bluuebunny/crossref_metadata_2025_split huggingface dataset:
Planktic foraminifera, particle flux and oceanic productivity off Pakistan, NE Arabian Sea: modern analogues and application to the palaeoclimatic record
Authors: Schulz Hartmut , von Rad Ulrich , Ittekkot Venugopalan 
Published: April 2008

Abstract

We use the flux of bulk sediment (CaCO
3
, biogenic opal, organic carbon, lithogenic material), and of planktic foraminifera (PF) and other shell-bearing plankton from sediment trap EPT-2 off Pakistan to (1) constrain the seasonal pattern of regional productivity and (2) search for indications of the NE monsoon winter situation that may serve as a modern analogue to better reveal the seasonal climatic signals preserved in the sedimentary record of the Arabian Sea. Our trap data show a clear seasonality of fluxes that can also be traced in the composition of non-bioturbated (varved) summer and winter sediment laminae preserved within the oxygen minimum zone. In EPT-2, the flux of PF is low during summer, but during winter and late spring it is higher, as at trap station WAST, in the upwelling area of the western Arabian Sea.
Globigerina bulloides
, a PF species linked to summer upwelling and high productivity, is of minor importance off Pakistan. In contrast,
Globigerina falconensis
dominates in flux and relative abundance, and is indicative of winter mixing, when NE monsoonal winds cool the highly saline surface waters and break up stratification. An enhanced horizontal flux of suspended sediments stirred up on the shelf and upper slope is clearly shown by the peak in occurrence of small benthic foraminifera during winter. Altogether, our data suggest that the particle flux in the northeastern Arabian Sea is determined by local sediment resuspension and winter productivity rather than by summer monsoonal upwelling, representing a ‘non-upwelling’ environment, in contrast to the ‘summer upwelling’ regime off Oman, Somalia and southern India. We used this evidence to reconstruct the seasonal intensity of both monsoons for the past 25 ka: the SW and NE monsoon both were weak during the last glacial period. The NE monsoon peaked during the cool phases of the glacial to interglacial climatic transition (i.e. during the Younger Dryas (YD) and Heinrich Event H1). The SW monsoon was reinforced after the YD. Both monsoons were enhanced during early Holocene time, when summer insolation and hence atmospheric forcing was at a maximum.
Scotland’s denudational history: an integrated view of erosion and sedimentation at an uplifted passive margin
Authors: Hall Adrian , Bishop Paul 
Published: April 2008

Abstract
Denudational history is commonly reconstructed from basin sediments derived from the denuded source area, and less frequently from the source area itself. Northern Britain is an important source area for the surrounding sedimentary basins and this paper reviews the erosional history of Scotland from Devonian time to the present using evidence both from onshore geology and geomorphology and from patterns of sedimentation in surrounding basins. Cover rocks were extensive in Scotland during late Palaeozoic time but the persistence of sediment source areas within the upland areas of Scotland makes it unlikely that basement highs were ever completely buried, and depths of post-Devonian erosion of basement have been correspondingly modest (< 1–2 km). During Mesozoic time, Scotland experienced several major erosional cycles, beginning with uplift, reactivation of relief and stripping of cover rocks, followed by progressive reduction of relief through etchplanation and culminating in extensive marine transgressions in Late Triassic, Late Jurassic and Late Cretaceous time. Mid-Paleocene pulses of coarse sediment to the Moray Firth Basin coincided with major uplift. This uplift was associated with major differential tectonics within the Highlands, with warping and faulting along the margins of the Minch and the inner Moray Firth Basins. Tectonic activity was renewed on a lesser scale in late Oligocene time and continued into Late Neogene time. Differential weathering and erosion under the warm to temperature humid climates of Neogene time created the major elements of the preglacial relief, with formation of valleys, basins, scarps and inselbergs, features often closely adjusted to lithostructural controls and, in some cases, with precursors that can be traced back to Devonian time. The history that can be ‘read’ from the onshore region complements the source area history interpreted from sedimentary basins derived from these areas.
Late Neogene development of the UK Atlantic margin
Authors: Stoker M. S. 
Published: April 2008

