Terrace Formation Research Articles

Estudio de la evolución cuaternaria de un modelado fluvial escalonado intramontañoso mediante índices morfométricos: río Lozoya, Sistema Central Español

Los índices morfométricos son descritos como herramientas útiles para comprender la evolución geodinámica de diferentes regiones geológicas, aunque suelen aplicarse considerando sólo la geometría actual de las formas del relieve. En este trabajo, hemos combinado una cartografía geomorfológica detallada & algunos de los índices y variables morfométricas más relevantes (Vf, Índice-T, SL, concavidad, elevación y pendiente), para cuantificar la evolución del río Lozoya. Estos índices fueron calculados usando no sólo las formas actuales del relieve, sino también para diferentes periodos. Este es el caso del índice Vf, cuyos valores fueron calculados a lo largo del tiempo, utilizando la paleotopografía definida por las terrazas fluviales rocosas del río Lozoya. Estas técnicas fueron aplicadas a la sequencia de terrazas rocosas del río Lozoya por medio de SIG y herrameintas estadísticas. El área de trabajo se ubica en una depresión tectónica intramontañosa delimitada por alineaciones pop-up (Sistema Central Español). El análisis geomorfométrico ha revelado una evolución Cuaternaria compleja controlada y condicionada por factores como las principales, estructuras Alpinas, la litología de subsuelo, la geomorfología regional, el levantamiento regional y el clima. En la cuenca de drenaje del Río Lozoya, los valles más incididos y estrechos se localizan aguas abajo, asociados con cambios litoestructurales y capturas fluviales, mientras que los valles más amplios se localizan hacia la zona de cabecera, relacionados con depresiones tectónicas pop-down. Por otro lado, el análisis del perfil longitudinal del Río Lozoya ha mostrado que los knickpoints mayores han persistido durante el tiempo, por lo menos desde el Mioceno Superior y sin aparentes signos de reactivación durante el Cuaternario. Finalmente, nuestro análisis revela que la formación y preservación de las terrazas erosivas están controladas por factores litológicos y morfoestucturales.

Evolution of Holocene alluvial landscapes in the northeastern Songshan Region, Central China: Chronology, models and socio-economic impact

A recent suggestion of the existence of an enormous ancient waterbody in Central China had been associated with the intensifying water management that led to the rise of early states. However, the evolution of regional alluvial landscapes remains unclear. Through intensive geoarchaeological surveys and careful field examination of typical sedimentary sequences, we reconstructed Late Pleistocene-Holocene landscapes in the northeastern Songshan Region and identified three distinctive models of landscape evolution. In the loess hills and tablelands areas, rivers were characterized by the large-scale alluvial aggradation during the terminal Late Pleistocene. Following a slight river incision during the Early Holocene, a pronounced alluvial aggradation resumed throughout the Middle Holocene. This gave way to another episode of river downcutting during the Late Holocene. The platform-type plains area witnessed a similar process of landscape evolution. However, the amplitude of the Early Holocene river-incision was smaller, whilst the large-scale Middle Holocene aggradation filled up the valleys, which also led to the formation of buried terraces. The eastern plains area was marked by continuous alluvial-lacustrine aggradation from the Late Pleistocene onwards. Many lakes, marshes and wetlands were formed during the Middle Holocene river aggradation. These waterbodies were separated by the high-elevation landforms, creating a mosaic-like aquatic landscape. The Late Pleistocene-Holocene landscape supported mixed farming of rice and millets from the Neolithic to Bronze Age. After 4000 BP, with another event of river incision, the wetlands shrank, and the extensive area of drylands emerged in the east plains. This change coincided with the emergence of large-scale urban centers in the region.

