Pollen profiles from three former lakes in the Lake Garda area

1. Late glacial and postglacial sediments from three former lakes in the Lake Garda area (Southern Alps) were investigated. 2. The pollen diagram from Bondone (1550 m) shows an older phase rich in NAP. A younger one corresponds with the Younger Dryas time according to two radiocarbon determinations. In the Preboreal no climatic deterioration could be found. 3. At first plants, which are nowadays typical for snow-ground, pioneer and dwarf shrub associations, immigrated into the surroundings of Bondone. In Alleröd times larch and pine appeared as the first trees. At the beginning of the Preboreal dense forest existed in that region. During the Alleröd timber line was at about 1500 m. 4. In the pollen diagrams from Saltarino (194 m) and Fiavè (654 m) an oldest period rich in NAP is followed by two stadial and two interstadial phases. Tree birches and larches immigrated during the oldest interstadial phase. 5. In the case of Saltarino and Fiavè only a preliminary dating could be made. A correlation seems to be possible with diagrams published by Zoller as well as with the diagram of Bondone. Discrepances in dating, which arise then, are discussed. According to the two possibilities of dating the youngest stadial is synchronous either with the so-called Piottino stadial or the Younger Dryas time. Consequently the oldest interstadial phase of Saltarino corresponds either with the Bölling or with a pre-Bölling interstadial. The last possibility seems to be more probable. 6. In the southern part of the Lake Garda area reforestation was preceded by a long shrub phase mainly with Juniperus. At about 650 m there was a period with Pinus mugo and only with a small amount of Juniperus before reforestation. A phase with Betula nana well known from areas north of the Alps could nowhere be found. 7. In the area under study larch appeared as the first tree. Lateron it has been the most important constituent of the forests near timber line. Birch, which plays an important role as a pioneer tree in Denmark - for instance at the transition of the pollen zones III/IV - as well as in Southern Germany during Bölling time, was of less importance at the southern border of the Alps. In that area the spreading of Pinus occurred very early causing dense forests. 8. During the last stadial phase (probably Younger Dryas time) dense forests with Pinus and Larix existed at 650 m. In the lower part of the Lake Garda area, however, both thermophilous trees as Quercus and herbs frequently occurred. This leads to the conclusion that during this time tree growth was limited by dryness in lower altitudes of the border of the Southern Alps. Pinus and Juniperus, however, do not show higher values in this period, a fact which cannot yet be explained. 9. A list of plants, which were found in the sediments, is compiled. Helodium lanatum, Dictamnus albus, Mercurialis cf. ovata, Buxus, Cerinthe cf. minor, Onosma, Anthericum and Asphodelus albus are findings, which are of special interest for the history of the flora of that region.

Fossil record of foraminifera and ostracoda from the Elsterian-Saalian-Interglacial in Schleswig-Holstein, Germany

Die in den Ablagerungen des marinen Elster-Saale-Interglazials (= Holstein-See = Stör-Meer) gefundenen und als autochthon betrachteten Foraminiferen und Ostrakoden kommen alle noch rezent vor. In vielen Proben wurden daneben aus dem Tertiär und der Oberkreide aufgearbeitete Foraminiferen gefunden. In den Proben aus Muldsberg, Albersdorf und Esbjerg konnte eine gleichgerichtete Faunen-veränderung vom Liegenden zum Hangenden beobachtet werden. Die Formen der jeweils unteren Proben gehören subarktischen bis hochborealen Temperaturen, etwa vollmarinem Milieu und mindestens 30 m Wassertiefe an. Ins Hangende hinein wurde nach Foraminiferen und Ostrakoden das Meer flacher, wärmer und brackischer, bis es schließlich in den obersten Proben wattähnliche Verhältnisse mit wahrscheinlich etwas geringerer Temperatur als am heutigen südlichen Nordseerand erreichte. Diese Beobachtung stimmt überein mit den von GRAHLE (1936) an Mollusken gewonnenen Erkenntnissen und den Schlüssen, die andere Bearbeiter aus einzelnen Mikrofaunen zogen. Es wurde versucht, die Faunen der restlichen Aufschlüsse in das oben erwähnte Schema einzuordnen. Dies gelang nur in zwei Fällen nicht. In Oldenhütten ist das Versagen wahrscheinlich auf unentwirrte Lagerungsstörungen zurückzuführen, in der Austernbank Tarbek liegen abweichende fazielle Verhältnisse vor. Die restlichen Aufschlüsse zeigen, daß aus den vom Eis gestörten Sedimenten doch oft ein sinnvolles Bild rekonstruiert werden kann. Die im kälteren Teil der Holstein-See auftretende Foraminifere Elphidium subarcticum CUSHMAN scheint in den Absätzen des schleswig-holsteinischen Eem-Meeres zu fehlen.

