bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structure, composition and age of the Faeroe basalt plateau
Authors: Waagstein R. 
Published: April 2008

Summary

The lower Tertiary Faeroe basalt plateau is centred around the Faeroe Islands in the northern part of the supposed Faeroe-Rockall microcontinent. It consists of subaerial lavas, divided into three formations. The lower formation is probably thickest (>3 km) in the southern or central part of the islands, whereas the middle and upper formations are probably thickest (> 2 km in total) just N of the Faeroes, close to the line of opening between the Faeroes and Greenland. The lower formation consists of tholeiites relatively low in TiO
2
. The lower part of the middle formation shows an upward progression from high-Ti olivine tholeiites to high-Ti tholeiites, whereas the entire upper and rest of the middle formations consists of a contrasting population of high-Ti tholeiites and low-Ti MORB-like olivine tholeiites to tholeiites. The MORB type is confined to the northern Faeroes, increasing in abundance upwards. Similar MORB-like basalts have been recovered from further SW along the microcontinent (Faeroe Bank, Bill Bailey Bank, Lousy Bank and the Rockall Plateau), being associated with high-Ti tholeiites near the Faeroes and away from the Tertiary line of opening (Faeroe and Bill Bailey Banks). In addition, transitional to mildly alkaline basalts have been recovered on the E side of the Faeroe Bank Channel and on Bill Bailey Bank.

Based on field revision of the magnetostratigraphy of the lower formation it is tentatively suggested that the lower formation was extruded during chrons C26R to C25N and the two higher formations during C24R. Accumulation rates seem to have varied systematically and to have been related to the abundance and type of sediments between the lavas, which may indicate that extrusive activity ceased in the Faeroes before the opening of the NE Atlantic in C24R, and explain the presence of conjugate strike-slip faults in the NW Faeroes.
The spatial distribution of the various basalt types fits a model of shifting axes of intraplate volcanicity, shifting from the Faeroes to E Greenland and in part back again.
The geochemistry and origin of the Faeroe-Shetland sill complex
Authors: Gibb F. G. F. , Kanaris-Sotiriou R. 
Published: April 2008

Summary
Geochemical investigations of dolerite cores from four intrusions in the recently discovered Faeroe-Shetland sill complex have established that the sills are of transition (T) mid-ocean ridge basalt (MORB)-type composition. Some uncertainty surrounds the age of the complex, but there is no doubt that it is, at least in part, of Tertiary age. Comparisons with previously proposed models for the development of sill-sediment complexes during initial stages of seafloor spreading suggests that the Faeroe-Shetland sills may represent an intrusive episode associated with a spreading axis that eventually produced oceanic crust W of the Faeroes.
Basaltic magmatism of late Cretaceous and Palaeogene age recorded in wells NNE of the Shetlands
Authors: Fitch F. J. , Heard G. L. , Miller J. A. 
Published: April 2008

Summary

Two wells drilled by Sovereign in 1984 NNE of the Shetlands (Wells 219/28-1 & 219/28-2) passed through numerous primary basic ashfall tuff horizons within a sequence of abundantly tuffaceous rocks representing the basal early Eocene ‘ash-marker’. Small amounts of volcanic debris can be recognized in adjacent strata. In one of the wells, two chemically distinct sills of olivine-dolerite were penetrated below the ‘ash-marker’ in late Cretaceous rocks. The probable magmatic sequence revealed by petrographic studies, K/Ar and
40
Ar/
39
Ar dating is:

(1)
The near-sediment/sea water interface intrusion of a dolerite sill into Santonian strata around 80 Ma in early Campanian times (Well 219/28-2).

(2)
A major episode of explosive volcanic eruptions depositing many primary basic ashfall tuffs in the basal early Eocene (both wells).

(3)
Minor further volcanic activity continuing throughout most of the early Eocene (both wells) with two slightly more significant eruptions in the late early Eocene and early mid-Eocene respectively.

