Kevin G. Taylor

Geochemical and mineral magnetic characterisation of urban sediment particulates, Manchester, UK

Urban sediments are part of a complex system in which particulates accumulate potentially toxic pollutants, ultimately posing a threat to urban water-bodies and public health. It is therefore important to recognise sources, signatures and pathways of urban particulates. Urban sediment samples were analysed from both inner and outer city road surfaces of Manchester, UK. High metal concentrations, coupled with the largely ferrimagnetic multi-domain (MD) mineral magnetic composition of the particulates, indicate inputs of anthropogenic origin, primarily particulates derived from automobiles, as being the dominant source to the urban sediment system. Iron and Pb concentrations show a clear spatial trend, whereby concentrations are enhanced in the inner city samples. Lead concentrations for inner and outer city samples average 354 and 185 μg g−1, respectively. Iron concentrations for inner and outer city samples average 11302 and 6486 μg g−1, respectively. Sequential extraction analysis shows the metals Mn, Fe, Zn and Pb are largely associated with the reducible fraction, whereas Cu is largely associated with the oxidisable fraction. Zinc is the only metal showing significant association with the exchangeable fraction (up to 33%), suggesting that it may be the most susceptible metal to mobilisation during runoff. Metal fractions identified as showing larger associations with the reducible and oxidisable fractions will continue to be vulnerable to mobilisation as a result of changes in ambient pH and/or redox conditions. Mineral magnetic concentration parameters, such as the saturation isothermal remanent magnetisation (SIRM), together with hysteresis parameters such as the coercive force and interparametric ratios (such as (Bo)cr/Hc and IRM-100mT/SIRM) show that ferrimagnetic MD minerals dominate the Manchester urban sediments. Average results for frequency-dependent susceptibility as a percentage (2%) suggest that the composition of these Manchester sediments is not dominated by soil-derived material, and therefore magnetically coarser, anthropogenically-derived material is dominant. Unlike Pb and Fe concentrations, mineral magnetic characteristics of the Manchester urban sediment samples exhibit no significant spatial variation.

Trace Metals as Biomarkers for Eumelanin Pigment in the Fossil Record

X-ray maps of fossil feather pigments reveal color patterning in extinct bird species. Well-preserved fossils of pivotal early bird and nonavian theropod species have provided unequivocal evidence for feathers and/or downlike integuments. Recent studies have reconstructed color on the basis of melanosome structure; however, the chemistry of these proposed melanosomes has remained unknown. We applied synchrotron x-ray techniques to several fossil and extant organisms, including Confuciusornis sanctus, in order to map and characterize possible chemical residues of melanin pigments. Results show that trace metals, such as copper, are present in fossils as organometallic compounds most likely derived from original eumelanin. The distribution of these compounds provides a long-lived biomarker of melanin presence and density within a range of fossilized organisms. Metal zoning patterns may be preserved long after melanosome structures have been destroyed.

Stability and facies association of early diagenetic mineral assemblages; an example from a Jurassic ironstone-mudstone succession, U.K.

ABSTRACT Sedimentological and petrographic data from two Lower Liassic ooidal ironstones (the Frodingham and Pecten Ironstones) and associated mudstones from eastern England have been collected. Within these ironstones early diagenetic berthierine, siderite, and minor glauconite have a limited lateral extent, associated with an intrabasinal high (the Market Weighton Swell). This mineral assemblage passes laterally and vertically into mudstones and silty mudstones within which pyrite is the dominant early diagenetic iron mineral. The ironstones are stratigraphically condensed, having experienced low net sediment accumulation rates and shallow, high-energy conditions. Thermodynamic considerations indicate that berthierine and siderite should be stable in anoxic environments where sulfide activity is negligible. Pyrite is rare within the ironstones, suggesting that sulfate reduction was a negligible process during ironstone formation. Where pyrite is present it postdates berthierine and siderite, indicating that sulfate reduction may have been a later process in some beds. We propose that berthierine and siderite were precipitated during suboxic diagenesis, where sulfate reduction was inhibited and iron reduction was the dominant process of organic-matter oxidation. Suboxic diagenesis resulted from the extended periods of physical and biological sediment reworking during ironstone deposition, which favored the oxidation of iron minerals and aerobic egradation and loss of organic matter. Berthierine formed during early suboxic diagenesis at the expense of detrital clays and iron oxides. During later suboxic diagenesis, pore-water bicarbonate activities increased, leading to siderite precipitation. Early glauconite also formed in places, and it seems likely that it formed close to the oxic/suboxic interface. The predominance of pyrite in the mudstones indicates that sulfate reduction was the major process of organic-matter oxidation during early diagenesis.

