bluuebunny/crossref_metadata_2025_split huggingface dataset:
Large mammal turnover pulses correlated with latest Neogene glacial trends in the northwestern Mediterranean region
Authors: Azanza B. , Alberdi M. T. , Prado J. L. 
Published: April 2008

Abstract

From the latest Miocene to the Holocene period, three biotic events in the large mammal communities of the western Mediterranean region show significant and robust diversity changes and/or turnover with respect to sampling, and correspond in time to significant pulses of the latest Cenozoic glaciations. The ‘Ruscinian mammal turnover pulse’ represents a major biotic event close to the ‘Messinian salinity crisis’. This can be described more as a turnover than a dispersion event. The pattern of turnover shows a significantly high value of first appearances close to the Mio-Pliocene transition; last appearances were also important but reduced significantly in the following interval. A Southern Hemisphere glaciation event has been related to the Messinian crisis. The second major biotic event corresponds to the so-called ‘
Equus
-elephant event’ during early Villafranchian time. The relevance of this dispersal event is proved by a marked increase in diversity as a result of a high number of first appearances. Between 3.0 and 2.6 Ma the onset of bi-polar glaciations occurred, followed by glacial-interglacial cycles of moderate amplitude sustained at the orbital periodicity of 41 ka. The last major biotic event was the ‘Galerian mammal turnover pulse’ around 1.0 Ma. This turnover represents an important community reorganization that marks a total rejuvenation of the fauna and is coincident with the arrival of
Homo
species in the western Mediterranean region. At this time, glacial maxima became more extreme and the dominant periodicity of variation shifted to 100 ka, which is attributed to the massive Northern Hemisphere ice sheets.
Groundwater in the Celtic regions
Authors: Robins N. S. , Misstear B. D. R. 
Published: April 2008

Abstract
The Celtic regions of Britain and Ireland have a complex and diverse geology which supports a range of regionally and locally important bedrock aquifers and unconsolidated Quaternary aquifers. In bedrock, aquifer units are often small and groundwater flow paths short and largely reliant on fracture flow. Groundwater has fulfilled an important social role throughout history, and is now enjoying renewed interest. Groundwater quality is generally favourable and suitable for drinking with minimal treatment. However, many wells are vulnerable to microbiological and chemical pollutants from point sources such as farmyards and septic tank systems, and nitrate concentrations from diffuse agricultural sources are causing concern in certain areas. Contamination by rising minewaters in abandoned coalfields and in the vicinity of abandoned metal mines is also a problem in some of the Celtic lands.
Interdependence of groundwater and surface water in lowland karst areas of western Ireland: management issues arising from water and contaminant transfers
Authors: Coxon Catherine , Drew David 
Published: April 2008

Abstract
In lowland karsts, both surface and groundwater systems are often present. This is the case over large areas of limestone in the west of Ireland where gaining and losing streams and seasonal lakes (turloughs) are common and where much of the surface river system consists of artificial channels. A case study from County Clare illustrates the problems involved in delineating catchment areas for springs which have partially contributing surface stream sources. Case studies from counties Galway and Clare, with complex surface water-groundwater interactions, exemplify problems that may arise with water quality and quantity. Difficulties in defining realistic protection areas for groundwater resources and sources are discussed.
Shallow groundwater in drift and Lower Palaeozoic bedrock: the Afon Teifi valley in west Wales
Authors: Robins N. S. , Shand P. , Merrin P. D. 
Published: April 2008

Abstract

Detailed geological surveying in the Afon Teifi valley of west Wales has identified the distribution and geometry of a complex array of drift deposits over shales and greywackes of Silurian and Ordovician age. A well and borehole field inventory and groundwater sampling programme provides the basis for evaluating the groundwater flow patterns within these strata. Sustainable yields are mostly small with exceptional yields up to 345 m
3
d
−1
. Potential infiltration derived from an estimate of baseflow is 535 mm a
−1
; much of this discharges locally and only 9 Mla
−1
is estimated to flow longitudinally down the valley as groundwater throughflow. Total groundwater abstraction amounts to 760 Mla
−1
. Groundwater generally satisfies the EC maximum admissible concentration guideline levels and is Ca-HCO
3
to Ca-Cl type. Differences in bedrock groundwater chemistry between the western and the eastern parts of the study area are largely controlled by the drift type. By analogy, the groundwater potential demonstrated in the Afon Teifi valley is likely to be indicative of the potential in geologically similar valleys elsewhere in west and mid Wales.
Conceptual modelling of data-scarce aquifers in Scotland: the sandstone aquifers of Fife and Dumfries
Authors: Gaus I. , Dochartaigh B. É. Ó 
Published: April 2008

