Flume studies on the kinematics and dynamics of large-scale bed forms

Thesis (Sc.D.)--Massachusetts Institute of Technology, Dept. of Earth and Planetary Science, 1981.Microfiche copy available in Archives and ScienceVita.Bibliography: leaves 170-178.by Kevin Michael Bohacs.Sc.D

How to make a 350-m-thick lowstand systems tract in 17,000 years : The Late Pleistocene Po River (Italy) lowstand wedge

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Fate of terrigenous organic carbon in muddy clinothems on continental shelves revealed by stratal geometries: Insight from the Adriatic sedimentary archive

Continental shelves host 90% of modern Organic Carbon (OC) burial and play a key role in the sequestration of terrigenous OC over geological timescales. The efficiency of OC burial in these systems, however, varies greatly depending on the duration of exposure to oxic-suboxic conditions during sediment transport. In this study, we use observations across a wide range of stratigraphic and sedimentological scales coupled with geochemistry data from muddy shelf deposits along the western Adriatic to investigate the relation between sediment transport and burial of terrigenous (land-derived) fraction of OC (OCTerr). Our analysis focused on the Little Ice Age (LIA, 1500-1850 CE) interval, which was characterized by wet, cold, and stormy weather conditions, before the time of widespread regulation and damming of rivers. On the Adriatic shelf, LIA deposits are organized as clinothem: strata that dip gently seawards. The LIA clinothem becomes progressively steeper and deeper from north to south. Basin-scale seismic-stratigraphic analysis and biogeochemical data show evidence of elongated stratal units associated with low OCTerr content in the northern sector of the LIA clinothem, whereas farther south, where clinoforms are steeper, the LIA clinothem exhibits wavy stratal units with limited cross-shelf continuity and high OCTerr concentrations. Based on these data we infer two contrasting scenarios for OCTerr deposition during the LIA: 1) protracted sediment redistribution under the influence of coastal currents with efficient OCTerr degradation prior to final burial in the northern sector; and (2) rapid deposition of OCTerr-rich event beds as a result of flood-driven hyperpycnal flows with limited dispersion across the shelf in the southern sector. The latter scenario of deposition resulted in scattered hot spots of OCTerr burial along the apparently homogeneous western Adriatic shelf deposit. Our work documents significant lateral variability of a fine-grained system in which hot spots of OCTerr can be preserved in scattered prodelta bedsets (<1 km in across-shelf lateral continuity) over a 600 km long shelf. Shelfal clinothems worldwide should not be considered as homogeneous pools of OCTerr because of the influence of river, storm, and oceanic currents

Avulsion cycles and their stratigraphic signature on an experimental backwater‐controlled delta

River deltas grow in large part through repeated cycles of lobe construction and channel avulsion. Understanding avulsion cycles is important for coastal restoration and ecology, land management, and flood hazard mitigation. Emerging theories suggest that river avulsions on lowland deltas are controlled by backwater hydrodynamics; however, our knowledge of backwater-controlled avulsion cycles is limited. Here, we present results from an experimental delta that evolved under persistent backwater hydrodynamics achieved through variable flood discharges, shallow bed-slopes, and subcritical flows. The experimental avulsion cycles consisted of an initial phase of avulsion setup, an avulsion trigger, selection of a new flow path, and abandonment of the parent channel. Avulsions were triggered during the largest floods (78% of avulsions) after the channel was filled by a fraction (0.3 ± 0.13) of its characteristic flow depth at the avulsion site, which occurred in the upstream part of the backwater zone. The new flow path following avulsion was consistently one of the shortest paths to the shoreline, and channel abandonment occurred through temporal decline in water flow and sediment delivery to the parent channel. Experimental synthetic stratigraphy indicates that the bed thicknesses were maximum at the avulsion sites, consistent with our morphologic measurements of avulsion setup and the idea that there is a record of avulsion locations and thresholds in sedimentary rocks. Finally, we discuss the implications of our findings within the context of sustainable management of deltas, their stratigraphic record, and predicting avulsions on deltas

Reconstructions of deltaic environments from Holocene palynological records in the Volga delta, northern Caspian Sea

