Chronology and correlation of Quaternary magnetostratigraphy and nannofossil biostratigraphy in Norwegian-Greenland Sea sediments

Paleomagnetic analyses of a series of sediment cores from the Norwegian—Greenland Sea document the existence of seven short-lived geomagnetic events during the last about 500.000 years. Calcareous nannofossil biostratigraphy, correlated to oxygen isotope chronostratigraphy, provides a time framework to infer age and duration of these periods of extreme divergence of the earth's magnetic paleofield from the regular normal polarity configuration of the Brunhes Chron. The geomagnetic events typically extend over 5 to 10 kyr. Two events are observed within the oxygen isotope stage 2–4 interval. A short event is recorded at the stage 4/5 boundary and another just below the stage 5/6 boundary. Additional three geomagnetic events are identified in oxygen isotope stage 6, at the stage 9/10 boundary and near the top of oxygen isotope stage 13, respectively.

---

Zusammenfassung Paläomagnetische Analysen einer Serie von Sedimentkernen aus der Norwegisch-Grönländischen See dokumentieren die Existenz von sieben kurzen geomagnetischen Ereignissen innerhalb der letzten etwa 500.000 Jahre. Alter und Dauer dieser extrem von der regulären Konfiguration normaler Polarität des erdmagnetischen Feldes der Brunhes Epoche abweichenden Episoden werden im Zeitrahmen von Biostratigraphien kalkiger Nannofossilien bestimmt, die mit einer Sauerstoffisotopen-Chronostratigraphie korreliert sind. Die geomagnetischen Ereignisse erstrecken sich typischerweise über Zeiträume von 5 bis 10 tausend Jahren. Zwei Ereignisse werden im Intervall der Sauerstoffisotopen Stadien 2–4 beobachtet. Ein kurzes Ereignis fällt in etwa mit der Stadien 4/5 Grenze zusammen, ein weiteres findet sich knapp unterhalb der Stadien 5/6 Grenze. Drei weitere geomagnetische Ereignisse sind im Sauerstoffisotopen Stadium 6, an der Stadien 9/10 Grenze und nahe dem Ende des Stadiums 13 identifiziert worden.

---

Résumé Des analyses paléomagnétiques pratiquées dans une série de carottes de sédiments de la mer de Norvège-Groenland montrent l'existence de sept événements géomagnétiques de courte durée, au cours des derniers 500.000 ans. Ces événements sont marqués par une extrême divergence du champ paléomagnétique terrestre par rapport à la configuration régulière de la polarité normale de Brunhes. La biostratigraphie des nannofossiles calcaires, correlée à la chronostratigraphie des isotopes de l'oxygène, fournit un cannevas temporel qui permet d'en préciser l'âge et la durée. Ils s'étendent typiquement sur 5 000 à 10 000 ans. Deux événements sont observés dans l'intervalle 2–4 des stades des isotopes de l'oxygène. Un événement court est enregistré à la limite des stades 4/5 et un autre juste sous la limite 5/6. Les trois autres événements se situent respectivement dans le stade 6, à la limite des stades 9/10 et près du sommet du stade 13.

---

, 500.000 7 . , Brunhes, , . 5 10 . 2–4 . 4/5, — 5/6. 6, 9/10 13.

     

麦哲伦海山群MK海山富钴结壳钙质超微化石生物地层学研究

富钴结壳是发育在深海海山之上的一种重要沉积矿产资源,建立准确可靠的年代学格架,无论对富钴结壳成矿作用研究还是对古海洋环境研究,都具有重要意义。但迄今为止,由于定年技术的限制,可靠的富钴结壳年代学框架资料并不多。文中以钙质超微化石生物地层学方法为主要手段,并结合Co经验公式法、样品的结构特征和磷酸盐化作用时代等资料,对麦哲伦海山群MK海山MKD13-3号富钴结壳样品的年代学框架进行了综合限定。研究结果如下。(1)该样品剖面从下到上可以分4层,分别为:磷块岩基岩,其中包括R层(残留层)结壳,时代为112.0~70.6Ma B.P.;I层,进一步划分为I-1和I-2层,其时代分别为55.0~48.0Ma B.P.和44.0~23.0Ma B.P.;Ⅱ层,时代为23.0~14.0Ma B.P.;Ⅲ层,时代为5.0~0Ma B.P.。(2)该富钴结壳样品在生长过程中发育了3个生长间断,分别为:基岩与I-1层之间的生长间断,时代为70.6~55.0Ma B.P.;I-1层与I-2层之间的生长间断,时代为48.0~44.0Ma B.P.;Ⅱ层与Ⅲ层之间的生长间断,时代为14.0~5.0Ma B.P.。     

