Mass Flow Processes Research Articles

Pre-1.94 to post-1.88 Ga sediment depositional environment and c. 1.94 Ga felsic magmatism in the Knaften area, northern Sweden

ABSTRACTThe Knaften area is situated in the northern part of the Bothnian Basin in the central Svecofennian province of Sweden. Sedimentary rocks are here conformably intercalated with mafic to intermediate volcanic rocks. The depositional environment in the south-eastern part of the Knaften area was syn-orogenic deep water where tectonic activity caused volcanism and faulting. Mass flow processes transported material down slope and formed turbidites and debris flow deposits. Later, two phases of deformation affected the supracrustal rocks. Detrital zircons in a turbiditic sedimentary rock gave ages between 2.07 and 1.88 Ga, and between 2.93 and 2.62 Ga, indicating a substantial Archean component. The 1.88 Ga maximum depositional age is coeval with those of other supracrustal successions in the region, e.g., the mainly sedimentary Härnö and Vargfors groups, as well as the mainly volcanic Skellefte and Arvidsjaur groups. Zircons in the Knaften granite and the Knaften porphyry dyke have U-Pb ages of 1939 ± 3 Ma and 1939 ± 4 Ma, respectively. They confirm previously poorly constrained 1.95–1.94 Ga ages for these rocks. The intrusions cross-cut the mafic to intermediate volcanic rocks that, by consequence, must be older than 1.94 Ga. The new zircon data thus point to an age difference of about 50 to 60 million years between the felsic magmatism and the deposition of the dated turbiditic sediments. The oldest volcanic rocks (pre-1.94 Ga) in the Knaften area are evidence of at least one additional depositional stage in the Svecofennian tectonic evolution.

Assessing Ground Penetrating Radar's Ability to Image Subsurface Characteristics of Icy Debris Fans in Alaska and New Zealand

Icy debris fans have recently been described as fan shaped depositional landforms associated with (or formed during) deglaciation, however, the subsurface characteristics remain essentially undocumented. We used ground penetrating radar (GPR) to non-invasively investigate the subsurface characteristics of icy debris fans (IDFs) at McCarthy Glacier, Alaska, USA and at La Perouse Glacier, South Island of New Zealand. IDFs are largely unexplored paraglacial landforms in deglaciating alpine regions at the mouths of bedrock catchments between valley glaciers and icecaps. IDFs receive deposits of mainly ice and minor lithic material through different mass-flow processes, chiefly ice avalanche and to a lesser extent debris flow, slushflow, and rockfall. We report here on the GPR signal velocity observed from 15 different wide-angle reflection/refraction (WARR) soundings on the IDFs and on the McCarthy Glacier; the effect of GPR antenna orientation relative to subsurface reflections; the effect of spreading direction of the WARR soundings relative to topographic contour; observed differences between transverse electric (TE) and transverse magnetic (TM) antenna polarization; and a GPR profile extending from the McCarthy Glacier onto an IDF. Evaluation of the WARR soundings indicates that the IDF deposits have a GPR signal velocity that is similar to the underlying glacier, and that the antenna polarization and orientation did not prevent identification of GPR reflections. The GPR profile on the McCarthy Glacier indicates that the shallowest material is layered, decreases in thickness down fan, and has evidence of brittle failure planes (crevasses). The GPR profile and WARR soundings collected in 2013 indicate that the thickness of the McCarthy Glacier is 82 m in the approximate middle of the cirque and that the IDF deposits transition with depth into flowing glacial ice.

