David S. Wray

Marine biodiversity through the Late Cenomanian–Early Turonian: palaeoceanographic controls and sequence stratigraphic biases

Changes in the marine macro- and microfauna, sedimentary geochemistry and surface-water palaeoproductivity through the last 500 000 years of the Cenomanian and first 300 000 years of the Turonian are documented. These are based on the succession at Eastbourne, the thickest and most complete section through the Late Cenomanian and Early Turonian in the Anglo–Paris Basin. Two levels of rapid faunal and geochemical change are identified, one coincident with a significant increase in siliciclastic input at the base of the Plenus Marls Member, and the other with a marked drop in surface water productivity near the top of the same unit. Faunal change is demonstrated to be largely a pattern of immigration–emigration rather than true extinction, and our sequence stratigraphical analysis shows that it was coincident with major sea-level changes. No evidence is found to support the hypothesis that reduced bottom water oxygenation developed and was responsible for extinctions amongst the benthos in mid-shelf environments. The onset of pure chalk facies is interpreted to mark the breakdown of shelf-break fronts and the spread of oligotrophic oceanic waters over much of the continental shelf, initiated by rising sea-level. The Cenomanian–Turonian event, far from recording a mass extinction of shelf fauna, is most probably an artifact caused by a significant switch in the nature of the surviving sedimentary record as a result of a major, but perfectly ordinary, oceanographic change.

Orbital tuning of Cenomanian marly chalk successions: towards a Milankovitch time-scale for the Late Cretaceous

Outcrops of Cenomanian marly chalks in the Crimea (Ukraine) and SE England (UK), 2600 km apart, display conspicuous decimetre–scale rhythmicity and can be correlated by using 12 biostratigraphical events. Closely spaced samples from the two sections were used to generate long time–series of digitally captured grey–scale reflectance data. Spectral analysis of these data demonstrates that if the rhythmicity is assumed to be driven by precession (bedding cycles; mode at 20 ka), it is seen to be modulated by the short eccentricity cycle (100 ka bundles). The latter signal is expressed in the sediments by the occurrence of dark marls at precession minima occurring at eccentricity maxima. Although identified in the spectra, tilt (38 ka) and the long eccentricity cycle (400 ka) are not strongly expressed. Comparison of age modelled, unfiltered grey–scale data between the two sections reveals strikingly similar patterns, and enables the identification of a 80 ka hiatus in the UK chalks.

IDENTIFICATION AND LONG-RANGE CORRELATION OF BENTONITES IN TURONIAN-CONIACIAN (UPPER CRETACEOUS) CHALKS OF NORTHWEST EUROPE

A geochemical and mineralogical study of thin (2–20 cm) clay-rich beds found in Turonian–Coniacian chalks from the Anglo-Paris Basin has been undertaken. On the basis of their rare-earth element (REE) and mineralogical composition it is possible to subdivide beds into bentonites, characterized by a negative Eu anomaly and elevated smectite content, and detrital beds (characterized by a minimal or absent Eu anomaly and a greater proportion of illite). Six beds are considered to be bentonites (Glynde 1, Southerham 1, Caburn, Bridgewick 1, Lewes and Shoreham 2). Trace-element discriminant diagrams add support, as does comparison with similar studies undertaken in eastern England and northern Germany. Geochemical evidence demonstrates that the tephra was variably acidic in composition (rhyodacite–rhyolite–comendite/pantellerite), and was probably derived from crustal melting associated with initial rifting of the North Atlantic. Correlation of bentonites between the Anglo-Paris Basin, eastern England and northern Germany can be demonstrated and independently tested, establishing a tephro-event stratigraphy across northwest Europe for this period.