Abstract
Hydrogeological conceptual modelling is an essential tool in aquifer management, particularly in areas where groundwater abstraction is increasing. Conceptualization requires extensive (and expensive) amounts of data, for which resources are often lacking. This paper describes conceptual models of the Permo-Triassic sandstones in the Dumfries basin and the Upper Devonian sandstones in Fife. Data scarcity means that each aquifer requires an individually tailored approach to formulate the conceptual model and calculate the water balance. This approach can differ considerably from the standard techniques used when more data are available. The implications of data scarcity on the confidence in results are discussed and the conceptual models for both aquifers are compared.
The water resources of Bardsey, north Wales
Authors: Webb M. M. 
Published: April 2008

Abstract
Bardsey is a small island off the Welsh coast. Water supplies are drawn from spring sources but water shortages are experienced in summer. Sanitation depends on Elsan type toilets. There are limited groundwater resources in the Gwna Mélange, which is of Monian age, with groundwater transport controlled by fracture flow. There is evidence of some groundwater contamination.
Deposition of sedimentary organic matter in black shale facies indicated by the geochemistry and petrography of high-resolution samples, Blake Nose, western North Atlantic
Authors: Barker Charles E. , Pawlewicz Mark , Cobabe Emily A. 
Published: April 2008

AbstractA transect of three holes drilled across the Blake Nose, western North Atlantic Ocean, retrieved cores of black shale facies related to the Albian Oceanic Anoxic Events (OAE) 1b and 1d. Sedimentary organic matter (SOM) recovered from Ocean Drilling Program Hole 1049A from the eastern end of the transect showed that before black shale facies deposition organic matter preservation was a Type III–IV SOM. Petrography reveals that this SOM is composed mostly of degraded algal debris, amorphous SOM and a minor component of Type III–IV terrestrial SOM, mostly detroinertinite. When black shale facies deposition commenced, the geochemical character of the SOM changed from a relatively oxygen-rich Type III–IV to relatively hydrogen-rich Type II. Petrography, biomarker and organic carbon isotopic data indicate marine and terrestrial SOM sources that do not appear to change during the transition from light-grey calcareous ooze to the black shale facies. Black shale subfacies layers alternate from laminated to homogeneous. Some of the laminated and the poorly laminated to homogeneous layers are organic carbon and hydrogen rich as well, suggesting that at least two SOM depositional processes are influencing the black shale facies. The laminated beds reflect deposition in a low sedimentation rate (6m Ma−1) environment with SOM derived mostly from gravity settling from the overlying water into sometimes dysoxic bottom water. The source of this high hydrogen content SOM is problematic because before black shale deposition, the marine SOM supplied to the site is geochemically a Type III–IV. A clue to the source of the H-rich SOM may be the interlayering of relatively homogeneous ooze layers that have a widely variable SOM content and quality. These relatively thick, sometimes subtly graded, sediment layers are thought to be deposited from a Type II SOM-enriched sediment suspension generated by turbidites or direct turbidite deposition.
Biostratigraphic subdivision and correlation of upper Maastrichtian sediments from the Atlantic Coastal Plain and Blake Nose, western Atlantic
Authors: Self-Trail Jean M. 
Published: April 2008

