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Planktic foraminiferal biostratigraphic zonation schemes are critical for providing first-order relative age control in deep-sea sediments and provide the basis on which to interpret evolutionary dynamics through time. Over the previous decades, the majority of published biostratigraphic zonation schemes focused on the tropical regions of the world. The mid-latitude or temperate regions, especially of the northwest Pacific, have been understudied in terms of recording plankton occurrences. Lack of detailed biostratigraphic studies have largely left out this region from plankton evolutionary analyses, thus how this part of the world ocean, which is characterized by the Kuroshio Current Extension (KCE), may contribute to global plankton biodiversity is unknown. In this study, we present the first magnetostratigraphically-calibrated late Neogene to Quaternary (15.12–0 Ma) planktic foraminiferal zonation schemes from the northwest Pacific for three Ocean Drilling Program Leg 198 holes (1207A, 1208A, and 1209A) that span the KCE. We utilize previously published warm subtropical, cool subtropical, and temperate zonation schemes from the southwest Pacific, with modifications. We find examples of significant diachroneity among primary marker taxa used to construct biozones at the three northwest Pacific sites, which ranges from 0.075 to 2.29 million years. Comparison of our primary datum markers with those of the tropical planktic foraminiferal zonation scheme also reveal diachroneity on the scale of 0.022 to 4.8 million years. We have identified times of intense dissolution in the northwest Pacific, namely in the middle to late Miocene that likely contribute to the observed diachroneity of datums. This study highlights the need for regionally specific mid-latitude biostratigraphic zonation schemes, as diachronous datums and differing assemblages may be hallmarks of oceanic ecotones created by major boundary current systems. These data also provide a framework to characterize local plankton evolutionary dynamics and paleobiogeographic patterns in future studies. [ABSTRACT FROM AUTHOR]

Patterns of diversity in the modern planktic foraminifera indicate a latitudinal diversity gradient (LDG), which peaks in the mid-latitude regions. Plankton distributional patterns are oftenmost strongly associated with temperature and are expected to change in response to expanded tropical water masses. Defining the underlying causes of climatic and oceanographic processes, however, requires detailed, local-scale diversity curves and evolutionary metrics, as well as solid taxonomic concepts of planktic foraminifera, to test the oceanographic processes driving evolution of marine plankton. Currently, diversity estimates for the planktic foraminifera are mainly based on global datasets skewed towards tropical to subtropical sites and conducted at coarse resolutions that hamper investigations of evolutionary processes, especially for short-lived climate perturbations. Here, we present 10-kyr resolution diversity curves and 25-kyr resolution local first appearance and extirpation rates of planktic foraminifera for four Ocean Drilling Program sites that extend from the temperate northern edge of themodern-day position of the Kuroshio Current Extension (KCE) to the tropics. We provide an updated taxonomic review of late Neogene planktic foraminiferal species from within the influence of the KCE. These data allow for investigations of the western Pacific LDG and patterns of evolution through the late Neogene in response to tectonic and climate events. Our results indicate that a mid-latitude diversity peak has been prominent in the western Pacific since at least 12.1Ma, with highest diversity generally on the northern edge of the KCE. These data contradict previous studies indicating highest diversity is located ±20°, as our data reveal highest diversity for the planktic foraminifera at ±35° N likely due to strong seasonality. Development of the modern North Pacific gyre system due to closure of the Central American Seaway and constriction of the Indonesian Throughflow increased the LDG between the tropics and the northernmost site, likely in response to KCE intensification. Diversity was only slightly affected during the mid-PiacenzianWarm Period (~3.2-2.9Ma), with diversity gradients between the equatorial site and southernmost mid-latitude sites becoming similar, perhaps indicating a weaker thermal gradient developing in the northwest Pacific as the KCE and warmer waters were displaced northwards. With intensification of Northern Hemisphere glaciation came a decrease in diversity at the northernmost site, hypothesized to be caused by subtropical gyre constriction and southward displacement of subpolar surface waters. The beginning of the mid-Pleistocene transition marks an increase in diversity gradients, especially between the northernmost and tropical sites. A detailed taxonomic evaluation of planktic foraminiferal species has led to synonymization of what we consider regional morphological variants, as well as revised taxonomic concepts of key subtropical to temperate late Neogene planktic foraminifera. Scanning electron micrographs capture the morphological variability within a species concept for the first time in great detail for this part of the world ocean. These data and updated taxonomic concepts provide a framework for future studies to link evolutionary patterns with high-resolution geochemical and sedimentological data to further interpret localized drivers of diversification in the planktic foraminifera. [ABSTRACT FROM AUTHOR]

