Variations In Uplift Rate Research Articles

Fracturing around magma reservoirs can explain variations in surface uplift rates even at constant volumetric flux

Many volcanoes show continuous but variable deformation over timescales of years to decades. Variations in uplift rate are typically interpreted as changes in magma supply rate and/or a viscoelastic response of the host rock. Here we conduct analogue experiments in the laboratory to represent the inflation of a silicic magma body at a constant volumetric flux, and measure the chamber pressure and resulting surface displacement field. We observe that dyke intrusions radiating from the magma body cause a decrease in the peak uplift rate, but do not significantly affect the spatial pattern of deformation or spatially averaged uplift rate. We identify 4 distinct phases: 1) elastic inflation of the chamber, 2) a gradual decrease in the rate of uplift and pressurisation, associated with the formation of visible cracks 3) propagation of a dyke by mode 1 failure at the crack tip and 4) a pressure decrease within the chamber. Phase 2 can be explained by either a) crack damage, which reduces the elastic moduli of the surrounding rock or b) magma filling pre-existing cracks. Thus these experiments provide alternative mechanisms to explain observed variations in uplift rate, with important implications for the interpretation of deformation patterns at volcanoes around the world.

Interactions between Cenozoic tectonics and landscape dynamics in Londrina, Paraná, Brazil

The Londrina City, located in southern Brazil, is situated on the basalt of the Paraná Igneous Province (PIP), near tectonic structures such as the Guaxupé faults and the São Jerônimo-Curiúva and São Sebastião lineaments, with a history of reactivation in the Cenozoic. Between 2015 and 2018, low-magnitude earthquakes hit the municipality, suggesting a possible connection with these structures. This study investigates the relationship between Cenozoic tectonics and geomorphological dynamics, combining quantitative geomorphological analysis with field analysis of faults. The results reveal signs of tectonic control on the landscape, with two pulses of regional uplift/base level drop affecting the drainage network. Reactivated segments, especially at intersections of NE and NW structures, influence dynamics, with variations in uplift rates between basins and block rotation under a transtensive regime. Recent earthquakes are related to the reactivation of an N50-60E fault scarp, possibly the Guaxupé Fault, indicating recurrent tectonic movement. Paleostress analyses identify three deformation pulses, highlighting the complexity of landscape evolution in intraplate regions. These findings enhance understanding of regional tectonics, emphasizing the need to comprehend landscape evolution in interior plate areas, such as the South American Plate.

Detrital zircon U[sbnd]Pb geochronology of modern river sediment in the Eastern Pamir Syntaxis and its implications for the formation of the Pamir and growth of the Tibetan Plateau

The Eastern Pamir Syntaxis links the western Tibetan Plateau with the western syntaxis of the Himalayan-Tibetan orogen. Quantifying temporal and spatial variations in uplift rates for the Eastern Pamir Syntaxis is critical for understanding the growth of the Himalayan-Tibetan orogen. To better understand these variations, we report n = 285 new detrital zircon UPb ages from sediments in modern rivers of the Eastern Pamir Syntaxis. When compared with previous work, our data, with a major age mode around ∼107 Ma, indicate that siliciclastic sediments in the Taxkorgan River were primarily derived from Cretaceous rocks. Whereas a less prominent age mode around ∼13 Ma suggests that Miocene rocks made an important sediment contribution to the Taxkorgan River. The other notable age modes are in the range of 200–300 Ma and 600–800 Ma. Our data suggest that detrital zircon UPb signatures for rivers draining the Eastern Pamir Syntaxis change significantly from south to north, and the influence of Cretaceous proto-sources gradually diminishes northward. Because Tibetan sutures are traceable into the Pamir, these data help define the distribution of late Early Cretaceous rocks associated with the closure of the Meso-Tethys within the Pamir. These data support the establishment of the modern-like river pattern in the Eastern Pamir Syntaxis contemporaneous with activity on the Kongur Extensional System in the northeast Pamir.