New evidence and interpretation of facies, provenance and geochemistry of late Triassic-early Cretaceous Tethyan deep-water passive margin-related sedimentary rocks (Ayios Photios Group), SW Cyprus in the context of eastern Mediterranean geodynamics

The late Triassic-early Cretaceous deep-sea sedimentary succession exposed in western Cyprus is used here to help understand the wider context of continental break-up and seafloor spreading in the easternmost Mediterranean region. The restored sequence begins with late Triassic, base-of-slope sandstone turbidites and mudrocks, and fines upwards into mudrocks, distal calciturbidites and metalliferous sediments. After a hiatus, late Jurassic-early Cretaceous non-calcareous mudstones and radiolarites accumulated beneath the carbonate compensation depth, together with redeposited shallow-water-derived carbonates, including calcirudites. The succession culminates in late Jurassic-early Cretaceous very thickly bedded and highly mature quartzarenites that accumulated by mass-flow processes. The fine-grained siliciclastic sediments are terrigenous in origin, as indicated by whole-rock, trace element and REE analysis. Fe, Mn and trace metal enrichment in the late Triassic represents hydrothermal input related to submarine volcanism that was probably triggered by the nearby onset of seafloor spreading. The late Triassic sandstones were derived from a low to intermediate-grade metamorphic source terrane. The late Jurassic-early Cretaceous sandstones reflect extreme physical and chemical maturity in the source area, followed by transport and mass flow to a deep-water base-of-slope setting. Regional facies variation and locally available palaeocurrent data suggest sediment supply, originally from a continental block, no more than tens of km to the west or north. Similar successions are exposed in W Turkey, represented by the Antalya Complex. In the light of alternatives, the sedimentary succession is restored as the base-of-slope apron of a rifted microcontinental block, adjacent to the northern margin of the S Neotethys. The overall succession indicates (unstable) passive margin development after regional latest Triassic-early Jurassic continental break-up, with implications for plate reconstructions and hydrocarbon exploration.

Heat and mass transfer characteristics of steam in a horizontal wellbore with multi-point injection technique considering wellbore stock liquid

In this paper, a novel model is proposed to study the variable mass flow process in a long horizontal well and to predict the distribution of thermophysical properties along the horizontal wellbore.First, a physical simulation device is designed to carry out a steam-injection experiment. Second, considering both the uneven distribution of steam and the effect of wellbore stock liquid, a steam-absorption model and a pressure drop model are proposed to predict the distribution of steam and pressure along the horizontal wellbore. Third, the effects of different parameters on steam distribution are analyzed in detail. The results indicate that: (1) an uneven employment phenomenon exists along the wellbore; (2) the pressure distribution along the wellbore is higher when wellbore stock liquid is taken into consideration; (3) the length of the unemployed section along the wellbore increases with an increase in the wellbore stock liquid viscosity; (4) the length of the unemployed section along the wellbore decreases with an increase in the steam injection rate; and (5) the reasonable wellbore length can prevent an unemployed section along the wellbore.This paper presents a basic reference for engineering for parameter optimization as well as for the prediction of steam distribution along the horizontal wellbore.

Carbonate production, accumulation and sea-level change in fault-block platform setting: a case study on the Albian sequences in Central Tunisia

The Albian series have been deposited on both sides of a major E–W paleogeographic fault, which was inherited in the early stages of the Tethyan-rifting phase. To the south of this fault, a shallow platform domain (footwall block or horst) occurred and is relayed northward by a slope-deep shelf setting (hanging wall block or graben). The platform to basin transition was analyzed northward of this fault nearby M’rhila Mountains. A detailed sedimentological study, coupled with a tectonic analysis, indicates that the Albian sedimentary deposits consist of four third-order depositional sequences. The three lower ones are only present in the deep-shelf setting and include substantial carbonate accumulations. The latter deposits are generally arranged into alternating mud-rich-bedded limestone and conglomeratic levels. Most of this material was exported from the adjacent shallow platform by mass flow and suspension transport processes. In the studied series, the maximum carbonate accumulation is recorded in the deep shelf during the moderate transgressive increasing and the late highstand decreasing rates of sea-level rise. However, the minimum carbonate sedimentation is thought to be linked to both the minimum lowstand and the maximum transgressive sea-level rise. The uppermost depositional sequence—which occurs on both sides of the major fault, is different from the three lower ones as it includes only scarce thin re-sedimented limestone beds. The youngest sequence is related to an important interplay between a pulse of tectonic subsidence and the major see level rise that happened during the upper Albian (100–98.9 Ma), resulting in a regional collapse of the substratum and the drowning of the carbonate factory situated southward. Therefore, the uppermost sequence is considered as a tectonically originated depositional sequence rather than a “pure” eustatic one. The organic-rich deposits associated to this sequence south and north of the major fault correlate well with the global anoxic events. The present study case represents a good example illustrating the role of local tectonics and global eustatic fluctuations in controlling not only the facies and thickness distribution but also the carbonate production and accumulation.

