bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sediment geometries and domino faulting
Authors: Waltham David , Hardy Stuart , Abousetta Abdulnaser 
Published: April 2008

Abstract
A general forward modelling scheme is used to produce a model of sediment geometry in half-grabens formed during extension of domino fault blocks. The model includes the effects of erosion, sediment transport, sedimentation and isostasy and simulates both syn- and post-rift sedimentary sequences. The geometries and relationships produced by the model are broadly similar to natural examples seen on North Sea seismic sections. This similarity is emphasized by the generation of synthetic seismic data using the numerically modelled geometry as a template. The unconformable nature of the boundary between syn- and post-rift seismic sequences is clearly visible on the synthetic data in the region of the fault block crest.
Relationships between thrust tectonics and sequence stratigraphy surfaces in foredeeps: model and examples from the Pyrenees (Cretaceous-Eocene, France, Spain)
Authors: Deramond Joachim , Souquet Pierre , Fondecave-Wallez Marie-José , Specht Martin 
Published: April 2008

Abstract
A new method of chronological and geometrical analysis is used for understanding the sedimentary and tectonic evolution of perisutural basins (foredeep and foreland basins). It may be applied to synorogenic basins whose infilling was controlled by sea-level fluctuations and where, as a result, the tectonic structures are well preserved. This method is based on the mapping of depositional sequence boundaries and maximum flooding surfaces defined by sequence stratigraphy. These planar markers are considered as synchronous and their numerical ages are determined by classical chronostratigraphic methods, by dating and by comparison with the eustatic global cycle chart.
The evolution of the studied perisutural basins is controlled by the propagation in space and time of a syn-depositional thrust-and-fold system including a fault-propagation anticline and two synclines (a foreland and a hinterland syncline) over and in front of a blind basal sole thrust. The propagation of this thrust-and-fold system toward the foreland is connected to unconformable depositional sequence sets, which indicate for each system a time span for thrusting of several eustatic cycles.
The evolution of a single thrust-and-fold system corresponds to a shortening accommodated by upward imbrication of second-order thrusts inside the anticline. Each of these thrusts is related, at least, to one depositional sequence lying unconformably on the external side of the fold and deformed by the successive development of the branch lines toward the hinterland. This tectono-sedimentary correlation indicates a time span sometimes as short as one eustatic cycle for each second-order thrust.
Thrusting and sea-level changes are not exactly synchronous, as the depositional sequence sets (which are tectonic in origin) do not systematically correlate with eustatic supercycles. The apparent time correlation between the two groups of independent phenomena is an artefact of the method which calibrates the tectonic evolution by comparison with eustatic fluctuations.
Applied to the South Central Pyrenees, the method has specified the structure of the Late Cretaceous foredeep basin and has revealed the successive stages of forward thrust-and-fold system migration (4 to 5 Ma for each one from 89 Ma) and of hindward second-order thrust migration (1 to 4 Ma for each one).
In the North Central Pyrenees as in the South Central Pyrenees, Late Cretaceous foredeeps are characterized by syntectonic turbidite deposits (from 89 Ma onward) and by a significant shortening due to a symmetrical and synchronous structural evolution. The Eocene foreland is a foreland syncline developed in the footwall of the North Pyrenean Thrust. This syncline is due to the occurrence of blind thrusts and it is infilled by fluvial deposits.
Luminescence dating of sand from the Kelso Dunes, California
Authors: Edwards Stephen R. 
Published: April 2008

Abstract
A relatively new luminescence dating technique, infra-red stimulated luminescence (IRSL), has been used to date dune sand from the Kelso Dunes, eastern Mojave Desert, California. This is the first time the technique has been applied to desert aeolian sands. The IRSL technique measures the time since sediment grains were last exposed to light, by sampling a highly light-sensitive signal which reduces rapidly to a negligible level when so exposed. The technique can be used to date very young samples. Of the ten samples dated, the surface sample gave an age of 40 ± 17 years, while subsurface samples gave high-precision middle and late Holocene dates. These results, obtained from the upper 8 m of the sand mass, indicate significant aeolian activity during the later part of the Holocene. Clustering of IRSL ages from the data so far available suggests that the aeolian activity may have been episodic.
Climbing and falling sand dunes in Finnish Lapland
Authors: Seppälä Matti 
Published: April 2008