This article was made available through open access by the Brunel Open Access Publishing Fund.New palynological and ostracod data are presented from the Holocene Volga delta, obtained from short cores and surface samples collected in the Damchik region, near Astrakhan, Russian Federation in the northern Caspian Sea. Four phases of delta deposition are recognized and constrained by accelerated mass spectrometry (AMS) radiocarbon ages. Palynological records show that erosive channels, dunes (Baer hills) and inter-dune lakes were present during the period 11,500–8900 cal. BP at the time of the Mangyshlak Caspian lowstand. The period 8900–3770 cal. BP was characterized regionally by extensive steppe vegetation, with forest present at times with warmer, more humid climates, and with halophytic and xerophytic vegetation present at times of drought. The period 3770–2080 cal. BP was a time of active delta deposition, with forest or woodland close to the delta, indicating relatively warm and humid climates and variable Caspian Sea levels. From 2080 cal. BP to the present-day, aquatic pollen is frequent in highstand intervals and herbaceous pollen and fungal hyphae frequent in lowstand intervals. Soils and incised valley sediments are associated with the regional Derbent regression and may be time-equivalent with the ‘Medieval Warm Period’. Fungal spores are an indicator of erosional or aeolian processes, whereas fungal hyphae are associated with soil formation. Freshwater algae, ostracods and dinocysts indicate mainly freshwater conditions during the Holocene with minor brackish influences. Dinocysts present include Spiniferites cruciformis, Caspidinium rugosum, Impagidinium caspienense and Pterocysta cruciformis, the latter a new record for the Caspian Sea. The Holocene Volga delta is a partial analogue for the much larger oil and gas bearing Mio-Pliocene palaeo-Volga delta.Funding for the data collection and field work was provided from the following sources: 1 – IGCP-UNESCO 2003–2008 (Project 481 CASPAGE, Dating Caspian Sea Level Change); 2 – NWO, Netherlands Science Foundation and RFFI, Russian Science Foundation 2005–2008 (Programme: ‘VHR Seismic Stratigraphy and Paleoecology of the Holocene Volga Delta’); and 3 – BP Exploration (Caspian Sea) Sea Ltd. (Azeri-Chirag-Gunashli) 2005–2008 (‘Unravelling the Small-Scale Stratigraphy and Sediment Dynamics of the Modern Volga Delta Using VHR Marine Geophysics’). The palynological work was funded jointly by BP Exploration (Caspian Sea) Ltd., Delft University of Technology and KrA Stratigraphic Ltd. Ostracod analyses were funded by StrataData Ltd. and funding for two additional radiocarbon dates provided by Deltares

The late Pleistocene Po River lowstand wedge in the Adriatic Sea : Controls on architecture variability and sediment partitioning

The authors dedicate this study to their colleague Giovanni Bortoluzzi, who passed away in 2015. A special tanks is due to Marco Ligi and Nevio Zitellini for geophysical data acquisition and processing; Marco Pastore and Filippo D'Oriano for their support during the cruise LSD2014 and processing of geophysical data. Elisabetta Campiani provided additional support for processing the multibeam bathymetry. A particular thank goes to Cpt. Emanuele Gentile and the crew of the R/V Urania during cruise LSD 2014. We thank Ronald Steel and an anonymous Reviewer for their constructive comments. This project was funded by ExxonMobil Upstream Research Company and by the Flagship Project RITMARE–The Italian Research for the Sea. We acknowledge the European Union Project PROMESS-1 (contract EVR1-2001-41) for borehole PRAD 1-2. This is ISMAR-CNR contribution number 1959.Peer reviewedPostprin

Assessment van Kinderen en jongeren: noodzaak om de blik te verruimen

Het onderwijs wordt geconfrnteerd met het dilemma om deprstaties en rendement van leerlingen te verhogen en anderzids ook iets te doen voor een groelend aantal uitvallers of onderpresteerders. Het Daffodil.project is een Europees Comenius- project is een Europees Comenius_multilateral samenwerkingsproject met partners uit 7 landen (Belgie, Hongarije, Zweden,Portugal, Noorwegen, Roemenie en de Britse Maagdeneilanden)met als doel een model te ontwikkelen dat bruikbaar is om het functioneren van kinderen met een probleem beter in kaart te brege

Towards a more functional and dynamic assessment of children with special needs in function of more inclusive education

Towards a more functional and dynamic assessment of children with special needs in function of more inclusive education - We present the Guidelines for Inclusive Assessment of children that experiment Special Educational Needs, developed by the DAFFODIL project team