Calcareous nannofossils of ODP Holes 114-699A and 114-700B

Ocean Drilling Program (ODP) Leg 114 recovered nannofossil-bearing sediments from seven sites in the high latitudes of the South Atlantic Ocean. Cretaceous sections were recovered from Sites 698 and 700, located on the Northeast Georgia Rise and its lower flanks, respectively. These contain distinctive high-latitude nannofossil floras similar to those from high-latitude areas of the Northern Hemisphere. Most of the biostratigraphic datums used to date the upper Campanian to Maestrichtian interval appear to lie at approximately the same level in both hemispheres. The FAD of Nephrolithus frequens is confirmed to be diachronous with an earlier occurrence in high latitudes. The LAD of Monomarginatus primus n. sp. also appears to be diachronous with a later LAD in the high latitudes of the Southern Hemisphere. Fossiliferous Paleocene to lowermost Miocene sediments were recovered at all seven sites, from the Northeast Georgia Rise in the west to the Meteor Rise in the east. These nannofossil floras, although restricted in diversity and only poorly preserved, are sufficiently distinctive to allow the recognition of 19 zones and three subzones, which are used to date and correlate the cores recovered. Only Site 704 on the Meteor Rise yielded a substantial section of Miocene to Quaternary nannofossil-rich sediments. The nannofossil floras of this section are of very low diversity, with usually fewer than eight species present. Some stratigraphic ranges of important biostratigraphic datum species are observed to be different in the high-latitude sections from those recorded from low-latitude areas. The LAD of Reticulofenestra bisecta, when calibrated by magnetostratigraphy, appears to occur earlier in Hole 699A (within Chron C6CR) than in Hole 703A and possibly Hole 704B and in other published accounts of lower latitude sites in the South Atlantic. The FAD of Nannotetrina fulgens/N. cristata appears to occur later in Hole 702B (Chron C20R) than it does in other published accounts of lower latitude sites in the South Atlantic. Diachroneity is also suspected in the stratigraphic ranges of Chiasmolithus solitus and Chiasmolithus oamaruensis, although poor magnetostratigraphic results through the critical interval prevent confirmation of this. Differences in the relative stratigraphic ranges of lsthmolithus recurvus and Cribrocentrum coenurumlC. reticulatum at Sites 699 and 703 are noted. These possibly suggest warmer surface waters on the eastern side (Site 703) of the middle to late Eocene South Atlantic than those on the western side (Site 699). The diversities of the nannofossil floras and the presence of the warm-water genera Discoaster, Sphenolithus, Helicosphaera, and Amaurolithus reflect the changing surface water temperatures throughout the Cenozoic. Warmer periods are inferred for the late Paleocene to early middle Eocene, late middle Eocene to late Eocene, latest Oligocene to earliest Miocene, and possibly the Pliocene. Colder periods are inferred for the middle Eocene, most of the Oligocene, and the Miocene. Dramatic changes in the nannofossil floras of the Pleistocene of Site 704 are thought to reflect a rapidly changing environment. Monomarginatus primus, a new species from the Upper Cretaceous strata of Hole 700B, is described.

Eocene-Oligocene nannofossils from the Labrador Sea

During Ocean Drilling Program (ODP) Leg 105, a thick sequence of lower Eocene to lower Oligocene sediments was recovered from Hole 647A in the southern Labrador Sea. These sediments contain diverse, well-preserved, high-latitude calcareous nannofossil flora. The nannofossil biostratigraphy of the hole indicates the presence of a minor hiatus between Zones NP 16 and NP 17 in the upper middle Eocene and a barren interval separating Zones NP 13 and NP 15. Species abundance is highest within the lower to middle Eocene and starts to decline near the base of the upper Eocene. No major change in the nannoflora was observed across the Eocene/Oligocene boundary, although a slight decrease in species abundance was recorded. The Paleogene calcareous nannofossils of nearby DSDP Site 112 were reexamined and compared with those of Site 647. Several cores were reassigned to different nannofossil zones. The calcareous nannoflora are dominated by high-latitude indicative species and also exhibit a high diversity, which suggests the influence of more temperate water masses in this region during Eocene and Oligocene time. One new subspecies from the middle Eocene, Sphenolithus furcatolithoides labradorensis, is described.