A 100-m.y.-long window onto mass-flow processes in the Patagonian Mesozoic subduction zone (Diego de Almagro Island, Chile)

Diego de Almagro Island was formed by the subduction and accretion of several seafloor-derived tectonic slices with very heterogeneous ages and pressure-temperature-time (P-T-t) paths. The highest element of the pile (the Lazaro unit) evidences subduction in the high-P granulite field (∼1.3 GPa, 750 °C) at ca. 163 Ma. Below it, a thin tectonic sliver (the Garnet Amphibolite unit) preserves eclogite-facies remnants (∼570 °C and ∼1.7 GPa) formed at ca. 131 Ma (in situ U-Pb zircon rim ages). Peak assemblages were nearly fully amphibolitized during decompression down to ∼1.2 GPa and ∼600 °C at 125–120 Ma (Rb-Sr multimineral dating). The underlying Blueschist unit has ∼50 m.y. younger metamorphic ages and exhibits slightly cooler peak burial conditions (∼520 °C, 1.7 GPa; ca. 80 Ma, in situ white mica Ar-Ar ages and multimineral Rb-Sr dating) and is devoid of amphibolitization. The mylonites from the sinistral strike-slip Seno Arcabuz shear zone bounding Diego de Almagro Island to the east also exhibit amphibolite-facies (∼620 °C and ∼0.9 GPa) deformation at ca. 117 Ma (multimineral Rb-Sr ages). In situ white mica Ar-Ar dating and multimineral Rb-Sr dating of low-T mylonites (∼450 °C) along the base of the Lazaro unit reveal partial resetting of high-T assemblages during tectonic displacement between 115 and 72 Ma and exhumation of the slice stack. Detrital zircon U-Th-Pb ages indicate that the material accreted on Diego de Almagro Island has been mostly recycled from a Permian–Triassic accretionary wedge (Madre de Dios accretionary complex) exposed along the subduction buttress. Geological and geochronological constraints suggest that the rocks of the Seno Arcabuz shear zone and the Lazaro unit were tectonically eroded from the buttress, while the underlying Garnet Amphibolite and Blueschist units instead derive from the subducted oceanic basin, with increasingly younger maximum depositional ages. The very long residence time of the rocks (∼90 m.y. for the Lazaro unit) along the hanging wall of the subduction interface recorded long-term cooling along the Patagonian subduction zone during the Mesozoic. Diego de Almagro Island therefore represents a unique window onto long-term tectonic processes such as subduction interface down-stepping, tectonic erosion, and episodic underplating near the base of an accretionary wedge (40–50 km).

Shallow marine to pelagic sediments from a dismembered ophiolite, Kandra, southern India – Glimpses of ancient subduction zone related sedimentation

