Astronomical time scale for Paleocene and early Eocene sediments

The astronomical-tuned time scale is rapidly extended into the Paleogene but, due to the existence of an Eocene gap, different tuning options had to be presented for the Paleocene. These options differ both in number and tuning of ~405-kyr eccentricity related cycles and are only partially consistent with recalculated 40Ar/39Ar constraints for the Cretaceous/Paleogene (K/Pg) and Paleocene/Eocene (P/E) boundaries. In this paper, we evaluate the cyclostratigraphic interpretation of records from ODP Leg 198 and 208 sites, and the Zumaia section to solve the problem of the different tuning options. We found that the interval between the K/Pg boundary and the early Late Paleocene biotic event (ELPE) comprises 17 instead of 16 * ~405-kyr eccentricity related cycles as previously proposed, while the entire Paleocene contains 25 * ~405-kyr cycles. Starting from 40Ar/39Ar age constraints for the K/Pg boundary, a new tuning to 405-kyr eccentricity is presented for the Paleocene and earliest Eocene, which results in ages of ~66.0 and ~ 56.0 Ma for the K/Pg and P/E boundaries, respectively. This tuning introduces considerable differences in age for a number of nannofossil events at ODP Sites 1209 and 1262 in the interval between 61 and 63 Ma, but eliminates large and abrupt changes in the seafloor spreading rate. The tuning seems further consistent with recalculated 40Ar/39Ar ages for ash layer -17 of early Eocene age. However, despite this apparent consistency with existing radio-isotopic constraints, an alternative 405-kyr younger or, less likely, older tuning cannot be excluded at this stage.

Late Oligocene through early Pleistocene calcareous nannofossils of ODP Leg 115 holes

The chronostratigraphy, the calcareous nannofossil biochronology, and the biostratigraphy of the Miocene and Pliocene sediments retrieved during Leg 115 in the equatorial western Indian Ocean are presented and discussed. Most of the zonal boundaries of the standard 1971 zonation of Martini and the 1973 zonation of Bukry are easily recognized in these low-latitude sediments. We also comment on the secondary events that are proposed in the literature to improve the biostratigraphic resolution provided by the standard zonations. The study of calcareous nannofossil biostratigraphy and taphonomy of sequences from the Northern Mascarene Plateau area, which was drilled to investigate the Neogene history of carbonate flux and dissolution, indicate that the accumulation of carbonates in this area results from a complex interplay among carbonate bioproductivity, carbonate removal by chemical dissolution and mechanical erosion, and carbonate addition by mass and current transport. In spite of these drawbacks, major changes and trends in carbonate accumulation can be recognized, most of which, if not all, correlate with major steps in the evolution of the Neogene climatic system.

Construction of a precise early Eocene orbital cyclostratigraphy for DSDP Site 80-550 from the Goban Spur, North Atlantic

We constructed a precise early Eocene orbital cyclostratigraphy for DSDP Site 550 (Leg 80, Goban Spur, North Atlantic) utilizing precession related cycles as represented in a high resolution X-Ray Fluorescence based Barium core log. Based on counting of those cycles, we constrain the exact timing of two volcanic ash layers in Site 550 which correlate to ashes +19 and -17 of the Fur Formation in Denmark. The ashes, relative to the onset of the Paleocene/Eocene Thermal Maximum (PETM), are offset by 862 kyr and 672 kyr, respectively. When combined with published absolute ages for ash -17, the absolute age for the onset of the PETM is consistent with astronomically calibrated ages. Using the current absolute age of 28.02 Ma for the Fish Canyon Tuff (FCT) standard for calibrating the absolute age of ash -17 is consistent with tuning option 2 in the astronomically calibrated Paleocene time scale of Westerhold et al. (2008) [Westerhold, T., Röhl, U., Raffi, I., Fornaciari, E., Monechi, S., Reale, V., Bowles, J., and Evans, H.F., 2008, Astronomical calibration of the Paleocene time: Palaeogeography, Palaeoclimatology, Palaeoecology, v. 257, p. 377-403]. Using the recently recalibrated absolute age of 28.201 Ma for the FCT standard is consistent with tuning option 3 in the astronomically calibrated Paleocene time scale. The new results do not support the existence of any additional 405-kyr cycle in the early Paleocene astronomically tuned time scale.

