bluuebunny/crossref_metadata_2025_split huggingface dataset:
Anatomy, hydrodynamics and depositional setting of a Westphalian C lacustrine delta complex, West Midlands, England
Authors: GLOVER B. W. , O'BEIRNE A. M. 
Published: June 2006

ABSTRACTStudies, spanning a 3 year period, of Westphalian C strata exposed in an active quarry have enabled three dimensional reconstruction of a lacustrine delta complex. The sequence exhibits a complex history of lake infilling by sediment introduced by intermittent high energy, low sinuosity distributary channel flows.Deposition in the small 0.2 km2 lake prior to delta formation was dominated by organic matter and typified rheotrophic swamp conditions. Large lycopods colonized the swamp floor. The lake was filled by a prograding delta which comprised six horizontally and vertically stacked delta lobes. The presence of lycopods aided sediment accumulation.Fluctuations in river discharge and consequent lake level rise and fall exerted a fundamental control on delta progradation and aggradation. Flooding during low lake levels first produced erosion on the existing lobe followed by a lake level rise which created accommodation for aggradation of a new delta lobe. Further lobe erosion and low stand lobe formation occurred during lake level fall.The area's proximity to alluvial fans resulted in hyperconcentrated flood flow within the distributary channels. The occurrence upon in‐channel surfaces of plant colonization, including lycopods, testifies to the ephemeral nature of the flow. The lacustrine delta complex formed at the front of a terminal alluvial fan. Northward progradation of the alluvial fan was achieved by the capture and infilling of lakes by northerly flowing distributary channels.
Origin and migration of palaeofluids in the Upper Visean of the Campine Basin, northern Belgium
Authors: MUCHEZ PHILIPPE , MARSHALL JIM D. , TOURET JACQUES L. R. , VIAENE WILLY A. 
Published: June 2006

ABSTRACTUpper Visean limestones in the Campine Basin of northern Belgium are intensively fractured. The largest and most common fractures are cemented by non‐ferroan, dull brown‐orange luminescent blocky calcite.First melting temperatures of fluid inclusions in these calcites are around ‐57°C, suggesting that precipitation of the cements occurred from NaCl‐CaCl2‐MgCl2 fluids. The final melting temperatures (Tmice) are between ‐5 and ‐33°C. The broad range in the Tmice data can be explained by the mixing of high salinity fluids with meteoric waters, but other hypotheses may also be valid. Homogenization temperatures from blocky calcite cements in the shelf limestones are interpreted to have formed between 45 and 75°C. In carbonates which were deposited close to and at the shelf margin, precipitation temperatures were possibly in the range 70‐85°C and 72‐93°C, respectively.On the shelf, the calcites have a δ18O around ‐9.3‰ PDB and they are interpreted to have grown in a fluid with a δ18O between −3.5 and +1.0‰ SMOW. At the shelf margin, blocky calcites (δ18O∼ ‐ 13.5‰ PDB) could have precipitated from a fluid with a δ18O betweenn ‐4.0 and ‐1.1‰ SMOW. The highest oxygen isotopic compositions are comparable to those of Late Carboniferous marine fluids (δ18O= ‐ 1‰ SMOW). The lowest values are more positive than a previously reported composition for Carboniferous meteoric waters (δ18O= ‐7‰ SMOW). Precipitation is likely to have occurred in marine‐derived fluids, which mixed with meteoric waters sourced from near the Brabant Massif. Fluids with a similar negative oxygen isotopic composition and high salinity are actually present in Palaeozoic formations. The higher temperature range in the limestones near the shelf margin is explained by the upward migration of fluids from the ‘basinal’ area along fractures and faults into the shelf.
Grain size distribution in suspension from bed materials
Authors: MAZUMDER B. S. 
Published: June 2006

ABSTRACTExperimental results show that the grain size distribution of suspended material is related to flow parameters and grain size distribution in the bed. A theoretical model has been developed to compute the suspension grain size distribution on the basis of diffusion equations, taking into account the effect of hindered settling due to the increased concentration in suspension. Fluid velocity closest to the bed is estimated by using the concept of migration velocities of particles in the bed layer. Comparisons of data computed by the proposed method and data from actual observations show generally good agreement.
Laminaset geometries in fine grained shallow marine sequences: core data from the Rannoch Formation (North Sea) and outcrop data from the Kennilworth Member (Utah, USA) and the Bencliff Grit (Dorset, UK)
Authors: CORBETT P. W. M. , STROMBERG S. G. , BRENCHLEY P. J. , GEEHAN G. 
Published: June 2006