A suprasubduction zone oceanic back-arc setting for the Paleoproterozoic Kandra ophiolite complex (KOC) in southern India has been suggested from geochemical signatures. The telescoped segments of thin deformed sedimentary successions of shallow marine to pelagic affinity, overlying a basaltic substrate and preserved within thrust slices of the KOC, are tectonically juxtaposed against the Eastern Dharwar craton margin. In the northern thrust slice (Kandra village succession), about 150m of sedimentary strata show intercalation of quartz arenite and basaltic flow in the lower part, grading upwards to heterolithic sandstone-mudstone deposited above the storm wave base. In the southeastern part of the KOC (Gurramkonda succession), deep-water greywacke turbidite, pelagic chert, mafic tuff and volcaniclastics, and quartz arenite deposited below the storm wave base, are preserved as thrust bound packets. Intermittent basaltic outpourings punctuated deeper water deposition as evidenced by alternate metachert and metabasalt layers, and emplacement of basaltic rocks along small thrusts which transpose stratification. Craton margin sediments consists of immature, coarse terrigenous clastics intercalated with thin mafic tuff, suggesting influence of mass flow processes giving way to fluvial sedimentation in the lower part of the Udaigiri Group. Further up, fine grained plane laminated siltstone-shale with rippled sandstone lenses grade upward to compositionally mature quartz arenite deposited close to the craton margin, with signatures of tidal- and wave reworking. The association of stratigraphic successions of two contrasting depositional environments in the KOC adds to the spectrum of variation of sedimentary collage of the ocean plate stratigraphy. The Kandra village and Gurramkonda successions of the KOC, possibly represent ancient arc-trench milieu, and shallower part of oceanic marginal basin respectively. Paleoproterozoic subduction-accretion process led to collapse of these basins and tectonic emplacement of the KOC against the Eastern Dharwar craton margin which hosted near shore sedimentary succession of the Udaigiri Group, occurring west of the KOC.

Sedimentology of Hirnantian glaciomarine deposits in the Balkan Terrane, western Bulgaria: Fixing a piece of the north peri-Gondwana jigsaw puzzle

Glaciomarine deposits of late Hirnantian age in the western part of the Palaeozoic Balkan Terrane have persistent thickness (~7m) and lateral uniformity in rock colour, bedding pattern, lithology, and sedimentary structures. Four lithofacies are distinguished from base to top: lonestone-bearing diamictites, interbedded structureless mudstones, crudely laminated diamictites, and finely laminated mudstones. The diamictites are clast-poor to clast-rich comprising muddy to sandy varieties. Their compositional maturity is evidenced by the very high amount of detrital quartz compared to the paucity of feldspar and unstable lithic grains. Other textural components include extraclasts derived from the local Ordovician basement, mudstone intraclasts, and sediment aggregates. Turbate structures, grain lineations, and soft sediment deformation of the matrix below larger grains are locally observed. Sedimentological analysis reveals that deposition occurred in an ice-intermediate to ice-distal, poorly agitated shelf environment by material supplied from meltwater buoyant plumes and rain-out from ice-rafted debris. Remobilization by mass-flow processes (cohesive debris flows and slumps) was an important mechanism particularly for the formation of massive diamictites. The glaciomarine deposits represent a typical deglaciation sequence reflecting retreat of the ice front (grounded or floating ice sheet), relative sea-level rise and gradually reduced sedimentation rate with increasing contribution from suspension fallout. This sequence was deposited on the non-glaciated shelf of the intracratonic North Gondwana platform along the southern margin of the Rheic Ocean. The Hirnantian strata of the Balkan Terrane can be correlated with similar glaciomarine deposits known from peri-Gondwana terranes elsewhere in Europe showing clear ‘Armorican affinity’. Several lines of evidence suggest that the provenance of siliciclastic material was associated mainly with sedimentary recycling of mature sands which had been deposited across North Gondwana in Cambrian and pre-glacial Ordovician times.

Sedimentology, depositional environments and significance of an Ediacaran salt‐withdrawal minibasin, Billy Springs Formation, Flinders Ranges, South Australia

AbstractThe late Ediacaran Billy Springs Formation is a little‐studied, mudstone‐dominated unit deposited in the Adelaide Rift Complex of South Australia. Sediments are exposed in an approximately 11 km × 15 km synclinal structure interpreted as a salt‐withdrawal minibasin. The stratigraphic succession is characterized by convolute‐laminated slump deposits, rhythmically laminated silty mudstones, rare diamictites and fining‐upward turbidite lithofacies. Lithofacies are the product of deposition in a deepwater slope or shelf setting, representing one of the few such examples preserved within the larger basin. Although exact correlations with other formations are unclear, the Billy Springs Formation probably represents the distal portion of a highstand systems tract, and is overlain by coarser sediments of the upper Pound Subgroup. Diamictite intervals are interpreted to be the product of mass flow processes originating from nearby emergent diapirs, in contrast to previous studies that suggest a glacial origin for extrabasinal clasts. Within the spectrum of outcropping minibasins around the world, the sediments described here are unique in their dominantly fine‐grained nature and overall lithological homogeneity. Exposures such as these provide an opportunity to better understand the sedimentological processes that operate in these environments, and provide an analogue for similar settings in the subsurface that act as hydrocarbon reservoir‐trap systems.