Abstract

Detailed biostratigraphic analyses of nine cores from the Atlantic Coastal Plain and two cores from the Blake Nose, western Atlantic Ocean, provide the basis for subdivision and correlation of upper Maastrichtian sediments along a shallow- to deep-water transect. The calcareous nannofossil record from these sites shows distinct differences between the middle to outer neritic Coastal Plain sediments and the lower to upper bathyal Blake Nose sediments.
Micula murus
, a reliable marker species for low- to mid-latitude sites, is shown herein to respond to differing palaeoenvironmental conditions of nearshore v. open-ocean sites. Its usefulness as a biostratigraphic marker for neritic sediments is called into question. The last appearance datum of
Ceratolithoides kamptneri
is documented as a reliable biozone marker for latest Maastrichtian time (within CC26b) in this region. The evolutionary radiation and resulting biostratigraphic utility of species of
Ceratolithoides, Lithraphidites
and
Micula
is discussed in detail, and their first and last occurrences are tied to magneto-stratigraphic chrons where possible.
Ceratolithoides amplector, Ceratolithoides indiensis
and
Ceratolithoides pricei
are shown to be useful, biostratigraphically, in sediments deposited under bathyal conditions. Several species of
Lithraphidites
(
Lithraphidites? charactozorro, Lithraphidites kennethii
and
Lithraphidites grossopectinatus
) can be used to further subdivide upper Maastrichtian sediments at both neritic and bathyal localities. The first and last occurrence of
Micula praemurus
in Zones CC25a and CC26a, respectively, are shown to be useful biostratigraphic datum points.
Biostratigraphic implications of mid-latitude Palaeocene-Eocene radiolarian faunas from Hole 1051A, ODP Leg 171B, Blake Nose, western North Atlantic
Authors: Sanfilippo Annika , Blome Charles D. 
Published: April 2008

Abstract

Abundant well-preserved radiolarians were recovered from Ocean Drilling Program Leg 171B Hole 1051A, western North Atlantic, and range from upper middle Eocene radiolarian Zone RP16 through lower Palaeocene Zone RP6. This mid-latitude fauna contrasts with tropical faunas in lacking many tropical zonal markers and in its high proportion of diachronous first and last occurrences. The sequence from Hole 1051A contains the lower Eocene-middle Eocene and Palaeocene-Eocene (P-E) boundaries, and the only known record of a well-preserved Late Palaeocene Thermal Maximum (LPTM) radiolarian assemblage. There is no gross change observed in the composition of the fauna, only a minor increase in the number of first and last occurrences across the LPTM interval and P-E boundary. Calcareous evidence indicates two hiatuses, each 1–2 Ma long, one in the lowermost middle Eocene sequence and a second in the upper Palaeocene sequence. Presence of the middle Eocene hiatus is corroborated by an abnormally large radiolarian turnover. Twenty-six events are documented and show that most of radiolarian Zone RP10 and a substantial part of Zone RP9 are missing. Seven new species are described:
Spongatractus klausi, Calocyclas aphradia, Lychnocanoma (?) parma, Sethocyrtis austellus, Sethocyrtis chrysallis, Thyrsocyrtis (Pentalacorys) krooni
and
Thyrsocyrtis (Thyrsocyrtis) norrisi
.
Carbon addition and removal during the Late Palaeocene Thermal Maximum: basic theory with a preliminary treatment of the isotope record at ODP Site 1051, Blake Nose
Authors: Dickens Gerald R. 
Published: April 2008

Abstract

The late Palaeocene Thermal Maximum (LPTM) was a brief interval at
c.
55 Ma characterized by a −2.5 to −3‰ shift in the δ
13
C of global carbon reservoirs. The geochemical perturbation probably represents a massive input of
12
C-rich carbon to the exogenic carbon cycle. Largely unresolved issues concerning this carbon injection during the LPTM are the rates of carbon input and removal. Simple expressions are developed here to describe a δ
13
C excursion in the exogenic carbon cycle after carbon input. A change in global δ
13
C (dδ
Ex
/d
t
) can be explained to a first approximation by a set of parameters: the initial mass and isotopic composition of the global carbon cycle (
M
Ex(o)
, δ
Ex(o)
), and the fluxes and isotopic compositions of external carbon inputs, outputs and injected carbon (
F
In
, δ
In
,
F
Out
, δ
Out
,
F
Add
, δ
Add
). In general, for a given exogenic carbon cycle, a large
F
Add
or low δ
Add
results in a larger δ
13
C excursion. Likewise, for a given negative δ
13
C excursion, a large M
Ex
or low δ
Ex
requires a greater input of
12
C. Differences in
F
In
, δ
In
,
F
Out
and δ
Out
cause changes in the response of δ
Ex
over time. For a negative δ
13
C excursion of given magnitude, a greater
F
In
requires a greater input of
12
C and lessens the time for δ
Ex
to return to initial conditions. A decrease in δ
Out
(caused by an increase in the relative output of organic matter and carbonate) has a similar effect. Variable d
M
Add
/d
t
produces transients in δ
Ex
that are related to the source function but modified by carbon removal. In theory, a well-dated and representative global δ
13
C excursion could be used to derive the carbon inputs and ouputs. Ocean Drilling Program (ODP) Site 1051 has an expanded early Palaeogene section, and recent work at this location has provided a well-dated δ
13
C record across the LPTM. This δ
13
C record contains transient variations of apparently global nature. These observed transients are best explained by a pulsed injection of CH
4
into an exogenic carbon cycle with a greater carbon throughput or enhanced burial of organic matter after carbon addition.
Palaeoenvironmental implications of palygorskite clays in Eocene deep-water sediments from the western Central Atlantic
Authors: Pletsch Thomas 
Published: April 2008

