Middle Eocene to Pleistocene calcareous nannofossils of ODP Leg 113 holes

Long sequences of Upper Cretaceous through Quaternary sediments rich in calcareous and siliceous microfossils were recovered at Ocean Drilling Program Sites 689 and 690 on Maud Rise off East Antarctica. These sites have become the southernmost anchor in the Atlantic Basin for bio-, magneto-, chemostratigraphic, and paleobiogeographic studies. ODP Sites 692 and 693 on the Weddell Sea margin of East Antarctica and Site 696 on the South Orkney microcontinent of West Antarctica yielded calcareous nannofossils within some stratigraphic intervals. Sites 691, 692, 694, 695, and 697 did not recover Cenozoic calcareous nannofossils. Calcareous nannofossil biostratigraphy suggests a major hiatus across the Paleogene/Neogene boundary at Sites 689 and 690, and two additional hiatuses in the middle Eocene-lower Oligocene section at Site 690. Correlation with magnetostratigraphy reveals: the last occurrence (LO) of Reticulofenestra umbilica at Maud Rise is over 1 m.y. younger than that at the middle-latitude sites; the LO of Isthmolithus recurvus is synchronous in the middle-latitude and high-latitude areas (about 34.8 Ma); Reticulofenestra oamaruensis ranges from 38.0 to 36.0 Ma at Maud Rise; Reticulofenestra reticulata has a shorter range at Maud Rise (42.1 to 38.9 Ma) than at the middle-latitude DSDP Site 516; the range of Chiasmolithus oamaruensis is diachronous over different latitudes; and the LO of Chiasmolithus solitus is a good datum at 41.3 Ma from 30°S to 65°S in the South Atlantic Ocean. Comparison of calcareous nannofossil abundances in a latitudinal transect shows: Reticulofenestra bisecta is a temperate-water species and its LO, which crosses below that of Chiasmolithus altus at Maud Rise, is not applicable for the Paleogene/Neogene boundary in high southern latitude areas; Clausicoccus fenestratus is rare or absent at Maud Rise and can not be used as a marker; Coccolithus formosus is a warm-water species which disappeared earlier toward higher latitudes. Calcareous nannofossil assemblages indicate that by at least the middle Eocene, surface water temperatures became considerably lower in the high southern latitudes than in the middle-latitude areas and that there have been more extreme cold events in the high latitudes during the Neogene. Bicolumnus ovatus n. gen., n. sp. is proposed in this paper.

Calcareous nannofossils in sediments of the southeast Pacific

This study provides the first detailed documentation of calcareous nannofossil assemblages in Eocene subantarctic Eltanin piston cores recovered from the southeast Pacific Ocean. These Eltanin cores are important because they have been reported to contain ice-rafted quartz. The present study confirms early and middle Eocene ages for the cores and dates them more precisely using calcareous nannofossils. Semiquantitative study of the nannoflora indicates that they are of a warmer water character than those from the higher latitudes (such as Falkland Plateau, Maud Rise, and Kerguelen Plateau). This study concludes that it is unlikely for the ice-rafted quartz in the Eocene sections to be downcore contaminants from the overlying Neogene sediment and suggests that the grains are probably the result of Eocene ice-rafting from Antarctica when the Drake Passage was closed and water circulation patterns were different from those of today.

Macrobenthos from the Novaya Zemlya Trough, Kara Sea

During Cruise 54 of R/V Akademik Mstislav Keldysh macrobenthos of the Novaya Zemlya Trough was studied with use of a Sigsby trawl along a submeridional transect near 75°30'N at depth range from 68 to 362 m. In total 140 species of bottom animals were found. Relative role of taxons was assessed using three parameters: abundance, biomass, and energy flow. Similarity of the parameters was used for comparison of samples. New material greatly contributes to data on composition of fauna and structure of communities of the studied region. It was revealed that small scyphozoid polyps and sipunculoids play an important role in the trough's community. Presence of a community dominated by Ophiocten sericeum (with important role of small bivalves) was revealed for the first time not only at the eastern by also at the western slope of the Novaya Zemlya Trough. The sharpest changes in composition and structure of the bottom community were confined to a zone of transition from the trough floor to the slope. These changes are determined by specificity of the macrorelief (of the floor and slope), composition of ground (soft brown silts abound in rhizopods and dense gray silts with admixture of pebbles), and possibly by hydrodynamic processes near the bottom.

