Ages, biostratigraphic datums, and coiling ratios of Pulleniatina in sediments from DSDP Holes 15-154A and 16-157

Pliocene and Pleistocene planktonic foraminiferal biogeography and paleoceanography have been examined in Deep Sea Drilling Project (DSDP) sites of the Panama Basin (Pacific Ocean) and Colombian and Venezuelan Basins (Atlantic Ocean) to determine the timing of the isolation of Atlantic and Pacific tropical planktonic faunas resulting from the development of the Central American isthmus. Previous studies have suggested a late Miocene to middle Pliocene occurrence of this event. The Panama Basin (DSDP site 157) and the Colombian Basin (DSDP site 154A) share two early Pliocene biogeographic events: (1) great abundance of sinistral coiling Neogloboquadrina pachyderma at 4.3 m.y. ago at site 157 and 0.7 m.y. later at site 154A, and (2) a sinistral-to-dextral change in the coiling-direction preference in Pulleniatina 3.5 m.y. ago at both locations. Identification of these events farther to the east in the Venezuelan Basin (DSDP site 148) is complicated by insufficient lower Pliocene core recovery, but abundant sinistral N. pachydcrma appear to have extended far to the east in the Caribbean 3.6 m.y. ago; perhaps the early Pliocene abundance of this form is not indicative of cool water. The coiling-direction history and stratigraphic ranges of Pulleniatina became different in the Atlantic and Pacific Oceans during the early Pliocene; this is inferred to result from geographic isolation of the assemblages. Saito (1976) used the temporary disappearance of this genus from Atlantic waters at 3.5 m.y. ago to mark the closure of the Isthmus of Panama, but I show that in the Colombian Basin (site 154A) its disappearance was closer to 3.1 m.y. ago. This suggests the possibility of surface-water communication between the Atlantic and Pacific until that time.

Mean dynamic topography and oceanographic parameters estimated from an inverse model and satellite geodesy, with link to model result in one single NetCDF file (392 MB), including the inverse data error covariance

Geostrophic surface velocities can be derived from the gradients of the mean dynamic topography-the difference between the mean sea surface and the geoid. Therefore, independently observed mean dynamic topography data are valuable input parameters and constraints for ocean circulation models. For a successful fit to observational dynamic topography data, not only the mean dynamic topography on the particular ocean model grid is required, but also information about its inverse covariance matrix. The calculation of the mean dynamic topography from satellite-based gravity field models and altimetric sea surface height measurements, however, is not straightforward. For this purpose, we previously developed an integrated approach to combining these two different observation groups in a consistent way without using the common filter approaches (Becker et al. in J Geodyn 59(60):99-110, 2012, doi:10.1016/j.jog.2011.07.0069; Becker in Konsistente Kombination von Schwerefeld, Altimetrie und hydrographischen Daten zur Modellierung der dynamischen Ozeantopographie, 2012, http://nbn-resolving.de/nbn:de:hbz:5n-29199). Within this combination method, the full spectral range of the observations is considered. Further, it allows the direct determination of the normal equations (i.e., the inverse of the error covariance matrix) of the mean dynamic topography on arbitrary grids, which is one of the requirements for ocean data assimilation. In this paper, we report progress through selection and improved processing of altimetric data sets. We focus on the preprocessing steps of along-track altimetry data from Jason-1 and Envisat to obtain a mean sea surface profile. During this procedure, a rigorous variance propagation is accomplished, so that, for the first time, the full covariance matrix of the mean sea surface is available. The combination of the mean profile and a combined GRACE/GOCE gravity field model yields a mean dynamic topography model for the North Atlantic Ocean that is characterized by a defined set of assumptions. We show that including the geodetically derived mean dynamic topography with the full error structure in a 3D stationary inverse ocean model improves modeled oceanographic features over previous estimates.

(Table 1) Cation exchange capacity and other characteristics of soils common in Lower Saxony, Germany

The chemical and biochemical processes associated with the filtration of rainwater through soils, a step in groundwater recharge, were investigated. Under simulated climatic conditions in the laboratory, undisturbed soil columns of partly loamy sands, sandy soils and loess were run as lysimeters. A series of extraction procedures was carried out to determine solid matter in unaltered rock materials and in soil horizons. Drainage water and moisture movement in the columns were analysed and traced respectively. The behaviour of soluble humic substance was investigated by percolation and suspension experiments. The development of seepage-water in the unsaturated zone is closely associated with the soil genetic processes. Determining autonomous chemical and physical parameters are mineral composition and grain size distribution in the original unconsolidated host rock and prevailing climatic conditions. They influence biological activity and transport of solids, dissolved matter and gases in the unsaturated zone. Humic substances, either as amorphous solid matter or as soluble humic acids play a part in diverse sorption, solution and precipitation processes.

(Table DR1) Biogenic silica and chert in the Pacific Ocean, DSDP and ODP data

Evidence for the dissolution of biogenic silica at the base of pelagic sections supports the hypothesis that much of the chert formed in the Pacific derives from the dissolution and reprecipitation of this silica by hydrothermal waters. As ocean bottom waters flow into and through the crust, they become warmer. Initially they remain less saturated with respect to dissolved silica than pore water in the overlying sediments. With the diffusion of heat, dissolved ions, and to some extent the advection of water itself, biogenic silica in the basal part of the sedimentary section is dissolved. Upon conductively cooling, these pore waters precipitate chert layers. The most common thickness for the basal silica-free zone (20 m) lies below the most common height of the top of the chert interval above basement (50 m). This mode of chert formation explains the frequent occurrence of chert layers at very shallow subbottom depths in pelagic sections of the Pacific. It is also consistent with the common occurrence of cherts