Differential coastal uplift quantified by luminescence dating of marine terraces, central Cascadia forearc, Oregon

Flights of marine terraces along the coastline of the Cascadia convergent margin record long-term, sustained crustal uplift of the subduction zone upper plate. At Yaquina Bay (Newport, Oregon) differences in the elevations of previously inferred MIS 5 (5a, 5c, and 5e) marine terraces north and south of the bay imply differences in the long-term uplift rate that are attributed to displacement along the Yaquina Bay fault – a west-to-east trending fault inferred to be located within the bay. Here we present the first direct ages for the marine terrace deposits at Yaquina Bay using luminescence dating of marine terrace sands on terrace treads to quantify long-term and interval uplift rates. These new age results in combination with high-resolution topographic data, allow us to refine previous mapping of marine terraces in the vicinity of Yaquina Bay, including the recognition of a MIS 5a terrace south of Yaquina Bay. Differences in the elevations of terraces north and south of Yaquina Bay confirm relative displacement along the Yaquina Bay fault since the late Pleistocene. Our results imply differences in the long-term uplift rate relative to sea level north and south of Yaquina Bay since ca. 125 ka; south of the fault, uplift rates appear to have been relatively constant at 0.3–0.4 m/kyr, whereas north of the fault, average uplift rates were greater, 0.7–0.9 m/kyr over the past ca. 125 kyrs. Notably, terrace elevations north of the fault require variations in uplift rate through time. Uplift rates appear to have been relatively low (≤0.1 m/kyr) between MIS 5e and 5c but increased to rates of ∼1.6 m/kyr in a ∼20 kyr period between MIS 5c and MIS 5a. Subsequently, uplift rates appear to have decreased to 0.7 m/kyr during the last ∼80 kyrs, but were sustained at rates approximately double that of the block south of the fault. These results require temporally variable slip along the Yaquina Bay fault since the late Pleistocene.

Global dominance of tectonics over climate in shaping river longitudinal profiles

River networks are striking features engraved into Earths surface, shaped by uplift and erosion under the joint influence of climate and tectonics. How a river descends along its course – its longitudinal profile – varies greatly from one basin to the next, reflecting the interplay between uplift and erosional processes. It has recently been argued that climatic aridity should be a first-order control on river profile concavity, but the importance of climate relative to other factors has not been tested at global scale. Here we show, using recent global datasets of river profiles and tectonic activity, that tectonics is much more strongly expressed than climate in global patterns in river profile concavity. River profiles tend to be more strongly concave in tectonically active regions along plate boundaries, reflecting tectonically induced spatial variations in uplift rates. Rank correlations between river profile concavity and global tectonic proxies (basin slope and two indices of seismic risk) are much stronger than those between river concavity and precipitation, potential evapotranspiration, or aridity. These results show that tectonics, and not climate, exerts first-order control on the shape of river longitudinal profiles globally.

Variable Quaternary Uplift Along the Southern Margin of the Central Anatolian Plateau Inferred From Modeling Marine Terrace Sequences

AbstractThe southern margin of the Central Anatolian Plateau (CAP) records a strong uplift phase after the early Middle Pleistocene, which has been related to the slab break‐off of the subducting Arabian plate beneath the Anatolian microplate. During the last 450 kyr the area underwent an uplift phase at a mean rate of ~3.2 m/kyr, as suggested by Middle Pleistocene marine sediments exposed at ~1,500 m above sea level. These values are significantly higher than the 1.0–1.5 m/kyr estimated since the Late Pleistocene, suggesting temporal variations in uplift rate. To estimate changes in uplift rate during the Pleistocene we studied the marine terraces along the CAP southern margin, mapping the remnants of the platforms and their associated deposits in the field, and used the TerraceM software to identify the position and elevation of associated shoreline angles. We used shoreline angles and the timing of Quaternary marine sedimentation as constrains for a Landscape Evolution Model that simulates wave erosion of an uplifting coast. We applied random optimization algorithms and minimization statistics to find the input parameters that better reproduce the morphology of CAP marine terraces. The best‐fitting uplift rate history suggests a significative increase from 1.9 to 3.5 m/kyr between 500 and 200 kyr, followed by an abrupt decrease to 1.4 m/kyr until the present. Our results agree with slab break‐off models, which suggest a strong uplift pulse during slab rupture followed by a smoother decrease.

