Major River Valleys Research Articles

Geoecological risks in the valleys of small rivers of the forest-steppe zone of the Russian plain (on the example of the Chuvash Republic)

The Chuvash Republic belongs to the territories with a high frequency of occurrence of emergency situations of moderate severity. This is due to the intensive economic development of the region. The probability and intensity of the manifestation of georisks is different for individual landscapes, therefore it needs a detailed study. The study includes the study of the probability of the development of slope, climatic, hydrological risks, and the risk of wildfires on the territory of the Chuvash Republic. The analysis showed that the slope type of geoecological risk is confined to the river valleys of the region and has maximum values in the north of the Chuvash Republic. A high risk of flooding and flooding exists in the valleys of major rivers of the region (Volga, Sura) and their tributaries of the first order. On other watercourses, the hydrological risk is not significant. Climate and weather risks are associated with hurricane winds and dry winds. The southeastern part of the region suffers the most from them. The risk of fires depends on the composition and age of the stand. The maximum risk values are typical for the Prisursky forest area (southern and southwestern parts of the region). Based on the data obtained, the classification of the districts of the Chuvash Republic by the size of the georisks was carried out. Four groups of districts were identified according to the probability of natural emergencies and the main factors of their occurrence were described.

A review of Palaeolithic sites associated with gravel deposits in India

Abstract Rivers and river-borne deposits have always been a major attraction for hominins as an important source of sustenance and settlements. Hence, fluvial deposits have long been an important source of evidence for early human occupation throughout the Old World. Apart from being an important palaeoclimatic marker, fluvial sequences have provided archaeologists with frameworks for correlation, along with Palaeolithic markers discovered within them. Moreover, given the influx of sediments eroded and deposited by Indian rivers, these could have acted as a centre of hominin activities. Palaeolithic research in India has been concentrated around some of its major river valleys, which have yielded a rich record of hominin occupation. So far, 305 Palaeolithic sites have been reported from a gravel context throughout the country, yielding Lower to Upper Palaeolithic, Mesolithic and Neolithic evidence. However, most of the derived evidence is secondary deposits and stands contested based on its contextuality. Nevertheless, its importance as a source of information about hominin activity cannot be underestimated. This review presents a provisional synthesis of all of the Indian Palaeolithic sites reported from gravel contexts, thereby presenting scope for future multidisciplinary research at these localities.

Spatial and Temporal Variations of Freezing and Thawing Indices From 1960 to 2020 in Mongolia

Mongolia is one of the most sensitive regions to climate change, located in the transition of several natural and permafrost zones. Long-term trends in air freezing and thawing indices can therefore enhance our understanding of climate change. This study focuses on changes of the spatiotemporal patterns in air freezing and thawing indices over Mongolia from 1960 to 2020, using observations at 30 meteorological stations. Our results shows that the freezing index ranges from −945.5 to −4,793.6°C day, while the thawing index ranges from 1,164.4 to 4,021.3°C day over Mongolia, and their spatial patterns clearly link to the latitude and altitude. During the study period, the trend in the thawing index (14.4°C-day per year) was larger than the trend in the freezing index (up to −10.1°C-day per year), which results in the net increase of air temperature by 2.4°C across Mongolia. Overall, the increase in the thawing index was larger in the low latitudes and altitudes (e.g., the Gobi-desert, steppes, the Great lake depression and major river valleys) than in high latitudes and altitudes (mountain regions), while it was the opposite for the freezing index. The highest values for both thawing index and freezing index (i.e. the least negative values) have occurred during the last 2 decades. As the trends in the freezing and thawing indices and mean annual air temperature confirm intensive climate warming, increased permafrost degradation and shallower seasonally frozen ground are expected throughout Mongolia.