Abstract
This paper presents the first description of climbing and falling sand dunes from Finnish Lapland. They are located on the slopes of a glaciated valley containing an esker. The largest climbing dune is 1800 m long and 2–5 m high. The slope of the fell dips 7 degrees on average. The material comprising the dune is typical aeolian sand with a median grain size about 0.23 mm but not very well sorted. The dunes were formed just after deglaciation under periglacial conditions.
Outcrop data-base for the geological characterization of fluvial reservoirs: an example from distal fluvial fan deposits in the Loranca Basin, Spain
Authors: Cuevas Gozalo M. C. , Martinius A. W. 
Published: April 2008

Abstract
Sedimentological data for stochastic modelling purposes consist both of qualitative and of ‘hard’ numerical data from reservoir-equivalent outcrops. Data requirements are defined prior to collection of the actual field data-base, and standard procedures for the collection and classification of these data are established. Required data are on individual sandbodies, such as genetic type, geometry, palaeoflow and size; and on the 2D and 3D sedimentary architecture (spatial distribution, interconnectedness).
Validity of the data-requirement definition, and feasibility of data acquisition for specific stochastic modelling purposes, were tested in reservoir-equivalent outcrops of distal fluvial fan deposits of Tertiary age in the Loranca Basin in central Spain. Several sandbody genetic types were recognized: meander-loop deposits, channel-fill deposits, crevasse-channel and crevasse-splay deposits and deltaic deposits. Statistical processing of the numerical outcrop data showed that meander-loop deposits are thicker, wider and present higher linearinterconnectedness values than channel-fill deposits.
Identification and significance of aeolian deposits within the dominantly fluvial Sherwood Sandstone Group of the East Irish Sea Basin UK
Authors: Cowan Greig 
Published: April 2008

Abstract
The Triassic Sherwood Sandstone Group sediments of the East Irish Sea Basin are over 4000 ft thick and comprise medium- to coarse-grained sandstones and rare thin mudstones. Facies models developed during production drilling on the South Morecambe Field show that deposition occurred in a braided fluvial setting with minor aeolian episodes. The major facies associations present are: (A) major channel fill; (B) ephemeral channel fill; (C) non-channelized sheetflood deposits; (D) and (E) non-reservoir fines (abandonment and playa respectively); (F) aeolian dune and sand-sheet. Volumetrically, the major channel (A) and sheetflood (C) facies dominate, and the alternation of these facies associations is correlatable across the field. The aeolian sandstones form units varying in thickness from a few grain diameters up to 3 m thick. The sand-sheet and dune deposits can be correlated over considerable distances and show pressure communication on RFT logs. Although the aeolian sandstones comprise only 5–10% of the reservoir they have very high porosities and permeabilities (up to 30% and 10 darcies) and make disproportionate contributions to flow into the wellbore. The depositional criteria used to differentiate between aeolian and fluvial deposition in the South Morecambe Field are pinstripe lamination, good sorting and lack of rounded clay clasts, but these criteria are not definitive. As a result of the dissolution of an early diagenetic cement, aeolian sandstones have very high porosities compared to fluvial sandstones. This high porosity is reflected in high sonic transit times and allows aeolian sandstones to be identified tentatively in uncored wells by use of sonic logs.
Modelling fluid flow through geologically realistic media
Authors: Lake L. W. , Malik M. A. 
Published: April 2008

Abstract
The most useful way to validate a predictive scheme is to compare its results against actual performance. While this approach has enjoyed some success, the interpretation of any reservoir process is complicated by many operational, reservoir and subjective issues. These issues mean that the process performance is rarely clear, and consequently the success of the prediction is always in doubt, no matter how closely the prediction agrees with performance. The work described in this paper adopts another means of validation: comparison of a highly detailed deterministic simulation against the results generated from conditional simulation (CS). Results show that, although it is highly flexible and generates realistic heterogeneity, CS must be tailored to the specific geological environment for best agreement with the deterministic simulation.
Preliminary Landsat lineament analysis of the northern Nanga Parbat-Haramosh Massif, northwest Himalaya
Authors: Cronin V. S. , Schurter G. J. , Sverdrup K. A. 
Published: April 2008

