Pollen record from Kleiner Mochowsee, Germany

A Holocene pollen diagram from Kleiner Mochowsee (northern Niederlausitz, East Germany) shows pine as an important constituent of the woodland south of the Schwielochsee. Oak woodland was widespread since the Atlantic. Betula lost its importance at the end of the Preboreal. Fagus is represented continuously in the pollen record since the Atlantic, Carpinus since the Subboreal. However, the two latter tree species remain without great importance throughout the whole pollen record. The poor sandy soils are furthermore reflected by the low values of Corylus during the Boreal, comparable to other records from Berlin and its surrounding area. The 'classical' elm decline could be shown for the Niederlausitz, radiocarbon dates assume a contemporaneous age for this event with other records from northern Germany. Only small-scaled human impact is indicated in prehistoric times, during the migration period it seems to have ceased completely. Later, in the Medieval, deforestation and tillage can be shown. Secale was cultivated since the early Medieval; an accompanying weed flora appeared at the same time. Cultivation of Fagopyrum and Linum usitatissimum could be shown for the late Medieval times.

Chemistry of biogenic sediments from the equatorial Pacific

To increase our understanding of the mechanisms that control the distribution of Al and Ti within marine sediment, we performed sequential extractions targeting the chemical signatures of the loosely bound, exchangeable, carbonate, oxide, organic, opal, and residual fraction of sediment from a carbonate-dominated regime (equatorial Pacific) and from a mixed opal-terrigenous regime (West Antarctic Peninsula). We observe a systematic partitioning of Al and Ti between sediment phases that is related to bulk Al/Ti. We show that, where we can quantify an Al(excess) component, the dissolved Al is preferentially affiliated with the oxide fraction, resulting in Al/Ti molar ratios of 500-3000. This is interpreted as the result of surface complexation in the water column of dissolved Al onto oxyhydroxides. We also observe a previously undetected Ti(excess) with as much as 80% of the total Ti in the organic fraction, which is most likely a function of metal-organic colloidal removal from the water column. In samples where the excess metals are obscured by the detrital load, the Al and Ti are almost exclusively found in the residual phase. This argues for the paired removal of Al (preferentially by the oxide component) and Ti (preferentially by the organic component) from the water column by settling particulate matter. This research builds upon earlier work that shows changes in the bulk ratio of Al to Ti in carbonate sediment from the central-equatorial Pacific that coincide with changes in the sedimentary bulk accumulation rate (BAR). The ratios that are observed are as much as three times higher than typical shale values, and were interpreted as the result of scavenging of dissolved Al onto particles settling in the water column. Because this non-terrigenous Al(excess) accounts for up to 50% of the total sedimentary Al inventory and correlates best with BAR, the bulk Al/Ti may be a sensitive tracer of particle flux and, therefore, export production. Because we show that the excess metals are the result of scavenging processes, the bulk Al/Ti may be considered a sensitive proxy for this region.

CaCO3 content and bulk densitiy of east equatorial Pacific Ocean sediment cores

Nine piston cores and six triggerweight cores retrieved from the eastern equatorial Pacific Ocean during the Venture 1 expedition were analyzed for dry-bulk density (DBD) and CaCO3 content. Sites are located along a north-south transect at 110°W from 11°N to 3°S and along an east-west transect from 110° to 90°W, at approximately 3°S. The data reveal two DBD-CaCO3 relationships and four patterns of CaCO3 abundance.

Calcium carbonate, sedimentation and mass accumulation rates at DSDP Site 85-572

At Site 572, located at 1°N, 114° W (3903 m water depth), we recovered a continuous hydraulic piston cored section of upper Miocene to upper Pleistocene pelagic sediments. The sediment is composed of biogenic carbonate and silica with nonbiogenic material as a minor component. Detailed analysis of the calcium carbonate content shows that the degree of variability in carbonate deposition apparently changed markedly between the late Miocene and Pliocene at this equatorial Pacific site. During this interval carbonate mass accumulation rates decreased from 2.6 to 0.8 g/cm**2 per 10**3 yr. If we assume that variations in CaCO3 content reflect changes in the degree of dissolution, then the detailed carbonate analysis would suggest that the degree of variability in carbonate deposition decreases by a factor of 5 as the dominant wavelength of variations increases significantly. However, if the variability in carbonate concentration is described in terms of changes in mean mass accumulation, calculations then suggest that relatively small changes in noncarbonate rates may be important in controlling the observed carbonate records. In addition, the analysis suggests that the degree of variability observed in pelagic carbonate data may in part reflect total accumulation rates. Intervals with high sedimentation rates show lower amplitude variations in concentration than intervals with lower sedimentation rates for the same degree of change in the carbonate accumulation rate.

