Trench Fill Research Articles

Late paleozoic–mesozoic subduction and accretion of the paleo-pacific plate: insights from the ocean plate stratigraphy of the wandashan accretionary complex, NE China

ABSTRACT The Wandashan accretionary complex (AC) is located in the easternmost part of Northeast China and consists of the Raohe complex in the east and Yuejinshan complex in the west. It represents an excellent location for insights into Paleo-Pacific subduction and accretion processes. However, the protolith (mainly contains Ocean Plate Stratigraphy ‘OPS’ and ophiolite) nature and tectonic evolution of the Wandashan AC are under debate. This contribution reports three representative geological sections, conducts the OPS reconstruction, compares the reconstructed Wandashan OPS with the adjacent Bikin OPS in Russia and Inuyama–Mino–Neo OPS in Japan, and re-accessed detrital zircon U-Pb age data of the Wandashan area. The results show that the protolith of the Yuejinshan complex is consistent with the OPS formed on a back-arc basin. This back-arc basin formed in the Early Permian and eventually closed after ~216 Ma, and the basin materials emplaced and metamorphosed at ~210–180 Ma to form the metasedimentary rocks and greenschists. The Raohe complex has a relatively complete OPS, which mainly includes Carboniferous–Permian coastal- to shallow-sea- limestones, Middle Triassic–Early Jurassic pelagic cherts, Middle Jurassic hemipelagic siliceous shales/mudstones and slates, and a Middle Jurassic–Early Cretaceous turbidite sequence. The provenances of the trench fill (turbidites) include the widespread Precambrian basement in NE China, the Yuejinshan complex, seamounts and seafloor sediments on the subducted slab, and the adjacent Jiamusi, Khanka, and Songnen massifs. The Raohe OPS experienced decollement, submarine sliding, diapirism, offscraping, underplating, out-of-sequence thrusting, and progressive disruption during the process of accretion, forming the Raohe complex in the Middle Jurassic–Early Cretaceous (~169–133 Ma). Together, the Raohe and Yuejinshan complexes form the Wandashan AC.

Arc tempos of the Gangdese batholith, southern Tibet

The character of arcs varies over time with significant temporal fluctuations in the quantity and spatiotemporal patterns of magmatism. However, the driving mechanisms for this episodic behavior of arcs need more constraints. This paper analyzed the published data along with our new zircon U-Pb dating and Hf isotopic and whole-rock geochemical data of plutonic rocks in the Gangdese belt in southern Tibet to explore the features, potential drivers, and tectonic implications of episodic arc activity in the Gangdese arc. A comprehensive compilation of U-Pb ages and Lu-Hf isotopic analyses of zircon grains from igneous rocks in the Gangdese belt, sedimentary rocks in trench fill sequences, forearc basins and foreland basins, and sands from modern river reveals that: 1) Gangdese arc activity was episodic during Late Cretaceous to Middle Eocene, displaying two magmatic flare-ups (ca. 100–80 and 65–45 Ma) and one magmatic lull (ca. 80–65 Ma), and 2) both flare-up magmas show relatively positive εHf(t) values (+5 ~ +15) indicative of juvenile sources suggesting these magmas are dominated by contributions from the depleted mantle. In contrast, the magmatic lull between these two magmatic flare-ups could be caused by flat subduction of the Neotethyan slab beneath the southern margin of the Lhasa terrane. These flare-ups likely contributed greatly to the crustal thickening of the Gangdese belt. Constraints from paleo-elevation and geochemical proxies for crustal thickness showed that the ~100–80 Ma flare-up was accompanied by the formation of a thick arc root while the ~65–45 Ma flare-up likely developed in a thinner crust without an arc root.

Controls on the origin and evolution of deep-ocean trench-axial channels

The type and volume of sediment entering subduction zones affects the style of plate-boundary deformation and thus sedimentary and tectonic cycles. Because submarine channels significantly increase the transport efficiency of turbidity currents, their presence or absence in subduction trenches is a primary control on trench fill. To date, comprehensive architectural characterization of trench-axial channels has not been possible, undermining efforts to identify the factors controlling their initiation and evolution. Here, we describe the evolution of the Hikurangi Channel, which traverses the Hikurangi Trench, offshore New Zealand. Analysis of two- and three-dimensional seismic data reveals that the channel was present only during the last ~3.5 m.y. of the ~27 m.y. of the trench’s existence; its inception and propagation resulted from increased sediment supply to the trench following amplified hinterland exhumation. To test if the controls on the evolution of the Hikurangi Channel are universal, multivariate statistical analysis of the geomorphology of subduction trenches globally is used to investigate the formative conditions of axial channels in modern trenches. Terrigenous sediment supply and thickness of sediment cover in a trench are the dominant controls; subsidiary factors such as trench length and rugosity also contribute to the conditions necessary for trench-axial channel development. Axial channels regulate sediment distribution in trenches, and this varies temporally and spatially as a channel propagates along a trench. The presence of a trench-axial channel affects plate-boundary mechanics and has implications for the style of subduction-margin deformation.

