Gregers Dam

Sedimentary response to mantle plumes: Implications from Paleocene onshore successions, West and East Greenland

The uplift history of the Upper Cretaceous–Paleocene sedimentary successions underneath the extensive Tertiary flood basalts of West and East Greenland supports recently described models for the generation of flood basalt provinces in response to rising, hot, mantle plumes. However, the sedimentary development indicates that the period of plume-related uplift prior to eruption of volcanic rocks was very short (<5 m.y.). Substantial regional uplift and faulting took place in West and East Greenland in the early Paleocene to earliest(?) late Paleocene, resulting in a basinwide unconformity. In West Greenland, the uplift was associated with fluvial peneplanation, valley incision, and catastrophic deposition; in East Greenland, it was associated with fluvial peneplanation. The cumulative uplift in West Greenland is probably on the order of several hundred meters, whereas in East Greenland, the observed uplift cannot be quantified. In both West and East Greenland, this phase was shortly followed by rapid, major subsidence associated with extensive volcanism. It is suggested that this sequence of events reflects the arrival of the North Atlantic mantle plume or plumes.

Forced regressions in a large wave- and storm-dominated anoxic lake, Rhaetian-Sinemurian Kap Stewart Formation, East Greenland

During Rhaetian-Sinemurian time a large wave- and storm-dominated lake was situated in the Jameson Land basin, East Greenland. Lake deposits consist of alternating black unfossiliferous mudstones and sheet sandstones. Anoxic conditions dominated at the lake bottom during deposition of the muds, and the water column was probably stratified. The sandstones were deposited by progradation of wave- and storm-dominated deltas in a water depth of less than 15 m. Sequence-stratigraphic interpretation suggests that the mudstones were deposited in periods of rising and very high stands of lake level, whereas progradation of the deltaic sheet sandstones took place during forced regressions caused by significant falls. The lake thus underwent a large number of fairly high amplitude changes in level, probably caused by climatic fluctuations. The high-order cycles can be grouped into several long-period cycles that show the same number of major fluctuations as published eustatic sea-level curves. This similarity suggests a causal link between eustasy and long-period variations in the lake. The Kap Stewart Formation represents one of the few ancient examples of a large wave- and storm-dominated lake, and it is probably the first documented case of abundant well-developed lacustrine forced regressions.

Palynology and sedimentology across a new marine Cretaceous-Tertiary boundary section on Nuussuaq, West Greenland

A new northern high-latitude Cretaceous-Tertiary (K-T) boundary section has been studied at Annertuneq on the north coast of Nuussuaq, West Greenland. The boundary section is situated in a succession of homogeneous dark mudstone deposited in a marine-slope environment. Identification of the boundary is based on the presence of the latest Maastrichtian palynomorphs Palynodinium grallator , Disphaerogena carposphaeropsis , Manumiella spp., and Wodehouseia quadrispina below the boundary and on the first occurrence of the earliest Danian species Senoniasphaera inornata above the boundary. Variations in sporomorph and dinoflagellate cyst abundances indicate latest Maastrichtian regression followed by early Danian transgression. The transgressive phase can be subdivided into three high-frequency transgressive-regressive cycles. Each cycle indicates upwelling and transgression, mixing with low-latitudinal water masses, and ocean conditions suggested by the peak occurrences of Senegalinium spp., Trithyrodinium fragile , and Spongodinium delitiense , respectively.

Drowning of a nearshore peat-forming environment, Atane Formation (Cretaceous) at Asuk, West Greenland: sedimentology, organic petrography and geochemistry

Abstract The Cretaceous Atane Formation, Nuussuaq basin, West Greenland, is dominated by non-marine sandstones, shales, coals, and delta-front deposits. Marine incursions are frequent, however, and near Asuk, Disko, a coal seam is encased in shallow marine deposits. Notable changes in both petrography and geochemistry occur through the seam. At the base and top of the seam, the proportions of inertinite and liptinite increase at the expense of the huminite maceral group, and within all maceral groups proportions of detrital macerals increase. Geochemical changes include systematic variations in TOC, TS, n-alkane, acyclic isoprenoid, aromatic hydrocarbon, and di- and triterpenoid biomarkers, which include a number of rearranged hopanes and hopenes, and six isomers of 28,30-bisnorhopane. The variations reflect diagenetic changes related to the availability of clay, as well as changes in depositional environment going from shallow marine conditions, through fresh water mire back to open water conditions and to the eventual return of shallow marine conditions, shown by the occurrence of delta-front deposits containing Ophiomorpha nodosa trace fossils c. 50 cm above the top of the coal seam.

