The late Quaternary climatostratigraphy of IGS Borehole SLN 75/33 and its application to the palaeoceanography of the north-central North Sea

1978 ◽  
Vol 14 (2) ◽  
pp. 147-155 ◽  
Author(s):  
Diane Gregory ◽  
Rex Harland
Keyword(s):  
North Sea ◽  
Late Quaternary ◽  
North Central ◽  
The North ◽  
Central North Sea

A late Quaternary bio- and climatostratigraphy for marine sediments in the north-central part of the North Sea

Boreas ◽  
2008 ◽  
Vol 7 (2) ◽  
pp. 91-96 ◽  
Author(s):  
REX HARLAND ◽  
DIANE M. GREGORY ◽  
MURRAY J. HUGHES ◽  
IAN P. WILKINSON
Keyword(s):  
North Sea ◽  
Marine Sediments ◽  
Late Quaternary ◽  
North Central ◽  
The North ◽  
The North Sea

scholarly journals Looking beyond stratification: a model-based analysis of the biological drivers of oxygen deficiency in the North Sea

2016 ◽  
Vol 13 (8) ◽  
pp. 2511-2535 ◽  
Author(s):  
Fabian Große ◽  
Naomi Greenwood ◽  
Markus Kreus ◽  
Hermann-Josef Lenhart ◽  
Detlev Machoczek ◽  
...  
Keyword(s):  
North Sea ◽  
Oxygen Deficiency ◽  
Low Oxygen ◽  
The North ◽  
Oxygen Conditions ◽  
Southern Central ◽  
The North Sea ◽  
Central North Sea ◽  
The Impact ◽  
Oxygen Dynamics

Abstract. Low oxygen conditions, often referred to as oxygen deficiency, occur regularly in the North Sea, a temperate European shelf sea. Stratification represents a major process regulating the seasonal dynamics of bottom oxygen, yet, lowest oxygen conditions in the North Sea do not occur in the regions of strongest stratification. This suggests that stratification is an important prerequisite for oxygen deficiency, but that the complex interaction between hydrodynamics and the biological processes drives its evolution. In this study we use the ecosystem model HAMSOM-ECOHAM to provide a general characterisation of the different zones of the North Sea with respect to oxygen, and to quantify the impact of the different physical and biological factors driving the oxygen dynamics inside the entire sub-thermocline volume and directly above the bottom. With respect to oxygen dynamics, the North Sea can be subdivided into three different zones: (1) a highly productive, non-stratified coastal zone, (2) a productive, seasonally stratified zone with a small sub-thermocline volume, and (3) a productive, seasonally stratified zone with a large sub-thermocline volume. Type 2 reveals the highest susceptibility to oxygen deficiency due to sufficiently long stratification periods (>  60 days) accompanied by high surface productivity resulting in high biological consumption, and a small sub-thermocline volume implying both a small initial oxygen inventory and a strong influence of the biological consumption on the oxygen concentration. Year-to-year variations in the oxygen conditions are caused by variations in primary production, while spatial differences can be attributed to differences in stratification and water depth. The large sub-thermocline volume dominates the oxygen dynamics in the northern central and northern North Sea and makes this region insusceptible to oxygen deficiency. In the southern North Sea the strong tidal mixing inhibits the development of seasonal stratification which protects this area from the evolution of low oxygen conditions. In contrast, the southern central North Sea is highly susceptible to low oxygen conditions (type 2). We furthermore show that benthic diagenetic processes represent the main oxygen consumers in the bottom layer, consistently accounting for more than 50 % of the overall consumption. Thus, primary production followed by remineralisation of organic matter under stratified conditions constitutes the main driver for the evolution of oxygen deficiency in the southern central North Sea. By providing these valuable insights, we show that ecosystem models can be a useful tool for the interpretation of observations and the estimation of the impact of anthropogenic drivers on the North Sea oxygen conditions.