Geochemical and isotopic composition of volcanic rocks of the heterogeneous Miocene (~ 23–19 Ma) Tepoztlán Formation, early Transmexican Volcanic Belt, Mexico

We present the first geochemical data (major and trace elements, as well as Sr, Nd, and Pb isotopes) on volcanic rocks from the Tepoztlán Formation in the central Transmexican Volcanic Belt. The Tepoztlán Formation is up to 800m thick and comprises a wide range of primary volcanic rocks (lavas, pyroclastic density current deposits, pyroclastic fall deposits), and their secondary reworked products due to mass flow (lahars) and fluvial processes. Magnetostratigraphy combined with K/Ar and Ar/Ar geochronology suggests an age of Early Miocene (23–19Ma) for this Formation. Lava flows, pyroclastic rocks, dykes and volcanic clasts range from basaltic andesite to rhyolite, with a clear dominance of andesites and dacites. All samples are subalkaline and hy-normative. These rocks show homogeneous REE patterns with LREE enrichment and higher LILE concentrations with respect to HFSE, notably the typical negative anomaly of Nb, Ta, and Ti, suggesting a subduction-related magma genesis. Major and trace element concentrations show that either assimilation of heterogeneous continental crust or crustal recycling by subduction erosion and fractional crystallization are important processes in the evolution of the Tepoztlán Formation magmas. Isotopic compositions of the Tepoztlán Formation samples range from (87Sr/86Sr)t=0.703693 to 0.704355 and (143Nd/144Nd)t=0.512751 to 0.512882, falling within the mantle array. All geochemical characteristics indicate that these rocks originated from a heterogeneous mantle, modified and evolved through assimilation of country rock and fractional crystallization in the upper crust.

Modification of a maize simulation model under different water, nitrogen and salinity levels

Irrigation, salinity and nitrogen (N) are the three major limiting environmental factors inmaize yield potentials especially in arid and semi-arid regions. An integrated water and N MaizeSimulation Model (MSM) was modified for salinity conditions using 2009-2010 fieldexperiments data in southwest of Iran. Irrigation levels were: I1=1.0ETc+0.25ETc as normalleaching amount, I2=0.75I1 and I3=0.5I1, salinity of irrigation water: S1=0.6, S2=2.0 and S3=4.0dS m-1 and N fertilizer rate: N1=0, N2=150 and N3=300 kg N ha-1. Data of the first and secondyear were used to calibrate and validate the modified model, respectively. The MSM model wasmodified by including the combined effects of water and salt stresses using different wateruptake functions. Furthermore, N uptake via mass flow process was also modified. By thismodification, the soil salinity was also estimated by the model. Calibration/validation resultsshowed that the water uptake function of Homaee and Feddes led to a better estimation of allparameters than those obtained by other water uptake functions. Based on the NRMSE and dindices, the modified MSM model presented a very good to fair estimation of soil water content,salinity and N, evaporation, transpiration, evapotranspiration, leaf area index, total dray matter,N uptake and grain yield. Besides, under saline irrigation water there was much higher risk tothe groundwater contamination by nitrate leaching.