Organic geochemistry and source potential of the lacustrine shales of the Upper Triassic - Lower Jurassic Kap Stewart Formation, East Greenland

Abstract The Upper Triassic — Lower Jurassic Kap Stewart Formation (Jameson Land, East Greenland) has been studied by a combination of sedimentological and organic geochemical methods (LECO/Rock Eval, sulphur, gas chromatography) in order to assess the hydrocarbon source potential of the abundant and extensive lacustrine shale intervals present in the formation. The organic matter in the shales is a mixture of algal and higher plant remains (type I and III kerogen). An organic assemblage dominated by algal material, having a rich oil potential, occurs in an interval approximately 10–15 m thick in the uppermost part of the formation. This interval has an organic carbon content up to 10% and Hydrogen Index values up to 700. The interval is consistently traceable along the exposed margins and the central part of the basin. The deposition of the uppermost shale interval coincided with the largest expansion of the lake, during a period with a stratified water column and anoxic bottom-water conditions. Locally the rocks exposed are thermally postmature due to the thermal influence of dolerite sills which intruded the Kap Stewart Formation in Tertiary time. However, the organic-rich shale interval is beyond the influence of the sills and indicates a maturity prior to or in the early stages of oil generation. Calculations of the generative potential of the lacustrine source rocks suggest that significant amounts of petroleum may have been generated in those sediments which have undergone sufficient burial in the southern and central part of the basin. Here, the contemporaneously deposited delta front and barrier island sandstones can thus be considered as potential targets for future hydrocarbon exploration. This type of play may also be of importance in other North Atlantic basins with a similar basin history.

Trithyrodinium evittii Drugg 1967 and T. fragile Davey 1969 an artificially split of one dinoflagellate cyst species–Stratigraphic and palaeoenvironmental importance

Based on morphological observations carried out on the same material, but submitted to different processing, Trithyrodinium fragile Davey 1969 is herein demonstrated to be a junior synonym of Trithyrodinium evittii Drugg 1967. From both original descriptions, the only way that the two species can be separated is by the presence or the absence of a thick brown organic layer on the surface of the endocyst. The present study proves that this is an artificial separation caused by different processing techniques. As a result, T. evittii is emended in order to encompass specimens, wholly or partially exhibiting this brown organic layer and previously attributed to T. fragile. These new observations also have stratigraphic and palaeoenvironmental implications. Combination of both synonym lists reveals that T. evittii, which is regarded as a warm water species (58°N to 52°S) in the latest Cretaceous, migrated to higher latitudes (80°N to 75°S) in the earliest Paleocene. Consequently, an increase in oceanic circul...

Sequence stratigraphic correlation of Lower Jurassic shallow marine and paralic successions across the Greenland-Norway seaway

The Lower Jurassic Neill Klinter Formation of Jameson Land, East Greenland, was deposited in a wide, shallow and tidally influenced marine embayment. The formation is interpreted within a sequence stratigraphic framework and a sequence stratigraphie correlation with the time-equivalent Tilje, Ror and Not Formations on the mid-Norwegian shelf is presented. This comparison shows that the Lower Jurassic in both regions consists of six sequences. The Neill Klinter Formation is characterized by near absence of well-defined parasequences. This pattern is interpreted as reflecting a high rate of influx of sand in the land-locked embayment situated at the margin of the Greenland craton. Continuous filling of accommodation space and erosion thus led to amalgamation of parasequences, and poor development of facies cyclicity. The correlative successions on the Halten Terrace, mid-Norway shelf are less tidally influenced. Well-developed parasequences are characteristic, and the overall content of heteroliths and mudstones is higher, reflecting a more distal position in the seaway with respect to the Norwegian cratonic margin, and a slower infilling of new accommodation space. The present study is probably the first published attempt to undertake a long distance high-resolution sequence stratigraphie correlation across the North Atlantic. A direct correlation of systems tracts on a scale of few tens of metres between East Greenland and the mid-Norwegian shelf seems to be possible, but independent biostratigraphic testing of the correlation proposed here is still required.

Exploration significance of lacustrine forced regressions of the Rhaetian-Sinemurian Kap Stewart Formation, Jameson Land, East Greenland

During Rhaetian-Sinemurian time a large wave- and storm-dominated hydrologically closed lake was situated in the Jameson Land basin, East Greenland. The lacustrine succession consists of alternating black unfossiliferous organic-rich mudstones and sheet sandstones. Anoxic conditions dominated at the lake bottom during deposition of the muds, and the water column was probably stratified. Water depth during deposition of the muds exceeded several tens of metres and probably reached a hundred metres. The sandstones were deposited by progradation of wave-dominated deltas in a water depth of less than 15 m. High-resolution sequence stratigraphic interpretation suggests that the mudstones were deposited in periods of rising and high stand of lake level, whereas progradation of the deltaic sheet sandstones took place during forced regressions caused by significant fall. The lake thus underwent a large number of fairly high-amplitude changes in level, probably caused by climatic fluctuations. The high-frequency cycles can be grouped into several low-frequency cycles that show the same number of major fluctuations as published eustatic sea-level curves. This similarity suggests a causal link between eustasy and long-period variations in lake level. Recognition of lowstand shorelines in association with the process of forced regression has led to recognition of a new stratigraphic play type in the Jameson Land basin. Lowstand deltaic sandstone bodies, isolated in organic-rich lacustrine shales with a suitable maturity for hydrocarbon generation, occur in an extensive area in southern and central Jameson Land. In these parts of the basin this play type may be attractive for exploration assuming optimal conditions for hydrocarbon preservation. The Kap Stewart black shale-forced regressive sandstone play type may be applied to similar lacustrine successions elsewhere.