Geodetic Observations of Time‐Variable Glacial Isostatic Adjustment in Southeast Alaska and Its Implications for Earth Rheology

AbstractGlobal Positioning System observations in Southeast Alaska show evidence for interannual variations in uplift rates, which are consistent with an acceleration of mass loss rates across the region from the 1990s to 2012. We constructed an updated regional loading model based on updated twentieth century average deglaciation estimates. This model features a larger mass loss rate overall than the model used in previous studies. We adopted a viscosity model with an upper and lower mantle viscosity from VM5a but with a low viscosity asthenosphere as in previous regional studies. We varied the asthenospheric thickness, asthenospheric viscosity, and lithospheric thickness to find the Earth model that best fits the data, which has a lithospheric thickness of 55 km and an asthenosphere with thickness 230 km and viscosity 3 × 1019 Pa s. There is a strong tradeoff between the asthenosphere thickness and viscosity, and different estimates or assumptions about the asthenospheric thickness is one of the main causes of the varying viscosity estimates of previous studies. We find a higher viscosity than previous studies in part because we find that a thicker asthenosphere fits the data better than a thinner one and also because the higher twentieth century mass loss rate compared to earlier studies requires a higher viscosity to predict the same uplift rates. Vertical velocities predicted by the model drop rapidly with distance from the ice masses, while horizontal velocities are smaller but extend for a longer distance.

Spatial distribution pattern of channel steepness index as evidence for differential rock uplift along the eastern Altun Shan on the northern Tibetan Plateau

Abstract The eastern Altun Shan is a crucial part of the Altun orogenic belt within the Tibetan Plateau. Study of the uplift rate and the related features in this area provides important clues for understanding the uplift mechanism of the Tibetan Plateau as a whole. As an important geomorphic element in landscape development, the fluvial system can record the relationship between tectonic activity and climatic change. In recent years, studies of the Channel Steepness Index Ksn, have been conducted by many researchers, using the geomorphological model of equilibrium channel longitudinal profiles, combining bedrock uplift and river incision and thus making it possible to extract rock uplift history from river profiles. This research show that regional rock uplift rate is a major factor in affecting the Ksn index. Regional tectonic activity and intensity, therefore, can be evaluated from variation in the Ksn index, which can provide a sensitive measure of uplift rate. In this paper, the Digital Elevation Map ‘ASTER GDEM’, with a spatial resolution of 30 m, was utilized as basic data, and combined with ArcGIS and MATLAB software to extract the Ksn index from the equilibrium channel longitudinal profiles model. Meanwhile, we employed statistical methods to analyze the Ksn index. Our results suggest that averaged Ksn indices, obtained from the subrange A，B，C，D, and E of the eastern Altun Shan (from west to east), are 70.93, 139.03, 108.85, 134.44 and 165.39, respectively. Further analysis implies that the variation in this index can be correlated with the distribution pattern of uplift rates within different regions. Its value increases gradually from west to east, reflecting regional uplift rate. Along the western section of the eastern Altun Shan, the uplift rate is slower and characterized by strike-slip movements, while its eastern part has uplifted faster and is controlled by thrust fault systems. Moreover, in contrast with the southern Altun Shan, the uplift rate of the northern part is high. These variations in uplift rate seem to be linked with “the imbricated thrusting transformation-limited extrusion model” of the Tibetan Plateau. Our results can be correlated with previous work on the active characteristics along the eastern Altyn Tagh Fault (ATF).

Clustering River Profiles to Classify Geomorphic Domains

The structure and organization of river networks has been used for decades to investigate the influence of climate and tectonics on landscapes. The majority of these studies either analyze rivers in profile view by extracting channel steepness or calculate planform metrics such as drainage density. However, these techniques rely on the assumption of homogeneity: that intrinsic and external factors are spatially or temporally invariant over the measured profile. This assumption is violated for the majority of Earth's landscapes, where variations in uplift rate, rock strength, climate, and geomorphic process are almost ubiquitous. We propose a method for classifying river profiles to identify landscape regions with similar characteristics by adapting hierarchical clustering algorithms developed for time series data. We first test our clustering on two landscape evolution scenarios and find that we can successfully cluster regions with different erodibility and detect the transient response to sudden base level fall. We then test our method in two real landscapes: first in Bitterroot National Forest, Idaho, where we demonstrate that our method can detect transient incision waves and the topographic signature of fluvial and debris flow process regimes; and second, on Santa Cruz Island, California, where our technique identifies spatial patterns in lithology not detectable through normalized channel steepness analysis. By calculating channel steepness separately for each cluster, our method allows the extraction of more reliable steepness metrics than if calculated for the landscape as a whole. These examples demonstrate the method's ability to disentangle fluvial morphology in complex lithological and tectonic settings.

