The Late Quaternary sedimentary record in Scoresby Sund, East Greenland

Until recently, little was known about the Quaternary marine sedimentary record in East Greenland. Geophysical and geological investigations in Scoresby Sund were undertaken to characterize the nature and chronology of this record. Seismic records show that almost 70% of the outer fjord system is covered by about 10 m of unlithified sediments, making direct correlation with the Quaternary records on land and the adjacent continental margin difficult. These acoustically unstratified sediments are scoured by icebergs above 550 m water depth. Almost 90% of core material is massive diamicton of Holocene age, deposited mainly from iceberg rafting and turbid meltwater. Sedimentation rates are 0.1 -0.3 m 1000 yr-¹. Thicker accumulations of unlithified Quaternary sediments in Scoresby Sund occur as sediment ridges and in two other major depocentres. A low sediment ridge runs across the mouth of Scoresby Sund, and is interpreted as an end moraine of Late Weichselian Flakkerhuk stadial age. The very restricted sediment thickness suggests that grounded ice filled the fjord during the Flakkerhuk and an ice shelf was not present. High inputs of ice rafted debris to the continental margin at about 18 000 BP indicate this as a probable age for the moraine. During the Allerød Interstadial, ice probably retreated from the outer fjord system, since massive diamictons similar to those of Holocene age are present at the base of most cores. A major depocentre of acoustically stratified sediments at the head of Hall Bredning is interpreted to represent ice proximal deposits from a glacier margin extending across the fjord. It is adjacent to dated moraines on land and is inferred to be of Milne Land stadial age (about 10 000 BP). A similar age is interpreted for acoustically laminated sediments and a moraine at the entrance of Vikingebugt, on the south side of Scoresby Sund. Dated kame terraces in the inner fjord system indicate that ice retreated to its present position 6–7000 years ago.     

Recent sedimentary processes in Scoresby Sund, East Greenland

The fjord system of Scoresby Sund on the east coast of Greenland has been the subject of two research cruises by RV Polarstern in 1988 and 1990. Most of the year, the fjord is covered by sea-ice. Sediment input takes place mostly via drifting icebergs during the short summer period. Depending on the distance to glaciers, surface sediments carry varying proportions of coarse ice-rafted debris (IRD). The degree of sediment reworking by scouring icebergs is controlled by the depth of the fjord, with the most intense reworking in areas shallower than about 450 m depth. Both IRD contribution and intensity of sediment scouring clearly control the distribution pattern of benthic organisms.     

The Aucellaelv stade at Aucellaelv, the first Weichselian glacier advance in Scoresby Sund, East Greenland

The first major Weichselian ice advance in Scoresby Sund, during the Aucellaelv stage, deposited thick till beds along the coast of Jameson Land between > 107 ka and 140 ka. and is correlated with isotope substage 5d in the marine record. This is shown by stream-cut sections at the mouth of the Aucellaelv. Jameson Land, which contain a scquence of shallow marine, fluvial and glacigene sediments extending from the Scoresby Sund glaciation (≅Saalian) to the Flakkerhuk stade (Late Weichselian). The sequence is dated by palaeoceanographic correlation with the deep-sea record, U/Th and luminescence dating, and correlated with the record in adjacent areas by mapping of marker horizons, and by mollusc fauna assemblages and amino acid analyses.     

Recent foraminifera in shelf sediments of the Scoresby Sund fjord, East Greenland

A study of sea-bottom samples from shallow waters in the northern part of Scoresby Sund, off Jameson Land, East Greenland, reveals four different foraminiferal assemblages between 1.3 and 35.6 m water depth. The shallowest samples. Assemblage SA (1.3–2.2 m), contain only very few foraminifera, presumably due to the annual repeated formation of an ice foot. Assemblage SB (3.7 and 4.3 m) is characterized by the calcareous species Haynesina nivea and H. orbiculare , while the arenaceous species Spiropleclammina biformis, Reophax arctica , and Recurvoides turbinatus dominate all the faunas of Assemblage SC (9.3–25.9 m depth). The change in fauna to the succeeding Portatrochammina bipolaris - Spiropleclammina biformis fauna (Assemblage SD, 29.6 and 35.6 m) presumably corresponds to the transition from the shallow Fjord water layer to the deeper and relatively more stable Polar water. Elphidiella hannai (Cushman & Grant) is recorded live for the first time in recent assemblages from the Atlantic Ocean.     

