bluuebunny/crossref_metadata_2025_split huggingface dataset:
Natural constraints on metamorphic reaction rates
Authors: Baxter Ethan F. 
Published: April 2008

Abstract

Quantitative constraints on the rates at which metamorphic reactions proceed in nature are now available from several sources. Most common are predictions made on the basis of laboratory kinetic data. However, the applicability of such laboratory-based predictions has long been questioned and many observations in the field now suggest much slower rates. Here, published quantitative field-based constraints on high temperature (>400 °C) reaction rates are assembled from a variety of sources. Reaction rates attending regional metamorphism are four to seven orders of magnitude slower than most laboratory-based predictions. A general rate law for
regional
metamorphism has been derived which best describes these field-based data:

log
10

(

R
net

)
≅
0.0029
T
−
9.6
±
1

where
R
net
is the net reaction rate (g/cm
2
/a) and
T
is temperature (°C). At the same time, natural reaction rates attending contact metamorphism differ from laboratory-based predictions by less than two orders of magnitude, and are in close agreement at higher temperatures. Thus, while existing laboratory-based kinetic data may be judiciously applied to some contact metamorphic systems, laboratory-based kinetic predictions clearly misrepresent regional metamorphism. To explain this kinetic discrepancy, regional metamorphic reaction rates may be limited by slow intergranular transport due to comparatively limited (or transient) availability of aqueous fluid in the intergranular medium. The general field-based rate law may be applied to regional metamorphic, and other environments (i.e. ultrahigh pressure or ultrahigh temperature metamorphism), if similar system characteristics (mainly, low aqueous fluid content) can be inferred.
Prograde and retrograde reactions, garnet zoning patterns, and accessory phase behaviour in SW Finland migmatites, with implications for geochronology
Authors: Nyström Annika I. , Kriegsman Leo M. 
Published: April 2008

Abstract
Rates of melt production and segregation in migmatites can be assessed using geochronology of accessory phases. Here we report on the distribution and growth patterns of accessory phases and their coupling with major phase microtextures and chemical zoning patterns in garnet. We propose that migmatization in SW Finland involved partial melting and subsequent moderate retrograde re-equilibration. The latter process has three major effects: (i) it partially obscures geochemical signatures formed during earlier equilibrium or disequilibrium melting; (ii) it excludes the possibility of very fast (< 100 years per batch) melt segregation rates in migmatites where restite-melt back reaction has operated; (iii) trace element distributions between leucosome and host rock cannot be used to infer melt segregation rates.
Garnet MnO patterns show flat cores, suggesting high-grade equilibration, and sharply increasing concentrations at the rims, attributed to garnet-melt back reaction. Trace element patterns (Zr, Y and heavy rare earth elements) also document retrogression at the rims, but in addition preserve earlier growth zoning related to incongruent melting. We report retrograde zircon and xenotime growth associated with garnet resorption, here related to restite-melt back reaction in leucosome, melanosome and mesosome. Hence, geochronological studies of migmatite terranes should take into account that the youngest zircon material is not restricted to leucosome, but can also form overgrowths on corroded grains in melanosome and mesosome.
Remembrance of things past: a hike along the Grès d’Annot research trail
Authors: Stanley Jean-Daniel 
Published: April 2008

Abstract

This brief
aperçu
recalls some keynote studies on the Grés d’Annot in the French Maritime Alps that paved the way for my involvement with these rocks in the late 1950s. At that time, the topic of gravitative flows was gaining momentum, and various theories on underwater avalanches, including turbidity currents capable of carrying coarse sand to the deep sea, had already been proposed. However, these transport processes still needed considerable clarification. Discoveries, including the identification of the sandstones as turbidites by Faure-Muret and others in 1956, were not conceived in a vacuum, but rested on many years of previous research by numerous geologists. Some of the key earlier findings are cited here. My interests then, and for several decades afterward, were focused on the broader context of sedimentary petrology, downslope-to-deep marine deposition, palaeogeography and regional structural geology pertaining to these spectacular Tertiary sequences. Now that more than 40 years have passed, I look back and can better appreciate the role of others and their influence serving as a base for my modest effort. The ‘cutting of teeth’ experiences on the Grés d’Annot were truly fortunate, not only for my early formation as a sedimentologist, but also as I have continued to pursue related and progressively more diverse activities.
The structural setting and palaeogeographical evolution of the Grès d’Annot Basin
Authors: Apps Gillian , Peel Frank , Elliott Trevor 
Published: April 2008

