Henrik Nøhr-Hansen

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.

Dinoflagellate cyst stratigraphy of the Palaeogene strata from the Hellefisk-1, Ikermiut-1, Kangâmiut-1, Nukik-1, Nukik-2 and Qulleq-1 wells, offshore West Greenland

Abstract A new Palaeogene dinoflagellate cyst stratigraphy from offshore West Greenland has been described based on the strata from the Hellefisk-1, Ikermiut-1, Kangâmiut-1, Nukik-1, Nukik-2 and Qulleq-1 wells. Twenty-one palynological intervals are defined from the Late Eocene to the late Early Paleocene. This stratigraphy has been correlated with a new microfossil zonation and previous established North Sea zonations. The stratigraphy and well correlation are based on last appearance datum events and abundances of stratigraphically important species from 355 samples, 148 of which are sidewall core samples. A major middle Eocene hiatus spanning the early Lutetian and a major Early Paleocene hiatus spanning the Late Santonian, Late Cretaceous to the early Danian have been recognised from the offshore deposits.

Upper Barremian to upper Albian (Lower Cretaceous) dinoflagellate cyst assemblages, Canadian Arctic Archipelago

Abstract The dinoflagellate cyst assemblages from four Lower Cretaceous sections from Melville Island, Axel Heiberg Island and Ellesmere Island in the Northwest Territories, Canada are described. The sections represent the upper part of the Isachsen Formation and the Christopher Formation. The strata studied comprise a composite stratigraphic section of approximately 1400m of shale and siltstone deposits. The study of 33 samples yielded 83 dinoflagellate cyst species, which date the strata as late Barremian to early late Albian. The flora discussed is correlative with assemblages described from other parts of the arctic area. This study provides new and detailed palynological information about the Lower Cretaceous of the Arctic Islands. Comments are included on the morphology and ranges of: Acanthaulax sp. aff. A.? tenuiceras, Apteodinium sp. cf. A. maculatum ssp. grande, Balmula sp. cf. B. tripenta, Batioladinium longicornutum, Batioladinium shaftesburiense, Canningia reticulata, Catastomocystis spinosa,...

Arctic black shale formation during Cretaceous Oceanic Anoxic Event 2

The Late Cretaceous Oceanic Anoxic Event 2 (OAE2) represents a major perturbation of the global carbon cycle caused by the widespread deposition of organic-rich black shales. Although the paleoceanographic response and the spatial extent of bottom-water anoxia in low and mid-paleolatitudes are reasonably well constrained for OAE2, similar data from high paleolatitudes are lacking. Here, we present palynostratigraphy and organic-carbon isotope stratigraphy from the Sverdrup Basin, Axel Heiberg Island (Canada). It is shown that episodes of high marine organic-carbon burial at paleolatitudes of ∼70°N is contemporaneous with the widely observed occurrence of black shale deposition during OAE2. Paleontological, lithological, and geochemical data indicate normal marine conditions with persistent anoxic bottom waters during OAE2. The results imply that the high marine primary productivity pulse during OAE2 may have caused massive organic-carbon burial on the Arctic shelf in general, with important implications for hydrocarbon source-rock distribution in the Arctic region.

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...

Ordovician spores with trilete rays from Washington Land, North Greenland☆

Abstract Late Ordovician dispersed ornamented spores with trilete rays are recorded from the Troedsson Cliff Formation in Washington Land, western North Greenland. Biostratigraphical information from conodonts, acritarchs and chitinozoa confines the spores to the lower Pusgillian Stage, early Ashgill. A new genus, Besselia , and two new species, Besselia nunaatica and B. polaris , are proposed.

