The primary goal of this project is to develop a relative chronology of events in the geologic history of the Kentucky River, and to consider the geologic controls on those events. This study utilized published geologic and topographic data, as well as field observations and extensive compilation and comparison of digital data, to examine the fluvial record preserved in the Kentucky River valley in central Kentucky. Numerous fluvial features including abandoned paleovalleys, fluvial terraces and deposits, bedrock benches, and relict spillways between adjacent river valleys were identified during the course of the study. The morphology of the modern valley coincides with bedrock lithology and can be used to describe the distribution and preservation of modern and ancient fluvial deposits and features in the study area. Bedrock lithology is the dominant control on valley morphology and on the distribution and preservation of fluvial deposits and features in the study area. Some stream trends are inherited from the late Paleozoic drainage of the Alleghanian orogeny. More recent inheritance of valley morphology has resulted from the erosion of the river from one lithology down into another lithology with differing erosional susceptibility, thus superposing the meander patterns of the overlying valley style onto the underlying lithology. One major drainage reorganization related to a pre-Illinoisan glacial advance disrupted the northward flow of the Old Kentucky River toward the Teays River system and led to organization of the early Ohio River. This greatly reduced the distance to baselevel, and led to abrupt incision and a change in erosional style for the Kentucky River. The successful projection of valley morphologies on the basis of bedrock stratigraphy, the history of erosion suggested by fission track data and the results of this study, as well as soil thickness and development, all argue against the existence of a midto late-Tertiary, low-relief, regional erosional surface. This study instead hypothesizes that the apparent accordance of ridge-top elevations in the study area is a reflection of a fluvially downwasted late Paleozoic depositional surface.

Geography and the Environment / Studies of the Amazon drainage network have primarily focused on the Western Basin and the Amazon Cone, but they have neglected the integration between these areas. Data presents a time gap in the Amazon’s development and the forces responsible for the organization of the drainage network are poorly understood. A key element towards gaining an improved awareness of the Amazon is the Eastern Amazon River Valley. The focus of this study is an 80,000 km² portion of this area. An integrated method is adopted that combines terrain information derived from a digital elevation model with geologic data. The interpretation of DEM data is unique to this study. Seven distinct surfaces were identified, along with numerous erosional environments. This observation supports a geomorphologic record of numerous erosional events starting in the Miocene. This finding is significant as it rejects previous models for staircase-like terraces for the Amazon, and establishes a timeline for the development of geomorphologic landforms in the study area. In addition, neotectonics events provide an alternative explanation to the generation of topography in the study area. It was concluded that geomorphology in the study area is the result of physical and chemical weathering, and modified by neotectonics. These findings provide alternative means for Amazon landscape evolution. / text