Abstract
A new kinematic model is derived for part of Haute Provence, which recognizes that Alpine deformation, involving both the Mesozoic and sub-Mesozoic section, has been active since the onset of Tertiary deposition. This model places the Grès d’Annot basin in an overall compressional setting, dominated by SW-directed Alpine thrusting, during deposition of the Tertiary basin fill sequence. Evidence is presented that one block of Palaeozoic material (Barrot) was strongly uplifted and deeply eroded prior to the onset of Tertiary deposition in the area. Local thin-skinned extension and strike-slip are observed, but these are secondary components, which are interpreted to be part of the overall thrust system. The region was affected by three different orogenic events. Pyreneo-Provençale thrusting established a structural fabric that influenced later, syndepositional thrust geometries. The Late Eocene to Early Oligocene Grès d’Annot Basin was a structured foreland basin created by the loading effects of the Alpine orogeny. The supply of siliciclastic sediment to the basin was controlled by tectonic events far to the south, in a subduction-related orogeny that extended from East Iberia to SE France. SW-directed Alpine compression within the basin produced significant basin-floor topography, which developed immediately prior to, and during, the Nummulitic transgression. The evolving palaeo-relief of the basin is recorded in thickness and facies variations of the older Tertiary lithostratigraphical units (Poudingues d’Argens, Calcaires Nummulitiques and Marnes Bleues), and by the onlap geometry of the Grès d’Annot turbidites. This allows us to define a set of palaeogeographical maps of the basin throughout its evolution, linked to a set of sequentially restored structural sections. This basin floor topography was complex, because Alpine thrusting overlapped the older east-west striking structures, and it created a set of partially isolated sub-basins. Major early compressional structures partitioned the basin, exerting strong control on all the Tertiary depositional systems, including the Grès d’Annot turbidite systems.
The southern Grès d’Annot outcrops (French Alps): an attempt at regional correlation
Authors: Du Fornel E. , Joseph P. , Desaubliaux G. , Eschard R. , Guillocheau F. , Lerat O. , Muller C. , Ravenne C. , Sztràkos K. 
Published: April 2008

Abstract
During Eocene-Oligocene times, the Grès d’Annot turbidite system (French Alps) was deposited in several tectonically controlled sub-basins, which were mainly fed from a southern major sediment source: the Corsica-Sardinia Massif. In order to establish regional correlations in the southern part of the basin, four kilometre-scale outcrop areas were studied in detail. From south to north these are: the St Antonin, Annot, Grand Coyer and Chalufy areas. The results are: (1) an updated chronostratigraphic framework, (2) a major SE-NW correlation panel, approximately 400m thick and 50 km long, parallel to palaeocurrent directions, within which all stratigraphic units are defined in terms of sedimentology and micropalaeontology and (3) some correlation panels at outcrop scale (around 5 km long and several hundred metres thick), within which all stratigraphic units are defined as before, but with the addition of a direct visual control on correlations, which enables the reconstruction of higher resolution geometry. Seven time-equivalent stratigraphic packages have been correlated from upstream to downstream, making use of micropalaeontologic constraints, and their geometric and facies evolution have been reconstructed through times. This evolution may be related to different stages in the basin deformation, induced by the east to west development of the Alpine foreland basin.
Genetic units/parasequences of the Annot turbidite system, SE France
Authors: Guillocheau François , Quéméner Jean-Marie , Robin Cécile , Joseph Philippe , Broucke Olivier 
Published: April 2008

