Younger Terraces Research Articles

Quaternary landscape evolution of the Helmand Basin, Afghanistan: Insights from staircase terraces, deltas, and paleoshorelines using high-resolution remote sensing analysis

The Helmand Basin in southern Afghanistan is a large (310,000 km2), structurally controlled, endorheically drained basin with a hyperarid climate. The basin hosts a high elevation (~200 m) plateau (the Dasht-i Margo), 11 fluvial staircase terraces (T11 to T1), 7 delta systems (D1 to D7), and 6 paleolake shorelines (SL1 to SL6) within the Sistan Depression on the western side of the basin. Mapping and surveying of these features by remote sensing is integrated with geological observations to reconstruct Quaternary landscape evolution of the basin. The fluvial systems, deltas, and paleolake shorelines are correlated with one another and with the younger terraces (T7 to T1). The shape of fluvial longitudinal profiles changes depending on whether they formed pre-, syn-, or post-growth of the Koh-i Khannesin volcano on the southern margin of the Helmand River. The age of the volcano (~0.6 Ma) and correlation of the terraces with the global history of glacial-interglacial cycles constrain the age of the younger terraces to the late Pleistocene and indicates that the older terraces are middle Pleistocene (dating back to 800 ka). The Helmand Basin once hosted a large lake, called here the Sistan paleolake, which at SL6 times and before had a surface area >50,000 km2. Since that time the lake elevation and area have decreased, evolving to the present-day dried out Sistan Depression with small ephemeral playa lakes. Episodic formation of terraces, deltas, and paleolake shorelines is attributed to changes in base level modulated by climate change related to Milankovitch cycles.

Modelling and simulation of Holocene marine terrace development in Boso Peninsula, central Japan

In the southern part of Boso Peninsula, central Japan, we can observe a series of well-developed Holocene marine terraces. We modeled the development of these marine terraces by considering sea-level fluctuation and steady land uplift. The evolution of coastal landform is generally described as follows: altitude change = − erosion + deposition − sea-level rise + land uplift. In this study, the erosion rate is supposed to be proportional to the dissipation rate of wave energy, and the deposition rate of eroded materials to decay exponentially as they are transported seaward. The rate of sea-level rise is given by the time derivative of a sea-level curve obtained from the sediment core records of oxygen isotope ratios. Steady plate subduction generally brings about steady crustal uplift/subsidence independently of earthquake occurrence, and so the land-uplift rate is regarded as time independent on a long-term average. Our simulation results show that a pair of sea cliff and abrasion platform is efficiently formed about a stationary point of the sea-level curve. The Holocene sea-level curve has four peaks and three troughs, and so basically seven terraces are formed one by one during the past 10,000 yr. However, when the land-uplift rate is low, most of the terraces formed at older times sink in the sea. When the land-uplift rate is high, the overlap and/or reverse of older and younger terraces occur frequently, and so the correspondence between the age and present altitude of terraces is not necessarily one-to-one. Taking the land-uplift rate to be 3–4 mm/yr, we can reproduce a series of well-developed Holocene marine terraces in Boso Peninsula independently of coseismic uplifts. From these simulation results, we may conclude that the Holocene marine terraces in Boso Peninsula were developed as a result of the composite process of sea-level fluctuation and steady coastal uplift.

Monitoring a commercial vineyard in New Zealand to maintain soil health and achieve long-term sustainability

This paper illustrates the benefits of long-term monitoring of soil and vine health in Craggy Range’s Te Muna vineyard in the Martinborough region of New Zealand. The soils at Te Muna are formed on two river terraces. The higher and older terrace, planted to Pinot Noir, is very gravelly; the lower and younger terrace, planted to Sauvignon Blanc, contains more silt and very fine sand. Both terraces are freely drained. Soil pH, organic C and available P were monitored in selected blocks on both terraces. Under current management that includes cover crops and sheep grazing in winter, soil organic C has been stable for 10 years. Because of the regular application of RPR and intermittent liming, soil pH (water) has risen from c.5.5 to 6.5–7. Values for soil available P, measured by Olsen bicarbonate and Mehlich-3 extractions, diverged over time. The Olsen test indicated satisfactory P levels: conversely, the Mehlich test showed P values rising to very high levels, confirming Western Australian experience that this acid extraction is unsuitable for soils treated with RPR. Petiole and leaf blade P concentrations confirmed these results, but they showed greater interannual variation than the soil P measurements. Overall, the long-term sustainability of the vineyard should be assured.

