Diagenesis of siliceous particles in ODP Hole 114-699A

A number of neogenic opaline structures, not previously reported in the literature, as well as other neogenic phases are described from four Oligocene to Pliocene biosiliceous sediment samples from Hole 699A. The possible influence of microbes on the formation or the morphology of some of them is discussed. The samples, which are early Pliocene, early to middle Miocene, and late Oligocene (two) in age, were histologically fixed aboard ship upon retrieval. Investigations of the samples used SEM (with Edax/Tracor) and XRD methods. Diagenesis has affected all four samples, but the most extensive development of neoformed structures occurs in the Miocene and uppermost Oligocene samples, where microbial filaments (0.05 to 10 ?m long), microbial colonies, and siliceous microhemispheroids (0.2 to 0.7 µm diameter) were observed. The latter encrust filaments, diatoms, and detrital grains to varying degrees. Other neoformed structures include (1) flakes formed by coalesced microhemispheroids, some of which are guided by short, stubby filaments, which occur only in the Miocene and uppermost Oligocene samples, and (2) flakes characterized by smooth or microfissured surfaces, which grow on diatom frustules and in pore spaces and have a more widespread distribution. The XRD data indicate possible cristobalite formation in the Miocene and uppermost Oligocene samples; we believe that the neoformed opaline structures (encrusted filaments and microhemispheroids) may represent an early phase of opal-CT. The timing of neoformation of most of these features appears to have been fairly recent, continuing even at the time of sampling. There appears to be no direct correlation of this incipient, lower Miocene-uppermost Oligocene diagenetic layer and the pore-water chemistry profiles; a massive increase in shear strength in these sediments, however, may indicate some cementation. Smectite was identified by XRD as the most prominent clay mineral in these generally clay-poor sediments. Honeycombed minerals with filamentous edges, which could correspond to smectite, were observed with SEM in the pore spaces.

Organic facies variations in the Mesozoic South Atlantic DSDP Holes

Visual kerogen and total organic carbon determinations indicate that there are two periods of organic enrichment events in the Mesozoic sediments of the South Atlantic. The first period, from the Late Jurassic through the late Aptian, is recorded in sediments from the Falkland Plateau, the Cape Basin, and the Angola Basin. Apparently, salinity stratification in the restricted basin, coupled with rising sea level, led to bottom water anoxia and organic enrichment. The second event, from the late Albian to the Santonian period, is recorded in sediments from the Angola Basin and the Sao Paulo Plateau. It appears to have been caused by development of an anoxic oxygen minimum zone at midwater depths. Organic matter sedimentation in the Mesozoic South Atlantic is controlled by geologic, climatic, eustatic, and Oceanographic factors.

Foraminiferal, lithic, and isotopic changes across four major unconformities at DSDP Hole 80-548A

Sediment samples taken at close intervals across four major unconformities (middle Miocene/upper Miocene, lower Oligocene/upper Oligocene, lower Eocene/upper Eocene, lower Paleocene/upper Paleocene) at DSDP-IPOD Site 548, Goban Spur, reveal that coeval biostratigraphic gaps, sediment discontinuities, and seismic unconformities coincide with postulated low stands of sea level. Foraminiferal, lithic, and isotopic analyses demonstrate that environments began to shift prior to periods of marine erosion, and that sedimentation resumed in the form of turbidites derived from nearby upper-slope sources. The unconformities appear to have developed where a water-mass boundary intersected the continental slope, rhythmically crossing the drill site in concert with sea-level rise and fall.

