Thesis (Ph. D.)--Texas A & M University, 1997. / Includes bibliographical references (leaves 241-250).

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Oblique dunes have orientations that are intermediate between those of transverse and longitudinal dunes. The oblique dunes studied are reversing dunes which undergo no net annual migration when associated with normal meteorological patterns. From April 1980 through September 1980, the dunes migrated up to 65 feet (19.8 m) northwestward under the influence of prevailing onshore winds. High velocity northerly winds (November 1980 through February 1981), associated with the passage of winter frontal systems, caused the dunes to rapidly migrate 65 feet (19.8 m) southward. Volumes of sand transported by these strong winds were commonly reduced by accompanying rainfall. In October 1980 and March 1981 neither wind direction was dominant, and frequent changes in wind direction caused many of the dunes to become flattened. Hurricanes, which strike the area in late summer, have had no lasting effects on the dunes. Three major stratification types were observed in trenches and on etched surfaces. Translatent strata were deposited by wind ripples; grainfall deposits accumulated when saltating grains settled on leeward slopes of the dunes, and grainflow cross-strata were developed by avalanching on leeward slopes. Preservation of these stratification types occurred in zones of net deposition, predominantly leeward of the dune crests. Strata deposited during the summer wind regime dip northeast, whereas the winter strata dip in a southerly direction. The winter deposits are best preserved in the central cores of the dunes. This suggests that either the high velocity winds of the initial winter frontal systems destroy large volumes of the summer deposits, or that the dunes migrate southward, under the influence of dry northerly winds, during droughts. Oblique dune deposits should be difficult to discern in the rock record, because they may contain aspects of either transverse or longitudinal dunes. It is likely that some ancient oblique dunes have been mistakenly described as other dune types in the literature. / text

As with most dune fields, the White Sands Dune Field in New Mexico forms in a wind regime that is not unimodal. In this study, dune behavior at White Sands was documented from a time series of five lidar-derived digital elevation models (DEM) and compared to a record of wind direction and speed during the same period. For the study period of June 2007 - June 2010, 244 sand-transporting wind events occurred and define a dominant wind mode from the SW and lesser modes from the NNW and SSE. Based upon difference maps and tracing of dune brinklines, overall dune behavior consists of migration to the NE, but with along-crest migration of dune sinuosity to the SE. Permutations of the DEMs allow matching specific dune behavior with wind modes. The SW winds are transverse to dune orientations and cause most forward migration. The NNW winds cause along-crest migration of dune sinuosity and low stoss bedforms, as well as SE migration of NE-trending dune terminations. The SSE winds cause ephemeral dune deformation, especially crestal slipface reversals. Dune deformation occurs because of unequal deposition along the lee face as a function of the incidence angle formed between the wind and the local brinkline orientation. Incidence-angle control on dune deformation and types of lee-face surface processes allows for an idealized model for White Sands dunes. The dunes behave as complex systems in which each wind event deforms the dune shape, this new shape then serves as the configuration for the next wind event. / text

Thèse de doctorat : Sciences physique et de l'ingénieur. Sciences du bois : Bordeaux 1 : 2008. Thèse de doctorat : Sciences physique et de l'ingénieur. Sciences du bois : Université Cheikh Anta Diop de Dakar : 2008. / Titre provenant de l'écran-titre.

Η παρούσα διπλωματική διατριβή με τίτλο «Μελέτη και καταγραφή αμμοθινικών συστημάτων στη Νότια Κέρκυρα» εκπονήθηκε στα πλαίσια πτυχιακής εργασίας του τμήματος Γεωλογίας της σχολής Θετικών Επιστημών του Πανεπιστημίου Πατρών. Στόχος της εργασίας είναι η κατανόηση της προέλευσης και εξέλιξης των αμμοθινών στη Νότια Κέρκυρα, η περαιτέρω σχέση τους με την λιμνοθάλασσα Κορισσίων και η καταγραφή των γενιών των θινών ,των ιδιαίτερων μορφολογικών χαρακτηριστικών τους και των επιπλέον γεωμορφών της περιοχής. Σκοπός της εργασίας είναι η κατανόηση της προέλευσης και εξέλιξης των αμμοθινών στη Νότια Κέρκυρα και η περαιτέρω σχέση τους με την λιμνοθάλασσα Κορισσίων. Στη συνέχεια η μετέπειτα καταγραφή των γενιών των θινών ,των ιδιαίτερων μορφολογικών χαρακτηριστικών τους και των επιπλέον γεωμορφών της περιοχής. / This diploma thesis entitled "Study and recording dune systems in southern Corfu" was accomplished in the dissertation of Geology, Faculty of Sciences, University of Patras. Aim of this work is to understand the origin and evolution of the dunes in South Corfu, further their relationship with Korission lagoon and recording generations of dunes, the specific morphological characteristics and additional landforms of the area. Aim of this study is to understand the origin and evolution of the dunes in South Corfu and further their relationship with Korission lagoon. Then the subsequent recording of generations of dunes, the specific morphological characteristics and additional landforms of the area.

Every species has a limit to its geographic distribution. The problem is that we don’t really know why. Classical explanations propose that range limits occur where the ecological conditions overwhelm adaptation and populations are no longer self-sustaining. It is generally expected that population abundance and fitness decline towards range margins across a gradient of declining habitat quality. Current evolutionary and theoretical explanations of range limits predict that this geographic pattern of demography will result in genetic constraints in marginal populations, such that range expansion is thwarted by reduced evolutionary potential. In this thesis, I tested the key assumptions and predictions of range limit theory through an empirical evaluation of two coastal dune, endemic plants; Camissonia cheiranthifolia (Spreng.) Raim. (Onagraceae) and Abronia umbellata L. (Nyctaginaceae). In geographic wide surveys of a large proportion of populations across both species’ ranges, neither species exhibited declining abundance or performance towards its range limits. Central populations of C. cheiranthifolia tended to have a higher production of seeds per unit area than marginal populations. Although this pattern demonstrated the potential for gene flow from central sites to swamp selection in marginal sites, results from a transplant experiment suggested that this was unlikely. Experimental populations of C. cheiranthifolia originating from ≥ 675 km south of the northern range limit exhibited similar levels of fitness when planted at the range margin. Along a 200 km transect across the limit, and in contrast to expectations, fitness of all populations increased towards the limit and generally remained high beyond the limit. Individuals from all populations reproduced and matured fruit beyond the limit, suggesting that if individuals dispersed beyond the limit that populations would establish. The species’ abrupt distributional limit also did not correspond to an abrupt shift in ecological conditions, despite the association of fitness with plant community and microhabitat variables. Overall, ecological tolerances to fitness or niche-based explanations to range limits do not adequately describe the distributions of either species. Constraints on dispersal rate, the influence of anthropogenic factors on habitat dispersion and limited genetic variability for fitness related traits are addressed. / Thesis (Ph.D, Biology) -- Queen's University, 2007-05-13 16:45:44.456

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Bibliography: v. 1, leaves 127-152 / 2 v. : ill. (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Geology and Geophysics, 1986

Thesis (Ph.D.)--McMaster University (Canada), 1991. / Source: Dissertation Abstracts International, Volume: 54-02, Section: B, page: 0699.