The origin of massive diamicton facies by iceberg rafting and scouring, Scoresby Sund, East Greenland

Almost 90% of 39 m of core material recovered from Scoresby Sund and the adjacent East Greenland shelf is massive diamicton, interpreted to be formed predominantly by the release of iceberg rafted debris and reworking by iceberg scouring. There is also likely to be a contribution from suspension settling of fines derived from glaciofluvial sources. Model calculations suggest that the ¹⁴C derived Holocene sedimentation rate of 0.1-0.3 m 1000 yr⁻¹ in Scoresby Sund can be accounted for mainly by iceberg rafting of debris. A further 4% of core material is of gravel or coarse sand lenses, interpreted to reflect iceberg dumping of debris. Intensive iceberg scouring, which reworks sea floor sediments, is observed on acoustic records from over 30 000 km² of the Scoresby Sund fiord system and the adjacent East Greenland shelf (69-72°N and 75°N). The rate of iceberg production from Greenland Ice Sheet outlet glaciers, and iceberg drift tracks on the shelf, suggests that iceberg rafting and scouring may be important over a significant proportion of the 500 000 km² area above the shelf break. The relatively extensive modern occurrence of massive diamicton, formed by iceberg rafting and scouring, together with suspension settling of fines, suggests that it may also be a significant facies in the glacier-influenced geological record. The recognition in the geological record of the massive diamicton facies described above may also indicate the former presence of fast flowing ice sheet outlet glaciers.     

The Zoned Plagioclase of the Skaergaard Intrusion, East Greenland

The variation in zoning and An-content of plagioclases in theSkaergaard intrusion was investigated using microprobe analysisand optical methods on material from the surface of the intrusionas well as from a drill core from the hidden zone of the layeredseries. The plagioclases display cryptic variation and prominentvariations in type of zoning with structural height: oscillatoryzoned and resorbed plagioclase cores are predominant in thehidden zone, unzoned cores are typical of the lower zone, andplagioclases of the upper zone display skeletal zoning. Thereverse, oscillatory and skeletal zoning of plagioclase coresis ascribed to supercooled crystallization, and not to convectionor other petrogenetic factors. The variations in type of zoningand An-content of plagioclases from the hidden zone suggestonset of convection at the same time in the cooling historyof the intrusion as is indicated by the transition between thetranquil division and the banded division of the marginal bordergroup. A crystallization model is suggested, which accountsfor the observed variations. The variation in An-content ofplagioclases from the hidden zone suggests a limited extensionof some hundred metres of the intrusion at depth.     

The ultramafic cumulate series,Gardiner complex,East Greenland

The ultramafic cumulate series of the ultramafic, alkaline and carbonatite bearing Gardiner complex in East Greenland is divided in: 1) Contact zone of plagio-clase-bearing alkaline rocks chilled to the surrounding gneisses and alkaline lavas; 2) a banded sequence of dunites to mt-pyroxenites; 3) a zoned dunite — cpx-dunite ring and 4) in the centre of the complex ol-pyroxenites and mt-pyroxenites.The zones and bands are superimposed with gradational contacts and are increasingly younger towards the centre of the complex. Primocrysts and intercumulus phases, which are equivalent to phenocryst phases in magmatic liquids show that these rocks accumulated from nephelinitic to nepheline-hawaiitic magmas and the contact rocks from less alkaline basanitic magma types similar to the regional alkaline magmas.The cumulates apparently formed in a magma chamber of a nephelinitic volcano, resting on the regional basalts of the Kangerdlugssuaq area.     