The Paleohydrology of Lower Cretaceous Seasonal Wetlands, Isle of Wight, Southern England

ABSTRACT The floodplain deposits of the Wealden Group (Lower Cretaceous) of the Isle of Wight, southern England, were formed in a seasonal wetland setting, a type of environment widespread today along higher-order tropical and subtropical river systems but rarely identified in the geological record. The unit consists of four main lithofacies: sheet sandstones with dinosaur footprint casts; green-gray mudstones with vertebrate remains, abundant lignite, pyrite, and siderite; spectacularly color-mottled mudstones with goethite and locally pseudo-anticlines; and red mudstones with pseudo-anticlines, hematite, and carbonate nodules. The sheet sandstones are interpreted as crevasse deposits; the green-gray mudstones were deposited in shallow ponds on the floodplain, which acted as sinks for debris released by local floods following wildfires; the mottled mudstones represent surface-water gley soils formed in seasonally waterlogged areas; and the red mudstones resemble present-day Vertisols that formed on topographically elevated areas only intermittently flooded. These mudstones show vertical transitions from one to another, and although they could be interpreted as components of simple catenas, the absence of associated facies changes implies that topographic differences were not the only control. It is proposed that these three mudstone types formed as seasonal wetland catenas, in which differences in soil drainage conditions resulted from variations in the flooding hydroperiod affecting areas with minor relief differences, rather than drainage variability simply reflecting static topographic differences. Such seasonal wetland systems are rarely documented in the stratigraphic record despite being a widespread environment in present-day tropical regions, and the Wealden deposits are used to identify criteria for the recognition of this important environment in the rock record. These southern English wetlands are compared with other Lower Cretaceous wetlands from northern Spain, enabling hydrological factors which controlled deposition to be recognized.

Early diagenetic pyrite morphology in a mudstone-dominated succession: The Lower Jurassic Cleveland Ironstone Formation, eastern England

Abstract Diagenetic pyrite in the mudstones and ironstones of the Lower Jurassic Cleveland Ironstone Formation of eastern England exhibits two distinct morphologies: framboidal pyrite, commonly associated with organic matter, and euhedral pyrite, associated with detrital clay pellets. These two morphologies are mutually exclusive in occurrence. Framboidal pyrite is present in clay-rich mudstones, ooidal ironstones, apatite-rich units and some silt-rich mudstones. Euhedral pyrite is present in silt-rich and sand-rich mudstones. δ34S isotopic analysis of six samples of pyrite suggests that both types of pyrite morphology precipitated during early diagenesis from porewaters with open access to overlying sea-water, although both probably acted as sites for continued pyrite precipitation during burial. It is proposed that framboidal pyrite precipitated from iron-dominated porewaters at sites of sulfide supply (i.e. in the region of organic matter as a result of bacterial sulfate reduction) where, locally, sulfide production rates were high enough for porewaters to reach supersaturation with respect to FeS. Euhedral pyrite also precipitated from iron-dominated porewaters, but sulfide production rates from organic matter was such that FeS saturation was not reached at the sites of sulfide production. Instead, euhedral pyrite was precipitated directly from porewater when FeS2 saturation was reached. The control over pyrite morphology was probably the amount and reactivity of the organic matter within the deposited sediments. The sand-rich mudstones contained less reactive organic matter due to clastic dilution and deposition in shallower environments with O2-rich bottom waters. The ironstones and apatite-rich units were deposited under very low sedimentation rates, and as a result organic matter contents were very low and iron reduction dominated early diagenesis, which inhibited sulfate-reduction. The presence of minor framboidal pyrite within these units, however, suggests that sulfide reduction took place in micro-environments during early diagenesis.

A spatial and seasonal assessment of river water chemistry across North West England

This paper presents information on the spatial and seasonal patterns of river water chemistry at approximately 800 sites in North West England based on data from the Environment Agency regional monitoring programme. Within a GIS framework, the linkages between average water chemistry (pH, sulphate, base cations, nutrients and metals) catchment characteristics (topography, land cover, soil hydrology, base flow index and geology), rainfall, deposition chemistry and geo-spatial information on discharge consents (point sources) are examined. Water quality maps reveal that there is a clear distinction between the uplands and lowlands. Upland waters are acidic and have low concentrations of base cations, explained by background geological sources and land cover. Localised high concentrations of metals occur in areas of the Cumbrian Fells which are subjected to mining effluent inputs. Nutrient concentrations are low in the uplands with the exception sites receiving effluent inputs from rural point sources. In the lowlands, both past and present human activities have a major impact on river water chemistry, especially in the urban and industrial heartlands of Greater Manchester, south Lancashire and Merseyside. Over 40% of the sites have average orthophosphate concentrations >0.1mg-Pl(-1). Results suggest that the dominant control on orthophosphate concentrations is point source contributions from sewage effluent inputs. Diffuse agricultural sources are also important, although this influence is masked by the impact of point sources. Average nitrate concentrations are linked to the coverage of arable land, although sewage effluent inputs have a significant effect on nitrate concentrations. Metal concentrations in the lowlands are linked to diffuse and point sources. The study demonstrates that point sources, as well as diffuse sources, need to be considered when targeting measures for the effective reduction in river nutrient concentrations. This issue is clearly important with regards to the European Union Water Framework Directive, eutrophication and river water quality.