Benthic foraminifera abundance data of sediment core GeoB7926-2

We present a high resolution, multiproxy study of the relationship between pelagic and benthic environments of a coastal upwelling system in the subtropical NE Atlantic Ocean. Marine sediments corresponding to late MIS3 to the Holocene in the radiocarbon dated core GeoB7926, retrieved off Mauritania (21°N) were analysed to reconstruct productivity in surface waters and its linkage to deep waters during the last 35 ka BP. High latitude cold events and changes in atmospheric and oceanographic dynamics influenced upwelling intensity over this time period. Subsequently, this caused changes in primary productivity off this low-latitude coastal upwelling locality. The benthic foraminiferal fauna displays four main community shifts corresponding to fundamental climatic events, first of all during late MIS3 (35-28 ka BP), secondly from 28 to 19 ka BP (including Heinrich event 2 and the LGM), thirdly within Heinrich event 1, the Bølling Allerød and the Younger Dryas (18-11.5 ka BP) and finally during the Holocene (11.5-0 ka BP). In particular, strong pelagic-benthic coupling is apparent in MIS 3, as demonstrated by increased primary productivity, indicated by moderate DAR and the dominance of benthic foraminiferal species which prefer fresh phytodetritus. A decline in upwelling intensity and nutrient availability follows, which resulted in a proportionately larger amount of older, degraded matter, provoking a shift in the benthic foraminifera fauna composition. This rapid response of the benthic environment continues with a progressive increase in upwelling intensity due to sea level and oceanographic changes and according high surface production during the LGM. During Heinrich event 1 and the Younger Dryas, extreme levels of primary production actually hindered benthic environment through the development of low oxygen conditions. After this period, a final change in benthic foraminiferal community composition occurs which indicates a return to more oxygenated conditions during the Holocene.

Calcareous nannofossils and planktonic foraminifera of ODP Hole 132-810C

The 136 m of calcareous oozes recovered in Hole 810C span the interval from upper Maastrichtian to middle Pleistocene. Three major hiatuses interrupt the sequence, with the topmost part of the Maastrichtian through the entire lower Paleocene, most of the lower Eocene, and the entire middle Eocene through most of the middle Miocene missing. Severe reworking and displacement affected the lower part of the succession from the Maastrichtian through the middle Miocene. Reworking and displacement gradually decreased in the upper portion. Calcareous nannofossil biostratigraphy enabled us to calibrate precisely the nearly complete magnetic reversal sequence of the Pliocene to the late Pleistocene. Two minor hiatuses detected by calcareous nannofossils across the Pliocene/Pleistocene boundary and in the upper lower Pleistocene, respectively, resulted in shortening of the Olduvai and Jaramillo Events within the Matuyama Chron of the magnetic reversal sequence.

Planktonic foraminifer stratigraphy of late Pliocene sediments from ODP Hole 167-1021C

This report is an initial investigation of the planktonic foraminifers from the late Pliocene of Ocean Drilling Program Hole 1021C. Planktonic foraminifer assemblages show fair preservation in many samples. Assemblages are quantitatively dominated by Globigerina bulloides, dextral coiling Neogloboquadrina atlantica, and Globorotalia inflata and alternate between cool temperate and subarctic conditions.

Physicochemical characteristics and protist occurrence at stations sampled in 2007/2008 in the eastern Beaufort Sea

This study documents, for the first time, the abundance and species composition of protist assemblages in Arctic sea ice during the dark winter period. Lack of knowledge of sea-ice assemblages during the dark period has left questions about the retention and survival of protist species that initiate the ice algal bloom. Sea-ice and surface water samples were collected between December 27, 2007 and January 31, 2008 within the Cape Bathurst flaw lead, Canadian Beaufort Sea. Samples were analyzed for protist identification and counts, chlorophyll (chl) a, and total particulate carbon and nitrogen concentrations. Sea-ice chl a concentrations (max. 0.27 µg/l) and total protist abundances (max. 4 x 10**3 cells/l) were very low, indicating minimal retention of protists in the ice during winter. The diversity of winter ice protists (134 taxa) was comparable to spring ice assemblages. Pennate diatoms dominated the winter protist assemblage numerically (averaging 77% of total protist abundances), with Nitzschia frigida being the most abundant species. Only 56 taxa were identified in surface waters, where dinoflagellates were the dominant group. Our results indicate that differences in the timing of ice formation may have a greater impact on the abundance than structure of protist assemblages present in winter sea ice and at the onset of the spring ice algal bloom.