The evolution of Chabahar beach ridge system in SE Iran in response to Holocene relative sea level changes

The Chabahar Strandplain (CHS) stretches along the Chabahar bay at a width of more than 5 km along the northern coast of the Gulf of Oman and SE Iran; an area that has been subjected to tectonic uplift as a part of the Makran accretionary prism. The CHS comprises of beach ridges, inter-ridge swales, sand dunes, tidal channels and fluvial deposits. We present the first documentation of the spatial distribution and the internal architecture of the CHS based on topographic surveys, sediment percussive coring, trenching and ground penetrating radar (GPR) transects. Radiocarbon dating on marine shells from foreshore deposits of 8 representative beach ridges yielded ages between 4800 and 270 cal. years BP at respective distances of 4800 to 670 m from the present shoreline. We interpret the boundary between the foreshore (beach) and the foredune deposits as indicator of past sea levels by analogy to present shore processes. This boundary is readily recognizable in sediment profiles from cores and trenches as well as GPR reflectors. Based on the age model and depositional features, we estimate relative sea level fall of up to 15 m over the past 4800 years. Considering that the eustatic sea level changes for this period are negligible for the Makran coast, this relative sea level fall is related to tectonic uplift across the coastal Makran. The elevation of palaeo-shorelines with similar ages decrease from east to west of the CHS, which suggest that alongshore variations in uplift rates are likely related to different movements of coastal fault blocks.

Variations in the long-term uplift rate due to the Altiplano–Puna magma body observed with Sentinel-1 interferometry

We present new Interferometric Synthetic Aperture Radar (InSAR) observations of surface deformation in the Altiplano–Puna region (South America) where previous studies documented a broad uplift at an average rate of ∼10 mm/yr. We use data from the Sentinel-1 satellite mission to produce high-resolution velocity maps and time series of surface displacements between years 2014–2017. The data reveal that the uplift has slowed down substantially compared to the 1992–2010 epoch and is characterized by short-term fluctuations on time scales of months to years. The observed variations in uplift rate may indicate a non-steady supply of melt and/or volatiles from the partially molten Altiplano–Puna Magma Body (APMB) into an incipient diapir forming in the roof of the APMB.

Morphotectonics in a low tectonic rate area: Analysis of the southern Portuguese Atlantic coastal region

South Portugal is characterized by low tectonic rates (<0.3 mm/a), with infrequent large seismicity. Recent studies indicate a coastal region in southwest Portugal uplifting at higher rates (0.11 ± 0.01 mm/a) than the remaining southern portion of Portugal (~0.04 mm/a); however, the mechanisms that drive this uplift are poorly understood. With the purpose of investigating the regional Quaternary deformation and its patterns, as well as the difference in the uplift rate, 77 exorheic drainage basins along 460 km of the southern Portuguese coastline were analysed through the application of geomorphic indices. In this study we applied stream channel sinuosity S, basin relief ratio Rh, elongation Re, basin shape ratio Bs, valley height-width ratio Vf, basin asymmetry factor AF, hypsometry HI and, the stream-length gradient index SL, and we propose the terminal basin shape index TBS. This study aims to (1) identify Quaternary deformation along presumed tectonic structures; (2) recognize uplift or subsidence along the coastline; and (3) test the application of geomorphic indices in low deformation rate environments. The cross-correlation of results led to the recognition of the São Teotónio-Aljezur-Sinceira fault system and the São Marcos-Quarteira Fault as major regional Quaternary faults, as well as to the interpretation of Quaternary activity for other structures. Spatial differences in uplift rates are identified through basin shape indices and valley height-width ratios, even for low vertical motion rates, whereas other indices were found to be not as sensitive to variations in uplift rate.

