Terrace Surfaces Research Articles

Small Pt nanoparticles on the TiO2 (110)–(1 × 2) surface

Scanning tunnelling microscopy (STM) has been used to study the initial stages of Pt deposition on the TiO2 (110)–(1×2) surface. Experimental STM images recorded for Pt coverage of 0.1 and 0.4 ML, suggest a Volmer-Weber growth. For low coverage and RT deposition, small clusters homogeneously distributed on the surface terraces are observed. However, after annealing at 825K, material agglomeration, with nucleation mainly at the cross-links, is observed as a consequence of Pt diffusion on the surface. Finally, the structure of small clusters has been determined, in good agreement with previous theoretical calculations.

Spontaneous formation of graphene-like stripes on high-index diamond C(331) surface

We employ first-principles density functional theory calculations to study the surface reconstruction, energetic stability, and electronic structure of diamond C(331) surface. Spontaneous formation of graphene-like stripes on the reconstructed surface is found to occur as the surface terrace C atoms transform from sp3 to sp2 hybridization upon structural relaxation. The comparison of the calculated absolute surface energies of C(331), C(111), and C(110) surfaces demonstrates the energetic stability of the graphitic-like C(331) surface. Local density of electronic states analysis reveals the occurrence of localized electronic states near the Fermi level, which may have a significant impact on the surface conductivity.

A 0.65 Ma chronology and incision rate assessment of the NW Iberian Miño River terraces based on 10Be and luminescence dating

In this work a series of 5 luminescence and 10Be dated fluvial terraces of the Miño River (NW Iberian Atlantic Margin) is presented. The outcomes allowed answering the longstanding question whether the Miño valley infill has a fluvial or marine origin. The perfect exponential decrease in 10Be concentrations with depth and a progressive increase in age with terrace altitude indicate that the Miño terraces are fluvial terraces rather than terraces incised in older marine basin infill. Accurate dating of the terraces was difficult due to saturation of the luminescence signal and high inheritance of 10Be concentrations. Nevertheless, minimum ages of up to 650ka could be determined and are very likely close to the real ages of the terraces.The age estimations and field evidence suggest that terrace formation and terrace incision occurred during eccentricity-forced cycles of glacio-eustatic sea level changes and tectonic uplift. The occurrence of a steep and narrow continental shelf probably favoured rapid and profound incision by the Miño River during periods of low sea levels. It is furthermore hypothesised that the transition periods between glacials and interglacials were especially important for terrace deposition and incision. Denudation rates of the terraces were calculated from the 10Be data and do not exceed 1.30mMa−1. These extremely low rates are probably the result of a combination of factors that favoured terrace preservation. Large, flat terrace surfaces with high permeability and continuous vegetation cover during the Quaternary stabilised the terrace surfaces.Maximum incision rates, calculated from terrace age and altitude, are 0.07–0.09mka−1. These values can be used as proxies for tectonic uplift rates. They are in agreement with published uplift rates along the northern Spanish coast and the westernmost termination of the Cordillera Cantabrica. This similarity most likely identifies a common tectonic regime leading to similar tectonic uplift rates. The results demonstrate that tectonic uplift occurs in a region that was until very recently considered as tectonically stable.

Terrace reconstruction and long profile projection: a case study from the Solent river system near Southampton, England

River terrace sequences are important frameworks for archaeological evidence and as such it is important to produce robust correlations between what are often fragmentary remnants of ancient terraces. This paper examines both conceptual and practical issues related to such correlations, using a case study from the eastern part of the former Solent River system near Southampton, England. In this region two recent terrace schemes have been constructed using different data to describe the terrace deposits: one based mainly on terrace surfaces; the other on gravel thicknesses, often not recording the terrace surface itself. The utility of each of these types of data in terrace correlation is discussed in relation to the complexity of the record, the probability of post-depositional alteration of surface sediments and comparison of straight-line projections with modern river long profiles. Correlation using age estimates is also discussed, in relation to optically stimulated luminescence dating of sand lenses within terrace gravels in this region during the PASHCC project. It is concluded that the need for replication at single sites means that this approach has limited use for correlative purposes, although dating of sediments is important for understanding wider landscape evolution and patterns of human occupation.