Jurassic and Cretaceous clays of the northern and central North Sea hydrocarbon reservoirs reviewed

Clay Minerals ◽  
2006 ◽  
Vol 41 (1) ◽  
pp. 151-186 ◽  
Author(s):  
M. Wilkinson ◽  
R. S. Haszeldine ◽  
A. E. Fallick
Keyword(s):  
Oxygen Isotope ◽  
North Sea ◽  
Meteoric Water ◽  
Threshold Temperature ◽  
Common Belief ◽  
The North ◽  
Wide Range ◽  
The North Sea ◽  
Uplift And Erosion ◽  
Central North Sea

AbstractThe principal clays of the northern and central North Sea are illite (sometimes with interlayered smectite) and kaolin. Chlorite is only locally important. Although it has been proposed that kaolin within North Sea sandstones is detrital in origin, the majority of workers have concluded that it is authigenic, largely the product of feldspar alteration. Kaolin is found within a wide range of sedimentary settings (and within shales) apparently defying the notion that kaolin is an indicator of meteoric water deposition. Within sandstones, the earliest authigenic kaolin has a vermiform morphology, the distribution of which is controlled by the availability of detrital mica to act as a nucleus, and the composition of the post-depositional porewaters. This vermiform kaolin formed in meteoric water, the presence of which is easily accounted for below sub-aerial exposure surfaces in non-marine formations, and below unconformities over marine units. In fully marine sands, and even marine shale units, kaolin still occurs. It has therefore been suggested that even these locations have been flushed with meteoric water.Early vermiform kaolin recrystallizes to a more blocky morphology as burial proceeds, at least in the Brent Group. Blocky kaolin has been reported as growing before, synchronously with, and after the formation of quartz overgrowths, though oxygen isotope studies support low-temperature growth, pre-quartz. Blocky kaolin may form during meteoric flushing associated with lower Cretaceous uplift and erosion, though it is found in fault blocks that are thought to have remained below sea level. Here, the kaolin may form in stagnant meteoric water, relics of the post-depositional porewater. It has also been proposed that the blocky kaolin grew in ascending basinal waters charged with carboxylic acids and CO2, though this hypothesis is not supported by stable oxygen isotope data. Some of the blocky kaolin is dickite, the stable polymorph above ∼100°C.Fibrous illite occurs almost ubiquitously within the clastic sediments of the North Sea. An early pore-lining phase has been interpreted as both infiltrated clastic clay, and as an early diagenetic phase. Early clays may have been quite smectite-rich illites, or even discrete smectites. Later, fibrous illite is undoubtedly neoformed, and can degrade reservoir quality significantly. Both within sandstones and shales, there is an apparent increase in the K content deeper than 4 km of burial, which could be due to dilution of the early smectite-rich phase by new growth illite, or to the progressive illitization of existing I-S. Much of the ‘illite’ that has been dated by the K-Ar method may therefore actually be I-S.The factors that control the formation of fibrous illite are only poorly known, though temperature must play a role. Illite growth has been proposed for almost the entire range of diagenetic temperatures (e.g. 15–20°C, Brent Group; 35–40°C, Oxfordian Sand, Inner Moray Firth; 50–90°C, Brae formation; 100–110°C, Brent Group; 130–140°C, Haltenbanken). It seems unlikely that there is a threshold temperature below which illite growth is impossible (or too slow to be significant), though this is a recurring hypothesis in the literature. Instead, illite growth seems to be an event, commonly triggered by oil emplacement or another change in the physiochemical conditions within the sandstone, such as an episode of overpressure release. Hence fibrous illite can grow at any temperature encountered during diagenesis.Although there is an extensive dataset of K-Ar ages of authigenic illites from the Jurassic of the North Sea, there is no consensus as to whether the data are meaningful, or whether the purified illite samples prepared for analysis are so contaminated with detrital phases as to render the age data meaningless. At present it is unclear about how to resolve this problem, though there is some indication that chemical micro-analysis could help. It is a common belief that illite ages record the timing of oil charge, and so can be used to calibrate basin models.Grain-coating Fe-rich chlorite cements can preserve exceptional porosity during burial. They are found in marginal marine sandstones, formed during diagenesis from precursor Fe-rich clays such as berthierine or verdine.

