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Intermontane basins are illuminating stratigraphic archives of uplift, denudation and environmental conditions within the heart of actively growing mountain ranges. Commonly, however, it is difficult to determine from the sedimentary record of an individual basin whether basin formation, aggradation and dissection were controlled primarily by climatic, tectonic or lithological changes and whether these drivers were local or regional in nature. By comparing the onset of deposition, sediment-accumulation rates, incision, deformation, changes in fluvial connectivity and sediment provenance in two interrelated intermontane basins, we can identify diverse controls on basin evolution. Here, we focus on the Casa Grande basin and the adjacent Humahuaca basin along the eastern margin of the Puna Plateau in northwest Argentina. Underpinning this analysis is the robust temporal framework provided by U-Pb geochronology of multiple volcanic ashes and our new magnetostratigraphical record in the Humahuaca basin. Between 3.8 and 0.8 Ma, ~120 m of fluvial and lacustrine sediments accumulated in the Casa Grande basin as the rate of uplift of the Sierra Alta, the bounding range to its east, outpaced fluvial incision by the Río Yacoraite, which presently flows eastward across the range into the Humahuaca basin. Detrital zircon provenance analysis indicates a progressive loss of fluvial connectivity from the Casa Grande basin to the downstream Humahuaca basin between 3 and 2.1 Ma, resulting in the isolation of the Casa Grande basin from 2.1 Ma to

Geodetic and seismologic studies support a tectonic model for the central Himalaya wherein ~2 cm/yr of Indo-Asian convergence is accommodated along the primary d�collement under the range, the Main Himalayan thrust. A steeper midcrustal ramp in the Main Himalayan thrust is commonly invoked as driving rapid rock uplift along a range-parallel band in the Greater Himalaya. This tectonic model, developed primarily from studies in central Nepal, is commonly assumed to project along strike with little lateral variation in Main Himalayan thrust geometry or associated rock uplift patterns. Here, we synthesize multiple lines of evidence for a major discontinuity in the Main Himalayan thrust in western Nepal. Analysis of topography and seismicity indicates that west of ~82.5�E, the single band of steep topography and seismicity along the Main Himalayan thrust ramp in central Nepal bifurcates around a high-elevation, low-relief landscape, resulting in a two-step topographic front along an ~150 km segment of the central Himalaya. Although multiple models could explain this bifurcation, the full suite of data appears to be most consistent with a northward bend to the Main Himalayan thrust ramp and activation of a young duplex horse to the south. This poorly documented segmentation of the Main Himalayan thrust has important implications for the seismogenic potential of the western Nepal seismic gap and for models of the ongoing evolution of the orogen.

Fold scarps, a type of geomorphic scarp formed by folding mechanisms of hinge migration or limb rotation, serve to delineate both fault-bend characteristics and folding histories, which can, in turn, illuminate tectonic processes and seismic hazards associated with thrust systems. Because the subsurface geometry of folds is commonly difficult to determine, existing fold-scarp models, which rely on both the fold type and its causative fault geometries, remain uncertain with respect to the kinematic evolution of a given fold. In this paper, we develop a model to illustrate that, irrespective of specific fold type and subsurface geometries, fold-scarp growth in the mechanism of hinge migration can be successfully reconstructed based on analyses of bed geometry. This model reveals that the underlying bed dips and the ratio of hinge migration distance/hinge width control the fold-scarp shape and slope. During initial growth (ratio1), the slope reaches a maximum, which solely depends on underlying bed dips. The scarp height, however, is independent of the hinge width and can be used to quantify folding magnitude. Application of our model to fold scarps in the Mingyaole anticline in the southern foreland of Chinese Tian Shan indicates that the modeled fold-scarp geometry can roughly match with field observations. The Mingyaole shortening rate is estimated to be ≥5.0 mm/a since ~15ka, such that this single fold has accommodated about half of the regional convergence during the Holocene. Key Points Folding through curved hinges creates a distinctive fold-scarp geometry Scarp slope relies on ratio of hinge migration/width, but scarp height is not Shortening rate of the Mingyaole fold is estimated to be ~5.0 mm/a since ~15 ka, such that this single fold has accommodated about half of the regional convergence during the Holocene.

