scholarly journals Pseudo-nitzschia sp. diversity and seasonality in the southern North Sea, domoic acid levels and associated phytoplankton communities

2018 ◽  
Vol 214 ◽  
pp. 194-206 ◽  
Author(s):  
A. Delegrange ◽  
A. Lefebvre ◽  
F. Gohin ◽  
L. Courcot ◽  
D. Vincent
Keyword(s):  
North Sea ◽  
Domoic Acid ◽  
Southern North Sea ◽  
Phytoplankton Communities

Detrital zircon geochronology and heavy mineral analysis as complementary provenance tools in the presence of extensive weathering, reworking and recycling: the Neogene of the southern North Sea Basin

2021 ◽  
pp. 1-13
Author(s):  
Jasper Verhaegen ◽  
Hilmar von Eynatten ◽  
István Dunkl ◽  
Gert Jan Weltje
Keyword(s):  
North Sea ◽  
Chemical Weathering ◽  
Heavy Mineral ◽  
Mineral Analysis ◽  
Provenance Analysis ◽  
Detrital Zircon Geochronology ◽  
Southern North Sea ◽  
Variable Heavy ◽  
Mineral Data ◽  
Heavy Mineral Analysis

Abstract Heavy mineral analysis is a long-standing and valuable tool for sedimentary provenance analysis. Many studies have indicated that heavy mineral data can also be significantly affected by hydraulic sorting, weathering and reworking or recycling, leading to incomplete or erroneous provenance interpretations if they are used in isolation. By combining zircon U–Pb geochronology with heavy mineral data for the southern North Sea Basin, this study shows that the classic model of sediment mixing between a northern and a southern source throughout the Neogene is more complex. In contrast to the strongly variable heavy mineral composition, the zircon U–Pb age spectra are mostly constant for the studied samples. This provides a strong indication that most zircons had an initial similar northern source, yet the sediment has undergone intense chemical weathering on top of the Brabant Massif and Ardennes in the south. This weathered sediment was later recycled into the southern North Sea Basin through local rivers and the Meuse, leading to a weathered southern heavy mineral signature and a fresh northern heavy mineral signature, yet exhibiting a constant zircon U–Pb age signature. Thus, this study highlights the necessity of combining multiple provenance proxies to correctly account for weathering, reworking and recycling.

scholarly journals Macrofauna as a major driver of bentho‐pelagic exchange in the southern North Sea

2021 ◽  
Author(s):  
Andreas Neumann ◽  
Justus E. E. Beusekom ◽  
Annika Eisele ◽  
Kay‐Christian Emeis ◽  
Jana Friedrich ◽  
...  
Keyword(s):  
North Sea ◽  
Southern North Sea

Radiogenic and stable isotope evidence for age and origin of authigenic illites in the Rotliegend, southern North Sea

Clay Minerals ◽  
1994 ◽  
Vol 29 (4) ◽  
pp. 555-565 ◽  
Author(s):  
K. Ziegler ◽  
B. W. Sellwood ◽  
A. E. Fallick
Keyword(s):  
North Sea ◽  
Structural Evolution ◽  
Lower Permian ◽  
Gas Reservoirs ◽  
Gaseous Hydrocarbon ◽  
Oxygen Isotope Exchange ◽  
Basin Inversion ◽  
Southern North Sea ◽  
Evaporative Concentration ◽  
Isotopic Analyses

AbstractAeolian sandstones of the Lower Permian Leman Formation (Rotliegend Group) provide the best gas reservoir in the southern North Sea, but permeability is greatly reduced by the presence of authigenic fibrous illites. New radiogenic (K/Ar) and stable (oxygen and hydrogen) isotope data are presented for fibrous illite cements (<0.1 µm), so that the absolute timing and controlling diagenetic factors for their formation can be more fully evaluated. Thus, the expected quality of gas reservoirs in the southern North Sea might be better predicted. Samples have been analysed from five wells in areas with contrasting structural evolution: the Sole Pit Basin, and the Indefatigable Shelf. The K/Ar ages of between 160 and 190 Ma have been obtained from the Indefatigable Shelf illites, and between 120 and 160 Ma for those from the Sole Pit Basin, reflecting different times of basin inversion. These K/Ar ages are interpreted by reference to burial/thermal models for each well. The temperature of illite precipitation falls between 88 and 140°C. Calculated pore-fluid compositions derived from oxygen and hydrogen isotopic analyses give values of ∼ + 1 to +9‰ (SMOW) δ18O and +1 to −50‰ (SMOW) δD. The illite δD values have probably been affected by isotopic exchange and fractionation with the surrounding gaseous hydrocarbon. The δ18O values reflect the degree to which evaporative concentration had affected Zechstein marine waters which subsequently invaded the Leman Sandstone. Comparisons between δ18O and δD values in clays and in formation water for the Leman Field suggest that oxygen isotope exchange might have taken place, and that the initial K+ and radiogenic 40Ar contents within illites may have been modified.

scholarly journals The Size of Diatoms II. Further Observations on Rhizosolenia styliformis (Brightwell)

1946 ◽  
Vol 26 (3) ◽  
pp. 271-284 ◽  
Author(s):  
R. S. Wimpenny
Keyword(s):  
North Sea ◽  
Indicator Species ◽  
Separate Species ◽  
Southern North Sea ◽  
Auxospore Formation ◽  
The North ◽  
The North Sea ◽  
Set Up ◽  
The Antarctic

1. Diameter measurements of Rhizosolenia styliformis from the Antarctic, the subtropical Atlantic and Pacific Oceans and from the North Sea and neighbouring waters have made it appear necessary to set up two varieties, oceanica and semispina, in addition to the type of the species R. styliformis. The type as I describe it has been called var. longispina by Hustedt, but elsewhere it has often been figured as the var. oceanica of this paper. Var. semispina is synonymous with the form represented by Karsten as R. semispina Hensen. It differs from R. semispina as drawn by Hensen and its synonym R. hebetata forma semispina Gran, but is thought likely to be linked by intermediates. If this is so R. hebetata may have to be extended to include and suppress R. styliformis, as var. semispina is linked to the type by intermediates. Var. oceanica has no intermediate forms and, if R. hebetata is to be extended, this variety should be established as a separate species.2. Var. oceanica is absent from the southern North Sea and appears to be an indicator species related to oceanic inflow.3. Auxospore formation was observed for the type in the southern North Sea in 1935 and biometric observations suggest that a period of 3-4 years elapsed between the production of auxospore generations in that area. Outside the southern North Sea for the type, measurements give no indication of auxospore generations occurring at intervals exceeding a year. While auxospore formation has been seen in var. oceanica from the Shetlands area samples of June 1935 and July 1938, this phenomenon has not been observed for var. semispina.

scholarly journals Modeling mixoplankton along the biogeochemical gradient of the Southern North Sea

2021 ◽  
Vol 459 ◽  
pp. 109690
Author(s):  
Lisa K. Schneider ◽  
Nathalie Gypens ◽  
Tineke A. Troost ◽  
Willem Stolte
Keyword(s):  
North Sea ◽  
Southern North Sea
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