Geotechnical engineering characterization of sediments at DSDP Leg 72 Holes

The hydraulic piston coring device (HPC-15) allows recovery of deep ocean sediments with minimal disturbance. The device was used during Leg 72 of the Deep Sea Drilling Project (DSDP) aboard the Glomar Challenger. Core samples were recovered from bore holes in the Rio Grande Rise in the southwest Atlantic Ocean. Relatively undisturbed sediment cores were obtained from Holes 515A, 516, 517, and 518. The results of shipboard physical property measurements and on-shore geotechnical laboratory tests on these cores are presented in this chapter. A limited number of 0.3 m cores were obtained and used in a series of geotechnical tests, including one-dimensional consolidation, direct shear, Atterburg limit, particle size analysis, and specific gravity tests. Throughout the testing program, attention was focused on assessment of sample disturbance associated with the HPC-15 coring device. The HPC-15 device limits sample disturbance reasonably well in terrigenous muds (clays). However, sample disturbance associated with coring calcareous sediments (nannofossil-foraminifer oozes) is severe. The noncohesive, granular behavior of the calcareous sediments is vulnerable to severe disturbance, because of the design of the sampling head on the device at the time of Leg 72. A number of modifications to the sampling head design are recommended and discussed in this chapter. The modifications will improve sample quality for testing purposes and provide longer unbroken core samples by reducing friction between the sediment column and the sampling tool.

Sedimentology and planktonioc foraminifera of core SU90-08

The observation by Heinrich (1988) that, during the last glacial period, much of the input of ice-rafted detritus to the North Atlantic sediments may have occurred as a succession of catastrophic events, rekindled interest on the history of the northern ice sheets over the last glacial period. In this paper, we present a rapid method to study the distribution of these events (both in space and time) using whole core low-field magnetic susceptibility. We report on approximately 20 cores covering the last 150 to 250 kyr. Well-defined patterns of ice-rafted detritus appear during periods of large continental ice-sheet extent, although these are not always associated within their maxima. Most of the events may be traced across the North Atlantic Ocean. For the six most recent Heinrich layers (HL), two distinct patterns exist: HL1, HL2, HL4, HL5 are distributed along the northern boundary of the Glacial Polar Front, over most of the North Atlantic between ~40° and 50°N; HL3 is more restricted to the central and eastern part of the northern Atlantic. The Nd-Sr isotopic composition of the material constituting different Heinrich events indicates the different provenance of the two patterns: HL3 has a typical Scandinavia-Arctic-Icelandic 'young crust' signature, and the others have a large component of northern Quebec and northern West Greenland 'old crust' material. These isotopic results, obtained on core SU-9008 from the North American basin, are in agreement with the study by Jantschik and Huon (1992), who used K-Ar dating of silt- and clay-size fractions of an eastern basin core (ME-68-89). These data confirm the large spatial scale of these events, and the enormous amount of ice-rafted detritus they represent.

Size-related stable isotope changes in Late Cretaceous and Recent planktic foraminifera from the western tropical Atlantic

The paleoecology of Cretaceous planktic foraminifera during the Late Cenomanian to Coniacian period (~95-86 Ma) remains controversial since much of the tropical marine record is preserved as chalk and limestone with uncertain geochemical overprints. Here we present delta13C and delta18O data from sieve size fractions of monospecific samples of exceptionally well preserved planktic foraminifera recovered during Ocean Drilling Program Leg 207 (Demerara Rise, western tropical Atlantic). Our results suggest that all species studied (Hedbergella delrioensis, Heterohelix globulosa, Marginotruncana sinuosa, Whiteinella baltica) grew primarily in surface waters and did not change their depth habitat substantially during their life cycle. Comparison of size-related ontogenetic trends in delta13C in Cretaceous and modern foraminifera further suggests that detection of dinoflagellate photosymbiosis using delta13C is confounded by physiological effects during the early stages of foraminifer growth, raising doubts about previous interpretations of photosymbiosis in small foraminifera species. We propose that obligate photosymbiosis involving dinoflagellates may not have evolved until the Campanian or Maastrichtian since our survey of Cenomanian-Coniacian species does not find the delta18O and delta13C size-related trends observed in modern foraminifer-dinoflagellate symbioses.

Clay mineraology and grain size composition of surface sediments from South Pacific Ocean

The reconstruction of low-latitude ocean-atmosphere interactions is one of the major issues of (paleo-)environmental studies. The trade winds, extending over 20° to 30° of latitude in both hemispheres, between the subtropical highs and the intertropical convergence zone, are major components of the atmospheric circulation and little is known about their long-term variability on geological time-scales, in particular in the Pacific sector. We present the modern spatial pattern of eolian-derived marine sediments in the eastern equatorial and subtropical Pacific (10°N to 25°S) as a reference data set for the interpretation of SE Pacific paleo-dust records. The terrigenous silt and clay fractions of 75 surface sediment samples have been investigated for their grain-size distribution and clay-mineral compositions, respectively, to identify their provenances and transport agents. Dust delivered to the southeast Pacific from the semi- to hyper-arid areas of Peru and Chile is rather fine-grained (4-8 µm) due to low-level transport within the southeast trade winds. Nevertheless, wind is the dominant transport agent and eolian material is the dominant terrigenous component west of the Peru-Chile Trench south of ~ 5°S. Grain-size distributions alone are insufficient to identify the eolian signal in marine sediments due to authigenic particle formation on the sub-oceanic ridges and abundant volcanic glass around the Galapagos Islands. Together with the clay-mineral compositions of the clay fraction, we have identified the dust lobe extending from the coasts of Peru and Chile onto Galapagos Rise as well as across the equator into the doldrums. Illite is a very useful parameter to identify source areas of dust in this smectite-dominated study area.