Mid-Pleistocene benthic foraminiferal record in the Southwest Pacific

Benthic foraminiferal faunas from three bathyal sequences provide a proxy record of oceanographic changes through the mid-Pleistocene transition (MPT) on either side of the Subtropical Front (STF), east of New Zealand. Canonical correspondence analyses show that factors related to water depth, latitude and climate cycles were more significant than oceanographic factors in determining changes in faunal assemblage composition over the last 1 Ma. Even so, mid-Pleistocene faunal changes are recognizable and can be linked to inferred palaeoceanographic causes. North of the largely stationary STF the faunas were less variable than to the south, perhaps reflecting the less extreme glacial-interglacial fluctuations in the overlying Subtropical Surface Water. Prior to Marine Isotope Stage (MIS) 21 and after MIS 15, the northern faunas had fairly constant composition, but during most of the MPT faunal composition fluctuated in response to climate-related food-supply variations. Faunal changes through the MPT suggest increasing food supply and decreasing dissolved bottom oxygen. South of the STF, beneath Subantarctic Surface Water, mid-Pleistocene faunas exhibited strong glacial-interglacial fluctuations, inferred to be due to higher interglacial nutrient supply and lower oxygen levels. The most dramatic faunal change in the south occurred at the end of the MPT (MIS 17- 12). with an acme of Abditodentrix pseudothalmanni, possibly reflecting higher carbon flux and lower bottom oxygen. This study suggests that the mid-Pleistocene decline and extinction of a group of elongate, cylindrical deep-sea foraminifera may have been related to decreased bottom oxygen concentrations as aresult of slower deep-water currents.

Correlation of Bolboforma zonation and nannoplankton stratigraphy in the Neogene of the North Atlantic

The Neogene Bolboforma zones established in the North Atlantic have been correlated with the calcareous nannoplankton stratigraphy obtained by investigation of the same samples from DSDP Sites 12-116 (44 samples), 49-408 (76 samples), 81-555 (43 samples) and 94-608 (103 samples). The absolute ages for the zonal boundaries were determined by the paleomagnetic record of Site 94-608. This correlation and the age determinations are additional useful tools to develop a precise biostratigraphy of Neogene sediments in the Northern Atlantic.

Radiolarian chronology and fauna across the middle/late Eocene boundary at ODP Hole 171-1052A

Quantitative radiolarian assemblage analysis has been conducted on middle and upper Eocene sediments (Zones RP16 to RP18) from Ocean Drilling Program Site 1052 in order to establish the radiolarian magnetobiochronology and determine the nature of the faunal turnover across the middle/late Eocene boundary in the western North Atlantic Ocean. We recognize and calibrate forty-five radiolarian bioevents to the magneto- and cyclo-stratigraphy from Site 1052 to enhance the biochronologic resolution for the middle and late Eocene. Our data is compared to sites in the equatorial Pacific (Leg 199) to access the diachrony of biostratigraphic events. Eleven bioevents are good biostratigraphic markers for tropical/subtropical locations (south of 30°N). The primary markers (lowest occurrences of Cryptocarpium azyx and Calocyclas bandyca) which are tropical zonal boundary markers for Zones RP17 and RP18 provide robust biohorizons for correlation and age determination from the low to middle latitudes and between the Atlantic and Pacific Oceans. Some other radiolarian bioevents are highly diachronous (<1 million years) between oceanic basins. A significant faunal turnover of radiolarians is recognized within Chron C17n.3n (37.7 Ma) where 13 radiolarian species disappear rapidly in less than 100 kyr and 4 new species originate. The radiolarian faunal turnover coincides with a major extinction in planktonic foraminifera. We name the turnover phase, the Middle/Late Eocene Turnover (MLET). Assemblage analysis reveals the MLET to be associated with a decrease in low-mid latitude taxa and increase in cosmopolitan taxa and radiolarian accumulation rates. The MLET might be related to increased biological productivity rather than to surface-water cooling.

Benthos fauna in the North Sea from 2 surveys in 1986 and 1987

During two surveys in the North Sea, in summer 1986 and in winter 1987, larger epibenthos was collected with a 2 m beam trawl. The distributions of the species were checked for average linkage by means of the JACCARD-index cluster analysis. In summer two main clusters can be recognized. These are situated to the north and to the south of the Dogger Bank. In winter two main clusters may be recognized as well, but these clusters divide the North Sea into a western and an eastern part. We conclude, that these differences of epibenthos characteristics are correlated with seasonal changes in water body distributions.

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.

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.

