bluuebunny/crossref_metadata_2025_split huggingface dataset:
Early Tertiary volcanism at the western Barents Sea margin
Authors: Faleide J. I. , Myhre A. M. , Eldholm O. 
Published: April 2008

Summary
The western Barents Sea margin is composed of two regional shear segments linked by a NE-trending rifted margin SW of Bjørnøya. The primary marginal structures developed in response to the Cainozoic opening of the Norwegian-Greenland Sea. A marginal high characterizes the rifted margin segment. It is suggested that the high forms an edifice of subaerial extrusives emplaced during the initial opening of the southern Greenland Sea in the early Eocene. The extrusives also cover the adjacent continental crust and the volcanic event may have caused the deposition of tuffs in the basinal province of the southwestern Barents Sea. Renewed local volcanic activity in the early Oligocene is related to the major reorganization in plate motion at this time.
Nd, Sr and Pb isotope geochemistry of the Lower Lavas, E Greenland Tertiary Igneous Province
Authors: Holm P. M. 
Published: April 2008

SummaryNew Sr, Nd and Pb isotopic and trace-element data are presented for the Lower Lavas and some Plateau Basalts. Ranges of isotopic compositions are large among the lower and middle Vandfaldsdalen Formation lavas (87Sr/86Sr=0.7033–0.7073;143Nd/144Nd=0.5124–0.5130;206Pb/204Pb=15.1–17.5;207Pb/204Pb=14.7–15.6;208Pb/204Pb=35.0–39.1) and show a decrease in range of values with stratigraphic height. The youngest flows among the Lower Lavas have compositions similar to the Plateau Basalts of the late Skrænterne and Igtertiva Formations as well as of Nansen Fjord and Wiedemann Fjord, all of which are near to Icelandic composition (87Sr/86Sr=0.7031–0.7036;143Nd/144Nd=0.5129–0.5131;206Pb/204Pb=17.1–18.4;207Pb/204Pb=15.3–15.4;208Pb/204Pb=37.6–38.0). The lavas constitute two groups, one of which (group 2) is restricted to the lower parts of the succession. The source for this group can be modelled by mixing between an enriched old lithospheric mantle and an ocean island basalt (OIB)-type mantle with a relatively small component of depleted asthenosphere. The other group (group 1) is the most common and can be modelled by mixing between a typical Icelandic source component and a second, less enriched, lithospheric mantle component. Contamination from continental crust was of minor overall importance.The geochemical evolution in basic E Greenland Tertiary lavas is believed to reflect the interaction between the asthenospheric mantle, 3 Ga old continental lithospheric mantle and the mantle jet which is presently positioned under Iceland. With time the most enriched lithospheric source quickly decayed while the less enriched lithospheric source was important during most of Vandfaldsdalen Formation times. The OIB-type source prevailed throughout lava eruption with the asthenospheric contribution larger in the Miki Formation and the Plateau Basalts.
A review of silicic pyroclastic rocks of the British Tertiary Volcanic Province
Authors: Bell B. R. , Emeleus C. H. 
Published: April 2008

Summary
Silicic airfall and ashflow tuffs constitute a significant component of the extrusive products of the British Tertiary Volcanic Province. These deposits typically formed early in the evolution of individual volcanic centres as proximal facies accumulations intercalated with polylithic pyroclastic breccias, and occur throughout the evolution of the Province. Rhyolites and, less commonly, trachytes occur as lavas in close spatial and temporal association and, together with the silicic pyroclastic rocks, are interpreted as the extrusive equivalents of the felsic and felsic-mafic (mixed-magma) subvolcanic intrusions which are important members of the central intrusive complexes of the Province. The field relations of the silicic tuffs suggest that the associated pyroclastic breccias are also often extrusive and together they form crater infills.
The origins of lacustrine oil source rocks: evidence from the lakes of tropical Africa
Authors: Talbot M. R. 
Published: April 2008

