No description available.

The middle Cretaceous (sediments of Albian to Turonian) lithostratigraphy and foraminiferal biostratigraphy of the central North Sea has been described using data from fifteen wells. These wells are located in or on the margins of major Cretaceous depocentres, namely the Witch Ground Graben, Dutch Bank, Moray Firth, 'Buchan' and Forth Approaches Basins. The lithology of cuttings, sidewall core, and conventional core samples have been described and with the help of electric logs a lithostratigraphic subdivision of each well has been achieved. In this area of the North Sea the middle Cretaceous sequences are subdivided into five units, these are the Valhall (part), Rodby, Hidra, Plenus Marl and Herring Formations. As an aid to correlation the Hidra and Herring Formations have been further subdivided on lithologic and electric log character. The microfaunal content of cuttings, sidewall core and conventional core samples from eight wells has been analysed and the taxonomy of the stratigraphically valuable foraminifera is briefly discussed. Seven new species (Bigeneria sp.1. and 2. , Textularia sp.1. and 2., Uvigerinamina sp.1., Gyroidinoides sp.1. and Osangularia sp.1.) and two new varieties, (Gavelinella intermedia (Berthelin) var A and var B) of foraminifera are described. The abundance of planktonic taxa allows the erection of a local zonal scheme comprising five bio-stratigraphic zones. The mid-Cretaceous microfaunas have many elements in common with the well documented assemblages recorded in the equivalent onshore sequences. This allows the ages of the middle Cretaceous formations to be interpreted by correlation of their microfaunas (particularly planktonic foraminifera) with those recovered from onshore sequences in which the standard macrofossil zonations have been identified. Lithostratigraphic and biostratigraphic analysis indicates the presence of a significant non-sequence within the middle Cretaceous sections in the area of the Buchan Field. This is correlated with unconformities in the Moray Firth, the Dutch Bank Basin, the Witch Ground Graben, the Fladen Ground Spur and Forties Field area. The mid-Cretaceous geological history of the central North Sea is described and related to that of the surrounding onshore and offshore areas of North West Europe. An overall transgression during the Albian to latest Cenomanian/early Turonian was followed by a brief regression and associated erosion later in the early Turonian. A further episode of transgression which was initiated later in the Turonian probably continued into the Maastrichtian. This transgressive-regressive-transgressive cycle may be related to eustatic fluctuations in sea level in conjunction with the mild tectonic activity which persisted through mid-Cretaceous times.

No description available.

No description available.

No description available.

No description available.

No description available.

Samples of suspended particulate matter (SPM) and sediment were collected from the Humber coastal zone during six seasonal and inter-annual surveys (November 1993 - July 1995) on board RRS Challenger as part of the NERC Land Ocean Interaction Study (LOIS) initiative. Concentrations of Ni, Zn, Fe and Mn, extracted using a 1M HCl digest, were determined by atomic absorption spectrometry techniques. Particulate Ni and Zn both exhibited a pronounced seasonal distribution in the Humber coastal zone. Significant metal-salinity relationships were obtained for both metals indicating the Humber Estuary to be a significant source of Nip and Znp to the region. Metal distributions in the coastal zone were influenced by residual flow and tidal range at the mouth of the estuary, as well as wind speed and direction. Estimated fluxes of dissolved and particulate Ni and Zn from the Humber mouth to the North Sea indicated significant seasonal variation for both metals (17-290 kg dayˉ¹ Ni; 34-1737 kg dayˉ¹ Zn) and identified transport in the particulate phase dominant in autumn/winter (61-82 % Ni; 68-92 % Zn) but less significant in spring/summer (2-41 % Ni; 15-72 % Zn). Comparison to estuarine inputs suggested retainment of Ni and Zn within the Estuary. In the Humber mouth and throughout the Plume Nip and Znp concentrations significantly correlated to Fep suggesting uptake onto Fe-oxyhydroxide phases was important. Trace metal settling velocities indicated a significant seasonal variation in the settling of Ni (<1-163 µm sˉ¹) and Zn (2-218 µm sˉ¹) with these metals generally settling slower than the average SPM in winter but at the same rate in spring. Particle-solute interactions of Ni and Zn, investigated using the radioisotopes ⁶³Ni and ⁶⁵zn, indicated significant variation in metal partitioning (Kd) for the SPM end-members of the Humber coastal zone with Ni Kd's varying from 6.7 x 10² for Holderness Cliff material, to 13.0 x 10² for estuarine SPM and up to a maximum of 22 x 10² during spring/summer phytoplankton blooms. These results provide the basis of a consistent seasonal data base of trace metal distributions within the Humber coastal Zone which will substantially contribute to the development and parameterization of a fine sediment transport model for trace metal contaminants in coastal zones.