Abundance and biomass of the benthic infauna of the North Sea

In 1986 participants of the Benthos Ecology Working Group of ICES conducted a synoptic mapping of the infauna of the southern and central North Sea. Together with a mapping of the infauna of the northern North Sea by Eleftheriou and Basford (1989, doi:10.1017/S0025315400049158) this provides the database for the description of the benthic infauna of the whole North Sea in this paper. Division of the infauna into assemblages by TWINSPAN analysis separated northern assemblages from southern assemblages along the 70 m depth contour. Assemblages were further separated by the 30, 50 m and 100 m depth contour as well as by the sediment type. In addition to widely distributed species, cold water species do not occur further south than the northern edge of the Dogger Bank, which corresponds to the 50 m depth contour. Warm water species were not found north of the 100 m depth contour. Some species occur on all types of sediment but most are restricted to a special sediment and therefore these species are limited in their distribution. The factors structuring species distributions and assemblages seem to be temperature, the influence of different water masses, e.g. Atlantic water, the type of sediment and the food supply to the benthos.

Distribution of deep-sea foraminifera in surface sediments east of New Zealand

Paleobathymetric assessments of fossil foraminiferal faunas play a significant role in the analysis of the paleogeographic, sedimentary, and tectonic histories of New Zealand's Neogene marine sedimentary basins. At depths >100 m, these assessments often have large uncertainties. This study, aimed at improving the precision of paleodepth assessments, documents the present-day distribution of deep-sea foraminifera (>63 µm) in 66 samples of seafloor sediment at 90-700 m water depth (outer shelf to mid-abyssal), east of New Zealand. One hundred and thirty-nine of the 465 recorded species of benthic foraminifera are new records for the New Zealand region. Characters of the foraminiferal faunas which appear to provide the most useful information for estimating paleobathymetry are, in decreasing order of reliability: relative abundance of common benthic species; benthic species associations; upper depth limits of key benthic species; and relative abundance of planktic foraminifera. R mode cluster analysis on the quantitative census data of the 58 most abundant species of benthic foraminifera produced six species associations within three higher level clusters: (1) calcareous species most abundant at mid-bathyal to outer shelf depths (<1000 m); (2) calcareous species most abundant at mid-bathyal and greater depths (>600 m); (3) agglutinated species mostly occurring at deep abyssal depths (>3000 m). A detrended correspondence analysis ordination plot exhibits a strong relationship between these species associations and bathymetry. This is manifest in the bathymetric ranges of the relative abundance peaks of many of the common benthic species (e.g., Abditodentrix pseudothalmanni 500-2800 m, Bolivina robusta 200-650 m, Bulimina marginata f. marginata 20-600 m, B. marginata f. aculeata 400-3000 m, Cassidulina norvangi 1000-4500 m, Epistominella exigua 1000-4700 m, and Trifarina angulosa 10-650 m), which should prove useful in paleobathymetric estimates. The upper depth limits of 28 benthic foraminiferal species (e.g., Fursenkoina complanata 200 m, Bulimina truncana 450 m, Melonis affinis 550 m, Eggerella bradyi 750 m, and Cassidulina norvangi 1000 m) have potential to improve the precision of paleobathymetric estimates based initially on the total faunal composition. The planktic percentage of foraminiferal tests increases from outer shelf to upper abyssal depths followed by a rapid decline within the foraminiferal lysocline (below c. 3600 m). A planktic percentage <50% is suggestive of shelf depths, and >50% is suggestive of bathyal or abyssal depths above the CCD. In the abyssal zone there is dramatic taphonomic loss of most agglutinated tests (except some textulariids) at burial depths of 0.1-0.2 m, which negates the potential usefulness of these taxa in paleobathymetric assessments.

Early to middle Miocene radiolarian stratigraphy of the Kerguelen Plateau, Southern Ocean

Early to middle Miocene radiolarian assemblages were examined at three sites (747, 748, and 751) that were cored during Ocean Drilling Program Leg 120 south of the present polar frontal zone on the Kerguelen Plateau (Indian sector of the Southern Ocean). The radiolarian biostratigraphic study relies on a radiolarian zonation recently developed on Leg 113 materials in the Atlantic sector of the Southern Ocean, which is correlated with the geomagnetic time scale. New radiolarian biostratigraphic data also considering the established geomagnetic polarity record were used to improve and emend the age calibration of some lower Miocene radiolarian zones and a redefined middle Miocene radiolarian zonation is proposed. Based on these results, a revised age assignment of the lower Miocene sections drilled at Leg 113 Sites 689 and 690 is proposed.