Pleistocene and late Miocene Calcareous nannofossil biostratigraphy of ODP Hole 150-905A

Continental rise Site 905 yielded upper Miocene and Pliocene uniform hemipelagic mud (a contourite) from approximately 215 to 540 meters below seafloor. The nannofossil biostratigraphy of this interval was reexamined using closely spaced samples from core interiors. Additionally, total nannofossil abundances and dominant species and species group abundances were determined to evaluate the potential of this section for extracting sequence stratigraphic information. The data indicate that the putative hiatuses at the end of the late Pliocene (Zones NN17 and NN18) and in the early Pliocene (Zones NN13 and NN14) probably are condensed intervals, but the base of the late Miocene is almost certainly marked by an unconformity. Judging from carbonate content and sedimentation rate both, nannofossil abundance may be governed by carbonate dissolution or by siliciclastic dilution. Consequently, condensed sections cannot be identified by the abundance of pelagic component in the sediment alone, as is possible in equivalent age Gulf of Mexico sediments. Where nannofossil preservation is adequate in consecutive samples, as in the early Pliocene and latest late Miocene, total nannofossil abundance fluctuates regularly and with a periodicity of less than 105 yr, which suggests that dilution of the pelagic component occurred with a frequency probably related to astronomical forcing.

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.

Calcareous nannofossil biostratigraphy of the central East Pacific Rise

During Leg 92 of the Deep Sea Drilling Project, sediments containing calcareous nannofossils of latest Oligocene to Holocene age were recovered from 14 holes at six sites (597 to 602) along the East Pacific Rise. The combined sections yield a virtually complete record for the region, with a compressed upper Miocene to Pleistocene interval. The nannofossil content of 14 U.S.N.S. Eltanin piston cores from the study area were also examined in order to supplement data generated during Leg 92. Two taxonomically new combinations are presented: Sphenolithus umbellus and Pontosphaera segmenta. Assemblages of calcareous nannofossils juxtaposed in reversed stratigraphic order within the upper Miocene provide strong evidence for downslope transport of sediments along the East Pacific Rise during the Messinian. Narrow bands of dark metalliferous sediment of coccolith Zone CN8b alternate with normal light-colored, in situ, pelagic sequences of Zone CN9b. This may indicate more vigorous bottom current activity between 5.40 and 6.70 Ma.

Calcareous nannofossils from the Sumisu Rift and Izu-Bonin Forearc Basin

During Ocean Drilling Program Leg 126, we recovered three expanded Pleistocene sections from the active backarc rift (Sumisu Rift) and three expanded Oligocene-Miocene sections from the forearc basin of the Izu-Bonin volcanic island arc. Quantitative analysis of the Pleistocene nannofossils revealed five major assemblages between 0 and LO Ma: Assemblage 1 (Holocene-0.085 Ma) contains dominant Emiliania huxleyi; Assemblage 2 (ca. 0.085-0.275 Ma) contains dominant small Gephyrocapsa and common E. huxleyi and Gephyrocapsa oceanica; Assemblage 3 (ca. 0.275-0.6 Ma) contains dominant Gephyrocapsa caribbeanica; Assemblage 4 (ca. 0.6-0.9 Ma) contains a peak abundance of small Gephyrocapsa in the middle part, and dominant occurrences of two types of G. caribbeanica in the lower and upper parts; and Assemblage 5 (ca. 0.9-1.0 Ma) contains dominant small Gephyrocapsa and common G. caribbeanica and Reticulofenestra asanoi. These assemblages are largely synchronous with similar assemblages recognized from tropical and subtropical regions, and can be used for finer subdivision of the Pleistocene than that based on standard Pleistocene nannofossil datums. The Oligocene-Miocene sections contain several hiatuses: up to 3 m.y. may be missing from the uppermost Oligocene (Zone CP19) at Sites 792 and 793; all of Zone CN2 is missing at Sites 792 and 793; part of Zone CN3 and all of Zone CN4 are missing at Site 792. Biochronology of several nannofossil datums at Leg 126 sites indicate that Sphenolithus distentus, Sphenolithus ciperoensis, Cyclicargolithus floridanus, and Discoaster kugleri have diachronous occurrences compared with other sites in the western Pacific Ocean and Philippine Sea.