Abstract
High-frequency cycles (genetic units or parasequences), with a mean duration of 20000 years, have been identified in the Grè d’Annot turbidite system of the southern Alpine foreland basin (Late Eocene/Early Oligocene). They filled a narrow (2–8 km wide) synsedimentary syncline that formed a confined basin fed upward by a fan-delta located on a narrow shelf. These cycles are 10m thick, and each consists of a basal heterolithic component and an upper sandy homolithic unit, traceable over at least 10 km. They result from the superposition of (1) a progradational phase with an accretionary system (low-angle accretionary bedsets) and a feeder system (by-pass to high preservation oblique laminasets) and (2) an aggradational phase with a ‘spread’ system overlain by a condensed interval. The progradational phase shows very low-angle clinoforms (low-angle accretionary sets, 1–2 m high, a few tens to a few hundreds of metres long) fed by erosional structures (channels or large scours, 0.2–2 m deep, a few metres to a few tens of metres wide). The aggradational phase (subplanar laminasets, ‘scour and fill’ structures) forms a ramp, and drapes the underlying sediments. These progradational geometries may be explained by the narrow sub-basin morphology and by the transition from channelled flow (updip narrow part) to unconfined flow (downdip wider part). These genetic units directly record the variations in sedimentation rate of the feeding fan-delta on the shelf, which are controlled by the 20 000 year cycles of sea-level change.
Deep-water sedimentation on an evolving fault-block: the Braux and St Benoit outcrops of the Grès d’Annot
Authors: Tomasso Mark , Sinclair Hugh D. 
Published: April 2008

Abstract
The record of sediment fill contained in sub-basins of the western outcrops of the Grès d’Annot indicates that, throughout the period of deposition of the sandstones, there was very little synsedimentary tectonic activity. However, evidence of syntectonic sedimentation is preserved in the basal portion of the fill of the Annot sub-basin. The lowermost portions of the turbidite infill of the Annot sub-basin crop out around Braux and St Benoit. These outcrops are separated by the St Benoit Fault, which is thought to have developed as a result of sinistral strike-slip movement on the main Rouaine Fault to the south. The St Benoit Fault has a normal offset of up to 400 m to the east. Detailed mapping within the Calcaires Nummulitiques, Marnes Bleues and Grès d’Annot, has led to the recognition of several features that indicate a syntectonic sedimentary evolution for the outcrops. These record a three-phase progressive evolution of the St Benoit Fault through the upper Calcaires Nummulitiques to the lowermost Grès d’Annot. As part of this, there are implications for deposition from turbidity currents on encountering topographic barriers. To our knowledge, this area contains one of the few outcrop examples of half-graben formation within the confined basins of the Grès d’Annot.
The Marnes Brunes Inférieures in the Grand Coyer remnant: characteristics, structure and relationship to the Grès d’Annot
Authors: Stanbrook David A. , Clark Julian D. 
Published: April 2008

Abstract
Part of the Alpine foreland basin, the Grand Coyer remnant lies in a NW-SE-trending syncline and contains turbidity current deposits derived from the south. Palaeotopography of the Marnes Bleues surface is complex but there is generally a NE-dipping confining slope in the west of the area. Palaeocurrent data suggest that aside from localized alteration of flow paths, the mean direction of flow was parallel to this slope. Three sections (Vallon de Fouès & Carton, Laupon and Sommet de la Mole) are used to illustrate the nature of the Marnes Brunes Inférieures—a transitional facies between the Marnes Bleues and the Grès d’Annot. The Marnes Brunes Inférieures is typically thin-bedded, sharp-based and sharp-topped, non-graded, predominantly very fine-grained sands, with planar and ripple lamination, interbedded with thin marls and shale. The finer grained Marnes Brunes Inférieures in the Grand Coyer area is interpreted as a distal and lateral equivalent of the coarser Grès d’Annot, which is generally thought to represent deposition along the main axis of flow. Examples are provided of how these characteristics change away from the onlap slope. Evidence is presented to illustrate the connection between syndepositional structural alteration and the common slumping observed within the Marnes Brunes Inférieures.
Three-dimensional full wave seismic modelling versus one-dimensional convolution: the seismic appearance of the Grès d’Annot turbidite system
Authors: Bourgeois Aline , Joseph Philippe , Lecomte Jean Claude 
Published: April 2008