Upland rivers control the large-scale topographic form of mountain belts, allow coupling of climate and tectonics at the earth’s surface and are responsible for large scale redistribution of sediment from source areas to sinks. However, the details of how these rivers behave when perturbed by changes to their boundary conditions are not well understood. I have used a combination of fieldwork, remotely sensed data, mathematical analysis and computer modelling to investigate the response of channels to well constrained changes in the forcings upon them, focussing in particular on the effects of glacial remoulding of the catchments draining the south flank of the Ladakh batholith, northwest Indian Himalaya. The last glacial maximum for these catchments is atypically old (~100 ka), and this allows investigation of the response to glaciation on a timescale not usually available. The geomorphology of the catchments is divided into three distinct domains on the basis of the behaviour of the trunk stream – an upper domain where the channel neither aggrades above or incises into the valley form previously carved by glacial abrasion, a middle domain where the channel incises a gorge down into glacial sediments which mantle the valley floor, and a lower domain where the channel aggrades above this postglacial sediment surface. This landscape provides a framework in which to analyze the processes and timescales of fluvial response to glacial modification. The dimensions of the gorge and the known dates of glacial retreat record a time averaged peak river incision rate of approximately 0.5 mm/y; the timescale for the river long profile to recover to a smooth, concave up form must exceed 1 Ma. These values are comparable with those from similarly sized catchments that have been transiently perturbed by changing tectonics, but have never been quoted for a glacially forced basin-scale response. I have also demonstrated that lowering of the upper reaches of the Ladakh channel long profiles by glacial processes can systematically and nonlinearly perturb the slope-area (concavity) scaling of the channel downstream of the resulting profile convexities, or knickzones. The concavity values are elevated significantly above the expected equilibrium values of 0.3-0.6, with the magnitude controlled by the relative position of the knickzone within the catchment, and thus also by the degree of glacial modification of the fluvial system. This work also documents the existence of very similar trends in measured concavities downstream of long profile convexities in other transiently responding river systems in different tectonoclimatic settings, including those responding to changes in relative channel uplift. This previously unrecognised unity of response across a wide variety of different environments argues that such a trend is an intrinsic property of river response to perturbation. Importantly, it is consistent with the scaling expected from variation in incision efficiency driven by evolving sediment flux downstream of knickzones. The pervasive nature of this altered scaling, and its implications for fluvial erosion laws in perturbed settings, have significant consequences for efforts to interpret past changes in forcings acting on river systems from modern topography. I follow this by examining in detail the channel hydraulics of the Ladakh streams as they incise in response to the glacial perturbation. I present a new framework under which the style of erosion of a natural channel can be characterized as either detachment- or transport-limited based upon comparison of the downstream distribution of shear stress with the resulting magnitude of incision. This framework also allows assessment of the importance of sediment flux driven effects in studied channels. This approach is then used to demonstrate that fluvial erosion and deposition in the Ladakh catchments is best modelled as a sediment flux dependent, thresholded, detachment-limited system. The exceptional quality of the incision record in this landscape enables an unprecedented calibration of the sediment flux function within this incision law for three different trunk streams. The resulting curves are not compatible with the theoretically-derived parabolic form of this relation, instead showing nonzero erosion rates at zero sediment flux, a rapid rise and peak at relative sediment fluxes of less than 0.5 and a quasi exponential decrease in erosional efficiency beyond this. The position of the erosional efficiency peak in relative sediment flux space and the magnitude of the curve are shown to be both variable between the catchments explored and also correlated with absolute sediment flux in the streams.

River incision into a widespread, upland low-relief landscape, and related patterns of exhumation recorded by low-temperature thermochronology, together underpin geodynamic interpretations for crustal thickening and uplift of the eastern Tibetan Plateau. We report results from a suite of 11 (U-Th-Sm)/He cooling-age samples. Eight samples comprise a 1.2 km relief section collected from elevations up to 4800 m in the Jiulong Shan, an elevated, rugged region located in the hinterland of the Yalong-Longmen Shan Thrust Belt, and surrounded on three sides by upland low-relief landscape surfaces. Zircon and apatite cooling ages record two episodes of rapid exhumation in the early Oligocene and late Miocene, that were separated by a period of stability from similar to 30 to 15 Ma. The first episode is consistent with a similar pulse evident from the Longmen Shan. The second episode is ongoing, and when integrated with adjacent cooling-age data sets, shows that doming of the Jiulong Shan has resulted in 2 to 4 km of differential exhumation of the plateau interior. We show from a compilation of glacial landform-mapping that the elevation of the plateau surface closely tracks global last glacial maximum equilibrium line altitude. We hypothesize that smoothing of highlands by efficient glacial and periglacial erosion, coupled with potential river captures and conveyance of sediments via external drainage, can yield an apparently continuous low-relief plateau landscape formed diachronously at high elevation. (C) 2016 Elsevier B.V. All rights reserved.

