Eastern North Greenland Research Articles

Introduction

The advent of aircraft to arctic exploration heralded a new age in North Greenland geology. Exactly 45 years elapsed from the time that Lauge Koch first conducted airborne reconnaissance over eastern North Greenland until the Geological Survey of Greenland (Grønlands Geologiske Undersøgelse, GGU) launched the major regional geological programme, the North Greenland Project (1978-80, 1984-85), which has provided the bulk of the geological information upon which this present volume is based.

Prevalence of Trichinella sp. in polar bears (Ursus maritimus) from northeastern Greenland

Prevalence of Trichinella sp. in polar bears (Ursus maritimus) from northeastern Greenland

Upper ocean internal waves in the marginal ice zone of the northeastern Greenland Sea

Oceanographic measurements obtained in the northeastern Greenland Sea—Fram Strait region were studied in order to characterize internal wave activity in the marginal ice zone (MIZ) of the Arctic Ocean. Experiments were performed with an array of four horizontally separated current meters and a CTD instrument in 1984 as part of the Marginal Ice Zone Experiment. Spectra of horizontal and vertical motion show that within the frequency range from the inertial frequency to 3 cph the MIZ internal wave field is similar in spectral shape and energy content to the wave field found beneath Arctic pack ice. Above 3 cph the MIZ spectra contain more energy than expected based upon both beneath‐ice measurements and the Garrett‐Munk model spectra. Elevated energy levels at high frequencies are shown to be caused by intermittent increases in internal wave activity occurring on time scales from 2 to 12 hours. Phase differences between pairs of time series, computed during the passage of several packets of internal waves, are used to estimate horizontal wave number vectors. A comparison of the calculated wave number vectors to a dispersion relation derived from a simple normal mode model of internal waves suggests that the wave packets may be adequately described as being comprised of lowest‐mode, horizontally propagating internal waves. The interaction of ice‐bottom topography with a sharp, elevated pycnocline is explored as a possible source of the intermittent increases in wave activity. Spectra of vertical displacement and velocity computed from time series of both temperature and density are presented in order to show the influence of intrusive activity in the MIZ. Differences in both spectral shape and energy content, found at frequencies below 2.5 cph, emphasize the need for careful interpretation of temperature‐based measurements of vertical motion obtained over long periods of time in the MIZ.

The thyra Ø flora: Toward an understanding of the climate and vegetation during the early tertiary in the high arctic

The Late Paleocene-Early Eocene Thyra Ø flora from eastern North Greenland is represented by a collection of 30–31 fossil plant types of which 22–23 are angiosperm leaf types. The flora records warm temperate climatic conditions with the absence of frost and is based mostly on comparison of the nearest living relatives to genera in the Thyra Ø flora. Climatic conditions implied by this method is in contrast to the cool temperate conditions indicated by this method is in contrast to the cool temperate conditions indicated by leaf physiognomy. Unpublished Early Tertiary leaf collections from Spitsbergen also record cool temperate conditions based on leaf margin data even though many taxa representing warmer climatic conditions are present. It is suggested here that the response to the low Arctic light levels was a main factor in shaping the character of the Early Tertiary Arctic vegetation, including leaf physiognomy and species composition. This has implications toward the use of leaf physiognomy for determining past climates in the Arctic.

Prevalence of Trichinella sp. in polar bears (Ursus maritimus) from northeastern Greenland

The occurrence of infections with Trichinella sp. in polar bears (Ursus maritimus) from northeastern Greenland has been studied by examination of muscle samples, mainly diaphragm, from 38 animals shot during the period 1983-1987. Trichinella larvae were demonstrated in 12 bears (32%) with an average of 9.2 larvae/g muscle tissue. No bears younger than three years old were infected. The prevalence of Trichinella among bears of the age group 3-4 years was 25% and 53% among older animals.

