Construction of a 1:250,000 scale regolith-landform map of the Cobar area of central New South Wales (NSW) Australia, demonstrates the presence of a wide range of previously undescribed regolith materials, landforms and landscape features in the region. The map covers the east-west extent of the Cobar Basin, extends to the west onto the Darling River Floodplain, and east onto rocks of the Girilambone Group. The mapping area is centred on the Cobar township and covers -14,730 krn2 between 303113 and 446113 E and 6483184 and 6586183 N (AGO 66, MGA Zone 55). 48 regolithlandform units have been identified, including both transported (alluvial, colluvial, aeolian, lacustrine) and in situ materials. A range of siliceous, ferruginous and calcareous indurated materials are also present. Four major drainage types have been identified based on lithological, sedimentological and topographic differences in alluvial materials. The 4 drainage types include: 1) modern drainage; 2) maghemite and quartzose gravels elevated 1-2 m relative to the modern drainage; 3) higher topographically inverted, and at least partly silicified, gravels; and, 4) sediments of Cretaceous origin. Multiple phases of drainage stability and instability from the Cretaceous to the present are indicated within the sediments. Breaching of drainage divides and increased dissection of the modern drainage, especially to the south of Cobar, indicate possible tectonic movement across a major regolith-landform boundary in the southern map area. Colluvial materials are more widespread to the north of Cobar reflecting the increased landscape dissection to the south. Colluvial fans are preserved adjacent to major rangefronts. Aeolian and lacustrine materials include longitudinal dunefields of the Darling River floodplain, source bordering dunes, and small lunettes associated with the Barnato Lakes system. Regolith-landform mapping at Cobar has been used to assess the applicability of previously developed landscape evolution models of the Cobar Block and surrounding region, and to develop a new landscape evolution model for the region. The new landscape evolution model of Cobar indicates minimal deposition of Cretaceous sediments, succeeded by high-energy early Tertiary fluvial regimes across the Cobar landscape. Weathering and sediment deposition continued into the Miocene, coupled with deep valley incision on the Cobar Block associated with early Oligocene regression. By the close of the Miocene, the Cobar Block had eroded to predominantly bedrock terrain and widespread filling of previously incised valleys occurred. A decrease in erosion and fluvial activity led to the formation of the modern drainage during the Pliocene-early Quaternary, followed by the formation of alluvial, aeolian and lacustrine deposits in the later Quaternary. Regionally, Eromanga Basin sediments were not extensive over the Cobar Block, and low rates of erosion are recorded at Cobar from the Cretaceous to the present. Former northerly drainage did exist in this area in the Cretaceous, but was limited in distribution. By at least the Early Tertiary the Cobar area was a structural high and drainage systems of the region had assumed their current configuration. These findings do not support interpretations of AFTT data of significant cover and subsequent stripping over the Cobar Block in the Early Tertiary. Evidence of landscape evolution from the Cretaceous to the present suggests that the Cobar landscape has been responding to changes in the primary landscape forming factors of lithology, climate and to a lesser degree, tectonics. Variations in the these three primary landscape forming factors have contributed to ongoing weathering, relatively continuous deposition, and periods of relative stability and instability, particularly in response to climatic and baselevel fluctuations, within a dynamically evolving landscape throughout the entire Tertiary. Former landscape evolution models of peneplanation and pediplanation, based on correlation of palaeosurfaces including duricrusts, a deep weathering profile developed during extended planation in the Early Tertiary, and tectonism during the late Tertiary in the Cobar area, are not supported by evidence preserved in regolith-landform features at Cobar.