Late Eocene to Early Oligocene magnetostratigraphic chron boundaries of ODP Hole 119-744A (Table 1)

The earliest Oligocene (~33.5 Ma) is marked by a major step in the long-term transition from an ice-free to glaciated world. The transition, characterized by both cooling and ice-sheet growth, triggered a transient but extreme glacial period designated Oi-1. High-resolution isotope records suggest that Oi-1 lasted for roughly 400,000 yr (the duration of magnetochron 13N) before partially abating, and that it was accompanied by an ocean-wide carbon isotope anomaly of 0.75?. One hypothesis relates the carbon isotope anomaly to enhanced export production brought about by climate-induced intensification of wind stress and upwelling, particularly in the Southern Ocean. To understand how this climatic event affected export production in the Southern Ocean, biogenic silica (opal) and carbonate accumulation rates were computed for the sub-polar Indian Ocean using deep-sea cores from ODP Site 744, Kerguelen Plateau. Our findings suggest that net productivity in this region increased by several fold in response to the Oi-1 glaciation. In addition, calcareous primary producers dominant in the Late Eocene were partially replaced by opaline organisms suggesting a trend toward seasonally greater surface divergence and upwelling in this sector of the Southern Ocean. We attribute these changes to intensification of atmospheric=oceanic circulation brought about by high-latitude cooling and the appearance of a full-scale continental ice-sheet on East Antarctica. Higher terrigenous sediment accumulation rates support the idea that wind-induced changes in regional productivity were augmented by an increased supply of glacial dust and debris that provided limiting micro-nutrients (e.g., iron-rich dust particles). We speculate that the rapid changes in biogenic sediment accumulation in the Southern Ocean and other upwelling-dominated regions contributed to the ocean-wide positive carbon isotope anomaly by temporarily increasing the burial rate of organic carbon relative to carbonate carbon. The changes in burial rates, in turn, may have produced a positive feedback on climate by briefly drawing down atmospheric pCO2 .

Early Cretaceous spores and pollen of ODP Leg 103 holes

About 80 species of spores and pollen grains were recorded during detailed palynological investigations of selected Lower Cretaceous sections from Holes 638B and 638C and the bottom of Hole 641C. Most of them are long-ranging taxa with worldwide distribution. However, on the Iberian margin and in the southern European basins, Trilobosporites canadensis, Trilobosporites bernissartensis, Parvisaccites amplus, Foveosporites subtriangularis, and Ephedripites multicostatus seem to be index species of the Valanginian to late Aptian interval. Clavatipollenites was not recovered in the Barremian marginal marine sediments.

Stable carbon isotope record and geochemistry of late Miocene-early Pliocene sediments from DSDP Site 90-590 in the Tasman Sea