(4)
The intrusion of a dolerite sill into Campanian strata close to 50 Ma in mid-Eocene times (Well 219/28-2).
Early Tertiary basalts and tuffaceous sandstones from the Hebrides Shelf and Wyville-Thomson Ridge, NE Atlantic
Authors: Stoker M. S. , Morton A. C. , Evans D. , Hughes M. J. , Harland R. , Graham D. K. 
Published: April 2008

Summary

A sequence of Palaeocene basalts and late Palaeocene-early Eocene tuffaceous sandstones has been recovered from three boreholes on the northern Hebrides Shelf and Wyville-Thomson Ridge. The basalts, cored in boreholes 85/5B and 85/7 on the northern Hebrides Shelf, can be seismically correlated with the extensive N Atlantic lava sequence. The basalt in 85/5B displays major element chemistry typical of alkali-basalts but trace and rare-earth element (REE) patterns are typical of olivine-tholeiites. In contrast, the basalt in 85/7 displays geochemical characteristics typical of a depleted tholeiite. Despite their different compositions, the basalts have similar ratios of the highly incompatible elements La and Ta which may reflect different degrees of partial melting of similar source material. The tuffaceous sandstones, cored in borehole 85/2B on the Wyville-Thomson Ridge, were deposited in a warm, shallow marine environment contemporaneous with the reworking of nearby basaltic terrains.
Nummulites rockallensis
Hinte & Wong occurs abundantly throughout the sandstones; its only previous known occurrence is from latest Palaeocene-earliest Eocene sediments at DSDP Site 117A on Rockall Bank. Regional mapping indicates that the tuffaceous sandstones overlie the basalts, thus the latter can be assigned to the Palaeocene (or older). This is consistent with K-Ar dates of 57.3–63.1 Ma obtained from the basalts.
Time and duration of activity in the British Tertiary Igneous Province
Authors: Mussett A. E. , Dagley P. , Skelhorn R. R. 
Published: April 2008

Summary
The time and duration of igneous activity in the separate component areas of the British Tertiary Igneous Province (BTIP) are investigated using radiometric dates that pass internal consistency tests, used in conjunction with palaeomagnetic polarities and the available stratigraphic information.
Reliable results are available only for the currently subaerial parts of the Province. It is found that activity occurred within the approximate interval 63–52 Ma, with most activity at about 59 Ma. Later activity was predominantly of acid magmas though basic rocks preponderate in the province as a whole. The types and span of igneous activity in the separate areas followed no common pattern but areas of more complex geology tend to have had a longer span of activity.

Magnetic polarities are predominantly reversed, with all the lavas having this polarity. This predominance is probably largely, but not entirely, due to reversed polarity intervals being longer than normal ones at this time, and with much activity occurring in a single reversed interval. The sequence of polarities found within the BTIP cannot be fully reconciled with the polarity timescales of either Harland
et al.
(1982) or Berggren
et al.
(1985).
Rb-Sr isotopic determinations and the timing of Tertiary central complex magmatism in NE Ireland
Authors: Meighan I. G. , McCormick A. G. , Gibson D. , Gamble J. A. , Graham I. J. 
Published: April 2008

Summary

Full Rb-Sr isotopic data and whole-rock regressions are presented for each of the Mourne Mountains granites (G1–G5 inclusive) and a set of granophyres/microgranites from the Slieve Gullion central complex. The former were intruded at approximately 56 Ma (G1–G4 inclusive) and later (G5), and
may
all be younger than the major intrusions of the Slieve Gullion and Carlingford central complexes. The initial Sr isotope ratios are >0.7060 for all five Mourne granites, the Slieve Gullion granophyres/microgranites analyzed and the rhyolitic rocks of the Tardree area (Co. Antrim), and crustal involvement is indicated in their petrogenesis. In the E Mourne Centre the first (the least silicic and most Sr-rich) granite has a significantly higher initial ratio (0.7129 ± 2) than G2 (0.7109 ± 3) and G3 (0.7104 ± 6), and the isotopic data provide further support for the recent revision to the mapping of the first and second granites. Preliminary Rb-Sr isotopic data for a comprehensive suite of Tertiary rhyolites from NE Ireland, some separated by >50 km, define a linear array whose explanation is considered.
The record of early Tertiary N Atlantic volcanism in sediments of the North Sea Basin
Authors: Knox R. W. O’B. , Morton A. C. 
Published: April 2008