Calcareous nannofossil biostratigraphy and paleoecology of the Cenomanian – Turonian transition in the Tarfaya Basin, southern Morocco

An abundant and diverse nannoflora occurs across the Cenomanian/Turonian (C/T) boundary at Tazra in the Tarfaya Basin of southern Morocco. The nannoflora of this sequence permits recognition of three biozones (CC10-CC12), three subzones (CC10a, CC10b and CC10c), and thirteen important nannolith bioevents previously reported from this interval elsewhere. The floral record shows erratic species abundance fluctuations that clearly vary with lithology and reflect at least in part preservational bias and diagenetic processes. In general, four dissolution resistant taxa are dominant: Watznaueria barnesae, Eiffellithus turriseiffelii, Eprolithus floralis, and Zeugrhabdotus spp. The late Cenomanian Zone CC10 marks a rapid excursion in ∂¹³C and is characterized by the successive extinction of four taxa, which are widely recognized as reliable biomarkers: Corollithion kennedyi, Axopodorhabdus albianus, Lithraphidites acutus, and Helenea chiastia. This interval is also marked by high species richness and high abundance of the tropical species Watznaueria barnesae, suggesting warm tropical waters. The subsequent ∂¹³C plateau and organic carbon-rich black shale deposition of the oceanic anoxic event (OAE2) is characterized by low species richness, but high nannofossil abundance, and peak abundance of the cool water and high productivity indicator Zeugrhabdotus spp., followed by the first peak abundance of cool water Eprolithus floralis. This interval correlates with the planktic foraminiferal diversity minimum and the Heterohelix shift, which marks the expansion of the oxygen minimum zone (OMZ). The C/T boundary is identified based on the FO of Quadrum gartneri, which is <1 m below the FO of the planktic foraminifer C/T marker Helvetoglobotruncana helvetica. In the early and middle Turonian, the two dominant species, tropical W. barnesae and cool water E. floralis, alternate in abundance and suggest fluctuating climatic conditions.     

Distribution of quartz in late Quaternary Atlantic sediments in relation to climate

The distribution of quartz in the surface sediments of the Atlantic Ocean reflects derivation from continents by means of rivers, wind, ice, and coastal erosion. Enrichment of quartz thus supplied has occurred in some deep basins of especially the southern high latitudes from winnowing of finegrained clays by bottom currents. Although similar modes of quartz transport may have operated both during the Holocene and the last glacial maximum (18,000 yr B.P.), significant differences in the intensity of transport and in the locii of deposition, which are attributable to climatic variations during these times, exist in some areas of the Atlantic. In Holocene sediments of the eastern equatorial Atlantic, a band of high percent quartz exists directly off the present Saharan Desert and Sahel region and reflects the trade-wind transport of dusts from these arid and semiarid regions. During the last glacial maximum (18,000 yr B.P.), this high quartz band expanded southward by about 8° of latitude. This expansion was caused not only by the southward expansion of aridity and desert dunes but also by the southward migration of the northerly belt of trade winds during the last glaciation. Relatively high abundances and accumulation rates of quartz during the last glaciation suggest higher intensities of trade winds during that time compared to the Holocene. In the North Atlantic, the abundances of quartz in Holocene sediments are high adjacent to Greenland-Iceland and in the areas off Newfoundland-Labrador, and gradually decrease toward the central areas. The polar front and limit of sea-ice melting are at present confined to the northern part of the North Atlantic. The ice-rafting of quartz grains is, therefore, effective in the areas adjacent to Greenland and to some extent off Labrador causing high abundances in these areas. In contrast to this, during the last glaciation, the quartz abundances and accumulation rates are high in the central areas of North Atlantic around 45°N and decrease toward Greenland-Newfoundland. The migration of the polar front to as far south as 45°N and the consequent southward migration of sea-ice melting and ice-rafting during the last glaciation apparently caused this change in distribution. In addition to ice-rafting at present, wave or current reworking of relict glacial-marine detritus may have caused the high abundance of quartz in the surface sediments off Newfoundland-Labrador. In 18,000 yr B.P. sediments of the Norwegian Sea, the area of high percent quartz (>10%) is more extensive than that in Holocene sediments. This reflects the greater influence of ice-rafting or glacier activity in the sediment dispersal in the Norwegian Sea during the last glacial times.     

