Lithostratigraphy of the Late Saalian to Middle Weichselian Skærumhede Group in Vendsyssel, northern Denmark

The Quaternary sedimentary succession in Vendsyssel, northern Denmark, contains a unique, high‐resolution record of the last interglacial and glacial periods. There is still much debate, however, about the timing and ice extent in this southwestern part of the Scandinavian Ice Sheet, particularly during the Middle Weichselian. In this study, a detailed lithostratigraphical subdivision is established for the Late Saalian to Middle Weichselian Skærumhede Group on the basis of numerous, up to 250 m deep, boreholes in Vendsyssel. The sediments mainly consist of marine clays, glaciolacustrine sediments and tills, and the total thickness of the Skærumhede Group is up to 140 m. Marine intervals have been used as stratigraphical marker units to separate the formations indicative of ice‐sheet activity in Vendsyssel, and the timing of the events has been constrained by a large number of optically stimulated luminescence (OSL) and radiocarbon ages. The Skærumhede Group is subdivided into seven formations and two members, reflecting shifts between marine and terrestrial sedimentation caused by fluctuations of the Scandinavian Ice Sheet and changes in sea level. The lowermost Skærumhede Till Formation was deposited directly on top of the bedrock during the Warthe advance c. 160–140 kyr BP. Above, there are fine‐grained marine sediments, subdivided into the Lower, Middle and Upper Skærumhede Clay Formations. The marine formations are separated by the Brønderslev Formation related to the Sundsøre ice advance from the north c. 65–60 kyr BP, and the Åsted Formation, deposited during the Ristinge advance from an east–southeastern direction c. 55–50 kyr BP. The uppermost formation in the group is the Lønstrup Klint Formation, which is an upwards‐coarsening sequence of mainly glaciolacustrine sediments deposited prior to the Kattegat advance c. 30–29 kyr BP. The new evidence from Vendsyssel has shown that the Skærumhede Group covers a large area, and that it can be used as a regional stratigraphical marker horizon. Furthermore, it contributes to a better understanding of the timing and extent of glacial events during the Late Saalian to Middle Weichselian in southwest Scandinavia.     

Early Last Interglacial palaeoenvironments in the western Baltic Sea: benthic foraminiferal stable isotopes and diatom‐based sea‐surface salinity

Knudsen, K. L., Jiang, H., Kristensen, P., Gibbard, P. L. & Haila, H. 2011: Early Last Interglacial palaeoenvironments in the western Baltic Sea: benthic foraminiferal stable isotopes and diatom‐based sea‐surface salinity. Boreas, 10.1111/j.1502‐3885.2011.00206.x. ISSN 0300‐9483. Stable isotopes from benthic foraminifera, combined with diatom assemblage analysis and diatom‐based sea‐surface salinity reconstructions, are used for the interpretation of changes in bottom‐ and surface‐water conditions through the early Eemian at Ristinge Klint in the western Baltic Sea. Correlation of the sediments with the Eemian Stage is based on a previously published pollen analysis that indicates that they represent pollen zones E2–E5 and span ～3400 years. An initial brackish‐water phase, initiated c. 300 years after the beginning of the interglacial, is characterized by a rapid increase in sea‐surface and sea‐bottom salinity, followed by a major increase at c. 650 years, which is related to the opening of the Danish Straits to the western Baltic. The diatoms allow estimation of the maximum sea‐surface salinity in the time interval of c. 650–1250 years. After that, slightly reduced salinity is estimated for the interval of c. 1250–2600 years (with minimum values at c. 1600–2200 years). This may be related to a period of high precipitation/humidity and thus increased freshwater run‐off from land. Together with a continuous increase in the water depth, this may have contributed to the gradual development of a stratified water column after c. 1600 years. The stratification was, however, particularly pronounced between c. 2600 and 3400 years, a period with particularly high sea‐surface temperature, as well as bottom‐water salinity, and thus a maximum influence of Atlantic water masses. The freshwater run‐off from land may have been reduced as a result of particularly high summer temperatures during the climatic optimum.     

Palaeoenvironments of a complete Eemian sequence at Mommark, South Denmark: foraminifera, ostracods and stable isotopes

A new investigation of the coastal cliff section at Mommark in southern Denmark has revealed a complete Eemian interglacial sequence for the first time in the southwestern Baltic area. Environmental changes through the lacustrine and marine interglacial deposits are discussed on the basis of foraminiferal assemblages and stable isotope composition as well as ostracods. In general, the assemblages indicate relatively high temperatures throughout the Eemian, and the Lusitanian foraminiferal species Pseudoeponides falsobeccarii Rouvillois has been reported for the first time from the Eemian of northwest Europe. A floating chronology of the deposits is based on a previously published correlation of the local pollen stratigraphy with annually laminated sequences in northern Germany. An initial early Eemian lacustrine phase, with ostracodal indication of deposition in a large freshwater lake, lasted until c. 300 years after the beginning of the interglacial, i.e. to the transition between the regional pollen zones E2 and E3. After that, marine conditions persisted almost throughout the interglacial, and the Cyprina Clay was deposited. The foraminiferal and ostracodal assemblages indicate that relatively deep water prevailed in the area until c. 6000 years after the beginning of the interglacial. However, both the foraminiferal assemblages and the oxygen isotope results show that a trend from relatively high salinity to lower salinity conditions had begun already at about 4000 years. After c. 6000 years the fauna indicates a gradual change to shallower water and further reduction in salinity, the latter also being reflected by a general decrease in the oxygen isotope values. The marine deposition ended at c. 10 600 years after the beginning of the Eemian, i.e. within the topmost part of pollen zone E7. This was succeeded by a late Eemian and early Weichselian freshwater phase.     