Upper ocean internal waves in the marginal ice zone of the northeastern Greenland Sea: Eckert, E.G. and T.D. Foster, 1990. J. geophys. Res., 95(C6):9569–9574

Upper ocean internal waves in the marginal ice zone of the northeastern Greenland Sea: Eckert, E.G. and T.D. Foster, 1990. J. geophys. Res., 95(C6):9569–9574

Stratigraphy and depositional history of the Upper Palaeozoic and Triassic sediments in the Wandel Sea Basin, central and eastern North Greenland

A lithostratigraphic scheme is erected for the Lower Carboniferous to Triassic sediments of the Wandel Sea Basin, from Lockwood Ø in the west to Holm Land in the east. The scheme is based on the subdivision into the Upper Carboniferous - Lower Permian Mallemuk Mountain Group and the Upper Permian - Triassic Trolle Land Group. In addition the Upper Carboniferous Sortebakker Formation and the Upper Permian Kap Kraka Formation are defined. Three formations and four members are included in the Mallemuk Mountain Group. Lithostratigraphic units include: Kap Jungersen Formation (new) composed of interbedded limestones, sandstones and shales with minor gypsum - early Moscovian; Foldedal Formation composed of interbedded limestones and sandstones -late Moseovian to late Gzhelian; Kim Fjelde Formation composed of well bedded Iimestones - late Gzhelian to Kungurian. The Trolle Land Group includes three formations: Midnatfjeld Formation composed of dark shales, sandstones and limestones - Late Permian; Parish Bjerg Formation composed of a basal conglomeratic sandstone overlain by shales and sandstones - ?Early Triassic (Scythian); Dunken Formation composed of dark shales and sandstones - Triassic (Scythian-Anisian). The Sortebakker Formation (new) is composed of interbedded sandstones, shales and minor coal of floodplain origin. The age is Early Carboniferous. The Kap Kraka Formation (new) includes poorly known hematitic sandstones, conglomerates and shales of Late Permian age.

Carbon isotope variations in the Upper Carboniferous - Pennian Mallemuk Mountain Group, eastern North Greenland

Isotope data from Late Palaeozoic limestones of the Wandel Sea Basin in eastern North Greenland show a variation of b13C from 0.0 %o to 5.7 %o vs PDB. Carbonates depleted in 13C occur in the basal part of lower Moscovian, upper Moscovian and middle Gzhelian transgressive sequences. 13C enriched limestones occur later in the cycles. The most 13C enriched limestones occur in the youngest (late Early Permian-early Late Permian) part of the sequence in Amdrup Land. The isotopic data is believed to represent changes in the global carbon cycle. Thus 13C enriched carbonates correlate to periods of burial of organic carbon mostly as coal, while 13C depleted carbonates formed as the result of erosion and oxidation of organic carbon during sea-level low stands.

Wandel Sea basin—A new synthesis of the late Paleozoic to Tertiary accumulation in North Greenland

The Wandel Sea basin in eastern North Greenland is the least known of the onshore depositional centers associated with the formation of the Arctic and North Atlantic oceans. Whereas the main features of Svalbard and the Sverdrup basin have been known for many years, it has only recently been possible to investigate the Wandel Sea basin in any detail. In the course of recent investigations, the concept of a classic bull9s eye type of accumulation in North Greenland has become increasingly difficult to maintain. This paper presents an alternative model involving a complex series of events with an overall change from elongate rift basins to a strike-slip-dominated structural belt. Individual events in this development provide evidence of early steps in the extended processes leading up to ocean formation.

Acritarchs from the Kap Holbæk Formation, North Greenland

In two recent general summaries of the geology of northern Greenland (Peel, 1986; Higgins et al., in press) brief reference was made to acritarchs from the Kap Holbæk Formation of eastern North Greenland indicative of a Proterozoic age. The age determination is of particular interest since the formation has been interpreted widely as of Cambrian age. This short note more fully documents the evidence for this revised age determination.

Palynology in a polar desert, eastern North Greenland

A pollen diagram from a lake in a polar desert in eastern North Greenland records the regional vegetation history back toc.7,000 years calBP (6,000 years convBP) in this extreme environment, which presents the coldest thermal regime where vascular plants can grow. The diagram shows that polar desert developed from sparse high arctic tundra atc.4,300 years calBP (3,900 years convBP), owing to reduced summer heat. Also adjacent parts of high arctic Greenland, Canada and Svalbard suffered environmental decline, and polar deserts ‐ presently restricted to a narrow fringe of land at the shores of the Arctic Ocean ‐ were even more restricted before this time. Like other arctic vegetation types, polar desert is highly sensitive to summer temperatures, and its southern limit coincides with the isotherm for mean July temperatures of 3.5d̀C. A comparison with the Northwest European ice‐age pollen record shows no evidence of summers as cold as those now prevailing in the extreme north, and the results support the contention that the present Arctic and the ice‐age mid‐latitude environments are not identical.