Abstract
Analysis of a mosaic of Landsat 2 MSS band 7 images covering the northern Nanga Parbat-Haramosh Massif (NPHM) has yielded approximately 540 lineaments, defined by sets of colinear drainage segments and aligned linear graytone boundaries. We recognized segments of the few well-mapped faults along the NPHM as lineaments. The paucity of field data concerning faults, joints, lithological fabric and contacts prevents us from interpreting most of the lineaments at this time. However, some of the prominent lineament trends probably mark the trace of previously unmapped active faults that accommodate the recent uplift of the NPHM. The origins of these lineaments must be established through structural geological field work.
Stratigraphy south of the Main Mantle Thrust, Lower Swat, Pakistan
Authors: Dipietro Joseph A. , Pogue Kevin R. , Lawrence Robert D. , Baig Mirza S. , Hussain Ahmad , Ahmad Irshad 
Published: April 2008

Abstract
The metamorphic sequence in Lower Swat is described and placed into the geological framework of Pakistan. The stratigraphic sequence consists of the Precambrian-Cambrian(?) Manglaur formation unconformably overlain by the Alpurai group which is subdivided into the Carboniferous or younger Marghazar formation, and the Triassic or younger Kashala, Saidu, and Nikanai Ghar formations. A third unit, the Jobra formation of unknown age, is present as discontinuous lenses unconformably below the Alpurai group. Type sections are indicated for each rock unit. Comparison with the stratigraphy in the Peshawar Basin indicates that the Lower Swat area existed as a highland with active normal faulting during and perhaps before deposition of the Marghazar formation. The Marghazar formation appears to be a rift facies that correlates with the Panjal Traps of western India. The Kashala and Nikanai Ghar formations represent a transition to a stable shelf environment. These units may correlate, in part, with the Zanskar Supergroup of western India. The Saidu formation may represent drowning of the shelf as it was pulled down and overridden by the Main Mantle Thrust suture melange. It may correlate with the Lamayuru Formation of western India. The Alpurai group thus records a depositional history from Late Paleozoic breakup of Gondwana, to development of a passive Mesozoic shelf, to drowning of the shelf at the onset of Himalayan orogeny.
Mechanisms of anabranch avulsion within gravel-bed braided rivers: observations from a scaled physical model
Authors: Leddy J. O. , Ashworth P. J. , Best J. L. 
Published: April 2008

Abstract

The physical modelling of gravel-bed braided rivers, using a 1:20 Froude scale model, permits analysis of the types and relative occurrence of different avulsion mechanisms. Anabranch avulsion within braided rivers involves three main mechanisms:
choking avulsion
caused by blockage of one channel by a sediment lobe,
constriction avulsion
produced by deflection, confinement and subsequent diversion of the flow by a barform and
apex avulsion
following erosion at the outside of sinuous thalwegs and confined meander bends. Each avulsion mechanism is described and analysis of the abundance of each type illustrates choking avulsion to be predominant without braided rivers. Three factors are found to control anabranch avulsions, namely flow discharge, sediment flux and floodplain topography. These are briefly discussed together with the implications of avulsion type for the alluvial architecture of gravelly braided alluvium.
Pleistocene Rhine gravel: deposits of a braided river system with dominant pool preservation
Authors: Siegenthaler Christoph , Huggenberger Peter 
Published: April 2008

Abstract
An example of a gravelly braided river deposit is described which exhibits a rather low structural diversity as compared to other ancient and modern braided river sediments. The presented model is based on a study of the Rhine gravel, formed in front of the Würm stage extension of the Rhine glacier (northern part of Switzerland). The observations in the Rhine gravel suggest that only processes which operate generally at a low topographic level of the braided river system generate a response in the geological record, i.e. (1) pool deposits produced at the junction of two channels (cross-bedded trough fills); (2) channel sediments which reflect thin bedload sheets deposited by moderate-magnitude flow stages with low suspension concentrations; (3) sheet flow deposits produced by extraordinary high-magnitude flow stages with high suspension concentrations, probably due to outbursts from glacial lakes.
Therefore, we postulate that in the Rhine gravel system only a limited number of braided river structures have a significant preservation potential: any deposit generated at an elevated geometric level, such as flood plain deposits or bars, are successively destroyed by channel formation and are replaced by channel deposits, which in turn may be reworked by pools which operate at the lowest geometric level. It is suggested that similar preservational hierarchies could eventually exist also in other braided river deposits.
The architecture of fluvial-deltaic sequences in the Upper Mesaverde Group (Upper Cretaceous), Book Cliffs, Utah
Authors: Miall Andrew D. 
Published: April 2008