Quantifying how hillslopes respond to river incision and climate change is fundamental to understanding the geomorphic evolution of tectonically uplifting landscapes during glacial-interglacial cycles. Hillslope adjustment in the form of deep-seated bedrock landslides can account for a large proportion of the regional sediment yield and denudation rates for rapidly uplifting landscapes. However, the timing and magnitude of the response of hillslopes to climatic and tectonic forcing in moderate uplift temperate maritime catchments characteristic of many active margins worldwide is not well quantified. This study seeks to investigate how hillslopes respond to climate-modulated river incision and to quantify the magnitude of the sediment flux from this response in a typical active margin setting. The non-glacialWaipaoa Sedimentary System (WSS) on the East Coast of the North Island of New Zealand consists of river catchments, coastal foothills to uplifting mountain ranges, and terrestrial and marine sediment depocentres collectively underlain by relatively young (Cretaceous and younger) sedimentary rocks within a tectonically active setting and temperate maritime climate. These attributes make theWSS similar to many coastal catchments on oceanic-continental convergent margins worldwide. However, because of widespread destruction of primary forests for conversion to pasture lands by the mid 20th Century, theWSS is currently a globally significant source of sediment to the world’s oceans. Because of these factors, theWSS was selected as one of two global study sites for the international, NSF supported, MARGINS Source-to-Sink initiative designed to investigate the transfer of sediment from terrestrial source to marine sink. Previous studies on theWSS have shown a strong link between climate change and geomorphic response in the system. River incision since the last glacial coldest period has generated a significant amount of topography, leaving small remnants of the ca.18,000 cal. yr BP last glacial aggradation terrace scattered up to 120 m above modern rivers. In this study, the hillslope response to river incision is quantitatively examined using new high resolution topographic data sets (lidar and photogrammetry) in combination with 3 field mapping and tephrochronology. Hillslopes are found to be coupled to river incision and adjusted to rapid incision through the initiation and reactivation of deep-seated landslides. In the erodible marine sedimentary rocks of the terrestrialWSS, post-incision deep-seated landslides can occupy over 30% of the surface area. Many of these slides show evidence of multiple “nested” failures and landslide reactivation. The ages of tephra cover beds identified by electron microprobe analysis show that following an initial 4,000 to 5,000 year time lag after the initiation of river incision, widespread hillslope adjustment started between the deposition of the ca. 13,600 cal. yr BPWaiohau tephra and the ca. 9,500 cal. yr BP Rotoma tephra. Tephrochronology and geomorphic mapping analysis indicates that river incision and deep-seated landslide slope adjustment is synchronous between mainstem rivers and headwater tributaries. Tephrochronology further shows that many slopes have continued to adjust to channel incision into the late Holocene. Hillslope response in the catchment can involve the entire hillslope from river to ridgeline, with some interfluves between incising sub-catchments being dramatically modified through ridgeline retreat and/or lowering. Using the results of the landform tephrochronology and geomorphic mapping, a conceptual time series of hillslope response to uplift and climate change-induced river incision is derived for a timeframe encompassing the last glacial-interglacial cycle. Using the same high resolution topography datasets, in-depth field analysis, and tephrochronology, the 18,000 year sediment yield from terrestrial deep-seated landslides in theWSS is estimated in order to investigate the magnitude of hillslope response to climate-modulated, uplift driven river incision. This completes one of the first processbased millennial time-scale sediment budgets for this class of temperate maritime, active margin catchments. Fluvial and geomorphic modelling is applied to reconstruct pre 18,000 cal. yr BP topography in 141 km2 of detailed study area and the resulting volumetric estimates from 207 landslides are used to estimate deep-seated landslide sediment flux for the broader system. An estimated 10.2 km3 of deep-seated landslidederived sediment with a multiplicative uncertainty of 1.9 km3 (+9.2 km3, -4.8 km3) was delivered to terrestrial and marine sinks. This accounts for between 10 and 74% of the total mass of the terrestrialWSS budget of ca. 91,000 Mt (+37,000 Mt, -26,000 Mt). Combining the deep-seated landslide results with other studies of terrestrial sediment sources and terrestrial and shelf sinks, the estimated terrestrial source load ranges from 4 Abstract 1.2 to 3.7 times larger than the mass of sediment sequestered in terrestrial and shelf depocentres. This implies that off-shelf transport of sediment is important in this system over the last 18,000 cal. yr BP, as it is today for anthropogenic reasons. Based on the derived sediment budget, the denudation rate for the terrestrialWSS of 0.8 mm yr-1 (+0.3 mm yr-1, -0.2 mm yr-1) is indistinguishable from the average terrestrialWaipaoa late Quaternary uplift rate, indicating an approximate steady-state balance between denudation and uplift. This thesis provides a quantitative analysis of the role of deepseated landslides in an active margin catchment that is used to improve the understanding of landscape and terrestrial source-to-marine-sink sediment transfer dynamics.