Rapid flood intensification and environmental response of the Lower Meuse during the Allerød-Younger Dryas climate transition

Lateglacial climatic oscillations exerted profound impacts on the Meuse fluvial system. In the Lower Meuse (southern Netherlands), geomorphological studies in the last decades mainly centred on Lateglacial vegetation evolution, channel pattern changes and river terrace formation. Little information has been reported about the paleohydrology and its relation with the regional climate conditions. This study investigates a sediment core that contains flood sediments deposited from the early Allerød up to the middle Holocene. We conducted grain size analysis, thermogravimetric analysis (organic matter and calcium carbonate content), pollen and macrofossil analysis, and determined the oxygen and carbon stable isotope ratios of biogenic carbonate (opercula of the freshwater gastropod Bithynia tentaculata). The chronology of the core is based on AMS 14C dating and pollen biostratigraphical correlation. The pollen and macrofossil studies reveal that the core site was a lake environment during the Allerød and Younger Dryas periods. The oxygen isotope record in conjunction with organic matter and carbonate content are believed to have captured the intra-Allerød Cold Period (IACP). The synchronous variation of oxygen and carbon isotopes with calcium carbonate content indicates a dominant evaporation effect on carbonate chemistry of the lake environments during the warm Allerød interstadial. End-member modelling decomposes the grain-size distributions into two sandy end members (bed load) and two silty-clayey end members (suspended load). In order to highlight the flood signal, we constructed two flood energy indexes (FEI-1 and FEI-2) that reflect the coarseness of the suspended load and bed load, respectively. Both indexes show a relatively high flood condition during the IACP, followed by a low flood phase in the Late Allerød and quickly intensified flood conditions at the onset of the Younger Dryas. In the second phase of the Younger Dryas, deposition of sandy aeolian sediments to the core site complicates the paleoflood identification using FEI-2 (bed load). This study shows a high sensitivity of the hydrological process and sedimentary environment at the Lower Meuse to the regional climate system.

Chronology of terraces in the Rio Grande rift, Socorro basin, New Mexico: Implications for terrace formation

AbstractThe Rio Grande rift hosts a remarkable record of Quaternary river incision preserved in an alluvial terrace sequence that has been studied for more than a century. However, our understanding of Rio Grande incision history in central New Mexico since the end of basin filling ca. 0.78 Ma remains hampered by poor age control. Robust correlations among Rio Grande terrace sequences in central and southern New Mexico are lacking, making it difficult to address important process-related questions about terrace formation in continental-scale river systems. We present new age controls using a combination of 40Ar/39Ar, 36Cl surface-exposure, and 14C dating techniques from alluvial deposits in the central New Mexico Socorro area to document the late Quaternary incision history of the Rio Grande. These new age controls (1) provide constraints to establish a firm foundation for Socorro basin terrace stratigraphy, (2) allow terrace correlations within the rift basin, and (3) enable testing of alternative models of terrace formation. We identified and mapped a high geomorphic surface interpreted to represent the end of basin filling in the Socorro area and five distinct, post–Santa Fe Group (ca. 0.78 Ma) alloformations and associated geomorphic surfaces using photogrammetric methods, soil characterization, and stratigraphic descriptions. Terrace deposits exhibit tread heights up to 70 m above the valley floor and are 5 to >30 m thick. Their fills generally have pebble-to-cobble bases overlain by fine-to-pebbly sand and local thin silt and clay tops. Alluvial-fan terraces and associated geomorphic surfaces grade to former valley levels defined by axial terrace treads. Carbon-14 ages from detrital charcoal above and below a buried tributary terrace tread show that the most recent aggradation event persisted until ca. 3 ka during the transition from glacial to modern climate conditions. Drill-log data show widespread valley fill ∼30 m thick that began aggrading after glacial retreat in northern New Mexico and southern Colorado (ca. 14 ka). Aggradation during this transition was likely due to hillslope destabilization, increased sediment yield, decreased runoff, and reduced stream competence. Chlorine-36 ages imply similar controls on earlier terraces that have surface ages of ca. 27–29, 64–70, and 135 ka, and suggest net incision during glacial expansions when increased runoff favored down-cutting and bedload mobilization. Our terrace chronology supports existing climate-response models of arid environments and links tributary responses to the axial Rio Grande system throughout the central Rio Grande rift. The terrace chronology also reflects a transition from modest (60 m/m.y.) to rapid (300 m/m.y.) incision between 610 and 135 ka, similar to patterns observed throughout the Rio Grande rift and the western United States in general.