Abstract
The Mesaverde Group is a clastic wedge that prograded eastward into the Western Interior Basin from the Sevier Orogen of central Utah during the Late Cretaceous. The Blackhawk Formation and the overlying Castlegate Sandstone represent tongues of fluvial-deltaic and shoreface strata that prograded far into the basin in response to pulses of tectonism.
The Desert Member of the Blackhawk Formation includes two fourth-order stratigraphic sequences and the Castlegate Sandstone represents the lower part of a third sequence. The upper two sequences begin with regional erosion surfaces, above which widespread fluvial blankets represent backfill deposits formed during periods of relative base-level rise. Transgressive and highstand deposits are poorly represented at the top of the Blackhawk Formation, having probably been removed by erosion prior to Castlegate sedimentation. The overriding tectonic control of this fluvial-deltaic wedge is demonstrated by regional changes in paleoslope and detrital sources. However, the sequence architecture indicates that this regional tectonism was modulated by short-term base-level changes, of tectonic or eustatic origin.
Architectural-element analysis of the fluvial units indicates deposition predominantly by large bars (macroforms) in braided river systems. The bars developed by lateral, oblique and downstream accretion. They combine laterally and vertically to form widespread sandstone sheets typically capped by thin mudstones and bounded by flat erosion surfaces. The sheets and their component bars thicken from an average of 4–6 m in the Price area to 6–9 m east of Green River, 140 km down palaeoslope, probably as a result of tributary amalgamation and consequent deepening of the river system. In the subsurface such sheets would define flow units for production purposes. However, they are not internally homogeneous, consisting of bar sandstones <400 m in lateral dimensions, and bar increments and small channels >120 m long and wide. Many of these heterogeneities are bounded by mudstone units, and contain dipping accretion surfaces which could act as baffles to lateral fluid movement.
The interaction and geometries of diapiric uprise centres along mid-ocean ridges — evidence from mantle fabric studies of ophiolite complexes
Authors: Bartholomew I. D. 
Published: April 2008

Abstract
Detailed structural mapping and thin-section fabric studies of oceanic upper mantle sections exposed within 3 ophiolite complexes have shown that in all of the ophiolites studied two co-existing high-temperature mantle fabric orientations can be identified. The fabrics are related both in time and space in that one fabric is ductile shear-folded by a later one to varying degrees. Olivine and orthopyroxene crystal slip-system and fabric orientation studies show that all the fabrics identified are high-temperature ‘primary’ asthenospheric flow fabrics and that simple shearing is the main flow process. The fabrics observed are at varying angles to the orientation of the Moho plane, with the slip directions varying both along strike with the Moho as well as vertically down from the Moho plane.
The identified flow fabrics are considered to be indicative of mantle flow directions ‘frozen’ into the mantle as it cooled from being ductile asthenosphere to lithosphere. Each fabric is interpreted as originating from a different localized mantle diapiric uprise centre. The centres interact with each other both in space and time, the observable ‘frozen’ fabrics indicating the closeness and ‘strength’ of individual diapirs relative to the position of the data measurement point.
Trace element models for mantle melting: application to volcanic arc petrogenesis
Authors: Pearce Julian A. , Parkinson Ian J. 
Published: April 2008