Summary
New data from core samples are presented on organic matter accumulation during the last 10 000–15 000 years in six tropical African lakes. Pyrolysis and maceral studies indicate that in most of these lakes the preserved organic matter is a mixture of phytoplankton and higher plant remains showing varying degrees of bacterial degradation. Organic assemblages dominated by phytoplankton material have not been encountered. Sediments with the richest oil potential accumulate in meromictic or monomictic lakes during periods when the climate is humid and surface winds are relatively slack. The evidence from tropical Africa does not support current theories that shallow saline lakes may be especially favourable sites for the accumulation of oil prone sediment.
Microbial and biogeochemical processes in Big Soda Lake, Nevada
Authors: Oremland R. S. , Cloern J. E. , Smith R. L. , Culbertson C. W. , Zehr J. , Miller L. , Cole B. , Harvey R. , Sofer Z. , Iversen N. , Klug M. , Des Marais D. J. , Rau G. 
Published: April 2008

Summary

Meromictic, alkaline lakes represent modern-day analogues of lacustrine source rock depositional environments. In order to further our understanding of how these lakes function in terms of limnological and biogeochemical processes, we have conducted an interdisciplinary study of Big Soda Lake. Annual mixolimnion productivity (ca. 500 g m
−2
) is dominated by a winter diatom bloom (600f annual) caused by upward transport of ammonia to the epilimnion. The remainder of productivity is attributable to chemoautotrophs (30%) and photosynthetic bacteria (10%) present at the oxic-anoxic interface from May to November. Studies of bacterial heterotrophy and particulate fluxes in the water column indicate that about 900f annual productivity is remineralized in the mixolimnion, primarily by fermentative bacteria. However, high rates of sulphate reduction (9–29 mmol m
−2
yr
−1
) occur in the monimolimnion waters, which could remineralize most (if not all) of the primary productivity. This discrepancy has not as yet been fully explained. Low rates of methanogenesis also occur in the monimolimnion waters and sediments. Most of the methane is consumed by anaerobic methane oxidation occurring in the monimolimnion water column. Other bacterial processes occurring in the lake are also discussed. Preliminary studies have been made on the organic geochemistry of the monimolimnion sediments. Carbon-14-dating indicates a lower depositional rate prior to meromixis and a downcore enrichment in
13
C of organic carbon and chlorophyll derivatives. Hydrous pyrolysis experiments indicate that the sediment organic matter is almost entirely derived from the water column with little or no contribution from terrestrial sources. The significance of the organics released by hydrous pyrolysis is discussed.
Palaeo-environment information from deep water siderite (Lake of Laach, West Germany)
Authors: Bahrig B. 
Published: April 2008

Summary

A comparative study from modern and ancient sediments from the Lake of Laach was performed by means of chemical and stable isotope analyses. In the modern environment siderite is precipitated around CO
2
-spring vents. In contrast, siderite from the Pleistocene/Holocene boundary occurs as small layers in a varved sequence. The stable isotope data provide strong evidence for an analogous formation of both types of siderite. The different CO
2
sources of the siderites allow reconstruction of a distinct rise of productivity at the Pleistocene/Holocene transition. It is proposed that siderite may be developed as a useful tool for tracing both palaeo-environmental and early diagenetic processes.
Spores and pollen in oils as indicators of lacustrine source rocks
Authors: De-xin Jiang 
Published: April 2008

Summary
More than 200 species of fossil spores and pollen extracted from 68 crude oil samples collected from the lacustrine sedimentary basins of China, including the Talimu Basin, the Zhungeer Basin, the Jiuquan Basin, the Chaidamu Basin, the Eerduosi Basin, the Xialiaohe Depression, etc., have been investigated. The spores and pollen found in the crude oil are interpreted as a kind of ‘trace element’ indicating the pathway of the petroleum migration from the source rock to the reservoir. The principle of why some of the spores and pollen found in the crude oil can act as a kind of indicator of source rock, and the methods used to find and recognize this kind of indicator, are explained in this paper. Based on the investigations of the spores and pollen from the crude oils, the spore and pollen indicators of lacustrine petroleum source rocks of the continental sedimentary basins are proposed.
The spores and pollen acting as the indicators of the lacustrine petroleum source rocks usually indicate a tropical or subtropical wet depositional climate. It is therefore, concluded that a wet and hot climate is favourable for the deposition of lacustrine petroleum source rocks.
Lacustrine petroleum source rocks in the Dinantian Oil Shale Group, Scotland: a review
Authors: Parnell J. 
Published: April 2008