The shaping of erosional landscapes by internal dynamics

Erosional landscapes transport sediment downstream, host natural hazards and are geologically active. While perturbations in external forcing, particularly climate and tectonics, sculpt erosional landscapes, similar landforms can be created by internal dynamics, that is, feedbacks between topography, erosion and sediment transport that occur independent of external perturbations. Internal system responses, termed autogenic dynamics, can remain active as landscapes adjust to perturbations in forcing, allowing for complex responses to external perturbations that potentially obscure links between external forcing, topographic form and sedimentary archives. Autogenic dynamics are being increasingly recognized in depositional systems, yet understanding of autogenic dynamics in erosional landscapes is nascent. In this Review, we discuss the mechanisms that contribute to internal dynamics in erosional landscapes. We use examples of autogenic terrace formation, knickpoint formation and river-basin reorganization to show how autogenic dynamics that occur over spatial scales of metres and temporal scales of hours can influence the evolution of mountain ranges over Myr periods. Unravelling the mechanics of autogenic processes allows the interplay of internal dynamics and external forcing to be explored and provides a framework to assess the influence of erosional processes in the geologic record. The morphology of erosional landscapes is often considered to be set by climate and/or tectonics; however, similar topographic features can arise through internal processes and feedbacks. This Review considers how the internal and external processes drive landscapes evolution, and how such processes can be differentiated in topographic and stratigraphic records.

Correcting MIS5e and 5a sea-level estimates for tectonic uplift, an example from southern California

Along tectonically active margins, the difference in elevations between global sea levels during highstands and uplifted marine terraces is a function of both tectonics and glacial-isostatic adjustment (GIA). However, disentangling the relative influence of these two processes remains a challenge for those trying to gain insights into either process. In this study, we outline a strategy for isolating the tectonic contribution to marine isotope stage (MIS) 5e and 5a marine terrace elevations for the southern California coast by determining the cosmogenic radionuclide burial age and elevation of the early Pleistocene (1.48 ± 0.17 Ma) Clairemont Terrace in San Diego. Using this older terrace as a datum for calculating tectonic uplift rate provides a much longer time period to average out uncertainties in past local or relative sea levels (RSL) that arise from ambiguities in GIA parameters and global meltwater volumes. The assumption of constant uplift rates is warranted for this portion of the California coast given its relatively simple tectonic setting on the rift flank of the Salton Trough. From this approach, we determine an average uplift rate of 0.066 ± 0.020 mm/yr or 0.055 ± 0.013 mm/yr, depending on the RSL model used for the time of the Clairemont Terrace formation, for much of the San Diego coastline. Correcting for this tectonic uplift rate leaves an estimate of 15.1 + 2.6/-3.1 m (16.4 + 1.9/-2.6 m) and 4.8 ± 1.9 m (5.6 ± 1.5 m) for RSL during MIS5e and MIS5a, respectively. These new estimates of MIS5e and MIS5a sea levels along the southern California coast provide important constraints on GIA parameters and former ocean and ice volumes.

Diffusion of Nanobubbles in fcc Aluminum

The existing theories of diffusion of gas-filled and empty bubbles in solids as yet do not have sufficient predictive power and require refinements that can be made using simulation. The method of the accelerated molecular dynamics simulation of the bubble drift in a pressure gradient is theoretically substantiated in this work. This method is used to calculate the diffusion coefficient of empty nanobubbles in aluminum. The theory of diffusion by means of the formation of critical terraces on the faces is supplemented in such a way that there is no contradiction with the continuous model for macroscopic dimensions. The simulation results show the key role of the formation mechanism of terraces in nanobubbles and confirm the amended theory. The inclusion of the effect of gas makes it possible to compare the simulation results with experimental data. The comparison also confirms the formation mechanism of terraces.