Südostbrasilien war während des Spätpleistozäns und des Holozäns beachtlichen Klimaschwankungen unterworfen, die vielfältige geoökologische Konsequenzen zur Folge hatten. Mit der europäischen Kolonialisierung setzte überdies ab dem frühen 16. Jahrhundert eine anthropogen verursachte Degradation ein, welche zu massiven Veränderungen des Landschaftssystems führte. Trotz einer längeren geowissenschaftlichen Forschungstradition in der Region ist der Kenntnisstand über die Auswirkungen der natürlichen und anthropogenen Veränderungen auf die Geomorphodynamik bis heute vergleichsweise gering. Bereits existierende Vorstellungen zu dieser Thematik erscheinen darüber hinaus zumindest ergänzungswürdig und müssen entsprechend des aktuellen Forschungsstandes erweitert werden. Um einen Beitrag zur Schließung dieser Forschungslücken zu leisten, wurden im Rahmen der hier vorliegenden Arbeit bodengeographische und fluvialmorphologische Untersuchungen im südostbrasilianischen Guapi-Macacu Flusseinzugsgebiet durchgeführt. Im konkreten soll der Frage nachgegangen werden, ob und wie sich klimatische und anthropogene Veränderungen auf die geomorphodynamische Stabilität der Region ausgewirkt haben. Neben dem wissenschaftlichen Erkenntnisgewinn können daraus gesellschaftlich relevante Informationen über zukünftige Umweltveränderungen abgeleitet werden. Zur Beantwortung solcher Fragestellungen werden in den Geowissenschaften Paläoumweltarchive genutzt. Wegen seiner naturräumlichen Gegebenheiten kommen in der Region dabei lediglich Böden oder fluviale Sedimente als Geoarchive in Frage. Folglich widmet sich der erste Teil der vorliegenden Dissertation der Bodenverbreitung und -genese im Vorland der Serra dos Órgãos-Gebirgskette. Neben der feldmethodischen Aufnahme ausgewählter Bodenprofile wurde dafür auch auf klassische physikochemische Labormethoden zurückgegriffen. Die sich daraus ergebenden bodengeographischen Befunde lassen große Übereinstimmungen mit bekannten Arbeiten aus anderen tropischen Regionen der Welt erkennen. So ist der erdoberflächennahe Untergrund an erosionsgeschützten Standorten aus stark verwitterten, (gelb)braunen Böden oder Bodensedimenten aufgebaut, welche fossile rote Bodenhorizonte und/oder einen farblich heterogenen Kristallinzersatz überlagern. An vielen Unterhängen konnten darüber hinaus teils mehrgliedrige, junge Kolluvien beschrieben werden. Um geomorphodynamische Aktivitätsperioden ausweisen zu können war v.a. die zeitliche Stellung der Hangverlagerungsprozesse von Bedeutung. Feo/Fed- und Mno/Mnd-Verhältnisse sowie geomorphologische Feldbefunde erlauben zusammen die Unterscheidung zwischen älteren und jüngeren Hangsedimenten. Die jüngsten Unterhangkolluvien konnten aufgrund eingebetteter moderner Keramik und Holzkohlen sicher in die neuzeitliche Landnutzungsperiode gestellt werden. Insgesamt ist das Archivpotenzial der Böden und Bodensedimente im Untersuchungs-gebiet jedoch gering. Die formulierten Forschungsfragen zu den Folgen von klimatischen und anthropogenen Veränderungen auf die Geomorphodynamik können damit nur unzureichend beantwortet werden. Einen Fortschritt könnten zukünftig evtl. Lumineszenzdatierungen bringen. Im zweiten Teil der Arbeit werden Untersuchungen vorgestellt, die an fluvialen Sedimentsequenzen in der Region durchgeführt wurden. Diese sind über weite Strecken aufgeschlossen und können daher vergleichsweise einfach studiert werden. Arbeiten zum Aufbau fluvialer Sedimente und Ableitungen über Paläoumweltbedingungen sind in Süd- und Südostbrasilien bisher äußerst selten und darüber hinaus ist die chronologische Auflösung meist nur unzureichend. In der vorliegenden Dissertation wurde zunächst aus 13 chronostratigraphisch bearbeiteten Einzelprofilen ein spätpleistozänes und holozänes, fluviales Standardprofil für das Guapi-Macacu Einzugsgebiet abgeleitet, welches sich aus vier deutlich zu unterscheidenden Fazieseinheiten aufbaut. 