Late Quaternary palaeontology, sedimentology and geochemistry of a vibrocore from the Witch Ground Basin, central North Sea

1986 ◽  
Vol 73 (1-2) ◽  
pp. 109-123 ◽  
Author(s):  
D. Long ◽  
A. Bent ◽  
R. Harland ◽  
D.M. Gregory ◽  
D.K. Graham ◽  
...  
Keyword(s):  
North Sea ◽  
Late Quaternary ◽  
The Witch ◽  
Central North Sea

Spatial and temporal dynamics of European hake (Merluccius merluccius) in the North Sea

2018 ◽  
Vol 75 (6) ◽  
pp. 2033-2044 ◽  
Author(s):  
Arved Staby ◽  
Jon Egil Skjæraasen ◽  
Audrey J Geffen ◽  
Daniel Howell
Keyword(s):  
North Sea ◽  
Temporal Dynamics ◽  
Trawl Survey ◽  
Merluccius Merluccius ◽  
Frequency Distributions ◽  
The North ◽  
The North Sea ◽  
Northern North Sea ◽  
Central North Sea ◽  
European Hake

Abstract Catches of European hake (Merluccius merluccius) in the North Sea have increased substantially during the last decade, even though there is no directed commercial fishery of hake in this area. We analysed the spatial distributions of hake in the northern the parts of its range, (where it is less well-studied), using ICES international bottom trawl survey data from 1997 to 2015. We examine length-frequency distributions for (i) distinct modes enabling the assignment of fish into categories which likely corresponded to the ages 1, 2, and 3+ and (ii) patterns of seasonal spatial distribution for the different groups. Age categories 1 and 2 fish were most abundant in the northern North Sea, and appear to remain in the North Sea until 2 years of age, when they move into deeper waters. Their distribution has expanded into the western-central North Sea in the last decade. Age category 3+ fish were most abundant in the northern and central North Sea during summer, indicating a seasonal influx of large individuals into this area likely associated with spawning activity. The distribution of these older fish has gradually expanded westward in both seasons.

scholarly journals Redeposited chalk hydrocarbon reservoirs of the North Sea caused by the Chicxulub K-T bolide impact

2003 ◽  
Vol 82 (4) ◽  
pp. 333-337
Author(s):  
M. Rider ◽  
D. Kroon
Keyword(s):  
North Sea ◽  
Secondary Effects ◽  
Sea Floor ◽  
Hydrocarbon Reservoir ◽  
The North ◽  
The North Sea ◽  
Physical Effects ◽  
Central North Sea ◽  
The Impact ◽  
Oil Company

AbstractA widespread, slumped, redeposited, uppermost Cretaceous chalk interval, up to 60m thick, immediately below the Cretaceous-Tertiary (K-T) boundary, recognised in oil company boreholes across the central North Sea and a major hydrocarbon reservoir, we re-interpret as the result of a single, catastrophic event caused by secondary effects related to the bolide impact at Chicxulub. A thin, dark clay bed immediately above the redeposited chalks, we suggest correlates to the outcropping, Iridium rich, Danish ‘Fish Clay’, rapidly deposited after the impact. Physical effects on sea-floor sediments, caused by the K-T bolide impact, have not previously been interpreted in the North Sea.

Mechanisms of late Quaternary fault throw-rate variability along the north central Gulf of Mexico coast: implications for coastal subsidence

2016 ◽  
Vol 29 (5) ◽  
pp. 557-570 ◽  
Author(s):  
Zhixiong Shen ◽  
Nancye H. Dawers ◽  
Torbjörn E. Törnqvist ◽  
Nicole M. Gasparini ◽  
Marc P. Hijma ◽  
...  
Keyword(s):  
Gulf Of Mexico ◽  
Late Quaternary ◽  
North Central ◽  
The North ◽  
Mexico Coast

scholarly journals Pyritized diatoms: a good fossil marker in the Upper Paleocene-Lower Eocene sediments from the Belgian and Dieppe-Hampshire Basins

2004 ◽  
Vol 83 (3) ◽  
pp. 173-178 ◽  
Author(s):  
Y. Van Eetvelde ◽  
C. Dupuis ◽  
C. Cornet
Keyword(s):  
North Sea ◽  
Strong Increase ◽  
Lower Eocene ◽  
The North ◽  
Carbon Isotope Excursion ◽  
Lithostratigraphic Units ◽  
Abundance Peak ◽  
The North Sea ◽  
Central North Sea ◽  
Upper Paleocene