Lithium-ion conducting La2/3−xLi3xTiO3 solid electrolyte thin films with stepped and terraced surfaces

La2/3−xLi3xTiO3 (LLT, x = 0.1 and 0.167) thin films were grown on (001)-oriented SrTiO3 (STO) substrates by pulsed laser deposition. The resultant LLT films were heteroepitaxially grown with atomically flat surfaces. Although the films considered to be single crystalline, they were composed of 90°-rotated multi domains (∼5 nm in size) with epitaxial relationships of (100) [001] LLT || (001) [100] STO and (100) [010] LLT || (001) [100] STO. The bulk conductivity of the LLT (x = 0.1) films was 2.5 × 10−2 S cm−1 at 190 °C, comparable to that of a bulk single crystalline LLT. Single crystalline LLT thin films with atomically flat surfaces should help clarify interfacial lithium-ion conductivity. At the request of the authors, this article is being retracted effective 1 March 2013.

Adsorption of carbon monoxide on Pd (210) and (510) surfaces

Adsorption of carbon monoxide on Pd (210) and (510) stepped surfaces has been investigated by the extended London‐Eyring‐Polyani‐Sato method constructed using a five‐parameter Morse potential. Pd (210) and (510) stepped surfaces consist of terrace with (100) structure and step with (110) character. These results show that there exist common characteristics of CO adsorption on these two surfaces. At low coverage, CO adsorbs in twofold bridge site of the (100) terrace. The critical characteristics inherit that of CO molecule adsorbed in twofold bridge site of (100) original surface. When the coverage is increased, the top site of (110) step is occupied. The critical characteristics resemble that of CO molecule adsorbed in top site of (110) original surface. A number of new sites are exposed on the boundary regions, for example, the fivefold hollow site (H) of these two surfaces. There are stable adsorption sites at high coverage. Because of the different length of the (100) terrace, the (210) and (510) stepped surfaces have some different characteristics. First, CO is tilted adsorption on bridge site of terrace of (210), but perpendicular on terrace of (510) surface. Second, the bridge site (B1) where one Pd atom at the top of the step and the other at the bottom of the step is a stable adsorption site on (210), but the same type of site on Pd (510) surface is not. Copyright © 2012 John Wiley & Sons, Ltd.

Highly Adaptable Two-Dimensional Metal–Organic Coordination Networks on Metal Surfaces

The formation of extended two-dimensional metal-organic coordination networks (2D-MOCNs) showing high adaptability to surface step edges and structural defects is revealed by scanning tunneling microscopy. Rod-like 4,4'-di-(1,4-buta-1,3-diynyl)-benzoic acid (BDBA) and iron atoms assemble into extended 2D-MOCNs on Au(111) and Ag(100) surfaces. Independent from the chosen substrate and its surface symmetry the MOCN grows continuously over multiple surface terraces through mutual in-phase structure adaptation of network domains at step edges as well as on terraces. The adaptability of the MOCNs is mainly ascribed to the high degree of conformational flexibility of the butadiynyl functionality of the ligand. Despite their flexibility, the MOCNs exhibit considerable robustness against annealing at high temperatures. The findings show that mesoscale self-assembled functional architectures with a high degree of substrate error tolerance can be realized with metal coordination networks.

Unsteady late Pleistocene incision of streams bounding the Colorado Front Range from measurements of meteoric and in situ 10Be

Dating of gravel‐capped strath terraces in basins adjacent to western U.S. Laramide Ranges is one approach to document the history of late Cenozoic fluvial exhumation. We use in situ 10Be measurements to date the broad surfaces adjacent to the eastern edge of the Rocky Mountains in Colorado, and compare these calculated ages with results from meteoric 10Be measurements. We analyze three sites near Boulder, Colorado (Gunbarrel Hill, Table Mountain, and Pioneer) that have been mapped as the oldest terrace surfaces with suggested ages ranging from 640 ka to the Plio‐Pleistocene transition. Our in situ 10Be results reveal abandonment ages of 95 ± 129 ka at Table Mountain, 175 ± 27 ka at Pioneer, and ages of 251 ± 10 ka and 307 ± 15 ka at Gunbarrel Hill. All are far younger than previously thought. Inventories of meteoric 10Be support this interpretation, yielding ages that are comparable to Table Mountain and ∼20% lower than Pioneer in situ ages. We argue that lateral beveling by rivers dominated during protracted times of even moderate glacial climate, and that vertical incision rates of several mm/yr likely occurred during times of very low sediment supply during the few interglacials that were characterized by particularly warm climate conditions. In contrast to the traditional age chronology in the area, our ages suggest that the deep exhumation of the western edge the High Plains occurred relatively recently and at an unsteady pace.

