Logging data are measurements of physical properties of the formation surrounding a borehole, acquired in situ after completion of coring (wireline logging) or during drilling (Logging-While-Drilling, LWD). The range of data (resistivity, gamma radiation, velocity, density, borehole images,…) in any hole depends on the scientific objectives and operational constraints.

Logging data are measurements of physical properties of the formation surrounding a borehole, acquired in situ after completion of coring (wireline logging) or during drilling (Logging-While-Drilling, LWD). The range of data (resistivity, gamma radiation, velocity, density, borehole images,…) in any hole depends on the scientific objectives and operational constraints.

Logging data are measurements of physical properties of the formation surrounding a borehole, acquired in situ after completion of coring (wireline logging) or during drilling (Logging-While-Drilling, LWD). The range of data (resistivity, gamma radiation, velocity, density, borehole images,…) in any hole depends on the scientific objectives and operational constraints.

Supplemental Instruction (SI) is a voluntary, non-remedial, peer-facilitated, course-specific intervention that has been widely demonstrated to increase student success, yet concerns persist regarding the biasing effects of disproportionate participation by already higher-performing students. With a focus on maintaining access for all students, a large, public university in the Western United States used student demographic, performance, and SI participation data to evaluate the intervention’s efficacy while reducing selection bias. This analysis was conducted in the first year of SI implementation within a traditionally high-challenge introductory psychology course. Findings indicate a statistically significant relationship between student participation in SI and increased odds of successful course completion. Furthermore, the application of Coarsened Exact Matching reduced concerns that increased course performance was attributed to an over-representation of higher performing students who elected to attend SI Sessions.

The Eocene–Oligocene Transition (EOT) is marked by a double-stepped positive δ18O excursion of ~1.3‰ and a deepening of the calcium compensation depth (CCD) interpreted to represent marked Antarctic glaciation and global ocean–atmosphere cooling (i.e., Oi-1 event). A ~0.5-m (~55–70kyr) resolution ostracode faunal study of the Massicore, drilled up-section from the Italian Massignano Quarry containing the Eocene–Oligocene Global Stratotype Section and Point (GSSP), revealed a relative increase in Krithe and decreases in faunal evenness and Shannon Index correlative to the Oi-1 event. These transient faunal changes may reflect local water column changes (e.g., export production) or intensified thermohaline flow of cooler deep waters through the paleotethyan seaway. Comparison of these Massicore ostracode faunal data to previously-published Massignano Quarry ostracode faunal data reveals similar relative abundances among common taxa where the study intervals overlap, and thereby provide a more complete Tethyan ostracode record spanning all of C13n and the broader EOT at the GSSP locality.

Distinct magnetic properties of marine sediments that record the Palaeocene–Eocene thermal maximum (PETM) have been suggested to be due to a bacterial magnetofossil signal that is linked to enhanced weathering conditions during the PETM. We document the dominance of bacterial magnetite in deep-sea sediments from southern Kerguelen Plateau (Ocean Drilling Program Hole 738C, southern Ocean) not only during the PETM, but also before and after the thermal event. This occurrence of magnetofossils throughout the PETM indicates that the occurrence of bacterial magnetosomes is not due to a preservation effect. Instead, we suggest that it is due to sustained mild iron-reducing conditions that dissolved the most labile aeolian-derived iron, which favoured continued magnetotactic bacterial activity without being strong enough to dissolve the less reactive magnetite and haematite. Enhanced aeolian haematite abundances at the beginning of the PETM indicate drier conditions on the neighbouring Antarctic continent at those times. Our results provide evidence that iron fertilisation by aeolian dust was the main limiting factor that conditioned proliferation of magnetotactic bacteria in the deep sea at the southern Kerguelen Plateau, with the exception of two short periods of rapidly changing palaeoenvironmental conditions at the onset and termination of the PETM. Increased iron supply from aeolian dust, that enhanced oceanic primary productivity and subsequent delivery of organic carbon to the seafloor, along with mild iron-reducing diagenetic conditions, seem to have been necessary to provide the iron needed for magnetite biomineralization by magnetotactic bacteria to drive their marked increase in abundance in the studied PETM record from southern Kerguelen Plateau. Our analyses of a deep-sea PETM record from Hole 1051B at Blake Nose (Atlantic Ocean) failed to identify magnetofossils despite evidence for the occurrence of magnetite and haematite of probable aeolian origin. Contrasting magnetic properties at these PETM sections indicate that further work is needed to understand the palaeoenvironmental and diagenetic factors whose interactions lead to production and preservation of magnetofossils in deep-sea sediments.