Along-strike variations in protothrust zone characteristics at the Nankai Trough subduction margin

AbstractSignificant along-strike changes in the protothrust zone at the toe of the Nankai Trough accretionary prism were imaged in new high-resolution seismic reflection data. The width of the protothrust zone varies greatly along strike; two spatially discrete segments have a wide protothrust zone (∼3.3–7.8 km, ∼50–110 protothrusts), and two segments have almost no protothrust zone (∼0.5–2.8 km, <20 protothrusts). The widest protothrust zone occurs in the region with the widest and thickest sediment wedge and subducting turbidite package, both of which are influenced by basement topography. The trench wedge size and lithology, the lithology of the subducting section, and the basement topography all influence the rate of consolidation in the trench wedge, which we hypothesize is an important control over the presence and width of the protothrust zone. We conclude that protothrusts are fractures that form from shear surfaces in deformation band clusters as the trench fill sediment is consolidated. Strain localization occurs at sites with a high density of protothrusts, which become the probable locations of future frontal thrust propagation. The frontal thrust may propagate forward with a lower buildup of strain where it is adjacent to a wide protothrust zone than at areas with a narrow or no protothrust zone. This is reflected in the accretionary prism geometry, where wide protothrust zones occur adjacent to fault-propagation folds with shallow prism toe surface slopes.

Basal Accretion Along the South Central Chilean Margin and Its Relationship to Great Earthquakes

AbstractThe south central Chilean margin regularly produces many of the world's largest earthquakes and tsunami, including the 2010 Mw 8.8 Maule and 1960 Mw 9.5 Valdivia events. In 2017, we acquired seismic reflection data along ~1,000 km of the margin using the R/V Langseth's 15 km long receiver array and 108.2 l (6,600 in3) seismic source to image structures associated with these ruptures. We focus on the Valdivia segment with the largest coseismic slip (~40 m). The outer 40 km of the forearc is an accretionary wedge constructed primarily of stacked sedimentary packages with irregular lengths and thicknesses and little along‐strike continuity. Forearc structures indicate that the accretionary wedge grows primarily through basal accretion of the downgoing trench fill. The décollement propagates along a weak boundary near the top of the trench fill but occasionally branches downward into the underthrust sediment along bedding horizons, peeling off slices that are underplated to the forearc. The shallow décollement level and the rarity of underplating events allow most of the trench sediment to subduct. As a result, only ~30% of the incoming sediment has been accreted since the Early Pliocene. This implies that, on average, ~1 km of sediment must subduct beyond the outer forearc, an inference that is supported by our seismic images. We propose that the thickness and great downdip and along‐strike extent of the underthrust layer, which separates the megathrust from the underlying roughness of the igneous ocean crust, ensures a smooth broad zone of strong coupling that generates the world's largest earthquakes and tsunami.

Proposal of Flowable Fill Designs for improvement of excavation and filling works of trenches in sanitation systems

Population grow in recent years requires an extension of the current pipeline sanitary system. For this purpose, granular excavation and landfill works are associated with pedestrian traffic congestion. Therefore, it is necessary to develop an innovative and sustainable alternative to reduce the problems generated during the execution of the conventional process. This research proposes the use of flowable fill due to the multiple advantages offered by this material. On the one hand, it is economical for medium to large trench fill volumes, considering savings in labor (it is done with a small number of workers), in equipment (does not require the rental or purchase of compaction equipment) and in time (the pouring is done by directly pumping the mixture, from the mixing machines to the excavation). On the other hand, being self-compacting and self-leveling decreases the width of the trenches, reducing excavation and filling volumes; which, in turn, incur money savings. Also, this material guarantees work safety, since people are not required inside the excavation and fill in poorly accessible areas without any problem. Dosages were established for ten flowable fill mixtures with cement contents of 50, 60, 70, 80 and 90 kg of cement and a range of admixture from 1.75 to 2.00%; The results indicated that decreasing the fine aggregate - coarse aggregate ratio, the compressive strength of the mixtures increases and the slumps of the mixtures decreases, and the compressive strength increases directly proportional to the cement content.