Cosmogenic Be and OSL Dating of Marine Terraces Along the Central- East Coast of Korea: Spatio-Temporal Variations in Uplift Rates

We report the abandonment age of the Jeongdongjin (JDJ) coastal terrace that lies at 65 m a.s.l. The age of the JDJ terrace surface has yet to be equivocally constrained because of its antiquity (>MIS 5), challenging the application of conventional radiocarbon and optically stimulated luminescence (OSL) dating techniques. The reliability of applied indirect age constraints on the sediments by amino-acid racemization and tephra chronology is debated. We present the first application of cosmogenic surface exposure dating to constrain the age of the old terrace in Korea. We dated four samples from the paleo shore platform surface using cosmogenic 10 Be surface exposure dating techniques. The analyses yielded exposure ages ranging from 240 to 170 kyr and likely correspond to the penultimate interglacial period (MIS 7). Sandy beach sediments overlying marine terraces at nearby Anin (~23 m a.s.l.) and Ayajin (~17 m a.s.l.) were dated by OSL. OSL dating of terrace beach sand in two separate areas yielded ages between 129-117 and 70-66 kyr, interpreted MIS 5e and MIS 5a, respectively. Combining the exposure ages and the heights of terraces corrected for paleo sea level, we obtain uplift rates of 353 for JDJ, 159 for Anin, and 238 mm/kyr for Ayajin. The results indicate spatio-temporal variations in the rate of surface uplift along the east coast of Korea during the late Quaternary. Furthermore, the west and east coasts of central Korea experienced different uplift histories during the late Quaternary, possibly resulting from the effects of different tectonic regimes.

Geologic controls on bedrock channel width in large, slowly-eroding catchments: Case study of the New River in eastern North America

We have investigated the geologic controls on hydraulic geometry of bedrock rivers using a single large catchment, the New River, from a stable tectonic setting with variable, resistant lithology but spatially stable climate. Our survey of channel width at 0.5km spacing along 572km of the river shows major variation that only roughly fits the expected scaling relationships between width, drainage area, and slope. Considerable variations in width, including steps in trends and large spikes, relate to physiogeologic boundaries that the river passes through. A large fraction (15%) of the river's length classifies as bedrock reach, showing that it behaves more like a bedrock river than an alluvial river. Unlike established trends, the channel is wider in bedrock than in alluvium. Field observations show that aspect ratio (width to depth) is not constant, but fluctuates systematically with width from wide, shallow reaches to narrower, deeper reaches. Our observations of bedrock properties suggest that susceptibility to fluvial plucking versus abrasion may control this anomalous channel morphology. One end member form with aspect ratio as high as 500, which we term the incision plain, is associated with very closely spaced discontinuities (~10cm) in otherwise hard rock. We propose that the closely spaced discontinuities enable efficient plucking that leads to widening by lateral erosion. This morphology locally occurs in other passive margin rivers and may be a fundamental fluvial form that is similar to, but the inverse of, slot canyons. The other end member, which we term channel neck, is narrower and deeper with complex flow paths through blocky bedrock. This form occurs where discontinuity spacing is longer (>0.5m) and erosion is abrasion dominated. These results imply that changes in channel width do not necessarily reflect variations in uplift rate, but instead may result from complex response to bedrock properties.

Erosion of a tectonically uplifting coastal landscape, NE Sicily, Italy

We investigate the relative importance of tectonic uplift, climate, and bedrock resistance as controls upon channel morphology in the active orogen of NE Sicily. The study area displays spatial variations in uplift rate, precipitation, and bedrock resistance. The significance of each of these gradients was tested using established morphometric relationships. Twenty catchments were investigated using the 28-m Aster digital elevation model (DEM) for longitudinal profile analysis, Google EarthTM to determine channel widths, and Schmidt Hammer readings to quantify bedrock strength. Based on channel morphologies and hillslope gradients, the basins exhibit three distinct reaches: upper, middle, and lower. The upper reaches of the bedrock channels display concave longitudinal profiles, positive correlation between uplift rate and steepness, and exponents in the width–area relationship of 0.4–0.5, indicating that uplift is the major control on the morphology of this reach. The middle reaches, however, display sublinear longitudinal profiles, weak correlation between uplift rate and channel steepness, and no systematic width–area relationship. We interpret this to be caused by the presence of a shear zone, which, through fracturing, has tectonically increased the bedrock erodibility, irrespective of its lithology. In the lower reaches, the channels are alluvial. Neither channel concavity nor steepness seems to be affected by the spatial variation in precipitation in any of the reaches, indicating that climate does not noticeably affect channel morphology. These observations suggest a strong tectonic influence on channel evolution in this active mountainous region. Our study illustrates how reach-scale morphometric analysis can aid understanding of how fluvial systems vary with potential controlling parameters.