Summary

The Lower Carboniferous Oil Shale Group includes lacustrine rocks with petroleum source-rock potential. Existing data is reviewed, and new pyrolysis data is presented which shows that the oil shales
sensu stricto
are excellent source rocks with up to 30% TOC and yields of up to 180 mg/g. Other shales and dark limestones in the group also have some source-rock potential. The oil shales contain mixtures of laminar algal matter (lamalginite) and discrete algal bodies (telalginite) which represent planktonic and benthonic algal deposits. The algal bodies are
Botryococcus
-type and referable to
Pila
. There is a general correlation between % alginite and hydrocarbon yield.
Lacustrine sequences in an early Mesozoic rift basin: Culpeper Basin, Virginia, USA
Authors: Gore P. J. W. 
Published: April 2008

Summary
Lacustrine sequences in the Culpeper Basin, Virginia, USA were deposited in a half-graben dominated by fluvial sheetflood deposition. During periods of increased precipitation and runoff, lakes formed within the basin. Numerous lacustrine sequences, ranging from less than 1 m to more than 35 m thick, document the expansion and contraction of perennial freshwater and saline lakes controlled by Milankovitch-type cyclic climatic change. Many of the lacustrine sequences contain black, laminated shale, deposited in deep, anoxic water in stratified lakes. Most of the lakes were hydrologically closed, as indicated by the presence of evaporite crystal moulds and pseudomorphs in associated mudflat deposits.
Organic geochemical characteristics of major types of terrestrial petroleum source rocks in China
Authors: Jiamo Fu , Guoying Sheng , Dehan Liu 
Published: April 2008

Summary
Terrestrial source rocks, deposited under non-marine conditions in continental environments, have been divided into five major groups: Group A, sedimentary formations of big lake basins in the interior of the Chinese plate; Group B, lacustrine clastic formations in fault-bounded basins; Group C, salt lake evaporite-clastic formations in fault-bounded basins; Group D, lagoonal-lacustrine volcano-clastic formations of intermontane basins; and Group E, paralic coal-bearing formations of platform areas. The abundance, type and evolutionary characteristics of the organic matter, as well as the biomarker characteristics of various groups of source rocks are discussed briefly. There are several problems relating to evaluation of hydrocarbon prospects in terrestrial sedimentary basins, including the origin of Type I kerogens and their hydrocarbon potentials, immature oils, and coal-bearing formations as potential source rocks.
Geochemical characteristics of crude oils and source beds in different continental facies of four oil-bearing basins, China
Authors: Tieguan Wang , Pu Fan , Swain F. M. 
Published: April 2008

Summary
In order to correlate Chinese continental crude oils with their sources and, thus, the different depositional facies of the sources, the geochemical characteristics of crude oils and of extracts from related source rocks in four different types of continental facies were studied. The four types of facies were those of (1) inland and paralic freshwater to brackish lake basins, (2) saline lake basins, (3) inland swampy lake and swamp basins, and (4) terrestrial and marine intertonguing facies basins. Oils from these facies show both similarities and differences. Some specific biomarkers, such as the stereoisomers of onocerane, serratane and long chain acyclic polymethylalkanes which could be useful indicators of a palaeoenvironment, are also discussed. All the components were identified using mass spectrometry and a few retention index data: therefore, the identification of some compounds must be tentative.
The lacustrine Condor oil shale sequence
Authors: Hutton A. C. 
Published: April 2008

SummaryOrganic matter in sedimentary rocks is derived from numerous types of organisms that lived in many different environments. Australian Tertiary oil shales, for example the Condor deposit, are termed lamosites and were formed in a lacustrine environment with the bulk of the organic matter derived from freshwater planktonic algae such asPediastrum. The Condor oil shale deposit, located near Proserpine, Queensland, contains four oil shale units and a brown coal unit. The oil shales contain abundant lamalginite (or lamellar alginite), derived from planktonic freshwater algae, with a small quantity of vitrinite derived from terrestrial plants and other minor constituents. The lower oil shale unit contains a dark brown oil shale whereas the upper three oil shale units contain predominantly brown oil shale. The coal unit contains liptinite-rich cannel coals. Reflectance data for vitrinite indicate that the lower oil shale unit and the underlying coal unit are within the oil generation window.
Sand turbidites and organic-rich diatomaceous muds from Lake Malawi, Central Africa
Authors: Crossley R. , Owen B. 
Published: April 2008