Active Flexural‐Slip Faulting: Controls Exerted by Stratigraphy, Geometry, and Fold Kinematics

AbstractFlexural slip plays an important role in accommodating fold growth, and its topographic expression, flexural‐slip fault (FSF) scarps, may be one of the most commonly occurring secondary structures in areas dominated by active thrusts and folds. Where FSF scarps are present and what factors control their occurrence, however, are typically poorly known. Through an investigation of clearly expressed FSF scarps, well‐preserved fluvial terraces, and well‐exposed bedrock at eight sites in the Pamir‐Tian Shan convergent zone and Kuche fold belt, NW China, we summarize the most favorable conditions for active flexural‐slip faulting. Our study yields six key results. First, flexural slip operates commonly in well‐layered beds, although uncommonly can occur in massive, poorly layered beds as well. Second, in well‐layered beds, the slip surface is commonly located either (a) close to the contact of competent and incompetent beds or (b) within thin incompetent beds. Third, FSF scarps are always found overlying steep beds with dips of ~30–100°. Fourth, slip surfaces are typically spaced between ~10 and 440 m but can reach up to ~600 m. Fifth, FSF scarps at most sites can be observed far away from the hinge‐migrated fold scarps, suggesting that compared to hinge migration, limb rotation is generally required to accumulate flexural slip and produce associated topographic scarps. Finally, a higher regional convergent rate seems to facilitate the creation of FSF scarps more often than lower rates, whereas well‐preserved, old terraces capped by thin deposits are more likely to record FSF scarps than unevenly preserved, young terraces with thick sedimentary caps.

Determining contribution of sand dune potential sources using radionuclides, trace and major elements in central Iran

The present research describes a first attempt to use quantitative fingerprinting to quantify source contributions of sand dunes. Forty-nine surface samples from the main potential sources within Yazd-Ardekan Plain in the central Iran were collected and compared with eight samples of sand dunes, collected on various sites of Ashkzar erg. Three major categories of sand dune source were identified: young terraces and gravel fans (Qt2), clay flat (Qc), and gypsiferous marl (Egm). After sample preparation, concentrations of geochemical elements such as rare earth element (REE), major and trace elements, and isotopes of strontium (87Sr and 86Sr) and neodymium (143Nd and 144Nd) were measured. The results indicated, based on discriminant function analysis, 81.6% of the samples to be correctly assigned to their source areas. The mean contributions from Qt2, Qc, and Egm sources in the study area were estimated as 59, 30, and 11%, respectively. The efficiency coefficient for mixing model was calculated to be 0.99, which represents that the fingerprinting technique has a great potential for apportionment of sand dune sources.

PEDOLOGICAL STUDIES ON SOME SOILS WEST IDFU ASWAN EGYPT BY USING REMOTE SENSING DATA

The study aims at using satellite images and GeographicalInformation System (GIS) for physiographic digital soil mapping andcapability assessment of the area western side of Idfu district, AswanGovernorate, Western Desert .The area lies between longitude 32°29¯45= and 32°47¯1332= E and latitudes 24° 22- 38= and 25°8¯36=N andoccupies total area about 139000 feddans. To fulfill this objectiveLandsat ETM+ image and digital elevation model (DEM) of the studiedarea were used to define the physiographic units of the studied area. Thephysiographic units of the area under consideration could be grouped anddescribed as young terraces, old terraces, Wadi, Outwash plain .Thedifferent landforms were represented by 9 soil profiles, the morphologicaldescription was carried out and 26 disturbed soil samples were collectedfor physical and chemical analysis . The obtained results revealed that thesoils of the studied area are classified as follow:A)-Soils of Old Terraces: Typic Torriorthents, sandy, mixed,hyperthermic.(Profile8).Gypsic Haplosalids coarse loamy, mixed hyperthermic.(profile9) B)-Soils of the Young terraces: a) Typic Torripsamments siliceaus,hyperthermic (profil,1)-b) Gypsic Haplosalides coarse loamy, mixed,hyperthermic(profile,2)–c). Typic Haplosalides, coarse loamy ,mixed,hyperthermic. profiles 2 and3. C)-Soils of Wadis: Typic Torriorthents, sandy,mixed, hyperthermic (profiles 4 and 5 ) D)-Soils of Outwash Plains:.TypicTorriorthents, sandy ,mixed ,hyperthermic (profile,6) Typic Calcigypsids,coarse loamy,mixed,hyperthermic (profile,7).Land capability classes was performed using Sys & Verheye (1978)System, The studied soils could be categorized into two suitability classes(S3) marginally suitable and (N) not suitable which are suffering from soiltexture, soil profile depth, salinity and alkalinity and CaCOз content assoil limitations. To correct the severity of these limitations further landimprovement should be executed and in turn potential suitability surveyedas moderately suitable (S2), marginally suitable (S3) and not suitable (N)were recognized in the studied area. The severity can be corrected byapplication of organic and inorganic soil amendments and salt leaching