Chemical composition of late Pleistocene-Holocene pelagic sediments in Gakkel Ridge,Arctic Ocean

The paper presents data on the chemical composition of Late Pleistocene-Holocene sediments in the Gakkel Ridge according to data on sediment core PS 70/306-3, offers a hypothetical litho-stratigraphic model, and provides data on chemo-stratigraphic horizons distinguished based on the distribution of carbonates, organic carbon, metals (Fe, Mn, Cu, Zn, Co, Ni, V, Pb), As, and P in the core. Chemical transformations of sediments at the redox barrier are discussed, along with relations between the composition of the sediments and the facies sedimentation conditions.     

Middle Campanian–lowermost Maastrichtian nannofossil and foraminiferal biostratigraphy of the northwestern Australian margin

The middle–late Campanian was marked by an increase in the bioprovinciality of calcareous microfossil assemblages into distinct Tethyan, Transitional, and Austral Provinces that persisted to the end of the Maastrichtian. The northwestern Australian margin belonged to the Transitional Province and the absence of key Tethyan marker species such as Radotruncana calcarata and Gansserina gansseri has led petroleum companies operating in the area to use the locally developed KCCM integrated calcareous microfossil zonation scheme. The KCCM zonation is a composite scheme comprising calcareous nannofossil (KCN), planktonic foraminiferal (KPF) and benthonic foraminiferal (KBF) zones. This paper presents the definitions and revisions of Zones KCCM8–19, from the highest occurrence (HO) of Aspidolithus parcus constrictus to the lowest occurrence (LO) of Ceratolithoides aculeus, and builds on our previous early–late Maastrichtian study. The presence of a middle–upper Campanian disconformity is confirmed by microfossil evidence from the Vulcan Sub-basin, Exmouth and Wombat plateaus, and the Southern Carnarvon Platform. In the Vulcan Sub-basin and on the Exmouth Plateau (ODP Hole 762C) the hiatus extends from slightly above the LO of common Rugoglobigerina rugosa to above the LO of Quadrum gothicum. On the Wombat Plateau (ODP Hole 761B) it spans from above the LO of Heterohelix semicostata to above the LO of Quadrum gothicum; and in the Southern Carnarvon Platform the disconformity has its longest duration from above the HO of Heterohelix semicostata to above the LO of Quadrum sissinghii. A significant revision of the events which define Zones KCCM18 and 19 was necessary owing to the observation that the LO of Ceratolithoides aculeus occurs below the HOs of Archaeoglobigerina cretacea and Stensioeina granulata incondita and the LO of common Rugoglobigerina rugosa. In the original zonation these events were considered to be coincident.     

Reconstruction of late Quaternary sea-level change in southwestern British Columbia from sediments in isolation basins