Petrogenesis of late stage magmatism at Hold with Hope, East Greenland

The Myggbukta caldera complex and a swarm of basic dykes constitute the latest Tertiary magmatism in the Hold with Hope region, East Greenland. The Sr and Nd isotope ratios of these rocks show coherent variations which extend to high ⁸⁷Sr/⁸⁶Sr and low ¹⁴³Nd/¹⁴⁴Nd values and require a contribution from continental lithosphere. Broad correlations with major element differentiation indices suggest that the continental component was incorporated during magmatic differentiation thereby favouring a crustal contamination process. Trace element concentrations are strongly correlated with isotopic compositions but display ranges for many incompatible elements which extend beyond likely crustal contaminant compositions. This is readily modelled by AFC processes in which the dominant cause of trace element enrichment is the concentration effect of fractional crystallisation rather than the composition of the contaminant. The simplest such models still require unrealistically high degrees of fractional crystallisation to explain the ten-fold enrichment of some trace elements. This can be overcome if the primary magmas entering the crust already had highly variable trace element compositions. Such variability is readily achieved if melts from different parts of the melting column escape without thorough homogenization. An AFC model which incorporates variability in parental magma composition is then able to simulate the range of compositions observed at Hold with Hope. This carries the implication that the variations observed are more readily attributed to changes in uncontaminated parental magma than to variations in the composition or amount of contaminant. Received: 5 March 1998 / Accepted: 16 June 1998     

Isotopic age and metamorphic history of the banded gneiss at Danmarkshavn,East Greenland

Along the northern part of the East Greenland coast the Caledonian structures are superimposed on an older fold system called the Carolinidian. Traces of this Carolinidian belt are preserved in a few isolated fragments within the Caledonian fold belt. According to Haller (1970) one of these fragments exhibiting the typical Carolinidian NNW to NW-trending infrastructural folds is the peninsula of Germania Land which is accessible near the Danish weather station Danmarkshavn. The rock sampled there is a banded gneiss of granodioritic composition with steeply inclined, NNW-trending layers. Isotopic age determinations yielded essentially two groups of ages: 1) 3,000±150 m.y. (zircon suite and Rb/Sr whole rock analyses of layers) and 2) 320–380 m.y. (Rb/Sr mineral isochrons, U-Th-Pb on sphene, K/Ar on hornblende and biotite). The egg-shaped zircons support a sedimentary origin of the banded gneiss and in conjunction with the Rb/Sr whole rock ages determine the age of formation of the banded gneiss (or its last high grade metamorphism) some 3,000 m.y. ago. No other Precambrian metamorphism or orogeny is recorded in the rock. The ages between 320–380 m.y. date a thermal event of lower amphibolite facies grade related to a late Caledonian spasm.The new isotopic data reveal the existence of very old rocks in the hinterland — away from the direction of thrusting—of the East Greenland Caledonian belt. With respect to the age of the Carolinidian fold system three geological interpretations are compatible with the results of this study:

The new geological map of East Greenland

NE Greenland has seen epic polar exploration, bitter territorial disputes, scientific skulduggery but contains some of the world's most striking scenery and geology. It is now documented with a new geological map from 70°N to 82°N, which documents the architecture of the Caledonian mountain range over 1300km.     

The Isotopic Composition of Strontium in the Skaergaard Intrusion, East Greenland

The isotopic composition of strontium in the different partsof the differentiated Skaergaard intrusion has been determined.The average Sr⁸⁷/Sr⁸⁶ ratio for the basic rocks was found tobe 0?7065?0?002. Higher values, between 0?7101 and 0?7303, wererestricted to the late-stage acid granophyres. The Sr⁸⁷/Sr⁸⁶ratios for the basic Skaergaard rocks are similar to those foundby previous workers. The enrichment in Sr⁸⁷ expressed in theSr⁸⁷/Sr⁸⁶ ratio is taken to indicate contamination of the acidgranophyres by a source enriched in Sr⁸⁷. From considerationsbased upon circumstantial evidence the average country rock,composed of old Precambrian acid to intermediate gneiss, isnot sufficiently enriched in.Sr⁸⁷ to account for the Sr⁸⁷ enrichmentobserved in the acid granophyres by a simple assimilation process.At the present stage of the investigation the enrichment ofthe acid granophyres in Sr⁸⁷ is unexplained.     