The Gediz River fluvial archive: A benchmark for Quaternary research in Western Anatolia

The Gediz River, one of the principal rivers of Western Anatolia, has an extensive Pleistocene fluvial archive that potentially offers a unique window into fluvial system behaviour on the western margins of Asia during the Quaternary. In this paper we review our work on the Quaternary Gediz River Project (2001–2010) and present new data which leads to a revised stratigraphical model for the Early Pleistocene development of this fluvial system.In previous work we confirmed the preservation of eleven buried Early Pleistocene fluvial terraces of the Gediz River (designated GT11, the oldest and highest, to GT1, the youngest and lowest) which lie beneath the basalt-covered plateaux of the Kula Volcanic Province. Deciphering the information locked in this fluvial archive requires the construction of a robust geochronology. Fortunately, the Gediz archive provides ample opportunity for age-constraint based upon age estimates derived from basaltic lava flows that repeatedly entered the palaeo-Gediz valley floors. In this paper we present, for the first time, our complete dataset of 40Ar/39Ar age estimates and associated palaeomagnetic measurements. These data, which can be directly related to the underlying fluvial deposits, provide age constraints critical to our understanding of this sequence.The new chronology establishes the onset of Quaternary volcanism at ∼1320ka (MIS42). This volcanism, which is associated with GT6, confirms a pre-MIS42 age for terraces GT11-GT7. Evidence from the colluvial sequences directly overlying these early terraces suggests that they formed in response to hydrological and sediment budget changes forced by climate-driven vegetation change. The cyclic formation of terraces and their timing suggests they represent the obliquity-driven climate changes of the Early Pleistocene. By way of contrast the GT5-GT1 terrace sequence, constrained by a lava flow with an age estimate of ∼1247ka, span the time-interval MIS42 – MIS38 and therefore do not match the frequency of climate change as previously suggested. The onset of volcanism breaks the simple linkage of terracing to climate-driven change. These younger terraces more likely reflect a localized terracing process triggered by base level changes forced by volcanic eruptions and associated reactivation of pre-existing faults, lava dam construction, landsliding and subsequent lava-dammed lake drainage.Establishing a firm stratigraphy and geochronology for the Early Pleistocene archive provides a secure framework for future exploitation of this part of the archive and sets the standard as we begin our work on the Middle-Late Pleistocene sequence. We believe this work forms a benchmark study for detailed Quaternary research in Turkey.

Evolution and progressive geomorphic manifestation of surface faulting: A comparison of the Wairau and Awatere faults, South Island, New Zealand: COMMENT

Zinke et al. (2015) documented a flight of Saxton River terraces deformed by the Awatere fault, South Island, New Zealand. They concluded that the manifestation of off-fault deformation (OFD) is a cumulative effect, and therefore may not be immediately apparent on younger terraces, with implications for slip rate determinations. I argue that they did not adequately consider the detailed structural setting of elements of OFD within the Saxton River releasing bend on the Awatere fault. The surface deformation at Saxton River is probably controlled by the coincidence of terraces with structural zones within the bend, and I contest the authors’ conclusion that off-plane deformation is simply hidden in younger terraces. The influence of structural complexity on the width and geometry of OFD is well established (e.g., Milliner et al., 2015). Zinke et al.’s figure DR2 (in GSA Data Repository 2015341) shows that OFD along the Awetere fault occurs at bends or steps in the fault plane, including at Saxton River where the fault bends right relative to the main trace by 5–10°, ~50 m east of the T2-T3 riser. This gives rise to a graben (T1 tread) and two pressure ridges (T2 tread and bedrock spur) that define and bound an overall 150-m-wide releasing bend (Mason et al., 2006) (Figs. 1A and 1B). The paired pressure-ridge and graben geometry is predicted when the wall rocks on either side of a strike-slip fault approach and interact with a fault bend during an earthquake (Sibson, 1989), and has been reported on the Hope (Cowan, 1990) and Greendale (Duffy et al., 2013) faults in New Zealand, and the San Andreas fault in California (Ben-Zion et al., 2012), among others.