The changing malaria risk patterns in East‐Central Europe and the North Balkans in the last 27 000 years

ABSTRACTSoutheast Europe has historically been at the crossroads of migration routes between Western Asia and Europe. In the Holocene, this area might have been home to malaria. However, it is questionable when malaria arrived in this area and whether it could persist continuously or not in the Holocene. To begin to answer these questions, the July potential generation number of two malaria parasites were modelled, based on the reconstructed mean July temperatures of 52 times in the last 27 000 years. The results indicate that in the late Pleistocene era (27–12 kya bp), vivax malaria might have been present in the south‐east Black Sea and Aegean Sea's coastal areas. Vivax malaria could also be present in the Pannonian Basin and the inner parts of the North Balkans at least from the mid‐Greenlandian period (~10 kya bp). Although it is questionable whether falciparum malaria could be endemic in the Pannonian Basin during the mid‐Holocene climate optimum (~6 kya bp), this malaria plausibly could be endemic from the Neolithic era (~12–6.5 kya bp) in the major river valleys of the North Balkan region, millennia ahead of the Graeco‐Roman times (8th century bce to 6th century ce).

Timing, rates and geomorphic controls on holocene loess and aeolian sand deposition using multiple chronometric methods, southeastern Cordillera, Alberta, Canada

Glacier-fed river systems represent potentially significant sediment sources for aeolian processes owing to sediment production, flow seasonality, and winds within mountain settings. We investigate the timing and rates of Holocene loess and aeolian sand deposition in three major river valleys (Bow, North Saskatchewan and Athabasca) of the southeastern Canadian Cordillera through aeolian stratigraphy and dating of sedimentary materials. Source sediments are glacially-derived, seasonally-exposed alluvial deposits. Variation in river morphology promotes source-sediment deposition influenced by bedrock configuration, tributary stream deposition and alluvial fans. Two main settings for aeolian deposition are source-proximal valley-bottom sites and more distal lower-valley sites in sub-alpine and montane forest ecozones. Dating is well-constrained by radiocarbon ages and tephrochronology. Quartz optical dating is complicated, likely owing to minimal recycling of grains and quartz provenance. Mass accumulation rates (MARs) indicate that aeolian deposition was initiated soon after deglaciation and has occurred nearly continuously for at least 10000 years. Loess MARs ranged between 100 and 2500 g·m−2·a−1 during the Holocene. Rates in the last 3000 years are generally two to three times higher than those observed for earlier periods, and are highest in most recent times. We attribute Holocene accumulation at these sites in general to fluvial source sediment availability and the efficacy of forested valleys as sediment traps. The late Holocene increase in MARs is primarily attributed to increased glacial silt and alluvial sediment supply during neoglacial fluctuations including the Little Ice Age.

Appraisal of Groundwater Potential of Fadama Areas within Northern Nigeria: A Review

Nigeria is a country endowed with alluvial aquifers that occur along major river valleys, in low lying areas which are frequent to flooding during the rainy season. They are scattered across the ecological zones of Guinea savannah, Sudan savannah and the Sahel Savannah and are the thickest along the river Niger and river Benue. The irrigated flood plains (Fadama) are formed by the deposition of transported weathered exogenic terrigenous materials derived from the surrounding basement rocks. These shallow aquifers are mostly unconfined and are recharged through flash flooding events which make them hold great groundwater resources for dry season farming. The fertility of the soils with their residual moisture content makes them attractive for dry season farming. The potential and importance of Fadama agriculture for food production and economic development are crucial, given the recent rising food prices, climatic changes, environmental risks associated with “modern” agriculture, modelled farming systems and population growth. Fadama areas are therefore of critical importance to the survival and economic development of millions of rural dwellers. This paper reviews the groundwater potential of the Floodplains of Fadama for dry farming systems in semi-arid northern Nigeria.

Gene flow and climate-associated genetic variation in a vagile habitat specialist.