Calcareous nannofossils from ODP Leg 105 holes

Neogene calcareous nannofossils were examined from 10 holes at three sites cored during ODP Leg 105. Sediment recovered in Baffin Bay at Site 645 is virtually barren of calcareous nannofossils, with the exception of a sparse lower Miocene assemblage. Sites 646 and 647 in the Labrador Sea contain upper Miocene to Holocene sediments having numerous barren intervals. Upper Pleistocene fossil coccolithophorid floras in the Labrador Sea indicate alternations of cold subpolar with transitional (subpolar/subtropical) assemblages. Extreme variations in the abundance of Coccolithus pelagicus were observed at Sites 646 and 647. These variations are correlated with stable isotopic data to interpret oceanographic responses to warming and cooling trends. The climatic history indicated by the changes of these assemblages closely approximates the past climatic fluctuations recorded in other North Atlantic cores. One new taxon, Discoaster bergenii, is described.

Middle Eocene-lower Miocene calcareous nannofossil magnetobiochronology of ODP Holes 699A and 703A in the subantarctic South Atlantic

The distribution of calcareous nannofossils is documented for the middle Eocene through lowermost Miocene cores from Ocean Drilling Program Holes 699A and 703A in the subantarctic South Atlantic. The detailed nannofossil biostratigraphies established, in combination with published magnetostratigraphic data, have provided a fairly detailed age model for each hole. This study suggests that the middle Eocene through lowermost Miocene section from Hole 699A is virtually complete. A major hiatus has been identified in Hole 703A in the earliest Oligocene, coincident with n abrupt cooling in the Southern Ocean. Comparison of the nannofossil datum ages calibrated with magnetostratigraphy in the two holes with those from mid and southern high latitudes demonstrates synchroneity or diachroneity for the following nannofossil datums: (1) The last occurrence (LO) of Reticulofenestra bisecta is a consistent and reliable biostratigraphic marker for the Oligocene/Miocene boundary from mid- to high latitudes but not in extreme high latitudes; (2) similarly, the LO of Chiasmolithus altus has a consistent age of about 26.8 Ma in the Southern Ocean except in the extreme high latitudes where the datum appears to be substantially younger; (3) the LO of Reticulofenestra umbilica is about 32.9 Ma in the Southern Ocean; (4) the LO of Isthmolithus recurvus is reliable and consistent from mid through high latitudes and correlates with the lower part of Subchron C12R (~34.4 Ma); (5) the LO of Reticulofenestra oamaruensis has a consistent age of 36.0 Ma at all four Southern Ocean sites that have yielded a lower Oligocene magnetostratigraphy; (6) the first occurrence (FO) of R. oamaruensis is at 38.4 Ma in the Southern Ocean; and (7) the FO of I. recurvus shows some age variations from mid to high latitudes and the age range is 38.5-39.0 Ma at the five Southern Ocean sites.

Distribution of diatoms in surface sediments and some limnological characteristics of studied lakes in the Siberian arctic

The investigation of the species composition and ecology of diatoms of modern bottom sediments in water bodies of arctic polygonal tundra in three subregions of North Yakutiya has been carried out. As a result, 161 taxons of diatoms were determined; the determinant role of the depth, conductivity, pH of the water, and geographic latitude in their distribution was confirmed, and two complexes of species with respect to the leading abiotic factors were distinguished. The diatoms of the first complex prefer shallow water bodies of high latitudes with neutral and slightly alkaline water and relatively high conductivity. The second complex is confined to the water bodies of lower latitudes with small conductivity, as well as neutral and slightly acidic water.