ABSTRACTSandbodies from storm‐dominated marine and marginal marine environments commonly contain intervals of laminated fine sandstones. A characteristic of such lamination is the presence of low angle cross lamination. In order to model correctly the effects of such lamination on a waterflood of an oil‐bearing shoreface sequence it was necessary to quantify the geometry of the laminaset elements.This challenge has been greatly complicated by the lack of outcrop of the formation of interest. The Middle Jurassic Rannoch Formation of the North Sea only occurs in the subsurface where it is not possible in core to measure the aspect ratio of laminasets directly. In this study, the laminaset geometry data that can be obtained from core (e.g. apparent set thicknesses) were collected for the Rannoch Formation. These data were compared with similar data from potential outcrop analogues in (1) the Cretaceous Kennilworth Member of the Blackhawk Formation in Utah, USA and (2) the Upper Jurassic Bencliff Grit from the Dorset coast, UK.A quantitative analysis of laminaset geometries has been used to compare subsurface core with potential outcrop analogues. The Rannoch Formation core is characterized by numerous low angle truncations. We have measured these features in two wells (means of 7.2° and 12.1°). Mean apparent set thicknesses were 0.24 and 0.19 m.In the outcrop sections studied, truncation angles ranged from 9.6° to 13.4° and mean set thicknesses from 0.24 to 0.34 m. Mean bounding surface dips of 5.8° and 8.6°, and mean laminaset lengths of 2.3 and 4.1 m were also measured. directly in the field and by using photomosaics.On the basis of this comparison, the Kennilworth Member in Utah was found to be the most suitable and the geometries (i.e. aspect ratios) measured there were used to generate an appropriate geometry of Rannoch laminaset geometries for use in engineering studies: laminaset length, 2.0 m; laminaset thickness, 0.2 m.
River systems and their sediment flux, Indo‐Gangetic plains, Northern Bihar, India
Authors: SINHA RAJIV , FRIEND PETER F. 
Published: June 2006

ABSTRACTRiver systems of part of the Himalayan foreland, northern Bihar plains, India, are described in terms of their channel morphology, hydrology and suspended sediment characteristics. A simple classification of the river systems based mainly on the source area characteristics is proposed: (i) mountain‐fed, (ii) foothills‐fed, (iii) plains‐fed and (iv) mixed‐fed rivers. Distinct differences are noted between these classes of river systems. Most rivers show evidence of channel movement, mainly by avulsion, but cut‐offs also occur locally. The mountain‐fed rivers are characterized by very high discharge and low suspended sediment concentration and the plains‐fed rivers have relatively low discharge and high suspended sediment concentration. The foothill‐fed rivers have moderate values of discharge and suspended sediment concentration. The mountain‐fed rivers have built megafans of large extent, whereas the foothills‐fed and plains‐fed rivers have formed muddy interfan areas. Semi‐quantitative estimates of water and sediment flux suggest that about 99·9% of the mass transfer into the plains is water, with the remaining 0·1% being sediment, and that 10% of the latter (0·01% of the total) is retained in the basin, the remainder being transferred to the Bengal Fan.
Sedimentological characteristics and facies of the evaporite‐bearing Kirmir Formation (Neogene), Beypazari Basin, central Anatolia, Turkey
Authors: YAĜMURLU FUZULI , HELVACI CAHIT 
Published: June 2006

