Parameters of the Earths orbit for the last 5 Million years in 1 kyr resolution

New values for the astronomical parameters of the Earth's orbit and rotation (eccentricity, obliquity and precession) are proposed for paleoclimatic research related to the Late Miocene, the Pliocene and the Quaternary. They have been obtained from a numerical solution of the Lagrangian system of the planetary point masses and from an analytical solution of the Poisson equations of the Earth-Moon system. The analytical expansion developed in this paper allows the direct determination of the main frequencies with their phase and amplitude. Numerical and analytical comparisons with the former astronomical solution BER78 are performed so that the accuracy and the interval of time over which the new solution is valid can be estimated. The corresponding insolation values have also been computed and compared to the former ones. This analysis leads to the conclusion that the new values are expected to be reliable over the last 5 Ma in the time domain and at least over the last 10 Ma in the frequency domain.

Calcareous dinoflagellates in the eastern equatorial Atlantic

Sediments of the Equatorial Atlantic (core GeoB 1105-4) have been investigated for both calcareous dinoflagellates and organic-walled dinoflagellate cysts. In order to determine the ecological affinity of calcareous dinoflagellates the statistical methods of Detrended Correspondence Analysis (DCA) and Redundancy Analysis (RDA) were used. Utilising DCA, distribution patterns of calcareous dinoflagellates have been compared with those of the ecologically much better known organic-walled dinoflagellate cysts. This method was also used to determine which environmental gradients have a major influence on the species composition. By using existing environmental information based on benthic and planktic foraminifera, such as Sea Surface Temperature (SST) and stable oxygen and carbon isotopes, as well as information on the amount of Calcium Carbonate and Total Organic Carbon (TOC) in bottom sediments, these gradients could be interpreted in terms of productivity and glacial-interglacial trends. Using RDA, the direct relationships between the distribution patterns of calcareous dinoflagellates with the above mentioned external variables could be determined. For the studied region and time interval (141-6.7 ka) the calcareous dinoflagellates show enhanced abundances in periods with reduced productivity most probably related to decreased divergence and relatively stratified, oligotrophic oceanic conditions.

(Appendix A) Abundance of calcareous dinoflagellates of sediment core GeoB2204-2

The environmental preferences of calcareous dinoflagellates have been investigated over the last 140 ka by comparing material from two sediment cores: one from the highly productive equatorial divergence of the eastern Atlantic Ocean and the other from the low productivity western tropical Atlantic Ocean. Pronounced differences in palaeoproductivity between the two sediment cores are indicated by high and variable organic carbon accumulation rates in the east, in contrast to relatively constant and low values in the west. Calcareous dinoflagellates show just the opposite pattern: high accumulation rates in the west and lower in the east. At the equatorial divergence, temporal variations of calcareous dinoflagellate and organic carbon accumulation rates show, for the most part, an inverse relationship. High calcareous dinoflagellate content coincides with low organic carbon accumulation rates and vice versa. In the investigated region and time interval, enhanced production of calcareous dinoflagellates can be correlated to periods of reduced palaeoproductivity probably related to relatively stratified conditions of the upper water column.

Dinoflagellate cyst assemblages, oxygen isotope records of foraminifera, and alkenone and Mg/Ca-based SST estimates for the time interval 3.40-3.18 Ma (Late Pliocene) from five North Atlantic and Caribbean sediment cores

The early Late Pliocene (3.6 to ~3.0 million years ago) is the last extended interval in Earth's history when atmospheric CO2 concentrations were comparable to today's and global climate was warmer. Yet a severe global glaciation during marine isotope stage (MIS) M2 interrupted this phase of global warmth ~3.30 million years ago, and is seen as a premature attempt of the climate system to establish an ice-age world. Our geochemical and palynological records from five marine sediment cores along a Caribbean to eastern North Atlantic transect show that increased Pacific-to-Atlantic flow via the Central American Seaway weakened the North Atlantic Current (NAC) and attendant northward heat transport prior to MIS M2. The consequent cooling of the northern high latitude oceans permitted expansion of the Greenland ice sheet during MIS M2, despite near-modern atmospheric CO2 concentrations. Before and after MIS M2, heat transport via the NAC was crucial in maintaining warm climates comparable to those predicted for the end of this century.