Pollen records of 11 profiles from Wendland in northern Germany

1) Ingesamt 11 Profile aus sechs Mooren und Seen im Gebiet des Hannoverschen Wendlandes wurden pollenanalytisch untersucht. Die Ablagerungen umfassen den Zeitraum vom Beginn der Älteren Tundrenzeit bis zur Gegenwart. 2) Die Waldgeschichte des Hannoverschen Wendlandes weist teils Merkmale der atlantisch geprägten Gebiete Nordwestdeutschlands, teils solche des kontinental beeinflußten nordostdeutschen Raumes auf und nimmt damit eine Zwischenstellung ein. 3) Die Kiefer wandert zu Beginn der Allerödzeit ein, d.h. später als im mecklenburgisch-märkischen Gebiet und im mitteldeutschen Trockengebiet. Im Verlauf der Allerödzeit bildeten sich hier wie dort lichte Kiefern-Birken-Wälder aus. 4) In der Jüngeren Tundrenzeit fand zunächst nur eine geringe Auflichtung der Wälder statt, und die Kiefer überwog weiterhin. Erst im späteren Verlauf dieser stadialen Phase breitete sich die Birke aus und verdrängte die Kiefer. Der späte Rückgang der Kiefer stellt eine Parallele zu der Entwicklung in Südostmecklenburg und in der Altmark dar. Die Abgrenzung dieser Phasen in der Jüngeren Tundrenzeit ist durch eine 14C-Datierung gesichert. 5) Noch im Atlantikum ähneln die Diagramme aus dem Gartower Talsandgebiet im Osten des Wendlandes in ihren hohen Kiefernanteilen denen der Sandergebiete in Brandenburg. Die Diagramme aus dem Moränengebiet des westlichen Wendlandes schließen dagegen mehr an die der östlichen Lüneburger Heide und des Hamburger Gebietes an. Dieser Unterschied wird auf edaphische Unterschiede zurückgeführt. 6) Seit dem frühen Subboreal glich auch die Vegetation des Gartower Gebietes mehr den buchenarmen Waldgesellschaften auf sauren Sandböden, wie sie im atlantischen Westen vorkommen. Die Kiefern sind fast ganz aus dem Waldbild verschwunden, wobei der rasche Rückgang zu Beginn des Subboreals sicher zu einem wesentlichen Teil vom Menschen beeinflusst worden ist. Die anschließende kiefernarme Zeit dauerte im gesamten Wendland bis zum Beginn der Kieferaufforstungen in der Neuzeit. 7) In allen untersuchten Diagrammen ist etwa seit dem Subboreal eine Besiedlung nachzuweisen. Diese muß im Osten des Wendlandes intensiver gewesen sein als im Westen. Es lassen sich Phasen geringer und intensiver Besiedlung nachweisen. 8) Seit Beginn des Subboreals ist das Waldbild schon so stark vom Menschen beeinflusst, dass die Ausbreitungsgeschichte der Laubwaldarten nicht ohne Berücksichtigung der Siedlungsphasen diskutiert werden kann. Besonders im Westen bestand eine ausgedehnte Lindenphase, die durch eine Siedlungszeit (Bronzezeit) beendet wurde. Beim folgenden Rückgang der Siedlungsintensität breitet sich bevorzugt die Hainbuche aus, die dann bei der nächsten Besiedlungsphase (Eisenzeit) zurückging. Erst danach erfolgte die maximale Rotbuchenausbreitung, die nur im Westteil des Wendlandes bedeutende Ausmaße zeigte, während im Ostteil rot- und hainbuchenreiche Eichenwälder entstanden. 9) Seit Beginn der mittelalterlichen Besiedlung ist dann der Eingriff des Menschen so stark gewesen, dass die edaphisch bedingten Unterschiede zwischen Moränen- und Sandergebieten im Pollenspektrum verwischt wurden. Sowohl die buchenreichen Wälder des westlichen als auch die buchenarmen Wälder des mittleren und des östlichen Teilgebietes müssen zu fast reinen Eichenwäldern geworden sein. 10) Calluna-Heiden sind im östlichen Wendland schon in vorgeschichtlicher Zeit nachzuweisen. Im Mittelalter und in der Neuzeit treten sie im gesamten Wendland auf. Etwa im 18. und 19. Jahrhundert war die Ausdehnung der Heideflächen am größten. Erst danach wurden sie im Zuge der Kiefernaufforstungen bis auf geringe Reste verdrängt. 11) Während in der spätglazialen Vegetation Juniperus auftritt, ist der Wacholder sowohl in vorgeschichtlicher als auch in geschichtlicher Zeit - im Gegensatz zur Lüneburger Heide - wohl niemals ein Bestandteil der anthropogenen Calluna-Heiden gewesen.