Abstract
Clay mineral analyses were performed on Eocene sediments from drill sites in the western Central Atlantic. The investigated sites cover the full range of early Palaeogene deep waters above and below the calcite compensation depth (CCD), but otherwise represent different depositional and hydrographic regimes. Palygorskite clays with authigenic microstructures were discovered in Lower Eocene hemipelagic sediments from the distal end of the Blake Nose depth transect and in pelagic clays of the same age from the distal Nares Abyssal Plain, where terrigenous input was reduced. Palygorskite clays were not detected in coeval sediments from a distal near-CCD setting on Bermuda Rise that received major terrigenous input. The distribution of palygorskite clays at these sites, the microstructures of the constituent minerals, their absence from contemporaneous deposits on the American margin, and the position of the northerly sites outside the range of a potential African aeolian supply strongly suggest an authigenic origin of these clays at the early Eocene sea floor. Palygorskite clays are widely distributed in lower Eocene sediments from about 50° N to 50° S palaeolatitude. The most widespread distributions and peak abundances in Atlantic oceanic sediments are reported from shelf to deep-water sites of the palaeo-tropical and -subtropical belt and correlate with the Early Eocene period of extreme warmth. Marine authigenic palygorskite clay may provide an indication of the localities and the time periods that were characterized by high bottom-water temperatures, by elevated alkalinity, silica and magnesium concentrations, and by reduced sediment accumulation rates.
When the Wilson Cycle breaks down: how orogens can produce strong lithosphere and inhibit their future reworking
Authors: Krabbendam Maarten 
Published: April 2008

Abstract
Although poly-cyclicity is common, many orogens show a remarkable lack of reworking. In this paper, a review of some factors that may either enhance or inhibit reworking of orogens is presented. As a general rule, orogens are unlikely to rift and rework if their lithospheric strength is higher than adjacent lithosphere. The strength of the lithosphere is strongly dependent on the geothermal gradient and the rheology of the rocks; both these factors can depend on the preceding orogenic evolution, even several hundred Ma after orogenesis. Strong orogenic lithosphere is expected if the crust is composed of material with a low radiogenic heat production capacity, such as island arcs, or if the underlying sub-continental lithosphere is still thickened, as in the Urals. Extensive dehydration metamorphism, a concentration of radiogenic heat production in the upper crust and erosional thinning of the orogenic crust can also strengthen the lithosphere and inhibit reworking. However, proximity of Archean cratons and anomalously high mantle heat flow appear to strongly enhance susceptibility to reworking.
From lithospheric thickening and divergent collapse to active continental rifting
Authors: Rey P. 
Published: April 2008