ABSTRACTA thick sedimentary sequence comprising fluvial, lacustrine and volcano‐sedimentary rocks is present in the Neogene Beypazari Basin, central Anatolia. These units display considerable lateral facies variation and interfinger with alkaline volcanic rocks along the north‐eastern margin of the basin. The uppermost Miocene Kirmir Formation contains numerous evaporite horizons. The evaporite sequence is up to 250 m thick and may be divided into four lithofacies. In ascending stratigraphical order these are: (1) gypsiferous claystone facies, (2) thenardite‐glauberite facies, (3) laminar gypsum facies and (4) crystalline gypsum facies. These facies interfinger with one another laterally along a section from the margins to central parts of the basin. The lithological and sedimentological features of the Kirmir Formation indicate fluvial, saline playa mudflat, hypersaline ephemeral playa lake and very shallow subaqueous playa lake depositional environments, which probably were influenced by alternating semi‐arid and evaporative conditions.
The development of small scale bedforms in tidal environments: an empirical model for unsteady flow and its applications
Authors: OOST ALBERT P. , BAAS JACO H. 
Published: June 2006

ABSTRACTDimensions and plan morphology of current ripples are generally considered to vary with flow velocity and grain size. Recently, however, it has been shown that for sand of D50=0.095 and 0.238 mm the equilibrium dimensions are identical at all velocities within the stability field of ripples and that the plan form of equilibrium ripples is linguoid. On this basis, an empirical unsteady flow model has been developed and tested with flume experiments in order to predict ripple development in natural depositional environments. The model includes the development of washed‐out ripples and upper stage plane bed. The unsteady flow model explains the development and preservation of small scale bedforms in various tidal environments more accurately than previous models. Such bedforms can serve, therefore, as indicators of prevailing hydrodynamic conditions.
Diagenesis of an Upper Triassic reef complex, Wilde Kirche, Northern Calcareous Alps, Austria
Authors: SATTERLEY ARTHUR K. , MARSHALL J. D. , FAIRCHILD I. J. 
Published: June 2006

ABSTRACTThe Wilde Kirche reef complex (Early‐Late Rhaetian) grew as an isolated carbonate structure within the shallow Kössen Basin. At the Triassic/Jurassic boundary a single brief (c.10–50 ka) period of subaerial exposure occurred. The preserved karst profile (70 m thick) displays a vadose zone, enhanced dissolution at a possible palaeo‐watertable (5–15 m below the exposure surface), and a freshwater phreatic zone. Karst porosity was predominantly biomouldic. Primary cavities and biomoulds were enlarged and interconnected in the freshwater phreatic zone; cavity networks developed preferentially in patch reef facies. Resubmergence of the reef complex allowed minor modification of the palaeokarst surface by sea floor dissolution and Fe‐Mn crust deposition on a sediment‐starved passive margin.Fibrous calcite (FC). radiaxial fibrous calcite (RFC) and fascicular optic calcite (FOC) cements preserved as low Mg calcite (LMC) are abundant in primary and karst dissolution cavities. FC cement is restricted to primary porosity, particularly as a synsedimentary cement at the windward reef margin. FC, RFC and FOC contain microdolomite inclusions and show patchy non‐/bright cathodoluminescence. δ18O values of non‐luminescent portions (interpreted as near original) are − 1.16 to − 1.82%0 (close to the inferred δ18O of calcite precipitated from Late Triassic sea water). δ13C values are constant (+3 to + 2.2%0). These observations suggest FC, RFC and FOC were originally marine high Mg calcite (HMC) precipitates, and that the bulk of porosity occlusion occurred not in the karst environment but in the marine environment during and after marine transgression. The HMC to LMC transition may have occurred in contact with meteoric water only in the case of FC cement. The most altered (brightly luminescent) portions of RFC/FOC cements yield δ18O=−2.44 to − 5.8%0, suggesting HMC to LMC alteration at up to 34°C. in the shallow burial environment at depths of 180–250 m.Abundant equant cements with δ18O =−4·1 to −7.1%0 show crisp, uniform or zoned dull luminescence. They are interpreted as unaltered cements precipitated at 33–36°C at 200–290 m burial depth, from marine‐derived fluids under a slightly enhanced geothermal gradient. Fluids carrying the equant cements may have induced the HMC to LMC transition in the fibrous cements.
Neptunian dykes and associated features in southern Spain: mechanics of formation and tectonic implications
Authors: WINTERER E. L. , SARTI M. 
Published: June 2006