Volcanogenic clays in Jurassic and Cretaceous strata of England and the North Sea basin

Abstract The nature and origin of authigenic clay minerals and silicate cements in the Jurassic and Cretaceous sediments of England and the North Sea are discussed in relation to penecontemporaneous volcanism in and around the North Sea Basin. Evidence, including new REE data, suggests that the authigenic clay minerals represent the argillization of volcanic ash under varying diagenetic conditions, and that volcanic ash is a likely source for at least the early silicate cements in many sandstones. The nature and origin of smectite-rich, glauconite-rich, berthierine-rich and kaolin-rich volcanogenic clay mineral deposits are discussed. Two patterns of volcanogenic clay minerals facies are described. Pattern A is related to ash argillization in the non-marine and marine environments. Pattern B is developed by the argillization of ash concentrated in the sand and silt facies belts in the seas bordering ash-covered islands and massifs. It is associated with regression/ transgression cycles which may be related to thermal doming and associated volcanism, including the submarine release of hydrothermal fluids rich in Fe. The apparent paucity of volcanogenic clay deposits in the Jurasssic and Early Cretaceous sediments of the North Sea is discussed.

The impact of unconfined mine tailings and anthropogenic pollution on a semi-arid environment – an initial study of the Rodalquilar mining district, south east Spain

A geochemical study of stream sediments near Rodalquilar (South-east Spain) was undertaken to investigate the impact of processing activities associated with nearby gold mining. Despite the semi-arid nature of the area, visual inspection of tailings indicates that considerable fluvial erosion occurs during rainfall events. Geochemical analysis demonstrates that Mo, Sb, Te, Bi and As are all found at elevated levels in stream sediments downstream of the tailings site. Elevated levels of Pb, Cu and Zn were also noted in stream sediments. Statistical analysis demonstrates that four factors control trace-element distribution. Factor 1 displays a strong association of Mo, Sb, Te and Bi and As and is attributed to the mine tailings. Factor 2 displays an association of Pb and Cu, and is most easily attributed to anthropogenic pollution. Factor 3 distinguishes Au and reflects the selective nature of ore-processing methods employed at the site. Factor 4 only highlights Zn, reflecting that it is derived from several, probably unrelated, sources.

A baseline survey of the distribution and origin of platinum group elements in contemporary fluvial sediments of the Kentish Stour, England

The extensive anthropogenic use of the platinum group elements (PGE: Ru, Rh, Pd, Os, Ir and Pt) is the main factor responsible for the widespread dispersion of these elements throughout the environment. Significant quantities of the PGE enter fluvial systems via road runoff, storm drains and wastewater and sewage treatment systems, and may accumulate in fluvial sediments by physical and chemical processes. A baseline survey of contemporary fluvial sediments in the Kentish Stour river, east Kent, England, has been undertaken to document the sources and distribution of anthropogenic PGE in an attempt to constrain some of the physical and chemical parameters that may influence the distribution of these elements. The geology of the catchment of the Kentish Stour is dominated by carbonate and silicate sedimentary rocks, and the river passes through urban and rural land and receives inputs of waste from sewage works. Nine sedimentary rocks, 4 motorway-runoff sediments and 22 river sediments were analysed for PGE by NiS fire assay preconcentration and ICP–MS. The highest element abundances occur in the motorway-runoff sediments (maximum total PGE content of 55 ng/g), whilst the lowest values were recorded in the sedimentary rocks, where some samples contain PGE at concentrations below the limit of detection. The total PGE content of the river sediments ranged from 0.4 to 10.8 ng/g. The distribution and variation in concentrations and ratios of the PGE in the contemporary fluvial sediments of the Kentish Stour correspond strongly with land-use changes (urban versus rural) and with points of discharge from sewage works. The absence of a pure catalytic converter signature in the river sediments, however, indicates that source signatures may be mixed in sewage works or that PGE may chemically fractionate in the fluvial environment.