Electrical properties and stability of an epitaxial alumina film formed on Cu-9 at. % Al(111)

An ultrathin epitaxial alumina film formed in ultrahigh vacuum on a Cu-9 at. %Al(111) single crystal was characterized by in situ low energy electron diffraction and reflection high energy electron diffraction methods and by ex situ x-ray diffraction and conducting atomic force microscopy (AFM) techniques. Ex situ measurement results on the crystal structure and surface morphology were compared with the in situ results. It was confirmed that the 1.6 nm-thick epitaxial film maintained its crystal structure and atomically flat terrace surface morphology after several months of air exposure. Current–voltage (I–V) measurements on the alumina film were performed using conducting AFM. No electrical breakdown occurred even when an electric field as strong as 2.5 × 109 V/m was applied. The band gap of the alumina film and the band alignment between the film and the substrate were determined from I–V curves.

Microstructure of Polycrystalline PBTTT Films: Domain Mapping and Structure Formation

We utilize near-edge X-ray absorption fine structure (NEXAFS) spectroscopy and scanning transmission X-ray microscopy (STXM) to study the microstructure and domain structure of polycrystalline films of the semiconducting polymer poly(2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene) (PBTTT). Total electron yield NEXAFS spectroscopy is used to examine the surface structure of the first 1-2 molecular layers, while bulk-sensitive STXM is used to produce maps of domain orientation and order sampled through the entire film thickness. We study different phases of PBTTT including as-cast, terraced and nanoribbon morphologies produced via spin-coating as well as aligned films of as-cast and nanoribbon morphologies produced by zone-casting. For the terraced morphology, domains are observed that are larger than the size of the terraced surface features, and the calculated degree of order is reduced compared to the nanoribbon morphology. For zone-cast films, we find that, although little optical anisotropy is observed in the bulk of as-cast films, a high degree of surface structural anisotropy is observed with NEXAFS spectroscopy, similar to what is observed in annealed nanoribbon films. This observation indicates that the aligned surface structure in unannealed zone-cast films templates the bulk ordering of the aligned nanoribbon phase. STXM domain mapping of aligned nanoribbon films reveals elongated, micrometer-wide domains with each domain misoriented with respect to its neighbor by up to 45°, but with broad domain boundaries. Within each nanoribbon domain, a high degree of X-ray dichroism is observed, indicating correlated ordering throughout the bulk of the film.

Shore platform development on an uplifting limestone island over multiple sea-level cycles, Niue, South Pacific

Niue is an uplifted limestone island, which preserves an atoll morphology with a sequence of terraces around its outer margin. A modern terrace fringes much of the island and this paper examines the extent to which this terrace can be considered accretionary and constructed by coral and coralline algae, or erosional and truncated by those processes that form shore platforms. The occurrence of Pleistocene limestone outcropping across this terrace and the continuation of caves and other karst features, dissecting the sub-aerial limestones, onto the forereef indicate the overall significance of erosion. At present live coral cover is restricted to isolated colonies growing in grooves, potholes and karstic channels eroded into the modern terrace surface. Coralline algae coat the outer margin of this terrace, and also veneer prominent surf benches that occur on the windward shore, 1–2m above the terrace surface. Terrace evolution on Niue therefore appears to be primarily erosional in origin. There is little accommodation space for reef growth and, as a result, accretional fringing reefs are absent around most of the island. Erosional processes have also dominated landscape evolution for at least the past few eustatic cycles. Fringing reef growth is absent or severely restricted during the last interglacial and occurs as sporadic small reefs on the seaward margin of an erosional terrace during the penultimate interglacial. The development of terrace features in uplifting reef settings does not necessarily originate through accretional reef processes and may in fact be entirely erosional. Although reef terraces are frequently depositional in other settings, those present on Niue indicate a predominance of erosion, indicating the need to discriminate emergent terraces in terms of the extent to which they are erosional or accretionary when using such features to reconstruct island palaeoenvironments.