The Oligocene-Miocene Transition (OMT) is an important interval in Earth's history, with substantial changes in Antarctic ice volume and mean temperature. The OMTis complicated in paleoclimatology, chronostratigraphy, and terminology, and there is a need for additional sites outside of the tropic/subtropics or Atlantic Basin to better understand the cause(s) and consequences of theOMT.Ocean Drilling Program Hole 744A sits on the southern edge of the Kerguelen Plateau, and is thus a sensitive recorder of changes on Antarctica and in the Indian Ocean sector of the Southern Ocean. Previous stratigraphic studies have concluded that the Oligocene/Miocene boundary is contained within a short coring gap (1 m) between Cores 744A-11 and 12. A new benthic foraminiferal stable isotope curve is at odds with the existing age model for the upper ~0.5mof Core 12. Anumber of different explanations for age models are discussed, and we find there is only one plausible explanation for the chronostratigraphy through Core 12. We suggest therewas a short (~150-200 kyr) hiatus, encompassing the peak Mi-1 excursion, based on interpreted magnetostratigraphy. This hiatus has no obvious lithologic expression. [ABSTRACT FROM AUTHOR]

We investigated the Cretaceous-Paleogene (K/Pg) transition at the Galanderud section, northern Alborz (Iran) to identify the pattern of mass extinction of planktic foraminifera and to unravel the associated paleoenvironmental changes in a little-studied area of the eastern Tethys. We applied a high-resolution quantitative and multidisciplinary study based upon benthic and planktic foraminiferal assemblages, clay mineralogy, rock magnetic properties, stable isotopes, and geochemistry. In this section, the K/Pg boundary is marked by an abrupt change in lithology from marl to a clay boundary layer, a marked decrease in magnetic susceptibility, a negative 2.2‰ δ 13 C excursion, and a peak in iridium. In the uppermost Maastrichtian, foraminifera are well preserved and diversified suggesting a stable, mesotrophic environment. By contrast, the K/Pg boundary and basal Danian is marked by high values of epifaunal benthic morphogroups, low planktic diversity, and high percentages of opportunistic species ( Guembelitria cretacea and Cervisiella operculata ) suggesting highly stressed and variable conditions, partly due to the dramatic collapse of calcareous primary producers. Benthic foraminiferal assemblages indicate outer neritic-uppermost bathyal depths with slight bathymetric variations. The most peculiar and unique aspect of the Galanderud section is the occurrence of the three thin chalk layers interbedded within clays above the K/Pg boundary, each marked by positive shifts in δ 13 C and δ 18 O values, and consisting of >80% carbonate. We propose that the chalk/clay deposits in the basal Danian reflect changes in seawater chemistry and dynamic changes in circulation (upwelling) alternating with episodes of enhanced weathering and runoff. This section on the northern margin of eastern Tethys provides new clues about the pattern of the K/Pg mass extinction and the paleoenvironmental changes occurring during the biotic recovery phase. [ABSTRACT FROM AUTHOR]

Deoxygenation is a critical problem facing the ocean as the world warms, and has the potential to effect coastal upwelling zones, shelf areas influenced by high runoff and nutrification, and restricted and semi-restricted basins. The mechanisms that drive deoxygenation in these diverse environments are still not fully understood, in part because the modern record of redox change is short and anoxia is still relatively rare in the modern ocean. Here, we address this problem of scale by studying deoxygenation in the geologic past. We summarize decades of individual studies of benthic foraminifera to generate a record of bottom water oxygen change in the Cretaceous Western Interior Sea (WIS) of North America over ~ 13 myr (Cenomanian-Campanian), spanning two major sea level cycles. The WIS was prone to major changes in dissolved oxygen content throughout its long history, sometimes directly antiphase to trends in the global ocean. Presented as maps, our data show that bottom water oxygen within the WIS was controlled by a combination of water mass source and mixing moderated by sea level and basin restriction. Areas flooded by cool Boreal (northern-sourced) waters in the northern and western parts of the seaway were better oxygenated than the eastern and southern portions of the seaway, which were flooded by warmer Tethyan (southern-sourced) waters. Beyond east-west differences explained by water mass, the entire seaway was better oxygenated during periods of transgression, and more poorly oxygenated to anoxic during periods of peak transgression/highstand and regression. We suggest that this pattern was due to the formation and downwelling of Western Interior Intermediate Water by the mixing of Tethyan and Boreal waters. During transgressions, an increasing volume of these watermasses entered the seaway, mixed, and downwelled well‑oxygenated surface water to the seafloor. During late transgression/highstand, partial stratification and the encroachment of low oxygen waters from the open ocean caused dissolved oxygen levels to drop at the seafloor, but continued downwelling prevented anoxia. During the subsequent regression, a decline in the volume of outside watermasses entering the seaway caused a reduction in mixing and weakened downwelling which led to stratification and seafloor anoxia. As a model for other semi-restricted basins, the trends observed in the WIS show that local changes in relative sea level, mixing, and circulation are critical in controlling oceanic deoxygenation in these environments, in clear contrast to continental margins impinged by oxygen minimum zones, like the contemporaneous Demerara Rise in the southern Caribbean. Although the WIS is larger than most semi-restricted basins, it is characterized by quasi-estuarine circulation driving the interaction of normal marine and brackish watermasses, and thus serves a model for similar shallow epicontinental basins of any size. Understanding how these processes vary in different environments is key to predicting susceptibility of regional water bodies to deoxygenation in the future with a warming world. [ABSTRACT FROM AUTHOR]