Neodymium isotopes from fossil fish teeth and detrital sediment, and oxygen isotopes from benthic forams from ODP Hole 119-738 B

Ephemeral polar glaciations during the middle-to-late Eocene (48-34 Ma) have been proposed based on far-field ice volume proxy records and near-field glacigenic sediments, although the scale, timing, and duration of these events are poorly constrained. Here we confirm the existence of a transient cool event within a new high-resolution benthic foraminiferal d18O record at Ocean Drilling Program (ODP) Site 738 (Kerguelen Plateau; Southern Ocean). This event, named the Priabonian oxygen isotope maximum (PrOM) Event, lasted ~140 kyr and is tentatively placed within magnetochron C17n.1n (~37.3 Ma) based on the correlation to ODP Site 689 (Maud Rise, Southern Ocean). A contemporaneous change in the provenance of sediments delivered to the Kerguelen Plateau occurs at the study site, determined from the <63 µm fraction of decarbonated and reductively leached sediment samples. Changes in the mixture of bottom waters, based on fossil fish tooth epsilon-Nd, were less pronounced and slower relative to the benthic d18O and terrigenous epsilon-Nd changes. Terrigenous sediment epsilon-Nd values rapidly shifted to less radiogenic signatures at the onset of the PrOM Event, indicating an abrupt change in provenance favoring ancient sources such as the Paleoproterozoic East Antarctic craton. Bottom water epsilon-Nd reached a minimum value during the PrOM Event, although the shift begins much earlier than the terrigenous epsilon-Nd excursion. The origin of the abrupt change in terrigenous sediment provenance is compatible with a change in Antarctic terrigenous sediment flux and/or source as opposed to a reorganization of ocean currents. A change in terrigenous flux and/or source of Antarctic sediments during the oxygen isotope maximum suggests a combination of cooling and ice growth in East Antarctica during the early late Eocene.

Strontium isotope ratios and concentrations in fossil fish teeth

We analyzed 87Sr/86Sr ratios in foraminifera, pore fluids, and fish teeth for samples ranging in age from Eocene to Pleistocene from four Ocean Drilling Program sites distributed around the globe: Site 1090 in the Cape Basin of the Southern Ocean, Site 757 on the Ninetyeast Ridge in the Indian Ocean, Site 807 on the Ontong-Java Plateau in the western equatorial Pacific, and Site 689 on the Maud Rise in the Southern Ocean. Sr isotopic ratios for dated foraminifera consistently plot on the global seawater Sr isotope curve. For Sites 1090, 757, and 807 Sr isotopic values of the pore fluids are generally less radiogenic than contemporaneous seawater values, as are values for fossil fish teeth. In contrast, pore fluid 87Sr/86Sr values at Site 689 are more radiogenic than contemporaneous seawater, and the corresponding fish teeth also record more radiogenic values. Thus, Sr isotopic values preserved in fossil fish teeth are consistently altered in the direction of the pore fluid values; furthermore, there is a correlation between the magnitude of the offset between the pore fluids and the seawater curve, and the associated offset between the fish teeth and the seawater curve. These data suggest that the hydroxyfluorapatite of the fossil fish teeth continues to recrystallize and exchange Sr with its surroundings during burial and diagenesis. Therefore, Sr chemostratigraphy can be used to determine rough ages for fossil fish teeth in these cores, but cannot be used to fine-tune age models. In contrast to the Sr isotopic system, our Nd concentration data, combined with published isotopic and rare earth element data, suggest that fish teeth acquire Nd during early diagenesis while they are still in direct contact with seawater. The concentrations of Nd acquired at this stage are extremely high relative to the concentrations in surrounding pore fluids. As a result, Nd isotopes are not altered during burial and later diagenesis. Therefore, fossil fish teeth from a variety of marine environments preserve a reliable and robust record of deep seawater Nd isotopic compositions from the time of deposition.