Constraining Late Quaternary Crustal Shortening in the Eastern Qilian Shan From Deformed River Terraces

AbstractThe Qilian Shan, located in the northeastern Tibet, is under strong tectonic activity and earthquake motion due to the propagation of the plateau. At the mountain front of the eastern Qilian Shan, the Tongziba River, in the southern Zhangye Basin, flows northward and successively cuts the Minle‐Damaying Fault and the Yonggu Anticline, two parallel structures within the Frontal Thrust system of the Qilian Shan. Here we present a detailed record of seven strath terraces of this river that documents the history of active deformation of the two structures. Based on the estimated crustal shortening distance from the deformed terraces and the terrace formation age constrained by AMS14C and optically stimulated luminescence (OSL) dating, a horizontal slip rate of 1.4 ± 0.5 mm/year of the Minle‐Damaying Fault is constrained since 16.7 ± 1.8 kyr, and a shortening rate of 1.3 ± 0.4 mm/year across the Yonggu Anticline has been estimated in a similar time frame, respectively. In total, the shortening rate across the mountain front is estimated to be 2.7 ± 0.6 mm/year. GPS data show a similar modern shortening rate in this area, which indicates the rate of crustal shortening may be comparable in the modern and 104‐year scales. Our study supports a higher crustal shortening rate along the mountain front of the eastern Qilian Shan than that of the western Qilian Shan since the Late Quaternary.

Luminescence chronology of the key-Middle Paleolithic site Khotylevo I (Western Russia) - Implications for the timing of occupation, site formation and landscape evolution

Here we present the luminescence chronology for the Middle Paleolithic open-air site of Khotylevo I, area I-6-2, in Western Russia. Even with a sizable number of such sites available on the Russian Plain, to our knowledge, no successful corresponding luminescence dating has been published before. Coupled with extensive sedimentological logs and grain-size analysis, our data is further used to infer the palaeoenvironmental conditions on site as well as the landscape-forming processes of the wider region. As the site is contained within the sediments of the 2nd fluvial terrace, our high-resolution chronostratigraphy is a valuable contribution to the understanding of this widespread phenomenon and Late Pleistocene geo-climatic events on the Russian Plain. For the formation of the 2nd terrace, a full incision/aggradation cycle was detected with a duration from MIS 5c/5b to MIS 3. Our results indicate that late Middle Paleolithic human occupation took place during the more ameliorate Early Weichselian phase of MIS 5a. Furthermore, the dates for Khotylevo I-6-2 prove the onset of the late Middle Paleolithic Keilmessergruppen occurred as early as MIS 5a. The archeological comparison with other numerically dated Late Middle Paleolithic assemblages across the northern central European Plain suggests a complex picture of population dynamics between MIS 5a and MIS 3.

Late Pleistocene-Holocene landscape evolution in the lower Peixe river, Brazil: A meandering river valley

This study investigated the lower terrace and floodplain formation in the lower Peixe River in southeastern Brazil. Morphologic, sedimentologic and geochronologic analyses in this meandering tributary of the Paraná River allowed an integrated approach to reconstructing fluvial changes from the late Pleistocene. Geomorphic units were mapped with Global Navigation Satellite System, satellite imagery and digital surface model interpretation, and sedimentary facies and radiocarbon (14C) dating analyses were performed on palaeochannels and backswamps. The palaeochannels on the lower terrace indicate fluvial activity during the late Pleistocene, torrential flows during the Northgrippian stage, and abandonments during the Meghalayan stage. The backswamp evaluated on the lower terrace documents the depositional change from oxbow lake abandonment in the Greenlandian stage to tributary flow, which passes flows over the palaeodrainage during flood episodes, while another backswamp in the floodplain highlights an intense morphodynamic removal of terrace deposits. An incisive phase during the Meghalayan stage is the main event responsible for establishing the current fluvial landscape, which promotes the formation of the lower terrace and floodplain. Local variations (i.e., tributary flows) in the degradation process on the terraces results in a topographical and morphological contrast between corresponding geochronologic units. Therefore, adjustment stages in the fluvial relief drive wetland variability in the fill terraces, which are fundamental to understanding degradational processes and formulating environmental management policies.