Quantitative comparative geomorpholgical analysis of fluvial and karst relief of Florida

Karst relief of Central Florida and fluvial relief of the Florida Panhandle were analyzed and compared on the basis of standardized samples of karst and fluvial topography derived from digital databases in a GIS environment. Comparative geomorphological analyses of the two distinct genetic relief types were performed on the basis of morphometric parameters derived for each type of relief in general as well as differentially for hypsometric intervals of paleo-marine terraces with the assumption of relative stability of tectonic conditions of the underlying carbonate platform. The comparative analyses conducted indicate overall higher values of the morphometric parameters in the fluvial relief compared to those in the karst relief. This is a consequence of more than two times higher rates of fluvial denudation compared to the karst denudation rates (0.23 vs. 0.11 mm/year, respectively). Differential analyses with respect to the paleo-marine terrace intervals reveal significant quantitative morphological differences between the upper, older and lower, younger terrace intervals in the karst and fluvial relief. In the two older terrace intervals, fluvial and karst denudation rates range from 0.07 to 0.09 mm/year, while in the younger terrace intervals fluvial denudation shows more than two times higher rates than the karst denudation (0.22 and 0.55 vs. 0.11 and 0.19 mm/year), indicating that fluvial processes in the study area are more effective than the respective karst processes. This is clearly reflected in the higher values of vertical dissection and denudated sediment volume in the fluvial relief in the younger terrace intervals, while the increased karst denudation rates are not yet reflected in the respective morphometric parameters due to the slower morphologic response. Overall, long-term karst denudation ranging from 0.07 to 0.19 mm/year is derived by volumetric analysis of the denudated sediment and as such accounts for the effects of both chemical and mechanical denudation. Consequently, they are significantly higher than the previously calculated short-term solutional denudation rates, although their values fall in the mid range of theoretical estimations with respect to climatic conditions of the study area. The obtained fluvial denudation rates ranging from 0.07 to 0.55 mm/year are similar to previous estimates of long-term fluvial denudation.

Lithologic controls on valley width and strath terrace formation

Valley width and the degree of bedrock river terrace development vary with lithology in the Willapa and Nehalem river basins, Pacific Northwest, USA. Here, we present field-based evidence for the mechanisms by which lithology controls floodplain width and bedrock terrace formation in erosion-resistant and easily friable lithologies. We mapped valley surfaces in both basins, dated straths using radiocarbon, compared valley width versus drainage area for basalt and sedimentary bedrock valleys, and constructed slope-area plots. In the friable sedimentary bedrock, valleys are 2 to 3 times wider, host flights of strath terraces, and have concavity values near 1; whereas the erosion-resistant basalt bedrock forms narrow valleys with poorly developed, localized, or no bedrock terraces and a channel steepness index half that of the friable bedrock and an average channel concavity of about 0.5. The oldest dated strath terrace on the Willapa River, T2, was active for nearly 10,000years, from 11,265 to 2862 calibrated years before present (cal YBP), whereas the youngest terrace, T1, is Anthropocene in age and recently abandoned. Incision rates derived from terrace ages average 0.32mmy−1 for T2 and 11.47mmy−1 for T1. Our results indicate bedrock weathering properties influence valley width through the creation of a dense fracture network in the friable bedrock that results in high rates of lateral erosion of exposed bedrock banks. Conversely, the erosion-resistant bedrock has concavity values more typical of detachment-limited streams, exhibits a sparse fracture network, and displays evidence for infrequent episodic block erosion and plucking. Lithology thereby plays a direct role on the rates of lateral erosion, influencing valley width and the potential for strath terrace planation and preservation.