Palaeomagnetism of middle Proterozoic (c. 1.25 Ga) dykes from central North Greenland

From a nunatak in central North Greenland (81.5°N, 44.7°W) nine sites of Middle Proterozoic basic dykes, cutting Archaean basement, were palaeomagnetically investigated. After AF and thermal cleaning the nine dyke sites and three adjacently baked gneiss sites give a stable characteristic remanent mean direction of D = 265°, I = 21.5° (N= 12, α95= 5.6°), the direction being confirmed by a detailed and positive baked contact test. The polarity of the dykes in the nunatak area is opposite to that of the Zig-Zag Dal Basalts and the Midsommersø Dolerites in eastern North Greenland some 200–300 km away, the volcanics of which are assumed to be of similar age (about 1.25 Ga). The remanent directions of the two sets of data are antiparallel within the 95 per cent significance level of confidence. When rotating Greenland 18° clockwise back to North America by the ‘Bullard fit’, the pole of the central North Greenland dolerites (NDL) falls at (14.3°N, 144.3°W). The reversed pole (14.3°S, 35.7°E) fits well on to the loop between 1.2 and 1.4 Ma on the apparent polar wander swath of Berger & York for cratonic North America. The palaeomagnetic results from the Middle Proterozoic basic dykes from central North Greenland thus strengthen previous palaeomagnetic results from the Midsommersø Dolerites and Zig-Zag Dal Basalts from the Peary Land Region in eastern North Greenland, suggesting that Greenland was part of the North American craton at least for the period between c. 1.3 and 1 Ma (and probably up to the end of Cretaceous time). The major geographical meridian of Greenland was orientated approximately E–W, and the palaeo-latitude of Greenland was about 10°–15°.

Modeled acoustic propagation through an ice edge eddy in the East Greenland Sea Marginal Ice Zone

A detailed modeling study of the relationship between the various oceanographic features of a cyclonic eddy located at the ice edge off the coast of northeastern Greenland and the eddy's effects on the propagation of acoustic energy is presented. The effects of the eddy on acoustic propagation as a function of location, depth, and frequency of the acoustic source and depth of the receiver for nominal frequencies of 50 Hz and 1 kHz are discussed. Significant differences sometimes greater than 20 dB in the acoustic field were observed for variations in any of the source and receiver parameters. The sound speed structure of the eddy makes propagation loss and acoustic modes very dependent on direction and location. A significant finding is that the interior environment of the eddy can generate a frequency dependence on propagation loss so that 1 kHz sustains a loss as much as 20 dB smaller than does 50 Hz, i.e., dispersion phenomenon. A similar propagation loss anomaly was observed and appears to be due to a combination of marginal ice zone (MIZ) fine structure and interference patterns created by reflections from the sea surface. Such an anomaly can exist in the MIZ with or without the eddy environment. Both of these frequency anomalies are a function of source and receiver depth. Low‐frequency (50 Hz) energy in the presence of the eddy can experience stronger downward refraction and thereby possibly suffer greater bottom interaction than high frequencies (1 kHz). As compared to the noneddy environment, propagation in the presence of the eddy, for any of the source and receiver depths studied, can result in changes in the levels and distribution of energy in the acoustic field by more than 10 dB as well as changes in the mode of propagation of some rays (e.g., refracted/surface‐reflected to refracted/refracted).

Fine structure, internal waves, and intrusions in the marginal ice zone of the Greenland Sea

Two series of 40 temperature and salinity profiles were made in the marginal ice zone of the northeastern Greenland Sea/Fram Strait region. The first series showed much intrusive activity, while the second was dominated by internal wave activity. Displacement dropped spectra showed spectral levels scaled by Desaubies' (1976) analytic representation of the Garrett‐Munk (1975) model to be comparable to those from lower latitudes though probably somewhat lower. Temperature dropped spectra showed severe contamination by intrusions. It is concluded that temperature spectra cannot be used to determine internal wave activity of the upper ocean in the marginal ice zone.