Cosmogenic10Be and36Cl geochronology of cryoplanation terraces in the Alaskan Yukon-Tanana Upland

ABSTRACTCryoplanation terraces are prominent but enigmatic landforms found in present and past periglacial environments. Geomorphologists have debated for more than a century over processes involved in the formation of these elevated, step-like, bedrock features. Presented here are the first numerical surface exposure ages and scarp retreat rates from cryoplanation terraces in the Yukon-Tanana Upland (YTU) in Alaska, part of unglaciated eastern Beringia, obtained from terrestrial cosmogenic nuclides (TCN) in surface boulders. Ages comprise six10Be TCN ages from two terrace treads near Eagle Summit and six36Cl ages from two treads on Mt. Fairplay. Based on these exposure ages, scarps at both locations were last actively eroding from 49 to 22.4 ka. Both locations exhibit time-transgressive development, particularly near scarp-tread junctions. Boulder exposure ages and distances between sampled boulder locations were used to estimate scarp retreat rates of 0.11 to 0.56 cm/yr. These numerical exposure ages presented here demonstrate that the cryoplanation terraces in the YTU are diachronous surfaces actively eroding during multiple cold intervals. With these results, hypotheses for cryoplanation terrace formation are discussed and evaluated for the YTU, including those based on geologic structure, nivation, and the influence of permafrost.

Catalytic Etching of Platinoid Gauzes during the Oxidation of Ammonia by Air: Etching of the Frontal Surface of the Platinoid Gauze in the Course of NH3 Oxidation at 1133 K

The morphology, microstructure, and chemical composition of the surface and near-surface layers of polycrystalline wire of an industrial platinoid gauze composed of Pt (81 wt %), Pd (15 wt %), Rh (3.5 wt %), and Ru (0.5 wt %) are investigated by scanning electron microscopy and energy dispersive X-ray spectroscopy. After oxidizing NH3 with air at T = 1133 K under a pressure of 3.6 bar for 50 h, a continuous rough layer of the cauliflower-type agglomerates formed during catalytic etching is detected on the frontal surface of the gauze. On the surface of wire fragments from 100 to 150 μm in size with a smooth micrograined structure, nanometer-size etch pits are detected at a concentration of 1.0 × 108–6.0 × 108 cm–2, which may be etching sites of the hotspot type. The growth of etch pits and the formation of crystalline terraces on the grain surface are caused by the surface diffusion of metal atoms. The continuous etching layer contains porous crystalline agglomerates (cauliflowers) with a linear size of 3 to 18 μm (mean size about 10 μm) at a concentration of 4.9 × 105 cm–2. Pores with a diameter of 0.1 to 1.7 μm are detected on the surface of agglomerates at a concentration of 1.3 × 107 cm–2. The specific surface area of the platinoid gauze, which is calculated from microscopic images taking into account the surface area of agglomerates and pores, is about 260 cm2/g. In the process of highly exothermic oxidation of NH3 with oxygen, on the surface of agglomerates with a low concentration of defects and in pore voids 5–15 μm in width and up to 10 μm in depth with an increased specific surface area and a high concentration of defects, vapor of volatile oxides and metals that are formed at hot regions of the bottom of pore voids can be condensed on the overlaying cold regions of the surface of agglomerates and single crystals. These processes give rise to the formation of a continuous etching layer of porous crystalline agglomerates, massive single crystals, and deep pore voids. The formed etching layer substantially increases the specific surface area of the catalyst, which leads to an increase in the volumetric rate of NH3 oxidation that accelerates the etching process.

