Allt Odhar and Dalcharn: Two pre-Late Devensian/Late Weichselian sites in northern Scotland

The lithostratigraphy and biostratigraphy of two sites (Allt Odhar and Dalcharn) in north-central Scotland are described, where pollen spectra of temperate affinity have been obtained from organic deposits that underlie till. The pollen record from Allt Odhar, in association with evidence from plant macrofossils and Coleoptera, shows the expansion of birch woodland and its eventual replacement by open grassland under a climatic regime slightly cooler than that prevailing in the northern highlands of Scotland at the present day. The organic sediments accumulated during an Early Devensian interstadial episode, which has been dated by the uranium series disequilibrium method to ca. 106 ka BP. Evidence for one and possibly two Devensian glaciations may be preserved at the site. The pollen record from Dalcharn, by contrast, reflects the middle and later stages of an interglacial cycle with the transition from pine forest to grassland. The overlying till sequence contains evidence of at least two separate glacial episodes. The age of the warm stage cannot be established precisely on present evidence, but there are indications that it may predate the last (Ipswichian) interglacial. These are the first sites from the mainland of Scotland to provide evidence of wooded conditions during interstadial and interglacial episodes of the Middle/Late Pleistocene.     

Some late Pleistocene involutions at Dalton-in-Furness,northern England

Involutions are reported for the first time from northwest England. They occur in ‘head’ deposits of reworked mudstone, shale, sandstone and breccia soliflucted over glacio-fluvial sands and gravels in the Poaka Beck valley. The involutions were developed in the late Devensian period and most present a strongly festooned cross-section. Excavation of these features showed that the regular form was a result of chance sectioning and that the cryoturbate structures were a cellular or pocket type of feature. Frost heave, ice segregation and a reversed density stratification all probably contributed to the development of the involutions, but an important factor was the ground water hydrology which gave especially favourable conditions for strong cryergic activity at this site.     

Ground stress determinations in Canada

SummaryGround Stress Determinations in Canada Stress determinations with the biaxial (Doorstopper) and the triaxial strain cell of the C. S. I. R., South Africa, are discussed and show that the triaxial cell is the more desirable instrument if good rock conditions exist. Vertical and average horizontal stresses in Canada are similar in magnitude to those from other parts of the earth's crust and show that vertical stresses are related to weight of overburden and average horizontal stresses increase in most of the cases with 0.407 kg/cm² per metre of depth. More data are necessary to make any prediction for the average horizontal stress beyond a depth of 800 m.Stress determinations and a tectonic analysis show that the unravelling of the geological stress-strain history allows some prediction of principal stress directions, but the attached uncertainties due to gaps in documentation require proof by stress determinations.With 8 Figures     

Blanket mire formation at the Cross Lochs, Sutherland, northern Scotland

A brief review of the genesis of blanket peats is presented, together with detailed analyses of basal peats from northern Scotland. Particular attention is paid to local factors affecting peat growth and the problems of sampling and interpretation arising from them. Macrofossil and loss-on-ignition analyses of four peat-mineral interfaces solve many of the terminological problems of such profiles and indicate that interpretations based on field stratigraphy alone are uncertain. Pollen analyses of two profiles from contrasting microtopographic situations show well-defined vegetational change associated with early peat development. Fully organic ombrotrophic peat is present from 6805 ± 50 BP at one site, following anthropogenic burning from c . 7500 BP and partial recovery of the open birch woodland. A change from birch woodland to Calluna heath occurs at approximately the same time on a more freely drained site with much later peat development, following further burning from 4890 ± 65 BP. Anthropogenic activity is clearly associated with changes in soil and vegetation preceding peat formation, and the role of climatic factors remains equivocal.     

Jurassic and Cretaceous climate in northern USSR,from paleotemperature determinations

Information is presented on paleoternperature determinations from the rostra of Jurassic and Lower Cretaceous belen-mites in northern USSR. Mean annual paleotemperatures of the order of 13–25 °C were obtained on the basis of isotopic composition of oxygen (about 100 determinations showing the tendency for higher temperatures between the Bathonian and late Volgian times); and of the order of 10–22 °C, on the basis of Ca/Mg ratio (about 200 determinations). Seasonal fluctuations of paleotemperatures were about 5–7 °C. The conclusion is drawn that the northern reaches of Eurasia were situated approximately within the northern part of the subtropical zone - in the Toarcian, Late Jurassic, and Neocornian; and in the temperate zone - in Middle Jurassic and late Volgian times. --Authors.     