Bracketing ages on marine—freshwater transitions in isolation basins extending from sea level to 100 m elevation on Lasqueti Island, and data from shallow marine cores and outcrops on eastern Vancouver Island, constrain late Pleistocene and Holocene sea-level change in the central Strait of Georgia. Relative sea level fell from 150 m elevation to about —15 m from 14000 cal. yr BP to 11 500 cal. yr BP. Basins at higher elevations exhibit abrupt changes in diatom assemblages at the marine-freshwater transition. At lower elevations an intervening brackish phase suggests slower rates of uplift. Relative sea level rose to about +1 m about 9000 cal. yr BP to 8500 cal. yr BP, and then slowly fell to the modern datum. The mean rate of glacio-isostatic rebound in the first millennium after deglaciation was about 0.11 in a ^-1, similar to the peak rate at the centres of the former Laurentide and Fennoscandian ice complexes. The latter feature smooth, exponential-style declines in sea level up to the present day, whereas in the study area the uplift rate dropped to less than one-tenth of its initial value in only about 2500 years. Slower, more deeply seated isostatic recovery generated residual uplift rates of <0.01 m a^-1 in the early Holocene after the late-Pleistocene wasting of the Cordilleran ice sheet.     

Pesticide behaviour in Quaternary sediments

Pesticides are very often spread in agricultural and forest areas covering important groundwater bodies in Quaternary sand and gravel deposits. They are mostly synthetic organic chemicals used for plant protection against predators and competing herbs. According to their radius of action they can be separated into herbicides, insecticides, nematicides, acaricides, molluscicides, rodenticides, fungicides, and bactericides. With respect to the risks of groundwater contamination by pesticides, only the first three groups are of interest. For a risks assessment of groundwater contamination, detailed knowledge of the geochemical behaviour of the pesticides and of the physico-chemical processes controlling their persistence and transport in the sediments is necessary. These processes can be summarized as dissolution/precipitation, adsorption/ desorption, degradation and transport processes in the soil in the unsaturated and saturated zones. Furthermore, the type of plant production being established in the area has to be considered. In the case of crop rotation the applied pesticides are changed every year and the risk of groundwater contamination is normally low because of retardation and degradation. In soils used for special-purpose crops, an accumulation of pesticide residues is possible, because the same substances are applied every year. Especially on sandy soils the leaching of residues can lead to severe groundwater contamination.     

The research front in Arctic Quaternary geology

Book reviewed in this article:
Andrews, J. T. (ed.) 1985. Quaternary Environments: Eastern Canadian Arctic, Baffin Bay and Western Greenland     

Regional deformation of late Quaternary fluvial sediments in the Apennines foreland basin (Emilia,Italy)

International Journal of Earth Sciences - Our research is aimed at estimating the vertical deformation affecting late Quaternary units accumulated into the foreland basin of the Northern Apennines...     

A late Quaternary bio- and climatostratigraphy for marine sediments in the north-central part of the North Sea

BOREAS Harland, R., Gregory, Diane M., Hughes, M. J. & Wilkinson, I. P. 1978 06 01: A late Quaternary bio- and climatostratigraphy for marine sediments in the north-central part of the North Sea. Boreas, Vol. 7, pp. 91–96. Oslo. ISSN 0300–9483.
Micropalaeontological studies of three boreholes in the north-central North Sea have led to the erection of a bio- and climatostratigraphy for the area. Palaeoenvironmental interpretations have depended largely upon oceanographic concepts and changes in the micropalaeontological assemblages have been related to postulated alterations in water mass regimes. The biostratigraphy can then be utilized as a climatostratigraphy since such water mass changes are most probably linked to alterations in the circulation of the North Atlantic, and in particular to the positions of the climatically important North Atlantic Current and Polar Front. The North Sea sequences are compared to similar sections in Europe and related to the commonly accepted standard chronostratigraphy.     

Periglacial sediment variations controlled by late Quaternary climate and lake level change at Elgygytgyn Crater, Arctic Siberia

Late Quaternary sediments in a permafrost environment recovered from the Elgygytgyn Impact Crater were studied to determine regional palaeoenvironmental variability and infer past water-level changes of the crater lake. Stratigraphic analysis of a 5 m long permafrost core is based on various lithological (grain size, total organic carbon, magnetic susceptibility) and hydrochemical (oxygen isotope composition, major cation content) properties and pore ice content. The results show that alluvial sediments accumulated on top of cryogenically weathered volcanic rock. Changes in the hydrochemical properties reflect different stages of cryogenic weathering. The lithological characteristics mark the transition from an erosive site to a site with accumulation. This environmental change is linked to a relative lake level highstand at >13 000 yr BP, when a shoreline bar was formed leading to slope sedimentation. Lake level dropped by 4 m during the Holocene.     