Summary
Seven cores taken from 350 m water depth are described, near the foot of a rift valley boundary fault, in the anoxic hypolimnion of Lake Malawi. The sediments average 29and turbidites, 18% largely undisturbed ‘pelagic’ mud and 53% ‘pelagic’ mud disturbed by slumping and bottom currents. Diatom-rich laminae can be correlated between cores and comparison of the lithostratigraphy with limnological records permits age estimation. Sand turbidite bed thickness/maximum grain size ratios are also examined. Blooms of phytoplankton production appear to have made a major contribution to the organic-carbon content in the undisturbed ‘pelagic’ muds.
Deltaic systems and their contribution to an understanding of basin-fill successions
Authors: Elliott T. 
Published: April 2008

Summary
Deltaic systems are prominent features of many clastic basin-fill successions throughout the geological record and are also important as sites of fossil fuel reserves. The process-based classification of deltaic systems into fluvial-, wave- and tide-dominated types adopted in recent years remains valid, but requires additional information on, for example, the sediment load of the system, its position in the basin and the extent of synsedimentary deformation in order to be a meaningful characterization of a delta. The range of delta types is further extended by research into ancient deltaic systems which can result in the definition of a non-actualistic delta which differs from modern systems. This is an important trend which should develop in the future as well-constrained ancient systems are characterized to their full extent. A further avenue of future research lies in examining the nature of links of deltaic systems to shelf, slope and submarine-fan systems, with particular reference to depositional analysis of seismic stratigraphic information.
Fjord sedimentation as an analogue for small hydrocarbon-bearing fan deltas
Authors: Syvitski J. P. M. , Farrow G. E. 
Published: April 2008

Summary

Fjord basins have sediment accumulating at rates between 0.1 and more than 1000 mm a
−1
with sea-level fluctuations up to 50 mm a
−1
, lithologies varying from poorly sorted conglomerates to unimodal sands and muds, carbon contents from less than 1.0% to more than 10% for methane-producing sediments found in some anoxic basins, and variably consolidated and sensitive sediment. Four major mechanisms affect the rate and style of basin infilling: (i) hemipelagic sedimentation of particles carried seaward by river plumes; (ii) delta-front progradation, particularly as affected by bed-load deposition at river mouths; (iii) proximal slope bypassing, primarily by turbidity currents and cohesionless debris flows; (iv) down-slope diffusive processes, mainly creep and slides, that work to smear previously deposited sediment into deep water.

Fjords, with their rugged topography and dynamic history of basin infilling, are prone to slope failures. Release mechanisms include sediment loading, ground motion from earthquakes, giant waves, sea-level fluctuations and changes in the mass physical properties of basin sediments. Slope failures occur on a semicontinuous basis and with displaced volumes of 10
3
–10
6
m
3
, or with much less frequency (1000 year intervals) but affecting larger volumes of sediment (10
6
–10
9
m
3
). Although slope failures are common to the delta front, they may occur anywhere along the prograding prodelta surface, along the basin margins and over basement highs.

Sediment accumulations in fjords have many similarities to small hydrocarbon-bearing basins, such as those of the North Sea, that once received submarine fans, often experienced anoxic conditions and contained high rates of sedimentation. Fjords typically contain more sand and conglomerate than other commonly employed modern analogue environments such as the Indus, Mississippi or Amazon fans.
Two stratigraphic plays are suggested on the basis of fjord-infilling processes. The first involves the semicontinuous failure of foreset sands where, through progradation, gravity flow sands form an areally extensive reservoir (up to 10 km wide, 100 m thick and 100 km long) sandwiched between basinal muds and prodelta muds. The second play involves the catastrophic failure of a major portion of the prodelta where reservoir-quality sands (from either the basin-head delta or marginal delta-beach complexes) infill a slide-formed megachannel (up to 500 m wide, 50 m thick and tens of kilometres long). These megachannel sands would be underlain by faulted and disturbed mud blocks, and capped by conformable hemipelagic muds.
Diagenesis of Upper Carboniferous sandstones: southern North Sea Basin
Authors: Cowan G. 
Published: April 2008