ABSTRACTNeptunian dykes and sills in Jurassic carbonate platform strata of the Betic region of Spain occupy spaces created by wholly mechanical fracturing and displacement of the host strata, and later filled by pelagic sediments from above or by precipitation of calcite from circulating solutions. In some places, joint‐bounded blocks of platform carbonates have been wholly removed, possibly by sliding down submarine slopes, leaving a staircase topography, commonly Fe‐encrusted, that was subsequently filled by pelagic sediments. Other cavities that formed during Cretaceous times were developed by dissolution and current erosion in moderately deep submarine environments, and then filled by pelagic sediments from above.None of the cavities hosted by either platform or pelagic strata contain evidence for their formation by dissolution in a subaerial environment. The Jurassic and Cretaceous history of subsidence of the Betic margins is thus simpler than in versions requiring repeated emergence to form subaerial karstic cavities.
Discrimination between coastal subenvironments using textural characteristics
Authors: SUTHERLAND ROSS A. , LEE CHEING‐TUNG 
Published: June 2006

ABSTRACTThe objective of this study was to discriminate between modern beach subenvironments based on textural characteristics obtained using the graphical (percentile) method, the moment method, and the log‐hyperbolic distribution (LHD). A total of 126 surface sedimentation units were sampled at the nodes of a 21 x 6 rectangular grid (1000 m2) on a carbonate sand beach, Oahu, Hawaii. Sampling was conducted at low energy conditions from the lower foreshore to the backshore. Non‐parametric discriminant analysis was used as an objective tool in defining distinct subenvironments. Confidence bands around the canonical variates derived from the graphic mean, sorting, skewness and kurtosis indicated four separate subenvironments (lower foreshore, mid‐foreshore, upper foreshore and backshore). Three distinct subenvironments were identified using the mean, sorting (standard deviation) and skewness measures derived by the method of moments. A similar subenvironment distinction was obtained using five statistics of the LHD (gamma, γ; nu ν; delta, δ; tau, τ; and xi, ξ). No significant difference was noted in textural characteristics between the upper foreshore and backshore zones, and these zones were grouped into one subenvironment. These results indicate that different process scenarios would be needed to explain different subenvironment partitioning based simply on the approach adopted. Discriminant analysis indicated that fewer subenvironment samples were misclassified and separation distances between subenvironments in bivariate canonical plots were greater for the standard moment measures compared with the statistics derived from fitting the computationally intensive LHD model. Examination of the mass frequency grain size distributions indicated that the LHD was generally the most appropriate model. These observations were confirmed by the hyperbolic shape triangle which indicated that the LHD rather than the more commonly used log‐normal distribution was generally optimal in describing sediments. These results support the use of the LHD statistical measures in subenvironment discrimination over the graphic‐inclusive measures.
The carbonate factory of Middle Triassic buildups in the Dolomites, Italy: a quantitative analysis
Authors: BLENDINGER W. 
Published: June 2006

ABSTRACTMiddle Triassic carbonate buildups of the Dolomites were high in relief (500–1000m) and small in size (one to a few square kilometres in area). A paradox results from the carbonate platform model that invokes the platform top, including reef rims, as the carbonate factory and flanking beds as talus deposits. Most buildups consist largely of clinoforms (inclined at 10‐50°) whereas massive reef rocks and stratified buildup interiors are poorly developed or absent. Facies and modal analysis of 323 thin sections from buildups of the Marmolada indicate that clinoforms are: (i) predominantly composed of in situ boundstones (56% of all samples); (ii) primarily made up of early cements (37 vol.%), microbial crusts (17 vol.%), micritic intraclasts (10 vol.%) and Tubiphytes (8 vol.%); and (iii) contain diagnostic shallow water grains (dasyclads, coated grains) that are less abundant by 1‐2 orders of magnitude compared with buildup interior facies. These data suggest that the clinoforms themselves were the main carbonate factory of the Triassic buildups. Stratified buildup interior rocks and massive reef rocks were apparently not a prerequisite for buildup growth and clinoform progradation.
Replacement of evaporites within the Permian Park City Formation, Bighorn Basin, Wyoming, USA
Authors: ULMER‐SCHOLLE DANA S. , SCHOLLE PETER A. 
Published: June 2006