Trace elemental and Sr-Nd-Hf isotopic compositions, and U-Pb ages for the Kitakami adakitic plutons: Insights into interactions with the early Cretaceous TRT triple junction offshore Japan

We conducted major, trace element, Sr-Nd-Hf isotopic, and U-Pb geochronologic analyses of early Cretaceous Kitakami granitic plutons, northeast Japan. We suggest that these plutons include rocks of adakitic affinity, which indicate partial melting of an eclogitic slab. The Kitakami adakites were mostly derived from juvenile oceanic crustal sources, but include inherited zircons with Archean to Neoproterozoic Hf model ages. Rather than being directly derived from crustal rocks of these ages, zircons may have been detrital in the voluminous trench fill sandstone within the Jurassic northern Kitakami accretionary prism. The exhumation of older basement that served as the detrital zircon source may have been triggered by ridge subduction. Although the plutons show a general southward younging from northern Kitakami (120–130 Ma), southern Kitakami (115–125 Ma), and Abukuma (100–115 Ma), restoration of post-crystallization left-slip faults inverts this spatial pattern and results in a northward-younging pattern. This suggests northward migration of a trench-ridge-transform triple junction that included the Izanagi–Farallon ridge. The Sambagawa eclogite may be genetically related to the Kitakami adakite in time and space if the transform duplexing is restored.

Convection-Dependent Competitive Adsorption between SPS and EO/PO on Copper Surface for Accelerating Trench Filling

In the absence of halogen ion, the convection-dependent competitive adsorption between bis(3-sulfopropy)-disulfide (SPS) and poly(ethylene glycol)-block-poly(propylene glycol) copolymer (EO/PO) on unpowered (in open circuit) copper surface is found in sulfuric acid solution. Galvanostatic measurements and electrochemical impedance spectroscopy were employed to analyze this particular adsorption behavior, revealing that the adsorption of EO/PO is enhanced by increased local convection intensity. The molecular dynamic simulation demonstrates that the increase of EO/PO adsorption decreases the adsorption of coexisting SPS on copper surface, supporting that the enhanced EO/PO adsorption in strong convection condition leads to the decrease of coexisting SPS adsorption on copper surface with the increase of convection intensity. The study of this convection-dependent competitive adsorption behavior enriches the understanding for the convection-dependent adsorption (CDA) behavior on electrolytic copper ‘bottom-up’ filling. Besides, the competitive adsorption behavior serves as a powerful handle to manipulate the accumulation of SPS at via or trench bottom before electroplating for improving the efficiency of via or trench filling. For example, the silicon wafer trench filling by copper electroplating is significantly accelerated with the introduction of convection-dependent competitive adsorption. Furthermore, a possible mechanism for accelerating trench filling by pre-adsorption process of SPS together with EO/PO is proposed.

Modeling of Al Doping During 4H-SiC Chemical-Vapor-Deposition Trench Filling

Aluminum doping during 4H-SiC chemical-vapor-deposition (CVD) trench filling was numerically modeled toward precise design of high-voltage superjunction devices. As a first-order approximation, growth-rate- and surface-normal-scaling functions were determined based on the reported experimental results. Simulated isoconcentration contours of aluminum were confirmed to qualitatively agree with the reported imaging of doping in SiC by scanning spreading resistance microscopy. Improvement of the proposed models based on additional experiments should contribute to reducing the development time for 4H-SiC superjunction devices fabricated using CVD trench filling.

Mechanism of Cobalt Bottom-Up Filling for Advanced Node Interconnect Metallization

A mechanism of cobalt bottom-up trench fill for advanced node interconnect metallization was studied. The mechanism in question employs a single additive which suppresses cobalt plating and directly impacts the plating rate. Hydrogen, generated simultaneously during plating by electrolysis, reacts with the suppressor via hydrogen reduction, and the product of this reaction is a deactivated form of the suppressor. The local plating rate is governed by the relative concentrations of the activated/deactivated forms. Cyclic voltammetry (CV) shows that the suppressor deactivation is impacted by electrochemical potential, suppressor concentration, rotation rate, and pH, all of which may be controlled to generate bottom up fill in interconnects. Such impacts were confirmed on the plating of patterned coupons. This hydrogen reduction-induced deactivation mechanism provides a theoretical explanation for bottom-up plating in a single additive bath, and the factors that may impact the bottom-up filling.