Biotic perturbations and changes in ocean circulation during the Maastrichtian stage of the latest Cretaceous raise questions about whether the biosphere was preconditioned for the end-Cretaceous mass extinction of calcareous plankton. A brief acme of inoceramid clams at ~ 71 Ma on Shatsky Rise in the tropical North Pacific was followed by their extinction during the “mid-Maastrichtian event” at 70.1 Ma associated with an abrupt warming of deep waters. This was later followed by an interval of intense dissolution beginning ~ 67.8 Ma at ODP Site 1209 (2387 m). The late Maastrichtian dissolution interval was initially gradual, and is characterized by a low planktic/benthic (P/B) ratio, highly fragmented planktic foraminifera, mostly an absence of larger taxa, low abundances of smaller taxa, extremely low planktic foraminiferal numbers, and low planktic foraminiferal and nannofossil species richness. A partial recovery in carbonate preservation and calcareous plankton simple diversity began ~ 250 kyr prior to the K/Pg boundary associated with the incursion of a younger (more enriched δ 13 C) deep water mass, although total abundances of planktic foraminifera in the sediment remained a tiny fraction of their earlier Maastrichtian values. A second, brief dissolution event occurred ~ 200 kyr before the boundary evidenced by renewed increase in planktic fragmentation, but without a decrease in P/B ratio. Our data show that changing deep water masses, coupled with reduced productivity and associated decrease in pelagic carbonate flux was responsible for the first ~ 1.6-Myr dissolution interval, while Deccan Traps volcanism (?) may have caused surface ocean acidification ~ 200 kyr prior to the K/Pg mass extinction event. [ABSTRACT FROM AUTHOR]

Two sites near the eastern margin of the Cretaceous Western Interior Sea (WIS) were investigated. The section at Cuba, Kansas (CK) is ~ 630 km east of the GSSP for the Cenomanian/Turonian boundary at Rock Canyon, Colorado (RC), and the section near Sioux City, Iowa (SCI) is ~ 315 km northeast of the Cuba site. Surprisingly, planktic foraminifera dominate all the studied samples despite the relative proximity of the sites to the paleo-shoreline and presumed neritic water depths. Such dominance suggests inhospitable benthic environments, and benthic foraminiferal assemblages indicate that seafloor oxygen in the WIS decreased eastward. Therefore, the hypothesis of an influx of freshwater into the WIS from the western margin forming a fresh water cap that diminished eastward is not supported. Benthic foraminifera are scarce in most studied samples and species diversity is low. In the CK section, diversity and abundance increase abruptly in the uppermost Cenomanian Benthonic Zone at the initiation of the δ 13 C org positive excursion marking the onset of Oceanic Anoxic Event (OAE 2). In the SCI section, however, the Benthonic Zone is recognized only by presence of Nodosaria bighornensis that has a stratigraphic range restricted to this interval; other benthic taxa are very rare or absent. The favorable conditions of the Benthonic Zone were short-lived. While relatively diverse planktic foraminiferal assemblages, including keeled species, characterize the initial δ 13 C excursion at the CK site, dwarfed specimens of Heterohelix and Hedbergella dominate the assemblages at the more proximal Sioux City site. Furthermore, most of the biostratigraphic events recognized in the basin center RC section can be traced into the CK section, but not into the SCI section, including the Rotalipora spp. and Globigerinelloides bentonensis extinctions, the Heterohelix shift event, and the brief benthic recovery event. Correlation between eastern WIS sites shows that the SCI section is thicker, suggesting a major sediment source to the east. This may explain the inhospitable benthic conditions and development of a ‘dead zone’ (seasonal hypoxia) analogous to the modern shelf of the northern Gulf of Mexico proximal to active discharge of the Mississippi River. Development of estuarine circulation in the WIS provided the eastern part of the basin with input of calcareous plankton from the south including planktic foraminifera. Foraminiferal assemblages, total organic carbon (TOC), and δ 13 C data of the studied sections suggest a two-fold history of Greenhorn transgression and OAE 2 development. The initial phase is a global signal characterized by a positive δ 13 C excursion, low TOC values, and high foraminiferal species diversity. The second phase is characterized by overprinting by local conditions in the WIS, including high fluvial input, relatively high TOC values, and low foraminiferal species diversity. These findings suggest that the eastern margin records unique depositional and biotic environments further revealing the dynamic and complex nature of the WIS and its sedimentary cycles. [ABSTRACT FROM AUTHOR]