Acoustic facies and seabed features of the mixed carbonate-siliciclastic deposits of the last eustatic cycle in the La Maddalena Archipelago (North Sardinia, Italy)

A high-resolution Chirp acoustic survey of 250 nautical miles performed in the La Maddalena Archipelago provided a scheme of the acoustic facies of the recentmost sediments and a frame of the large-scale bedforms linked to the last eustatic cycle that charac - terize its channels. Five main acoustic facies have been recognized and mapped. Due to the good coherence with the sediment texture map of the area, an interpretation of the acoustic facies in sedimentary terms is presented. The archipelago is characterized by a complex system of inlets, promontories, bays and channels ruled by the main tectonic trends of the region. A main, 20 km-long channel (Bucinara Channel) with numerous straits and some shoals divides the northern Sardinia coast from the main islands of Spargi, La Maddalena, Santo Stefano and Caprera. A shorter and larger channel occurs in the northern part of the Archipelago. Two minor sea branches connect these channels. The bathymetry of the area reveals that the channels generally have a flat bottom and steep flanks, with water depth mostly ranging between –35 and –60 m, with the exception of saddles and shoals. The sedimentary regime of the area is controlled by storm-induced currents and by a high carbonate production associated to the widespread presence of the Posidonia Oceanica seagrass, a marine Phanerogama that populates the flanks of the channels of the Archipelago. A multitude of morphologic forms can be attributed to the phases of falling, lowstanding, rising and high-standing of the last Pleistocene-Holocene eustatic cycle. Angular unconformities, gullies and sediment-incised palaeo channels along with abrasion platforms in the granitic basement witness the last sea level fall and low-stand. These forms now lie at water depths ranging between –33 m and –60 m and are covered by a thin veneer of sediments of the Holocene transgression. They have all been formed when the sea-level was about –110 m below the present datum and the Archipelago was a landscape of rocky hills separated by large, flat valleys scoured by torrent-like rivers. The Holocene rise of sea-level (Versilian transgression) caused the flooding of the landscape and the deposition of the thin sedimentary cover imaged by the acoustic profiles. The rising was punctuated by some sea-level still stands evidenced by terraced surfaces lying at depths between –33 m and –47 m which are coherent with the mapped and dated beach-rocks of the Bocche di Bonifacio strait. The decrease of sea level rise at 5000-6000 years B.P. and the following stabilization of sea level have triggered the present sedimentary and hydrodynamic conditions which, in turn, favoured the formation and maintenance of the bedforms. The Archipelago is dominated by an eastward directed sea current, and subordinately by a westward current. In the two main WNW-ESE and W-E trending channels of the Archipelago, the current flows have formed some longitudinal sand ridges up to 3 km long and 5 m high, while in the N-S oriented channels, transversal sand banks up to 10 m thick occur. Sea floor undulations, interpreted as sand waves, are present in some restricted areas close to the Sardinia coast in downflow position with respect to the headlands. Their wavelength (L) ranges between 10 to 40 m and the height (H) is up to 1,5 m, the ratio H/L

Toward quantifying geomorphic rates of crustal displacement, landscape development, and the age of glaciation in the Venezuelan Andes

We present the results of dating glacial landforms in Venezuela using 10Be terrestrial cosmogenic nuclide (TCN) analysis and optical stimulated luminescence (OSL). Boulders on the La Victoria and Los Zerpa moraines of the Sierra Nevada that mark the extent of the local last glacial maximum (LLGM) yield 10Be TCN surface exposure ages of 16.7±1.4ka (8 samples). About 25km to the west in the drainage basin of the Río Mucujún, 10Be TCN dates for boulders on moraines at La Culata in the Sierra Nevada Norte yield a younger average age of 15.2±0.9ka (8 samples). The data suggest that glaciation across the Venezuelan Andes during the LLGM was asynchronous. The LLGM in Venezuela may be broadly concurrent with Heinrich Event 1 at ~16.8ka, implying that glaciation here is dominantly temperature driven. A moraine inset into the older laterofrontal moraines of La Culata has an age of 14.1±1.0ka (5 samples); it may have been deposited by a small Late Glacial readvance. Right-lateral offsets of the La Victoria and Los Zerpa moraines by the Boconó fault are each ~100m. The 10Be TCN based Boconó fault slip rate is about <~5.5 to 6.5mma−1, notably less than the total right-lateral slip of 12±2mma−1 of shear documented across the Andes from geodesy. The 10Be TCN dating of boulders on a faulted alluvial fan along the northwestern range front at Tucanízón yields a late Pleistocene uplift rate of the Andes at between ~1.7±0.7mma−1. Glacial outwash has produced valley-fill sequences within the central Andean valley along the trace of the Boconó fault and Río Chama. The valley-fill has been incised to produce the ‘meseta’, a terrace surface that sits >100m above the Río Chama and on which the major city of Mérida is built. Geomorphic observations indicate that the meseta deposits were largely derived from the glaciers of La Culata. The OSL dating suggests that the final aggradation of the valley-fill deposits occurred rapidly over a period of about 5 to 6ka and that the surface was abandoned and initially incised at ~30ka. The result implies Venezuelan valley fills record phases of aggradation that are likely modulated by climate change on glacial/Milankovitch timescales.