Record of pollen, silt and greyscale stack from the Eifel Laminated Sediment Archive (ELSA)

Investigating the processes that led to the end of the last interglacial period is relevant for understanding how our ongoing interglacial will end, which has been a matter of much debate. A recent ice core from Greenland demonstrates climate cooling from 122,000 years ago driven by orbitally controlled insolation, with glacial inception at 118,000 years ago. Here we present an annually resolved, layer-counted record of varve thickness, quartz grain size and pollen assemblages from a maar lake in the Eifel (Germany), which documents a late Eemian aridity pulse lasting 468 years with dust storms, aridity, bushfire and a decline of thermophilous trees at the time of glacial inception. We interpret the decrease in both precipitation and temperature as an indication of a close link of this extreme climate event to a sudden southward shift of the position of the North Atlantic drift, the ocean current that brings warm surface waters to the northern European region. The late Eemian aridity pulse occurred at a 65° N July insolation of 416 W/m**2, close to today's value of 428 W/m**2, and may therefore be relevant for the interpretation of present-day climate variability.

Two pollen profiles of the middle Pleistocene at Samerberg/Upper Bavaria, Germany

Previous pollen analytical studies on sediments from the pleistocene lake basin at Samerberg, situated on the northern edge of the Bavarian Alps (47°45' N, 12°12' E, 607 m a.s.l.) had been performed on samples taken from cores and exposures close to the southern shore of the former lake. After geoelectric and refraction-seismic measurements had shown that the lake basin had been much deeper in its northern part, another core was taken where maximum depth could be expected. The corer penetrated three moraines, two of them lying above pollen-bearing sediments, and one below them, and reached the hard rock (Kössener Kalk) at a depth of 93 m. Two forest phases could be identified by pollen analysis. The pollen record begins abruptly in a forest phase at the end of a spruce-dominated period when fir started to spread (DA 1, DA = pollen zone). Following this, Abies (fir) was the main tree species at Samerberg, Picea being second, and deciduous trees were almost non-existent. First box (Buxus) was of major importance in the fir forests (DA 2), but later on beech (Fagus) and wing-nut (Pterocarya) spread (DA 3). Finally this forest gave way to a spruce forest with pine (DA 4). The beginning and the end of this interglacial cycle are not recorded. Its vegetational development is different from the eemian one known from earlier studies at Samerberg. It is characterized by the occurrence of Abies together with Buxus, Pterocarya and Fagus. A similar association of woody species is known only from the Holsteinian age deposits in an area ranging from England to Poland, though at no other place these species were such important constituents of the vegetation as at Samerberg. Therefore zone 1 to 4 are attributed to the Holsteinian interglacial period. The younger forest phase, separated from the interglacial by a stadial with open vegetation (DA 5), seems to be completely represented, though its sediments are disturbed, apparently by sliding which caused repetition of same-age-sediments in the core (DA 7a, b, c) The vegetational development is simple. A juniper phase (DA 6) was followed by reforestation with spruce, accompanied by some fir (DA 7, 9). Finally pine became the dominant species (DA 9). The simple vegetational development of this younger forest phase does not allow a safe correlation with one of the known pre-eemian interstadials, but for stratigraphical reasons it can be related best to the Dömnitz-interglacial, which among others is also known as Wacken- or Holstein-II-interglacial. Possibly another phase of reforestation is indicated at the end of the following stadial (DA 10). But due to an erosional unconformity nothing than the rise of the juniper curve can be stated. It was only after this sequence of forest phases and periods with open vegetation that glaciers reached the Samerberg area again.