Long-term perspectives on the evolution of river deltas have provided useful knowledge capable of responding to pending questions related to the ongoing climate and environmental changes. Increasing utilization pressure on delta environments has necessitated increased attention to protect the socio-economic and ecological values. As a result, multiple local initiatives have been designed, aimed at mitigating environmental deterioration and implementing adaptive measures, but many such initiatives have shown limited success. This thesis uses a case study of Save River delta in Mozambique to explore the relation between geomorphological evolution and socio-ecological system dynamics in delta environments. In addition, key environmental variables that concern the society today are highlighted and discussed in a management perspective. The results of the study show the development of Save River delta from the mid-Holocene to the present. The geomorphological settings of the delta suggest a faulted coastline over which subsequent deposition of fluvial sediments has formed a protruding delta front. Between c. 3000 and 1300 years ago, fine-grained sediments accumulated on top of the delta-front in the proximal part of the delta. This type of material was deposited under intertidal conditions and supported the formation of mangrove habitat. The geographical distribution of the mangrove deposit was driven by successive stages of back-barrier swamp formation and sea-level change as the delta evolved. From c. 1300 years ago, the river delta started to receive fluvial sediments from pulses of floods forming an alluvial floodplain. These sediments have accumulated mainly on the fine-grained mangrove wetland deposit. All the geomorphological features have evolved in a shoreward-shifting pattern over time. Centennial to decadal changes observed in the delta have followed a predictable geomorphological pattern, which is also part of the millennial evolution. The mangrove system, the base for the socio-economic system, is consequently strongly affected by the geomorphological development of the area. An increasing sensitivity of socio-ecological systems to environmental stressors, e.g. floods, cyclones and erosion, has motivated multiple initiatives to work towards a sustainable management of delta environments. This thesis highlights the need for interplay between geomorphology and ecology, considering both long- and short-term dynamics of delta environments. Hitherto, management initiatives have been concentrated on fragmented interventions of controlling water flow, which have disrupted the natural dynamics by obstructing the sedimentation-erosion cycle. To change this trend, coastal planners need to consider the significance of natural processes, e.g. cyclones, floods, erosion and accretion, for the long-term ecological and social sustainability of delta environments. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 1: Manuscript. Paper 2. Manuscript. Paper 3: Manuscript. Paper 4: Manuscript.</p>

In this dissertation, we have examined mineral assemblages and geomorphologic features in the Sisyphi Planum region of Mars, as well as examined the mineral assemblage of palagonite in Iceland. Chapter 2 is focused on the mineral assemblages detected on possible glaciovolcanic edifices in the Sisyphi Planum region of Mars. Minerals were identified utilizing visible/near-infrared orbital spectra from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM). Analysis of eleven CRISM images located on the volcanic edifices revealed three distinct spectral classes in the region which are interpreted to be: gypsum-dominated, smectite-zeolite- iron oxide-dominated (possibly palagonite), and polyhydrated sulfate-dominated material. The possible palagonite detections on the volcanic edifices, the geomorphology of the region, and the analogous terrestrial mineralogy of subglacial eruptions strongly suggests the formation of these minerals during subglacial eruptions or associated hydrothermal systems. This implies that thick water ice sheets were present in this region in the late Noachian or early Hesperian, and that the subglacial hydrothermal systems could have supported habitable environments with excellent biosignature preservation potential. Chapter 3 is focused on evaluating the variability of the composition and crystallinity of palagonite on Earth in order to inform efforts to identify it on Mars. We hypothesized that variability in palagonite composition and crystallinity could occur due to differences in environmental conditions during formation. Palagonite samples were collected in Iceland at subglacial volcanic sites around Reykjavík in the Western Volcanic Zone, on the southern coast in the Eastern Volcanic Zone, and from the Herðubreið tuya and Askja volcano in the Northern Volcanic Zone. Visible/near-infrared reflectance spectroscopy, thermal-infrared emission spectroscopy, and quantitative XRD were used to assess the bulk mineralogy, crystallinity, and clay composition of all samples. Results show the sampled palagonites contain partially devitrified glass, unaltered glass, and secondary minerals including clay minerals, poorly crystalline ferric oxides, and zeolites. However, one sample (SCoast01) shows a vastly different mineral assemblage in all sample techniques, including well-crystalline Fe/Mg-clays as opposed to the poorly-crystalline Al-clays observed in our other samples. Based on previous studies of subaqueous palagonites and the location this sample was collected from, we hypothesize that the SCoast01 sample was formed in a submarine environment rather than subglacial. This suggests that it may be possible to differentiate submarine vs. subglacial palagonite on Earth based on composition and from remote sensing observations on Mars. Chapter 4 is a geomorphologic study of the Sisyphi Planum region of Mars where we identified and classified the tops of the Sisyphi Montes as well as geomorphologically mapped the Sisyphi Planum region. Here, we address an overarching question: What is the relationship between the Sisyphi Montes and the ice in this region? To do this, we identified 106 edifices in the region and classified them into five categories: 1) flat topped, 2) rounded tops, 3) sharp peaks, 4) cratered peaks, and 5) height less than 300 meters – a “catch-all” category for all features below the specified height, which exhibit less distinctive morphologies in MOLA topography. While many of the edifices could be sub-glacial in origin, we find that the only morphologic class that exhibits uniquely subglacial morphologies are the flat-topped edifices. These edifices are similar to terrestrial tuyas, which form when a subglacial volcano breaches an ice sheet and erupts a plateau of sub-aerial lavas. Based on the geomorphologic map and topographic data, we have shown that flat-topped edifices are all located outside of regions that we map as the Mantled Unit, which we infer to be related to the Dorsa Argentina Formation. The combination of the flat topped edifices and their location outside of the mapped ice-related regions strongly suggests that the ice in the region was once more extensive than what is currently observed. While this has been proposed in the past, it has not been documented how far the ice sheet could have extended. Here we show that the ice must have extended to at least as far as the flat topped edifices in the region. The combination of these chapters using both mineralogy and morphology suggest that the Sisyphi Planum region of Mars was subglacial in origin. <br><br>