44 14C-Datierungen liefern hierfür ein solides Zeitgerüst, so dass gesicherte Aussagen über das Verhalten des Guapi-Macacu-Systems während der letzten etwa 13.000 Jahre möglich sind. Zwar stellt auch das fluviale Standardprofil kein hochauflösendes Paläoumweltarchiv dar, jedoch kann daraus ein wissenschaftlich wertvoller Erkenntnisfortschritt über die Geomorphodynamik im Untersuchungsgebiet abgeleitet werden. So weisen die Ergebnisse auf mehrfache Wechsel in der Fluvial- und Hangdynamik hin, die mit sehr hoher Wahrscheinlichkeit durch großklimatische Veränderungen hervorgerufen wurden. Störungen der thermohalinen Nordatlantikzirkulation lösten an der Grenze zwischen Pleistozän und Holozän sowie am Übergang vom Mittel- zum Spätholozän eine Südwärtsverlagerung der innertropischen Konvergenzzone (ITCZ) aus, wodurch sich die Südatlantische Konvergenzzone (SACZ) während der Sommermonate mit dem Südamerikanischen Monsunsystem (SAMS) verbinden konnte. Im Untersuchungsgebiet wurden dadurch feuchtere Bedingungen und gehäuft Starkregen ausgelöst, welche zu geomorphodynamisch aktiven Phasen führten. Vor allem in steilen Hanglagen und unterhalb größerer abflusswirksamer Felsflächen fanden phasenweise erhebliche Bodenabträge statt und ältere Hillwashsedimente wurden an den Unterhängen akkumuliert. In den Talböden sind die natürlichen Instabilitätsphasen durch grobklastische Schotter (Fazieseinheit I, ca. 12.800 cal. BP) sowie mächtige sandig bis kiesige Sedimente (Fazieseinheit III, ab ca. 4.700 cal. BP) dokumentiert. Bei einer vergleichsweise nördlichen Position der ITCZ, während des Früh- und Mittelholozäns, herrschten im Untersuchungsgebiet hingegen trockenere Klimabedingungen, welche zu geomorphodynamischer Stabilität führten. Diese Stabilitätsphase ist durch einen Hiatus bzw. feinkörnige fluviale Ablagerungen (Fazieseinheit II,zwischen 6.600 und 4.300 cal. BP) in den Flusstälern belegt. An den Hängen wurden zeitgleich sehr wahrscheinlich Cambisole gebildet. Mit der europäischen Kolonisation setzte zu Beginn des 16. Jahrhundert in Südostbrasilien die sukzessive Zerstörung des Atlantischen Küstenregenwaldes ein. Zuckerrohr- und Kaffeeplantagen etablierten sich und es wurde großflächig Brandrodungsfeldbau praktiziert. Dadurch wurden die Böden zeitweise entblößt, was in Verbindung mit den ergiebigen Niederschlägen erneut verstärkte Abträge zur Folge hatte. Die korrelaten Sedimente der nutzungsinduzierten Bodenerosion sind in Form von holzkohlehaltigen Unterhangkolluvien und Auenlehmen (Fazieseinheit IV) erhalten geblieben. Die 14C-Datierungen aus den Flusssedimenten belegen einen verstärkten anthropogenen Einfluss in der Region seit maximal 250 Jahren. Die vorliegende Arbeit hat gezeigt, dass Klima- und Nutzungsbedingungen das geomorphodynamische Prozessgeschehen in der Vergangenheit steuerten. Für die Zukunft sind eine Häufung von Starkniederschlägen und ein wachsender Nutzungsdruck in der Region prognostiziert. Die Ergebnisse aus der jüngeren Erdgeschichte lassen vermuten, dass es dadurch zur Landschaftsdestabilisierung verbunden mit großflächigen Hangrutschungen kommen wird. Diese werden v.a. in besiedelten Regionen sehr ernstzunehmende Naturgefahren für die Bevölkerung darstellen. / A growing number of publications from southeastern Brazil points to significant climatic and subsequently substantial geo-ecological changes during the latest Pleistocene and Holocene. Additionally, the European colonization led to anthropogenically triggered landscape degradation since the early 16th century. Even though there has been a long-term geoscientific research tradition in that region, the impacts of these changes on geomorphodynamic processes are not well understood so far. Existing concepts dealing with these topics need to be improved according to the current state of research. Hence, this doctoral thesis attempts to partly close this gap of knowledge. Therefore, pedological and sedimentological investigations were carried out at several outcrops within the Guapi-Macau river basin, SE-Brazil. Especially, this work aims to answer the research question if and how climate changes and increased human impact affected geomorphodynamic stability of this region. In addition to its scientific importance, this topic is of high relevance for the prediction of future environmental changes as well. Geoarchives are used in geosciences for the reconstruction of Quaternary palaeoenvironments. Due to local geographic conditions, only soils and fluvial sediments can be used as palaeoenvironmental archives in the study area. Consequently, the first part of this thesis deals with soil distribution and soil development in the foreland of the Serra dos Órgãos Mountains. Standard field descriptions and physicochemical laboratory methods were applied to characterize the regional soils. The results show that these soils have great similarities with other tropical regions of the world. In the study area a standard soil profile contains of a strongly weathered, (yellowish)brown soil horizon or hillwash sediment, covering a fossil reddish soil horizon and/or a heterogeneous weathering mantel. Additionally, relatively young colluvial soils