Tectonic and climatic controls of denudation rates in active orogens: The San Bernardino Mountains, California

The relative importance of climatic and tectonic factors in driving rates of denudation in mountain ranges has long been debated, with both precipitation and rates of crustal uplift cited as first order controls in a variety of different mountainous settings. Few studies, however, have explicitly considered the influence of climatic and tectonic processes on denudation rates during the early stages of orogenesis. Using basin-wide denudation rates derived from in-situ cosmogenic 10Be, and published modern precipitation rate data, the significance of rainfall and snowfall on rates of denudation is evaluated for the San Bernardino Mountains, California. Denudation rates vary between 52 mm ka − 1 in the arid northern regions of the mountains and 2700 mm ka − 1 in the more humid southern sector. We select three basins where the influence of precipitation on denudation rates can be isolated from the effects of crustal uplift and find that there is no apparent relationship between denudation rates and precipitation. Denudation rates differ more than five-fold on the opposing slopes of Mill Creek, a valley bisected by a major splay of the San Andreas Fault, and we propose that this denudation rate disparity can be best explained by variations in uplift rates across the fault. The results suggest that crustal uplift is the mechanism that underpins the ∼ 50-fold variability in denudation rates we have measured in the San Bernardino Mountains, but that this must be facilitated by sufficient precipitation to remove valley-fill deposits.

Late Cenozoic uplift of western Turkey: Improved dating of the Kula Quaternary volcanic field and numerical modelling of the Gediz River terrace staircase

A set of 13 new unspiked K–Ar dates has been obtained for the Quaternary basaltic volcanism in the Kula area of western Turkey, providing improved age control for the fluvial deposits of the Gediz River that underlie these basalt flows. This dating is able, for the first time, to resolve different ages for the oldest basalts, assigned to category β2, that cap the earliest Gediz deposits recognised in this area, at altitudes of ∼140 to ∼210 m above present river level. In particular, the β2 basalt capping the Sarnıç Plateau is dated to 1215 ± 16 ka (± 2 σ), suggesting that the youngest underlying fluvial deposits, ∼185 m above present river level, are no younger than marine oxygen isotope stage (MIS) 38. In contrast, the β2 basalt capping the adjacent Burgaz Plateau is dated to 1014 ± 23 ka, suggesting that the youngest underlying fluvial deposits, ∼140 m above present river level, date from MIS 28. The staircase of 11 high Gediz terraces capping the latter plateau is thus dated to MIS 48-28, assuming they represent consecutive ∼40 ka Milankovitch cycles, although it is possible that as many as two cycles are missing from this sequence such that the highest terrace is correspondingly older. Basalt flows assigned to the β3 category, capping Gediz terraces ∼35 and ∼25 m above the present river level, have been dated to 236 ± 6 ka and 180 ± 5 ka, indicating incision rates of ∼0.15 mm a − 1 , similar to the time-averaged rates since the eruptions of the β2 basalts. The youngest basalts, assigned to category β4, are Late Holocene; our K–Ar results for them range from zero age to a maximum of 7 ± 2 ka. This fluvial incision is interpreted using numerical modelling as a consequence of uplift caused by a regional-scale increase in spatial average erosion rates to ∼0.1 mm a − 1 , starting at ∼3100 ka, caused by climate deterioration, since when a total of ∼410 m of uplift has occurred. Parameters deduced on this basis from the observed disposition of the Early Pleistocene Gediz terraces include the local effective viscosity of the lower crust, which is ∼2 × 10 18 Pa s, the Moho temperature of ∼660 °C, and the depth of the base of the brittle upper crust, which is ∼13 km. The thin lithosphere in this area results in high heat flow, causing this relatively shallow base of the brittle upper crust and the associated relatively thick lower-crustal layer, situated between depths of ∼13 and ∼30 km. It estimated that around 900 ka, at the start of the ∼100 ka Milankovitch forcing, the spatial average erosion rate increased slightly, to ∼0.12 mm a − 1 ; the associated relatively sluggish variations in uplift rates are as expected given the relatively thick lower-crustal layer. This modelling indicates that the growth of topography since the Pliocene in this study region has not involved a steady state. The landscape was significantly perturbed by the Middle Pliocene increase in erosion rates, and has subsequently adjusted towards—but not reached—a new steady state consistent with these increased erosion rates. It would not be possible to constrain what has been occurring from the Middle to Late Pleistocene or even the Early Pleistocene uplift response alone; information regarding the starting conditions is also essential, this being available in this region from the older geological record of stacked fluvial and lacustrine deposition. This result has major implications for the rigorous modelling of uplift histories in regions of rapid erosion, where preservation of information to constrain the starting conditions is unlikely.

