Only a small body of work currently exists regarding the geomorphology of humid tropical montane rivers. The research that does exist reports rapid geomorphic processes and high sediment loads compared to other montane rivers. This research applies traditional field survey methods combined with new applications of remote sensing techniques to examine the geomorphology and sediment dynamics of the montane portions of the Rio Pacuare in Costa Rica. A suite of geomorphic components (channel slope and width, lateral contributions and planform) are examined and a model presented that illustrates the complexity of the Rio Pacuare’s geomorphology and how the distribution of alluvial sediment varies in relation to geology (tectonics and lithology) and flow hydraulics (stream power). Next, average annual bedload sediment transport capacity is estimated using fifty-one years of daily discharge data at six different locations within the study area, including the temporal (monthly) variability of sediment flux due to dry versus wet season discharge regimes. Then, a time-step hydraulic model is created that simulates observed (modern) and potential future discharge scenarios based on regional climate change model results. The simulated discharge data for two locations within the study area is then integrated into the sediment transport model to examine how sediment flux, and thus channel geomorphology, is likely to change in response to changes in the river’s discharge regime.

Accelerating sea-level rise (SLR) poses an imminent threat to salt marshes, which sit within meters of mean sea level. In order to assess marsh vulnerability to SLR, we must first understand the fundamental processes governing marsh response to SLR. The objective of this dissertation work is to examine how marsh sedimentation and erosion affect the morphological development of marshes as sea level rises, over a broad range of spatial and temporal scales. At the smallest scale, the effects of bioturbation by Sesarma reticulatum crabs on sediment erodibility are examined using a laboratory flume. Measurements of surface elevation, erosion, and turbidity show that S. reticulatum bioturbation repackages formerly compacted sediment and deposits it above the surface, decreasing the threshold velocity for erosion and increasing eroded volume. S. reticulatum-induced sediment erosion can have broader impacts on creek development and marsh morphology. S. reticulatum has facilitated drainage network expansion in salt marshes at Sapelo Island, GA and Cape Romain, SC in response to local SLR. Burrowing by this crab directly adjacent to tidal creeks at these locations leads to rapid headward growth. The effects of site-specific conditions on creek expansion are examined through comparison of sediment properties, surface elevations, and historical rates of creek growth at each site. Results suggest that while similar processes are occurring at both locations, the higher elevation of the marsh in GA leads to greater shear strength and a larger volume of material to be eroded by creeks. These combined effects have led to slower creek growth compared to SC. At the largest spatial scale, and projecting forward over a 100-year period, a model for marsh response to SLR at the Great Marsh in Massachusetts is developed. This model takes into account limitations imposed by both low sediment availability and steep topography in the surrounding uplands. Results indicate that while the marsh may persist for several decades, it undergoes a dramatic shift in ecology and hydrology. As the rate of SLR accelerates, marsh loss increases due to the lack of sediment available for accretion and the physical barriers to migration presented by surrounding topography.

As conveyors of water and sediment, rivers play an instrumental role in landscape evolution (Turner et al., 2015). River systems were traditionally considered as passive pipes of terrestrial organic carbon (OC), but are now viewed as active sites of OC processing, redistribution and storage (Aufdenkampe et al., 2011). Floodplains are an important part of this system and have the capacity to act as sources or sinks of carbon (Zehetner et al., 2009), but most importantly active hotspots of organic matter (OM) transformation (Hoffmann et al., 2009; Zocatelli et al., 2013). POC eroded from highly-organic peat soils, may be interrupted in its transport through the fluvial system, by temporary storage on floodplain landforms (Evans and Warburton, 2005; Evans et al., 2006). It is important to investigate the fate of fluvial peatland POC, in order to fully close the terrestrial peatland carbon budget, to account for subsequent mineralisation and explore the processes that lead to redistribution and storage. The River Ashop in the southern Pennines, UK, drains the slopes of both Bleaklow and Kinder Scout which are upland plateaux, which support an extensive cover of blanket peat (Evans and Lindsay, 2010). These peatlands have been severely eroded and are vulnerable to future erosion as they are marginal to the climatic space suitable for growth of peat bogs in the UK (Clark et al., 2010). The wider peatland catchment features cohesive, organic-rich floodplains, which are atypical in an upland landscape, and thus suitable for investigation in their role in the fate of eroded carbon. OM quality was an important focus of this research into the redistribution of terrestrial organic carbon. As such, OM quality was conceptualised, by identifying how different research disciplines identify with the term, and ultimately providing a classification scheme to assist individuals in their exploration of OM character. A novel approach using ITRAX core scanning data was used to establish carbon stocks of floodplains in the River Ashop catchment. Sedimentological characteristics were insufficient to distinguish between allochthonous and autochthonous organic matter storage. However, dating was used as a rapid and accurate tool to assess carbon source on the 'off-site' floodplain, and could perhaps be used in the wider environment where there are large discrepancies between the ages of source materials. Investigations into the OM quality, provided suitably convincing evidence that substantial overbank deposition of eroded 'old' peat had occurred. Despite this, viewing these sites simply as areas of carbon storage is misleading. In fact, these systems have potentially been turning over substantial quantities of carbon to the atmosphere. Contextual information from modern-day fluvial POC fluxes showed that both 'off-site' and 'on-site' floodplains only play a minor role in storing carbon. Geomorphological events, particularly the substantial sediment flux generated from peatland erosion were critical in the formation of these floodplains. In these peatland systems, erosion, deposition and turnover of carbon are intimately linked at the landscape scale, and floodplains are a dynamic component of this system.