Direct push sensing in wetland (geo)archaeology: High-resolution reconstruction of buried canal structures (Fossa Carolina, Germany)

(Geo)archaeological trenching techniques in floodplain and wetland environments are challenging due to the impact of groundwater inflow and highly unstable trench edges. Alternatively, classical driving core techniques often correspond with the contraction of organic layers and bias in height accuracies. Here, we present the application of direct push sensing techniques for minimal-invasive (geo)archaeological surveys in zones affected by a high groundwater table, especially when high-resolution parameterization of buried (geo)archaeological structures is required.Two of these direct push applications are electrical conductivity logging and the measurement of colorimetric proxies in unconsolidated sediments. The tools provide multi-proxy information about layer structure, texture, and organic parameters. The high sensing speed allows recording a large data set with high vertical and lateral resolution. In this study we exemplary provide results of a buried canal structure within a valley in SW Germany. We present a high-resolution cross-section from a zone of high groundwater table. The canal is part of Charlemagne's summit canal (Fossa Carolina), an Early Medieval hydro-engineering project bridging the Central European Watershed.We compare the direct push sensing data with driving core samples and discuss prediction and generation options of parameter transfer from multiple one-dimensional logs to a two-dimensional canal cross-section of high-resolution. In this context, we use in situ-obtained colorimetric data and electrical conductivity as proxies for (geo)archaeological site characterization. We model organic fills of the canal by direct push logs and robust sediment data. Given the cost and time effectiveness of such tools, (geo)archaeological site information of high-depth accuracy was grown rapidly, compared to less densely performed drillings that require an additional high effort in laboratory analyses.The Carolingian excavation depth is 6 m below current surface. There is evidence for multiple organic layers in the trench fills, which reveal aquatic to semi-terrestrial stillwater deposition and, therefore, evidence of multiple Carolingian and post-Carolingian ponds. We have evidence for a conceptual width of the deep-buried artificial water course of at least 3–4 m. This allows a passage of Carolingian cargo scows with a payload of several tons in this central zone of the canal.

Trench Filling Properties of Low k Insulated Layer Using Vacuum Ultraviolet Light-CVD

Photo-induced deposition of SiOCH thin films and their trench filling properties are discussed. Octamethyl-cycloterasiloxan (OMCTS) was used as a precursor and Xe2 excimer lamp was used as a light source. The deposition temperature was 80°C and the reactor pressure was maintained at 38.5 Pa. The relative permittivity of as-deposited film was 7.9. Due to the UV cure process, those OH-related bonds in the film were significantly decreased. The k-value of the UV cure film was 2.1. Photo-induced SiOCH was employed to achieve bottom-up filling of high-aspect-ratio features (A/S > 7.5).

An Assessment of Eco-Friendly Controlled Low-Strength Material

The present study aims to investigate the fresh and hardening properties of a soil-based controlled low-strength material (CLSM) containing stainless steel slag as a cementitious material. This type of CLSM primarily uses in construction as a trench-fill material. Four levels of the cement substitution (i.e. 0%, 10%, 20%, and 30%) and three amounts of binder content (80-, 100-, and 130kg/m3) were generated for the experimental work. Fresh and hardening properties of the recommended CLSM were examined in the laboratory. The results show that the proposed CLSM could be employed for eco- friendly trench fills.

Optimizing Middle of Line (MoL) Contact Cleaning to Preserve Tungsten (W) Integrity in Advanced Technology Nodes

Most of the advanced technology node semiconductor device manufacturing has adopted the gate-last approach which utilizes a RMG (Replacement Metal-Gate) process. The gate last method prevents unnecessary thermal loading on the high-k gate material and the metal layers; typically induced due to high-temperature activation of the doping regions. In gate-last process, junctions are salicidized after RMG requiring a different patterning approach for the active regions, i.e. an additional TS (Trench Silicide) mask is used. Thus the contact to the active regions is split into two levels. First the TS is formed and filled with tungsten which is followed by conventional contact patterning. With the increased complexity of contact architecture, contact cleaning becomes more critical in preventing contact opens as well as in maintaining the structural integrity to eliminate risks of contact to gate shorts and trench fill (tungsten) erosion. In this work, an advanced cleaning process is developed based on the electrochemical compatibility and interactions between the chosen chemistry and exposed layers as well as contaminants to be removed. The cleaning efficacy in the trenches is verified by measuring contact resistance as well as particle/flake inspections. Tungsten integrity is verified with bright field microscopy and damage to inter layer dielectrics is monitored by measuring trench and contact critical dimensions. Other structural interactions were studied with TEM imaging. The new cleaning process yielded substantially higher number of functional die as compared to POR (Process of Record). This paper will detail and discuss the above mentioned mechanism and performance data.