Previous work in landscape genetics suggests that geographic isolation is of greater importance to genetic divergence than variation in environmental conditions. This is intuitive when configurations of suitable habitat are a dominant factor limiting dispersal and gene flow, but has not been thoroughly examined for habitat specialists with strong dispersal capability. Here, we evaluate the effects of geographic and environmental isolation on genetic divergence for a vagile invertebrate with high habitat specificity and a discrete dispersal life stage: Dod's Old World swallowtail butterfly, Papilio machaon dodi. In Canada, P. m. dodi are generally restricted to eroding habitat along major river valleys where their larval host plant occurs. A series of causal and linear mixed effects models indicate that divergence of genome-wide single nucleotide polymorphisms is best explained by a combination of environmental isolation (variation in summer temperatures) and geographic isolation (Euclidean distance). Interestingly, least-cost path and circuit distances through a resistance surface parameterized as the inverse of habitat suitability were not supported. This suggests that, although habitat associations of many butterflies are specific due to reproductive requirements, habitat suitability and landscape permeability are not equivalent concepts due to considerable adult vagility. We infer that divergent selection related to variation in summer temperatures has produced two genetic clusters within P. m. dodi, differing in voltinism and diapause propensity. Within the next century, temperatures are predicted to rise by amounts greater than the present-day difference between regions of the genetic clusters, potentially affecting the persistence of the northern cluster under continued climate change.

Spatial genetic structure of Rocky Mountain bighorn sheep (Ovis canadensis canadensis) at the northern limit of their native range

The Canadian Rocky Mountains are one of the few places on Earth where the spatial genetic structure of wide-ranging species has been relatively unaffected by anthropogenic disturbance. We characterized the spatial genetic structure of Rocky Mountain bighorn sheep (Ovis canadensis canadensis Shaw, 1804) in the northern portion of their range. Using microsatellites from 1495 individuals and mitochondrial DNA sequences from 188 individuals, we examined both broad- and fine-scale spatial genetic structure, assessed sex-biased gene flow within the northern portion of the species range, and identified geographic patterns of genetic diversity. We found that broad-scale spatial genetic structure was consistent with barriers to movement created by major river valleys. The fine-scale spatial genetic structure was characterized by a strong isolation-by-distance pattern, and analysis of neighborhood size using spatial autocorrelation indicated gene flow frequently occurred over distances of up to 100 km. However, analysis of sex-specific spatial autocorrelation and analysis of mitochondrial haplotype distributions failed to detect any evidence of sex-biased gene flow. Finally, our analyses reveal decreasing genetic diversity with increasing latitude, consistent with patterns of post-glacial recolonization of the Rocky Mountains.

Soft Sediment Deformation Structures in Quaternary Sediments from Dadra and Nagar Haveli, Western India

Abstract Quaternary sediments are preserved in disconnected patches along the middle and lower reaches of major river valleys like Damanganga, Par, Ratakhadi and Dongarkhadi in the Dadra and Nagar Haveli region of Konkan coastal belt, Western India. These deposits mainly consist of stratified sand, silt, clay and gravel beds. The study area has been earlier affected by moderate earthquakes. The identified soft-sediment deformation structures (SSDS) are mainly developed in the sand silt, sand gravel and clay beds; and includes intrusive sedimentary bodies (dykes and sills), slump structures, suspended clast blocks and convolute structures. The nature, shape and dimension of SSDS suggest that the trigger mechanism and driving forces for the origin of these structures were seismic shock waves. Sediment loading and storm events as a trigger for the SSDS are less likely the reason and the proximity of these structures to the faults support the inference that it may be of seismic origin. Deformation in the Quaternary sediments of Dadra and Nagar Haveli imply the presence of neotectonic activity and points to an earthquake of magnitude >5.5 that struck the study area after sediment deposition.

Luminescence dating of Quaternary alluvial successions, Sellicks Creek, South Mount Lofty Ranges, southern Australia

