Bank Erosion in Fifteen Tributaries in the Glaciated Upper Susquehanna Basin of New York and Pennsylvania

The proportional contributions of cultivated lands and stream banks as sources of fine sediment loads were quantified in 15 rural watersheds in the Glaciated Appalachian Plateau region of the Susquehanna River basin of New York and Pennsylvania. We utilized a relatively simple method of fingerprinting sediment sources by comparing the concentrations of the nuclear bomb-derived radionuclide ¹³⁷ Cs in fluvial sediment samples collected from channel margins with sediment from cultivated fields and stream banks. The proportion of fine sediment from bank erosion ranged from none to 100% in the study tributaries, with a median contribution of 53% across the 15 study streams. In one stream with no evidence of bank sediment, anomalously high ¹³⁷ Cs levels in the samples indicated that the sources were pasture or forest, probably scoured from marshy floodplains upstream of the sampling sites. In the 14 other streams, cultivated lands accounted for an average of 42% of the fine sediment. We discuss sources of eroded bank material and the processes driving stream bank erosion in this glaciated region, and examine the impact of historic mill-dam deposits on bank erosion.     

The Upper Rhône Delta Sedimentary Record in the Arles-Piton Core: Analysis of Delta-Plain Subenvironments, Avulsion Frequency, Aggradation Rate and Origin of Sediment Yield

Results from analyses of the Arles‐Piton sediment core, retrieved from the apex of the Rhône Delta, highlight processes of Holocene deltaic construction controlled mainly by hydrosedimentary variability and channel avulsions. The alluvial suite was investigated for grain size, sedimentary structures, CaCO₃, organic matter, heavy minerals and chrono‐stratigraphy (¹⁴C and archaeological/historical dates). The study shows the succession of six facies associations: a distributary channel (before 6157‐5843 BC), a swamp (5719‐5530/4796‐4463 BC), a distal flood plain (5719‐5530/4796‐4463 BC), a distributary channel (4796‐4463/2900‐2503 BC), a proximal flood plain (2900‐2503 BC/AD 270‐290), and a crevasse splay (after AD 270‐290). Substantial changes in hydrodynamics are strongly linked to three channel avulsions (before 6157‐5843 BC, after 4796‐4463 BC and after 2900‐2503 BC). A correlation with the whole channel avulsion history of the Rhône Delta allowed us to propose an average rhythm of channel avulsion of c. 1450 years. From 5719‐5530 BC to AD 270‐290, the flood plain aggraded at the average rate of 2.5 mm/a. The aggradation rates were higher both in the proximal and distal flood plains, where sedimentation process is continuous. They were lower both in the active distributary channels, because of frequent truncation of the alluvial suite, and the abandoned channels where detritic inputs are minimum. The sediment supply arriving to the upper Rhône Delta was derived mainly from proximal source areas (Massif Central, Southern Alps) during the last 8000 years, except during the hydrological changes of Roman antiquity during which detritic inputs were derived firstly from the Northern Alps and Southern Alps, and secondly from the Massif Central.     

Tectonics and sedimentation in the hangingwall of a major extensional detachment: the Devonian Kvamshesten Basin, western Norway