AbstractThe late Neogene (Pliocene-Holocene) interval witnessed a significant change in sedimentation style across the UK Atlantic margin that culminated in its present morphological expression. The onset of change is marked by the creation of a regional, angular, erosional unconformity that can be traced from the Hebrides and West Shetland margins into the adjacent deep-water basins of the Rockall Trough and Faeroe-Shetland Channel. In the Rockall Trough, the unconformity is a submarine erosion surface that is dated as early Pliocene in age, betweenc.3.85 and 4.5 Ma. On the Hebrides and West Shetland margins, the dating of the unconformity is slightly less well constrained and spans the latest Miocene(?)-early Pliocene (c.5.5–3.8 Ma) interval. The formation of this unconformity may have resulted from the seaward tilting and subsidence of the shelf margin, which may have further modified the oceanographic circulation pattern in the adjacent basins. The sedimentary response to this event was relatively quick in the deep-water basins, which preserve a record of early Pliocene (post 3.85 Ma) to Holocene sediment-drift accumulation, albeit with a shift in the focus of sedimentation relative to the underlying strata. In contrast, major prograding wedges, which have contributed extensively to the construction of the Hebrides and West Shetland margins and to a lesser extent the Rockall Bank, date essentially from late Pliocene time and largely correlate with the influx of ice-rafted material to the margin. However, indications for a restricted lower Pliocene component to the shelf-margin succession suggest that this apparent delay or lag in sedimentation, relative to the basins, may be a natural response to the rate of denudation of the adjacent landmasses. The regional observations off NW Britain support the concept of Neogene tectonic uplift.
Ridge-plume interaction in the North Atlantic and its influence on continental breakup and seafloor spreading
Authors: Smallwood J. R. , White R. S. 
Published: April 2008

AbstractDevelopment of the rifted continental margins and subsequent seafloor spreading in the North Atlantic was dominated by interaction between the Iceland mantle plume and the continental and oceanic rifts. There is evidence that at the time of breakup a thin sheet of particularly hot asthenospheric mantle propagated beneath the lithosphere across a 2500 km diameter region. This event caused transient uplift, massive volcanism and intrusive magmatism, and a rapid transition from continental stretching to seafloor spreading. Subsequently, the initial plume instability developed to an axisymmetric shape, with thec.100 km diameter central core of the Iceland plume generating 30–40 km thick crust along the Greenland-Iceland-Faroes Ridge. The surrounding 2000 km diameter region received the lateral outflow from the plume, causing regional elevation and the generation of thicker and shallower than normal oceanic crust. We document both long-term (10–20 Ma) and short-term (3–5 Ma) fluctuations in the temperature and/or flow rate of the mantle plume by their prominent effects on the oceanic crust formed south of Iceland. Lateral ridge jumps in the locus of rifting are frequent above the regions of hottest asthenospheric mantle, occurring in both the early history of seafloor spreading, when the mantle was particularly hot, and throughout the generation of the Greenland-Iceland-Faroes Ridge.
The effects of longwall coal mining on overlying aquifers
Authors: Booth Colin J. 
Published: April 2008