Trace-metal pollution of soils in northern England

Data from a regional geochemical survey of topsoils (n=818) in rural and peri-urban areas over a single parent material (Coal Measures) are used to identify two types of trace-metal pollution - severe local contamination at 20 sites and widespread, diffuse pollution in more densely populated areas. Median concentrations of several trace metals in topsoils were significantly higher in areas of high, compared to low, population density (percentage increases in parenthesis): As (31), Cu (39), Fe (7), Mo (26-36), Ni (29), Pb (20), Sn (40), and Zn (11). Four potential pathways of diffuse trace-metal pollution are postulated: coal-ash dispersal, atmospheric aerosols derived from coal combustion, the historical spreading of sewage waste, and those related to road vehicles. The statistical analysis of geochemical data classified by local, human population density can be an effective means of identifying the magnitude and extent of diffuse pollution, and could help to establish natural background levels.     

Multidisciplinary assessment of pollution at three sites in Long Island Sound

Winter flounder (Pseudopleuronectes americanus) were sampled from three sites located near Norwalk, New Haven, and Niantic, Connecticut, in Long Island Sound during February 1987, to evaluate the degree of chemical contamination and to determine possible effects of contaminant exposure. At each site, sediment and infaunal invertebrates were also collected and analyzed for trace metals and organic chemicals. Specimens of liver and kidney from winter flounder were examined for histopathological conditions, including the presence of macrophage aggregates in liver tissue. Liver samples were also analyzed for DNA damage (i.e., the formation of adducts between DNA and chemical contaminants). Blood samples were collected and analyzed for erythrocyte micronuclei. The sampling site near New Haven was determined to be the most affected site, from the standpoints of greater chemical contamination and possible effects on winter flounder. Concentrations of aromatic hydrocarbons (AHs) and polychlorinated biphenyls (PCBs) were highest in sediment from this site, and the highest prevalences of the histopathological changes and DNA alterations were also found in the livers of winter flounder from this site. No differences in the concentrations of contaminants in fish or in frequencies of erythrocyte micronuclei in fish blood were found between sites. None of the sites sampled had contaminant levels or prevalences of lesions as high as previously found at other East Coast locations (e.g., Boston Harbor, Massachusetts, Raritan Bay, New York). Overall, our results indicate moderate levels of pollution at two of the urban sites in Long Island Sound and provide a framework for expanded studies to better define the extent and impact of chemical pollution in Long Island Sound.     

Evolution of a Lateglacial mountain icecap in northern Scotland

Finlayson, A., Golledge, N., Bradwell, T. & Fabel, D. 2011: Evolution of a Lateglacial mountain icecap in northern Scotland. Boreas, Vol. 40, pp. 536–554. 10.1111/j.1502‐3885.2010.00202.x. ISSN 0300‐9483. Detailed geomorphological mapping of the Beinn Dearg massif, northern Scotland, was conducted to examine the maximum (Younger Dryas) extent, and earlier interstadial evolution, of an icecap that existed during the Lateglacial period (14.7–11.7 cal. ka BP). Landform evidence indicates a plateau icecap configuration during the Younger Dryas. The interpreted age is supported by new cosmogenic exposure ages and previously reported interstadial sediments beyond the icecap margin. The reconstructed Younger Dryas Beinn Dearg icecap covered 176 km². Equilibrium line altitudes (ELAs) of ～570–580 m were calculated for the icecap as a whole. The empirically reconstructed icecap is compared with recent numerical model simulations. The two methods produce an icecap with a similar configuration; however, differences are apparent in the extent of eastern and western outlets (±1–5 km), and in the spatial variation of ELAs. Results suggest that the numerical simulation overestimates the western and underestimates the eastern icecap extent. We attempt to quantify these differences in terms of icecap mass balance and assess their possible causes. Geomorphological evidence for the pre‐Younger Dryas icecap configuration indicates that the Beinn Dearg massif remained an important source during earlier deglaciation. In contrast, the neighbouring Fannich mountains acted as an ‘unzipping’ zone, and were ice‐free on their northern side by the Allerød (Greenland Interstadial 1c to 1a). Deglaciation continued over the western Beinn Dearg plateau, with the possibility that glaciers remained in some central and eastern catchments prior to (Younger Dryas) icecap (re)growth.     