The Middle Devonian Kvamshesten Basin in western Norway is a late-orogenic basin situated in the hangingwall of the regional extensional Nordfjord–Sogn Detachment Zone. The basin is folded into a syncline with the axis subparallel to the ductile lineations in the detachment zone. The structural and stratigraphic development of the Kvamshesten Basin indicates that the basin history is more complex than hitherto recognized. The parallelism stated by previous workers between mylonitic lineation below the basin and intrabasinal fold axes is only partly reflected in the configuration of sedimentary units and in the time-relations between deposits on opposing basin margins. The basin shows a pronounced asymmetry in the organization and timing of sedimentary facies units. The present northern basin margin was characterized by bypass or erosion at the earliest stage of basin formation, but was subsequently onlapped and eventually overlain by fanglomerates and sandstones organized in well-defined coarsening-upwards successions. The oldest and thickest depositional units are situated along the present southern basin margin. This as well as onlap relations towards basement at low stratigraphic level indicates a significant component of southwards tilt of the basin floor during the earliest stages of deposition. The inferred south-eastwards tilt was most likely produced by north-westwards extension during early stages of basin formation. Synsedimentary intrabasinal faults show that at high stratigraphic levels, the basin was extending in an E–W as well as a N–S direction. Thus, the basin records an anticlockwise rotation of the syndepositional strain field. In addition, our observations indicate that shortening normal to the extension direction cannot have been both syndepositional and continuous, as suggested by previous authors. Through most of its history, the basin was controlled by a listric, ramp-flat low-angle fault that developed into a scoop shape or was flanked by transfer faults. The basin-controlling fault was rooted in the extensional mylonite zone. Sedimentation was accompanied by formation of a NE- to N-trending extensional rollover fold pair, evidenced by thickness variations in the marginal fan complexes, onlap relations towards basement and the fanning wedge geometry displayed by the Devonian strata. Further E–W extension was accompanied by N–S shortening, resulting in extension-parallel folds and thrusts that mainly post-date the preserved basin stratigraphy. During shortening, conjugate extensional faults were rotated to steeper dips on the flanks of a basin-wide syncline and re-activated as strike-slip faults. The present scoop-shaped, low-angle Dalsfjord fault cross-cut the folded basin and juxtaposed it against the extensional mylonites in the footwall of the Nordfjord–Sogn detachment. Much of this juxtaposition may post-date sedimentation in the preserved parts of the basin. Basinal asymmetry as well as variations in this asymmetry on a regional scale may be explained by the Kvamshesten and other Devonian basins in western Norway developing in a strain regime affected by large-scale sinistral strike-slip subparallel to the Caledonian orogen.     

On the frequency of lake-effect snowfall in the Catskill Mountains

Meltwater from snow that falls in the Catskill/Delaware watershed in the Catskill Mountains in south-central New York contributes to reservoirs that supply drinking water to approximately nine million people in and near New York City (NYC). Using the Interactive Multisensor Snow and Ice Mapping System (IMS) 4-km snow maps from the National Oceanic and Atmospheric Administration’s National Ice Center, we identified and tracked 28 lake-effect (LE) storms that deposited snow in the Catskills (2004–2017). These storms, which generally originated from Lake Ontario, but sometimes from Lake Erie, represent an underestimate of the number of LE storms that contribute snowfall to the Catskills snowpack because snowstorms are not visible on IMS maps when they travel over already-snow-covered terrain. Using satellite, meteorological (including NEXRAD and National Weather Service Cooperative Observer Program), and reanalysis data, we identified conditions that contributed to the LE snowstorms and mapped snow-cover extent (SCE) following the storms. We show that LE snow makes an important contribution to the Catskills snowpack because of the frequency of events, even though the total amount of each event may, on average, be small. The IMS 4-km maps tend to overestimate SCE compared to MODerate-resolution Imaging Spectroradiometer and Landsat snow maps. Climate change could impact LE storms and the distribution of rain versus snow in the Catskills, which may affect future reservoir operations in the NYC Water Supply System and winter recreation in the Catskills.     

Late Archean basement in the Bangenhuken Complex of the Nordbreen Nappe, western Ny-Friesland, Svalbard

The rocks of western Ny-Friesland, northern Svalbard, are part of a tectonostratigraphy including four thrust sheets, each composed mainly of orthogneisses overlain by younger metasedimentary rocks. Previous geochronological studies have shown that the orthogneisses are dominated by ca. 1750 Mya granitoids. This study of a quartz-monzonite in one of the thrust sheets, the Nordbreen Nappe, yields a single-zircon U-Pb ion-microprobe age of 2709 Ø 28 My. This is the oldest rock unit so far reported in the Svalbard Caledonides. However, age-determinations on detrital zircons in the metasediments of western Ny-Friesland have shown that Late Archean rocks were prominent sources. The new ages presented here provide the first evidence of a local source for these sedimentary rocks.     

Tree-ring evidence linking late twentieth century changes in precipitation to slope instability,central New York state,USA

The Burtonsville landslide in central New York, USA, is a kilometer-scale rotational block failure in glacial till that was likely initiated by incision of the adjacent Schoharie Creek. Although the timing of initial failure is unknown, relatively fresh scarps and tilted surfaces suggest that movement is post-glacial and active. The river currently erodes the toe slope and it removed significant material during flooding associated with Hurricane Irene (August 2011). We retrieved tree cores from 111 trees across the landslide to reconstruct modern movement and block tilting as it related to moisture conditions in the region. Our data show that trees across the slide are in sync with respect to the stress response indicated by reaction wood. The magnitude of response to slope instability, as inferred from eccentric growth, has varied considerably across the site. We hypothesize that macropore development during the driest periods, and the differential rate at which water has reached subsurface failure planes, has caused the observed slope instability. The combination of a wetter precipitation regime and slope instability leads to higher sediment loads in the adjacent stream and serves as a useful analogy for similar watersheds in the region.     