Abstract
Understanding mantle melting above subduction zones requires an evaluation of the behaviour of elements for which the mantle contribution greatly exceeds any subduction contribution. In this paper we present a compilation of partition coefficients for a suite of these elements (Nb, Zr, Y, Yb, Ca, Al, Ga, V, Sc, Fe, Mn, Co, Cr, Mg, Ni) for temperatures of 1200–1300°C, oxygen fugacities of QFM ± 1 and sub-alkaline compositions. These coefficients yield good-fit mantle depletion trends for abyssal, orogenic and trench-wall peridotites. Modelling of pooled melts from mantle melting columns, presented as FMM (fertile MORB mantle) normalized patterns, give signatures of the composition and degree of melting of the mantle wedge that are generally independent of the subduction component. In particular, patterns formed from melting of fertile mantle exhibit normalized element abundances in the order VHI > HI > MI (VHI = very highly incompatible, HI = highly incompatible and MI = moderately incompatible) at low degrees of melting, becoming VHI = HI = MI at high degrees of melting. With derivation from progressively depleted sources, the patterns for moderate degrees of melting change to VHI < HI = MI at moderate degrees of depletion and VHI < HI < MI at high degrees of depletion.
The details, but not the principles, can be varied by changing the shape of the melting column, the porosity of the mantle during melting, the potential temperature of the mantle, and the temperature and depth of initiation of melting. Bivariate plots of elements of contrasting compatibilities (Cr-Yb, Sc-Yb, Nb-Yb) can be contoured according to the degree of depletion or enrichment of the mantle and the degree of melting, with selected plots also emphasizing the role of garnet (Ti-Yb) and oxygen fugacity (V-Yb). Evaluation of data from present-day volcanic arcs suggests that: (1) intra-oceanic arcs with associated active backarc basins are derived principally from fertile MORB mantle that has lost up to about 3% melt in a previous melting event; (2) this depletion takes place in spinel lherzolite facies, supporting models that relate it to backarc basin melting events; (3) oceanic arcs with no associated backarc basins are derived principally from fertile MORB mantle, though enriched sources can be important locally; (4) intra-continental arcs are commonly derived from enriched mantle, probably because of the involvement of sub-continental lithosphere; (5) degrees of melting are probably high (in the order of 25–30%) in intra-oceanic arcs on thin crust, decreasing to 150r less in areas of thicker lithosphere; (6) some 10% melting can be explained by volatile addition to the mantle, the remainder by decompression.
The water inventory of the Earth: fluids and tectonics
Authors: Fyfe W.S. 
Published: April 2008

Abstract
As the human population continues to expand, to approach ten billion, there will be an increasing demand upon all Earth’s resources. Of particular importance will be resources related to energy, soil and water, all of which involve geofluids. Problems associated with waste disposal also involve systems for protecting near-surface water quality. There is an urgent need to quantify the fluid inventory and fluid dynamics of the near surface, while understanding volatiles and their deep recycling is fundamental to our understanding of the major dynamic processes of the Earth.
The nature of metamorphic fluids and significance for metal exploration
Authors: Phillips G. Neil , Williams Patrick J. , De Jong Geoffrey 
Published: April 2008

Abstract

Fluids are active at all levels in the crust during metamorphism. Devolatilization of many rock packages leads to the evolution of H
2
O, CO
2
and/or S as a fluid phase that is commonly of low salinity. The composition of the fluid phase released during devolatilization is controlled by the dominant mineral assemblage in the source region, and the evolution of such fluid is most dramatic where major changes in modal mineralogy occur; e.g. across metamorphic facies boundaries. Evidence for this loss of volatiles during metamorphism is provided by metamorphic assemblages that typically contain less volatile components as grade increases.

The metamorphism of mafic rock successions can yield a metamorphic fluid rich in H
2
O, CO
2
and S, and close in composition to fluids inferred in the formation of many gold-only deposits. The close affinity between gold and these fluids arises from the stability of the Au-S complexing.

Where evaporites are present in the succession, the fluids released during devolatilization can be quite saline. A further potential source of saline fluids in these environments is from crystallization of certain magmas. Saline fluids have a composition favourable for transporting gold
and
base metals, which is likely to explain the occurrence of gold as a co-product in many deposits where saline fluids are inferred.

The contrast between saline and low salinity fluids during metamorphism is not only reflected in ore metals, but also in the associated alteration and element mobility. Only a few elements are mobile in the low salinity fluids, and the alteration mineralogy is strongly influenced by the nature of the host rocks. Saline fluids readily transport many elements, and a similar alteration assemblage can be superimposed on many different precursors.