Abstract
The increasing use of three-dimensional seismic data for reservoir characterization justifies the need for an accurate and fast seismic modelling tool. Synthetic seismic data sets, where the geological model is controlled at each location, provide crucial information for the understanding of the seismic response in connection with various geological features. The method used here involves a wave equation approximation based on ray tracing and Born formalism in the context of a one-dimensional background, thereby providing economic computation of a very useful subset of geological models. The software enables a high level of flexibility to be applied to a range of realistic experiments. In particular the software provides pre-stack multi-component seismic response of a three-dimensional heterogeneous reservoir, including both reflected and converted waves, at the level of the target. In order to analyse and reconstruct the architecture of deep-water gravity deposits, we present a realistic synthetic seismic experiment of one Grès d’Annot outcrop. A geological interpretation of the outcrop has been based on photo panoramas calibrated with vertical sedimentological sections. The internal distribution of facies has been interpolated using geostatistical simulation, with one of the stochastic realizations of the reservoir architecture serving as the three-dimensional cube of lithofacies corresponding to the reservoir model. These lithofacies were assigned elastic parameters of an analogue Brazilian field. The reservoir model is then buried within a smooth background model, and a seismic model generated. The purpose of generating three-dimensional seismic models is to analyse the seismic signature of the different sedimentary architectures, in order to provide guidelines for the seismic interpretation of comparable subsurface reservoirs. Compared with convolution results, the computed synthetic data are more realistic and closer to the actual seismic data. This is mainly due to the fact that the method takes into account the lateral heterogeneity included in the vicinity of each reflecting point.
Silled sub-basins to connected tortuous corridors: sediment distribution systems on topographically complex sub-aqueous slopes
Authors: Smith Ru 
Published: April 2008

Abstract

Two end-member classes of sediment distribution systems on topographically complex slopes are distinguished here: (a)
cascades of silled sub-basins
, and (b)
connected tortuous corridors
. In the first scenario a process of filling and spilling of successive silled sub-basins down a slope occurs. For each sub-basin a sill tends to hinder further downslope flow of at least the basal sandy portions of sediment gravity flows until deposition reduces the relief sufficiently to allow spill down-slope. Spill is associated with incision in the sill. In the
connected tortuous corridors
scenario, flows avoid bathymetric obstacles, but follow a (laterally confined) continuous tortuous path down the slope. Without complete three-dimensional imaging of slope architecture it can be possible to incorrectly infer from two-dimensional profiles a
cascade of silled sub-basins
model. Thus flow paths in adjacent apparent subbasins can be connected out of the plane of section. Convergent thinning and convergent baselap stratal patterns occur in both scenarios, but only in the silled sub-basin case do such patterns occur against closing frontal slopes. For a given complex slope morphology, dominant controls on fill patterns and reservoir architecture are (a) the history of sediment supply character, and (b) rates of structure growth relative to rates of smoothing of topography by erosional and depositional processes. Two particularly important aspects of sediment supply are (i) flow volumes relative to scales of receiving spaces, and (ii) flow properties (in particular, transported grain size distribution, flow thickness and flow concentration), these controlling depositional gradients and the equilibrium profiles to which slopes tend to grade.
Factors influencing the deposit geometry of experimental turbidity currents: implications for sand-body architecture in confined basins
Authors: Al Ja’Aidi Omar S. , McCaffrey William D. , Kneller Benjamin C. 
Published: April 2008