Soil evolution in a tropical climate: An example from a chronosequence on marine terraces in Taiwan

Because of frequent tectonic activities due to arc–continent collision, multi-level marine terraces are present along the coast of the Taiwan Island. They are suitable sites for constructing tropical soil chronosequences. This study investigated soils along a transect on reef terraces on the Kenting Peninsula, the southmost tip of Taiwan, in order to construct a soil chronosequence and then reveal the relation between the soils and geomorphic processes. Parent materials of the soils appear to be mainly alluvial deposits or eolian beach sands covering the reef. Selected pedogenic properties of the soils, clay, free iron oxides and crystallinity ratio of free iron oxides, silicon–aluminum and silicon–aluminum–iron ratio, silicon–aluminum and silicon–aluminum–iron ratio, increased or decreased or decreased rapidly at first and slowly with time, following a single logarithmic relationship with soil age. Moreover, the structureless soils on the youngest terrace were classified as Entisols, whereas the soils with subangular blocky and clay coatings on the high (old) terraces were classified as Alfisols or Ultisols. A post-incisive chronosequence was identified for these soils. Finally, a schematic model is proposed to explain the relationships between pedological morphologies of the soils and terrace-surface processes.

A field guide to Charles Dawson's discredited sites implicated in the Piltdown hoax

Charles Dawson, FSA, FGS (1864–1916), was discoverer and presumed forger of Piltdown Man and the less well-known Barcombe Mills Man in East Sussex. Although the fossils were either fakes or salted from elsewhere, Dawson's geology was accurate apart from his over-estimate of the height of the Piltdown terrace above the River Ouse, leading to it being correlated with the 100ft (30m) terrace of the River Thames. This was corrected by Francis Hereward Edmunds, MA, FGS (1893–1960), who recognised it as a 50ft terrace, but this determination was largely ignored until the detection of the forgery in 1953. Subsequently, Piltdown has been the subject of palaeoanthropological speculation ad nauseum – essentially, who dunnit? – but the historical interest taken in the geology has been minimal. A field guide to Dawson's false hominin sites follows the valley of the River Ouse and its terraces. The so-called Piltdown Man II site near Sheffield Park was probably at Netherhall Farm. The type locality of Piltdown Man, Eoanthropus dawsoni, is marked by a memorial stone, but is on private property. The third site, on a hill above Barcombe Mills railway station (closed) and erroneously called Piltdown Man III in the literature, is a younger terrace and produced remains not considered to be E. dawsoni. The total length of the walk is about 16.4km on flat to gently undulating topography in a Quaternary landscape carved by the River Ouse.

Assessing changes in soil properties in the eastern part of the Nile delta over a long-term period

The properties of alluvial soils eastern part of Nile delta based on geomorphological zones are studied. Water characteristics, soil physical and chemical properties were studied during 24–40 years. The results showed that the highest soils quality of alluvial zone are located in young terraces. In a zone of coastal plain the salinization processes are active. On the other hand old terraces are dominated by aeolian processes.

Fluvial terrace formation in the lower Awhea and Pahaoa River valleys, New Zealand: implications for tectonic and sea-level controls

Altitudes and ages of fluvial terraces along the lower Awhea and Pahaoa River valleys are compared with the altitudes and ages of Holocene marine deposits and terraces in the actively uplifting southern Hikurangi Margin, New Zealand. From these, we infer fluvial terrace formation processes and examine implications for controls on river behaviour and the likely mechanism of uplift. Both river valleys contain a prominent fill terrace (PgT) radiocarbon dated at 10,000–8000cal. y BP, which formed in response to the rapid estuary infilling during the late stage of post-glacial sea-level rise. Older and younger terraces are primarily degradation terraces, with the exception of the oldest terraces mapped, which are fill terraces inferred to date from the Last Glacial Coldest Period. These results show the Awhea and Pahaoa Rivers respond to a number of competing controls including climate, tectonics, sea-level and anthropogenic (land use) changes, gradient and valley width. The influence of tectonic uplift can be isolated and Holocene marine terraces, estuarine deposits and the PgT tread altitudes are used to constrain the single-event displacement and slip rate of the submarine Palliser-Kaiwhata Fault, of 2–5m and 2.5±1mm/y, respectively. The results also provide insight into likely future response of rivers such as the Awhea and Pahaoa to sea-level rise and tectonic uplift.

Habitat and C-14 ages of lignitic terrace deposits along the northern Sarawak Coastline

The young terraces fringing the Miri coastline from Miri to Bekenu are formed by lignitic sands, fossil wood, and conglomeratic beds that contain reworked quartz pebbles derived from the older Tukau Formation. The sequence can be subdivided into four sub-units: I. Basal Conglomerate, II. Sandstone with fossil wood and Ophiomorpha, III. Cross- bedded lignitic sandstone, and IV. Bleached and weathered palaeosol. These sediments are indicative of a transgressive near-shore, fluvial to marginal marine depositional environment, as water energy peaked in cross-bedded sandstone of Sub- unit III. Radiometric C-14 based age determination in ten coastal locations indicates an age range from Late Pleistocene to Early Holocene (28,570 + 230 to 8,170 + 50 years BP). Given the terraces were formed in the same environment, but are now located at different elevations and appear to be block-faulted, it might imply significant tectonic movements in the Holocene.