Pollen ages and depths in ODP Site 184-1144

A high-resolution pollen record (sampling interval averages 820 years) has been obtained from ODP Site 1144 (water depth 2037 m), northern South China Sea. The 504-m sequence (in composition length) covers the last 1.03 million years according to micropaleontological and isotopic stratigraphy. The pollen assemblages are characterized by high proportions of Pinus and herb pollen, and by their frequent alternations. Based on these alternations, 29 pollen zones have been recognized that are closely correlated to the Marine Oxygen Isotope Stages (MIS) 1-29. Pinus- dominant pollen zones correspond to interglacial periods with lighter delta18O values, while herb-marked ones relate to the heavier delta18O stages assigned to glacials. Judging from the pollen data, the exposed northern continental shelf of the South China Sea during the glacials was covered by grassland, and the extensive northern shelf has formed only since MIS 6 (ca. 150 ka), probably as a result of tectonic subsidence. Tree pollen influx values are indicative of winter monsoon which began to intensify 600 ka ago. The summer monsoon variations can be approximated by the fern percentage within the total pollen and spore abundance, and the result shows high values in general occurring at interglacials, with the maxima at MIS 15, 5e and 1. The relatively high fern percentage with smaller amplitude in variations before 600 ka might suggest more stable humid conditions before the intensification of winter monsoon.

Sedimentological and pollen records from the fjord region of southern Chile

The position and intensity of the southern westerly wind belt varies seasonally as a consequence of changes in sea surface temperature. During the austral winter, the belt expands northward and the wind intensity in the core decreases. Conversely, during the summer, the belt contracts, and the intensity within the core is strengthened. Reconstructions of the westerly winds since the last glacial maximum, however, have suggested that changes at a single site reflected shifts throughout the entire southern wind belt. Here we use sedimentological and pollen records to reconstruct precipitation patterns over the past 12,500 yr from sites along the windward side of the Andes. Precipitation at the sites, located in the present core and northern margin of the westerlies, is driven almost entirely by the wind belt, and can be used to reconstruct its intensity. Rather than varying coherently throughout the Holocene epoch, we find a distinct anti-phasing of wind strength between the core and northern margin over multi-millennial timescales. During the early Holocene, the core westerlies were strong whereas the northern margin westerlies were weak. We observe the opposite pattern in the late Holocene. As this variation resembles modern seasonal variability, we suggest that our observed changes in westerly wind strength can best be explained by variations in sea surface temperature in the eastern South Pacific Ocean.

Nd isotope composition of fossil fish teeth of ODP Hole 119-738B

We report an optimized method for extracting neodymium (Nd) from fossil fish teeth with a single-stage column (125 µl stem volume; LN Resin, Eichrom Industries, Darien Illinois) for isotopic analysis by multi-collector inductively coupled mass spectrometry (MC-ICMPS). Three reference materials (basalt: BCR-2, BHVO-2; phosphate: fossil bone composite) and splits of fossil fish teeth samples previously processed with existing two-stage column methods were processed using the single-stage column method. 143Nd/144Nd values of reference materials agree within error with published values, and the values for fish teeth correspond with sample splits processed with two-stage columns. Precision to ± ~0.23 epsilon-Nd was achieved for 30 ng Nd samples of reference materials, and Nd isotope measurements of fossil fish tooth sample replicates as small as 7 ng Nd were reproducible within long term instrumental uncertainty. We demonstrate the utility of the new method with the first high resolution Nd isotope record spanning the ~40.0 Ma middle Eocene Climatic Optimum, which shows an excursion of 0.65 epsilon-Nd during the peak warming at the study site (Ocean Drilling Program Leg 119, Site 738; 30 kyr sample spacing from 40.3 to 39.6 Ma). LN Resin is already used in standard methods for separating Nd, and Nd isotopes are routinely measured by MC-ICPMS with high efficiency inlet systems. Our innovation is a single, small volume LN Resin column for Nd separation. The streamlined approach results in a 10X increase in sample throughput.