Quaternary alluvial and colluvial sediments infill major river valleys and form alluvial fans and colluvium-filled bedrock depressions on the range fronts and within the Mount Lofty Ranges of southern Australia. A complex association of alluvial successions occurs in the Sellicks Creek drainage basin, as revealed from lithostratigraphy, physical landscape setting and optically stimulated luminescence (OSL) ages. Correlation of OSL ages with the Marine Oxygen Isotope record reveals that the alluvial successions represent multiple episodes of alluvial sedimentation since the penultimate glaciation (Marine Isotope Stage 6; MIS 6). The successions include a penultimate glacial maximum alluvium (Taringa Formation; 160 ± 15 ka; MIS 6), an unnamed alluvial succession (42 ± 3.2 ka; MIS 3), a late last glacial colluvial succession within bedrock depressions (ca 15 ka; MIS 2) and a late last glacial alluvium (ca 15 ka; MIS 2) in the lowest, distal portion of Sellicks Creek. In addition, the Waldeila Formation, a Holocene alluvium (3.5 ± 0.3 ka; MIS 1), and sediments deposited during a phase of Post-European Settlement Aggradation (PESA) are also identified. The age and spatial distribution of the red/brown successions, mapped as the Upper Pleistocene Pooraka Formation, directly relate to different topographic and tectonic settings. Neotectonic uplift locally enhanced erosion and sedimentation, while differences in drainage basin sizes along the margin of the ranges have influenced the timing and delivery of sediment in downstream locations. Close to the Willunga Fault Scarp at Sellicks Creek, sediments resembling the Pooraka Formation have yielded a pooled mean OSL age of 83.9 ± 7 ka (MIS 5a) corroborating the previously identified extended time range for deposition of the formation. Elsewhere, within major river valleys, the Pooraka Formation was deposited during the last interglacial maximum (128–118 ka; MIS 5e). In general, alluviation occurred during interglacial and interstadial pluvial events, while erosion predominated during drier glacial episodes. In both cases, contemporaneous erosion and sedimentation continued to affect the landscape. For example, in the Sellicks Creek drainage basin, which lies across an actively uplifting fault zone, late glacial age sediments (MIS 2) occur within the ranges and near the distal margin of the alluvial fan complex. OSL dating of the alluvial successions reported in this paper highlights linkages between the terrestrial and marine environments in association with sea-level (base-level) and climatic perturbations. While the alluvial successions relate largely to climatically driven changes, especially in major river valleys, tectonics, eustasy, geomorphic setting and topography have influenced erosion and sedimentation, especially on steep-sloped alluvial fan environments.KEY POINTSLuminescence dating of the Sellicks Creek alluvial fan complex reveals that sedimentation occurred predominantly during the later stages of glacial cycles accompanying lower sea-levels than present.Luminescence dating confirms that the stratigraphically lower portions of the Pooraka Formation are beyond the range of radiocarbon dating.Upper Pleistocene alluvial fan sedimentation at Sellicks Creek correlates with pluvial events in southeastern Australia.

A comprehensive approach to understanding flood risk drivers at the municipal level

During the period 1998–2017, floods were responsible for 11% of the loss of life and 23% of the economic loss caused by climate-related and geophysical-related disasters worldwide. An integrated and effective definition of flood risk management strategies therefore still requires synthesized and comprehensive knowledge about the driving forces of flood risk.In this study, 278 Portuguese municipalities are analyzed and classified according to flood hazard, exposure, and vulnerability. After evaluating the three components that describe risk, an index of the flood risk is calculated and a cluster analysis is further performed to understand the role of the risk drivers (hazard, exposure, and vulnerability) in each municipality. The proposed approach therefore provides flood risk indexes on a municipal basis, which are built upon different sources of both cell-by-cell data and an aggregation of municipal-level data that has been statistically validated. Municipalities both in the NW part of the country and along the valleys of major rivers demonstrate a significant superimposition of high levels of exposure and hazard, while vulnerability presents a disperse pattern throughout the country.The results obtained using this approach should contribute to the diversification of flood risk management strategies. This is still lacking in the majority of the national-level flood risk governance processes, namely those strategies that focus on the contingency of daily activities and those aiming at a long-term reduction of the exposure, vulnerability, and hazard components that shape flood disasters.