A total of 186 samples taken from 9 offshore Central & Southern North Sea boreholes, 1 onshore XJK borehole, 2 onshore UK localities and 2 onshore Danish localities were processed and analysed for microfauna. A total of 273 individual taxa were identified - the majority to species level. The dominant microfaunal group recorded are the Foraminifera of which 23 genera were agglutinated, 75 calcareous benthonic and 21 planktonic. Other groups recorded are the Ostracoda which comprised 5 genera, Diatomacea 2 and Radiolaria 1. The recorded taxa are diagnosed and their stratigraphic and palaeoenvironmental significance discussed. The samples range in age from Late Cretaceous (Maastrichtian) through Paiaeocene (Danian &amp; Thanetian) to Early Eocene (Ypresian) and occasionally Middle Eocene (Lutetian). The offshore boreholes are biostratigraphically zoned with respect to the published biozonation scheme of King, 1989, and the so-called 'bioevents' (i.e. microfossil marker horizons) described by Mudge &amp; Copestake, 1992. The emphasis of the study was placed on the stratigraphical distribution of the microfaunas, particularly in the offshore realm where the majority of the boreholes (7) are located in the Southern North Sea area (Quadrants 44 and 49); a region lacking in previously published research on microfaunas of this age. The biozonation scheme of King, 1989, is found to be broadly applicable to all of the boreholes studied although some dififerences m detail were noted. Not all of the bioevents of Mudge &amp; Copestake (1992) are recorded. The samples studied are insuflBciently closely spaced to permit the construction here of a separate biozonation scheme, specific to the Southern North Sea area, although it is considered that the future creation of such a scheme could be justified with additional data. A total of 53 individual microfossil marker horizons thought to have stratigraphic utility in the area are noted. The bulk of the Paiaeocene sediments deposited in the Southern North Sea area were laid down under moderate palaeodepths (c. middle shelf) and probably representative of the socalled 'outer sublittoral' biofacies of King, 1983. Evidence for progressive deepening of water depth towards the north of the area and mto the Silver Pit Basin was noted. The microfaunal assemblages from the offshore boreholes are similar in overall character to microfaunas recorded from onshore Palaeogene sections in the UK and Denmark.

Material from the Tertiary of 12 released Shell/Esso exploration wells from the central and southern North Sea basins was studied (739 samples) to elucidate on the distribution and character of calcareous nannofossils in this commercially valuable area. The biostratigraphical distribution of the calcareous nannofossils is outlined, together with brief remarks on the lithology and wireline log responses in each well. Remarks on the distribution of foraminifera were supplied by G. K. Gillmore as part of a parallel study. Comparative material from sites in southern England (London Clay Formation, North London; Thanetian, Pegwell Bay; and Palaeogene of the Isle of Wight), Alabama (Lone Star Cement Quarry, St. Stephen's), New Zealand (William's Bluff near Oamaru, and Hampden Beach), South Atlantic (DSDP 36-329-29-1,36-329- 30-2), Hatton-Rockall Basin (DSDP 12-117-2-3), and Blake Plateau off Florida was also used during the study (70 samples). These localities were selected and analysed for correlation of stratigraphical levels (e. g. Late Oligocene of the Hatton-Rockall Basin), for comparison with low latitude assemblages at certain stratigraphical levels (e. g. Late Eocene of Alabama) or for close examination and scrutiny of species of Reticulofenestra (e. g. Hampden Beach, New Zealand). A brief overview of previous work in this area, the geological history of the North Sea Basin, and the development of oil exploration is given together with sampling strategies and procedures in the introductory chapter. A new method for examining the same specimen in both light and scanning electron microscopes is established which utilises materials and methodology routinely employed in nannopalaeontology, thus enabling the maximum amount of information to be derived from each specimen. Each well is discussed individually in sections relating to blostratigraphically important levels. The lithology, wireline log responses, and foraminiferal data (where available) are used to supplement and complement the calcareous nannofossil data and to build up an outline stratigraphy for each well (see Figs. 22-31). The result of the biostratigraphical study is the proposal of a biozonation scheme for the central and southern North Sea Basins (NS zones 1-23, largely based on the FDO of species) which covers more of the Tertiary, in finer detail, than any of the previously published schemes, and a tentatively proposed joint calcareous nannofossil/foraminifera b1ozonation scheme. The NS (abbreviation for North Sea) biozonation scheme is compared with the established schemes for north-west Europe and with those of supposed wider applicability. Using the scheme as a tool of correlation the extensive formations of the North Sea Basin are compared and contrasted with the restricted and often facies variable outcrops of northwest Europe. The taxonomic section is reduced in the interests of brevity, as the majority of the species encountered are established in the literature, however, a detailed examination of the Family Noelaerhabdaceae, in particular the genus Reticulofenestra, was undertaken and comment made on the taxonomy, structure and evolution of the group. The definition of this genus is emended and a comprehensive compendium of species produced to facilitate cross-referencing of forms.