Abstract
Two sets of scaled laboratory experiments were performed to examine the effect of flow volume, flow density and grain-size distribution on the transport efficiency of turbidity currents. The experiments employed two sediment analogues (ballotini and silica flour) intended to model medium- to coarse-grained sand and mud respectively. In the first set of experiments each parameter was varied to examine its effect upon deposit geometry. Increases in the initial flow density, volume and proportion of fines had the effect of increasing the amount of sediment that was transferred to the floor of the experimental tank by the turbidity currents. Increase of each of these parameters has a characteristic effect on the three-dimensional geometry of the deposit: the deposits of large-volume flows are elongate, and those of fines-rich flows are broad. Increase of flow density increases the initial potential energy of the flow, thus increasing the runout distance; increase of the initial density beyond a sediment concentration of 13% by mass results, however, in a reverse of the geometrical trend of deposit elongation, possibly because of turbulence suppression at high densities. Increase of flow volume also increases the initial potential energy, and reduces the rate of velocity decrease due to gravitational spreading. Increase in the proportion of fines leads to maintenance of negative buoyancy, as the fine fraction remains suspended until the flow has virtually come to rest; it also decreases the settling velocity of the coarser fraction and thus delays its sedimentation. The second set of experiments was performed to investigate the influence of flow efficiency on the interaction of turbidity currents with topography. A single arcuate obstacle was placed in the path of the flows. In successive experiments flow efficiency was increased by progressively increasing the proportion of fines (silica flour). Both the proportion of sediment reaching the obstructing topography and the proportion of it able to surmount the topography increased as flow efficiency increased. Thus flow efficiency may determine whether or not an enclosed basin hosts deposits whose geometry has been affected by the confinement, and may also determine the relative effectiveness of the topography in confining inbound turbidity currents, and thus trapping their sediment load.
Impact of syndepositional faulting on gravity current behaviour and deep-water stratigraphy: Tabernas-Sorbas Basin, SE Spain
Authors: Hodgson David M. , Haughton Peter D. W. 
Published: April 2008

Abstract
Seabed faulting can have a significant impact on the routeing and behaviour of gravity currents depositing sand on deepwater basin floors. The Neogene El Cautivo Fault in the Tabernas-Sorbas Basin, SE Spain, is a rare example of a fault that demonstrably propagated through to the seabed during turbidite deposition, allowing the interplay between deepwater sedimentation and tectonics to be explored. The fault is associated with a wide (up to 350 m) gouge zone that varies significantly in thickness along its length, reflecting upward expansion towards the original seabed and progressive burial as fault activity ceased. Kinematic and stratigraphic evidence indicate that the fault was a dextral oblique strike-slip fault that accommodated an area of deeper ponded bathymetry (a ‘mini-basin’) and accelerated subsidence on its southern flank. Active faulting controlled the routeing of turbidity currents (revealed by changing provenance across the structure), rates of seabed deformation (resulting in differential subsidence and ‘growth’ of the stratigraphy), and the behaviour of the ponded currents (producing distinctive bipartite beds when deposition was in localized ponded depressions). The seabed expression of the fault varied from a forced fold, which warped the surface causing local wedging and onlap in the vicinity of the structure, and an unstable scarp that locally collapsed. The fault gouge fabrics and vein arrays are consistent with faulting of soft, water-rich sediment close to the seabed.
Down-channel variations in stratal patterns within a conglomeratic, deepwater fan feeder system (Miocene, Adana Basin, Southern Turkey)
Authors: Satur N. , Cronin B. , Hurst A. , Kelling G. , Gürbüz K. 
Published: April 2008

Abstract
The proximal, channelized section of a deepwater fan in the Adana Basin, southern Turkey, provides an opportunity to study down-channel changes in stratal patterns. This is a multisourced, bypass fan with at least four feeder channels. The downdip changes within one of these channels are described along a 10 km transect. Down-channel changes in grading and organization of clasts are observed for non-grading disorganized facies in the most proximal locations to more organized, inverse-normal and normal graded conglomerates midway down the transect. Bedding style changes from scoured and more sheet-like beds updip into a pattern of small channels and bars midway along the transect, and into thick-bedded and structureless conglomerates in the more distal locations within the channel. These changes in stratal patterns coincide with observed changes in depositional gradient of the channel. The gradient changes are interpreted to be a contributing factor in controlling hydrodynamics within the gravity flows and thus the depositional stratal patterns.