Foraminifera from the Cenomanian-Turonian Dakota Formation, Straight Cliffs Formation, Iron Springs Formation, and Tropic Shale of southwest Utah are described and illustrated in detail. The assemblage comprises 37 taxa including 27 agglutinated species and only nine calcareous taxa. The associations of the foraminifera can be summarized on the basis of their distributions relative to geologic age and formation. The lowermost units of theDakota Formation in southwestUtah and Coal Mine Mesa Arizona are characterized by a Trochammina rutherfordi mellariolium-Verneuilinoides perplexus association. The uppermost strata of the Dakota Formation and lower Tropic Shale (upper Cenomanian) are characterized by a Trochamminoides apricarius-Haplophragmium arenatum association. Strata assigned to the lower-to middle Turonian Iron Springs and Straight Cliffs Formation are highly variable with respect to foraminiferal distributions. Lower Turonian deposits fromthe Tropic Shale, however, contain an association of Reophax inordinata and Ammomargulina lorangerae. The temporal and spatial variability of the foraminifera are attributed to transgressive-regressive facies shifts during deposition of the Greenhorn Marine Cycle. We recognize four paleoecological associations of agglutinated foraminifiera that include: (1) a marsh assemblage dominated by Trochammina and Miliammina; (2) a central estuary assemblage dominated by Ammobaculites and Trochammina; (3) a distal estuary assemblage dominated by Verneuilinoides, Textularia, andTrochamminoides; and (4) a shelf assemblage dominated by Haplophragmium and Reophax. [ABSTRACT FROM AUTHOR]

Abstract: We document the waxing and waning of a “proto-warm pool” in the western equatorial Pacific (WEP) based on a study of multi-species planktic foraminiferal isotope ratios and census data spanning the 13.2–5.8 Ma interval at ODP Site 806. We hypothesize that the presence or absence of a proto-warm pool in the WEP, caused by the progressive tectonic constriction of the Indonesian Seaway and modulated by sea level fluctuations, created El Niño/La Niña-like alternations of hydrographic conditions across the equatorial Pacific during the late Miocene. This hypothesis is supported by the general antithetical relationship observed between carbonate productivity and preservation in the western and eastern equatorial Pacific, which we propose is caused by these alternating ocean–climate states. Warming of thermocline and surface waters, as well as a major change in planktic foraminferal assemblages record a two-step phase of proto-warm pool development ~11.6–10 Ma, which coincides with Miocene isotope events Mi5 and Mi6, and sea-level low stands. We suggest that these changes in the biota and structure of the upper water column in the WEP mark the initiation of a more modern equatorial current system, including the development of the Equatorial Undercurrent (EUC), as La Niña-like conditions became established across the tropical Pacific. This situation sustained carbonate and silica productivity in the eastern equatorial Pacific (EEP) at a time when carbonate preservation sharply declined in the Caribbean. Proto-warm pool weakening after ~10 Ma may have contributed to the nadir of a similar “carbonate crash” in the EEP. Cooling of the thermocline and increased abundances of thermocline taxa herald the decay of the proto-warm pool and higher productivity in the WEP, particularly ~9.0–8.8 Ma coincident with a major perturbation in tropical nannofossil assemblages. We suggest that this interval of increased productivity records El Niño-like conditions across the tropical Pacific and the initial phase of the widespread “biogenic bloom”. Resurgence of a later proto-warm pool in the WEP ~6.5–6.1 Ma may have spurred renewed La Niña-like conditions, which contributed to a strong late phase of the “biogenic bloom” in the EEP. [Copyright &y& Elsevier]

Oceanic Anoxic Event 2 (OAE2; ~94.5 Ma) occurred in the latest Cenomanian and represents a perturbation to the global carbon cycle. The event is geochemically recorded in shales and limestones of the Western Interior Basin of North America and is additionally marked by foraminiferal bio-events (e.g., turnovers, extinctions). These bio-events are attributed to changing paleoceanographic conditions and circulation patterns in the Western Interior Seaway related to the onset of OAE2. Here we investigate the paleoenvironment near the southwestern edge of the seaway during OAE2 by integrating microfossil and geochemical records from the lower beds of the Tokay Tongue (Mancos Shale) at Carthage, New Mexico, USA. We demonstrate that this locality represents an expanded section of OAE2 based on temporal constraints from carbon isotope chemostratigraphy and the occurrence of regional marker ash-fall deposits (bentonites), limestones and other carbonate-rich beds. Prior to the onset of OAE2, a unique assemblage of benthic foraminiferal morphologies suggests the presence of a distinct water mass in the southwestern part of the seaway compared to coeval neritic and distal sites. Microfossil assemblages record the Benthonic Zone, a typical OAE2 bio-event, with some distinctions. The event is still identifiable and thereby useful in marking the earliest stages of OAE2. Early in OAE2, calcareous nannofossil and foraminiferal assemblages indicate intervals of high productivity. The dominance of biserial planktic foraminifera (Planoheterohelix spp.) suggests the development of photic zone euxinia with intensification of OAE2. During OAE2, epifaunal trochospiral benthic foraminifera (Gavelinella dakotaensis) suggest intervals of improved conditions related to food availability and seafloor ventilation. Later, as increased surface water productivity and subsequent food availability prevailed at the seafloor through the end of the OAE2 interval, benthic foraminifera were abundant and assemblages were dominated by infaunal, low oxygen tolerant species (Neobulimina albertensis), suggesting prevailing dysoxia. We attribute differences in the expression of bio-events and foraminiferal community composition at Carthage to the influence of freshwater runoff from the western margin that drove high-productivity conditions throughout OAE2. [ABSTRACT FROM AUTHOR]