The discovery and calibration of high resolution paleoceanographic proxies is necessary to extend historic climate records and to understand regional climate variability. Chemical variations of skeletal remains have emerged as an often reliable recorder of environmental conditions. Specifically, Ba/Ca ratios have been correlated to temperature, salinity, seawater Ba/Ca, and phytoplankton biomass, although, many of these relationships appear taxon- and location-specific. To assess the sub-weekly Ba/Ca variations in the intertidal shallow-burrowing bivalve Donax gouldii, specimens were collected from the Southern California Bight, skeletal growth increments were cross-dated based on tidal-driven growth patterns, and skeletal aragonite Ba/Ca was determined using laser ablation inductively coupled plasma mass spectrometry. Cross-dated growth among specimens revealed a simultaneous, large, and transient Ba/Ca peak in all shells. The timing of peak Ba/Ca was compared to a suite of locally measured physical and biological data, including temperature, salinity, density, nitrate, silicate, chlorophyll, diatom abundance, dinoflagellate abundance, and phytoplankton community composition. Based on cross-dated chronologies, Ba/Cashell is significantly correlated with Chl a from six and nine days prior and nutrients (nitrate, phosphate, silicate, and nitrite) from three days prior. In this system diatom abundance was not related to Ba/Cashell. Transiently higher seawater Ba/Ca resulting from upwelling may be reflected in peak Ba/Cashell, however the exact mechanisms leading to population wide Ba/Ca peaks remains enigmatic.

Spatiotemporal patterns of carbonate dissolution provide a critical constraint on carbon input during an ancient (~55.5Ma) global warming event known as the Paleocene–Eocene thermal maximum (PETM), yet the magnitude of lysocline shoaling in the Southern Ocean is poorly constrained due to limited spatial coverage in the circum-Antarctic region. This shortcoming is partially addressed by comparing patterns of carbonate sedimentation at the Site 690 PETM reference section to those herein reconstructed for nearby Site 689. Biochemostratigraphic correlation of the two records reveals that the first ~36ka of the carbon isotope excursion (CIE) signaling PETM conditions is captured by the Site 689 section, while the remainder of the CIE interval and nearly all of the CIE recovery are missing due to a coring gap. A relatively expanded stratigraphy and higher carbonate content at mid-bathyal Site 689 indicate that dissolution was less severe than at Site 690. Thus, the bathymetric transect delimited by these two PETM records indicates that the lysocline shoaled above Site 689 (~1,100m) while the calcite compensation depth remained below Site 690 (~1,900m) in the Weddell Sea region. The ensuing recovery of carbonate sedimentation conforms to a bathymetric trend best explained by gradual lysocline deepening as negative feedback mechanisms neutralized ocean acidification. Further, biochemostratigraphic evidence indicates the tail end of the CIE recovery interval at both sites has been truncated by a hiatus most likely related to vigorous production and advection of intermediate waters.

The oxygen and strontium isotopic ratios of marine carbonates are widely employed to derive paleotemperature and age, respectively. While open ocean samples are the standard source for these measures, shelf settings can also provide detailed records. However, the implementation of shelf data for these purposes has been hindered by the perception that local environmental conditions (such as freshwater influx) confound regional and global signals. Here, we directly evaluate this concern by assessing the spatial variability in the isotopic composition of biogenic carbonate precipitated along the depositional strike of an inner shelf environment. Data are derived from mollusc shells collected from a stratigraphically restricted, transgressive unit in the early Eocene (~55Ma) of the US Gulf Coastal Plain (GCP). Lithofacies and fossil assemblages suggest that an estuary was present in the westernmost study region, whereas more typically marine facies predominated elsewhere. Isotopic composition varies predictably with paleoenvironmental setting; shells from the estuary have δ18O values and 87Sr/86Sr ratios that reflect high freshwater input. Specimens in the eastern GCP, however, from within and between outcrops separated by up to 400km, all yield similar results. Serial microsampling reveals congruence not only in mean δ18O values, but also in winter and summer extremes. Estimated paleotemperatures (mean annual temperature of 26°C) agree well with proxy and model evidence for the early Eocene and the GCP, and 87Sr/86Sr ratios are consistent with the established early Eocene seawater ratio. The fidelity of isotopic values relative to environment indicates that shallow shelf records have much to contribute to studies of ancient climate and ocean chemistry.