Analysis of spatial\u2013temporal patterns of water table change as a tool for conjunctive water management in the Upper Central Plain of the Chao Phraya River Basin, Thailand

A sustainable strategy for conjunctive water management must include information on the temporal and spatial availability of this natural resource. Because of water shortages in the dry seasons, farmers on the Upper Plain of the Chao Phraya River basin, Thailand, are increasingly using groundwater to meet their irrigation needs. To evaluate the possibilities of conjunctive water management in the area, the spatial–temporal changes in the water table of the Younger Terrace Aquifer were investigated. First, a regional geomorphological map based on field surveys, remote sensing and previous environmental studies was developed. Then, the well data were analyzed in relation to rainfall, streamflow, yield and pumpage, and the data were interpolated using geostatistical techniques. The results were analyzed via integrated zoning based on color theory as applied to multivariate visualization. The analysis results indicate areas that would be more suitable for groundwater extraction in a conjunctive management framework with regard to the natural hydrogeological processes and the effects of human interaction. The kriging results were compared with the geomorphological map, and the geomorphological areas exhibit distinct hydrogeological patterns. The western fans exhibit the best potential for the expansion of conjunctive use, whereas the borders of the northern fans exhibit the lowest potential.

Comment on “Geomorphology in relation to tectonics: A case study from the eastern Himalayan foothills of West Bengal, India” by Chandreyee Chakrabarti Goswami, Dhruba Mukhopadhyay, B. C. Poddar [Quaternary International, 298, 80–92

In a recent paper Chakrabarti Goswami et al., 2013 discussed the geomorphology of Matiali fan and the terraces formed along the rivers traversing this fan, in the Jalpaiguri District of West Bengal, eastern Himalaya. The area of their study is tectonically active with a couple of blind thrust traversing the Quaternary fan deposits. The authors have proposed that the tectonic movements along blind thrust faults of the area, were the main control of formation and present disposition of the terraces. In proposing this, the authors have completely ignored the question of aggradation of the terraces, sediment:water ratio in the alluvial system and role of well-known climatic fluctuations during the time span over which these geomorphic features formed in eastern Himalaya. They have reported fault propagation folds deforming the fan sediments, but did not document any deformation or any other features within the younger terraces that could substantiate their claim of tectonics as the main agent for the development of the terraces. In this comment we point out the inconsistencies in the tectonogeomorphic model proposed by them and suggest that the climate induced aggradation played a major role in the formation of the terraces in the river valleys in this area.

Late Quaternary alluvial sequence and uplift-driven incision of the Urumqi River in the north front of the Tian Shan, northwestern China

This work focuses on the driving force behind the late Quaternary river incision and terrace formation of the Urumqi River in the north piedmont of the Tian Shan, northwestern China. Field investigations on geomorphic surfaces, terrace deposits, and its underlying bedrock identify four most significant features, which creates a local applicable framework for subdivision of the late Quaternary terrace sequence in the study area. Nine stepped river terraces are defined and designated as T1 to T9 increasing systematically in elevation. Morphologically, the highest T9 correlates with the oldest alluvial fan F1 of the Urumqi River. River incision and the resultant abandonment of fan F1 are chronologically constrained at ca. 550ka. The stratigraphic geometry of the Saerqiaoke anticline, a structure developing at the fan end of F1, reveals the existence of growth strata, implying continuous growth of this fold when the F1 alluvial sediments were deposited. In the range front of the Urumqi River, growth of the Saerqiaoke anticline has derived tectonically from uplift and basinward thrusting of the Tian Shan range. Such thrusting and basinward extension of the range are expected to force rock uplift of the headwater of the Urumqi River with respect to the Chaiwopu basin to the north and thus river incision occurring at ca. 550ka. During the subsequent period, several younger terraces have been formed in response to the further uplift of the Saerqiaoke anticline as well as climate changes during glacial–interglacial transitions. In the present study area, the total incision during Quaternary comes close to 400m, with about 85% contribution likely attributed to rock uplift of the Saerqiaoke anticline.