Seismic velocity structure and deformation due to the collision of the Louisville Ridge with the Tonga-Kermadec Trench

New marine geophysical data recorded across the Tonga-Kermadec subduction zone are used to image deformation and seismic velocity structures of the forearc and Pacific Plate where the Louisville Ridge seamount chain subducts. Due to the obliquity of the Louisville Ridge to the trench and the fast 128 mm yr−1 south–southwest migration of the ridge-trench collision zone, post-, current and pre-seamount subduction deformation can be investigated between 23°S and 28°S. We combine our interpretations from the collision zone with previous results from the post- and pre-collision zones to define the along-arc variation in deformation due to seamount subduction. In the pre-collision zone the lower-trench slope is steep, the mid-trench slope has ∼3-km-thick stratified sediments and gravitational collapse of the trench slope is associated with basal erosion by subducting horst and graben structures on the Pacific Plate. This collapse indicates that tectonic erosion is a normal process affecting this generally sediment starved subduction system. In the collision zone the trench-slope decreases compared to the north and south, and rotation of the forearc is manifest as a steep plate boundary fault and arcward dipping sediment in a 12-km-wide, ∼2-km-deep mid-slope basin. A ∼3 km step increase in depth of the middle and lower crustal isovelocity contours below the basin indicates the extent of crustal deformation on the trench slope. At the leading edge of the overriding plate, upper crustal P-wave velocities are ∼4.0 km s−1 and indicate the trench fill material is of seamount origin. Osbourn Seamount on the outer rise has extensional faulting on its western slope and mass wasting of the seamount provides the low Vp material to the trench. In the post-collision zone to the north, the trench slope is smooth, the trench is deep, and the crystalline crust thins at the leading edge of the overriding plate where Vp is low, ∼5.5 km s−1. These characteristics are attributed to a greater degree of extensional collapse of the forearc in the wake of seamount subduction. The northern end of a seismic gap lies at the transition from the smooth lower-trench slope of the post-collision zone, to the block faulted and elevated lower-trench slope in the collision zone, suggesting a causative link between the collapse of the forearc and seismogenesis. Along the forearc, the transient effects of a north-to-south progression of ridge subduction are preserved in the geomorphology, whereas longer-term effects may be recorded in the ∼80 km offset in trench strike at the collision zone itself.

Combining EMI and GPR for non‐invasive soil sensing at the Stonehenge World Heritage Site: the reconstruction of a WW1 practice trench

SummaryIncreasingly, conventional soil sampling procedures face restrictions because of their destructive character. Hence there is a growing interest in non‐invasive techniques, on which proximal soil sensors are based. There is great interest in applying proximal soil sensing to improve the characterization of the buried heritage embedded in the soil landscape at sites such as the Stonehenge World Heritage Site, UK. Because calibration and validation procedures based on invasive practices are unconventional, we turned to the investigation of a well‐documented practice trench dug during the First World War (WW1) close to the prehistoric Stonehenge monument. A methodology was tested that would simultaneously invert frequency‐domain ground‐penetrating radar (GPR) and multi‐receiver electromagnetic induction (EMI) data, with the aim of reconstructing the trench network. This trench network could not be distinguished on the EMI apparent electrical conductivity (σa) measurements, but appeared on the apparent magnetic susceptibility (κa) data. The GPR measurements showed the trench infilling as strong reflections contrasting with the surrounding soil. However, converting the two‐way travel times to absolute depths requires knowledge of the relative permittivity (εr). Because of the preference for non‐invasive observation in this protected landscape, we developed a procedure integrating the GPR measurements with κa measurements obtained with EMI. A fitting procedure, assuming a constant susceptibility and permittivity of the sub‐surface layers, allowed us to estimate both the susceptibility of the trench fill and the surrounding soil material, and the εr value of the material above and within the trench. This provided absolute depth values for the GPR reflection data, improving the lateral and vertical reconstruction of the trench system. Moreover, these results allowed depth slices to be determined from EMI κa data. So, integrating both GPR and EMI measurements enabled the detailed reconstruction of the buried trench network at Stonehenge, offering new perspectives on the investigation of features buried within the soil of protected sites.