abstract: Previous workers hypothesized that lunar Localized Pyroclastic Deposits (LPDs) represent products of vulcanian-style eruptions, since some have low proportions of juvenile material. The objective of the first study is to determine how juvenile composition, calculated using deposit and vent volumes, varies among LPDs. I used Lunar Reconnaissance Orbiter Camera Narrow Angle Camera (LROC NAC) digital terrain models (DTMs) to generate models of pre-eruption surfaces for 23 LPDs and subtracted them from the NAC DTMs to calculate deposit and vent volumes. Results show that LPDs have a wide range of juvenile compositions and thinning profiles, and that there is a positive relationship between juvenile material proportion and deposit size. These findings indicate there is greater diversity among LPDs than previously understood, and that a simple vulcanian eruption model may only apply to the smallest deposits. There is consensus that martian outflow channels were formed by catastrophic flooding events, yet many of these channels exhibit lava flow features issuing from the same source as the eroded channels, leading some authors to suggest that lava may have served as their sole agent of erosion. This debate is addressed in two studies that use Context Camera images for photogeologic analysis, geomorphic mapping, and cratering statistics: (1) A study of Mangala Valles showing that it underwent at least two episodes of fluvial activity and at least three episodes of volcanic activity during the Late Amazonian, consistent with alternating episodes of flooding and volcanism. (2) A study of Maja Valles finds that it is thinly draped in lava flows sourced from Lunae Planum to the west, rendering it analogous to the lava-coated Elysium outflow systems. However, the source of eroded channels in Maja Valles is not the source of the its lava flows, which instead issue from south Lunae Planum. The failure of these lava flows to generate any major channels along their path suggests that the channels of Maja Valles are not lava-eroded. Finally, I describe a method of locating sharp edges in out-of-focus images for application to automated trajectory control systems that use images from fixed-focus cameras to determine proximity to a target. / Dissertation/Thesis / Doctoral Dissertation Geological Sciences 2018

In Louisiana, barrier islands are undergoing morphological change driven by high rates of relative sea-level rise and interior wetland loss. Previous works utilized historical region-scale bathymetry and shoreline change analyses to assess coastal evolution. However, more localized assessments considering the role of sediment transport processes in regional evolution are lacking. This is essential to predicting coastal change trajectories and allocating limited sand resources for nourishment. Using bathymetric and shoreline data, 100-m spaced shore-normal transects were created to track meter-scale elevation change for 1880s, 1930s, 1980s, 2006, and 2015. An automated framework was used to quantify and track parameters such as shoreline change, barrier island area and width, bathymetric isobath migration, and shoreface slope. Our results illustrate that monitoring subaerial island erosion rates are insufficient for evaluating regional sediment dynamics of transgressive coastal systems. Advances in understanding these processes will facilitate more informed planning, management, and mitigation of transgressive barrier islands.