Upper Triassic – Jurassic sequence stratigraphy and its structural controls in the western Ordos Basin, China

Upper Triassic, Lower–Middle Jurassic and Upper Jurassic strata in the western Ordos Basin of North China are interpreted as three unconformity-bounded basin phases, BP-4, BP-5 and BP-6, respectively. The three basin phases were deposited in three kinds of predominantly continental basin: (1) a Late Triassic composite basin with a south-western foreland subbasin and a north-western rift subbasin, (2) an Early–Middle Jurassic sag basin and (3) a Late Jurassic foreland molasse wedge. Within the Late Triassic composite basin BP-4 includes three sequences, S4-1, S4-2 and S4-3. In the south-western foreland subbasin, the three sequences are the depositional response to three episodes of thrust load subsidence, and are mainly composed of alluvial fan, steep-sloped lacustrine delta and fluvial systems in front of a thrust fault-bounded basin flank. In the north-western rift subbasin, the three sequences are the depositional response to three episodes of rift subsidence, and consist of alluvial fan – braid plain and fan delta systems basinward of a normal fault-bounded basin margin. In the sag basin BP-5 includes four sequences, S5-1, S5-2, S5-3 and S5-4, which reflect four episodes of intracratonic sagging events and mainly consist of fluvial, gentle-gradient lacustrine delta and lacustrine systems sourced from peripheral uplifted flanks. BP-6, deposited in the foreland-type basin, includes one sequence, S6-1, which is the depositional response to thrust load subsidence and is composed of alluvial fan systems. The formation and development of these three kinds of basins was controlled by Late Triassic and Jurassic multi-episode tectonism of basin-bounding orogenic belts, which were mainly driven by collision of the North China and South China blocks and subduction of the western Pacific plate.     

Exploring the causes of an extreme flood event in Central New York,USA

This study examined the causes of an extreme flood event on 28 June 2013 in Central New York, USA by comparing its hydrological, hydrometeorological, and rainfall-runoff transformation characteristics with those of a typical flood event. Flood frequency analyses showed that the maximum rainfall intensity and the peak discharge of the extreme event had recurrence intervals (RIs) of 8 and 86 years, respectively, while RIs for the typical event were 42 and 11 years, respectively. Their severity diagrams and quantification of their rainfall spatial variations illustrated that the extreme event was spatially localized with high intensities, whereas the typical event was spatially uniform and prolonged. Watershed modeling indicated that the rainfall-runoff transformation was dominated by the infiltration excess process for the extreme flood, while controlled by both infiltration and saturation excess processes for the typical event. These analyses revealed that the upgrade-magnitude conversion pattern of the extreme flood event was induced by the spatial pattern of the rainfall and the “lubricant” effect of the watershed, and emphasized the need for better understanding of such type of extreme events.     

Basin and petroleum system modelling of the East Coast Basin,New Zealand: a test of overpressure scenarios in a convergent margin

In the East Coast Basin (ECB), an active convergent margin of the North Island, New Zealand, the smectite‐rich Eocene Wanstead Formation forms an effective regional seal, creating high overpressure in the underlying Cretaceous through Palaeocene units due to disequilibrium compaction. This study examines the evolution of pore pressure and porosity in Hawke Bay of the ECB based on stepwise structural reconstruction of a stratigraphic and structural framework derived from interpretation of a regional two‐dimensional seismic line. This framework is incorporated into a basin and petroleum system model to predict the generation, distribution, and dissipation of overpressure, and examine the influence of faults, erosion, structural thickening, and seal effectiveness of the Wanstead Formation on pore pressure evolution. We find that natural hydraulic fracturing is likely occurring in sub‐Wanstead source rocks, which makes it a favourable setting for potential shale gas plays. We use poroelastic modelling to investigate the impact of horizontal bulk shortening due to tectonic compression on pore pressure and the relative order of principal stresses. We find that shortening modestly increases pore pressure. When 5% or greater shortening occurs, the horizontal stress may approach and exceed vertical stress in the last 4 Myr of the basin's history. Shortening impacts both the magnitude and relative order of principal stresses through geological time. Due to the overpressured nature of the basin, we suggest that subtle changes in stress regime are responsible for the significant changes in structural deformational styles observed, enabling compressional, extensional, and strike‐slip fault regimes to all occur during the tectonic history and, at times, simultaneously.     