Cretaceous and Paleogene calcareous nannofossils from ODP Leg 123

Two of five holes drilled at two separate sites during Leg 123 of the Ocean Drilling Program intersected thick and relatively complete sections of Upper Cretaceous-Paleogene nannofossiliferous sediments. Although dominated by turbidite deposition in the upper part, Hole 765C contains a thick and relatively complete Albian-Oligocene section, including a particularly thick Aptian interval, with abundant and fairly well-preserved nannofossils. Several unconformities are confidently interpreted in this section that span much of the Santonian, late Campanian, Maestrichtian, late Eocene, and early Oligocene. Hole 766A contains a thick and relatively complete Albian-lower Eocene section having generally abundant and well-preserved nannofossils. Several unconformities also have been identified in this section that span much of the Coniacian, early Campanian, Maestrichtian, and late Eocene through early Pliocene. The chronostratigraphic position and length of all these unconformities may have considerable significance for reconstructing the sedimentary history and for interpreting the paleoceanography of this region. A particularly thick section of upper Paleocene-lower Eocene sediments, including a complete record across the Paleocene/Eocene boundary, also was cored in Hole 766A that contains abundant and diverse nannofossil assemblages. Although assemblages from this section were correlated successfully using a standard low-latitude zonation, difficulties were encountered that reduced biostratigraphic resolution. Several lines of evidence suggest a mid-latitude position for Site 766 during this time, including (1) high assemblage diversity characteristic of mid-latitude zones of upwelling and (2) absence of certain ecologically controlled markers found only in low latitudes.

Pollen record and dating of a sediment profile from Ahlequellmoor in Germany

A pollen diagram from the Ahlequellmoor in the Solling area shows the history of vegetation and settlement over the last 7,800 years. In the early Atlantic period mixed deciduous forest with mainly Tilia together with Ulmus and Quercus grew in the area. In the late Atlantic period Quercus became most abundant. Fagus spread in the Sub-boreal period at about 2700 B.C. Since ca. 900 B.C. the Solling was covered by beech forests with some oak. In prehistoric times woodland grazing is indicated. Only in Medieval times are two settlements in the vicinity of the Ahlequellmoor reflected in the pollen diagram. The earlier one is dated to about A.D. 750-1020, and may be connected with the former Monastery of Hethis, which is thought to have existed close to the fen from A.D. 815 to 822. The second Medieval settlement dates to the 11th-12th century. The large-scale woodland destruction of late Medieval and modern times is not clearly visible. The silvicultural measures of the last 200 years are reflected by increasing values of spruce and grassland taxa.

Epibiotic assemblages on seaweeds in the German Wadden Sea (North Sea)

After detachment from benthic habitats, the epibiont assemblages on floating seaweeds undergo substantial changes, but little is known regarding whether succession varies among different seaweed species. Given that floating algae may represent a limiting habitat in many regions, rafting organisms may be unselective and colonize any available seaweed patch at the sea surface. This process may homogenize rafting assemblages on different seaweed species, which our study examined by comparing the assemblages on benthic and floating individuals of the fucoid seaweeds Fucus vesiculosus and Sargassum muticum in the northern Wadden Sea (North Sea). Species richness was about twice as high on S. muticum as on F. vesiculosus, both on benthic and floating individuals. In both seaweed species benthic samples were more diverse than floating samples. However, the species composition differed significantly only between benthic thalli, but not between floating thalli of the two seaweed species. Separate analyses of sessile and mobile epibionts showed that the homogenization of rafting assemblages was mainly caused by mobile species. Among these, grazing isopods from the genus Idotea reached extraordinarily high densities on the floating samples from the northern Wadden Sea, suggesting that the availability of seaweed rafts was indeed limiting. Enhanced break-up of algal rafts associated with intense feeding by abundant herbivores might force rafters to recolonize benthic habitats. These colonization processes may enhance successful dispersal of rafting organisms and thereby contribute to population connectivity between sink populations in the Wadden Sea and source populations from up-current regions.