Cosmogenic 10Be and OSL dating of fluvial strath terraces along the Osip-cheon River, Korea: tectonic implications

The Osip-cheon River flows along a linear valley that runs approximately parallel to the Osip-cheon Fault. The present study was undertaken to elucidate the tectono-geomorphic evolution of the Osip-cheon Basin during the late Quaternary by employing cosmogenic 10Be surface exposure dating and optically stimulated luminescence (OSL) dating on a flight of fluvial strath terraces. Several morphometric indices (e.g., stream length-gradient index, asymmetry factor, transverse topographic symmetry factor, stream power incision) for relative tectonic activity are determined with the help of GIS analysis, suggesting minimal tilt of the blocks on either side of the Osip-cheon Fault, with displacement being mainly strike-slip. Thus, it is suggested that the Osipcheon River is a kind of subsequent stream that follows the weakened fault-line in the center of the basin. To determine the fluvial incision rate as an equivalent to the rate of local tectonic uplift, samples for cosmogenic 10Be dating and OSL dating were collected from the surfaces of strath terraces at two different areas along the Osip-cheon River. The terraces can be divided into three groups (T1: oldest to T3: youngest) depending on the height above the present river level. According to our data, the strath terraces formed at ca. 200 ka for T1, ca. 104 ka for T2, and ca. 14 ka for T3. The fluvial incision rate was determined by dividing the height of the terraces above the river by their respective ages. The fluvial incision rate has decreased over the last 200 ka, with a maximum rate of 0.28 mm/yr occurring between T1 and T2 (i.e., ca. 200 ka to 104 ka) followed by a rate of 0.21 mm/yr for the period from T2 to T3 (i.e., ca. 104 ka to ca. 14 ka), and a minimum rate of 0.17 mm/yr since the abandonment of T3 (i.e., over the last 14 ka). Tong-ri Canyon is deeply incised up to the major knickpoint of the Mi-in Falls. Here, the rock-cut strath terraces can be divided into two groups: the farther upstream part of the Tong-ri area (Site-1) was dated to 5.5 ± 0.5 ka, equivalent to the incision rate of 0.26 mm/yr, and the downstream part of the Tong-ri area (Site-5) was dated to 18.5 ± 1.8 ka, equivalent to the incision rate of 0.23 mm/yr. Given the active upstream migration of the knickpoint (Mi-in Falls) found in the upper reach of the river, the incision rate provided by the ages of the strath terraces in the Tong-ri Canyon should be higher than that for any other reach of the river. However, the incision rate of the reach below the mouth of Tong-ri Canyon is similar to the value of the reach above the major knickpoint, suggesting that knickpoint migration in the Tong-ri area was not active during the last 18.5 ka. Rather, it seems to have advanced to a certain level of incision in the past. Along the Osip-cheon River, the values of stream power incision and stream length-gradient show a contrasting distribution. The highest and most anomalous values of these indices are found along the upstream part of the Osip-cheon River. These indices values are likely to be associated with stream piracy. Given the geomorphic features (e.g., elbow of capture, wind gap, waterfall) found in the Tong-ri Canyon area, stream piracy might have been caused by Quaternary reactivation of the Osip-cheon Fault or by the ongoing but slowing, long-term regional tectonic uplift, with an axis along the Taebaek Mountain Range.

Chronology and processes of fluvial terrace formation in northeastern Kinki district, southwest Japan, based on cryptotephra analysis