Biogenic components of sediment accumulated at high rates beneath frontal zones of the Indian and Pacific oceans during the late Miocene and early Pliocene. The delta13C of bulk and foraminiferal carbonate also decreased during this time interval. Although the two observations may be causally linked, and signify a major perturbation in global biogeochemical cycling, no site beneath a frontal zone has independent records of export production and delta13C on multiple carbonate phases across the critical interval of interest. Deep Sea Drilling Project (DSDP) site 590 lies beneath the Tasman Front (TF), an eddy-generating jetstream in the southwest Pacific Ocean. To complement previous delta13C records of planktic and benthic foraminifera at this location, late Neogene records of CaCO3 mass accumulation rate (MAR), Ca/Ti, Ba/Ti, Al/Ti, and of bulk carbonate and foraminiferal delta13C were constructed at site 590. The delta13C records include bulk sediment, bulk sediment fractions (<63 µm and 5-25 µm), and the planktic foraminifera Globigerina bulloides, Globigerinoides sacculifer (with and without sac), and Orbulina universa. Using current time scales, CaCO3 MARs, Ca/Ti, Al/Ti and Ba/Ti ratios are two to three times higher in upper Miocene and lower Pliocene sediment relative to overlying and underlying units. A significant decrease also occurs in all delta13C records. All evidence indicates that enhanced export production - the 'biogenic bloom' - extended to the southwest Pacific Ocean between ca. 9 and 3.8 Ma, and this phenomenon is coupled with changes in delta13C - the 'Chron C3AR carbon shift'. However, CaCO3 MARs peak ca. 5 Ma whereas elemental ratios are highest ca. 6.5 Ma; foraminiferal delta13C starts to decrease ca. 8 Ma whereas bulk carbonate delta13C begins to drop ca. 5.6 Ma. Temporal discrepancies between the records can be explained by changes in the upwelling regime at the TF, perhaps signifying a link between changes in ocean-atmosphere circulation change and widespread primary productivity.

Early Cretaceous planktonic foraminifera from the Tethys

Early Cretaceous planktonic foraminiferal assemblages include rare planispiral and pseudoplanispiral morphotypes with elongate chambers that BouDagher-Fadel et al. assigned to Schackoina or accommodated in the new genus Claviblowiella. New findings of well-preserved planktonic foraminiferal faunas from the Lesches en Diois (SE France) section, the Cismon core (NE Italy), the Calabianca (NW Sicily) section and the Upper Aptian of Deep Sea Drilling Project (DSDP) Site 545 drilled off Morocco, have allowed a better understanding of the morphological features of these rare, unevenly distributed taxa. Our data demonstrate that each small planispiral species with globular chambers has a corresponding "clavate" morphotype which (as the "normal" forms) exhibits a smooth, finely perforate wall. Consequently, the latter have been assigned here to the genus Globigerinelloides and treated as subspecies of the "non-clavate" taxa. The (clavate) subspecies belonging to the genus Globigerinelloides here retained are G. duboisi sigali Longoria, G. maridalensis elongatus subsp. nov., G. blowi lobatus subsp. nov. and G. paragottisi clavatus subsp. nov., while Globigerinelloides minai Obregòn de la Parra is not retained. In addition, a new genus, Pseudoschackoina, type species Planomalina saundersi Bolli (senior synonym of Hastigerinoides cepedai Obregòn de la Parra, has been formalised for individuals possessing elongate, pointed, laterally compressed chambers, bearing tubulospines arranged on a pseudoplanispiral (dysaxial) coiling mode. Stratigraphically, in the sections studied the first taxon to appear is Pseudoschackoina saundersi, in the uppermost part of the Selli Level (=OAE1a), immediately followed, just above the OAE1a, by all the "clavate" globigerinelloidids. Regarding the last occurrences, Pseudoschackoina saundersi and G. maridalensis elongatus disappear in the lower part of the Globigerinelloides algerianus Zone, Globigerinelloides paragottisi clavatus at the top of the same zone, while Globigerinelloides blowi lobatus and G. duboisi sigali range up to the lower part of the Ticinella bejaouaensis Zone.

Seawater carbonate chemistry and biological processes during experiments with early life stages of the blue mussel Mytilus edulis, 2010