The Sjælland Fjelde Formation: a new Ordovician formation from eastern North Greenland

The name Sjælland Fjelde Formation is introduced for a varied sequence of shallow-water platform dolomites and dolomitic limestones, about 105 m in thickness, in Kronprins Christian Land, eastern North Greenland. The new formation lies between the previously described Wandel Valley and Børglum River Formations. Conodont faunas indicate that the Sjælland Fjelde Formation is of Middle to earliest Late Whiterockian (early Middle Ordovician) age and that it can be eorrelated with the upper part of the Wandel Valley Formation of Peary Land to the north-west.

The age of the Danmarks Fjord Member, eastern North Greenland

Conodonts of late Early Ordovician age (late Canadian, early-middle Arenigian) are identified from the Danmarks Fjord Member of the Wandel Valley Formation at its type locality near the head of Danmark Fjord, eastern North Greenland. The identifications confirm recent suggestions of an Early Ordovician age for the member made on lithostratigraphic grounds, and refute earlier opinions that the dolomite was probably of Early Cambrian age.

Early Ordovician trilobites from the Wandel Valley Formation, eastern North Greenland

A small trilobite fauna is described from the Wandel Valley Formation of Kronprins Christian land, eastern North Greenland. It has a specific composition identical to the fauna from the Catoche Formation, western Newfoundland, which is typical of the shallow water bathyurid biofacies of the eastern part of the Ordovician Laurentian palaeocontinent. The fauna is of early Ordovician age, trilobite Zone H, equivalent to the early Arenig.

Geology of central and eastern North Greenland

A historical review of geological research in North Greenland is followed by a summary of the main results of the 1978-80 GGU expeditions to the region. New outcrops of Archaean and early Proterozoic crystalline rocks are recorded only as xenoliths in dykes and volcanic centres. A revised stratigraphy is applied to the middle Proterozoic Independence Fjord Group sandstones, while petrographic and isotopic studies have been made of the cross-cutting Midsommersø dolerites and the overlying Zig-Zag Dal Basalt Formation. No convincing evidence has been found of a Carolinidian orogenic episode separating these units from succeeding late Proterozoic sedimentary sequences. Lower Palaeozoic sediments dominate North Greenland and are divided into southern shelf and northern trough successions; new or revised stratigraphies are now applied in both settings. The shelf-trough boundary can be shown to have moved south with time, and a major early Silurian expansion of the trough is related to shelf subsidence and a new phase of turbidite deposition derived from the rising East Greenland Caledonian mountains. Devonian - Middle Carboniferous (Ellesmerian) deformation brought deposition to a close and created the North Greenland fold belt, in which deformation intensity and metamorphic grade increase northwards. Thin-skinned thrusting in association with west or south-facing folds is important in southern areas; this is one of the main differences in interpretation compared to earlier work in the fold belt. New outcrops of post-ElIesmerian sediments (Wandel Sea Basin) have mainly been recorded as fault or thrust bounded sequences; a new stratigraphy is applied to the Wandel Sea Basin succession. Cretaceous - Tertiary events include a suite of volcanic centres, dyke swarms, the Kap Washington Group volcanics, and faults and thrusts of Tertiary (Eurekan) age; all have been studied anew, as have the Quaternary deposits.

Crustal inhomogeneities and seismicity near the margins of the North Atlantic Ocean

Some very pronounced crustal inhomogeneities have been found in the North Sea and in Greenland, in regions which were adjacent to each other before the opening of the North Atlantic Ocean by sea-floor spreading. Some of these regions of inhomogeneities are zones of relatively high seismicity, while others are aseismic. In the North Sea, the Viking Graben has earthquakes, while its southern continuation, the Central Graben, is almost aseismic. In eastern Greenland, there are only few earthquakes near the Mesozoic graben, while there is a prominent earthquake zone at the coast line in north-eastern Greenland. It is concluded that, superposed on the apparent similarities in the two regions, some differences in stress conditions or crustal weakness patterns must exist.

Notes on the Holocene marine fauna of eastern North Greenland

A list of invertebrates, notably molluscs, from the raised Holocene marine sedimets in eastern North Greenland is given. The faunas have low diversity, and contain an element of Arctic sublittoral and bat­hyal species indicative of cold surface water.