Planktic foraminifera are commonly used for first-order age control in deep-sea sediments from low-latitude regions based on a robust tropical–subtropical zonation scheme. Although multiple Neogene planktic foraminiferal biostratigraphic zonations for mid-latitude regions exist, quantification of diachroneity for the species used as datums to test paleobiogeographic patterns of origination and dispersal is lacking. Here, we update the age models for seven southwest-Pacific deep-sea sites using calcareous nannofossil and bolboform biostratigraphy and magnetostratigraphy, and use 11 sites between 37.9° N and 40.6° S in the western Pacific to correlate existing planktic foraminiferal biozonations and quantify the diachroneity of species used as datums. For the first time, northwest and southwest Pacific biozones are correlated and compared to the global tropical planktic foraminiferal biozonation. We find a high degree of diachroneity in the western Pacific, within and between the northwest and southwest regions, and between the western Pacific and the tropical zonation. Importantly, some datums that are found to be diachronous between regions have reduced diachroneity within regions. Much work remains to refine regional planktic foraminiferal biozonations and more fully understand diachroneity between the tropics and mid-latitudes. This study indicates that diachroneity is the rule for Late Neogene planktic foraminifera, rather than the exception, in mid-latitude regions. [ABSTRACT FROM AUTHOR]

Oceanic Anoxic Event 2 (OAE2) at the Cenomanian/Turonian Boundary (CTB: 93.9Ma) involved the global deposition of organic carbon-rich sediments, a distinctive positive shift in carbon isotope values, and significant species turnover, including changes in calcareous nannofossil assemblages. While it is thought that volcanismtriggered organic C-rich sediment deposition during OAE2, it is unclear whether enhanced productivity, increased stratification, of some combination of the two increased organicmatter preservation. Calcareous nannofossil assemblages have the potential to qualitatively assess changes in ocean nutrient and temperature conditions to disentangle such ecological dynamics during OAE2. Here we study an expanded section of the Tropic Shale in a drill core in southern Utah near thewestern margin of theWestern Interior Seaway (WIS) to understand how circulation changed during the event and how this may have influenced primary productivity and organic carbon burial. Relative abundance data of well-preserved nannoplankton are complemented with measurements of trace metal, and organic carbon and carbonate concentrations to determine changes in temperature and water column structure, as well as controls on surface water productivity. Detailed statistical analysis helps refine species paleoecologies combined with information from planktic and benthic foraminiferal assemblages and organic biomarkers. Changes in calcareous nannofossil assemblages indicate that near the start of OAE2 the westernWIS surface ocean actually cooled for a short time. Following this, surface waters became warmer and more stratified as a Tethyan water mass invaded the seaway. Assemblages suggest that warmth persisted for much of the OAE2 interval, while stratification waxed and waned. The local seaway cooled near the end of OAE2 as Boreal water masses streamed along the western margin. Variations, including the decrease in the abundance of Biscutum constans and short-lived peaks in the abundance of Eprolithus spp. are super regional or possibly global in extent. There is no correlation between calcareous nannofossil assemblages and trace metal concentrations, suggesting they were unaffected by volcanism-related nutrient inputs. Assemblages support other data that suggest increased stratification influenced organic carbon burial in theWestern Interior Seaway, and possibly elsewhere, during OAE2. [ABSTRACT FROM AUTHOR]

In this article the author discusses the similarity of the benthic Bolivina variabilis and planktic Streptochilus globigerus. He claims that the plankton is one particular species of foraminifer, which is a single-celled, testate protist. He explains that their profound similarity has provided the fact that plaplanktic lineages may have evolved multiple times from benthic ancestors since Jurassic time.

Site U1396 was piston cored as a part of Integrated Ocean Drilling Project Expedition 340 to establish a long record for Lesser Antilles volcanism. A ~150 m sediment succession was recovered from three holes on a bathymetric high ~33 km southwest of Montserrat. Aseries of shipboard and newly-generated chronostratigraphic tools (biostratigraphy, magnetostratigraphy, astrochronology, and stable isotope chemostratigraphy) were employed to generate an integrated age model. Two possible chronostratigraphic interpretations for the Brunhes chron are presented, with hypotheses to explain the discrepancies seen between this study and Wall-Palmer et al. (2014). The recentWade et al. (2011) planktic foraminiferal biostratigraphic calibration is tested, revealing good agreement between primary datums observed at Site U1396 and calibrated ages, but significant mismatches for some secondary datums. Sedimentation rates are calculated, both including and excluding the contribution of discrete volcanic sediment layers within the succession. Rates are found to be 'pulsed' or highly variable within the Pliocene interval, declining through the 1.5-2.4 Ma interval, and then lower through the Pleistocene. Different explanations for the trends in the sedimentation rates are discussed, including orbitally-forced biogenic production spikes, elevated contributions of cryptotephra (dispersed ash), and changes in bottom water sources and flow rates with increased winnowing in the area of Site U1396 into the Pleistocene. [ABSTRACT FROM AUTHOR]