Kinki district is a tectonically active area in southwest Japan. This area is located far from active volcanoes, and eolian deposits covering fluvial terrace deposits are not as thick as those in Kanto district. Thus, terrace chronology and processes of terrace formation previously were poorly established in Kinki district. Cryptotephra analysis identified invisible tephra horizons in eolian deposits covering fluvial terrace deposits in Takashima, Sekigahara and Inabe regions, including the Kikai-Akahoya tephra (K-Ah: 7.3 ka), Aira-Tn tephra (AT: 26–29 ka) and Kikai-Tozurahara tephra (K-Tz: 95 ka) horizons. Taisanjino 1 terrace in Takashima and Md1 terrace in Inabe were formed during Marine Isotope Stage (MIS) 5e, and Nakano terrace in Takashima, L2 terrace in Sekigahara and L2 terrace in Inabe were formed during MIS 2, based on their ages and geomorphic features. Aggradational terraces formed during MIS 2 exhibit similar geomorphic features among the three regions, although these regions have different base-levels of erosion and active fault movements. This means that the terrace formation during MIS 2 was mainly affected by climate changes, not by base-level changes and active fault movements. The main factor of terrace formation during glacial periods was the decrease in precipitation and water discharge due to climate changes, because the study area was not affected by glacial and periglacial processes during MIS 2. This indicates that aggradational terraces formed during glacial periods not only in glacial and periglacial areas but also in non-glacial and non-periglacial areas. From processes of terrace formation during MIS 5e, the tectonic base-level descent was important for terrace formation during interglacial periods, because terraces were formed during MIS 5e by active fault movements in the Takashima region despite small lake-level changes. Uplift rates of the Kamidera and Kuwana faults were 1.08 mm/y and >0.5 mm/y, respectively, based on the height of terrace surfaces formed during MIS 5e.

Fluvial response to sea-level changes since the latest Pleistocene in the near-coastal lowland, central Kanto Plain, Japan

This paper addresses the influence of sea level changes on the stratigraphy and basal topography of latest Pleistocene–Holocene incised valley fill of the Arakawa and Menuma Lowlands in central Japan by using sedimentary drill cores and columnar geologic sections. In the study area, four buried fluvial terrace surfaces (I to IV) formed in response to sea-level fall during the last glacial period. Surface III is covered with As-YP tephra (15–16.5ka) and extends at least 65km landward from the present mouth of the Arakawa River. A buried valley named surface V that extends from at least 85km upstream from the present river mouth to about 120m below present sea level on the continental slope was incised in response to the sea-level lowstand of the Last Glacial Maximum. The incised valley fill can be divided into three units: unit A (gravelly river channel sediments including valley-bottom gravels), unit B (fluvial sediments), and unit C (marine sediments), which intertongues within unit B and pinches out up to 60km upstream from the present river mouth. Unit C marks the landward limit of Holocene transgression. The lower part of unit B is a fining-upward succession formed during rising sea level and indicates retrogressive aggradation of floodplain sediments during transgression, whereas the upper part of unit B was formed during a sea-level highstand. The floodplain migrated more than 85km upstream from the modern shoreline in response to sea-level rise until the middle Holocene and extends over several tens of kilometers beyond the landward limit of the Holocene marine transgression.

On the genesis of some bottom and coastal features in the Eastern Gulf of Finland

An investigation undertaken recently by the Division of Regional Geoecology and Marine Geology of the Karpinsky All-Russian Research Geological Institute in the coastal zones of the Eastern Gulf of Finland allowed finding some specific relief forms of both near-shore bottom topography and shoreline shape. First of all, among the most interesting objects, the sand ridges on the surface of submarine terrace (between Repino locality and Cape Lautaranta) should be mentioned. These ridges are elongated at an angle to the shoreline and are located beyond the limits of wave action. The other interesting morphological type is represented by longshore sand waves up to some hundreds of meters long and some tens of meters wide near the Bol’shaya Izhora locality. Longshore sand waves move along the southern coast of the gulf, this causing alteration of erosion and accretion zones and leading to formation and degradation of the sand spits. Shore-face-connected ridges are believed to develop under the action of drift currents generated during the passage of deep west cyclones. It is shown that the ridge turned toward the current gives rise to a convergence of the cross-shore flows over the crest and provokes a shift of the maximum velocity toward the front side of the structure. Associated changes in sediment discharges result in accumulation and growth of the ridge. The origin of wavelike features in the shoreline contour (longshore sand waves) is due to a very oblique wave approach caused by predominance of the west winds blowing along the axis of the gulf. Under these conditions a small perturbation of the shoreline contour is shown to manifest a trend to increase with time.