The last glacial cycles in East Greenland, an overview

Marine, fluvial and glacigene sediments exposed in coastal cliffs and stream-cut sections in East Greenland between latitudes 69° and 78° N display a record of Quaternary climatic and environmental change going back to pre-Saalian times (> 240 ka), but with main emphasis on the last interglacial/glacial cycle. The stratigraphical scheme is based on studies on the Jameson Land peninsula, and contains five glacial stages and stades with the Greenland ice sheet or its outlets reaching the outer coasts. Individual sites are correlated and dated by a combination of biostratigraphy, luminescence dating, amino acid analyses, as well as ¹⁴C- and uranium series dating. The pre-Weichselian Lollandselv and Scoresby Sund glaciations were the most extensive. During the Weichselian the Inland Ice margin in this part of East Greenland was apparently very stable. The Aucellaelv, Jyllandselv and Flakkerhuk stades mark the advance and subsequent retreat of outlet glaciers from the Inland Ice which advanced through the wide Scoresby Sund basin and reached the inner shelf. In-between the glacier advances, three interglacial or interstadial periods have been recognized. During the Langelandselv interglacia-tion (≅ Eemian) the advection of warm Atlantic water was higher than during the Holocene, and the terrestrial flora and insect faunas show that summer temperatures were 3–4°C higher than during the Holocene optimum. There is no unambiguous evidence for cooling in the sediments from this interval. Later, in isotope stage 5, there were apparently two ice-free periods. During the Hugin Sø interstade, stable Polar water dominated Scoresby Sund, and the terrestrial flora suggests summer temperatures 2° -3° lower than the present. The marine and fluvial sediments from the second ice-free period, the Mønselv interstade, are devoid of organic remains.     

Petrology of the Vandfaldsdalen Macrodike, Skaergaard Region, East Greenland

The Vandfaldsdalen macrodike is a layered and differentiatedgabbroic dike approximately 3?5 km long and from 200 to 500m wide. It appears to cut the eastern margin of the Skaergaardintrusion and may have served as a feeder for the Basistoppensill. The macrodike can be divided into three series of rocks:a marginal series of differentiated gabbros adjacent to thewalls of the dike; a central series of differentiated and subhorizontallylayered gabbros and ferrodiorites in the interior of the dike;and an upper felsic series of granophyric rocks with abundantquartzo-feldspathic xenoliths. The mineral and bulk-rock compositionsthrough both the marginal series and central series show progressiveiron enrichment. The most Ca-rich plagioclase (An₆₉) and mostmagnesian pyroxene (Wo₄₂ En₄₆ Fs₁₂) occur in olivine-bearingrocks of the marginal series about 5 m from the contact withwall rocks. The most Na-rich plagioclase (An₃₉) and Fe-richpyroxene (Wo₃₈ En₂₄ Fs₃₈) are in olivine-free ferrodiorite ofthe central series, about 20 m below the contact with the felsicseries. Evidence from field observations, bulk-rock chemical compositions,and Sr and Nd isotopic data indicate the felsic series formedas a mixture of the initial macrodike magma and granitic countryrock. ⁸⁷Sr/⁸⁶Sr ratios of specimens from the felsic series rangebetween 0?7129 and 0?7294. ¹⁴³Nd/¹⁴⁴Nd ratios vary between 0?51208and 0?51118. Both ratios vary serially with the SiO₂ contentsof the specimens. We suggest that the felsic series evolvedas a separate body of low density liquid which floated on thedenser gabbroic magma of the central series. Heat from crystallizationof the gabbroic magma must have diffused into the felsic layer,enabling extensive assimilation of the granitic xenoliths, butour data indicate there was very little exchange of chemicalcomponents between the two liquids.     

The Mesozoic of Western Scandinavia and East Greenland

Thick Mesozoic sediments are found offshore Norway and Denmark, and Mesozoic rocks are present and well exposed in Denmark, along the coast of East Greenland and on the arctic islands of Svalbard.
During the Mesozoic, Scandinavia and Greenland were subject to major extension in the Late Permian-Early Triassic and Late Jurassic-Early Cretaceous, prior to Cenozoic opening of the North Atlantic. Deep basins developed along the rift zones of the North Sea and between East Greenland and Norwa）; and were .filled with sediments derived from mainland Scandinavia and Greenland. The marginal areas bordering the rift zones suffered less subsidence, as did the epicontinental Barents Sea.     