Sequence stratigraphy and lateral variability of Lower Cretaceous clinoforms in the southwestern Barents Sea

An extensive seismic database covering an area of 100,000 km2 (38,610 mi2) and 16 wells are integrated to define a sequence-stratigraphic framework for the Lower Cretaceous succession in the southwestern Barents Sea. Seven sequences (S0–S6) are defined, and the geometry, trajectory, and lateral variability of decompacted seismic clinoforms are described to elucidate the depositional history of the basin and to better understand coarse-grained sediment transport from the shelf to basin. Three different clinoform scales are recognized: (1) clinoform sets with 35–60 m (115–197 ft) height, interpreted as deltaic or shoreline clinoforms; (2) clinoform sets with 60–110 m (197–361 ft) height, interpreted as sediments prograding on a continental shelf; and (3) clinoforms with greater than 150 m (>492 ft) height, which represent shelf-margin clinoforms. Furthermore, clinoforms are grouped into two main progradation directions: (1) clinoforms prograded to the southeast in sequences 2–3, in the Fingerdjupet Subbasin and the western Bjarmeland platform, indicating a source of sediments located in the west-northwestern Barents Sea, and (2) clinoforms prograded to the southwest in sequences 1–6, in the eastern part of the Bjarmeland platform, Nordkapp Basin, and Finnmark platform, indicating a second source of sediments located in the east-northeast. Additionally, in the Hammerfest Basin, clinoforms prograded to the southeast off the Loppa high in sequences 5–6. Low-relief (35–60 m [115–197 ft]), high-gradient, and oblique clinoforms are observed within sequence 2 in the western Bjarmeland platform. The high-gradient foresets are interpreted as potential coarse-grained deposits or as a result of clinoforms prograding to progressive deeper waters, resulting in steeper foresets. Clinoforms located in the eastern part of the study area are interpreted as sourced by a mud-rich system, reflecting a long transportation distance. However, thin, heterolithic patterns in the gamma-ray log possibly reflect thin, sheetlike sands. The height of the clinoforms seems to be a factor controlling the sediment bypass to deep water in the study area. When the height is more than 200 m (656 ft), bottomset deposits are common. This study contributes to a better understanding of the paleogeography and the evolution of the frontier southwestern Barents Sea during the Early Cretaceous and to comprehending the variables increasing the bypass of coarse-grained sediments to deep-water settings.

The extant thermophilic dinoflagellate Tectatodinium pellitum (Al. Tectatodinium rugulatum) from the Danian of Denmark

Tectatodinium rugulatum (Hansen, 1977) McMinn, 1988, from the lower Danian of Denmark, is considered conspecific with, and a junior synonym of, the extant thermophilic species Tectatodinium pellitum Wall, 1967. However, the Danian material, based on holotype and topotype specimens, appears to show a degree of morphologic variability not seen in younger material. The accepted stratigraphic range base of Tectatodinium pellitum is now extended to the lower Danian, where this species appears to be a useful biostratigraphic marker in the Danish North Sea basin.

New Albian to Cenomanian (Cretaceous) dinoflagellate cyst taxa of ovoidinioid affinities from East Greenland, the Barents Sea and England

ABSTRACT Palyno-biostratigraphical studies of upper Albian-Lower Cenomanian successions from East Greenland, the south-western Barents Sea and south-eastern England have revealed new dinoflagellate cyst taxa of clear or questioned ovoidinioid affinities. This paper describes the new genus Sindridinium, four new species – Ovoidinium epelidosphaeroides sp. nov., Epelidosphaeridia manifesta sp. nov., Sindridinium borealis gen. et sp. nov. and Sindridinium anaanae gen. et sp. nov. – and proposes a new combination, Sindridinium? torulosa comb. nov. (formerly Canningia torulosa). The genus Epelidosphaeridia is emended based on features seen in E. manifesta sp. nov., which demonstrate peridiniacean affinities and support inclusion in the Ovoidinioideae. Morphological gradations between Epelidosphaeridia spinosa, E. manifesta sp. nov. and Ovoidinium epelidosphaeroides sp. nov., suggest close phylogenetic relationships, also postulated between Sindridinium? torulosa comb. nov., S. borealis gen. et sp. nov. and S. anaanae gen. et sp. nov. The stratigraphic ranges of the taxa described are calibrated to known dinoflagellate markers and mid-Cretaceous ammonites.