General Statement A detailed study of the southwestern part of the Randolph quadrangle was undertaken in view of the fact that Richardson (1941) mapped a large area of undifferentiated Ordovician rock. Therefore, the purposes of this investigation are: (1) to prepare a more detailed geologic map of the south­western part of the Randolph quadrangle (Plate 1), (2) to describe the struc­ture, stratigraphy, and geologic history of the area, and (3) to relate the geology to adjacent areas. The elevation of the area mapped ranges from approximately 8, 910 to 6, 700 feet above sea level with the major part of the area above 8, 000 feet. This area forms part of the eastern ridge of the Bear River Range (Williams, 1948, p. 1, 125-1, 126). The southern boundary of the area extends east from the southwest corner of the Randolph quadrangle for a distance of about 4 miles. The eastern boundary extends northward about 11 miles and is parallel to the mountain front. The northern boundary is less well defined and is taken as the ridge separating Curtis Creek from the next canyon to the north. The western boundary extends south approximately 10 miles to the southwest corner of the Randolph quadrangle. The southwestern part of the Randolph quadrangle (Figure 1) covers approximately 56 square miles and lies approximately 60 per cent in Cache County and 40 per cent in Rich County. The major part of the area lies within the Cache National Forest. The area mapped is generally accessible from mid-June to mid- September. A road is maintained along the length of the area by the U. S. Forest Service and is passable by automobile except during heavy rain- storms in the summer months. Field Work The field work was done during the summer of 1963. Formation con- tacts, attitudes, and faults were mapped in the field on aerial photographs of the approximate scale 1:20, 000. This information, concerning the south- western part of the Randolph quadrangle, was transferred to a base map constructed from the topographic map of the U. S. Geological Survey of the same area (1912 edition). The base map was enlarged to the scale 1:24, 000. Stratigraphic sections were measured with a 50-foot steel tape. A Brunton compass was used to measure attitudes and slope angles. Sample rock types were collected from each unit and compared with the rock-color chart (Goddard, 1951) to obtain standard color names. Fossils were collected and identified in the laboratory by the author. Previous Investigations The earlier geologic reports from the general area of the Randolph quadrangle are found in the Hayden Survey and the survey of the Fortieth Parallel supervised by King. Hayden (1871, p. 150-156), Peale (1877, p. 573-609), Hague (1877, p. 393-442), and Emmons (1877, p. 326-393) all commented upon the general area. Walcott (1908) studied the Cambrian rocks of the Bear River Range and defined eight formations. Veatch (1907) studied the area adjacent to the Randolph quadrangle in Wyoming. In the Randolph quadrangle, Richardson (1913) divided the Ordovician rocks into three formations, identified the Silurian rocks as a formation, defined one Mississippian formation, and later (1941) published a geologic map of the quadrangle. Mansfield's (1927) study of southeastern Idaho provided valu­able information concerning regional structure and stratigraphy. Williams (1948) mapped the Logan quadrangle which is adjacent to the area on the west. Specific studies (Ross, 1949, 1951; Maxey, 1941, 1958) have given more detailed information concerning Cambrian and Ordovician rocks of the area. A recent publication by Armstrong and Cressman (1963) is important in dating the uplift and thrust faulting in the ancestral Bear River Range. The Geologic Map of Utah (Stokes, 1961) followed the interpretaion of Richardson (1941), for the southwestern part of the Randolph quadrangle, except in the designation of the Wasatch formation which is shown as Knight conglomerate.

Longitudinal profile, channel cross-section geometry, and depositional patterns of the Green River in its course through the eastern Uinta Mountains are each strongly influenced by river -level geology and tributary sediment delivery processes. We surveyed channel cross sections at 1-km intervals, mapped surficial geology, and measured size and characteristics of bed material in order to evaluate the geomorphic organization of the 70- km study reach. Canyon reaches that are of high gradient and narrow channel geometry are associated with the most resistant lithologies exposed at river level and the most frequent occurrences of tributary debris fans. Meandering reaches that are characterized by low gradient and wide channel geometry are associated. with river-level lithology that is of moderate to low resistance and very low debris fan frequency. The channel is in contact with bedrock or talus along only 42 percent of the bank length in canyon reaches and there is an alluvial fill of at least 12 m that separates the channel bed from bedrock at three borehole sites. The influence of lithology primarily operates through the presence of resistant boulders in debris fans that are delivered by debris flows from steep tributaries. The depositional settings created by debris fans consist of (1) channel-margin deposits in the backwater above the debris fan, (2) eddy bars in the zone of recirculating flow below the constriction, and (3) expansion gravel bars in the expansion below the zone of recirculating flow. These fan-eddy complexes are the storage location of about 70 percent. by area, of all fine- and coarse-grained alluvium contained within the canyons above the low-water stage. Immediately adjacent meandering reaches contain an order of magnitude more alluvium by area but have no debris fan-created depositional settings. This study also describes the flood-plain and terrace stratigraphy of the Green River in the eastern Uinta Mountains and changes due to the operations of Flaming Gorge Dam, upstream from the study area. These landforms are vertically aggrading deposits that are longitudinally correlative throughout the 65-km study reach. The suite of surfaces identified includes a terrace that is inundated by rare pre- or post-dam floods, an intermediate bench that is inundated by rare post-dam floods, and a post-dam flood plain that is inundated by the post-dam mean annual flood. Analysis of historical photographs in the study reach shows that both the intermediate bench and post-dam flood plain are landforms that were not present in any of the 6 years for which photographs were examined between 1871 and 1954. Photographic replications also show that gravel bars consisting of bare gravel in 1922 and earlier photographs are now covered by fine-grained alluvium and vegetation . Decreased gravel-bar mobility is indicated by estimates of critical and average boundary shear stress. Comprehensive surficial geologic mapping of the study area indicates that the bankfull channel has decreased in width by an average of about 20 percent.