Palynology on sediment profile Tso Kar in Ladakh

Palynological investigation of a 410 cm long core section from Tso Kar (33°10'N, 78°E, 4527 m a.s.l.), an alpine lake situated in the arid Ladakh area of NW India at the limit of the present-day Indian summer monsoon, was performed in order to reconstruct post-glacial regional vegetation and climate dynamics. The area was covered with alpine desert vegetation from ca. 15.2 to 14 kyr BP (1 kyr=1000 cal. years), reflecting dry and cold conditions. High influx values of long-distance transported Pinus sylvestris type pollen suggest prevailing air flow from the west and northwest. The spread of alpine meadow communities and local aquatic vegetation is a weak sign of climate amelioration after ca. 14 kyr BP. Pollen data (e.g. influx values of Pinus roxburghii type and Quercus) suggest that this was due to a strengthening of the summer monsoon and the reduced activity of westerly winds. The further spread of Artemisia and species-rich meadows occurred in response to improved moisture conditions between ca. 12.9 and 12.5 kyr BP. The subsequent change towards drier desert-steppe vegetation likely indicates more frequent westerly disturbances and associated snowfalls, which favoured the persistence of alpine meadows on edaphically moist sites. The spread of Chenopodiaceae-dominated vegetation associated with an extremely weak monsoon occurred at ca. 12.2-11.8 kyr BP during the Younger Dryas interstadial. A major increase in humidity is inferred from the development of Artemisia-dominated steppe and wet alpine meadows with Gentianaceae after the late glacial/early Holocene transition in response to the strengthening of the summer monsoon. Monsoonal influence reached maximum activity in the Tso Kar region between ca. 10.9 and 9.2 kyr BP. The subsequent development of the alpine meadow, steppe and desert-steppe vegetation points to a moderate reduction in the moisture supply, which can be linked to the weaker summer monsoon and the accompanying enhancement of the winter westerly flow from ca. 9.2 to 4.8 kyr BP. The highest water levels of Tso Kar around 8 kyr BP probably reflect combined effect of both monsoonal and westerly influence in the region. An abrupt shift towards aridity in the Tso Kar region occurred after ca. 4.8 kyr BP, as evidenced by an expansion of Chenopodiaceae-dominated desert-steppe. Low pollen influx values registered ca. 2.8-1.3 kyr BP suggest scarce vegetation cover and unfavourable growing conditions likely associated with a further weakening of the Indian Monsoon.

Phytoplankton in the surface desalted lens of the Kara Sea

Phytoplankton of a surface strongly desalinated water lens was investigated on the basis of materials collected during Cruise 57 of R/V Akademik Mstislav Keldysh in September 2007. The lens with salinity <18 psu had area of ca. 19000 sq. km and was located in the northwestern part of the Kara Sea near the eastern coast of Novaya Zemlya. It was a specific biotope that had been isolated from surrounding waters for more than three months. In the investigated area 66 algae species were identified. The maximal species diversity was found in the upper layers of the desalinated lens, where species number was 1.5 to 3 times higher than in other parts of the water column. Phytoplankton abundance in the upper layers of the lens was 1.5 to 4.5 times higher than in its lower part and generally higher than below the picnocline. Diatoms were the most abundant group in the upper layers of the lens, while flagellates dominated in the subpicnocline part of the water column. Maximal values of phytoplankton biomass were observed everywhere in the upper layers of the lens, where they were 1.2 to 3.7 times higher than in the lower part of the lens and 1.3 to 7.2 times higher than in the layer below the picnocline. Dinoflagellates generally gave the most contribution to total phytoplankton biomass. Phytoplankton of the desalinated surface lens in the northwestern part of the Kara Sea by its composition and quantitative parameters had the nearest resemblance to a phytocenosis that we observed two weeks later at a shallow desalinated shelf closely adjacent to the Ob estuary.