Several experiments have shown a decrease of growth and calcification of organisms at decreased pH levels. There is a growing interest to focus on early life stages that are believed to be more sensitive to environmental disturbances such as hypercapnia. Here, we present experimental data, acquired in a commercial hatchery, demonstrating that the growth of planktonic mussel (Mytilus edulis) larvae is significantly affected by a decrease of pH to a level expected for the end of the century. Even though there was no significant effect of a 0.25-0.34 pH unit decrease on hatching and mortality rates during the first 2 days of development nor during the following 13-day period prior to settlement, final shells were respectively 4.5±1.3 and 6.0±2.3% smaller at pHNBS~7.8 (pCO2~1100-1200 µatm) than at a control pHNBS of ~8.1 (pCO2~460-640 µatm). Moreover, a decrease of 12.0±5.4% of shell thickness was observed after 15d of development. More severe impacts were found with a decrease of ~0.5 pHNBS unit during the first 2 days of development which could be attributed to a decrease of calcification due to a slight undersaturation of seawater with respect to aragonite. Indeed, important effects on both hatching and D-veliger shell growth were found. Hatching rates were 24±4% lower while D-veliger shells were 12.7±0.9% smaller at pHNBS~7.6 (pCO2~1900 µatm) than at a control pHNBS of ~8.1 (pCO2~540 µatm). Although these results show that blue mussel larvae are still able to develop a shell in seawater undersaturated with respect to aragonite, the observed decreases of hatching rates and shell growth could lead to a significant decrease of the settlement success. As the environmental conditions considered in this study do not necessarily reflect the natural conditions experienced by this species at the time of spawning, future studies will need to consider the whole larval cycle (from fertilization to settlement) under environmentally relevant conditions in order to investigate the potential ecological and economical losses of a decrease of this species fitness in the field.

Effect of ocean warming and acidification on the early life stages of subtropical Acropora spicifera

This study investigated the impacts of acidified seawater (pCO2 900 µatm) and elevated water temperature (+3 °C) on the early life history stages of Acropora spicifera from the subtropical Houtman Abrolhos Islands (28°S) in Western Australia. Settlement rates were unaffected by high temperature (27 °C, 250 µatm), high pCO2 (24 °C, 900 µatm), or a combination of both high temperature and high pCO2 treatments (27 °C, 900 µatm). There were also no significant differences in rates of post-settlement survival after 4 weeks of exposure between any of the treatments, with survival ranging from 60 to 70 % regardless of treatment. Similarly, calcification, as determined by the skeletal weight of recruits, was unaffected by an increase in water temperature under both ambient and high pCO2 conditions. In contrast, high pCO2 significantly reduced early skeletal development, with mean skeletal weight in the high pCO2 and combined treatments reduced by 60 and 48 %, respectively, compared to control weights. Elevated temperature appeared to have a partially mitigative effect on calcification under high pCO2; however, this effect was not significant. Our results show that rates of settlement, post-settlement survival, and calcification in subtropical corals are relatively resilient to increases in temperature. This is in marked contrast to the sensitivity to temperature reported for the majority of tropical larvae and recruits in the literature. The subtropical corals in this study appear able to withstand an increase in temperature of 3 °C above ambient, indicating that they may have a wider thermal tolerance range and may not be adversely affected by initial increases in water temperature from subtropical 24 to 27 °C. However, the reduction in skeletal weight with high pCO2 indicates that early skeletal formation will be highly vulnerable to the changes in ocean pCO2 expected to occur over the twenty-first century, with implications for their longer-term growth and resilience.

Element abundances, loss on ignition, total analyzed abundances, CIA values, and Al-oxide/Ti-oxide ratios of sediment core CRP-2A (Table1)

The CRP-2/2A core, drilled in western McMurdo Sound in October and November 1998, penetrated 624 m of Quaternary. Pliocene, lower Miocene, and Oligocene glacigenic sediments. The palaeoclimatic record of CRP-2/2A is examined using major element analyses of bulk core samples of fine grained sediments (mudstones and siltstones) and the Chemical Index of Alteration (CIA) of Nesbitt & Young (1982). The CIA is calculated from the relative abundances of AI, K, Ca, and Na oxides, and its magnitude increases as the effects of chemical weathering increase. However, changes in sediment provenance can also affect the CIA, and provenance changes are recorded by shifts in the Al2O3/TiO2 ratios and the Nb contents of these CRP-2/2A mudstones. Relatively low CIA values (40-50) occur throughout the CRP-2/2A sequence, whereas the Al2O3/TiO2 ratio decreases upsection. The major provenance change is an abrupt onset of McMurdo Volcanic Group detritus at ~300 mbsf and is best characterized by a rapid increase in Nb content in the sediments. This provenance shift is not evident in the CIA record, suggesting that a contribution from the Ferrar Dolerite to the older sediments was replaced by an input of McMurdo Volcanic Group material in the younger sediments. If this is true, then the relatively uniform CIA values indicate relatively consistent palaeoweathering intensities throughout the Oligocene and early Miocene in the areas that supplied sediment to CRP-2/2A.