Abstract

The hydrogeological effects of longwall mines are vertically zoned. The heavily fractured strata immediately above the mine dewater, but they are typically overlain by a zone of low permeability that prevents shallower aquifers from draining to the mine. However, shallow bedrock aquifers experience head changes caused by fracturing during subsidence. New fracture void space takes up water, causing large head drops especially in confined aquifers. Increased fracture permeability affects heads because upper aquifers in high relief areas lose water through fractured aquitards to lower aquifers, and because the higher permeabilities lower hydraulic gradients and up-gradient heads, and increase down-gradient discharge. In addition, a secondary drawdown spreads out laterally through transmissive aquifers from the potentiometric low in the subsiding zone. After undermining, water levels may recover due to closure of fractures and to recharge flowing back into the affected area. Studies at two active longwall mines in Pennsylvanian coal measures in Illinois support the conceptual model, with variations. Unconsolidated, unconfined aquifers were not significantly affected by mining. At one site, heads in a moderately transmissive sandstone declined due to mining but recovered fully afterwards. Increased permeability led to enhanced well yields, but water quality deteriorated, probably because of oxidation and mobilization of
in situ
sulphides during the unconfined and recovery phases. At the other site, heads in a poorly transmissive sandstone fell rapidly during subsidence and did not recover; hydrogeological responses varied at the site scale due to variations in bedrock-drift continuity. Predictions and monitoring schemes can be guided by the general conceptual model, but must consider local hydrogeological variations. Effects in shallow aquifers not in direct contact with the mine can be simulated using readily available flow models.
Contaminant source characterization of the San José Mine, Oruro, Bolivia
Authors: Banks David , Holden Wayne , Aguilar Eduardo , Mendez Carlos , Koller David , Andia Zelmar , Rodriguez Javier , Sæther Ola Magne , Torrico Armando , Veneros Renato , Flores Jorge 
Published: April 2008

Abstract
The San José Mine is a mothballed Ag-Sn mine near Oruro on the Bolivian Altiplano. A groundwater risk assessment has been carried out considering: (i) the current mine water pumping operation; (ii) potential future mine flooding; and (iii) mine waste leachate, at risk sources. Mine flooding rates have been simulated using two models (MIFIM and MODFLOW), with input data based on the observed water inflow distribution and calculated mine volumes. Mine water chemistry has been characterized by field analyses. Transport of contaminants in groundwater in the Quaternary sedimentary aquifer complex surrounding the mine has been assessed by empirical data and hydraulic-geochemical modelling using MODFLOW and MPATH. Empirical and modelled data suggest that no risk is (or will be) posed to Oruro’s public water supply wellfields at Challapamapa. Continued pumping and discharge of mine water poses a potential risk to surface water recipients and private groundwater abstractions located alongside these.
Hydrogeological and geochemical interactions of adjoining mercury and coal mine spoil heaps in the Morgao catchment (Mieres, NW Spain)
Authors: Loredo J. , Ordóñez A. , Pendás F. 
Published: April 2008

Abstract

Asturias, NW Spain, has a long coal and metal mining tradition including mining for mercury, which was intermittently exploited from Roman times up to 1974. In the valley of the Morgao Stream, there is a spoil heap from the Los Rueldos mercury mine immediately uphill from another one from the Morgao coal washery, both situated less than 3 km away from the town of Mieres (30,000 inhabitants). At the Los Rueldos site, arsenic is abundant in the form of As-rich pyrite. Total arsenic concentrations in representative samples from the spoil heap range from 4746 to 62 196 mg kg
−1
. Readily leachable Pb and Zn are respectively present at average concentrations of 3680 and 45 mg kg
−1
. Leachate from this spoil heap drains on to the El Batán coal spoil heap, together with acid drainage from old underground workings of the Los Rueldos Mine, which has very low pH (2.5), with up to 2900 mg 1
−1
SO
4
, and between 5.3 and 8.3 mg 1
−1
As. The total flow of polluted water from the Los Rueldos site that flows into the Morgao Stream is estimated to average 3200 m
3
year
−1
(corresponding to only 1% of the total flow from the Morgao drainage basin). Analysis of the Morgao Stream downstream of both spoil heaps clearly shows the results of the dilution effects, with the As content being lowered by more than 95%.
Hydrogeological and geochemical consequences of the abandonment of Frazer’s Grove carbonate hosted Pb/Zn fluorspar mine, north Pennines, UK
Authors: Johnson K. L. , Younger P. L. 
Published: April 2008