Pollen record and age determination of a sediment core from the Kara Sea

AMS-14C dated sediment cores from the Ob and Yenisei estuaries and the adjacent inner Kara Sea were investigated to determine the siliclastic and organic carbon fluxes and their relationship to paleoenvironmental changes. The variability of sediment fluxes during Holocene times is related to the post-glacial sea-level rise and changes in river discharge and coastal erosion input. Whereas during the late/middle Holocene most of the terrigenous sediments were deposited in the estuaries and the areas directly off the estuaries, huge amounts of sediments accumulated on the Kara Sea shelf farther north during the early Holocene before about 9 Cal. kyrs. BP. The maximum accumulation at that time is related to the lowered sea level, increased coastal erosion, and increased river discharge due to the final stage of mountain deglaciation of the Putoran Massif. Increased supply of Yenisei-derived material indicated by peak magnetic susceptibility values probably occurred in climate-related pulses culminating near 11, 10, and 9 Cal. kyrs. BP. As sea level rose, the main Holocene depocenter migrated southward. Based on hydrogen index values and n-alkanes, the organic matter is predominantly of terrigenous origin. Maximum accumulation rates of 1.5 to more than 6 g/cm2/y occurred in the early Holocene sediments, suggesting more humid climatic conditions with an increased vegetation cover in the source area at that time. In general, high organic carbon accumulation rates characterize the estuaries and the inner Kara Sea as important sink for terrigenous organic carbon. A high-resolution record of Holocene variability of magnetic susceptibility (MS) in an AMS14C-dated sediment core from the northern Yenisei estuary may indicate natural variability of Arctic climate change and river discharge on a centennial to millenial time scale. Short-term maxima in MS probably related to warmer climate, enhanced precipitation, intensified weathering/erosion and increased river discharge, display a frequency of about 300 to 700 years.

(Table 1) Typical trace-fossil occurrences in DSDP Holes 56-436 and 56-435A

Trace fossils are in places abundant in cores from DSDP Leg 56 sites. They are particularly rich in the pelagic-clay sequence at Site 436. Some significant trace fossils, including Zoophycos, Teichichnus, Chondrites, rind and solid burrows, and pellet-armored rods, are described. The ichnofauna, except for pellet-armored rods in diatomaceous mudstone of the landward trench slope, is characterized by cosmopolitan bathyal to abyssal forms.

Calcium isotope fractionation in cultured, modern and fossil scleractinian coral skeleton

The present study investigates the influence of environmental (temperature, salinity) and biological (growth rate, inter-generic variations) parameters on calcium isotope fractionation (d44/40Ca) in scleractinian coral skeleton to better constrain this record. Previous studies focused on the d44/40Ca record in different marine organisms to reconstruct seawater composition or temperature, but only few studies investigated corals. This study presents measurements performed on modern corals from natural environments (from the Maldives for modern and from Tahiti for fossil corals) as well as from laboratory cultures (Centre Scientifique de Monaco). Measurements on Porites sp., Acropora sp., Montipora verrucosa and Stylophora pistillata allow constraining inter-generic variability. Our results show that the fractionation of d44/40Ca ranges from 0.6 to 0.1 per mil, independent of the genus or the environmental conditions. No significant relationship between the rate of calcification and d44/40Ca was found. The weak temperature dependence reported in earlier studies is most probably not the only parameter that is responsible for the fractionation. Indeed, sub-seasonal temperature variations reconstructed by d18O and Sr/Ca ratio using a multi-proxy approach, are not mirrored in the coral's d44/40Ca variations. The intergeneric variability and intrageneric variability among the studied samples are weak except for S. pistillata, which shows calcium isotopic values increasing with salinity. The variability between samples cultured at a salinity of 40 is higher than those cultured at a salinity of 36 for this species. The present study reveals a strong biological control of the skeletal calcium isotope composition by the polyp and a weak influence of environmental factors, specifically temperature and salinity (except for S. pistillata). Vital effects have to be investigated in situ to better constrain their influence on the calcium isotopic signal. If vital effects could be extracted from the isotopic signal, the calcium isotopic composition of coral skeletons could provide reliable information on the calcium composition and budget in ocean.