Stratigraphic control on laterally persistent cementation, Book Cliffs, Utah

Field data from the Upper Cretaceous Blackhawk Formation in the Book Clitfs (Utah–Colorado) demonstrate the presence of laterally extensive carbonate cements beneath major marine flooding surfaces. The occurrence of firmgrounds, compaction around concretions, and high minus-cement porosities indicate that cementation occurred during early diagenesis. It is proposed that the early cementation associated with these marine flooding surfaces occurred as a result of reduced sediment accumulation rates or non-depositional hiatuses linked to abrupt deepening during marine flooding. These reduced sediment accumulation rates extended sediment residence time within early diagenetic zones, leading to enhanced early cementation in shallow marine sandstones and mudstones.

Arsenic retention and release in ombrotrophic peatlands.

Organic matter can play an important role in the mobility and fate of As in the environment, but there is a lack of data on As biogeochemistry in ombrotrophic peatlands. The aim of this study was to investigate As retention and release in atmospherically contaminated ombrotrophic peat soils in the Peak District National Park (UK). Solid phase As concentrations in the peat soils exceed 25 mg kg(-1). Solid phase As and Fe concentrations are closely correlated at sites where the peat is subjected to drying and oxic conditions. In a wetter zone of the bog, solid phase As and Fe distributions are decoupled, suggesting that As retention in these systems is not solely controlled by the presence of Fe oxides. Comparison of solid phase As and Pb distributions reveals that As has been subjected to post-depositional mobility in areas of water table fluctuation. Conversely, at permanently waterlogged locations As is immobile. Detailed stream water sampling reveals that As is released from the organic-rich uplands soils into the fluvial system. Dissolved As concentrations are highly variable, with values ranging from 0.20 to 7.28 microg l(-1). Stream water As concentrations are elevated during late summer stormflow periods when there has been re-wetting of the peat after significant water table draw-down. Dissolved As is strongly correlated to dissolved organic carbon under stormflow and baseflow. The results of this study suggest that organic matter plays an important role in As dynamics in ombrotrophic peatlands, but further work is needed to identify the exact As binding and release mechanisms. Drying and re-wetting of ombrotrophic peat soils and associated changes in redox status has the potential to lead to increased As mobility. Further work is needed to provide information on how predicted climate change will influence As cycling at sites containing a legacy of atmospheric contamination.

A sequence-stratigraphic interpretation of a mudstone-dominated succession: the Lower Jurassic Cleveland Ironstone Formation, UK

Microfacies analysis (using optical and backscattered electron imagery) has been undertaken on 37 samples from the Cleveland Ironstone Formation, Staithes, Yorkshire, UK. Four lithofacies were encountered: clay-rich mudstones, silt-rich mudstones, sand-rich mudstones and concretionary carbonates (two types: berthierine/siderite-rich ironstones and apatite-rich concretionary horizons). Successive units were found to stack systematically into upward-coarsening units on a small (0.1–1.0 m) scale. Upward-coarsening and upward fining packages were also found on a larger (1.0–3.0 m) scale. The small-scale upward-coarsening units are interpreted to be parasequences; while the large scale upward-fining and upward-coarsening packages are interpreted to be retrogradational and progradational parasequence sets respectively. The ironstones occur at the level where the stacking patterns change from being overall progradational to retrogradational, while the apatite-rich concretionary units occur at the level where the stacking patterns change from being retrogradational to progradational. The concretionary carbonates are interpreted to have formed close to/at major stratal surfaces. The ironstones are interpreted to be either the correlative equivalent of sequence boundaries or part/all, of the forced regressive system tract; while the apatite-rich units are interpreted to have precipitated close to/at maximum flooding surfaces (condensed sections) and/or major transgressive surfaces.

Mineralized soft-tissue structure and chemistry in a mummified hadrosaur from the Hell Creek Formation, North Dakota (USA)

An extremely well-preserved dinosaur (Cf. Edmontosaurus sp.) found in the Hell Creek Formation (Upper Cretaceous, North Dakota) retains soft-tissue replacement structures and associated organic compounds. Mineral cements precipitated in the skin apparently follow original cell boundaries, partially preserving epidermis microstructure. Infrared and electron microprobe images of ossified tendon clearly show preserved mineral zonation, with silica and trapped carbon dioxide forming thin linings on Haversian canals within apatite. Furthermore, Fourier transform infrared spectroscopy (FTIR) of materials recovered from the skin and terminal ungual phalanx suggests the presence of compounds containing amide groups. Amino acid composition analyses of the mineralized skin envelope clearly differ from the surrounding matrix; however, intact proteins could not be obtained using protein mass spectrometry. The presence of endogenously derived organics from the skin was further demonstrated by pyrolysis gas chromatography mass spectrometry (Py-GCMS), indicating survival and presence of macromolecules that were in part aliphatic (see the electronic supplementary material).