can be observed in many footslope positions. To identify phases of geomorphic activity, the temporal evolution of hillslope deposition is of great importance. A combination of Feo/Fed- and Mno/Mnd-ratios as well as the assessment of the geomorphic position of the sites allowed a relative distinction of older from younger hillslope deposits in the region. In detail, whereas youngest colluvial layers developed during the modern period of land use intensification, could be identified by embedded modern pottery as well as high amounts of charcoal, a further distinction of older hillslope deposits was not possible with the applied methods. Furthermore, often their preservation state is not sufficient so that their potential as archives for palaeoenvironmental research is very limited. However, future luminescence dating would be an option to establish a late Quaternary chronology of hillslope deposits. In the second part of this thesis, investigations of fluvial sediments of the region will be presented. They are exposed over longer distances of the river courses in the Guapi-Macau catchment so that they could easily be studied. Comparable works on the architecture of fluvial sediments are very rare in SE-Brazil, and furthermore their palaeoenvironmental interpretation often remains doubtful due to insufficient age control. Based on chronostratigraphical investigations of 13 fluvial exposures a latest Pleistocene and Holocene standard profile for the Guapi-Macau catchment were developed. The investigations revealed four different facies units that are clearly distinguishable from each other. 44 14C-datings provide a reliable time frame for the reconstruction of the Guapi-Macacu river system during the last approx. 13.000 cal. years BP. Although the fluvial sediments are discontinuous and thus do not offer high resolution proxy data, important findings concerning geomorphodynamic processes could be extracted from them. The results point on multiple changes of the overall geomorphodynamic conditions, very likely triggered by large-scale climate changes. Disturbances in the thermohaline circulation of the northern Atlantic caused a southwards shift of the Intertropical Convergence Zone (ITCZ) at the Pleistocene/Holocene boundary as well as at the transition from the Mid- to the Late Holocene. Consequently, the South Atlantic Convergence Zone (SACZ) was connected with the South American Monsoon System (SAMS) during summer, producing periods of intense precipitation over large parts of southeastern South America where the study area is located. Especially at steep slopes and below larger areas of bare bedrock phases of geomorphic activity periodically appeared. Significant amount of soil were eroded, and older hillwash sediments were deposited on the footslopes. In the floodplains, coarse grained gravels (Unit I, approx. 12.800 cal. BP) and several meters of planar or cross-bedded sands to fine gravels (Unit III, after approx. 4.700 cal. BP) document periods of natural geomorphodynamic instability. Due to a more northerly position of the ITCZ, the study area was obviously drier and geomorphologically more stable during the Early and Mid-Holocene. This is documented by a hiatus or fine-grained deposits (Unit II, from approx. 6.600 to 4.300 cal. BP), respectively. On the slopes probably (yellowish)brown cambisols developed simultaneously. Since the European colonization starting from the early 16th century large areas of valuable Atlantic rainforest were destroyed. Instead, sugar cane and coffee plantations were established, and slash-and-burn agriculture became a common land use practice. Soils were exposed and prevailing strong rains led to high rates of soil erosion again. Correlate sediments of this man-made soil erosion are preserved as charcoal-containing hillslope colluvium and fine-grained floodplain sediments (Unit IV). Radiocarbon ages from the fluvial loams point on increased human impact for the last max. 250 years. The present doctoral thesis demonstrates that climatic changes and human impact strongly affected geomorphodynamic processes of SE-Brazil during the past. There are predictions of a larger frequency of intense rainfall events and increased land use pressure for the future. The presented results from the geological history suggest that landscape destabilization and large-scale landslides could be direct consequences of such changes. As seen already today, especially in highly populated regions this could be serious natural hazards which can affect human health.