Summary
Upper Carboniferous sediments from the central part of the southern North Sea Basin were deposited on a broad fluvio-deltaic plain. Potential reservoir rocks occur within distributary channel facies sandstones, but porosity and permeability have been reduced by authigenic mineral growth and improved by at least two separate phases of porosity enhancement: firstly by the infiltration of meteoric waters during post-Carboniferous uplift, and secondly by the action of acidic fluids generated during burial. The depth of invasion of meteoric fluids is highly variable, ranging from a few metres to hundreds of metres, and the best porosity is preserved in sediments which have undergone both phases of porosity enhancement. Virtually all the observed porosity in Carboniferous sandstones can be interpreted as having a secondary origin. Integrating the deduced diagenetic history with a burial and temperature history for specific wells allows the timing of diagenetic events to be estimated.
Detailed sedimentology and gamma-ray log characteristics of a Namurian deltaic succession I: Sedimentology and facies analysis
Authors: Bristow C. S. , Myers K. J. 
Published: April 2008

Summary
The aim of this study was to investigate the relationship between sedimentary facies and the gamma-ray log characteristics of the Upper Namurian Rough Rock exposed in a road section at Elland, Yorkshire. The overall succession coarsens upwards and is divided into five facies which record a prograding deltaic system. Coarse sands of a major braided fluvial distributary (Facies 1) rest upon channelled coarse sands of minor distributaries or crevasse channels (Facies 2) which overlie mouth-bar deposits (Facies 3) and more distal deltaic deposits (Facies 4). Abandonment deposits (Facies 5) occur above and between the channellized sands and the mouth-bar sands. Thus the delta front featured a series of small distributaries characterized by periodic switching in discharge and sediment transport. The shoal-water delta may have been similar to the Lafourche Delta on the Mississippi.
Arcuate and bird’s foot deltas in the late Pleistocene Palaeo-Tokyo Bay
Authors: Okazaki H. , Masuda F. 
Published: April 2008

Summary

Two types of prograding deltaic sequences are recognized in the upper part of the late Pleistocene Shimosa Group, which crops out in southern Ibaraki Prefecture and northern Chiba Prefecture, eastern Kanto, Japan. The older sequence is interpreted as a wave- and tide-dominated arcuate delta and the younger sequence as a fluvial-dominated bird’s foot delta. The older sequence is characterized by thick molluscan shell beds (
c.
10 m) in the middle part. In contrast, the younger sequence is characterized by the rhythmic alternation of fine-grained sand and mud with ripples in the lower part and coarse-grained sandy deposits with trough cross-stratification in the upper part. Both sequences show distinct coarsening-upward sequences. The difference between these two types of delta was caused by the water depth in the delta front during the lowering of the sea level from the interglacial to the glacial period during the last stage of Palaeo-Tokyo Bay.
A fluvial-dominated lacustrine delta in a volcanic province, W Greenland
Authors: Pedersen G. K. 
Published: April 2008

Summary
A 50 m thick sequence of dark grey to black non-marine shales are exposed in a 12 km section along the NE coast of Disko in W Greenland. The shales are sandwiched between sandy fluvial deposits, and the sedimentological logs demonstrate a marked lateral continuity of facies within the shale unit. The shale is fissile and micaceous, and contains locally comminuted plant debris. The average total organic carbon (TOC) content is 6%, the organic matter corresponds to type III kerogen and the dominant clay mineral is kaolinite. The shale unit constitutes one coarsening-upward sequence interpreted as lacustrine prodelta mud, with thin sheets of sand deposited from density underflows which pass transitionally up into cross-laminated mouth-bar sand finally overlain by cross-bedded sand deposited in fluvial channels. This sequence represents progradation of a fluvial-dominated delta into a lake partially bounded by subaqueous hyaloclastic breccias.