Eocene and Oligocene radiolarian biostratigraphy from the Southern Ocean

Eocene-Oligocene radiolarians from Ocean Drilling Program Sites 699, 702, and 703, Leg 114 of the Subantarctic Atlantic were examined in order to extend the tripartite zonation for the recovered cores based on results of similar analysis of Leg 120 submarine sediments from the Indian Ocean. Correlation of the two oceans is made by examining 23 biohorizons and the three zones, Eucyrtidium spinosum, Axoprunum irregularis, and Lychnocanoma conica, in ascending stratigraphic order. One new species, Eucyrtidium nishimurae, is described.

Pollen analysis of a sediment profile from Gabelsee in Germany

The article shows that pollen analysis plays an important role in the prediction of potential settlement areas and, furthermore, can offer a crude determination of settlement duration. Especially when the archaeological data fails to offer a possibility of dating, pollen analysis in connection with 14C can importantly broaden the knowledge base. As in the present case, the results of the Archaeo-Prognosis mapping and the pollen analysis of the Gabelsee are compared and, within this vicinity, confirmend. = Der Beitrag zeigt, dass die Pollenanalyse eine wichtige Rolle für die Vorhersage von potenziellen Siedlungsflächen spielen und darüber hinaus eine grobe Berechnung der Siedlungsdauer bieten kann. Insbesondere wenn die archäologische Datenbasis keine genaue Datierung zulässt, ermöglicht die Pollenanalyse in Verbindung mit der 14C-Datierung eine wichtige Erweiterung der Kenntnisse. Im vorliegenden Fall konnten die Ergebnisse der Archäoprognosekarte mit denjenigen der Pollenanalyse des Gabelsees verglichen und für diesen lokalen Raum bestätigt werden.

Jurassic microfossils of DSDP Hole 79-547B

The first marine incursion of the incipient North Atlantic Ocean is recorded in the uppermost Triassic to Lower Jurassic sequence of DSDP Site 547 off central Morocco. A lithologic change from continental red beds below to slope breccias and hemipelagic carbonates above indicates that a carbonate ramp was probably established by Sinemurian time along the Moroccan continental margin and that subsidence in the adjacent basin was rapid in the early phases of continental rift. Foraminifers recovered from the Liassic (Sinemurian-Pliensbachian) basinal deposits are diverse and well preserved. The faunas are compositionally similar to contemporaneous neritic assemblages of Europe and the Grand Banks of Newfoundland. The Middle Jurassic in Hole 547B is characterized by regressive deposits that are poor in foraminifers. The major Late Jurassic "Atlantic" transgression is again represented by basinal deposits consisting of limestone breccias and pelagic carbonates. Foraminifers recovered from this interval are transitional between Late Jurassic assemblages reported from deep-sea deposits in the North Atlantic and typical Late Jurassic neritic assemblages of Europe. The Late Jurassic assemblages of Hole 547B are primarily dominated by nodosariids and spirillinids with moderate abundances of simple arenaceous forms. Nonreticulate epistominids occur very rarely in the Upper Jurassic of Hole 547B. It is tentatively suggested that these represent upper bathyal assemblages.

Biogenic and mineral composition and foraminiferal stratigraphy of sediment cores obtained in northern Germany