Volatile organic compounds in Quaternary sediments

The distribution of volatile organic compounds in surface sediments varies widely with the depositional environment. Oxygen and sulfur compounds, alkenes and arenes, are more abundant than alkanes in strongly reducing sediments such as those from around Walvis Bay, West Africa. Among the compounds identified by GC-MS were toluene, benzene, 2-methyl-2-butene, 3,5-dimethylcyclopentene, 3-menthylfuran, 3-methylfuran, 2-methylbutanol, 3-methylbutanol, 3-pentanone, 2-methylthiophene, 3-methylthiophene and dimethylsulfide. Some of these compounds have the isoprene carbon skeleton.In a less reducing environment such as the Arabian Sea-Persian Gulf area, a more diverse alkene assemblage was observed including ethylene, propylene, pentenes, hexenes, cyclohexene, methylpentenes and dimethylcyclopentenes. Also, the sediments contained a few very specific alkane structures. The gem-dimethyl hydrocarbons (neopentane, neohexane, and neoheptane) were dominant among the branched hydrocarbons. The high concentration of volatile alkenes and oxygen and sulfur compounds is not observed in deep sea drilling samples at depths greater than about 100 m.     

Quaternary stratigraphy of Hong Kong coastal sediments

Geotechnical borehole data from around Hong Kong record a lithostratigraphic succession extending at least back to the early Pleistocene (Oxygen Isotope Stage 12). From these data, together with seismic data, four unconformity bounded units which accumulated between the mid Pleistocene and Holocene can be identified. This permits the development of an integrated sequence stratigraphy which can be applied to regional investigations.     

Seismites in Quaternary sediments of southeastern Altai

We study earthquake-induced soft-sediment deformation (seismites) in reference Quaternary sections of southeastern Altai. Sediments in the sections bear signature of liquefaction and fluidization and deformation is localized in thin (few centimeters to 0.5–1.0 m) continuously striking and frequently repeated layers sandwiched between undeformed sediments. The soft-sediment deformation records coseismic motion of different slip geometries. Seismic origin is also inferred for layers and lenses of coarse colluvium slid into the lake bottom from the slopes, which intrude plane-bedded silt and sand and vary in thickness from a few centimeters to one meter. The occurrence of seismic soft-sediment deformation at different stratigraphic levels of the Quaternary and in the Upper Pliocene Beken Formation confirms the high seismicity of southeastern Altai in Quaternary time.     

Calcareous nannofossils from late Jurassic sediments of the Volga Basin (Russian Platform): evidence for productivity-controlled black shale deposition