One of the profound realizations in Earth science during the last several decades has been that the solid earth and climate system interact through mountain belt evolution. Tectonic forces generate topography, and erosion, driven largely by the climate, destroys topography. Perturbations to the competition between these processes may, for example, have driven the transition from greenhouse to icehouse climate during the Cenozoic. Erosion is the ultimate connection between the climate and solid earth system, and because landscapes are shaped by erosion, they hold in their form information about climatic and tectonic forcings. Reading climatic and tectonic processes from the landscape requires an understanding of how these processes drive erosion. One way that climate influences erosion is by setting the elevation at which glaciation occurs. It has been thought for over a century that erosion by glaciers can limit the height of cold, heavily glaciated mountains. In this thesis, I argue that the prevalence of this phenomenon is underappreciated, and that glacial erosion has imposed an upper limit on the growth of warm, tropical mountains. The argument is premised on a combination of field observations from two (sub)tropical mountain ranges in Costa Rica and Taiwan (including 10Be and 3He surface exposure ages), a new method of topographic analysis that identifies previously unrecognized patterns of landscape rearrangement introduced by high elevation glaciation, and a study of ten tropical mountain ranges that reveals a widespread glacial control on their height. The results of this thesis demonstrate the efficacy of glacial erosion even in the warmest mountains, and challenge the hypothesis that quickly uplifting and eroding landscapes have approached a steady state balance between rock uplift and fluvial erosion during the Pleistocene.

Cova des Pas de Vallgornera (CPV) is morphologically and scientifically, the most prominent karst feature of Mallorca Island (Spain). It consists of over 74 km of passages developed within two carbonate lithologies (reef front and back reef facies) of Upper Miocene age. Two distinct cave patterns are recognized, both tightly controlled by the type of facies; spongework mazes and collapse chambers are characteristic for the reef front unit, whereas linear, fracture-guided galleries develop in the back reef carbonates. CPV is abundantly decorated with a variety of speleothems. The overarching goal of this study is to provide evidence towards the cave's major speleogenetic pathways using diagnostic mineral assemblages and a set of micro- and macro-scale morphological features. In particular, this research investigates whether hypogene processes were/are the main driving force in CPV's speleogenesis and how mineral assemblages and cave morphologies help untangle the complex evolution of the cave. The mineralogy of speleothems (crusts, nodules, crystals, earthy masses) deposited in the vicinity of hypogene features in the reef front is characterized by the presence of aragonite, ankerite, huntite, clay minerals, and quartz. In the back reef limestone, however, the dominant mineral is dolomite, along with aragonite, celestine, huntite, clay minerals, and quartz. Calcite is by far the most ubiquitous mineral throughout the cave. A total of twenty-six minerals were identified throughout the cave; the highest diversity (20 species) is around or inside typical hypogene features occurring within the back reef limestone, whereas in the seaward part only 13 minerals occur. Detailed macroscopic and scanning electron micro-chemical analysis and imaging have permitted the investigation of textural relationships between the minerals associated with vents, rims, and corrosion cupolas above them. These studies along with morphological and stable isotope analyses (δ13C, δ18O, δ34S), confirm that not all minerals are connected with a hypogene stage in the cave evolution, and furthermore, none of them appears to be sulfuric acid by-products. Instead, the mineral assemblages documented in speleothems from CPV clearly support at least three speleogenetic pathways, namely seacoast mixing, ascending of warm groundwaters (basal recharge), and vadose (meteoric recharge). In summary, we have shown that cave minerals (in association with particular cave morphologies) in CPV hold the keys to understanding mineral-forming processes, conditions, and events, allowing establishing their relationship with various speleogenetic pathways.

No description available.