The Ratekau boring ended in clays of the so-called Asterigerina-Zone; these clays have shallow-water features in the uppermost samples. The clays are overlain by deep-water clays with pteropods; this formation is split into two parts by a shallow-water deposit. The fossiliferous series ends upward in sandy deposits with shallow-water fossils. The question is raised whether the two deep-water deposits might correspond to the Lower Doberg Beds (Eochattian) and the Upper Doberg Beds (Neochattian) at the Doberg hill, closer to the rim of the basin. All fossiliferous samples from this boring are thought to be of Late Oligocene age; the boundary towards the Middle Oligocene, however, could not be ascertained. The Vaale boring ended in rather typical Septaria clay of the Middle Oligocene. This clay is capped by some metres of unfossiliferous glauconite clays, which in turn are overlain by silts and silty clays with planktonic fossils identical to those found at Dingden locality. These deposits are tentatively dated as Early Miocene. The next higher series of samples consists of sands and clays deposited in shallower waters. They contain a rich fauna of benthic molluscs, which, according to the current notion in stratigraphy, would have a Reinbek Age. In addition, they contain a set of planktonic fossils which differs from the 'Lower Miocene' assemblages. These sands and clays are overlain by a thick series of marine sands very poor in fossils. Finally, four metres of clay with foraminifera, having Younger Miocene affinities, form the top of the fossiliferous sequence. The borings at Wulksfelde and Langenhorn were not far apart and their sediments are easily correlated. Both wells start below in continental 'Lignite Sands' and contain overlying shallow water sands and clays. These yielded Hemmoor benthic mollusca, supposed to indicate Lower Miocene in the relevant literature; however, we encountered their planktonic foraminifera in the uppermost Miocene as well. The same planktonic species were found in all samples of both borings. These deposits under discussion furthermore contain a particular pteropod species. They are overlain by a thick series of gypsiferous clays, with scarce fossils. The uppermost fossiliferous clays (probably Langenfelde Age) contain another pteropod species, not met with in other samples. The discrepancies between the plankton zonation and the traditional subdivision according to benthic molluscs in the borings of Vaale, Wulksfelde and Langenhorn (and in samples from Twistringen, Dingden and Antwerp localities as well) renders the time-stratigraphic value of the denominations Reinbek and Hemmoor rather doubtful. The samples of the Westerland boring can be placed in the Gram and Sylt stages of local chronostratigraphy on the strength of the Astarte series established by HINSCH. The Gram samples contain a typical pteropod species; both groups of samples contain the same planktonic foraminifera as the borings Wulksfelde and Langenhorn. Our material did not bring the problem of the Miocene-Pliocene boundary in this region any closer to a solution. In conclusion, it can be claimed that this investigation provides strong arguments that the usual recognition of Hemmoor and Reinbek does not correspond to well-defined chronostratigraphical units. A better chronostratigraphic subdivision has to be based on the examination of many more samples, and on a better understanding of the paleoecology of the fossils involved.

Coccolithosphores and fossil organic compounds of sediment core MD01-2444

This study analyzes coccolithophore abundance fluctuations (e.g., Emiliania huxleyi, Gephyrocapsa specimens, and Florisphaera profunda) in core MD01-2444 sediment strata retrieved at the Iberian Margin, northeastern Atlantic Ocean. Coccolithophores are calcareous nannofossils, a major component of the oceanic phytoplankton, which provide information about past ecological and climatological variability. Results are supported by data on fossil organic compounds (sea surface temperatures, alkenones, and n-hexacosan-1-ol index) and geochemical analyses (benthic d13Ccc and planktonic d18Occ isotopes). Three scenarios are taken into account for this location at centennial-scale resolution over the last 70,000 years: the Holocene and the stadial and interstadial modes. The different alternatives are described by means of elements such as nutrients; upwelling phenomena; temperatures at surface and subsurface level; or the arrival of surface turbid, fresh, and cold waters due to icebergs, low sea level, increased aridity, and dust. During the Holocene, moderate primary productivity was observed (mainly concentrated in E. huxleyi specimens); surface temperatures were at maxima while the water column was highly ventilated by northern-sourced polar deep waters and warmer subsurface, nutrient-poor subtropical waters. Over most of the last glacial stadials, surface productivity weakened (higher F. profunda and reworked specimen percentages and lower diunsaturated and triunsaturated C37 alkenones); the arrival of cold Arctic surface waters traced by tetraunsaturated C37 peaks and large E. huxleyi, together with powerful ventilated southern-sourced polar deep waters, disturbed, in all likelihood, the delicate vertical equilibrium while preventing significant upwelling mixing. Finally, during the last glacial interstadials (lower F. profunda percentages, nonreworked material, and higher diunsaturated and triunsaturated C37 alkenones) a combined signal is observed: warm surface temperatures were concurrent with generally low oxygenation of the deep-sea floor, moderate arrival of northern-sourced deep waters, and subsurface cold, nutrient-rich, recently upwelled waters, probably of polar origin; these particular conditions may have promoted vertical mixing while enhancing surface primary productivity (mainly of Gephyrocapsa specimens).