The flexural-slip fault (FSF), a type of secondary fault generated by bed-parallel slip, occurs commonly and plays an important role in accommodating fold growth. Although the kinematics and mechanics of FSFs are well studied, relatively few field observations or geometric models explore its geomorphic expression. In the Pamir-Tian Shan convergent zone, NW China, suites of well-preserved FSF scarps displace fluvial terraces in the Mingyaole and Wulagen folds. Integrating interpretations of Google Earth images, detailed geologic and geomorphic mapping, and differential GPS measurements of terrace surfaces, we summarize geomorphic features that typify these faults and create kinematic models of active flexural-slip faulting. Our study indicates the following: (i) FSF scarps commonly occur near synclinal hinges, irrespective of whether (a) the dip direction of beds on either side of the hinge is unidirectional or in opposite directions, (b) the hinge is migrating or fixed, or (c) the hinge shape is narrow and angular or wide and curved. (ii) Active FSFs are likely to produce higher scarps on steeper beds, whereas lower or no topographic scarps typify gentler beds. (iii) Tilt angles of the terrace surface displaced above FSFs progressively decrease farther away from the hinge, with abrupt changes in slope coinciding with FSF scarps; the changes in tilt angle and scarp height have a predictable geometric relationship. (iv) Active FSFs can accommodate a significant fraction of total slip and play a significant role in folding deformation. (v) Active FSFs may be used to assess seismic hazards associated with active folds and associated blind thrusts.

Piggyback basins on the margins of growing orogens commonly serve as sensitive recorders of the onset of thrust deformation and changes in source areas. The Bieertuokuoyi piggyback basin, located in the hanging wall of the Pamir Frontal Thrust, provides an unambiguous record of the outward growth of the northeast Pamir margin in northwest China from the Miocene through the Quaternary. To reconstruct the deformation along the margin, we synthesized structural mapping, stratigraphy, magnetostratigraphy, and cosmogenic burial dating of basin fill and growth strata. The Bieertuokuoyi basin records the initiation of the Pamir Frontal Thrust and the Takegai Thrust ~5-6 Ma, as well as clast provenance and paleocurrent changes resulting from the Pliocene-to-Recent uplift and exhumation of the Pamir to the south. Our results show that coeval deformation was accommodated on the major structures on the northeast Pamir margin throughout the Miocene to Recent. Furthermore, our data support a change in the regional kinematics around the Miocene-Pliocene boundary (~5-6 Ma). Rapid exhumation of NE Pamir extensional domes, coupled with cessation of the Kashgar-Yecheng Transfer System on the eastern margin of the Pamir, accelerated the outward propagation of the northeastern Pamir margin and the southward propagation of the Kashi-Atushi fold-and-thrust belt in the southern Tian Shan. This coeval deformation signifies the coupling of the Pamir and Tarim blocks and the transfer of shortening north to the Pamir frontal faults and across the quasi-rigid Tarim Basin to the southern Tian Shan Kashi-Atushi fold-and-thrust system.

In response to the Indo-Asian collision, deformation of the Tien Shan initiated at ∼25 Ma along the northwestern margin of the Tarim Basin. 300 km north, the Kyrgyz Range began deforming ∼15 Ma later. Although multiple intervening structures across the Tien Shan are currently active, the sequencing of initial deformation across the orogen's entire width remains poorly known. To determine whether deformation migrated sequentially northward or developed less predictably, we documented deformation patterns within the Naryn Basin in south-central Kyrgyzstan. Detailed mapping and a published balanced cross section across the Naryn Basin suggest that deep-seated, relatively steeply dipping thrust faults have disrupted the basin during late Cenozoic deformation. Dating of deformed fluvial terraces with ages between ∼10 and 250 ka constrains the rate of deformation across relatively young structures in the Tien Shan interior. Based on geodetic surveys of dated terraces, local rates of relative rock uplift span from 0.3 to 3.5 mm/yr. Folding rates and patterns are temporally persistent at a given site. Moreover, they mimic modern geodetic rates measured from interferometric synthetic aperture radar. Extrapolating these rates into the past suggests that structures within the interior of the Naryn Basin formed in the last 1 Myr, whereas the ranges surrounding the basin initiated at least 1-4 Myr earlier. Hence, within the Naryn Basin itself, deformation has migrated from margins to interior. Similarly, these new chronologies indicate that at least some deformation in the interior of the Tien Shan initiated millions of years later than along either orogenic margin. ©2014. American Geophysical Union. All Rights Reserved.

