Sedimentology

Towards the northwest of San Luis Potosí City, a detailed stratigraphic and sedimentological analysis make (89 variable-scale sedimentological logs and 900 paleocurrent data). This study took place in outcrops attributed to the Caracol Formation. Based on its lithological and facial variation, this analysis allowed to informally dividing this unit in two lithostratigraphic members: 1) the “Santa Teresa” deep-marine member, from Coniacian-Santonian age; and 2) the “El Pedregal” shallow-marine member, possibly from the Later Santonian age.
The Santa Teresa deep-marine member distinguished by a shale, siltstone and sandstone succession with scare conglomerate lenses and marly-carbonates interbedded. This member concordantly overlies the Indidura Formation, and we document an approximate thickness of 1000 m, with an age varying from Later Coniacian to Santonian, obtained through the following ammonites species: Texanites nodosus, Texanites quinquenodosus(?) and Texanites gallicus(?). The sedimentological characteristics that this member exhibits, allow us to distinguish at least two implicated systems: i) a mixed-type submarine channel system with a meandering geomorphology, moderate sinuosity, composed of channel-axis and channel-fill facies associations which laterally change to inner levee and channel abandonment facies associations. We documented as well outer levee and depositional lobe subordinated associations, and ii) an hyperpicnal system that presents moderate sinuosity hyperpicnal channels with meandering geomorphology, along with overbank systems and their associated hyperpicnal lobe.
On the other hand, El Pedregal shallow-marine member constituted by a shale, siltstone, and mudstone and marly-mudstone succession that concordantly overlies the Santa Teresa member and discordantly underlies continental units from the Paleogene formations. The approximate thickness of this interval is of 300 meters, with a Santonian age determined by its stratigraphic position. The sedimentological characteristics that the clastic units from this member presents, allow us to interpret the presence of estuarine and delta-front systems, dominated by tides and rivers. Somewhat, the carbonated units exhibit characteristics of open-shelf environments, influenced by waves and storms processes, characterized through hummocky and swaley crossed lamination, which are indicative of a sequence limit (discontinuity) between the deep and shallow members.
This work is only focused on the Santa Teresa deep-marine member, where by means of the analysis of its sedimentological characteristics, was possible to interpret 11 depositional sub-environments and its relative spatial-temporal relations, and documented the depositional models for each facies association and their environmental evolution model within a tectonic context. The models was establishing through the interpretation of the architectural elements applying analogue sedimentation models for the foredeep depozone into retro-arc foreland basins.
The sequence known as Caracol Formation that outcrops in the central part of the San Luis Potosi State represents a progradational system from deep to shallow-marine environments. The Santa Teresa deep-marine member is a result of an early phase generated on a structurally confined basin with a sedimentary input from submarine channel complexes developed subparallel to the orogenic belt (transport direction: SE-S), and hyperpicnal system which mean S-SW input direction. This results can be interpreted a close relationship with the emerged paleoelement known as Valles-San Luis Potosí Platform (PVSLP), and that this first phase is stratigraphically delimited to the top by storm-deposits from the e base of the El Pedregal shallow-marine member sequence.

A ca. 20 mm thick spherule bed representing Chicxulub impact ejecta deposits and marking the Cretaceous/Paleogene (K/Pg) boundary was recently discovered on Gorgonilla Island (Gorgona National Natural Park, Pacific of Colombia). This discovery represents the first confirmed record of the K/Pg event in Colombia, South America and the eastern Pacific Ocean. The deposit consists of extraordinarily well-preserved glass spherules (microtektites and microkrystites) reaching 1.1 mm in diameter. Importantly , the Gorgonilla spherule bed is unique relative to other K/Pg boundary sites in that up to 90% of the spherules are intact and not devitrified, and the bed is virtually devoid of lithic fragments and microfossils. The spherules were deposited in a deep marine environment, possibly below the calcite compensation depth. The preservation, normal size-gradation, presence of fine textures within the spherules, and absence of bioturbation or traction transport indicate that the Gorgonilla spherules settled within a water column with minimal disturbance. The spherule bed may represent one of the first parautochthonous primary deposits of the Chicxulub impact known to date. 40 Ar/ 39 Ar dating and micropaleontological analysis reveal that the Gorgonilla spherule bed resulted from the Chicxulub impact. Intense soft-sediment deformation and bed disruption in Maastrichtian sediments of the Gorgonilla Island K/Pg section provide evidence for seismic activity triggered by the Chicxulub bolide impact, 66 million years ago. It is also notable that the basal deposits of the Danian in the Colombian locality present the first evidence of a recovery vegetation, characterized by ferns from a tropical habitat, shortly following the end-Cretaceous event.