Oxygen isotopes, IRD and SST reconstruction for the interval MIS31-19 of IODP Site 306-U1314

Early and Mid-Pleistocene climate, ocean hydrography and ice sheet dynamics have been reconstructed using a high-resolution data set (planktonic and benthic d18O time series, faunal-based sea surface temperature (SST) reconstructions and ice-rafted debris (IRD)) record from a high-deposition-rate sedimentary succession recovered at the Gardar Drift formation in the subpolar North Atlantic (Integrated Ocean Drilling Program Leg 306, Site U1314). Our sedimentary record spans from late in Marine Isotope Stage (MIS) 31 to MIS 19 (1069-779 ka). Different trends of the benthic and planktonic oxygen isotopes, SST and IRD records before and after MIS 25 (~940 ka) evidence the large increase in Northern Hemisphere ice-volume, linked to the cyclicity change from the 41-kyr to the 100-kyr that occurred during the Mid-Pleistocene Transition (MPT). Beside longer glacial-interglacial (G-IG) variability, millennial-scale fluctuations were a pervasive feature across our study. Negative excursions in the benthic d18O time series observed at the times of IRD events may be related to glacio-eustatic changes due to ice sheets retreats and/or to changes in deep hydrography. Time series analysis on surface water proxies (IRD, SST and planktonic d18O) of the interval between MIS 31 to MIS 26 shows that the timing of these millennial-scale climate changes are related to half-precessional (10 kyr) components of the insolation forcing, which are interpreted as cross-equatorial heat transport toward high latitudes during both equinox insolation maxima at the equator.

(Table 3) Run conditions and phase relations and proportions during cooling rate experiments on ODP Interval 163-989B-10R-7,55-59

Equilibrium melting and controlled cooling experiments were undertaken to constrain the crystallization and cooling histories of tholeiitic basalts recovered by the Ocean Drilling Program drilling of Site 989 on the Southeast Greenland continental margin. Isothermal experiments conducted at 1 atm. and at the fayalite-magnetite-quartz buffer using lava sample Section 163-989B-10R-7 yielded the equilibrium appearance sequence with decreasing temperature: olivine at 1184 ± 2ºC; plagioclase at 1177ºC ± 5ºC; augite at 1167 ± 5ºC; and pigeonite at 1113 ± 12ºC. In controlled cooling experiments using the same starting composition and cooling rates between 10ºC/hr and 2000ºC/hr, we find a significant temperature delay in the crystallization of olivine, plagioclase, and augite (relative to the equilibrium appearance temperature); pigeonite does not form under any dynamic crystallization conditions. Olivine exhibits the largest suppression in appearance temperature (e.g., 30º for 10ºC/hr and >190º at 100ºC/hr), while plagioclase shows the smallest (~10ºC at 10ºC/hr; 30ºC at 100ºC/hr, and ~80ºC at 1000ºC/hr). These results are in marked contrast to those obtained on lunar basalts, which generally show a large suppression of plagioclase crystallization and modest suppression of olivine crystallization with an increased cooling rate. The results we report agree well with the petrography of lavas recovered from Site 989. Furthermore, the textural analysis of run products, representing a large range of cooling rates and quench temperatures (1150ºC to 1000ºC), provide a framework for evaluating cooling conditions necessary for glass formation, rates of plagioclase growth, and kinetic factors governing plagioclase growth morphology. Specifically, we use these insights to interpret the textural and mineralogical features of the unusual compound flow recovered at Site 989. We concluded from the analysis that this flow most likely records multiple breakouts from a distal tube at an abrupt break in slope, possibly a fault scarp, resulting in the formation of a lava fan delta. This interpretation implies that normal faulting of the oldest lava sequences (lower and, possibly, middle series) preceded eruption of Site 989 lavas.

Auxiliary material and basic geochemical and benthic foraminiferal stable isotope data for the interval bracketing Eocene Thermal Maximum 2 (ETM2) at DSDP Sites 401 and 550 in the northeastern Atlantic Ocean

Ever since its discovery, Eocene Thermal Maximum 2 (ETM2; ~53.7 Ma) has been considered as one of the "little brothers" of the Paleocene-Eocene Thermal Maximum (PETM; ~56 Ma) as it displays similar characteristics including abrupt warming, ocean acidification, and biotic shifts. One of the remaining key questions is what effect these lesser climate perturbations had on ocean circulation and ventilation and, ultimately, biotic disruptions. Here we characterize ETM2 sections of the NE Atlantic (Deep Sea Drilling Project Sites 401 and 550) using multispecies benthic foraminiferal stable isotopes, grain size analysis, XRF core scanning, and carbonate content. The magnitude of the carbon isotope excursion (0.85-1.10 per mil) and bottom water warming (2-2.5°C) during ETM2 seems slightly smaller than in South Atlantic records. The comparison of the lateral d13C gradient between the North and South Atlantic reveals that a transient circulation switch took place during ETM2, a similar pattern as observed for the PETM. New grain size and published faunal data support this hypothesis by indicating a reduction in deepwater current velocity. Following ETM2, we record a distinct intensification of bottom water currents influencing Atlantic carbonate accumulation and biotic communities, while a dramatic and persistent clay reduction hints at a weakening of the regional hydrological cycle. Our findings highlight the similarities and differences between the PETM and ETM2. Moreover, the heterogeneity of hyperthermal expression emphasizes the need to specifically characterize each hyperthermal event and its background conditions to minimalize artifacts in global climate and carbonate burial models for the early Paleogene.