Quantitative morphotectonics of the Pliocene to Quaternary Auletta basin, southern Italy

The geomorphological evolution of the Pliocene–Quaternary Auletta basin, a wide fault-bounded depression of the southern Apennines axial zone, Italy, was reconstructed using both DEM-based morphometric analysis and classical morphotectonic investigations. Morphotectonic analyses have been integrated with geological, structural and paleomagnetic data in order to reconstruct the Quaternary evolution of the area. The Auletta basin coincides with the lower valley of the Tanagro River and is filled by Pliocene to Pleistocene marine and continental sediments. The strike of the basin is N120–130°, according to the main fault systems of the area. Long-term landscape evolution results from interaction and feedback of geomorphic stages with the morphogenesis of erosional land surfaces alternating with tectonic pulses in which also block-tectonic rotation occurred. The ages of the morphological de-activation of such terraced surfaces have been roughly defined on the grounds of their morpho-stratigraphic relationships with Pliocene and Quaternary deposits, and better constrained by radiometric dating. Tectonic tilting has been established from morphological relationships between rotated blocks related to the activity of the Alburni fault line and the several generations of erosional and depositional land surfaces. The stratigraphic, structural, paleomagnetic and geomorphological data presented here suggest that the studied basin appears to have a more complex tectonic evolution than an extensional graben. Transtensional tectonics along NW–SE striking, listric faults of the Alburni margin system created the depression since Pliocene times, whereas extensional tectonics plays a key role in the middle to late Pleistocene morphotectonic evolution of the basin. This work demonstrates the usefulness of an integrated analysis in order to extract information on tectonic activity and landscape evolution in the Auletta basin, as an example for other study areas.

Identification of Lower Pleistocene tephras under Tokyo and reconstruction of Quaternary crustal movements, Kanto Tectonic Basin, central Japan

The Kanto Tectonic Basin (KTB) originated from a paleo-forearc basin, and is filled with the Pleistocene Kazusa Group, Quaternary marine sediments with a thickness of more than 3000 m. In order to understand general process of emerging paleo-forearc basin development on active plate margins, an attempt was made to establish the tephrochronological framework of the Kazusa Group under the Tokyo metropolitan area, southwest KTB, and reconstruct changes in depositional environments and geological structure. Chemical compositions of major, trace and rare earth elements of glass shards, and refractive indices of glass shards and phenocrysts, were used to identify 12 Early Pleistocene tephras collected from five sediment cores, including seven tephras newly recognized under the Tokyo metropolitan area: Kd8B, YM, KK, Ob4e-Kd23A, Ob4d-Kd23B, Ob4c-Kd24, Ob4b-6, Ob4b-5, Ob4b-4, Ob4b-1, Omn-SK110, and SYG, in descending order. Calcareous nannofossil biostratigraphic and magneto-stratigraphic positions of 24 tephras discussed in this paper, including 17 known tephras described by previous studies, indicate that their ages range from ca. 0.9 Ma to ca. 2.0 Ma. Northward-dipping strata with a gradient of about 0.015 of the base of the Johoku Sand and Gravel Bed (1.219–1.343 Ma) indicates that south-side was uplifted, caused by crustal movements with a mean ratio of 1.2 × 10 −5/ky since its deposition. This movement has continuously occurred, deforming MIS 5.5 marine terrace surfaces. The depths of SYG and Ob4c-Kd24 suggest that the deformation of the southwestern part of the NE-SW trending Mizonokuchi Syncline is significantly lower than that of the northeast part. This syncline extends northeastward to the southeastern part of the Musashino Upland. Activity of the Mizonokuchi Syncline probably was terminated at the end of the Early Pleistocene to Middle Pleistocene. The Tachikawa Active Fault (TAF), trending NW-SE, has been active since the Middle Pleistocene. The termination of the Mizonokuchi Syncline and the activation of TAF simultaneously occurred roughly around 1.0–0.5 Ma. These tectonic changes most likely resulted from a change in motion direction of the Philippine Sea Plate relative to the North American Plate.

Nanoimprint Fabrication and Thermal Behavior of Atomically Ultrasmooth Glass Substrates with 0.2-nm-Height Steps

We examined the conditions for the development of atomically stepped ultrasmooth surfaces on commercial silicate glass substrates by the thermal nanoimprint technique using sapphire (α-Al2O3 single crystal) molds with 0.2-nm-height atomic steps. Under the pressing conditions of 3 MPa, 300 s, and 610 °C for imprinting, a 0.2-nm-high stepped and atomically ultrasmooth terraced surface could be formed on soda-lime silicate glass substrates having the glass transition temperature of 521 °C. We found that the 0.2-nm-height step structure of the imprinted glass surface disappeared after annealing at 490 °C, and the smoothness of the terrace increased.