Contribution of woody habitat islands to the conservation of birds and their potential ecosystem services in an extensive Colombian rangeland

The conservation of birds and their habitats is essential to maintain well-functioning ecosystems including human-dominated habitats. In simplified or homogenized landscapes, patches of natural and semi-natural habitat are essential for the survival of plant and animal populations. We compared species composition and diversity of trees and birds between gallery forests, tree islands and hedges in a Colombian savanna landscape to assess how fragmented woody plant communities affect forest bird communities and how differences in habitat characteristics influenced bird species traits and their potential ecosystem function. Bird and tree diversity was higher in forests than in tree islands and hedges. Soil depth influenced woody species distribution, and canopy cover and tree height determined bird species distribution, resulting in plant and bird communities that mainly differed between forest and non-forest habitat. Bird and tree species and traits widely co-varied. Bird species in tree islands and hedges were on average smaller, less specialized to habitat and more tolerant to disturbance than in forest, but dietary differences did not emerge. Despite being less complex and diverse than forests, hedges and tree islands significantly contribute to the conservation of forest biodiversity in the savanna matrix. Forest fragments remain essential for the conservation of forest specialists, but hedges and tree islands facilitate spillover of more tolerant forest birds and their ecological functions such as seed dispersal from forest to the savanna matrix.

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.

Late middle Eocene to late Oligocene radiolarian biostratigraphy of ODP Hole 113-689B of Maud Rise, Southern Ocean

We propose a new biostratigraphic scheme comprising the Eucyrtidium spinosum, Eucyrtidium antiquum (new), Lychnocanoma conica (emended), Clinorhabdus robusta (emended) and Stylosphaera radiosa (emended) Zones, in ascending order, in Eocene to Oligocene sediments drilled on Maud Rise in Southern Atlantic Ocean (Site 689, Ocean Drilling Program Leg 113). The bases of these zones are defined by the lowermost occurrences of E. spinosum, E. antiquum, L. conica, C. robusta and the uppermost occurrence of Axoprunum irregularis (?), respectively. From correlation to the magnetostratigraphic data, the E. spinosum, E. antiquum, L. conica, C. robusta and S. radiosa Zones are assigned to the late middle Eocene through late Eocene (Subchrons C17n2 to C13r), earliest Oligocene (C13n to C11n), late early Oligocene (C11n to C10n2), early late Oligocene (C10n1 to C8r) and latest Oligocene (C8r to C7An), respectively. The four boundary datum levels and supplementary datum levels such as the lowermost occurrences of A. irregularis (?), Dicolocapsa microcephala and Lithomelissa challengerae may be recognized in other ODP sites in the Southern Ocean. The first occurrence of E. antiquum approximates the Eocene-Oligocene boundary in Southern Ocean but the last occurrences of many species such as Periphaena decora, D. microcephala and the Lithomelissa sphaerocephalis group are commonly diachronous between high latitude sites. Two new species, Theocyrtis (?) triapenna and Spirocyrtis parvaturris, are described.

Late Cretaceous benthic foraminiferal assemblages from Demerara Rise, western tropical Atlantic

This paper is based on Santonian-Campanian sediments of Ocean Drilling Program Sites 1257 (2951 mbsl) and 1259 (2353 mbsl) from Demerara Rise (Leg 207, western tropical Atlantic, off Surinam). According to its position, Demerara Rise should have been influenced by the early opening of the Equatorial Atlantic Gateway and the establishment of a bottom-water connection between the central and South Atlantic Oceans during the Late Cretaceous. The investigated benthic foraminiferal faunas demonstrate strong fluctuations in bottom-water oxygenation and organic-matter flux to the sea-floor. The Santonian-earliest Campanian interval is characterised by laminated black shales without benthic foraminifera in the lowermost part, followed by an increasing number of benthic foraminifera. These are indicative of anoxic to dysoxic bottom waters, high organic-matter fluxes and a position within the oxygen minimum zone. At the shallower Site 1259, benthic foraminifera occurred earlier (Santonian) than at the deeper Site 1257 (Early Campanian). This suggests that the shallower site was characterised by fluctuations in the oxygen minimum zone and that a re-oxygenation of the sea-floor started considerably earlier at shallower water-depths. We speculate that this re-oxygenation was related to the ongoing opening of the Equatorial Atlantic Gateway. A condensed glauconitic chalk interval of Early Campanian age (Nannofossil Zone CC18 of Sissingh) overlies the laminated shales at both sites. This interval contains benthic foraminiferal faunas reflecting increasing bottom-water oxygenation and reduced organic-matter flux. This glauconitic chalk is strongly condensed and contains most of the Lower and mid-Campanian. Benthic foraminiferal species indicative of well-oxygenated and more oligotrophic environments characterise the overlying mid- to Upper Campanian nannofossil chalk. During deposition of the nannofossil chalk, a permanent deep-water connection between the central and South Atlantic Oceans is proposed, leading to ventilated and well-oxygenated bottom waters. If this speculation is true, the establishment of a permanent deep-water connection between the central and South Atlantic Oceans terminated Oceanic Anoxic Event 3 "black shale" formation in the central and South Atlantic marginal basins during the Early Campanian (Nannofossil Zone CC18) and led to well-oxygenated bottom waters in the entire Atlantic Ocean during the Late Campanian (at least from Nannofossil Zone CC22 onwards).