Ice caps existed throughout the Lateglacial Interstadial in northern Scotland

We constrain, in detail, fluctuations of two former ice caps in NW Scotland with multibeam seabed surveys, geomorphological mapping and cosmogenic ¹⁰Be isotope analyses. We map a continuous sequence of 40 recessional moraines stretching from ～10 km offshore to the Wester Ross mountains. Surface‐exposure ages from boulders on moraine ridges in Assynt and the Summer Isles region show that substantial, dynamic, ice caps existed in NW Scotland between 13 and 14 ka BP. We interpret this as strong evidence that large active glaciers probably survived throughout the Lateglacial Interstadial, and that during the Older Dryas period (ca. 14 ka BP) ice caps in NW Scotland were thicker and considerably more extensive than in the subsequent Younger Dryas Stadial. By inference, we suggest that Lateglacial ice‐cap oscillations in Scotland reflect the complex interplay between changing temperature and precipitation regimes during this climatically unstable period (ca. 15–11 ka BP). © Natural Environment Research Council (NERC) copyright 2008. Reproduced with the permission of NERC. Published by John Wiley & Sons, Ltd.     

Implications of dissected drift at Stockdale Head,western Lake District,northern England

From mapping and consideration of prominent drift ridges at Stockdale Head, western Lake District, northern England it is inferred that the ridges are the products of dissection of a glacigenic or soliflual drift sheet rather than landforms constructed at the margins of a Loch Lomond Stade (LLS) valley‐head glacier. This proposal has implications for the recognition of LLS glacier limits and, possibly, understanding the dearth of moraine ridges associated with Dimlington ice in Lake District valleys. Copyright © 2004 John Wiley & Sons, Ltd.     

Geotechnical properties of the Great Limestone in northern England

This paper is concerned with the mechanical properties of the Great Limestone in northern England. After first outlining the geological structure of the limestone at East Layton in north Yorkshire, the problem of the basal dolomitization of the limestone is introduced and the geochemistry of the rock profile evaluated. It is shown that chemical alteration due to dolomitization is accompanied by a mechanical weakening of the rock and a reduction in the quality of the bond between a tar or bitumen coating medium and the surface of the stone. The two types of rock are compared via specific gravity, moisture absorption, unconfined compressive strength, aggregate impact and aggregate crushing tests. The results from a detailed series of shear box tests taken through from peak to residual shear strength are interpreted through the fundamental strength properties of calcite and dolomite to show that whereas in the size range 200B.S. sieve, dolomite is a little weaker than limestone due to internal weakness associated with volume change; the situation is reversed as the particles decrease in size to form an aggregate of single dolomite crystals which are inherently more resistant to shear.     

Shallow marine sedimentation in the proterozoic moine succession,northern Scotland

Shallow marine deposits are recognised from the Loch Eil division of the Proterozoic Moine Succession. Three sedimentary facies are identified: siltstone, interbedded siltstone and sandstone, and sandstone. The bulk of the succession comprises sandstones which are commonly cross-bedded. Bipolar cross-bedding is indicative of tidal activity, and the facies is considered to have accumulated in an offshore shallow marine setting. The interbedded siltstone and sandstone facies and the siltstone facies are similarly interpreted as offshore sediments deposited in areas characterised by relatively high rates of silt deposition and starvation of sand. Calc-silicate rocks represent concretions formed during diagenesis. Palaeocurrents derived from the lower part of the succession mainly flowed to the north-northeast with a subsidiary mode to the south-southwest, and probably represent longshore currents flowing broadly parallel to a palaeocoastline.     

Active ice-sheet deglaciation and ice-dammed lakes in the northern Cairngorm Mountains, Scotland

Mapping of ice-marginal and glaciolacustrine deposits in the northern Cairngorm Mountains allows the nature of deglaciation following the Last Glacial Maximum (c.18 000 BP) to be reinterpreted. Two ice-dammed lakes were ponded between the Glenmore lobe of the Scottish ice sheet and local glaciers draining northwards from the Cairngorm Mountains. Delta progradation from the southern end of each lake reflects dominant meltwater sources and glacio-hydrological gradients. Sediment facies representing subaqueous mass-flow deposits, lakebottom rhythmites, lower and upper foresets and topsets are associated with prograding delta fronts. Moraines show that the lakes were ice dammed at both ends, evidence that active glaciers existed in the Cairngorm Mountains while ice was retreating from Strath Spey, and that deglaciation was punctuated by readvances of the ice margin. These results indicate that an ice-stagnation model of deglaciation is invalid for most of the duration of ice wastage, but instead support an active-retreat hypothesis with multiple, climatically forced readvances.     