Abstract
The Aegean Sea, the Alboran Sea, and the Basin and Range Province suggest that continental lithosphere following gravitational collapse may end up being thinner than it was before convergence and thickening. In order to assess the condition leading to the development of finite lithosphere thinning following convergence and convective thinning, the strength of the continental lithosphere, the gravitational force, and the rate of gravity-driven flow (spreading rate) are calculated during and after continental collision. One-dimensional numerical experiments, presented here, assume that the deformation is homogeneous, that erosion is a function of strain rate and elevation, and that thermal relaxation involves no lateral conduction of heat. Results show that if 430f the lower lithospheric mantle is dragged into the convective mantle (convective thinning), gravitational collapse may lead to a lithosphere thinner than the initial lithosphere (pre-thickening lithosphere), provided that gravitational collapse is accommodated by the passive displacement of the surrounding lithosphere (free boundary collapse). When a slightly larger volume of lithospheric mantle is removed, a phase of extension leading to a necking instability and the formation of an active rift follows collapse. The presence of fixed boundaries and/or horizontal compressive stresses strongly reduces the spreading rate and opposes finite lithosphere thinning and therefore active rifting. It is suggested that back-arc extension occurring in continental settings could exemplify post-collapse active rifting.
Geodynamics of central Australia during the intraplate Alice Springs Orogeny: thin viscous sheet models
Authors: Roberts Emily A. , Houseman Gregory A. 
Published: April 2008

Abstract

This study investigates possible mechanisms that can account for the intraplate deformation in central Australia and the Canning Basin during the Devo-Carboniferous Alice Springs Orogeny. The intraplate orogeny in central Australia seems to have occurred without the association of a significant collisional orogenic event at the plate boundary. In contrast, the present-day Tian Shan may be viewed as a consequence of the plate boundary collision which has produced the Himalayas and the Tibetan Plateau. The experiments presented in this paper examine a mechanism that produces intraplate thickening and thinning of the crust but leaves the boundary relatively undeformed. A thin viscous sheet approximation of continental lithosphere is used to demonstrate that a clockwise rotational northern boundary acting on a lithospheric sheet with an internal weak zone may produce crustal thickening in the region representing central Australia, and thinning in the region representing the Canning Basin. In this model a clockwise rotation of the northern boundary may be induced either by an eastward shear traction or by a clockwise bending moment. The relation between rotation of the boundary and maximum crustal thickening factor is, to first order, independent of the way in which deformation is driven. It depends primarily on the relative dimensions of the intracratonic weak zone. For plausible estimates of thin viscous sheet geometry and variation of lithospheric strength within the sheet, it is inferred that clockwise rotation of the northern Australian block of order 20–25° is required to produce a maximum crustal thickening factor in central Australia of order 1.67. These calculations indicate that the depth-averaged strength of the lithosphere in central Australia prior to the Alice Springs Orogeny was of order
B
0
= 0.8 × 10
13
Pa s
1/3
, assuming plausible estimates of plate boundary force of 5 × 10
12
Nm
−1
and orogenic time span of 100 Ma. Based on a simplified approximate model for lithospheric strength this strength coefficient corresponds to a Moho temperature in central Australia of order 520°C. The concentration of deformation in this relatively narrow zone that stretches E-W across the continent, implies that the blocks to the N and S are much stronger, a difference which might be explained by a decrease in Moho temperature of order 60°C. If Moho temperatures prior to the Alice Springs orogeny were higher than those estimated above, the required deformation may have been compressed into a shorter period than 100 Ma, or may have been episodic rather than continuous.
A thin-plate model of Palaeozoic deformation of the Australian lithosphere: implications for understanding the dynamics of intracratonic deformation
Authors: Braun Jean , Shaw Russell 
Published: April 2008

Abstract

Presented here are the results of a thin-plate model of the continental lithosphere in which deformation is driven by velocities specified along the plate boundaries. The geometry of the model, the strength of each lithospheric block, and the boundary conditions have been chosen to reproduce the major tectonic episodes experienced by the Australian continent during a 200 Ma time period starting in the Ordovician (i.e. 470 Ma). The model’s focus is on the reactivation and/or reworking of zones of weakness within the continent that have either been set
a priori
or developed in response to previous tectonic regimes. Using the tectonic history of the Australian continent as a natural laboratory in which hypotheses on the nature and style of intracratonic deformation can be tested, the following conclusions can be made: (i) intracratonic deformation results from the concentration of strain into regions of decreased lithospheric strength; these weak zones are often caused by previous intracratonic deformation and/or develop at the interface between regions of contrasting strength; (ii) repeated deformation episodes lead to strain localization; (iii) localized deformation may also take place as the result of the constructive interaction between two tectonic regimes originating on separate margins; and (iv) there are mechanisms that operate within the lithosphere by which deformation leads to local strengthening.