Recent studies of the northeastern part of the Tibetan Plateau have called attention to two emerging views of how the Tibetan Plateau has grown. First, deformation in northern Tibet began essentially at the time of collision with India, not 10-20 Myr later as might be expected if the locus of activity migrated northward as India penetrated the rest of Eurasia. Thus, the north-south dimensions of the Tibetan Plateau were set mainly by differences in lithospheric strength, with strong lithosphere beneath India and the Tarim and Qaidam basins steadily encroaching on one another as the region between them, the present-day Tibetan Plateau, deformed, and its north-south dimension became narrower. Second, abundant evidence calls for acceleration of deformation, including the formation of new faults, in northeastern Tibet since ~15 Ma and a less precisely dated change in orientation of crustal shortening since ~20 Ma. This reorientation of crustal shortening and roughly concurrent outward growth of high terrain, which swings from NNE-SSW in northern Tibet to more NE-SW and even ENE-WSW in the easternmost part of northeastern Tibet, are likely to be, in part, a consequence of crustal thickening within the high Tibetan Plateau reaching a limit, and the locus of continued shortening then migrating to the northeastern and eastern flanks. These changes in rates and orientation also could result from removal of some or all mantle lithosphere and increased gravitational potential energy per unit area and from a weakening of crustal material so that it could flow in response to pressure gradients set by evolving differences in elevation. Key Points The north-south limits of Tibet were set by lateral variations in strength Roughly 15 million years ago, deformation of NE Tibet accelerated Since 20-15 million years ago, the orientation of shortening rotated eastward ©2013. American Geophysical Union. All Rights Reserved.

Fold deformation in three dimensions involves shortening, uplift, and lateral growth. Fluvial terraces represent strain markers that have been widely applied to constrain a fold's shortening and uplift. For the lateral growth, however, the utility of fluvial terraces has been commonly ignored. Situated along northern margin of Chinese Pamir, the Mushi anticline preserves, along its northern flank, flights of passively deformed fluvial terraces that can be used to constrain three-dimensional folding history, especially lateral growth. The Mushi anticline is a geometrically simple fault-tip fold with a total shortening of 740 ± 110 m and rock uplift of ~1300 m. Geologic and geomorphic mapping and dGPS surveys reveal that terrace surfaces perpendicular to the fold's strike display increased rotation with age, implying the fold grows by progressive limb rotation. We use a pure-shear fault-tip fold model to estimate a uniform shortening rate of 1.5 + 1.3/-0.5 mm/a and a rock-uplift rate of 2.3 + 2.1/-0.8 mm/a. Parallel to the fold's strike, longitudinal profiles of terrace surfaces also display age-dependent increases in slopes. We present a new model to distinguish lateral growth mechanisms (lateral lengthening and/or rotation above a fixed tip). This model indicates that eastward lengthening of the Mushi anticline ceased by at least ~134 ka and its lateral growth has been dominated by rotation. Our study confirms that terrace deformation along a fold's strike not only can constrain the lateral lengthening rate but can serve to quantify the magnitude and rate of lateral rotation: attributes that are commonly difficult to define when relying on other geomorphic criteria. © 2013. American Geophysical Union. All Rights Reserved.

Between June and September each year, the Indian monsoon typically delivers about 80% of the Nepalese Himalaya's annual precipitation. Topography on the windward (southern) flank of the range modulates persistent spatial variations in precipitation along the length of the range. Where topography is stepped with an initial abrupt rise as the Himalaya abut the foreland and a second rise as topography ascends toward the high peaks, two bands of high precipitation prevail, each where relief passes a threshold value. In contrast, more uniform, northward rising topography localizes a single high-rainfall band near the front of the range. A dense meteorological network that was operated in the Marsyandi catchment from 1999 to 2004 in central Nepal gives more insight on spatial variability in precipitation. Annual precipitation decreases ten-fold between the rainfall peak (of ∼4. m/yr) on the southern flank of the Himalaya and the semi-arid rain shadow on its northern flank (40-50. km farther north). Modest contrasts in rainfall between ridges versus valleys during the monsoon are replaced by strong altitude-dependent precipitation contrasts in the winter. Strikingly, above ∼4. km altitude, ∼40% of the total precipitation arrives as winter snowfall. Four years of daily discharge and suspended sediment measurements on the main-stem and on several tributaries of the Marsyandi during the monsoon document a strong north-south gradient in average erosion rates. Based on a suspended-to-bedload ratio of 2:1 (as estimated from grain-sizes in a landslide-dammed paleo-lake), erosion rates range from ∼0.1. mm/yr in the northern rain shadow to ∼2. mm/yr in the monsoon-drenched south. This strong modern spatial gradient in erosion rates mimics the precipitation gradient across the same area and broadly scales with specific discharge. In the wetter regions, nearly a meter of rain is required before significant sediment fluxes occur. After this initial meter of rain, the daily rainfall required to trigger sediment pulses (attributable to landsliding) gradually decreases during the remaining monsoon season from ∼40. mm to 10. mm. In the higher altitude rain shadow to the north, water discharge is more closely linked to temperature than to precipitation: a linkage suggesting that melting of snow and ice, rather than rainfall, modulates the runoff. The sediment flux in the rain shadow during the monsoon season displays a marked temporal hysteresis: fluxes broadly scale with discharge during the first two months of the monsoon, but decouple from discharge later in the monsoon. This behavior suggests that the sediment flux is supply limited. We interpret that much of the sediment is subglacially derived and that its transport into the river network is restricted either by limited bedrock erosion or subglacial hydrology. © 2012 Académie des sciences.