En este trabajo se presenta el estudio tafonómico de vertebrados fósiles procedentes de la Formación Loncoche (Campaniano tar-dío-Maastrichtiano temprano) en el área de Calmu-Co, Provincia de Mendoza, Argentina. En esta localidad se reconocieron cuatro etapas ambientales: (1) sistemas lacustres salinos; (2) sistemas fluviales; (3) sistemas deltaicos; (4) sistemas fluviales y lacustres someros. Los verte-brados hallados en el ambiente deltaico comprenden concentraciones desarticuladas parautóctonas-alóctonas (tafofacies 1) de peces (Chon-drichthyes, Teleostei, Lepisosteidae y Ceratodontidae), tortugas (Chelidae), dinosaurios (Titanosauria) y plesiosaurios (Plesiosauria). El carácter desarticulado y fragmentario de estas concentraciones mixtas (terrestres, dulceacuícolas y marinas), sugiere la mezcla de restos de ambientes litorales con los provenientes de sistemas fluviales. Esta interpretación se sustenta en los atributos tafonómicos de estas concentraciones, que muestran alto grado de meteorización, abrasión y mezcla temporal. En contraste, en el ambiente fluvial se registran concentraciones desarti-culadas parautóctonas (tafofacies 2) de dinosaurios, con procesos de fragmentación y abrasión debido al transporte hidráulico. Los procesos fosildiagenéticos incluyen eventos de permineralización y cementación de canales vasculares y fracturas, fenómenos de deformación y com-presión litostática. Estas evidencias indican que la ingresión marina atlántica (Maastrichtiano-Paleoceno) que cubrió el norte de Patagonia, se extendió hasta Calmu-Co, área occidental de la Cuenca Neuquina. Palabras clave. Argentina. Mendoza. Cretácico Superior. Vertebrados. Tafonomía. Ambiente fluvio-deltaico. Abstract. VERTEBRATE TAPHONOMY OF UPPER CRETACEOUS VERTEBRATES FROM THE LONCOCHE FORMATION IN CALMU-CO (MENDOZA, ARGENTINA): PALEOENVIRONMENTAL AND PALEOGEOGRAPHICAL IMPLICATIONS. This paper presents a taphonomic study of vertebrate fossils from the Loncoche Formation (late Campanian-early Maastrichtian) found in the Calmu-Co area in Mendoza, Argentina. Four environmental stages were recognized in this site, (1) saline lacustrine systems; (2) fluvial systems ; (3) deltaic systems; (4) shallow fluvial and lacustrine systems. The vertebrates found in the deltaic environment comprise disarticulated parautochthonous-allochthonous concentrations (taphofacies 1) of fishes (Chondrichthyes, Teleostei, Lepisosteidae and Ceratodontidae), turtles (Chelidae), dinosaurs (Titanosauria) and plesiosaurs (Plesiosauria). The disarticulated and fragmentary feature of these mixed concentrations (terrestrial, freshwater, marine) suggest a mixture of remains from littoral environments and fluvial systems. The above interpretation is based on the taphonomic attributes of these concentrations, which showed a high degree of weathering, abrasion and time-averaging. On the other hand, disarticulated parautochthonous concentrations (taphofacies 2) of dinosaurs were registered in the fluvial environment. These remains showed processes of fragmentation and abrasion due to hydraulic transport. Fossil-diagenetic processes include events of perminer-alization and cementation of vascular canals and fractures, phenomena of deformation and lithostatic compression. These evidences indicate that the Atlantic marine ingression (Maastrichtian-Paleocene) which covered northern Patagonia, spread until Calmu-Co, in the western Neuquén Basin.