Abstract
The problems associated with predicting where mine water will emerge and what the quality will be in a post-closure situation are recognised world-wide. The closure of Frazer’s Grove, a fluorspar mine in the North Pennines in the UK has given the opportunity to study in detail the relationship between rising groundwater and the strata/mineworkings through which it is rising. Detailed sampling and surveys both above and underground were carried out before, during and after rebound. During the rebound phase the mine water was stratified. Since the mine water emerged in August 1999, stratification has broken up and reestablished itself twice to date. The possible causes of the break-up of stratification are examined with the aid of hydrogeochemical data and geophysical techniques. The main contaminants present in the mine water are zinc, manganese, iron and sulphate. A general exponential decrease in dissolved metal concentration in the mine water is seen with time. The hydrogeochemical data also establishes the origin of the contamination in the mine water discharge with zinc and manganese originating from Frazer’s Grove mine itself and iron from several sources. The Frazer’s Grove mine investigation provides insight into water quality and its likely development with time in abandoned mines.
Pb isotope variations in Archaean time and possible links to the sources of certain Mesozoic-Recent basalts
Authors: Luais Béatrice , Hawkesworth Chris J. 
Published: April 2008

Abstract

The present-day Pb isotope ratios of mafic and felsic rocks, feldspars and ore samples (galenas) from Archaean cratons ranging in age from 3.8–3.7 Ga to 2.6–2.7 Ga have been used to investigate their initial
207
Pb/
204
Pb ratios, and μ
1
ratios (source U/Pb ratios). Two broad trends of initial
207
Pb/
204
Pb evolution are observed, with samples from Greenland, Abitibi and SW India tending to have lower initial
207
Pb/
204
Pb ratios through time than those from eastern India, Australia and southern Africa (Kaapvaal and Zimbabwe). The calculated μ
1
values are in the range of 7–9 and they tend to be constant for a given craton through time, with Zimbabwe as a notable exception, for both mafic and felsic rock types. It follows that each craton is characterized by specific μ
1
values, or initial
207
Pb/
204
Pb ratios; μ
1
for Greenland is 7.37 ± 0.27, and they are higher for Abitibi at 7.57 ± 0.13, which are similar to SW India, where μ
1
= 7.57 ± 0.13. In Scotland μ
1
= 7.94 ± 0.152, in Finland μ
1
is 8.03 ± 0.08, in eastern India it is 8.03 ± 0.1, and for Australia μ
1
= 8.07 ± 0.14, and there tend to be higher values of 8 ± 0.2 and 8.32 ± 0.29 in the Kaapvaal and Zimbabwe, respectively. Overall, there is therefore a strong provinciality of μ
1
values in the Archaean areas, and unexpectedly the high μ
1
Archaean terranes are close to the areas of high μ
1
Mesozoic continental flood basalts (CFB), and the DUPAL anomaly in recent oceanic basalts. The cratons with high μ
1
values are in the southern hemisphere near the 130–190 Ma CFB from the Gondwana supercontinent, and the maximum DUPAL anomalies at latitudes 30–45°S south of Africa and 0–15°S south of India. The variations in μ
1
are based on
207
Pb/
204
Pb ratios, and so they primarily reflect events that took place early in Earth history. In one model, the high μ
1
values were initially generated at the core-mantle boundary, through processes linked to core formation and late accretion events, and they were mobilized in plumes responsible for at least some of the early Archaean mafic crust. Preservation of domains characterized by different U/Pb ratios is inferred to have been at relatively shallow levels, as they are preserved in both felsic and mafic rocks, and they appear to have survived for long periods of time, despite the effects of mantle convection and plate motion. Recycling of early Archaean lithosphere in the mantle by delamination might perpetuate these anomalies through time in a given area, perhaps even contributing to the modern DUPAL Pb anomalies. Delamination rather than subduction as the process of lithosphere recycling might explain why such regional domains are not observed in the kappa (κ
1
: source Th/U) ratios of these Archaean samples.
Stable isotopes in the Archaean Belingwe belt, Zimbabwe: evidence for a diverse microbial mat ecology
Authors: Grassineau N. V. , Nisbet E. G. , Fowler C. M. R. , Bickle M. J. , Lowry D. , Chapman H. J. , Mattey D. P. , Abell P. , Yong J. , Martin A. 
Published: April 2008