Development of a Holocene glacier-fed composite alluvial fan based on surface exposure-age dating techniques: The Illåe fan, Jotunheimen, Norway

Holocene development of a composite alpine alluvial fan is reconstructed and dated based on its geomorphology and Schmidt-hammer exposure-age dating (SHD), supplemented by terrestrial cosmogenic-nuclide dating (TCND), lichenometry, radiocarbon dating, soil development, and palaeohydrological analysis. SHD ages of 7080 ± 450 to 8220 ± 440 years and a TCND age of 6075 ± 1220 years from the fan surface indicate that fan aggradation occurred in the early Holocene through episodic debris floods (phase 1) in response to paraglacial processes following deglaciation of the catchment (~9.7 ka). Stabilisation during the Holocene Thermal Maximum (phase 2) was followed by re-activation of the fan, involving entrenchment and terrace formation (phase 3), which occurred in response to neoglaciation after ~5.5 ka and culminated in the Little Ice Age. The main control on fan development was the effect of the changing extent of glaciers in the catchment on sediment supply, initially evinced in high-magnitude debris floods (hyperconcentrated flows) and later in water floods (typical fluvial processes). Aggradation switched to stabilisation as paraglacial activity waned, while later entrenchment was associated with relatively low bedload. Results provide the basis of a conceptual model of alluvial fan evolution for glacierized catchments related to Holocene environmental change.

Climate-driven formation of fluvial terraces across the Tibetan Plateau since 200 ka: A review

The causes of terrace formation in active orogenic belts have long been studied. Here, we present a synthesis of 147 available papers on the ages of Quaternary terraces within the Tibetan Plateau and along the surrounding orogenic belts. More than 1500 ages were collected to establish a database for exploring the causes of fluvial terrace formation. Because the age data were collected from different settings, ages younger than 200 ka were grouped into three regional climate systems: the westerlies, Indian summer monsoon, and East Asian summer monsoon. We further examined the relationship between terrace formation and climate change, as well as the contribution of tectonic uplift. Our results indicate that the intervals of fluvial terrace formation are synchronous with transitions in global climate from cooler to warmer conditions (stadials to interstadials). We propose that the formation of fluvial terraces across the Tibetan Plateau has been controlled mainly by cyclical climate changes, although there is not a one-to-one correspondence.

Pleistocene landscape evolution in the Avon valley, southern Britain: Optical dating of terrace formation and Palaeolithic archaeology

This paper presents the first comprehensive Optically Stimulated Luminescence dating programme from a sequence of Pleistocene river terraces in the Avon valley (Wiltshire-Hampshire-Dorset), southern Britain. These results offer the most complete chronometric framework for Pleistocene landscape evolution and Palaeolithic occupation in the Avon valley, allowing for the first time: (1) an assessment of the timing of terrace formation and landscape evolution, (2) the dating of hominin presence in the area, and (3) an investigation of the relationship between terrace formation and Quaternary climatic change. Analysis of 25 samples collected from terraces 10 and 7 to 4 show that the middle Avon terraces formed in response to the main Pleistocene climatic oscillations (Marine Isotope Stages (MIS) 10, 8, 6) and that fluvial mechanisms changed through time, resulting in three different types of terrace architecture. The highest and oldest deposits are compound terraces deposited during the Early Pleistocene before the Mid Pleistocene Transition. The middle reach of the valley is characterised by well-developed strath terraces overlain with thick fluvial deposits, reflecting the greater degree of incision in response to the increased amplitude of climate cycles in the Middle Pleistocene. The youngest deposits in the confined modern floodplain represent cut-and-fill terraces deposited after MIS5e. The results indicate that the two main Palaeolithic sites in the area, Milford Hill and Woodgreen, date to between at least MIS 10 and 8 with a pre-MIS 10 human occupation at a third main site at Bemerton. This is significant because the sites date to a period previously associated with a decline in hominin presence in Britain. The dating of the Avon valley terrace sequence highlights the complex nature of terrace formation during the Pleistocene and the need to critically reassess the chronological understanding of these fluvial archives in southern Britain. This research demonstrates that with a detailed and multidisciplinary approach shifts in hominin landscape use can be discovered, providing new information on hominin behavioural change during the Pleistocene.