The Lundergård Clay and its Foraminifera, a new formation in the marine Quaternary of Denmark

Knudsen, Karen Luise: The Lundergard Clay and its Foraminifera, a new formation in the marine Quaternary of Denmark. Boreas, Vol. 1, pp. 289–297. Oslo, 1st December, 1972.
Samples from marine Quaternary clay deposits at Lundergård in Vendsyssel have been analysed for their content of Foraminifera. The clay, which is called the Lundergård Clay, contains a typical arctic foraminifer fauna with Quinqueloculina stalkeri and Elphidium ustulatum as characteristic species. To attempt an age determination of the Lundergård Clay, the fauna is compared with foraminifer assemblages from other marine Quaternary deposits of Vendsyssel and adjacent areas. The deposit may represent a hitherto unknown facies of the Older Yoldia Clay of Vendsyssel, which is supposed to be of Weichselian interstadial age, or it may be older and can perhaps be correlated with the Holderness Basement Till of Saale interstadial age.     

Wolf Volcano, Galapagos Archipelago: Melting and Magmatic Evolution at the Margins of a Mantle Plume

Wolf volcano, an active shield volcano on northern Isabela Islandin the Galápagos Archipelago, has undergone two majorstages of caldera collapse, with a phase of partial calderarefilling between. Wolf is a typical Galápagos shieldvolcano, with circumferential vents on the steep upper carapaceand radial vents distributed in diffuse rift zones on the shallower-slopinglower flanks. The radial fissures continue into the submarineenvironment, where they form more tightly focused rift zones.Wolf's magmas are strikingly monotonous: estimated eruptivetemperatures of the majority of lavas span a total of only 22°C.This homogeneity is attributed to buffering of magmas as theyascend through a thick column of olivine gabbroic mush thathas been deposited from a thin, shallow (<2 km deep) subcalderasill that is in a thermochemical steady state. Wolf's lavashave the most depleted isotopic compositions of any historicallyactive intraplate ocean island volcano on the planet and haveisotopic compositions (except for ³He/⁴He) indistinguishablefrom mid-ocean ridge basalt erupted from the GalápagosSpreading Center (GSC) 250–410 km away from the peak ofinfluence of the Galápagos plume. Wolf's lavas are enrichedin incompatible trace elements and have systematic major elementdifferences relative to GSC lavas, however. Wolf's magmas resultfrom lower extents of melting, deeper melt extraction, and agreater influence of garnet compared with GSC magmas, but Wolfand the GSC share the same sources. These melt generation conditionsare attributed to melting in a thermal and mechanical boundarylayer of depleted asthenosphere at the margins of the Galápagosplume. The lower degrees of melting and extraction from deeperlevels result from a thicker lithospheric cap at Wolf than existsat the GSC. KEY WORDS: caldera; Galápagos; mush; partial melting; plume     

The NCGIA core curricula in GIS and remote sensing

Since the development of the original NCGIA Core Curriculum in GIS (Goodchild and Kemp 1990), the National Center for Geographic Information and Analysis has been providing support and direction to the GIS education community. Following the success of the original Core Curriculum, three new curricula are now under development. All are being constructed and distributed on the World-Wide Web and involve international authorship and editorial input. This paper outlines the origins of these projects and some of the issues related to the development of Web-based instructional materials that they raise.     

A preliminary study of the dynamics of a modern draa, Algodones, southeastern California, USA

A transverse crescentic draa in the Algodones dune field, California, was monitored for a year using surface process mapping, aerial photography and supplemental wind measurement. The draa is oriented by the long-term resultant wind, whereas its superimposed features are in equilibrium with the bedform-modified secondary airflow. Surface airflow and the movement of superimposed bedforms is typically oblique or parallel to the draa brinkline, particularly on the lee slope. Comparison of measurements of draa movement and sand deposition on the lee slope, with expected rates calculated from wind data and draa size, confirm that there is a significant component of sand flow parallel to the draa brinkline. The internal structure being generated at the base of the draa lee slope is inferred from the surface processes active there. Within the space of a kilometer two types of compound cross-strata, separated by an area of simple cross-strata, are being produced. This has significant implications for interpretations of ancient aeolian strata. Variations in internal structure types found in lateral sequence may be generated by one complex bedform, and these cross-strata may be simple or compound. Second-order bounding surface orientations indicate resultant primary palaeowind directions; compound cross-strata dip directions indicate secondary flow conditions. The existence of cross-strata dip directions oblique or perpendicular to the second-order surface indicates longitudinal secondary flow on the lee face, but not necessarily a longitudinal or oblique draa. Without further detailed knowledge about various draa configurations and behaviour, stratification attributed to draas can be used only to interpret activity on the lower draa lee face.     

Comparison of Quaternary interglacial periods in the Iceland Sea

Five Quaternary interglacial periods are represented in core 57-7 from the Iceland Sea. Analysis of coccolith and planktonic foraminiferal assemblages from the interglacial periods (Oxygen Isotope Stages 1, 5, 7, 9 and 11) shows both similarities and differences in the assemblages. The differences indicate that the palaeoenvironment was not identical in the five interglacial periods. Oxygen Isotope Substage 5e reflects the warmest period, with the greatest inflow of warm Atlantic water. During this interval the Arctic Front apparently had a more westerly position than it has today. Substages 5a and 5c were periods when Arctic water masses dominated, as at the present day. In Oxygen Isotope Stages 7 and 9 inflow of Atlantic water was limited. Oxygen Isotope Stage 11 reflects a period of great productivity, but the region was still dominated by Arctic water masses. The position of the Arctic Front was possibly close to that of today, but not at the extreme western position it had in Oxygen Isotope Substage 5e.