Rock mass ratings (RMRs) predicted from slope angles of natural rock outcrops

We investigate the relative importance of tectonic uplift, climate, and bedrock resistance as controls upon channel morphology in the active orogen of NE Sicily. The study area displays spatial variations in uplift rate, precipitation, and bedrock resistance. The significance of each of these gradients was tested using established morphometric relationships. Twenty catchments were investigated using the 28-m Aster digital elevation model (DEM) for longitudinal profile analysis, Google EarthTM to determine channel widths, and Schmidt Hammer readings to quantify bedrock strength. Based on channel morphologies and hillslope gradients, the basins exhibit three distinct reaches: upper, middle, and lower. The upper reaches of the bedrock channels display concave longitudinal profiles, positive correlation between uplift rate and steepness, and exponents in the width–area relationship of 0.4–0.5, indicating that uplift is the major control on the morphology of this reach. The middle reaches, however, display sublinear longitudinal profiles, weak correlation between uplift rate and channel steepness, and no systematic width–area relationship. We interpret this to be caused by the presence of a shear zone, which, through fracturing, has tectonically increased the bedrock erodibility, irrespective of its lithology. In the lower reaches, the channels are alluvial. Neither channel concavity nor steepness seems to be affected by the spatial variation in precipitation in any of the reaches, indicating that climate does not noticeably affect channel morphology. These observations suggest a strong tectonic influence on channel evolution in this active mountainous region. Our study illustrates how reach-scale morphometric analysis can aid understanding of how fluvial systems vary with potential controlling parameters.

Tectonics of the Neogene Cascadia forearc basin: Investigations of a deformed late Miocene unconformity

Research Article| August 01, 2000 Tectonics of the Neogene Cascadia forearc basin: Investigations of a deformed late Miocene unconformity Lisa C. McNeill; Lisa C. McNeill 1School of Earth Sciences, University of Leeds, Leeds LS2 9JT, UK Search for other works by this author on: GSW Google Scholar Chris Goldfinger; Chris Goldfinger 2College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, Oregon 97331, USA Search for other works by this author on: GSW Google Scholar LaVerne D. Kulm; LaVerne D. Kulm 2College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, Oregon 97331, USA Search for other works by this author on: GSW Google Scholar Robert S. Yeats Robert S. Yeats 3Department of Geosciences, Wilkinson Hall, and College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, Oregon 97331, USA Search for other works by this author on: GSW Google Scholar Author and Article Information Lisa C. McNeill 1School of Earth Sciences, University of Leeds, Leeds LS2 9JT, UK Chris Goldfinger 2College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, Oregon 97331, USA LaVerne D. Kulm 2College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, Oregon 97331, USA Robert S. Yeats 3Department of Geosciences, Wilkinson Hall, and College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, Oregon 97331, USA Publisher: Geological Society of America Received: 23 Nov 1998 Revision Received: 12 Jul 1999 Accepted: 04 Aug 1999 First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (2000) 112 (8): 1209–1224. https://doi.org/10.1130/0016-7606(2000)112<1209:TOTNCF>2.0.CO;2 Article history Received: 23 Nov 1998 Revision Received: 12 Jul 1999 Accepted: 04 Aug 1999 First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Lisa C. McNeill, Chris Goldfinger, LaVerne D. Kulm, Robert S. Yeats; Tectonics of the Neogene Cascadia forearc basin: Investigations of a deformed late Miocene unconformity. GSA Bulletin 2000;; 112 (8): 1209–1224. doi: https://doi.org/10.1130/0016-7606(2000)112<1209:TOTNCF>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract The continental shelf and upper slope of the Oregon Cascadia margin are underlain by an elongate late Cenozoic forearc basin, correlative to the Eel River basin of northern California. Basin stratigraphy includes a regional late Miocene unconformity that may coincide with a worldwide hiatus ca. 7.5–6 Ma (NH6). The unconformity is angular and probably subaerially eroded on the inner and middle shelf, whereas the seaward correlative disconformity may have been produced by submarine erosion; alternatively, this horizon may be conformable. Tectonic uplift resulting in subaerial erosion may have been driven by a change in Pacific and Juan de Fuca plate motion. A structure contour map of the deformed unconformity and correlated seaward reflector from seismic reflection data clearly outlines deformation into major synclines and uplifted submarine banks. Regional margin-parallel variations in uplift rates of the shelf unconformity show agreement with coastal geodetic rates.The shelf basin is bounded to the west by a north-south–trending outer arc high. Rapid uplift and possible eustatic sea-level fall resulted in the formation of the late Miocene unconformity. Basin subsidence and outer arc high uplift effectively trapped sediments within the basin, which resulted in a relatively starved abyssal floor and narrower Pliocene accretionary wedge, particularly during sea-level highstands. During the Pleistocene, the outer arc high was breached, possibly contributing to Astoria Canyon incision, the primary downslope conduit of Columbia River sediments. This event may have caused a change in sediment provenance on the abyssal plain ca. 1.3–1.4 Ma. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Tectonics of the Neogene Cascadia forearc basin: Investigations of a deformed late Miocene unconformity