A Holocene seabird record from Raffles Sø sediments, East Greenland, in response to climatic and oceanic changes

A 3.5-m-long sediment sequence from a lake on Raffles Ø, off Liverpool Land, East Greenland, was investigated for chronology, lithology, palynology and biogeochemistry. Radiocarbon-dating of plant remains and the lithology of the sediment succession indicate continuous sedimentation since deglaciation of the area prior to 10000 cal. yr BP. The postglacial palynological record shows little variation and evidence of a wind-transported pollen supply, both resulting from the geographical characteristics of Raffles Ø. Significant variations in the biogeochemical data reflect changes in aquatic bioproduction. These changes depend to some extent on climatic changes; however, they are mainly due to variations in seabird breeding colonies in the catchment which influence nutrient and cadmium supply to the lake. Large seabird breeding colonies were present between 7500 and 1900, from 1000 to 500, and since c. 100 cal. yr BP. Their absence prior to 7500 cal. yr BP may be the result of unsuitable feeding conditions close to Raffles Ø caused by a too dense or too open sea-ice cover. In contrast, between 1900 and 1000 and from 500 to 100 cal. yr BP, the seabird settlement was probably restricted by an insufficiently long breeding season due to cold climate conditions in East Greenland.     

The Eemian and Weichselian stratigraphy of the Langelandselv area, Jameson Land, East Greenland

Coastal Jameson Land is characterized by thick Quaternary deposits from the last interglacial/glacial cycle. The successions at the mouth of Langelandselv exhibit a key stratigraphy where sediments from the Langelandselv interglaciation (Eemian) are overlain by three till units interbedded with glacimarine and deltaic interstadial successions. Immediately after the retreat of glaciers after the extensive Scoresby Sund glaciation (Saalian). advection of warm Atlantic surface water surpassed what is known from the Holocene. The two lowermost Weichselian tills, deposited during the Aucellaelv and Jyllandselv stades (Early Weichselian), reflect short-lasting readvances of fjord glaciers. Luminescence dates and correlation with adjacent areas suggest ages of 110–80 ka and 70–60 ka for the Hugin Sø and the Møselv interstades, respectively.     

Fractionation and assimilation in the Borgtinderne syenite,East Greenland

The Borgtinderne nepheline-sodalite syenite is one of the major intrusions in the Tertiary igneous province of East Greenland. The syenite magma, which was evolving towards an undersaturated peralkaline residuum, underwent extensive modification by incorporation of country rock basalt, resulting in the production of a variety of hybrid syenites. Major element variation in the hybrids is essentially linear. Break-up and mechanical incorporation of the basic material was aided by amphibolitisation and metasomatism of the basalt xenoliths.     

Glacial history of interior Jameson Land, East Greenland

The plateaus between 400 and 800 m a.s.l. around the water-divides on central and eastern Janieson Land are covered by the 'Jameson Land Drift' up to 50 m thick glacial. placiotluvial and glaciolacustrine deposits. A high content of far-travelled wcsterii rocks indicates the overriding by extensive glaciers channelled from the west through the Scoresby Sund basin. The Jameson Land Drift deposits have bccn lithostratigraphically divided into two groups. each representing the sedimentary successions from one glaciation in the wider sense of the word. sediments from the lower Lollandselv glaciation are upwards delimited by a distinct periglacial surface. TL-dates suggest a prc-Saalian (approximately isotope stages 11–9) age. The following Scoreshby Sund glaciation . when most of the studied Jameson Land Drift sediments were laid down. is of Saalian age (e. isotope stages 8 6). The deposits from the Scoresby Sund glaciation are interpreted as representing a complete glaciation deglaciation succession, including proglacial sandur and glaciolacustrine sediments. followed by till deposition, with an overlying succession of glaciolacustrinc and glaciofluvial sediments. From 200–250 m to c . 400 m a.s.l. there is a driftless area, exposing Jurassic sandstones, probably a result of intensive and long-lasting periglacial erosion. Extensive occurrences of tors and of glaciofluvially (subglacially as well as subaerially) eroded canyons and channels characterize the landscape. A similar. although less well defined. upper driftless zone is found above c 500 m a.s.l. on northern Jameson Land, north of the drift-covered plateaus. During the Wcichsclian (isotope stages 5d 2). thick glacial. fluvial and marine deposits were laid down in a coastal zone below c . 200 m a.s.l., and only cold-based local ice caps seem to have existed on the interior plateaus of Jameson Land. The now driftless areas were characterized by periglacial erosion during this period.