Summary
Volcaniclastic deposits in sedimentary sequences of the North Sea Basin and adjacent areas indicate that two phases of early Palaeogene explosive volcanism took place in the north-eastern Atlantic region. The earlier, late Palaeocene (NP5-NP6) phase involved significant activity along a N-S trend that included both the British and Faeroe-Greenland Tertiary volcanic provinces. The later phase spanned the latest Palaeocene and early Eocene (NP9 to NP13), with much or all of the activity taking place in the Faeroe-Greenland Province. Early ashfalls of mixed basaltic to silicic compositions may have included contributions from the final phase of British volcanism, but were followed by a series of 200 or more tholeiitic ashfalls of Faeroe-Greenland provenance. These tholeiitic eruptions appear to have marked the onset of separation of Greenland from Europe in mid NP10 times. A subsequent return to pyroclastic activity of more variable compositions appears to have marked the re-establishment of stresses within the E Greenland crust that continued throughout the early Eocene (mid NP10 to end NP13). The mechanism of eruption of the tholeiitic ashes, which are equivalent to a magma volume of several thousand cubic kilometres, is uncertain, but they would appear to involve hydrovolcanic processes.
Large Australian lakes during the last 20 million years: sites for petroleum source rock or metal ore deposition, or both?
Authors: De Deckker P. 
Published: April 2008

Summary
Three basic ‘regimes’ of large lakes are recognized: (1) deep lake, (2) lake with ephemeral (and shallow) water, and (3) dry lake. The characteristics of these three lake types are discussed with regard to the composition of their water and sediment chemistry, but also to their potential for the production and preservation of organic matter, as well as the adsorption and accumulation of metals. Large Australian lakes, some with a sedimentation record spanning the last 20 million years, are examined in line with the above concept. Because of the low sedimentation rates in those lakes and the present-day water chemistry predominantly leading to the precipitation of gypsum and halite (especially in the groundwater below the lakes), it appears that any organic matter that would have been produced in the lakes during their carbonate phase in Miocene time would have been consumed by bacterial activity mainly in the groundwater. It is therefore suggested that the search for sites of metalliferous accumulation may prove more rewarding than will exploration for oil within sediments deposited since the early Miocene. As a comparison with large lakes on other continents, suggestions are presented as to what would have happened if sedimentation rates were much greater and if the lakes were in proximity to volcanism.
Geochemical characterization of the organic matter from some recent sediments by a pyrolysis technique
Authors: Vandenbroucke M. , Behar F. 
Published: April 2008

Summary

A comparative study of humic acids and kerogens from recent sediments was performed using geochemical analyses of hydrocarbons released by pyrolysis of these fractions. Lacustrine samples came from the Eastern African Rift (Lake Bogoria, Lake Tanganyika) and Europe (Lake Leman), marine samples from upwelling zones (Mauritania, Arabia), and coastal land-derived sediments from Kerguelen and Svalbard islands and from a deltaic facies in Indonesia. The deposited aquatic organic matter consisted of clearly identifiable algae (diatomae, coccolithophoridae). C
14+
saturated and unsaturated hydrocarbons generated by programmed temperature pyrolysis under an inert gas flow (argon) were recovered, hydrogenated and analysed by GC. The iso- + cyclo-alkane fraction was separated, then analysed by GC-MS. Pyrolysates of humic acids, kerogens and fulvic acids reveal diverse compositions important for comparative studies. Hydrogenated hydrocarbon distributions of kerogens and humic acids can be distinguished by diminished amounts of C
14+
hydrocarbons in the latter, whereas fulvic acids generate unique hydrocarbon distributions atypical of both kerogens and humic acids. Major iso- + cyclo-alkanes in the kerogens, the main fraction of the organic matter, are isoprenoids (pristane and phytane), steranes (α cholestane) and triterpanes (C
27
and C
29
hopanes and moretanes), whatever the origin of the kerogen, whether lacustrine or marine.
Application of biological markers in the recognition of palaeohypersaline environments
Authors: ten Haven H. L. , de Leeuw J. W. , Sinninghe Damsté J. S. , Schenck P. A. , Palmer S. E. , Zumberge J. E. 
Published: April 2008