Calcareous nannofossil stratigraphy, nannofossil events and carbon isotopic ratios of ODP Leg 183 sites

Cores from Sites 1135, 1136, and 1138 of Ocean Drilling Program Leg 183 to the Kerguelen Plateau (KP) provide the most complete Paleocene and Eocene sections yet recovered from the southern Indian Ocean. These nannofossil-foraminifer oozes and chalks provide an opportunity to study southern high-latitude biostratigraphic and paleoceanographic events, which is the primary subject of this paper. In addition, a stable isotope profile was established across the Cretaceous/Tertiary (K/T) boundary at Site 1138. An apparently complete K/T boundary was recovered at Site 1138 in terms of assemblage succession, isotopic signature, and reworking of older (Cretaceous) nannofossil taxa. There is a significant color change, a negative carbon isotope shift, and nannofossil turnover. The placement of the boundary based on these criteria, however, is not in agreement with the available shipboard paleomagnetic stratigraphy. We await shore-based paleomagnetic study to confirm or deny those preliminary results. The Paleocene nannofossil assemblage is, in general, characteristic of the high latitudes with abundant Chiasmolithus, Prinsius, and Toweius. Placed in context with other Southern Ocean sites, the biogeography of Hornibrookina indicates the presence of some type of water mass boundary over the KP during the earliest Paleocene. This boundary disappeared by the late Paleocene, however, when there was an influx of warm-water discoasters, sphenoliths, and fasciculiths. This not only indicates that during much of the late Paleocene water temperatures were relatively equable, but preliminary floral and stable isotope analyses also indicate that a relatively complete record of the late Paleocene Thermal Maximum event was recovered at Site 1135. It was only at the beginning of the middle Eocene that water temperatures began to decline and the nannofossil assemblage became dominated by cool-water species while discoaster and sphenolith abundances and diversity were dramatically reduced. One new taxonomic combination is proposed, Heliolithus robustus Arney, Ladner, and Wise.

Paleocene to middle Eocene calcareous nannofossils of Maude Rise, Weddell Sea

Cores from Sites 689 and 690 of Ocean Drilling Program Leg 113 provide the most continuous Paleocene and Eocene sequence yet recovered by deep sea drilling in the high latitudes of the Southern Ocean. The nannofossil-foraminifer oozes and chalks recovered from Maud Rise at 65°S in the Weddell Sea provide a unique opportunity for biostratigraphic study of extremely high southern latitude carbonate sediments. The presence of warm water index fossils such as the discoasters and species of the Tribrachiatus plexus facilitate the application of commonly used low latitude calcareous nannofossil biostratigraphic zonation schemes for the upper Paleocene and lower Eocene intervals. In the more complete section at Site 690, Okada and Bukry Zones CP1 through CP10 can be identified for the most part with the possible exception of Zone CP3. Several hiatuses are present in the sequence at Site 689 with the most notable being at the Cretaceous/Tertiary and Paleocene/Eocene boundaries. Though not extremely diverse, the assemblage of discoasters in the upper Paleocene and lower Eocene calcareous oozes is indicative of warm, relatively equable climates during that interval. A peak in discoaster diversity in uppermost Paleocene sediments (Zone CP8) corresponds to a negative shift in 5180 values. Associated coccolith assemblages are quite characteristic of high latitudes with abundant Chiasmolithus, Prinsius, and Toweius. Climatic cooling is indicated for middle Eocene sediments by assemblages that contain very abundant Reticulofenestra, lack common discoasters and sphenoliths and are much less diverse overall. Two new taxa are described, Biscutum? neocoronum n. sp. and Amithalithina sigmundii n. gen., n. sp.

Pollen and macrofossils profiles and age determination from three cores in Northeastern Kansas, U.S.A.

Two marshes near Muscotah and Arrington, Atchison County, northeastern Kansas, yielded a pollen sequence covering the last 25,000 yrs of vegetation development. The earliest pollen spectra are comparable with surface pollen spectra from southern Saskatchewan and southeastern Manitoba and might indicate a rather open vegetation but with some pine, spruce, and birch as the most important tree species, with local stands of alder and willow. This type of vegetation changed about 23,000 yrs ago to a spruce forest, which prevailed in the region until at least 15,000 yrs ago. Because of a hiatus, the vegetation changes resulting in the spread of a mixed deciduous forest and prairie, which was present in the region from 11,000 to 9,000 yrs ago, remain unknown. Prairie vegetation, with perhaps a few trees along the valleys, covered the region until about 5,000 yrs ago, when a re-expansion of deciduous trees began in the lowlands.

Paleocene and Eocene calcareous nannofossils at DSDP Legs 25 and 40 Holes

Paleocene and Eocene nannofossil flora from Deep Sea Drilling Project Legs 25 and 40 were analyzed in order to provide a basis of comparison with DSDP Legs 36 and 71 and with other South Atlantic assemblages. A mid-latitude biostratigraphic zonation, using previously described zonal markers, was adopted for the southwest Indian Ocean. Various diagenetic effects were noted in the sedimentary sequences. Some of these mask to some extent paleoecologic signals, particularly those generated by the Discoaster/Chiasmolithus ratio.