Daily Dietary Nutrition and Nutraceutical Intake in Agricultural Laborers of Hirakud Command Area, Sambalpur, Odisha, India

Sambalpur is considered as the rice bowl of Odisha for its cultivation activities due to the presence of hydroelectric power house Hirakud Dam, with total capacity of 5,896,000,000 m3, 55 km long and is one of the first major multipurpose river valley projects started after India's independence. It irrigates about 75,000 km2 (19×106 acres) of land and therefore, is considered as a blessing to the farmer families. As because of cultivation and allied activities, Agricultural Laborers (ALs) constitute a large portion of the active work force. Study on the nutritional intake in this important fraction of population is lacking. Present study was an attempt to know the food consumption pattern and nutritional intakes of ALs in Hirakud command area of Sambalpur district, India. Data were collected from 300 ALs, consisting of 150 from each gender. Daily dietary pattern and nutritional intake of respondent were calculated through 24 hours dietary recall method. It was observed that ALs consume all most all the food varieties available in Odisha. Cereal consumption was 6.80 and 1.77 % excess than the recommend value dietary allowance (RDA) by Indian Council for Medical Research (ICMR, in 1990). Except cereals, all other food consumption was below the RDA value in ALs. The intake of other food varieties in ALs was > 60% deficit from the RDA values. Consumption of milk was 97% less in case of male ALs and 98 % less in case of female ALs in comparison to the values suggested in RDA. Similarly, consumption of all nutrients was less than RDA norms except Vitamin -C in case of male ALs. The consumption of Niacin and Vitamin -C was excess in case of female ALs. Alternate low cost food supply is suggested to compensate such insufficient nutritional uptake by ALs in the study area.
 Keywords: Food, nutrient intake, nutraceuticals, nutritional status, 24 hours recall method

Geochemical and mineralogical characteristics of loess along northern Appalachian, USA major river systems appear driven by differences in meltwater source lithology

Eastern United States loess mapped by the U.S. Department of Agriculture, National Resources Conservation Service (USDA-NRCS) mostly occurs near major river systems like the Delaware and Susquehanna Rivers. The proximity of loess along major river valleys suggests late-Quaternary glacial meltwater sediments were dominant sediment sources for loess. Based on differing lithologies of meltwater deposits in these systems, we hypothesize that loess in each river system has a unique geochemical and mineralogical signature. To test this hypothesis, we examined pedons developed in loess parent materials, and adjacent to either the Delaware or West-Branch of the Susquehanna River, both of which carried large amounts of Wisconsinan outwash. Soils were analyzed for particle size distribution, clay mineralogy, and coarse and fine silt particle density, mineralogy, and geochemistry. Results show that while the pedons are similar in morphology, substantial differences exist in the pedons' textures, mineralogies, and geochemical compositions. We attribute the differences to parent material differences that stem from lithologically distinct sediment sources for loess from the two river systems. Susquehanna River loess has a higher particle density, and lower abundance of minerals such as Zr, base oxides (such as CaO), and rare earth elements. Discriminant analysis results suggest that developing a “loess fingerprint” for each river system based on major, minor and rare earth elements is possible, and likely to be useful in differentiating sources; however coarse silts may be a more effective fraction (than fine silts) for sediment sourcing, especially if rare earth elements are used.

Tree Species Composition and Forest Stratification along the Gradients in the Dry Deciduous Forests of Godavari Valley, Telangana, India

Abstract It is important to understand the tree species composition, abundance, species diversity and stratification in tropical dry deciduous forests that are under threat. A quadrat study was attempted in the dry deciduous forests along the ecological gradients in the Godavari Valley of northern Telangana, India. The study records the presence of 110 flowering plant taxa belonging to 82 genera and 37 families in 120 sampled plots, and there was enumeration of 15,192 individuals of ≥10 cm girth at breast height. Tectona grandis (teak) is the principal forest cover component in the region, which often formed pure stands in Adilabad and, to some extent, in Nizamabad districts. Further down to the Warangal district, teak was gradually replaced by Terminalia alata. Twenty tree species were found dominant at one place to the other, and the top 10 dominant taxa have shared nearly 41% of the total density of the forest cover. The tree relative density ranged from 0.007% to 20.84%. The values of Importance Value Index were between 0.245 (12 spp. including some exotics) and 32.6 (teak). These baseline data help to know the change detection along the gradients in the tropical forest ecosystem of a major river valley in the region and the drivers of change

Age and evolution of diachronous erosion surfaces in the Amazon: Combining (U-Th)/He and cosmogenic 3He records