Summary

In this study the saturated and aromatic hydrocarbon fractions of a marl sample from a Messinian (late Micoene) evaporitic basin located in the northern Apennines, and four oils, Rozel Point oil (Utah, USA; Miocene) and three seep oils from Sicily (Messinian), have been studied by GC with simultaneous FID and FPD detection and by GC-MS. All samples show characteristics which might be linked to hypersaline conditions prevailing during the time of deposition. Some of these characteristics are: a very low pristane/phytane ratio (<0.1), a relatively high abundance of docosane (C
22
) and gammacerane and a series of extended hopanes and/or hop-17(21)-enes maximizing at C
35
. The aromatic hydrocarbon fraction of all samples is dominated by organic sulphur compounds of which 2,3-dimethyl-5-(2,6,10-trimethylundecyl) thiophene is the most abundant compound. The suggestion of Meissner
et al.
(1984), that the source rock of Rozel Point oil was deposited under hypersaline conditions in a playa-like system, is supported by the organic geochemical characteristics of this oil.
Possible relationships of stratigraphy and clay mineralogy to source rock potential in lacustrine sequences
Authors: Yuretich R. F. 
Published: April 2008

Summary
Petroleum accumulations in lacustrine environments often possess characteristics different from those in marine settings. In general, lacustrine petroleum fields are smaller, the oil has often not migrated far from the source, and oil shales are common. Some of these differences can be attributed to the relative youthfulness of lacustrine basins and to differences in the type of organic matter present. However, additional influences may arise from the stratigraphic framework and clay composition of the source rocks. The scale of the environment may be a major controlling factor. Gradations between large lakes and marginal marine basins exist, but lake basins will more often be areally small, relatively shallow and subject to frequent lateral migrations in depositional environments. These characteristics make the resulting sedimentary sequences much more heterogeneous, both in stratigraphic relationships and in sediment composition. Stratigraphy will ultimately influence the migration and accumulation of the oil; the sediment composition—particularly clay mineralogy—will affect the generating potential of the source rock. Shifting sediment source areas coupled with lake level fluctuations and early diagenetic reactions may produce thin mudstones containing very heterogeneous clay mineral assemblages, which, accordingly, may not undergo significant transformations during burial diagenesis.
Cenozoic lacustrine basins of South-east Asia, their tectonic setting, depositional environment and hydrocarbon potential
Authors: Gibling M. R. 
Published: April 2008

Summary
Cenozoic strike-slip tectonism, which caused local crustal extension in South-east Asia, generated many short-lived but deeply subsiding basins. Under tropical conditions and assisted by intensive karstic weathering, the basins formed ideal sites for lakes during early basinal history in Oligocene to Miocene times. In several basins in northern Thailand, a shallow-lacustrine assemblage of mudstone and coal contains thin, alginite-rich oil shales of moderate grade which formed under oxic or anoxic conditions during the initial flooding of the lake, which was accompanied by high organic productivity. In the Mae Sot Basin, a carbonate-rich lacustrine assemblage contains thick, alginite-rich oil shales of high grade which formed under anoxic conditions in deeper, probably stratified lakes where the organic material was well preserved. The kerogen in both assemblages is Type I, hydrogen-rich. Under conditions of rapid sedimentation and abnormally high heat flow associated with active tectonism, the shallow-lacustrine oil shales have generated hydrocarbons which are exploited in several basins.
Anoxic-oxic cyclical lacustrine sedimentation in the Miocene Rubielos de Mora Basin, Spain
Authors: Anadón P. , Cabrera L. , Julià R. 
Published: April 2008

Summary
The Rubielos de Mora Basin is a Miocene half-graben (3 × 10 km) with a sedimentary fill of over 600 m of alluvial and lacustrine sequences. Three main units make up this basin infill: lower (alluvial) and middle and upper lacustrine units. The upper lacustrine unit is mainly formed in the western part of the basin, by cyclical sequences. These sequences consist of organic-poor, non-laminated mudstones and marls cyclically alternating with thinly laminated facies such as sandy mudstones, bioclastic laminae, oil shales, rhythmites (carbonate-clay, varve-like couplets) and marls. Low-Mg calcite and non-stoichiometric (Mg-poor) dolomite are the dominant carbonate minerals in the non-laminated facies, whereas variable amounts of low-Mg calcite, high-Mg calcite, aragonite and non-stoichiometric dolomite have been recorded in most of the laminated facies. Low-Mg calcite is the main carbonate mineral in sandy mudstones and bioclastic laminae which occur at the lower part of laminated intervals in the cycles. Analysis of oil shales reveals a major macrophyte contribution of organic matter, displaying an early diagenetic evolutionary stage. Cyclical sequences record alternating oxic-anoxic bottom conditions in marginal zones of a meromictic lake, due to cyclical changes in lake water volume. This feature is recorded in the cyclical sequences of mineralogical changes and facies transitions. Strong tectonic subsidence (not balanced by sedimentation and taking place in an active rift setting) and palaeoclimate were the most striking features which could favour the establishment of a meromictic lake during this stage of the basin history.
Profiles of fan deltas and water depth in the receiving basin
Authors: Ito M. 
Published: April 2008