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.

Distribution of calcareous nannofossils in upper Cretaceous and Cenozoic sediments of the Kerguelen Plateau

ODP Leg 119 drilled 11 sites on the Kerguelen Plateau (southern Indian Ocean) and Prydz Bay (East Antarctica). Upper Pliocene through Quaternary sediments were recovered at Site 736 on the northern Kerguelen Plateau; calcareous nannofossils occurred in only a few samples. Over 700 m of middle Eocene through Quaternary sediments was cored at Site 737 on the northern Kerguelen Plateau, and calcareous nannofossils are abundant in the middle Eocene through the middle Miocene sediments. Nearly 500 m of sediments ranging from the lower Turanian to the Quaternary was recovered at Site 738 on the southern Kerguelen Plateau; calcareous nannofossils are abundant from the Miocene downward. Calcareous nannofossils are also abundant in the upper Eocene through Miocene section from Site 744 on the southern Kerguelen Plateau. Except for Core 119-746A-13H, the Neogene sequences drilled at deep-water Sites 745 and 746 off the southern Kerguelen Plateau are devoid of calcareous nannofossils. Occurrences of calcareous nannofossils were generally rare and sporadic at Sites 739 and 742 in Prydz Bay and suggest that the diamictite sequences recovered is as old as middle Eocene-early Oligocene age. Other sites drilled in Prydz Bay (Sites 740, 741, and 743) did not yield calcareous nannofossils. Species diversity of calcareous nannofossils was low (about a dozen) in the southern Indian Ocean in the Late Cretaceous. High-latitude nanno floral characteristics are apparent after the Cretaceous/Tertiary boundary extinctions. Cold climatic conditions limited Oligocene calcareous nannofossil assemblages to fewer than a dozen species, and extinctions of species generally were not compensated by originations of new species. Only a few species of calcareous nannofossils were found in the Miocene sequences, in which Coccolithuspelagicus and one or two species of Reticulofenestra exhibit extreme (0%-100%) fluctuations in assemblage dominance, and these fluctuations may reflect rapid fluctuations in the surface-water temperatures. Further deterioration of climate in the late Neogene essentially excluded calcareous nannoplankton from the Southern Ocean. Significantly warmer water conditions during part of the early-middle Pleistocene were inferred by a few lower-middle Pleistocene calcareous nannofossil species found on the Kerguelen Plateau. The calcareous nannofossil zonation of Roth (1978 doi:10.2973/dsdp.proc.44.134.1978) can be applied to the Upper Cretaceous section recovered at Site 738, and the zonation of Okada and Bukry (1980 doi:10.1016/0377-8398(80)90016-X) can be applied without much difficulty to the Paleocene to middle Eocene sequences from the Kerguelen Plateau. However, some conventional upper Paleogene markers are not useful for southern high latitudes, whereas a few nonconventional species events are useful for subdividing the upper Paleogene sequences. The latter species events include the first occurrence (FO) of Reticulofenestra reticulata, the FO and last occurrence (LO) of Reticulofenestra oamaruensis, the LO of Isthmolithus recurvus, and the LO of Chiasmolithus altus. As the Neogene sequences from the southern Indian Ocean contain only a few long-ranging, cold-water species, or are devoid of coccoliths, calcareous nannofossil zonations remain virtually unworkable for the Neogene in the high-latitude southern Indian Ocean as in other sectors of the Southern Ocean.

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.

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.

Ecological investigations in the wadden area off Borkum, East Frisian Islands, Germany