The Jurassic/Cretaceous boundary interval in the northern hemisphere is characterized by the widespread occurrence of black shales. About 60% of all petroleum source rocks comprise sediments of late Jurassic and early Cretaceous age with the origin of such black shales still under discussion. In order to better understand the factors that controlled black shale sedimentation, 78 samples were analyzed for calcareous nannofossils from two sections (Gorodische, Kashpir) of the Volga Basin (NE Russia). Calcareous nannofossils are ideal proxies for deciphering nutrient, temperature and salinity fluctuations. Additionally 58 samples from both sections were also analyzed for clay mineralogy, ¹³C_org , TOC and CaCO₃ composition. Both sections contain calcareous claystones and intercalated organic rich shales overlain by phosphorite beds. The presence of the calcareous nannofossil species Stephanolithion atmetros throughout both successions allows a biostratigraphic assignment to the S. atmetros Nannofossil Biozone (NJ 17), which corresponds to the Dorsoplanites panderi Ammonite Biozone of the Middle Volgian. The marlstones of the Kashpir section yield a well-preserved rich and diverse nannoflora, whereas all black shale beds are essentially barren of calcareous nannofossils. Only the uppermost black shale layers yield an impoverished assemblage of low diversity and abundance. Geochemical data suggest an early diagenetic nannofossil dissolution in the black shales of the Kashpir section. This is supported by the occurrence of coccoliths in black shale horizons of the Gorodische section. The assemblages in both sections are dominated by coccoliths of the Watznaueriaceae group (Watznaueria barnesae, Watznaueria fossacincta, Watznaueria britannica, Watznaueria communis), Biscutum constans and Zeugrhabdotus erectus. In Kashpir rare specimens of Crucibiscutum salebrosum occur in the higher part of the section. These taxa indicate boreal affinities. B. constans and Z. erectus are considered to be taxa indicative of a higher productive environment, while C. salebrosum is a cool-water species. From base to top of the Kashpir section, consecutive mass occurrences of different taxa/groups were observed: W. barnesae–W. fossacincta acme, W. britannica–W. communis acme, Z. erectus acme, B. constans acme (including sparse occurrences of C. salebrosum).The observed distribution patterns have been interpreted as characterizing a transition from a low productive, oligotrophic setting with high abundances of K-selected cosmopolitan species (Watznaueriaceae) and predominating marlstone sedimentation to a higher productive, mesotrophic setting. Cooler water temperatures marked by r-selection and acmes of opportunistic species (Z. erectus, B. constans) are coincident with the deposition of black shales and phosphorites in the higher part of the section. Interpretation of clay mineral distribution indicates that black shale deposition occurred under semi-arid hinterland climatic conditions concomitant with a sea level rise. This induced dysoxic conditions in the deeper parts of the Volga Basin, favoring the preservation of organic matter. The cause of the nutrient enrichment in the surface water is still unclear, but possible river water input from the continents does not seem to have been the controlling factor under a semi-arid climate. The occurrence of phosphorites in the upper part of both sections presumably indicates that enhanced productivity may be better explained by the upwelling of nutrient-rich bottom water and thereby causing the recycling of nutrients from oxidized phytoplankton back into the photic zone. This recycling effect finally may have led to an intensified phytoplankton growth which seemed to be a sufficient source for the enrichment of organic matter. This is well correlated with the increase in black shale horizons in the upper part of the Kashpir section.     

Late Quaternary Calcareous Nannofossils from the Offshore Sediments in southern Hongkong

Based upon the features of nannofossil composition, distribution, abundance and diversity, the fossil-bearing sediments exposed by five drill holes in the offshore area of southern Hongkong can be divided into the upper Middle Pleistocene, the Upper Pleistocene and Holocene. There were two palaeoclimatic stages in the Holocene in this area according to fossil palaeoecologic and sedimentation analyses: the temperature-rising stage and the warm stage. The latter involves two temperature-falling periods, which could be the major factor causing sea-level fall during that time.     

Provenance and sea-ice transportation of Mid-Pliocene and Quaternary sediments, Yermak Plateau, Arctic Ocean (ODP Site 911)

In this study, the clay and heavy mineral analysis of ODP Site 911 sediments is used to investigate the sources and transport mechanisms (sea ice and oceanic currents) of sediments in the Arctic Ocean during the Mid to Late Pliocene (3.10–2.78 Myr) and upper Quaternary (800 kyr to the present). The time period between 3.10 and 3.00 Myr is characterized by a decreasing smectite and increasing illite content, which is interpreted as reflecting cooling conditions. At the beginning of the Mid-Pliocene Global Warmth period at ∼3.00 Myr, the smectite content shows an abrupt increase. This change can also be seen as a drop in the amount of kaolinite and TOC. After 3.00 Myr the kaolinite and TOC values start to increase, probably indicating high rates of reworked glacially eroded matter. During the Pleistocene, smectite shows a lower and illite a higher fluctuation level compared with the Pliocene. This might be due to reigning glacial conditions during the Pleistocene, when the freshwater input was much lower than during the Pliocene. During the Pliocene, the fluctuating heavy minerals might reflect changes in freshwater input from the great Siberian rivers, which would have led to changes in the supply of terrigenous material delivered to the shelf by the rivers. The heavy mineral fluctuation also reflects changes in the amount of sea-ice formation, which correlates with climate variations and the freshwater input from the continent. Based on the composition of the clay and heavy mineral groups in this study, the most likely transportation path is the Siberian branch of the Transpolar Drift.