AbstractAssemblages of brackish and marine diatoms have been examined from Upper Paleocene-Lower Eocene strata of the Belgian Basin (Knokke well) and the Dieppe-Hampshire Basin (Saint-Josse borehole and Ailly sections). The diatoms observed are invariably preserved in pyrite as internal moulds and their siliceous skeletons are completely replaced by pyrite by epigenesis. Three major diatom assemblages have been observed which can be used to approximate the position of the recently defined Paleocene-Eocene boundary (defined by the Carbon Isotope Excursion). This isotope excursion occurs just below the strong increase in the abundance of Fenestrella antiqua and in the vicinity of the abundance peak of Coscinodiscus morsianus var. moelleri. They also allow correlations of the lithostratigraphic units of the Belgian Basin with the formations of the Dieppe-Hampshire and central North Sea Basins. For instance, investigations of diatoms recorded in the Knokke Clay Member of the Knokke well indicate that this unit corresponds to the lower units of the ‘Sparnacian facies’ of the Dieppe-Hampshire Basin and to the Sele Formation of the North Sea Basin.

scholarly journals A sporomorph ecogroup model for the Northwest European Jurassic - Lower Cretaceous II : Application to an exploration well from the Dutch North Sea

2004 ◽  
Vol 83 (2) ◽  
pp. 81-91 ◽  
Author(s):  
O.A. Abbink ◽  
J.H.A. Van Konijnenburg-Van Cittert ◽  
C.J. Van der Zwan ◽  
H. Visscher
Keyword(s):  
Sea Level ◽  
North Sea ◽  
Distribution Patterns ◽  
Humid Climate ◽  
Depositional Sequence ◽  
Sea Level Fluctuations ◽  
The North ◽  
Reservoir Models ◽  
The North Sea ◽  
Central North Sea

AbstractJurassic shallow marine to non-marine depositional sequences are among the most important economic targets in the North Sea. Detailed, ‘high resolution’ stratigraphy of these sequences has become a necessity in both predictive geological exploration models as well as in production reservoir models. In these paralic sequences, palynomorphs are the most abundant (micro) fossil group. Palynology is increasingly challenged to improve the biostratigraphic control, and to support the sequence stratigraphical framework. Based on a recently developed, conceptual Sporomorph EcoGroup model, the quantitative distribution patterns of terrestrial palynomorphs are grouped in six Sporomorph EcoGroups (SEGs), viz. Upland, Lowland, River, Pioneer, Coastal, and Tidally-influenced SEG. Application of the SEG model to data from a marginal marine, uppermost Callovian - Middle Oxfordian section of NAM well F17-4 from the southern part of the Central North Sea Graben allows the recognition of sea-level fluctuations and climate changes. A marked palaeoclimatic shift occurred in the earliest Middle Oxfordian. The relatively cool-subtropical, humid climate changed into a warmer, subtropical-tropical, drier climate. The sea-level reconstructions based on the SEG model are validated against a latest Callovian - Earliest Oxfordian depositional sequence.

scholarly journals SELECTIVE OIL SPILL COMBAT PLANNING FOR OFFSHORE EXPLORATION AND PRODUCTION OPERATIONS IN THE NORTH SEA

1979 ◽  
Vol 1979 (1) ◽  
pp. 641-647
Author(s):  
Johannes Ph. Poley
Keyword(s):  
North Sea ◽  
Contingency Planning ◽  
Coastal Protection ◽  
Oil Composition ◽  
Arrival Times ◽  
The North ◽  
Exploration And Production ◽  
The North Sea ◽  
Central North Sea ◽  
Sea Area

ABSTRACT Experience shows that during emergencies (Ekofisk, Amoco Cadiz) considerable differences of opinion can arise concerning the best combat-action to be taken, in spite of existing approved contingency plans. In this paper, a case is made for an improvement of the decision-making during emergencies through selective contingency planning for offshore operations. In such selective contingency planning, a spill from a specific (potential) source and its impact on a stretch of coastline are being interconnected and analysed. This will involve consideration of source-specific data (such as location, oil-composition, flow-rates, and temperatures), together with such items as estimates of the fate and movement of that oil across the intermediate stretch of sea, seasonal conditions, pollution risks in terms of oil arrival times and amounts, and coastal vulnerability In consultation between government and industry, a scenario for action tailored to that situation then can be decided in advance, both for combat at the spill location and for coastal protection. The paper is illustrated with evidence from the Ekofisk blow-out case, and with the estimated pollution hazard for the Dutch Wad-denzee from an oil blow-out in the central North Sea area.

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