Late Pleistocene-Holocene lake terraces, water level change, and active tectonics: Eastern coast of Lake Van, Eastern Anatolia, Turkey

Data obtained from mapping, topographic analysis and radiometric dating completed in the epicentral region of the 23 October 2011 Van earthquake reveals the role of tectonic processes on the terrace formation. An investigation of seven terraces between Bardakçı and Yeşilsu villages on the hanging wall of the Van Fault Zone indicates changes in the Holocene coastline of Lake Van and provides information regarding the relationships between the changes and tectonic uplift in the region. Taking note of the elevation of the terraces, seven terrace levels appeared within the last 30 ka. Three of them are interpreted as tectonic origin. According to the dates and heights of the tectonic terrace levels, the mean annual uplift rate is calculated to be ≥ 2 mm/year on the hanging wall of the Van Fault Zone. Additionally, mapping occurred of folds with generally E-W direction, occasionally NE and NW orientation, developed within the Quaternary deposits. Assessment of the obtained data shows uplifting of the area, with the effect of reverse faults/thrusts and folds developed by the N–S compression during the Plio-Quaternary an important factor in terrace development in the region.

Early Pleistocene River Terraces of the Gediz River, Turkey: The role of faulting, fracturing, volcanism and travertines in their genesis

Reconstructing and interpreting past hydrological system changes from the Quaternary sediment-landform record presents many challenges especially when trying to establish causality. In such circumstances attempting to isolate individual drivers is perhaps unrealistic and thus inferences are made with respect to the combined influence of multiple controls and constraints. In this paper we seek to interpret the landscape responses recorded in the sediment-landform record of the Early Pleistocene Gediz valley, western Turkey, within the context of interacting geodynamic and hydrodynamic system changes.Our earlier work on the Gediz sequence established the presence of a rich fluvial archive constrained by a comprehensive geochronology from overlying lava flows. Repeated damming of the Gediz valley floor and consequent re-routing of water flow, testifies to a direct connection between fluvial activity and volcanism. This volcanism has been linked to regional tectonic extension with regional uplift promoted as a major driver of the progressive river incision of the Gediz River over the Quaternary. This incision has been punctuated by periods of deposition dictated by sediment and water budgets controlled principally by fluctuating climate and consequent vegetation change. Recently however, the significance of more local fault movements and fracturing has been recognised and here we examine and attempt to quantify these geodynamics in greater detail. In addition, we examine and describe, for the first time, extensive associated travertine deposits. Isotopic analysis of these travertines confirms their thermogenic origin and directly links their creation to the faulting/fracturing, volcanism and the recycling of calcium-rich groundwater. The formation of mounds and sheets extend onto their contemporary valley floors, thus directly connecting the fluvial and travertine archives and allowing linkage between surface and subsurface hydrological change.By utilising both the fluvial and travertine archives a more complex picture of landscape evolution emerges. The youngest terraces (<GT6) appear to be driven by local fault movement associated with the onset of volcanism and thus the link with fluctuating climates, as demonstrated in the higher terraces (GT7 +), is unclear. Detailed observations suggest formation of these lower terraces is also conditional on the local substrates. Here it appears that GT5-GT1 form in response to the creation of a knickpoint where the river intersects the faults in areas of hard basement rock. Hence, this response is highly localized, dependent on the immediate geometry and structure of the underlying strata. The presence of complex basement topography also plays a key role in generating ground water pressure and thus the creation of travertine mounds.The Gediz sequence demonstrates increasing complexity. There is no reason to suggest this is unusual. Although climate and tectonics remain as key drivers the local landscape response is also conditioned by many additional factors. While it is tempting to search for global patterns (“the big picture”), such reduced complexity may be over simplistic. Recognising complexity requires detailed observation and therefore more emphasis on “the smaller picture” which can only be obtained through extensive field observation.