xvi, 136 p. : ill. (some col.) A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number. / This dissertation discusses the contribution of deep-seated landslides and earthflows to the morphology, erosion, and evolution of mountainous landscapes, focusing on the northern California Coast Ranges. In active landscapes, channel incision is necessary to create relief but also increases stresses in adjacent hillslopes, ultimately leading to slope failure. While conceptually simple, the spatial relationships between channel incision and landsliding have not been well quantified. Along the South Fork Eel River, I mapped the distribution of deep-seated landslides using light detection and ranging (LiDAR) derived maps. Landslide density increases in regions subject to late Pleistocene-Holocene channel incision and particularly in response to lateral incision at the apex of meander bends. Wavelet analysis of channel sinuosity reveals hillslopes are most sensitive to meander wavelengths of 1.5 km. Argillaceous lithology generates abundant earthflow activity along the main stem Eel River, yet spatial and temporal patterns of earthflow movement are poorly understood. I undertook a detailed study of the Kekawaka Earthflow using LiDAR, meteoric 10 Be in soil, orthorectified historical aerial photographs, and field surveys. Inventories of 10 Be in soil pits increase systematically downslope, indicate an average movement rate of 2.1 ± 1.3 m/a over the past 150 years, and establish a minimum earthflow age of 1700 years. The Kekawaka earthflow has a systematic history of movement, both spatially, with greatest movement in the narrow transport zone, and temporally, as velocities peaked in the 1960's and have slowed since 1981. I used LiDAR and aerial photographs to map earthflow movement and calculate sediment flux across 226 km 2 of the main stem Eel River. From 1944-2006, 7.3% of the study area was active, and earthflows account for an erosion rate of 0.53 ± 0.04 mm/a, over half the regional average sediment yield. Velocity time series on 17 earthflows suggest temporal earthflow behavior is influenced by decadal-scale changes in precipitation, temperature, and river discharge, although local topographic factors can overwhelm this climatic signal. When active, earthflows erode an order of magnitude faster than surrounding terrain; however, source supply limitations appear to govern long- term earthflow evolution. This dissertation includes previously published coauthored material. / Committee in charge: Joshua Roering, Chairperson, Geological Sciences; Ilya Bindeman, Member, Geological Sciences; Dean Livelybrooks, Member, Physics; Ray Weldon, Member, Geological Sciences; W. Andrew Marcus, Outside Member, Geography

Made available in DSpace on 2015-04-22T21:58:40Z (GMT). No. of bitstreams: 1 DISSERTACAO FRANCINELE.pdf: 3255436 bytes, checksum: 43f68fe86d2c26a8d069ecd0eb9bc428 (MD5) Previous issue date: 2011-06-29 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The lateritic crusts, which represent the relict of paleoclimatic changes especially between the Cenozoic and the Recent, allow inferring the conditions and the evolution of weathering in the intertropical region of the Earth. At the edge of the Guianas Shield, in the central region of Roraima, where occur lateritic crusts outcropping, has developed the Graben of the Tacutu. It`s reactivation in the Pliocene caused severe erosion what the region tectonically unstable. With the objective to determine the implications of that environment in the weathering of the basement rocks from the Guiana Shield, the region of Mucajai was selected to where it is situated the Serra da Prata and to a less extent the Serra da Moça. These relief features are inserted in the Piedmont Rio Branco-Rio