Orbitally tuned time scale and astronomical forcing in the middle Eocene to early Oligocene determined on ODP and IODP sediment cores

Deciphering the driving mechanisms of Earth system processes, including the climate dynamics expressed as paleoceanographic events, requires a complete, continuous, and high-resolution stratigraphy that is very accurately dated. In this study, we construct a robust astronomically calibrated age model for the middle Eocene to early Oligocene interval (31-43 Ma) in order to permit more detailed study of the exceptional climatic events that occurred during this time, including the Middle Eocene Climate Optimum and the Eocene/Oligocene transition. A goal of this effort is to accurately date the middle Eocene to early Oligocene composite section cored during the Pacific Equatorial Age Transect (PEAT, IODP Exp. 320/321). The stratigraphic framework for the new time scale is based on the identification of the stable long eccentricity cycle in published and new high-resolution records encompassing bulk and benthic stable isotope, calibrated XRF core scanning, and magnetostratigraphic data from ODP Sites 171B-1052, 189-1172, 199-1218, and 207-1260 as well as IODP Sites 320-U1333, and -U1334 spanning magnetic polarity Chrons C12n to C20n. Subsequently we applied orbital tuning of the records to the La2011 orbital solution. The resulting new time scale revises and refines the existing orbitally tuned age model and the Geomagnetic Polarity Time Scale from 31 to 43 Ma. Our newly defined absolute age for the Eocene/Oligocene boundary validates the astronomical tuned age of 33.89 Ma identified at the Massignano (Italy) global stratotype section and point. Our compilation of geochemical records of climate-controlled variability in sedimentation through the middle-to-late Eocene and early Oligocene demonstrates strong power in the eccentricity band that is readily tuned to the latest astronomical solution. Obliquity driven cyclicity is only apparent during very long eccentricity cycle minima around 35.5 Ma, 38.3 Ma and 40.1 Ma.

Ocean acidification and its potential effects on the early life-history of non-calcifying and calcifying echinoderm (Odontaster validus, Patiriella regularis and Arachnoides placenta) larvae, 2011

Ocean acidification, as a result of increased atmospheric CO2, has the potential to adversely affect the larval stages of many marine organisms and hence have profound effects on marine ecosystems. This is the first study of its kind to investigate the effects of ocean acidification on the early life-history stages of three echinoderms species, two asteroids and one irregular echinoid. Potential latitudinal variations on the effects of ocean acidification were also investigated by selecting a polar species (Odontaster validus), a temperate species (Patiriella regularis), and a tropical species (Arachnoides placenta). The effects of reduced seawater pH levels on the fertilization of gametes, larval survival and morphometrics on the aforementioned species were evaluated under experimental conditions. The pH levels considered for this research include ambient seawater (pH 8.1 or pH 8.2), levels predicted for 2100 (pH 7.7 and pH 7.6) and the extreme pH of 7.0, adjusted by bubbling CO2 gas into filtered seawater. Fertilization for Odontaster validus and Patiriella regularis for the predicted scenarios for 2100 was robust, whereas fertilization was significantly reduced in Arachnoides placenta. Larval survival was robust for the three species at pH 7.8, but numbers declined when pH dropped below 7.6. Normal A. placenta larvae developed in pH 7.8, whereas smaller larvae were observed for O. validus and P. regularis under the same pH treatment. Seawater pH levels below 7.6 resulted in smaller and underdeveloped larvae for all three species. The greatest effects were expected for the Antarctic asteroid O. validus but overall the tropical sand dollar A. placenta was the most affected by the reduction in seawater pH. The effects of ocean acidification on the asteroids O. validus and P. regulars, and the sand dollar A. placenta are species-specific. Several parameters, such as taxonomic differences, physiology, genetic makeup and the population's evolutionary history may have contributed to this variability. This study highlights the vulnerability of the early developmental stages and the complexity of ocean acidification. However, future research is needed to understand the effects at individual, community and ecosystem levels.