Summary

Profiles of prograding fan deltas are largely controlled by the water depth in the receiving basin. The initial slope of the fan-delta front with respect to that of the fan-delta plain, which is sometimes detectable in stratigraphic packages, decreases with the increase in water depth at the toe of fan-delta front deposits. The resultant relationship provides important evidence and information for restoring the depositional architecture of ancient fan deltas that may reflect the marginal geometry of sedimentary basins. Relatively steep gradients in fan-delta accretion surfaces may lead to an overestimation of the
vertical
stratigraphic thickness, particularly if it is calculated using a simple cumulative bed thickness. Furthermore, fan-delta successions which appear to be anomalously thick may not be due to progressive or incremental basin subsidence, but rather to overestimated stratigraphic thickness because the fan-delta clinoform dips were ignored. A part of the thick fan-delta deposits, therefore, can best be interpreted in terms of lateral accretion of fan-delta front deposits on the dipping clinoform surfaces, responding to the shallowing in the receiving basin.
Detailed sedimentology and gamma-ray log characteristics of a Namurian deltaic succession II: Gamma-ray logging
Authors: Myers K. J. , Bristow C. S. 
Published: April 2008

Summary
A portable gamma-ray spectrometer was use to measure the total radioactivity, potassium content (% K), uranium content (ppm U) and thorium content (ppm Th) in the Upper Namurian Rough Rock at an outcrop in a road section at Elland, Yorkshire. The total gamma radiation generally decreases upwards in the succession, reflecting an upward increase in grain size. Gamma-ray peaks within the succession are due partly to facies/grain-size changes and partly to concentrations of thorium-bearing monazite in mouth-bar sandstones and basal channel lags. Failure to identify the true nature of these peaks could lead to erroneous correlations in the subsurface. The Th/K ratio decreases upwards in association with the increase in grain size and a decrease in the quartz/feldspar ratio. The Th/K ratio and Th-K cross-plots are effective in distinguishing some of the deltaic facies.
Nile Delta: a review of depositional environments and geological history
Authors: Sestini G. 
Published: April 2008

Summary
The distribution of the Holocene-Recent sedimentary environments of the Nile Delta is related to secular variations of the semi-arid climate and of the Nile River sediment input and flux, and to coastal subsidence and high wave energy, together with an eastward littoral drift. The delta started to form in the Late Pliocene, with its main development taking place in the Pleistocene, associated with progradation of large volumes of coarse coastal delta sands and the offshore accumulation of turbidities (Nile Cone). In the Oligocene-Early Miocene, an ancestral Nile discharged to the NW. Fluvio-deltaic deposits appeared in the present delta area in the Late Miocene, where they built a narrow prism close to an active faulted flexure, which in the subsurface now separates the South Delta Block from the deep North Delta Basin. The stratigraphy, structure and depocentre development of the region are functions of the interaction between the E-W- to WSW-ENE-trending Mediterranean margin structures, active since the end of the Cretaceous, and the NW-, NNW- and NNE-trending Red Sea-Gulf of Suez structural fabric associated with arching and rifting from the Oligocene to Pleistocene. The main phases of tectonic activity and of clastic deposition, which also correlate with lowered sea levels, were in Late Oligocene-Early Miocene, late Middle Miocene, Tortonian-Messinian, Middle Pliocene and Early-Middle Pleistocene. Petroleum exploration in the Nile Delta has produced modest results to date with a few medium-sized gas fields and minor oil discoveries.