Two of the most popular mechanisms for thickening the crust beneath the Tibetan Plateau are (1) pure shear with faulting and folding in the upper crust and horizontal shortening below and (2) flow of lower or middle crust without significant shortening of the upper crust. To help discriminate between the relative contributions of these two mechanisms, well-constrained estimates of upper crustal shortening are needed. Here we document the Cenozoic shortening budget across the northeastern Tibetan Plateau margin with several balanced cross sections that exploit thermochronological and magnetostratigraphic constraints. These sections indicate 11 +2/-1% east-west shortening since middle Miocene time and ∼9 +2/-3% NNE-SSW shortening between middle Eocene and middle Miocene times with little subsequent shortening of this orientation. Shortening rates accelerate fivefold after middle Miocene time. Given the present-day crustal thickness of 56 4 km in northeastern Tibet, crustal restorations that remove Cenozoic shortening suggest that the northeastern Tibetan crust was 45±5 km thick prior to the India-Asia continental collision. This precollision thickness estimate is equivalent to average continental crustal thicknesses both adjacent to the Tibetan Plateau (44±4 km) and globally (41±6 km) and suggests that pure shear alone may account for Cenozoic crustal thickening in northeastern Tibet. In contrast to eastern Tibet where, in the absence of significant shortening structures, crustal flow has been invoked to explain the addition of crustal material since middle Miocene time, our results may obviate lower crustal flow as a necessary crustal thickening agent in northeastern Tibet. Copyright © 2012 by the American Geophysical Union.

Sedimentary rocks in Tibetan Plateau basins archive the spatiotemporal patterns of deformation, erosion, and associated climate change that resulted from Cenozoic continental collision. Despite growing understanding of basin development in northeastern Tibet during initial India-Asia collision, as well as in the late Miocene-Holocene, surprisingly little is known about the intervening period: a time when the plateau may have undergone fundamental tectonic changes. To fill this gap, we present new magnetostratigraphy from a >2300-m-thick fluviolacustrine succession that spans ca. 30-9.3 Ma. An integrated analysis of sedimentology, subsidence, and provenance from this section reveals the sequential, pulsed erosion of multiple ranges bordering the Xunhua Basin. Emergence of the WNW-trending Laji Shan is highlighted by a doubling of sediment accumulation rates between 24 and 21 Ma and a transition to coarse allu vial facies at 20.3 Ma. Detrital zircon U/Pb age spectra show that these coarse sediments came from basement terranes within the Laji Shan. Together these observations suggest accelerated growth of the Laji Shan and its coupled foreland basin at ca. 22 Ma. The most rapid accumulation rates in Xunhua Basin occur within the finest-grained strata and suggest an underfilled basin during the fastest interval of Laji Shan deformation. Growth of the Laji Shan occurred northward of the contemporaneous plateau margin, which had been defined since ca. 45-50 Ma by the West Qinling, lying ~60 km farther south. Hence, following ~20-25 m.y. of apparent stability, the deformation front in this region jumped ~60 km to the north at ca. 22 Ma. Subsequently, growth of the north-trending Jishi Shan occurred at ca. 13 Ma and is highlighted by an acceleration in Xunhua Basin accumulation rates between 12 and 9 Ma, as well as by a significant change in detrital zircon provenance of nearby Linxia Basin deposits by 11.5 Ma. Initial growth of the WNW-trending Laji Shan in the early Miocene and subsequent growth of the north-trending Jishi Shan ~10 m.y. later support interpretations of a middle Mio cene kinematic reorganization in northeastern Tibet. © 2012 Geological Society of America.