Paleocommunity research efforts have explored a multitude of faunal assemblages using a wide range of sampling and analytical methods to infer a paleoecological signal. Here, we derive six secondary datasets from a single stratigraphic series of faunal assemblages in the Finis Shale (Pennsylvanian) of Jacksboro, Texas, USA, using a variety of data categorization decisions (i.e., abundance versus calcified biomass, all taxa versus selected indicator taxa, and generic versus higher clade resolution). Biomass- and abundance-derived datasets were not significantly different in terms of evenness, Shannon’s information index, or Simpson’s diversity index. Using Bray-Curtis and nonmetric multidimensional scaling ordinations, with Sorenson and relative Sorenson distance measures, ordination axis scores of the six derived datasets were all significantly correlated with one another, suggesting little difference in their respective paleoecological signals. Three potential explanations for this consistent paleoecological signal, regardless of which data categorizations are employed, include: (1) the dominance of a few brachiopod taxa overwhelmingly influenced the community structure, (2) relatively constrained environmental conditions limited community variation, and (3) low variation in specimen size minimized potential differences among abundance and calcified biomass categorizations. We suggest that other datasets with greater diversities, greater evenness, or from a wider range of paleoenvironments might not show this consistency. Thus, to the degree possible and appropriate, paleoecological investigators should test the effects of these data categorization decisions on a paleoecological signal, regardless of the analytical method employed.

Thesis (M.S.) Department of Geological Sciences. Base map: coordinates provided by the author on page 3.

Global climate change has often resulted in extinction events that can be quantitatively measured by taxonomic loss but are more difficult to assess in terms of ecological restructuring. We use a commonly applied ecological tool, rank-abundance curves (RACs), to evaluate the ecological response of benthic foraminiferal and ostracode communities to the Paleocene-Eocene thermal maximum, which may be seen as an analog for current and future global warming. RACs are proxies for community structure, and therefore changes in the shape of RACs allow inferences to be drawn about and quantification of ecological responses. Benthic foraminiferal communities became increasingly stressed during the Paleocene-Eocene thermal maximum, and community reorganization occurred before the taxonomically defined extinction horizon. In contrast, ostracode communities became less stressed during the same interval, reinforcing the idea that different groups of organisms respond differently to extinction events and global warming. The decoupling of ecologic impact from taxonomic impact during the Paleocene-Eocene thermal maximum reaffirms the fact that future climate change could have far-reaching effects on taxa and ecosystems and proves the importance of examining both the taxonomic and ecologic responses of communities during extinction events. Abundance

On the occasion of the 200th anniversary of the discovery of boron, we review the oceanic biogeochemistry of boron as well as suitable analytical techniques for its determination. This overview includes aspects of biogeochemistry including geochemical stable isotope variations, uptake, transport, storage, nutritional value, toxicity, and distribution within biological materials, providing a framework for discussion of the role of boron in marine organisms, which remains largely enigmatic.

Reconstructing the phylogeny and biogeography of the Caribbean land snail Cerion requires a robust stratigraphic and chronological framework. To this end, we have determined the stratigraphic succession on San Salvador, a Bahamian island with a rich fossil and modern Cerion fauna. A primary purpose of this paper is to independently verify this succession through whole-rock and Cerion aminostratigraphies and AMS C-14- based age models. Over 150 individual Cerion shells were age-ranked from 140 ka to modern using stratigraphic position and reverse-phase HPLC (RPC) amino acid racemization, which was sufficiently sensitive to resolve stratigraphic subunits within the Holocene and late Pleistocene. A secondary purpose of this paper is to assess broad changes in the gross morphology (height, width) of supersets of Cerion from age-ranked lots spanning this similar to 140 kyr chronostratigraphy. Through each of the three interglacial sequences (i.e., marine isotope stages 5e, 5a, and 1), between-sample trends in mean gross morphology often greatly exceed within-sample variances (+/- 1 sigma). Live-collected Cerion exhibit a range in gross morphology that nearly encompasses that of the entire fossil sequence. A trend of increasing gross shell size characterizes each of the interglacial phases, with a major step-decrease between marine isotope stages 5a and 1. While between-unit variation is often great in Cerion from SSI, within-unit variation appears unimodal through the record. (C) 2008 Elsevier B.V. All rights reserved.

The fundamental global climate shift from greenhouse to icehouse conditions during the Eocene-Oligocene transition (EOT) has been variously attributed to the development of oceanic gateways, perturbations in the global carbon cycle, and variations in orbital forcing. This global climate shift is marked by the first significant Cenozoic glaciation of Antarctica and is associated with a variety of faunal and floral changes in the marine and terrestrial realms. Establishing the tempo and mode of biotic changes through the EOT can provide insight into both its physico-chemical nature and biotic impact.