Linearization of in situ stress change formulae for gauges at arbitrary down-hole orientation

The vibrating wire stress gauge is a borehole device for measuring stress changes in situ. Three gauge arrays are required for determining changes in the secondary principal stresses. Standard data reduction formulae that use the principal axes for reference are in error because of possible changes in the principal directions. Data reduction formulae that allow for such changes and for arbitrary gauge orientations within an array are presented here. This is of considerable practical importance when installing gauges because of scheduling restrictions and hole irregularities that may preclude installation at the planned angles for which data reduction formulae exist. Linearization and thus direct inversion of the resulting system of equations, is achieved in a fixed but otherwise arbitrarily oriented Cartesian system of reference.     

Effects of rock anisotropy and heterogeneity on stress distributions at selected sites in North America

Provinces of regionally consistent horizontal stress orientations persist throughout the upper crust, and these may contain local areas where horizontal stress (σ_H) orientations seem to rotate relative to the regional stress orientations in a consistent manner. We suggest that the concept of aninclusion with anisotropy and heterogeneity of mechanical properties may be useful to explain some cases of σ_H rotations. σ_H rotations up to 50° and magnitude changes of 40% could reasonably be expected, based on simulations. Patterns correlate well with crustal observations; rotation of σ_H orientation reaches 25° to 58° in the different cases studied. We also model a strike-slip fault zone as a soft inclusion, showing reorientations of σ_Hmax which agree with observed rotations near the Murre Fault in the Jeanne d'Arc Basin, Canada. Results imply that understanding the behaviour of soft and stiff inclusions, or expanding and contracting thermal inclusions for that matter, can help explain a number of geophysical and geological phenomena related to stress patterns.     

Glacigenic rafting at Castle Hill,Gardenstown, and its significance for the glacial history of northern Banffshire,Scotland

Reinvestigation of the lower part of the key Quaternary section at Castle Hill, Gardenstown, has shown that the sediments are not in stratigraphical order, but consist chiefly of glaciotectonites, including rafts of soft sediments, which were deposited by ice moving southeastwards from the Moray Firth. Sedimentary structures are preserved in some of the rafts, which are separated by subhorizontal shears. The rafts accreted subglacially under conditions of moderate to high strain, the final glacial event being the deposition of a thin, discontinuous sheet of till, probably derived from a more westerly direction. It is proposed that interbedded dark grey shelly clay, till and sand elsewhere in northern Banffshire were emplaced, at least in part, by a similar mechanism during either the Middle Devensian, or more likely, the Late Devensian. Sand and clay with paired bivalve shells, which were formerly exposed within the Quaternary successions at Castle Hill and inland at King Edward, some 12 km to the south, are interpreted to be within glacigenic rafts, and are not in situ deposits formed during a widespread marine transgression. It is suggested that the alternation of phases of constructional and excavational deformation within a single glacial event rather than discrete glaciations provides a useful model for glacial deposition in northern Banffshire, and more generally in northeast Scotland. © 1997 John Wiley & Sons, Ltd.     

A critical evaluation of pollen-stratigraphic investigations of pre-Late Devensian sites in Scotland

This paper reviews pollen-stratigraphic evidence from proposed interglacial and pre-Late Devensian interstadial sites in Scotland. The paper has two major parts. In the first the stratigraphic details of each of the sites are summarised and discussed. The sites are classified as ‘interglacial’ or ‘interstadial’ according to the interpretations adopted by recent authors, though as discussed in later sections such distinction is problematic and somewhat arbitrary.In the second part general problems of interpretation are discussed in the light of the stratigraphic details. Problems of dating and correlation are severe since most of the sediments lie close to or beyond the limit of conventional radiocarbon dating. Thus the normal approach has been to use pollen-stratigraphic comparisons with type-sites in southern or eastern England. This practice is considered questionable. Problems of assessing the provenance of pollens and spores are perhaps even more important, and at some sites are so severe as to render pollen assemblages of limited value. The problems discussed are: (a) secondary reworking of pollen; (b) long-distance wind transport of nonregional pollen; (c) pollen deterioration and (d) low pollen concentrations.Many of the problems discussed are of general significance being applicable to late Quaternary pollen diagrams from other regions. In the concluding section of the paper certain procedures are proposed that may permit a clearer assessment of potential problems of taphonomy in pollen stratigraphy.