Abstract
Sulphide-rich sediments, stromatolitic limestones and tidal-flat deposits in the late Archaean (2.7 Ga) Manjeri and Cheshire Formations, Belingwe greenstone belt, Zimbabwe show evidence for complex and extensive prokaryotic mat communities, including (1) shallow-water coastal sulphur mats; (2) mats, probably in somewhat deeper water; (3) nearby stromatolites that lived by oxygenic photosynthesis in shallow coastal settings. Petrological and geochemical (rare earth element; REE) evidence, coupled with high-resolution stable isotope results, identifies several complex interdependent metabolic consortia of bacteria and archaea. These microbial consortia would have exchanged nutrients and products both locally within prokaryotic mats and more widely via the waters of the Belingwe basin. This isotopic, sedimentological and REE evidence for a complex ecology of bacteria and archaea is consistent with metabolic inferences from rRNA phylogeny and is direct evidence that a diverse prokaryotic community, managing carbon on a global scale, had evolved by the late Archaean.
Chitinozoa and Nd isotope stratigraphy of the Ordovician rocks in the Ebbe Anticline, NW Germany
Authors: Samuelsson J. , Gerdes A. , Koch L. , Servais T. , Verniers J. 
Published: April 2008

Abstract
Strongly tectonized Ordovician rocks appear in the Ebbe Anticline (Rheinisches Schiefergebirge), West Germany. These fine-grained detrital rocks of the Herscheider Schichten are divided into the Plettenberger Bänderschiefer. Unterer (Kiesberter) Tonschiefer, (Rahlenberger) Grauwackenschiefer, and the Oberer (Solinger) Tonschiefer. The scope of this investigation was to improve the dating of the entire Ordovician succession. but especially the Oberer (Solinger) Tonschiefer. We used chitinozoans. Palaeozoic microfossils of high biostratigraphic value, and Nd isotopes, which previously have been used for correlation and terrane affinity analysis. Chitinozoan preservation is poor, but some taxa could be confidentially identified to the species level. The ɛNd(t) values obtained from the Ordovician succession range from -8.0 to -9.2. Joint evaluation of chitinozoan and Nd isotope data together with previously known age-ranges suggest the following ages for the Herscheider Schichten: Plettenberger Bänderschiefer (early Abereiddian, earliest Llanvirn), Unterer (Kiesberter) Tonschiefer (early to mid Abereiddian, early Llanvirn). (Rahlenberger) Grauwackenschiefer (Aurelucian, earliest Caradoc), and Oberer (Solinger) Tonschiefer (late Caradoc). The Ebbe ɛNd(t) values are most readily compared with ɛNd(t) values from Avalonia. and we therefore support the inclusion of the Ordovician rocks of the Ebbe Anticline in that palaeocontinent.
Late Oligocene and early Miocene glacimarine sedimentation in the SW Ross Sea, Antarctica: the record from offshore drilling
Authors: Hambrey Michael J. , Barrett Peter J. , Powell Ross D. 
Published: April 2008

Abstract
Recent offshore drilling in the SW Ross Sea has recovered three cores with a cumulative thickness of 1500 m of Oligocene-early Miocene strata. Together with data from earlier drilling, notably from the CIROS-1 drillhole 70 km to the south (702 m of core), the cores record shallow marine glacigenic sedimentation at the margin of a rift basin bordering a mountain range that was breached by outlet glaciers from an ice sheet. This paper focuses on the late Oligocene-early Miocene record, which preserves sedimentary facies that represent warmer glacier ice and climatic conditions than are evident in the Antarctic today. Strata were cored near the South Victoria Land coast, and sedimentary facies include diamictite, conglomerate, breccia, sandstone, siltstone, mudstone and rhythmite. Facies associations, combined with seismic stratigraphic data, indicate an alternating proximal and distal marine record of glacigenic sedimentation, including phases of glacier grounding and variable degrees of iceberg rafting. Reworking by gravity-flow processes and near-shore submarine currents is also evident. These facies, together with evidence for periglacial vegetation, provide evidence of a late Oligocene-early Miocene climatic regime resembling that in the high-Arctic today. Thus, the climate was transitional between cooltemperate conditions of early Oligocene and cold-polar conditions of Quaternary time.