Nannofossil and stable isotope record across the Paleocene/Eocene Thermal Maximum in ODP Hole 183-1135A

The Paleocene/Eocene Thermal Maximum (PETM, ca. 55 Ma) is an abrupt, profound perturbation of climate and the carbon cycle associated with a massive injection of isotopically light carbon into the ocean-atmosphere system. As such, it provides an analogue for understanding the interplay between phytoplankton and climate under modern anthropogenic global-warming conditions. However, the accompanying enhanced dissolution poses uncertainty on the reconstruction of the affected ecology and productivity. We present a high-resolution record of bulk isotopes and nannofossil absolute abundance from Ocean Drilling Program (ODP) Site 1135 on the Kerguelen Plateau, Southern Indian Ocean to quantitatively constrain for the first time the influence of dissolution on paleoecological reconstruction. Our bulk-carbonate isotope record closely resembles that of the classic PETM site at ODP Site 690 on the opposite side of the Antarctic continent, and its correlation with those from ODP Sites 690, 1262 and 1263 records allows recognition of 14 precessional cycles upsection from the onset of the carbon isotopic excursion (CIE). This, together with a full range of common Discoasteraraneus and an abundance crossover between Fasciculithus and Zygrhablithusbijugatus, indicates the presence of the PETM at Site 1135, a poorly known record with calcareous fossils throughout the interval. The strong correlation between the absolute abundances of Chiasmolithus and coccolith assemblages reveals a dominant paleoecological signal in the poorly preserved fossil assemblages, while the influence of dissolution is only strong during the CIE. This suggests that r-selected taxa can preserve faithful ecological information even in the severely-altered assemblages studied here, and therefore provide a strong case for the application of nannofossils to paleoecological studies in better-preserved PETM sections. The inferred nannoplankton productivity drops abruptly at the CIE onset, but rapidly increases after the CIE peak, both of which may be driven by nutrient availability related to ocean stratification and vertical mixing due to changed sea-surface temperatures.

Post-glacial pollen record from Yorkshire

The stratigraphy and pollen analysis of the deposits show that this is a lake basin which during the Late-glacial period was partially filled by lake clays and muds. One of the main interests of the pollen diagrams lies in the division of zone i into three suh-zones showing a minor climatic oscillation which seems to be comparable with the Boiling oscillation of northern Europe. During Post-glacial time the greater part of the deposits has been muds but on one side a fen developed which in early zone VI was sufficiently dry to support birch and pine wood. Later in zone VI the water table must have risen slightly because the fen peats were gradually covered by a rather oxidized mud suggesting that the fen became replaced by a shallow swamp with a widely fluctuating water table. In the Atlantic period the basin was reflooded and the more central deposits were covered by a layer of mud. Later in the central region, swamp and eventually Sphagnum bog communities developed. The whole area is now covered by a sihy soil and forms a flat meadowland.

Oligocene-Miocene calcareous nannofossils in ODP Leg 149 holes

During Ocean Drilling Program (ODP) Leg 149, five sites were drilled on the Iberia Abyssal Plain in the northeastern Atlantic Ocean. Both Mesozoic and Cenozoic sediments were recovered. Oligocene to Miocene sediments were cored at deepwater Sites 897, 898, 899, and 900. Except for a few intervals, occurrences of generally abundant and well-preserved calcareous nannofossils suggest that the deposition of the turbidite-type sediments occurred above the calcite compensation depth (CCD). One major unconformity in the middle late Miocene is present. Detailed quantitative analyses of calcareous nannofossils are used to determine the changes occurring among the nannoflora in relation to sea-level variation. A succession of 89 biohorizons from the early Oligocene to the late Miocene are defined by combining the biostratigraphic results of the four sites studied in the Iberia Abyssal Plain. One new genus and eight new species are described: Camuralithus, Camuralithus pelliculatus, Ericsonia detecta, Helicosphaera limasera, Sphenolithus akropodus, Sphenolithus aubryae, Sphenolithus cometa, Reticulofenestra circus, and Syracosphaera lamina. Two new variations and seven new combinations are also introduced.