Research Article| August 01, 2000 Tectonics of the Neogene Cascadia forearc basin: Investigations of a deformed late Miocene unconformity Lisa C. McNeill; Lisa C. McNeill 1School of Earth Sciences, University of Leeds, Leeds LS2 9JT, UK Search for other works by this author on: GSW Google Scholar Chris Goldfinger; Chris Goldfinger 2College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, Oregon 97331, USA Search for other works by this author on: GSW Google Scholar LaVerne D. Kulm; LaVerne D. Kulm 2College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, Oregon 97331, USA Search for other works by this author on: GSW Google Scholar Robert S. Yeats Robert S. Yeats 3Department of Geosciences, Wilkinson Hall, and College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, Oregon 97331, USA Search for other works by this author on: GSW Google Scholar GSA Bulletin (2000) 112 (8): 1209–1224. https://doi.org/10.1130/0016-7606(2000)112<1209:TOTNCF>2.0.CO;2 Article history received: 23 Nov 1998 rev-recd: 12 Jul 1999 accepted: 04 Aug 1999 first online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation Lisa C. McNeill, Chris Goldfinger, LaVerne D. Kulm, Robert S. Yeats; Tectonics of the Neogene Cascadia forearc basin: Investigations of a deformed late Miocene unconformity. GSA Bulletin 2000;; 112 (8): 1209–1224. doi: https://doi.org/10.1130/0016-7606(2000)112<1209:TOTNCF>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract The continental shelf and upper slope of the Oregon Cascadia margin are underlain by an elongate late Cenozoic forearc basin, correlative to the Eel River basin of northern California. Basin stratigraphy includes a regional late Miocene unconformity that may coincide with a worldwide hiatus ca. 7.5–6 Ma (NH6). The unconformity is angular and probably subaerially eroded on the inner and middle shelf, whereas the seaward correlative disconformity may have been produced by submarine erosion; alternatively, this horizon may be conformable. Tectonic uplift resulting in subaerial erosion may have been driven by a change in Pacific and Juan de Fuca plate motion. A structure contour map of the deformed unconformity and correlated seaward reflector from seismic reflection data clearly outlines deformation into major synclines and uplifted submarine banks. Regional margin-parallel variations in uplift rates of the shelf unconformity show agreement with coastal geodetic rates.The shelf basin is bounded to the west by a north-south–trending outer arc high. Rapid uplift and possible eustatic sea-level fall resulted in the formation of the late Miocene unconformity. Basin subsidence and outer arc high uplift effectively trapped sediments within the basin, which resulted in a relatively starved abyssal floor and narrower Pliocene accretionary wedge, particularly during sea-level highstands. During the Pleistocene, the outer arc high was breached, possibly contributing to Astoria Canyon incision, the primary downslope conduit of Columbia River sediments. This event may have caused a change in sediment provenance on the abyssal plain ca. 1.3–1.4 Ma. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.