“Bottomsets” of the lava−fed delta of James Ross Island Volcanic Group, Ulu Peninsula, James Ross Island, Antarctica

Abstract Sedimentological study of the three geographically separated outcrops of bottom− sets of a single lava−fed delta (Pliocene) in the James Ross Island (Antarctica) allows recognition of six lithofacies.Deposits of traction currents, deposits of volcaniclastic debris flows and products of such flows transformations (both low− and high−density turbidity currents) and glacigenic deposits (subaqueous debris flows and traction/turbidity currents) were all recognised. Existence of submarine proglacial environment formed prior to formation of volcani− clastic deposits partly covering the subaqueous slopes of volcano is supposed. The principal role of mass flow processes was recognised and explained by relative steep slopes of the lava−fed delta. The distribution of lithofacies significantly differs in the individual outcrops. These variations in sedimentary succession and also in thickness of volcaniclastic deposits of “bottomsets” of the single lava fed delta suggest principal role of local conditions and paleogeography for development and preservation of this part of delta depositional system. Moreover proximal and distal setting can be followed and direct vs. more distant relation to over−riding lava−fed delta supposed. The sedimentary succession terminated by foresets of hyaloclastite breccia.

Modification of maize simulation model for predicting growth and yield of winter wheat under different applied water and nitrogen

Model WSM (Wheat Simulation Model) was developed based on the previous model (MSM, Maize Simulation Model). The planted cultivar was Shiraz with five irrigation treatments (1.2, 1.0, 0.8, and 0.5 ratios of the potential irrigation requirement under surface irrigation system and rain-fed) and four applied nitrogen treatments (0, 46, 92, 136kgNha−1). The irrigation water requirements were estimated by measuring the differences between soil field capacity and measured soil water content at root depth in the full irrigation treatment before irrigation. In the WSM model, dynamic flow of water, nitrogen, and heat through the soil were simulated numerically in an unsteady state condition at soil profile. Water and nitrogen transfer in the soil are governed by the Richard's equation and the diffusion convection equation, respectively. Emergence time of seed after sowing was simulated using soil water content, temperature, sowing depth, and soil particle diameters using beta function. Plant growth stages were simulated considering photoperiod, vernalization and air temperature. Hourly simulation of actual evaporation from soil surface and transpiration were simulated using the Penman–Monteith method based on atmospheric conditions and soil water content at root depth. Nitrogen uptake was simulated through mass flow and diffusion processes during the growing season. Produced dry matter was simulated as a function of hourly corrected intercepted radiation (based on air temperature) by plant leaves, maximum and minimum plant top N concentration and the amount of N uptake. Wheat grain yield was simulated by the ratio of grain N uptake and grain N concentration that were estimated by an empirical equation as a function of simulated top N uptake. Obtained experimental data in 2009–2010 were used to calibrate the model. The experimental results from 2010 to 2011 validated favorably the proposed model.

Origin and architecture of a Mass Transport Complex on the northwest slope of Little Bahama Bank (Bahamas): Relations between off-bank transport, bottom current sedimentation and submarine landslides

The analysis of the sedimentary dynamics of the carbonate slope of the northwest part of Little Bahama Bank (LBB, Bahamas) reveals a complex interaction between slope destabilisations, off-bank sediment export and longitudinal transport, the latter being driven by the Antilles and the Florida currents, at the northern end of the Florida Strait. Their combined action since the middle Miocene resulted in an extensional growth slope, previously called ‘LBB Drift’ (Mullins et al., 1980). Deposition within this extensional growth slope is dominated by either platform-derived downslope sedimentation or bottom current sedimentation. The latter induces the formation of a plastered drift, showing both upslope and downslope migrations, which do not correspond to the ‘LBB Drift’ as described by Mullins et al. (1980). Interestingly, a large submarine landslide affects the upper part of this plastered drift, and displays a complex and striking geomorphology on the seafloor. A new high-quality multibeam echosounder and seismic dataset allowed a detailed characterisation of the architecture of this Mass Transport Complex (MTC). A 44km-long circular incision at 275m and 460m water depths, with a steep external edge (from 40 to 70m high), forms the only present day evidence of this ancient MTC. It comprises confined Mass Transport Deposits (MTDs), which are delimited by frontal and lateral edges that developed inside the plastered drift. The top of this plastered drift is marked by a major erosional surface, most likely induced by an increase in oceanic current circulation. Channelised geometries, laterally associated with overspill deposits, developed within the depression induced by the MTC, and are an additional evidence of bottom current activity in this area. In addition, recent pockmarks are visible on the seafloor in front of the circular scarp of the MTC and probably relate to fluid escape, originating from the underlying MTDs' compressional area.All these features seen on the northwest slope of LBB bring new understanding on MTC sedimentary processes and associated morphologies in carbonate slope settings. Furthermore, this study highlights the interplay between off-bank transport, oceanic circulation and mass flow processes, which are seen as key processes in the shaping of Bahamian slopes and in their sedimentary dynamics.