Negro, and its surroundings lowered portion on the Dissected Plateau North of the Amazonas. Rocks, crusts and soils of the region were studied on basis of field survey of the lithotypes and their textural, mineralogical and geochemical characterization. The major oxides, the trace elements (Mn, Zr, V, Ni, Cu, Zn, Sc, Co, Ga, Cr, Y, Th, Hf, Nb, Ta, Ba, Mo, Sr, Rb, Cs, U, W, As, Au, Ag, Hg, Ge, In, Li, Sb, Se, Te, Tl and ETR) and the Pb isotopes were analyzed. The lateritic lithotypes developed from charnockites, gabbro, granites and gneisses. Crusts of protopisoliticas and pisoliticas types were formed at the top of the Serra da Prata and vermiform in the lower portions of the landscape which are cover by clay-sandy reddish brown soils. The crusts are immature, friables with abundant clay matrix, composed mainly of goethite and hematite, and low content of gibbsite. The rocks are distinguished by SiO2, Na2O, K2O, Ba, Rb, Tl, Y, Mo, REE (La-and Eu) association, while the lateritic rocks by Fe2O3, PF, Co, Cr, Ga, Zn, Mn, W . There is a greater geochemical affinity between the crusts and soils with granite, charnockite and gneiss than with the gabbro, as they are the most abundant rocks and also because they have little chemical variation; however, the Pb isotopic ratios indicate provenance from the charnockite. The development of these crusts marks the Quaternary landscape evolution of the central portion of Roraima after the tectonic reactivation in the Miocene. / As crostas lateríticas, que representam os relictos das transformações paleoclimáticas especialmente entre o Cenozóico e o Recente, permitem inferir as condições e a evolução do intemperismo na região intertropical da Terra. Na borda do Cráton das Guianas, região central de Roraima, se desenvolveu o Grabén do Tacutu, onde afloram crostas lateríticas. Essa área cratônica foi reativada no Plioceno o que propiciou intensa erosão ao tornar a região tectonicamente instável. Com o objetivo de determinar as implicações desse ambiente no intemperismo das rochas do embasamento do Cráton das Guianas, foi selecionada a região de Mucajaí onde ocorrem a Serra da Prata e com menor expressão a Serra da Moça. Essas feições de relevo fazem parte do Pediplano Rio Branco-Rio Negro, e seu entorno rebaixado, do Planalto Dissecado Norte da Amazônia. Foram estudadas as rochas, as crostas e os solos da região com base em levantamento de campo dos litotipos e na caracterização dos aspectos texturais, mineralógicos e geoquímicos. Foram analisados os óxidos maiores e menores (SiO2, Fe2O3, Al2O3, K2O, Na2O, CaO, MgO,TiO2, P2O5, PF) os elementos traços (Mn, Zr, V, Ni, Cu, Zn, Sc, Co, Ga, Cr, Y, Th, Hf, Nb, Ta, Ba, Mo, Sr, Rb, Cs, U, W, As, Au, Ag, Hg, Ge, In, Li, Sb, Se, Te, Tl e ETR) e isótopos de Pb. As crostas lateríticas desenvolveram-se a partir de charnockítos, gabros, granitos e gnaisses. São do tipo protopisolíticas a pisolíticas no topo da Serra da Prata e vermiformes nas porções rebaixadas, ambas recobertas por solos argiloarenosos marrom avermelhados. As crostas lateríticas são friáveis com abundante matriz argilosa, com predominância de goethita sobre hematita, e baixo conteúdo de gibbsita, portanto são pouco evoluídas, destacando-se apenas por seus conteúdos de Fe2O3, PF, Co, Cr, Ga, Zn, Mn e W, enquanto as rochas se diferenciam pela associação SiO2, Na2O, K2O, Ba, Rb, Tl, Y, Mo, ETR (-La e Eu). Apesar das razões isotópicas de Pb indicarem que as crostas lateríticas tiveram proveniência a partir do charnoquito, os dados geoquímicos mostraram maior afinidade entre essas e as rochas mais abundantes (granito, charnoquito e gnaisse), devido suas similaridades químicas. O desenvolvimento destas crostas marca a evolução quaternária da paisagem após a reativação tectônica da região no Mioceno.