Charlemagne's summit canal: an early medieval hydro-engineering project for passing the Central European Watershed.

The Central European Watershed divides the Rhine-Main catchment and the Danube catchment. In the Early Medieval period, when ships were important means of transportation, Charlemagne decided to link both catchments by the construction of a canal connecting the Schwabian Rezat and the Altmühl rivers. The artificial waterway would provide a continuous inland navigation route from the North Sea to the Black Sea. The shortcut is known as Fossa Carolina and represents one of the most important Early Medieval engineering achievements in Europe. Despite the important geostrategic relevance of the construction it is not clarified whether the canal was actually used as a navigation waterway. We present new geophysical data and in situ findings from the trench fills that prove for the first time a total length of the constructed Carolingian canal of at least 2300 metres. We have evidence for a conceptual width of the artificial water course between 5 and 6 metres and a water depth of at least 60 to 80 cm. This allows a crossing way passage of Carolingian cargo scows with a payload of several tons. There is strong evidence for clayey to silty layers in the trench fills which reveal suspension load limited stillwater deposition and, therefore, the evidence of former Carolingian and post-Carolingian ponds. These findings are strongly supported by numerous sapropel layers within the trench fills. Our results presented in this study indicate an extraordinarily advanced construction level of the known course of the canal. Here, the excavated levels of Carolingian trench bottoms were generally sufficient for the efficient construction of stepped ponds and prove a final concept for a summit canal. We have evidence for the artificial Carolingian dislocation of the watershed and assume a sophisticated Early Medieval hydrological engineering concept for supplying the summit of the canal with adequate water.

Enhancement of On-Resistance Characteristics Using Charge Balance Analysis Modulation in a Trench Filling Super Junction MOSFET

In Super Junction (SJ) MOSFETs, charge balance is the most important issue of the SJ fabrication process. In order to achieve the best electrical characteristics, such as breakdown voltage and on-resistance, the N-type and P-type drift regions must be fully depleted when the drain bias approaches the breakdown voltage, which is known as the charge balance condition. In conventional charge balance analysis, based on multi-epi process SJ MOSFETs, analytical model has only N, P pillar width and doping concentration parameter. But applying a conventional charge balance principle to trench filling process, easier than Multi-epi process, is impossible due to the missing of the trench angle parameter. To achieve much more superior characteristics of on-resistance in trench filling SJ MOFET, the appropriate trench angle is necessary. So in this paper, modulated charge balance analysis is proposed, in which a trench angle parameter is added. The proposed method is validated using the TCAD simulation tool.

Design and Fabrication of Super Junction MOSFET Based on Trench Filling and Bottom Implantation Process

In Super Junction MOSFET, Charge Balance is the most important issue of the trench filling Super Junction fabrication process. In order to achieve the best electrical characteristics, the N type and P type drift regions must be fully depleted when the drain bias approaches the breakdown voltage, called Charge Balance Condition. In this paper, two methods from the fabrication process were used at the Charge Balance condition: Trench angle decreasing process and Bottom implantation process. A lower on-resistance could be achieved using a lower trench angle. And a higher breakdown voltage could be achieved using the bottom implantation process. The electrical characteristics of manufactured discrete device chips are compared with those of the devices which are designed of TCAD simulation.

Sedimentary fill of the Chile Trench (32–46°S): volumetric distribution and causal factors

The Chile Trench of the convergent continental margin of Central Chile is a sediment-filled basin that stretches over 1500 km in a north–south direction. The sediment fill reflects latitudinal variations in climate as well as in the morphology and geology of Chile, but also of sediment transport processes to the trench and within the trench. We try to untangle these signals by calculating the total volume and the latitudinal volume distribution of trench sediments and by relating this distribution to a number of factors that affect this pattern. The volume calculation is based on a model geometry of the top of the subducting oceanic plate that is buried beneath trench sediments and the sea floor as measured by swath bathymetry. We obtain the model geometry of the subducting plate by interpolating between depth-converted seismic reflection profiles that cross the trench. The total volume of the trench fill between 32 and 46°S is calculated to be 46000 ± 500 km 3 . The resulting latitudinal volume distribution is best explained by a sedimentation model that alternates between (1) glacial phases of high sediment flux from Southern Chile combined with active latitudinal sediment transport within the trench and (2) interglacial phases over which sediment input is dominated by local factors. Supplementary material: Top of the oceanic basement (TOB) grid is available as ascii raw data files (xyz) at www.geolsoc.org.uk/SUP18664 .