Heavy-metal concentration in the frog Rana ridibunda from a small river of Macedonia, Northern Greece

The concentration of 14 heavy metals in the tissues of the frog Rana ridibunda, living in a small river of Macedonia, Northern Greece. was investigated. The liver contained significantly higher amounts of copper (1041±153 mg/kg dry wt), cobalt (6±0.1 mg/kg), molybdenum (22±7 mg/kg), chromium (41±11 mg/kg), and cadmium (2±0.2 mg/kg), while the carcass contained significantly higher amounts of aluminum (303±67 mg/kg), manganese (164±38 mg/kg), nickel (27±3 mg/kg), strontium (419±34 mg/kg), and barium (93.1±1 mg/kg). High concentrations of copper, chromium, molybdenum, zinc, manganese, and aluminum, corresponding to the highly polluted areas, were detected. For some other metals, such as cobalt, nickel, lead, cadmium, and cesium, the river could be classified as moderately to heavily polluted. The main sources of the river pollution seem to be fertilizers containing heavy metals as trace elements, pesticides with a heavy metal in their formula, urban runoff, and various light industries along the river that discharge their effluents into this river. It seems likely that the Central Macedonia area shares common sources of pollution for a number of heavy metals.

Origin of clay-rich beds in Turonian chalks from Lower Saxony, Germany — A rare-earth element study

Abstract The mineralogy and REE geochemistry of thin, clay-rich beds from Turonian chalks of Lower Saxony (Germany) has been studied. Two types of clay-rich beds are present. The first is of volcanic origin and is characterised by: (1) a REE signature similar to marine argillized volcanic ash bands; and (2) a silicate mineralogy dominated by smectite with minor corrensite. The second type is of continental origin and is characterised by: (1) a REE signature similar to continental shale; and (2) a silicate mineralogy dominated by smectite with minor heulandite-clinoptilolite. The use and misuse of these widespread clay-rich horizons in the Turonian stratigraphy of Lower Saxony is discussed.

Essential and trace elements content of commercial infant foods in the UK.

There is a paucity of data in respect of the nutritional quality of complementary foods for infants and young children aged between 6 and 12months. The primary objective of this study was to examine nutritive values of such complementary infant food on the UK market in order to ascertain their suitability relative to dietary guidelines for the 6-9months age group. Quantitative analyses were conducted on eight different products representing four popular brands (meat and vegetable based) currently on sale in the UK. Eight major mineral and trace elements, namely: calcium, copper, magnesium, iron, zinc, potassium, sodium and selenium were measured by ICP-OES and ICP-MS. The results of these studies were referenced to the Recommended Nutrient Intake (RNI) values for 6-9months old children, and a menu of entire daily intake of minerals and trace elements was composed taking into consideration the nutrient and energy intake from milk consumption. Based on these comparisons, all the food samples studied in this work contained less essential minerals than expected from the RNI values except for potassium in meat and vegetable based recipes. These results suggest that commercial complementary infant foods on the UK market may not contain the minimum levels of minerals required for the labelling declaration of micronutrient content (Commission Directive 2006/125/EC). This provides opportunities and scope for product optimisation to improve their nutritive value.

An example of alternative correlation techniques in a low-accommodation setting, nonmarine hydrocarbon system: The (Lower Cretaceous) Mannville Basal Quartz succession of southern Alberta

Chemostratigraphy and heavy-mineral techniques have been applied to the Lower Cretaceous Basal Quartz in the Western Canada sedimentary basin. The aim of the study is to demonstrate that these two techniques can be used to help understand the complex stratigraphy of reservoirs deposited in low-accommodation fluvial settings. The Basal Quartz is an ideal unit to demonstrate their applicability in stratigraphic studies of hydrocarbon reservoirs because extensive mapping and petrographic studies have enabled the establishment of a rigorous stratigraphic framework despite its complexity resulting from deposition in a low-accommodation fluvial setting. The three component units analyzed in the Basal Quartz (Horsefly unit, Bantry–Alderson–Taber [BAT] unit, and Ellerslie unit) each have unique geochemical and heavy-mineral characteristics. Chemostratigraphic analysis shows that silty claystones from the Horsefly, BAT, and Ellerslie units have distinctly different geochemistry from one another, with the variations being caused by changes in clay mineralogy and other components, such as feldspar, apatite, and zircon. The geochemistry also suggests periodic volcanogenic input influenced the silty claystones of the Basal Quartz. Heavy-mineral analysis shows that sandstones from the three units can be distinguished on the basis of ratio parameters, such as apatite/tourmaline, rutile/zircon, and zircon/tourmaline, which are controlled by differences in provenance and intensity of weathering during transport.