Rates of river incision across the main tectonic units of the Pamir identified using optically stimulated luminescence dating of fluvial terraces

Calculated incision rates along the Panj, the main river of the Pamir, are used to investigate any influence by tectonics or climate on the architecture of the river. The depositional ages of Panj River terraces were calculated using optically stimulated luminescence (OSL) dating of terrace sand. Fluvial incision rates were generated by integrating the terrace depositional ages with accurate kinematic GPS measurements of terrace heights above the modern Panj. We investigated 16 terraces along the Panj at the western Pamir margin and one terrace from the Vakhsh River to the north of the Pamir. The results reveal brief periods of fluvial deposition over the past 26kyr. The oldest Panj terrace depositional ages coincide with early MIS 2 and MIS 2/1 glaciations on the Pamir Plateau. Younger terrace ages have no apparent link with glacial cycles. Terraces with varying heights above the modern Panj at different localities yielded similar depositional ages. This suggests that local conditions have determined fluvial incision rates. Combining all of the terrace measurements, the average incision rate of the Panj over the last 26kyr has been ~5.6mm/yr. A high mean incision rate of ~7.3mm/yr was calculated from terraces where the Panj has cut a steep-sided valley through the Shakhdara dome. Significantly lower incision rates (~2–3mm/yr) were calculated from terraces where the Panj flows along the southern boundaries of the Shakhdara and Yazgulom domes. At those localities, graded segments of the Panj River profile and increased valley widths are indicative of local base levels. Downstream of the Yazgulom dome, river incision rates are generally lower (~4–5mm/yr) than the Panj average. However, there is one exception where higher incision rates (~6mm/yr) were calculated upstream of the Darvaz Fault Zone, a major tectonic feature that forms the western boundary of the Pamir. The Vakhsh River terrace to the north of the Pamir yielded a lower incision rate (~3mm/yr) compared to the Panj average. Variation in incision rates along the Panj does not correspond to changes in rock type or river catchment area. Instead, incision rates appear to have been primarily influenced by river capture across the southern and central metamorphic domes of the Pamir. Wherever the Panj cuts these domes it displays a convex river profile. The combination of localized river profile convexity and changes in incision rates across the Pamir domes indicates that the dome boundaries have been active recently.

Geochronology and geoarchaeology of Pleistocene fluvial deposits in the Prados-Guatén Depression (Madrid Basin, Central Spain)

This study deals with the geochronological, geoarchaeological, sedimentological and geomorphological analyses of sandy Pleistocene fluvial deposits exposed throughout the Prados-Guatén Depression, occupying the wide drainage divide of the Guadarrama and Jarama rivers draining towards the Tagus River (SW Madrid, Central Spain). Pleistocene fluvial deposits within the depression record two different fluvial systems draining the zone during the Pleistocene. Older fluvial deposits (T1), thick stacked arkosic sand sequences (∼15–17 m) with fossil fauna attributable to the Lower Pleistocene (c. 1.0–0.9 Ma; Mammuthus meridionalis NESTI), exposed at elevations of +15–40 m above the present Guatén stream thalweg. This terrace was deposited by an ancient fluvial system draining the Depression north to south, flowing directly to the Tagus (Paleo-Manzanares). Overlapping the older ones, the younger deposits studied are inset fluvial terraces at +13–16 m (T2) and +8 m (T3). T2 Upper-Middle Pleistocene (500–200 ka) fauna, Equus ferus cf. Mosbachensis, is related with the abandonment of the valley, the onset of a stage of relevant intra-valley dissection, and subsequent refilling linked to the early organization of the present drainage leading to the development of T3. Paleomagnetic data from T2 and T3 terraces display an overall normal “Brunhes” polarity, although anomalous reverse polarities are recorded in the younger terrace (T3). TL and OSL dates range between c. >126–75 ka for T2 (MIS 5) and c. 20–17 ka for T3 (MIS 2), indicating a mainly Upper Pleistocene age for the development of these two more recent terraces. The dates obtained indicate that the establishment of the present divergent fluvial arrangement within the Prados-Guatén Depression started during the Middle-Upper Pleistocene transition, after it was abandoned by the Lower-Middle Pleistocene Paleo-Manzanares fluvial system (T1). T2 contains a variety of Lower to Middle Palaeolithic flint flaking products, indicating chronocultural transition during the Upper Pleistocene in the area, correlated with a drastic change in the fluvial landscape from the end of MIS 5 (<75 ka).