New Silurian and Devonian palaeomagnetic results from the Hexi Corridor terrane, northwest China, and their tectonic implications

A total of 239 orientated drill-core samples from 23 sites were collected for palaeomagnetic study from Silurian and Devonian red beds, marlaceous sandstone, and limestone rocks in the eastern part of the Hexi Corridor, southwest Ningxia, North China. The characteristic high-temperature component resides in both haematite and magnetite. It clusters around a northwesterly and shallow to moderate downward direction and its antipode after tilt correction. The primary origin of this characteristic remanent magnetization (ChRM) is ascertained by positive fold and reversal tests at the 95 per cent confidence level. The corresponding palaeopoles, at 339.0°E, 60.1°N with A ₉₅ = 11.2° (Silurian) and 336.0°E, 56.0°N with A ₉₅ = 9.2° (Devonian), imply that the North China Block (NCB) had a low palaeolatitude of around 15°N in the Northern Hemisphere during the Silurian–Devonian period. Comparison with the Early–Middle Ordovician palaeopole of the NCB suggests that the NCB moved rapidly northwards by 30.8° ± 10.9° to cross the palaeo-equator during the Early–Middle Ordovician to Silurian. In combination with the palaeobiogeographical data from Ningxia, our palaeomagnetic results suggest that the NCB was located close to Australia during the Late Devonian.     

Post-Nipissing Origin of a Backdune Complex Along the Southeastern Shore of Lake Michigan

Relatively low (<25 m) parabolic dunes and dune ridges occur inland of massive parabolic dunes in many dune complexes along the southeastern shore of Lake Michigan. The major study of these backdunes (Tagues, 1946) concluded, based on field criteria, that they were older than the massive parabolic dunes and originate at the Calumet and Algonquin stages of ancestral Lake Michigan (~14-10 ka). Younger ages are indicated by this study in which Optically Stimulated Luminescense (OSL) ages were obtained from the crest of three backdunes southwest of Holland, Michigan. All ages are within statistical error of each other and indicate dune stabilization at ~4 ka. Similarities in surface soil development throughout the backdunes support the conclusion that they all stabilized at about the same time. Radiocarbon ages from paleosols indicate that the massive parabolic dunes were active at 4 ka and that this activity persisted after the back dunes had stabilized. In the Holland area, dune growth and migration occurred in a broad zone, including both back and massive parabolic dunes, immediately after the rise to and drop from Nipissing II high lake levels but became confined to a narrower zone closer to shore after ~4 ka.     

Clast Fabric in Relict Periglacial Colluvium, Salamanca Re-Entrant, Southwestern New York, USA

Samples of macrofabric data obtained from colluvial deposits near the late-Wisconsinan glacial margin display widely divergent characteristics. Those from highly weathered and jointed sandstone plot as girdle distributions. Samples from red colluvium of early-Wisconsinan age form moderately strong clusters. Fabrics from shallow depth in medium-textured brown colluvium of late-Wisconsinan age generally have modes aligned with the local slope but are weak, and appear to have been modified by frost heaving. Clasts in the basal layers of an overlying loess unit were emplaced by frost heaving from the brown colluvium and have very weak or uniform fabrics. Particle shape exerts an influence on fabric strength in the brown colluvium, with samples composed of more elongated clasts displaying stronger fabrics. Fabrics from near-surface deposits show generally weaker shape and strength characteristics and higher inclinations than those at depth. Calculated seasonal frost penetration is consistent with the depth to which weaker, more steeply inclined fabrics are found. Sampling in relict periglacial deposits should be performed only below the level of disturbance by seasonal frost.     