The Upper Cretaceous of central Texas is dominated by a broad, shallow carbonate platform called the Comanche Platform that occupies an important gateway between the epeiric Western Interior Seaway (WIS) of North America to the open-marine Gulf of Mexico/Tethys. We investigated the Cenomanian–Turonian Eagle Ford Shale on and adjacent to the Comanche Platform to determine whether the Eagle Ford Shale has an affinity with the Western Interior, and if so, determine where the transition from Western Interior to open ocean is located. We were also interested in the relationship, if any, between the organic-rich facies of the Eagle Ford and Oceanic Anoxic Event 2 (OAE2). Our work is based on quantitative foraminiferal population counts and associated sedimentary particles (including inoceramid prisms, sand, glauconite, and pyrite grains), calcareous nannofossil assemblages, carbon isotopes, and total organic carbon (TOC) from three sites across a range of paleowater depths: an outcrop in Lozier Canyon in Terrell County, west of Langtry, TX, an outcrop at Bouldin Creek outside of Austin, TX, and Swift Energy's Fasken A #1H core in Webb County, TX. The highest TOC in the Eagle Ford occurs before the onset of OAE2 (6% at Lozier Canyon, 7% at both Bouldin Creek and the Fasken Core) and then declines steadily through the rest of the section (except for a small increase at the end of OAE2 at Lozier and a fairly large post-OAE2 increase at Bouldin Creek). Nannofossil paleoproductivity indicators (% Zeugrhabdotus and % Biscutum ) track TOC at Bouldin Creek and in the Fasken Core and display similar trends to those observed in the Western Interior Seaway to the north. Benthic foraminiferal abundances increase as TOC decreases and the lithology shifts from laminated black shale to bioturbated light gray shale; low-oxygen-tolerant infaunal Neobulimina spp. appear first and gradually increase in abundance; epifaunal benthics appear soon after. This oxygenation trend continues through the OAE2 interval and the upper Eagle Ford contains a diverse epi- and infaunal benthic foraminiferal assemblage and macrofossil assemblage. This trend of decreasing TOC and nannofossil paleoproductivity indicators coupled with increasing benthic foraminiferal abundance and diversity (and seafloor oxygenation) corresponds to rising sea level. Based on foraminiferal and nannofossil events, TOC trends, and changes in lithology, both platform sites have a strong affinity with the Western Interior, with Lozier Canyon being the most similar; the Fasken Core bears all the characteristics of an open ocean site, except for the fact that peak TOC occurs before OAE2. This suggests that the oceanographic boundary between WIS and Tethys can be placed on the edge of the Comanche Platform. Productivity was likely driven by bathymetry-induced upwelling caused by restriction between the WIS and Tethys during times of low sea level; as sea level rose, upwelling diminished and productivity decreased. This explains why the Fasken Core, adjacent to the platform margin and in the center of this upwelling zone, displays the same TOC trends as the platform sites. Organic carbon content in the seaway was controlled by stratification and enhanced preservation, but this was also reduced by rising sea level, which is why the two areas show parallel trends. [ABSTRACT FROM AUTHOR]

New ages of rocks in the San Juan Islands, northwest Washington, significantly change our understanding of the evolution of the San Juan Islands thrust system. Re-examination of foraminifera-bearing mudstones at Richardson on Lopez Island indicates a late Aptian (112–115 Ma), not late Albian (100 Ma) age as currently presented in the literature. The age brackets of thrusting, marked by these pre-thrusting mudstones and 84-Ma post-thrusting sedimentary rocks, span a much longer period than previously thought, diminishing controls on rates of displacement in the thrust system and the timing of regional deformation in western Washington. New 40Ar/39Ar plateau ages of phengite in blueschist-facies meta-volcanic rock, also at Richardson, are 124 ± 0.7 Ma (2σ, late Barremian). These blueschist-facies volcanic rocks are in fault contact with the fossiliferous mudstones. Therefore, the blueschist-facies metamorphism at Richardson, previously inferred to be associated with the thrusting, now appears to have occurred prior to thrusting. Further, the Ar ages demonstrate that blueschist-facies fabric formed earlier than the thrust event and is therefore not directly useful in analyzing the thrusting kinematics. The Richardson 40Ar/39Ar age is similar to isotopic ages found in the eastern San Juan Islands and in the Shuksan blueschist terrane in the northwest Cascades, and thus fits into an emerging regional age pattern of blueschist-facies metamorphism during Late Jurassic – Early Cretaceous (up to Barremian) but not late Albian – Cenomanian. If this pattern is more broadly confirmed for the San Juan Islands, all the blueschist-facies metamorphism can be regarded as having formed in subduction zones elsewhere along the continental margin rather than in the anomalous setting of an on-land thrust system, as in the San Juan Islands. [ABSTRACT FROM AUTHOR]