The study area extends from west of the Great Divide to the Broken Hill and Tibooburra regions of far western New South Wales, encompassing several important mining districts that not only include the famous Broken Hill lodes (Pb-Zn-Ag), but also Parkes (Cu-Au), Peak Hill (Au), Cobar (Cu-Au-Zn) and White Cliffs (opal). The area is generally semi-arid to arid undulating to flat terrain covered by sparse vegetation. ¶ During the Cretaceous, an extensive sea retreated across vast plains, with rivers draining from the south and east. After the uplift of the Great Divide associated with opening of the Tasman Sea in the Late Cretaceous, drainage swung to the west, cutting across the Darling River Lineament. The Murray-Darling Basin depression developed as a depocentre during the Paleogene. Climates also underwent dramatic change during the Cenozoic, from warm-humid to cooler, more seasonal climates, to the arid conditions prevalent today. Up until now, there has been very little temporal constraint on the development of this landscape over this time period. This study seeks to address the timing of various weathering and landscape evolution events in northwestern New South Wales. ¶ The application of various regolith dating methods was undertaken. Palaeomagnetic dating, clay δ18O dating, (U+Th)/He and U-Pb dating were all investigated. Palaeomagnetic and clay dating methods have been well established in Australian regolith studies for the last 30 years. More recently, (U+Th)/He dating has been successfully trialled both overseas and in Australia. U-Pb dating of regolith materials has not been undertaken. Each method dates different regolith forming processes and materials. Palaeomagnetic and clay dating were both successfully carried out for sites across northwestern New South Wales, providing a multi-technique approach to resolving the timing of weathering events. Although (U+Th)/He dating was unsuccessful, there is scope for further refinement of the technique, and its application to regolith dating. U-Pb dating was also unsuccessfully applied to late-stage anatase, which is a cement in many Australian silcretes. ¶ Results from this study indicate that the landscape evolution and weathering history of northwestern New South Wales dates back at least 60 million years, probably 100 million years, and perhaps even as far back as 180 million years. The results imply that northwestern New South Wales was continuously sub-aerially exposed for the last 100 Ma, indicating that marine sedimentation in the Murray-Darling and Eromanga-Surat Basins was separated by this exposed region. The ages also provide further evidence for episodic deep chemical weathering under certain climatic conditions across the region, and add to the data from across Australia for similar events. In particular, the palaeomagnetic ages, which cluster at ~60 ± 10 Ma and 15 ± 10 Ma, are recorded in other palaeomagnetic dating studies of Australian regolith. The clay ages are more continuous across the field area, but show older clays in the Eromanga Basin sediments at White Cliffs and Lightning Ridge, Eocene clays in the Cobar region, and Oligocene – Miocene clays in the Broken Hill region, indicating progressively younger clay formation from east to west across northwestern New South Wales, in broad agreement with previously published clay weathering ages from around Australia. ¶ These weathering ages can be reconciled with reconstructions of Australian climates from previously published work, which show a cooling trend over the last 40 Ma, following an extended period of high mean annual temperatures in the Paleocene and Eocene. In conjunction with this cooling, total precipitation decreased, and rainfall became more seasonal. The weathering ages fall within periods of wetness (clay formation), the onset of seasonal climate (clay formation and palaeomagnetic weathering ages) and the initiation of aridity in the late Miocene (palaeomagnetic weathering ages). ¶ This study provides initial weathering ages for northwestern New South Wales, and, a broad geochronology for the development of the landscape of the region. Building on the results of this study, there is much scope for further geochronological work in the region.

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.