Die Bodentiergemeinschaft des Wattenmeeres ist von Frühjahr bis Herbst eines jeden Jahres durch extrem hohe Dichten von Jungtieren charakterisiert. Die Kenntnisse über die Ansiedlung von fplanktischen Larven im Wattenmeer, sowie die Dynamik postlarvaler Stadien sind aufgrund der üblicherweise verwendeten, großen Siebmaschenweiten gering. Gerade aber diesen Altersstadien kommt möglicherweise eine besondere Stellung im Energiefluß des Wattenmeeres zu. An 5 Stationen (von NWL bis HWL, B1-B5) im Rückseitenwatt der ostfriesischen Insel Borkum wurden 1986 Ansiedlung, räumliche Verteilung, Wachstum, Mortalität und Produktion der Altersklasse 0 von Macoma balthica, Mya arenaria und Cerastoderma edule untersucht. Um die Ansiedlung der planktotrophen Larven dieser Arten zu beschreiben, wurden ihre Dichten in Plankton und Bodenproben miteinander verglichen. Die Untersuchungen zur Dynamik der benthischen Stadien wurden mit zwei in der Probenfläche und der Siebmaschenweite unterschiedlichen Probenserien durchgeführt. Die Drift postlarvaler Stadien wurde durch bodennahe Planktonfänge innerhalb des Eulitorals nachgewiesen. Parallel zu den Untersuchungen an der Endofauna wurden das Vorkommen und die Größe epibenthischer Räuber im Untersuchungsgebiet erfaßt. Die Hauptansiedlung von M. balthica- und M. arenaria-Larven erfolgte nahezu gleichzeitig Ende Mai/Anfang Juni. Die meisten Larven beider Arten gingen an der prielnächsten (tiefsten) Station (B1) zum Bodenleben über, gefolgt von der nächst höher gelegenen Station B2. Während frühe Bodenstadien von M. arenaria nicht im oberen Bereich des Watts (B3,B4) gefunden wurden, ist eine geringfügige Erstansiedlung von M. balthica in diesem Gebiet nicht auszuschließen. Ein die Ansiedlung limitierender Einfluß der relativ dichten Mya arenaria-Siedlung an den Stationen B1 und B2 sowie der Alttiere von M. balthica konnte nicht festgestellt werden. Die Ähnlichkeit des Ansiedlungsprozesses bei beiden Arten, die sich im Zahlenverhältnis Larvenangebot zu Anzahl der ersten Bodenstadien widerspiegelt, kann ein Hinweis auf eine überwiegend passive Ansiedlung der Larven am Boden sein. Der Ort der Hauptansiedlung von C. edule wurde durch den Transekt nicht erfaßt. Die Station B2 war zwar durch ein Herzmuschelfeld charakterisiert, dieses war aber nach zwei Eiswintern nahezu vollständig eliminiert. Der Abundanz der planktischen Larven zufolge war der Hauptansiedlungszeitraum ebenfalls Ende Mai/Anfang Juni. Zu dieser Zeit wurden nur vereinzelt frühe Bodenstadien an den Stationen B1 und B2 gefunden, keine an den Stationen B3 und B4. Während die frühen postlarvalen Stadien von M. arenaria überwiegend am Ort der Ansiedlung blieben, verbreiteten sich die von M. balthica bis in den oberen Bereich des Untersuchungsgebietes (B3-B5). Analog zu der Besiedlung dieser Gebiete durch postlarvale M. balthica wurde die im Verlauf des Untersuchungsjahres stattfindende Kolonisierung der Station B1 durch C. edule ebenfalls postlarvalem Transport zugeschrieben. Demzufolge spielt bei beiden Muschelarten postlarvaler Transport eine wichtige Rolle bei der Besiedlung von Habitaten. Planktonfänge innerhalb der bodennahen Wasserschicht bestätigten, daß im Untersuchungsgebiet M. balthica die am stärksten verdriftende Muschelart war, gefolgt von C. edule. Mortalität, Wachstum, mittlere Biomasse, Produktion und P/B-Verhältnis wurden für M. balthica an den Stationen B1, B3 und B4 sowie für M. arenaria an der Station B1 bestimmt. Wachstum und damit auch Produktion beider Arten erwiesen sich hier - wie an den höher gelegen Stationen (nur M. balthica) - als durch größenselektiven Feinddruck beeinflußt. Der Effekt postlarvalen Transports auf Wachstum wird diskutiert. Übergreifend über die auf Artebene diskutierten Ergebnisse wird die Bedeutung der Dispersion postlarvaler Stadien und die Wirkung epibenthischen Feinddrucks im Wattenmeer erörtert. Der Vergleich postlarvalen Transportes mit der Dispersion planktischer Larvenstadien, der Dispersion von Meiofauna und der Mobilität adulter Stadien der Makrofauna verdeutlicht, daß es sich hierbei um eine Strategie handeln kann, innerhalb eines unvorhersagbaren Biotops freiwerdende Ressourcen zu nutzen und dadurch Konkurrenz zu vermeiden. Es wird die Hypothese aufgestellt, daß Initialansiedlung und Immigration einerseits sowie Feinddruck und Emigration andererseits einen Regelkreis darstellen, der in verschiedenen Teilbereichen des Watts mit unterschiedlicher Geschwindigkeit abläuft.