Molybdenum and sulphur isotope ratios of early Pleistocene sapropels of ODP Hole 160-969D

Organic-rich sediments (sapropels) deposited in the Mediterranean are presumed to have formed during periods of increased productivity, and/or deep water oxygen depletion, possibly including the development of sulfidic conditions (euxinia). Geochemical redox proxies (Re, Mo, Mo isotopes, V, Fe/Al, and multiple S isotopes) in 8 sapropels from the Pleistocene confirm water column euxinic conditions of varying intensity during sapropel deposition. These same proxies indicate an oxic origin for hemipelagic sediments deposited between sapropel-forming episodes. In one intensively sampled sapropel, deposited between 1.450 and 1.458 Ma, changing concentrations of organic carbon, Ba, Re, Mo, V, and Fe/Al track one another closely, reflecting coupling between water column euxinia and biological productivity. Multiple S isotope data from this sapropel suggest that the redox interface where oxidative sulfur cycling occurred was present in the sediments during hemipelagic sedimentation, but moved into the water column during sapropel deposition. Molybdenum isotopes of these 8 sapropels encompass a range of values (d98Mo = +0.2 to +1.7), but are all 98Mo-depleted relative to seawater (d98Mo = +2.3 per mil), suggesting that quantitative removal of Mo did not occur. This finding contrasts with modern Black Sea sediments. In general, Re/Mo ratios in sapropels are greater than in modern seawater, implying that the water column was not sufficiently sulfidic during sapropel-forming episodes to induce complete removal of both these elements. Surprisingly, the heaviest d98Mo values are found within hemipelagic sediments. Very few of the hemipelagic samples preserve the negative d98Mo values commonly associated with modern oxic marine sediments. Many of the hemipelagic samples also contained higher concentrations of Re and Mo than are common in oxic sediments. These features may be attributable to diffusion from the sapropels of a 98Mo-enriched component into the hemipelagic sediments.

(Table 1) Organic and inorganic geochemical analysis of Late Jurassic to Early Cretaceous black shale sediments from the Norwegian-Greenland Seaway

The Late Jurassic to Early Cretaceous (Volgian-Ryazanian) was a period of a second-order sea-level low stand, and it provided excellent conditions for the formation of shallow marine black shales in the Norwegian-Greenland Seaway (NGS). IKU Petroleum Research drilling cores taken offshore along the Norwegian shelf were investigated with geochemical and microscopic approaches to (1) determine the composition of the organic matter, (2) characterize the depositional environments, and (3) discuss the mechanisms which may have controlled production, accumulation, and preservation of the organic matter. The black shale sequences show a wide range of organic carbon contents (0.5-7.0 wt %) and consist of thermally immature organic matter of type II to II/III kerogen. Rock-Eval pyrolysis revealed fair to very good petroleum source rock potential, suggesting a deposition in restricted shallow marine basins. Well-developed lamination and the formation of autochthonous pyrite framboids further indicate suboxic to anoxic bottom water conditions. In combination with very low sedimentation rates it seems likely that preservation was the principal control on organic matter accumulation. However, a decrease of organic carbon preservation and an increase of refractory organic matter from the Volgian to the Hauterivian are superimposed on short-term variations (probably reflecting Milankovitch cycles). Various parameters indicate that black shale formation in the NGS was gradually terminated by increased oxidative conditions in the course of a sea-level rise.