(U-Th)/He geochronology of two weathered plateaus in the Carajás Mountains, Pará, Brazil, reveals a history of weathering spanning from ca. 80 Ma to the present for this high elevation (∼720 m) land surface. Cosmogenic 3He measurements of hematite pebbles and blocks cemented onto the plateaus at two sites, N1 and S11D, yield erosion rates as low as 0.09 and 0.08 m Ma−1, respectively. Thus, these results confirm that the plateau surfaces are nearly immune to physical erosion for tens of millions of years. (U-Th)/He geochronology of ferruginous duricrusts blanketing the low elevation (250–100 m) plains surrounding the Carajás Mountains yield results consistently younger than ∼10 Ma. The geochronology results also reveal that the low elevation plain is diachronous, becoming progressively younger towards the receding plateaus. The spatial distribution of (U-Th)/He ages permits reconstruction of the history of scarp retreat for the Carajás landscape, showing that scarp retreat along major river valleys may have been as fast as 20 km Ma−1 during tectonically active and humid periods in the Cenozoic. The cessation of scarp retreat at some sites suggests that metamorphosed banded iron-formations and quartzites provide effective barriers to retreating escarpments, helping to preserve some of the oldest continuously exposed land surfaces on Earth.

Conservation genetics of the eastern yellow-bellied racer (Coluber constrictor flaviventris) and bullsnake (Pituophis catenifer sayi): River valleys are critical features for snakes at northern range limits.

On the North American Great Plains, several snake species reach their northern range limit where they rely on sparsely distributed hibernacula located in major river valleys. Independent colonization histories for the river valleys and barriers to gene flow caused by the lack of suitable habitat between them may have produced genetically differentiated snake populations. To test this hypothesis, we used 10 microsatellite loci to examine the population structure of two species of conservation concern in Canada: the eastern yellow-bellied racer (Coluber constrictor flaviventris) and bullsnake (Pituophis catenifer sayi) in 3 major river valleys in southern Saskatchewan. Fixation indices (FST) showed that populations in river valleys were significantly differentiated for both species (racers, FST = 0.096, P = 0.001; bullsnakes FST = 0.045–0.157, P = 0.001). Bayesian assignment (STRUCTURE) and ordination (DAPC) strongly supported genetically differentiated groups in the geographically distinct river valleys. Finer-scale subdivision of populations within river valleys was not apparent based on our data, but is a topic that should be investigated further. Our findings highlight the importance of major river valleys for snakes at the northern extent of their ranges, and raise the possibility that populations in each river valley may warrant separate management strategies.

A revised species population estimate for the Bar-headed Goose (Anser indicus)

BackgroundThe Bar-headed Goose (Anser indicus) is a species that relies heavily on the plateau wetlands of Asia and whose population was thought to be declining. Over the past decade, south-central Tibet, one of the most important wintering grounds, supported large numbers of Bar-headed Geese, but the population had not been regularly monitored in this area.MethodsWe surveyed wintering Bar-headed Geese along the Yarlung Zangbo, Lhasa and Nyang Qu rivers, the three major river valleys and their tributaries in south-central Tibet in January 2014 and recorded their location, flock size and habitat utilization. Based on these data and the latest wintering counts elsewhere, we revised the population estimate for this species.ResultsWe recorded more than 67,000 Bar-headed Geese in south-central Tibet during January 2014. By geographic area, the geese were most abundant in the Lhasa River valley (38.5%) and the Nyang Qu River valley (31.0%), and by administrative division in Lhunzhub (27.2%) and Shigatse (26.7%). Bar-headed Geese were most often observed feeding in winter wheat fields and ploughed fields, resting on pastureland and marshes. The approximate number of 67,000 geese recorded in Tibet is more than four times the estimate of 1993 for the same region and exceeds the most recent world population estimate of 52,000–60,000. Based on our work in Tibet and the latest wintering counts available from other areas, we revised the estimated population size of this species to 97,000–118,000.ConclusionsOur result reveals a remarkable increase in the number of Bar-headed Geese wintering in south-central Tibet. This population increase most likely stems from a proliferation of cropland and especially winter wheat fields in south-central Tibet. This habitat improvement may also cause short-stopping of the Bar-headed Goose and thus reduce mortality of the geese that would otherwise undertake a somewhat daunting trans-Himalayan migration.