Lithofacies and depositional environment of the Amasiri Sandstone, southern Benue Trough, Nigeria

Eight lithofacies typical of tidally-influenced shelf, mass flow and turbidity current processes characterize the Amasiri Sandstone (Cenomanian – Turonian) in the southern Benue Trough, Nigeria. The cross bedded sandstone lithofacies (Sxm) in Afikpo area were deposited in tidally influenced, shallow sandy shoreline environment while similar lithofacies associated with the conglomeratic lithofacies (Sfc) in Akpoha are proximal canyon–fill deposits. The conglomeratic lithofacies with rip-up clasts together with the massive, horizontal-bedded lithofacies (Smm) and parallel-laminated sandstone lithofacies (Sfl) in Akpoha were deposited in confined channels in proximal submarine canyon setting. The wavy/ripple-laminated sandstone lithofacies (Sfw) and very fine grained bioturbated sandstones lithofacies (Sfb) represent weakly confined distributary splay and unconfined associations in proximal to distal submarine canyon settings. The bioturbated mudstone lithofacies (Msb) and parallel-laminated mudstones lithofacies (Msl) comprise the bypass/levees association in the inner to outer shelf and in the distal canyon settings. Overall, these lithofacies indicate deposition in shelf to deep water depositional environments.

Subaqueous eruption-fed mass-flow deposits: Records of the Ordovician arc volcanism in the northern Famatina Belt; Northwestern Argentina

This study is focused on the analyses of a Chaschuil section (27° 49′ S–68° 04′ W), north of the Argentina Famatina Belt, where Ordovician explosive-effusive arc volcanism took place under subaerial to subaqueous marine conditions. In analyzing the profile, we have recognized an Arenigian succession composed by dominant volcaniclastic lithofacies represented by volcaniclastic debris flow, turbidity current and minor resedimented syn-eruptive pyroclastic depositsand lavas. The upper portions of succession are represented by volcanogenic sedimentary lithofacies with fossiliferous levels. Great volumes of the volcaniclastic deposits are strongly controlled in their transport by mass flow processes. These representative deposits provide significant data in relation to the coeval volcanic events for recognizing a continuous explosive volcanism together a minor effusive activity and the degradation of volcanic edifices. Likewise mass flow deposits give indications of the high rate of sedimentation, strong slope control and instability episodes in the basin, typical of those volcanic environments. That substantial information was the key to understand the features and evolution of the Arenigian basin in the north of the Famatina System.

Direct estimation of mass flow and diffusion of nitrogen compounds in solution and soil

Plant nutrient uptake from soil is mainly governed by diffusion and transpirationally induced mass flow, but the current methods for assessing the relative importance of these processes are indirect. We developed a microdialysis method using solutions of different osmotic potentials as perfusates to simulate diffusion and mass flow processes, and assessed how induced mass flow affected fluxes of nitrogen (N) compounds in solution and in boreal forest soil. Varying the osmotic potential of perfusates induced vertical fluxes in the direction of the dialysis membranes at rates of between 1×10(-8) and 3×10(-7) ms(-1) , thus covering the estimated range of water velocities perpendicular to root surfaces and induced by transpiration. Mass flow increased N fluxes in solution but even more so in soil. This effect was explained by an indirect effect of mass flow on rates of diffusive fluxes, possibly caused by the formation of steeper gradients in concentrations of N compounds from membrane surfaces out in the soil. Our results suggest that transpiration may be an essential driver of plant N acquisition.

To date or not to date - Does luminescence dating work in the European Alps and their foreland?