Determining the Age of Terrace Formation Using Luminescence Dating—A Case of the Yellow River Terraces in the Baode Area, China

Dating fluvial terraces has long been a challenge for geologists and geomorphologists, because terrace straths and treads are not usually directly dated. In this study, the formation ages of the Yellow River terraces in the Baode area in China were determined by dating fluvial deposits overlying bedrock straths using optically stimulated luminescence (OSL) dating techniques. Seven terraces (from the lowest terrace T1 to the highest terrace T7) in the study area were recognized, and they are characterized by thick fluvial terrace deposits overlaid by loess sediments. Twenty-five samples from nine terrace sections were dated to about 2–200 ka. The OSL ages (120–190 ka) of the fluvial samples from higher terraces (T3–T6) seem to be reliable based on their luminescence properties and stratigraphic consistency, but the geomorphologic and stratigraphic evidence show that these ages should be underestimated, because they are generally similar to those of the samples from the lower terrace (T2). The formation ages of the terrace straths and treads for the T1 terrace were deduced to be about 44 ka and 36 ka, respectively, based on the deposition rates of the fluvial terrace deposits, and the T2 terrace has the same strath and tread formation age of about 135 ka. The incision rate was calculated to be about 0.35 mm/ka for the past 135 ka, and the uplift rate pattern suggests that the Ordos Plateau behaves as a rigid block. Based on our previous investigations on the Yellow River terraces and the results in this study, we consider that the formation ages of terrace straths and treads calculated using deposition rates of terrace fluvial sediments can overcome problems associated with age underestimation or overestimation of strath or fill terraces based on the single age of one fluvial terrace sample. The implication is that, for accurate dating of terrace formation, terrace sections should be systematically sampled and dated.

ROLE OF TECTONIC REGIME IN THE DEVELOPMENT OF CONCEDIMENTAL DEPOSITS OF CHOCRATIC ANTICLINE FOLD

In the article based on the data of the field studies for 2008-2013, the sequence of tectonic movements in the formation of the Chocratic anticlinical fold is justified on the basis of a facial analysis. The Kerch Peninsula is a unique region where both anthropogenic and subaerial deposits of shelf and marine formations are widely represented. Of particular interest is located in the north-eastern part of the peninsula of Lake Chocrac with the anticline structure of the same name, which is part of the system of folds of the Lychagin shaft. Using the methodology of reconstruction of geological events and geological and structural analysis of Quaternary sediment, condimentary deposits of the Chocratic anticline fold were identified for the first time, the sequence of terrace formation and the impact of tectonic movements on its formation were shown. It was shown that the formation of sediments of the Karangad period on the north-eastern shore of Lake Chocratic differs from the formation of other sediments of that time on the Crimean Peninsula.Features of lithologic-facial composition of the Chocratic anticline fold require a comprehensive approach to their study to more accurately reflect the conditions of sedimentation and geological processes associated with formation fluids. It is well known that formation fluids are responsible for the "clay" tectonics, which are widely distributed on the territory of the Kerch Peninsula and the nearby Kerch shelf.The authors conclude that the tectonic movements that formed the Chocratic anticline occurred from the end of the early quarantine to the time when the leveling surface appeared.

Fluvial activity in the Lomas de Lachay during the upper Pleistocene and Holocene

The Lomas de Lachay are the first ridges of the western slope of the Andes, about 100 km northward from Lima. This study examines the structure and age of fluvial terraces in the valleys of different orders. Accumulation of alluvium took place during the periods ca. 57 ka, 24–15 ka and likely the Late Glacial/Early Holocene. These periods correlate with pluvial Minchin, Tauca, and probably Coipasa (when fluvial activity in some Peruvian valleys was also noted). These alluviation phases were separated by erosion and terrace formation. The progressive aridization of the climate caused LGM aeolian covers to appear (21–18 ka) for the first time. Wind-blown sands fossilized older forms of relief and covered the valley slopes in the border zone between the lomas and desert. In the Holocene period, three types of geosystems developed in line with different morphogenetic activity: Coastal Desert (typified by a prevalence of aeolian processes); Lomas (very stable, with a prevalence of chemical weathering – tafones); and Mountain Desert (typified by very active fluvial and slope systems during El Nino events). Settlement phases in Lomas de Lachay were related to a high frequency of ENSO, and intensive grazing in recent centuries caused the creation of terracettes and buried soils on the slopes.