In Central Asia's Tien Shan, deformation is distributed across the wide orogen, a characteristic of intracontinental mountain building. Active faults are commonly found within intramontane basins that separate its constituent ranges. In order to explore the controls on this intramontane basin deformation, we study the Naryn Basin of south-central Kyrgyzstan. A series of five balanced cross-sections reveals a transition in patterns of faulting from faults confined to basin margins to faults focused within the basin center. The 20-km-wide eastern Naryn Basin displays deformation attributed to low-angle splays of the northern, basin-bounding fault. In the 40-km-wide western Naryn Basin, the pattern of deformation linked to the northern range remains, but is accompanied by steeper faults that dip both south and north without being directly linked to the basin-bounding fault. We compare these cross-sections to synthetic aperture radar interferometry (InSAR) measurements of surface deformation. Profiles of InSAR-derived surface deformation rates across the Naryn Basin reveal that in the west, deformation is distributed across the broad basin interior, whereas in the east, rapid uplift is concentrated at the margin of the narrower basin. From the geodetic and structural data, we infer that in the western Naryn Basin, deformation has migrated away from the northern basin margin and into the interior. Deformation of the eastern basin interior, however, remains linked to the basin-bounding fault. A simple mechanical model demonstrates that basin width may control basin deformation whereby basin-interior faulting in the narrow, eastern Naryn Basin is inhibited by the overburden of adjacent ranges. Copyright 2011 by the American Geophysical Union.

As soon as a fold begins to grow above base level, it becomes subject to erosion. A numerical model of simultaneous fold growth and river erosion captures the early stages of channel formation and delineates the evolution of longitudinal channel profiles. This numerical exploration suggests that the patterns of channel incision into growing folds can be used to guide kinematic interpretations of fold growth. Four types of fold limb growth are modeled: limb lengthening through (1) the fold crest or (2) the fold toe, (3) limb rotation, and (4) curved fold limbs due to trishear folding. Initially, the pattern of channel incision is sensitive to the kinematics of surface deformation. Subsequently, more mature streams evolve toward similar incision patterns with deepest incision near the midpoint of the longitudinal channel profile. We compare these model predictions to Rough Ridge on New Zealand's South Island, where high-resolution topographic data reveal the multitude of channels incised into the flanks of these folds. Because the opposing limbs of these folds have followed distinct deformation pathways, the early sensitivity of channel incision to deformation pathway can be examined. Furthermore, the lateral propagation of the fold through time allows for an approximate space-for-time substitution, such that the evolution of these incision patterns can be examined from early through more mature stages. This analysis indicates that the west limb of Rough Ridge has grown by limb lengthening through the toe and the east limb has grown primarily by lengthening through the crest. Copyright 2011 by the American Geophysical Union.

Three successive zones of fault-related folds disrupt the proximal part of the northern Tian Shan foreland in NW China. A new magnetostratigraphy of the Taxi He section on the north limb of the Tugulu anticline in the middle deformed zone clarifies the chronology of both tectonic deformation and depositional evolution of this collisional mountain belt. Our ∼1200-m-thick section encompasses the upper Cenozoic terrigenous sequence within which ∼300 sampling horizons yield an age span of ∼8–2 Ma. Although the basal age in the Taxi He section of the Xiyu conglomerate (often cited as an indicator of initial deformation) is ∼2.1 Ma, much earlier growth of the Tugulu anticline is inferred from growth strata dated at ∼6.0 Ma. Folding of Neogene strata and angular unconformities in anticlines in the more proximal and distal deformed zones indicate deformation during Miocene and Early Pleistocene times, respectively. In the Taxi He area, sediment-accumulation rates significantly accelerate at ∼4 Ma, apparently in response to encroaching thrust loads. Together, growth strata, angular unconformities, and sediment-accumulation rates document the northward migration of tectonic deformation into the northern Tian Shan foreland basin during the late Cenozoic. A progradational alluvial–lacustrine system associated with this northward progression is subdivided into two facies associations at Tugulu: a shallow lacustrine environment before ∼5.9 Ma and an alluvial fan environment subsequently. The lithofacies progradation encompasses the time-transgressive Xiyu conglomerate deposits, which should only be recognized as a lithostratigraphic unit. Along the length of the foreland, the locus of maximum shortening shifts between the medial and proximal zones of folding, whereas the total shortening across the foreland remains quite homogeneous along strike, suggesting spatially steady tectonic forcing since late Miocene times. [ABSTRACT FROM AUTHOR]