The Squantum ‘Tillite’ (c. 593–570 Ma) consists of thick (up to 215 m) massive and crudely-stratified diamictites conformably interbedded with subaqueously-deposited conglomerates and sandstones within a thick (~ 7 km) Boston Basin fill which is dominated by argillite turbidites. The Squantum Tillite was first interpreted as being glacigenic in origin in 1914 because of the presence of diamictites; argillites were interpreted as glaciolacustrine ‘varves’ with rare ice-rafted debris, and conglomerates as glaciofluvial outwash. More recently these have been shown to be the product of deep marine mass flow processes with no glacial influence, yet because of its age equivalence with the deep marine, glacially-influenced Gaskiers Formation, the Squantum Tillite is still seen by some as supporting evidence for a widespread ‘Snowball Earth’ event at c. 580 Ma. New sedimentological work confirms that conglomerate and sandstone facies are deep marine sediment gravity flows genetically related to massive (homogeneous) and crudely-stratified (heterogeneous) diamictites produced subaqueously by downslope mixing of gravel and cobbles with muddy facies. Rare horizons of ‘ice rafted debris’ in thin-bedded and laminated turbidite facies interbedded with thick debrites show a weak but positive correlation of lamina thickness with grain size, suggesting these facies are non-glacial co-genetic ‘debrite–turbidite’ couplets. A significant volcanic influence on sedimentation is identified from reworked lapilli tuff beds and reworked ash in turbidites. The depositional setting of the Squantum ‘Tillite’ appears to be that of a submarine slope/fan setting in an open marine volcanic arc basin receiving large volumes of poorly-sorted sediment on the mid-latitude active margin of Gondwana. No direct glacial influence is apparent.

Decrease of energy demand for bioethanol-based polygeneration system through case study

Economic competitiveness of bioethanol production strongly depends on the amount of heat and power consumed during the production process. Integration of different energy conversion processes by polygeneration is one of the solutions to minimize the use of energy resources to best meet user’s energy demands. In this study, a biogas generation system, a Fuel Cell system and a green house are integrated in the bioethanol plant to form a polygeneration system. At the same time, in order to further reduce the consumption of external energy sources, possibilities of heat energy integration, which looks for the best utilization of energy flows generated or consumed inside the process, have been investigated. Simulation of the polygeneration system is carried out by Simulink; energy saving potential for the polygeneration plant is analyzed to find the optimum configuration to maximize the electricity production while producing sufficient heat from both the Fuel Cell unit and pellets combustion to satisfy the energy requirements of the whole plant. Based on the simulation results, detailed energy and mass flow processes of the whole polygeneration plant was presented.

Diamondiferous, Neoarchean fan-delta deposits, western Superior Province, Canada: Sedimentology and provenance

Most fluvial diamond placers occur in non-aggrading braided systems where the diamonds are preferentially trapped by very rough substrates. The recognition that some of the Neoarchean, diamond-bearing breccias near Wawa, Ontario, Canada, are actually fluvial conglomerates, deposited by a mixture of traction current and mass-flow processes, provided the opportunity to add information on aggradational diamond placer systems. The 454m thick Leadbetter Conglomerate was studied to ascertain the depositional processes that led to the development and provenance of the placer. The Conglomerate is composed of a series of weakly sheared and highly viscous debris-flows interbedded with boulder to pebble conglomerates representing longitudinal bars and channels. Pebble conglomerate and sandstone channels become more dominant upwards, with a decrease in mass-flow processes. An abrupt marine transgression flooded this fan-delta assemblage ending deposition of the coarse-grained lithofacies. The lowest 100m of the conglomerate is composed of clasts derived solely from the underlying mafic volcanic assemblage. Above this zone the clast types become more diverse and felsic volcanic clasts become progressively more important upwards. Whole rock geochemistry performed on coarse-grained sandstone samples indicates that major sediment contributions came from mafic rocks and nearby diamondiferous lamprophyres and related breccias, though the possible existence of a localized kimberlitic source cannot be excluded. Geochemistry also indicates that minor enrichments of heavy minerals formed on the alluvial fan-delta surface but the primary cause of the conglomerate's diamondiferous nature was a nearby diamond-bearing source rock.