Anthropogenic impacts recorded in recent sediments from Otisco Lake,New York,USA

Geochemical analysis of ²¹⁰Pb-dated sediment cores from Otisco Lake (New York) combined with analysis of recent land cover change in the watershed revealed the history of land use change, lake management, and industrial pollution since European settlement in the northeastern US. Clearance of forestland for agriculture characterized the early settlement era that was marked in the Otisco Lake sediments by a decline in organic carbon (OC) and OC:N ratios, which indicate a change in the sources of organic matter to the lake. Agricultural land use reached its greatest areal extent in the Otisco watershed around 1900, followed by field abandonment and reforestation over the last century. In the 1920s sediment accumulation rates began to increase coincident with residential development along the lake shore. Nitrogen and organic carbon, which are transported from the watershed, show increased fluxes to the lake in response to this change. Deposition of inorganic carbon increased markedly over a short period from the 1940s to the 1980s, which is consistent with enhanced mobilization of watershed calcium by increased acidic deposition, followed by alkalinization of the lake waters and calcite precipitation. An increase in copper content in the sediments reflects application, since 1942, of the algicide copper sulfate to the lake waters to control algal blooms. This CuSO₄ marker confirmed the accuracy of the ²¹⁰Pb chronology. Atmospheric mercury (Hg) fluxes to the lake were affected by increased sediment transport from the watershed. The maximum Hg peak in the sediment record, however, was dated to the early 1970s and coincides with maximum Hg emissions to the atmosphere in the Great Lakes region.     

The Entrepreneurial City: Fabricating Urban Development in Syracuse,New York

This paper presents a case study of contemporary urban redevelopment in Syracuse, New York, within a theoretical framework drawn from urban political economy. Our analysis integrates the role of the local state in assuming the financial risk for a redevelopment project with an understanding of the meanings and role of a fabricated cultural landscape in ensuring the success of the project. We argue that the urban landscape is fundamentally embedded and implicated in the ongoing political economy of American urban places.     

Regional relief characteristics and denudation pattern of the western Southern Alps, New Zealand

The Southern Alps of New Zealand are the topographic expression of active oblique continental convergence of the Australian and Pacific plates. Despite inferred high rates of tectonic and climatic forcing, the pattern of differential uplift and erosion remains uncertain. We use a 25-m DEM to conduct a regional-scale relief analysis of a 250-km long strip of the western Southern Alps (WSA). We present a preliminary map of regional erosion and denudation by overlaying mean basin relief, a modelled stream-power erosion index, river incision rates, historic landslide denudation rates, and landslide density. The interplay between strong tectonic and climatic forcing has led to relief production that locally attains 2 km in major catchments, with mean values of 0.65–0.68 km. Interpolation between elevations of major catchment divides indicates potential removal of l0¹–10³ km³, or a mean basin relief of 0.51–0.85 km in the larger catchments. Local relief and inferred river incision rates into bedrock are highest about 50–67% of the distance between the Alpine fault and the main divide. The mean regional relief variability is ± 0.5 km.Local relief, valley cross-sectional area, and catchment width correlate moderately with catchment area, and also reach maximum values between the range front and the divide. Hypsometric integrals show scale dependence, and together with hypsometric curves, are insufficient to clearly differentiate between glacial and fluvial dominated basins. Mean slope angle in the WSA (ψ = 30°) is lower where major longitudinal valleys and extensive ice cover occur, and may be an insensitive measure of regional relief. Modal slope angle is strikingly uniform throughout the WSA (φ = 38–40°), and may record adjustment to runoff and landsliding. Both ψ and φ show non-linear relationships with elevation, which we attribute to dominant geomorphic process domains, such as fluvial processes in low-altitude valley trains, surface runoff and frequent landsliding on montane hillslopes, “relief dampening” by glaciers, and rock fall/avalanching on steep main-divide slopes.     

New dynamics of rent gap formation in New York City rent-regulated housing: privatization,financialization, and uneven development

ABSTRACT

To explain newfound investor interest in rent-regulated multifamily housing in New York City since 2001, this paper analyzes the transformation in ownership and management of the Riverton Houses, a large rent-regulated housing complex in northern Manhattan. The paper finds new dynamics of rent gap formation at work; rather than depressed capitalized rent attracting investment, increasing potential rent provides a new mechanism for opening rent gaps. The Riverton Houses case shows how three factors increase potentials rents: 1) changes in rent control law that provide new avenues to increase rents, 2) new financial actors and institutions that have higher expectations for risk and return, and 3) longer-term processes of uneven development at the urban scale. Altered rent gap dynamics under processes of privatization, financialization, and uneven urban development complicate the geography of reinvestment beyond a reinvested core and gentrifying periphery. Instead, the urban frontier is drawn recursively within urban space.