addition, a reduction of ice sheet size is suggested by the bioturbated and IRD-enriched facies that characterize these high-productivity intervals. Based in our age model and calculated sedimentation rates glacial–interglacial cyclicity between 4 and 3.5 Ma in the cores from Antarctic Peninsula and Prydz Bay Sites, result in frequencies consistent with obliquity and precession forcing. The prolonged early-middle Pliocene warm period was superimposed on a cooling trend recorded by the: 1) increase of the terrigenous sediment supply at all our sites starting between 3.7 and 3.6 Ma, and 2) decrease in SSSTs (from > 5.6 °C at 3.7 Ma to 4°–2.7 °C at 3.6 Ma, and 2.5 °C at 3.5 Ma.) indicated by the silicoflagellate W/C R from Site 1165. We postulate that, although the start of a cooling trend is recorded at about 3.7–3.6-Ma, relatively warm conditions prevailed until 3.5 Ma capable of maintained open marine conditions with reduced or no sea-ice and reduced ice sheet volume and extent. The information in this paper regarding the timing of continental-wide and regional warm events and the paleoenvironmental conditions that characterized them (i.e., SSST, extent of sea ice, and ice sheet size) are relevant to help constrain paleoclimate and ice sheet models for the early-middle Pliocene, a time period when the level of warming according to the Intergovernmental Panel on Climate Change 2007 report, is within range of the estimates of the Earth's global temperature increases for the 21st century. These data, when linked to modeling studies like those of Pollard and DeConto (2009) will further our understanding of how these ice sheets may respond to future warming of the southern high latitudes.

A new fossil araphid genus and species, Creania lacyae, and a new fossil araphid species, Synedropsis cheethamii are described from Oligocene to lower Miocene sediments recovered from the Victoria Land Basin, Antarctica. The new genus Creania possesses round, uniseriate areolae, a central sternum and apical fields composed of a row of short rectangular openings. Presence of two distinctive rimoportulae per valve, and the shape and number of apical field openings are the primary features that distinguish the genus. The genus is (at present) monospecific. The new species Synedropsis cheethamii is closely related to the modern species Synedropsis lata and S. lata var. angustata but is distinguished by its less dense stria, the shape and position of the rimoportula and the shape and structure of the apical slit field. The presence of Synedropsis in upper Oligocene sediments marks the nearliest occurrence of this genus which is commonly associated with sea-ice. We postulate that both Synedropsis cheethamii and...

As the earth faces a warming climate, the rock record reminds us that comparable climatic scenarios have occurred before. In the Late Cretaceous, Arctic marine organisms were not subject to frigid temperatures but still contended with seasonal extremes in photoperiod. Here, we describe an unusual fossil assemblage from Devon Island, Arctic Canada, that offers a snapshot of a ca 75 Myr ago marine palaeoecosystem adapted to such conditions. Thick siliceous biogenic sediments and glaucony sands reveal remarkably persistent high primary productivity along a high-latitude Late Cretaceous coastline. Abundant fossil faeces demonstrate that this planktonic bounty supported benthic invertebrates and large, possibly seasonal, vertebrates in short food chains. These ancient organisms filled trophic roles comparable to those of extant Arctic species, but there were fundamental differences in resource dynamics. Whereas most of the modern Arctic is oligotrophic and structured by resources from melting sea ice, we suggest that forested terrestrial landscapes helped support the ancient marine community through high levels of terrigenous organic input.