The ostracode genus Fossocytheridea Swain and Brown 1964 is emended herein. A summary of the diagnostic characters include: (1) a median sulcus, (2) a tripartite antimerodont hinge with distinct heart-shaped terminal elements, (3) distinct sexual dimorphism; (4) a narrow inner margin that has 20-28 straight radial pore canals, and (5) variability in the external carapace (pore shape, pore density, and patterns of reticulation) that bears close resemblance to Cyprideis. Two new species are described from southwest Utah (U.S.A): Fossocytheridea mosbyense sp. nov. and Fossocytheridea kirklandi sp. nov. and 21 taxa previously assigned to Fabanella, Sarlatina, Ovocytheridea, Dolocytheridea, Antibythocypris, and Cytheridea are assigned to the emended genus. Fossocytheridea resembles Cyprideis with respect to both shell morphology and ecology since it occurs in association with euryhaline biota in coal-bearing strata. Expansion of marginal marine environments during the highest sea level of the Mesozoic saw Fossocytheridea successfully migrate and dominate restricted coastal environments. Since this expansion, the prominent characters of Fossocytheridea have been preserved in descendent genera belonging to the tribe Cyprideidini Kollmann 1960 that are preserved to this day in Cyprideis. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Focuses on the Cretaceous-Tertiary (K-T) boundary cocktail, suggesting that Chicxulub impact triggers margin collapse and extensive sediment gravity flows. Reference to the basis of calcerous nannofossil biostratigraphy; Details on microfossil reworking; Relationship of the K-T boundary cocktail to the Chicxulum impact.

Cretaceous oceanic anoxic events (OAEs) were periods of geologically short (<1 million years) global change characterized by elevated temperatures, changes in ocean biogeochemistry, ecological turnover, and the global-scale deposition of black shales. After decades of OAE research, the intensity and spatiotemporal heterogeneity of ocean anoxia and its direct effects on marine ecology remain areas of active study. We present high-resolution organic geochemical and foraminiferal records from the western margin of the Western Interior Seaway (WIS) during the Cenomanian-Turonian Oceanic Anoxic Event 2 (OAE2, ~94 Ma) that indicate reorganization of a neritic ecosystem in response to sea-level rise, and dynamic changes in redox conditions that were likely driven by enhanced marine productivity. A significant transgression prior to OAE2 decreased terrestrial organic matter input and led to enhanced productivity, anoxic bottom waters and sediments, and episodic photic zone euxinia. During the middle of OAE2, further enhanced productivity led to the " Heterohelix shift" in planktic foraminifera, the " Gavelinella acme" in benthic foraminifera, and deoxygenation in sediments, bottom waters, and the upper water column. The combined use of high-temporal resolution algal, bacterial, and terrestrial biomarkers, in addition to foraminiferal records, demonstrates the sensitivity of marine autotrophic and heterotrophic communities to sea-level rise and variable water column oxygenation in marginal marine settings during hyperthermal events. Furthermore, our results reveal the temporal and spatial heterogeneity of anoxia during OAE2 in the WIS. This study highlights widespread shallow marine feedbacks during global change that may affect neritic ecosystems under future warming scenarios. • Marine productivity and anoxia/euxinia was enhanced by transgressions. • Algal, bacterial, and foraminiferal assemblages changed with anoxia/euxinia. • First direct comparison of foraminiferal and biomarker records during OAE2 in WIS. [ABSTRACT FROM AUTHOR]

Proximal marine strata of the North American Western Interior Basin (WIB) preserve a rich record of biotic turnover during Oceanic Anoxic Event 2 (OAE2; ca. 94 Ma), a pronounced Late Cretaceous carbon cycle perturbation interpreted to reflect global warming, widespread hypoxia, and possible ocean acidification. To develop a more robust synthesis of paleobiologic and geochemical data sets spanning this Earth-life transition, we drilled the 131 m Smoky Hollow #1 Core (SH#1), on the Kaiparowits Plateau of southern Utah, USA, recovering the Cenomanian-Turonian Boundary (CTB) interval in the Tropic Shale Formation. A 17.5 m positive excursion in high-resolution bulk carbon isotope chemostratigraphy (δ13Corg) of SH#1 characterizes the most expanded OAE2 record recovered from the mid-latitudes of the WIB. Depleted values in a paired carbonate carbon isotope (δ13Ccarb) chemostratigraphy cyclically punctuate the OAE2 excursion. These depletions correspond to intervals in the core with a higher degree of carbonate diagenesis and correlate well to an existing sequence stratigraphic framework of flooding surfaces in the shoreface facies of the Markagunt Plateau (~100 km west). We detect statistically significant evidence for astronomical cycles in the δ13Ccarb data set, imparted by diagenesis at flooding surfaces, and develop a floating astronomical time scale (ATS) for the study interval. Stable eccentricity cycles (405 k.y.) align with stratigraphic sequences and associated trends in sedimentation rate, and short eccentricity cycles (~100 k.y.) pace nested parasequences. These results confirm an astronomical signal and, therefore, climatic forcing of relative sea level during OAE2 in the WIB. Furthermore, cross-basin correlation of the ATS and expanded δ13C chemostratigraphy of SH#1 suggests that these transgressive-regressive parasequences modulated siliciclastic sediment delivery in the seaway and contributed to deposition of prominent rhythmically bedded CTB units across the WIB, including the Bridge Creek Limestone. The presented approach to analysis of these proximal offshore siliciclastic facies links early diagenetic influences on chemostratigraphy to astronomically modulated sequence stratigraphic horizons, and helps to resolve rates of paleobiologic and paleoenvironmental change during a significant Mesozoic carbon cycle perturbation. [ABSTRACT FROM AUTHOR]