[pt] A ocupação e uso dos solos têm claras implicações nos processos erosivos, porém devemos destacar também um dos atores principais para os processos erosivos, que é a evolução geomorfológica. A bacia do córrego das Palmeiras está inserida em um local com baixas amplitudes de relevo, mas que apresenta um alto potencial de vulnerabilidade a eventos de erosão e movimentos de massa. Destacamos obviamente o grande número de voçorocamentos que atingem determinadas áreas do médio vale do rio Paraíba do Sul, principalmente próximos ao seu eixo principal em um grande alinhamento de direção NE-SW a qual a bacia do córrego das Palmeiras está inserida. O presente estudo tem como objetivo principal descrever a origem e a distribuição dos processos erosivos na bacia do córrego das Palmeiras, na cidade de Barra do Piraí, Rio de Janeiro. Para que o principal objetivo desse trabalho seja alcançado, se torna necessário o cumprimento dos objetivos específicos, os quais são: Descrever a relação da orientação das voçorocas com as estruturas do substrato geológico; Descrever a relação entre processos erosivos e os níveis de base locais e; Descrever a relação entre processos erosivos e uso do solo. Para a realização deste trabalho foram utilizadas técnicas de análise e embasamentos teóricos da ciência geográfica e mais especificamente da área da geomorfologia. Podemos destacar como os principais resultados alcançados as análises referentes à relação entre os condicionantes geológicos/geomorfológicos e a ocorrência e comportamento de processos erosivos, permitindo afirmar que existe uma relação estreita entre a compartimentação geológica, orientação das estruturas, processos de rebaixamento de níveis de base, histórico de uso e ocupação do solo e a presença de processos erosivos. / [en] Land use has clear implications in the erosive processes and their relation with the geomorphological evolution can be seen notoriously. The Palmeiras stream basin is inserted in a place with low amplitudes of relief, but that presents a high potential of vulnerability to events of erosion and mass movements. We highlight obviously the large number of gully erosions that reach certain areas of the middle valley of the Paraíba do Sul river, mainly near its main axis in a great alignment of direction NE-SW to which the basin of the stream of Palmeiras is inserted. This study has as main objective the description of the origin and spatial distribution of the erosive processes in the Córrego dos Palmares basin. In order for the main objective of this work to be achieved, it is necessary to fulfill the specific objectives, which are: Analyze the spatial distribution of erosive processes; analyze the relation of the orientation of the gullies with the lithological structures of the geological substrate; Analyze the relationship between erosive processes and local base levels and; analyze the relationship between erosive processes and land use. For the accomplishment of this work, techniques of analysis and theoretical bases of the geographic science and more specifically of the area of geomorphology were used. We can highlight as the main results of the description the relationship between the geological / geomorphological conditions and the occurrence and behavior of erosive processes, allowing to affirm that there is a close relationship between the geological compartmentation, orientation of the structures. History of land use and occupation and the presence of erosive processes.

>Magister Scientiae - MSc / Several attempts have been made to assess the impact of post-fire soil erosion; however, erosion occurs as a result of the complex interplay between many factors, such as climate, land cover, soil and topography, making precise estimation difficult. Additionally, these factors are far from constant in space and time, and often interact with one another. To assess the impact of wildfire on soil erosion and factors influencing its variability, the post-fire soil erosion response of two mountainous headwater sub-catchments namely Langrivier and Tierkloof, with different vegetation cover in the Jonkershoek Valley was examined using a systematic approach that combines efforts in field and laboratory work, spatial analysis and process-based numerical modelling. Geospatial modelling shows high spatial variability in erosion risk, with 56 % to 67 % of surfaces being highly susceptible excluding rock cover. The model highlights the importance of terrain and vegetation indices, with predicted erosion being more severe on steep slopes with lower vegetation cover. / 2021-08-30

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第18083号 / 理博第3961号 / 新制||理||1571(附属図書館) / 30941 / 京都大学大学院理学研究科地球惑星科学専攻 / (主査)教授 千木良 雅弘, 教授 釜井 俊孝, 准教授 松四 雄騎 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

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