ABSTRACTThe Permian Park City Formation consists of cyclically bedded subtidal to supratidal carbonates, cherts and siltstones. Early diagenesis of Park City Formation carbonates occurred under the influence of waters ranging from evaporative brines to dilute meteoric solutions and resulted in evaporite emplacement (syndepositional nodules and cements), as well as dolomitization, silicification and leaching of carbonate grains.Major differences are seen, however, in the diagenetic patterns of subsurface and surface sections of Park City Formation rocks. Subsurface samples are characterized by extensively preserved evaporite crystals and nodules, and preserve evidence of significant silicification (chert, chalcedony and megaquartz) and minor calcitization of evaporites. In outcrop sections, the evaporites are more poorly preserved, and have been replaced by silica and calcite and also leached. The resultant mouldic porosity is filled with widespread, very coarse, blocky calcite spar.These replacements appear to be multistage phenomena. Field and petrographic evidence indicates that silicification involved direct replacement of evaporites and occurred during the early stages of burial prior to hydrocarbon migration. Siliceous sponge spicules provided a major source of silica, and the fluids involved in replacement were probably a mixture of marine and meteoric waters. A second period of replacement and minor calcitization is inferred to have occurred during deep burial (under the influence of thermochemical sulphate reduction), although the presence of hydrocarbons probably retarded most other diagenetic reactions during this time interval. The major period of evaporite diagenesis, however, occurred during late stage uplift. The late stage replacement and pore‐filling calcites have δ13C values ranging from 0·5 to ‐25·3%, and δ18O values of ‐16·1 to ‐24·30 (PDB), reflecting extensive modification by meteoric water. Vigorous groundwater flow, associated with mid‐Tertiary block faulting, led to migration of meteoric fluids through the porous carbonates to depths of several kilometres. These waters reacted with the in situ hydrocarbon‐rich pore fluids and evaporite minerals, and precipitated calcite cements.The Tosi Chert appears to have been an even more open system to fluid migration during its burial and has undergone a much more complex diagenetic history, as evidenced by multiple episodes of silicification, calcitization (ferroan and non‐ferroan), and hydrocarbon emplacement.The multistage replacement processes described here do not appear to be restricted to the Permian of Wyoming. Similarly complex patterns of alteration have been noted in the Permian of west Texas, New Mexico, Greenland and other areas, as well as in strata of other ages. Thus, multistage evaporite dissolution and replacement may well be the norm rather than the exception in the geological record.
Recrystallization of dolomite: evidence from the Monterey Formation (Miocene), California
Authors: MALONE MITCHELL J. , BAKER PAUL A. , BURNS STEPHEN J. 
Published: June 2006

ABSTRACTDolomites from the upper calcareous‐siliceous member of the Miocene Monterey Formation exposed west of Santa Barbara, California, were analysed for geochemical, isotopic and crystallographic variation. The data clearly document the progressive recrystallization of dolomite during burial diagenesis in marine pore fluids.Recrystallization is recognized by the following compositional and crystallographic variations. Dolomites have decreasing δ18O and δ13C compositions, decreasing Sr contents and increasing Mg contents with increasing burial depths and temperatures from east to west in the study area. δ18O values vary from 5·3‰ in the east to − 5·5‰ PDB in the west and are interpreted to reflect the greater extent and higher temperature of dolomite recrystallization in the west. δ13C values correlate with δ18O and decrease from 13·6‰ in the east to − 8·7‰ PDB in the west. Sr concentrations correlate positively with δ18O values and decrease from a mean of 750 ppm in the east to a mean of 250 ppm in the west. Mol% MgCO3 values inversely correlate with δ18O values and increase from a minimum of 41·0 in the east to a maximum of 51·4 in the west.Rietveld refinements of powder X‐ray diffraction data indicate that the more recrystallized dolomites have more contracted unit cells and increased cation ordering. The fraction of the Ca sites in the dolomites that are occupied by Ca atoms increases slightly with the approach to stoichiometry. The fraction of the Mg sites occupied by Mg atoms strongly correlates with mol% MgCO3. Even in early diagenetic, non‐stoichiometric dolomites, there is little substitution of Mg in Ca sites. During recrystallization, the amount of Mg substituting for Ca in Ca sites decreases even further. Most of the disorder in the least recrystallized, non‐stoichiometric dolomites is related to substitution of excess Ca on Mg sites.