Midcontinental Native American population dynamics and late Holocene hydroclimate extremes

Climate’s influence on late Pre-Columbian (pre-1492 CE), maize-dependent Native American populations in the midcontinental United States (US) is poorly understood as regional paleoclimate records are sparse and/or provide conflicting perspectives. Here, we reconstruct regional changes in precipitation source and seasonality and local changes in warm-season duration and rainstorm events related to the Pacific North American pattern (PNA) using a 2100-year-long multi-proxy lake-sediment record from the midcontinental US. Wet midcontinental climate reflecting negative PNA-like conditions occurred during the Medieval Climate Anomaly (950–1250 CE) as Native American populations adopted intensive maize agriculture, facilitating population aggregation and the development of urban centers between 1000–1200 CE. Intensifying midcontinental socio-political instability and warfare between 1250–1350 CE corresponded with drier positive PNA-like conditions, culminating in the staggered abandonment of many major Native American river valley settlements and large urban centers between 1350–1450 CE during an especially severe warm-season drought. We hypothesize that this sustained drought interval rendered it difficult to support dense populations and large urban centers in the midcontinental US by destabilizing regional agricultural systems, thereby contributing to the host of socio-political factors that led to population reorganization and migration in the midcontinent and neighboring regions shortly before European contact.

Regionalization of local geomorphometric derivations for geological mapping in the sedimentary domain of central Amazônia

This paper reports procedures to prepare locally derived geomorphometric data for geological mapping at regional scale in central Amazônia. The size of the study area, approximately 1.5 million km2, and the prevailing flat topography of the targeted environment were the constraints motivating the aims, at spatial and numerical synthesis of the detailed geomorphometric information derived from SRTM DEM. The developed approach consisted in assigning single (average) values to terrain patches, to represent the regional distribution of pixel-based geomorphometric information (slope, profile curvature and relative relief). In analogy to the nature of sedimentary packs, patches were established as contiguous elevation strata, constructed through a procedure combining segmentation, filterings and range compressions. For slope only, pre-processing of locally derived data with median filtering effectively avoided the typical flattening of the regionalized results due to input distribution characteristics. Profile curvature was transformed into absolute values and thus a different meaning from the original (pixel) variable was considered in the interpretation, also avoiding the compensation of original values (positive and negative) tending to zero value when averaged through a regionally flat extension. Examinations near major river valleys showed patched elevation to depict alluvial terraces. In the interfluves and floodplains, contrasting patterns in the averaged variables among patches of similar elevations allowed the recognition of important relief features. In addition to the reduction of the distribution ranges, the correlation between regionalized geomorphometric variables was higher than observed in the originally local data, due to the thematic synthesis following regionalization. Depth of dissection, claimed to be related to the relative age of sedimentary units, was the main factor to explain the overall variations of the geomorphometric results. The developed regionalization process improved the potential of local geomorphometric data for updating and revision of geological maps and for guiding future surveys in the sedimentary domain of Amazônia.

Analysis of the relationships between the spatial arrangement of palaeovalleys and contemporary valleys of Central Poland in the light of GIS methods

The article presents an example of application of selected GIS methods for showing connections between the course of palaeovalleys and contemporary valleys in Central Poland. The analysed area was shaped in the conditions of environment as early as the Palaeogene and Neogene, but the greatest impact on the present-day landscape came from the morphogenetic processes which operated in the Quaternary.Palaeogeographic studies of the analysed area often point to the possible dependencies between the contemporary landscape and its substrate, particularly as regards the valley system. In order to verify this hypothesis, on the basis of archival cartographic materials and a Digital Elevation Model of the current terrain, a procedure for conducting analyses with the use of commonly available GIS tools was proposed. Results of the conducted analysis allow for stating that the major river valleys of Central Poland in large part correspond to the arrangement of the fossil valley system, and the relationships are most easily noticeable for the largest valleys.