Abstract: Current theories regarding the connections and feedbacks between surface and tectonic processes are predicated on the assumption that higher rainfall causes more rapid erosion. To test this assumption in a tectonically active landscape, a network of 10 river monitoring stations was established in the High Himalayas of central Nepal across a steep rainfall gradient. Suspended sediment flux was calculated from sampled suspended sediment concentrations and discharge rating curves. Accounting for solute and bedload contributions, the suspended sediment fluxes were used to calculate watershed-scale erosion rates that were then compared to monsoon precipitation and specific discharge. We find that, in individual watersheds, annual erosion rates increase with runoff. In addition, our data suggest average erosion rate increases with discharge and precipitation across the entire field site such that the wetter southern watersheds are eroding faster than the drier northern watersheds. The spatially non-uniform contemporary erosion rates documented here are at odds with other studies that have found spatially uniform long-term rates (105–106 yr) across the pronounced rainfall gradient observed in the region. The discrepancy between the modern rates measured here and the long-term rates may be reconciled by considering the high erosional efficiency of glaciers. The northern catchments were much more extensively glacierized during the Pleistocene, and therefore, they likely experienced erosion rates that were significantly higher than the modern rates. We propose that, in the northern watersheds, the high rates of erosion during periods of glaciation compensate for the low rates during interglacials to produce a time-averaged rate comparable to the landslide-dominated southern catchments. [Copyright &y& Elsevier]

Although detrital zircon has proven to be a powerful tool for determining provenance, past work has focused primarily on delimiting regional source terranes. Here we explore the limits of spatial resolution and stratigraphic sensitivity of detrital zircon in ascertaining provenance, and we demonstrate its ability to detect source changes for terranes separated by only a few tens of kilometers. For such an analysis to succeed for a given mountain, discrete intrarange source terranes must have unique U/Pb zircon age signatures and sediments eroded from the range must have well-defined depositional ages. Here we use ~1400 single-grain U/Pb zircon ages from northeastern Tibet to identify and analyze an area that satisfies these conditions. This analysis shows that the edges of intermontane basins are stratigraphically sensitive to discrete, punctuated changes in local source terranes. By tracking eroding rock units chronologically through the stratigraphic record, this sensitivity permits the detection of the differential rock uplift and progressive erosion that began ca. 8 Ma in the Laji Shan, a 10-25-km-wide range in northeastern Tibet with a unique U/Pb age signature. [ABSTRACT FROM AUTHOR]

Abstract: Thrust faulting is a fundamental mode of crustal deformation, yet many of the key geometrical attributes of thrust faults and the controls on fault rupture, growth, and linkage remain poorly resolved. Numerous surface-rupturing thrust faults cut through upper Quaternary glacial outwash terraces within the Ostler Fault zone, an active thrust system in the Southern Alps, New Zealand. We use these deformed marker surfaces to define the three-dimensional deformation field associated with their surface expression and to map displacement and length on ∼40 fault segments. Displacement transfer across two fault segment arrays occurs in distinctly different styles. In one, displacement is transferred between en échelon fault segments to produce a smooth, linear displacement gradient. In the other, large-scale folding and a population of small faults transfer displacement between two non-overlapping fault segments, with a residual displacement minimum within the transfer zone. Size distribution of fault-segment length and maximum displacement follow a power-law scaling relationship. Maximum displacement (D max) scales linearly with and represents ∼1% of segment trace length (L). D max/L data from the segments of the Ostler Fault zone display similar scaling to a global fault dataset. This similarity is surprising, given that the observed displacements along the Ostler Fault represent only 20ky of slip on fault segments that are likely to be many times older. [Copyright &y& Elsevier]

Demonstrates that patterns of sediment accumulation and the position of major rivers in the Neogene Gangetic foreland basin appear to have changed markedly in Plio-Pleistocene times. Support for the hypothesis that the importance of erosional unloading has increased in the Himalayas during the past 4 Myr.

Comparison of rainfall data and mean hillslope angles in the Himalayas of central Nepal shows that mean hillslope angles decrease with increasing mean annual rainfall. Higher pore pressures and higher rates of chemical weathering in the wetter regions may decrease the threshold angle of hillslopes prone to landsliding. When valley spacing is held constant, the sensitivity of mean hillslope angle to climate implies that relief, in the absence of limits due to rock strength, is also dependent on climate. These results suggest that wet-to-dry climatic changes increase relief in regions with incising bedrock channels and that dry-to-wet climatic changes reduce relief. [ABSTRACT FROM AUTHOR]