Abstract: Eustasy is a key parameter to understand sedimentary sequences on continental margins and to reconstruct continental ice volume in the Cenozoic, but timing and magnitude of global sea level changes remain controversial, especially for the Miocene Epoch. We analyzed sediment cores recovered from the Marion Plateau, offshore northeastern Australia, during Ocean Drilling Program (ODP) Leg 194 to define the mechanisms and timing of sequence formation on mixed carbonate-siliciclastic margins, and to estimate the amplitude of Miocene eustatic adjustments. We identified sequence boundaries on seismic reflection lines, significantly revised the existing biostratigraphic age models, and investigated the sedimentary response to sea-level changes across the Marion Plateau. We subdivided the Miocene sediments into three sequence sets comprising a set of prograding clinoforms, a muddy prograding carbonate ramp evolving into an aggrading platform, and a lowstand ramp evolving into a backstepping ramp. We recognized eight individual sequences dated at 18.0Ma, 17.2Ma, 16.5Ma, 15.4Ma, 14.7Ma, 13.9Ma, 13.0Ma, and 11.9Ma. We demonstrate that sequences on the Marion Plateau are controlled by glacio-eustasy since sequence boundaries are marked by increases in δ18O (deep-sea Miocene isotope events Mi1b, Mbi-3, Mi2, Mi2a, Mi3a, Mi3, Mi4, and Mi5, respectively), which reflects increased ice volume primarily on Antarctica. Our backstripping estimates suggest that sea-level fell by 26–28m at 16.5Ma, 26–29m at 15.4Ma, 29–38m at 14.7Ma, and 53–81m at 13.9Ma. Combining backstripping with δ18O estimates yields sea-level fall amplitudes of 27±1m at 16.5Ma, 27±1m at 15.4Ma, 33±3m at 14.7Ma, and 59±6m at 13.9Ma. We use a similar approach to estimate eustatic rises of 19±1m between 16.5 and 15.4Ma, 23±3m between 15.4 and 14.7Ma, and 33±3m between 14.7 and 13.9Ma. These estimates can be combined into a eustatic curve that suggests that sea-level fell by 53–69m between 16.5 and 13.9Ma. This implies that at least 90% of the East Antarctic Icesheet was formed during the middle Miocene. The new independent amplitude estimates are crucial as the Miocene is the geologic Epoch for which the New Jersey margin sea-level record is poorly constrained. [Copyright &y& Elsevier]

About 34 million years ago, Earth's climate shifted from a relatively ice-free world to one with glacial conditions on Antarctica characterized by substantial ice sheets. How Earth's temperature changed during this climate transition remains poorly understood, and evidence for Northern Hemisphere polar ice is controversial. Here, we report proxy records of sea surface temperatures from multiple ocean localities and show that the high-latitude temperature decrease was substantial and heterogeneous. High-latitude (45 degrees to 70 degrees in both hemispheres) temperatures before the climate transition were ∼20°C and cooled an average of ∼5°C. Our results, combined with ocean and ice-sheet model simulations and benthic oxygen isotope records, indicate that Northern Hemisphere glaciation was not required to accommodate the magnitude of continental ice growth during this time. [ABSTRACT FROM AUTHOR]

We present enigmatic toroidal carbonate concretions retrieved from 700 m water depth from two sites in the upper plateau of the Rio Grande Rise. The concretions have a diameter of ~15 cm and a central hole of ~5 cm, and were observed on top of loose bioclastic sand over an area of ~30 m2 at 0.5–1.5 m from one another. They consist of brown, porous, bioclastic grainstone, lacking internal structures. Grains consist of sand (< 3% coarse, 30% medium, 35% fine, 25% very fine), composed mainly by planktonic foraminiferal tests, and < 10% lime mud. The observed foraminiferal species indicate initial deposition of the sand in an open ocean setting. Biostratigraphy suggests an age no older than Pleistocene. Petrographic thin sections and SEM reveal that the fossiliferous grainstone contains intraclastic micritic cement and isopachous rim cement made of bladed magnesian calcite. δ18O values range from +1.5 to +3.3‰ (V-PDB) and increase with the degree of cementation, while δ13C ranges from +0.5 to +2.3‰ irrespective of cementation. The cementation of the grainstones is likely to have taken place in the marine phreatic environment. Carbonate precipitation induced by methane oxidation or (subaerial) meteoric diagenesis are ruled out based on both cement fabric and isotopic composition. Plausible causes for the toroidal shape of these structures could be: 1) sediment excavation by organisms, or 2) cementation within biofilms around burrows, followed by selective seafloor erosion. However, unveiling the actual formation mechanisms warrants further investigation. • First report of toroidal carbonate concretions from the Rio Grande Rise. • The concretions consist of grainstone dominated by planktic foraminifera. • Biostratigraphy suggests an age no older than Pleistocene. • Cement fabric and stable isotopes suggest formation by marine phreatic diagenesis. • No contribution of methane-derived carbonate is found. [ABSTRACT FROM AUTHOR]