Over the past twenty years, increased geoarchaeological studies enable not only to reconstruct past environments and their morpho-sedimentary dynamics, but also to specify the formation processes of archaeological records. In return, the many archaeological results obtained from these investigations enable to reconstruct more accurately chronostratigraphic and chronocultural frameworks and to characterize the activity systems and space organisation of settlements and their exploited territories, from Paleo-lithic to historic period. Thus, are invited to this session all contributions which, involve a synthetic geoarchaeological approach dealing with social-environmental interactions with multidisciplinary work (i.e., geomorphology, stratigraphic analysis, micromorpholo-gy, geochemistry…). This will allow us to discuss some speci�ic aspects to the geoarchaeo-logical approach, such as taphonomy, scale of analysis and resilience. Therefore, we accept papers explaining the over-or under-representation of some periods of occupation due to problems of differential conservation of the remains. Moreover, through a local or regional approach, the question of anthropisation of soil and paleoenvironments according to the forcing human activities in quaternary systems are welcomed. Finally, we will pay special attention to questions such as the ability of environments to regenerate despite anthro-po-disturbances and adaptability of human behaviours to the environment.
Grégory Dandurand, Anaëlle Vayssière, Mathieu Rué, Marylise Onfray

Estudio sedimentológico en la cuenca de la quebrada La Floresta en los municipios de Pailitas y Tamalameque, departamento del Cesar, Colombia Sedimentological study in the basin of La Floresta brook located in the municipality of Pailitas and Tamalameque, department of the Cesar, Colombia DOI: http://dx.doi.org/10. sedimentológico en la cuenca de la quebrada La Floresta en los municipios de Pailitas y Tamalameque, departamento del Cesar, Colombia", INGE CUC, vol. 15, no. 2, 2019. DOI: http://doi.org/10.17981/ingecuc.15.2.2019.08 Resumen Introducción: La quebrada La Floresta se localiza entre los municipios de Pailitas y Tamalameque, cuenta con una extensión de 13.500 hectáreas, donde se realizaron estudios granulométricos, humedad y estimación de volumen de sedimentos aportados por la cuenca mediante el modelo EROSUP-U. Objetivo: Cuantificar el aporte sedimentológico de la quebrada La Floresta y clasificar tipos de suelo basado en AASTHO y USC. Metodología: Se recolectaron 84 muestras, cada 10 mts y 15 mts, siguiendo la metodología propuesta por la Comisión Federal de Electricidad de México. Resultados: La estimación volumétrica, aplicando la ecuación universal de perdida de suelo (EUPS), establece que el aporte sedimentológico de la quebrada es de 4.944.679.344,77 m 3 /año; el suelo se clasificó en cuatro (4) grupos (A-1-a, A-1-b, A-2-4, A-2-6), el más representativo es el A-1-a con un 84.52% de las muestras analizadas. Conclusiones: La quebrada La Floresta cuenta con una amplia variabilidad granulométrica de sedimentos, siendo de mayor proporción las grava, arena gruesa y arena fina, con o sin material fino bien graduado, con predominio de gravas y un aporte sedimentológico de 4.944.679.344,77 m 3 /año. Palabras clave: Clasificación de suelos, Abstract Introduction: La Floresta brook is located between the municipalities of Pailitas and Tamalameque, has an extension of 13,500 hectares, where granulometric studies, humidity and sediment volume estimation contributed by the basin through the model EROSUP-U. Objective: In order to quantify the sedimentological contribution and classify the soil type based on AASTHO and USC. Methodology: 84 samples were collected, each 10mts and 15mts, following the methodology proposed by the Federal Electricity Commission of Mexico. Results: The volumetric estimation, applying the universal equation of soil loss (EUPS), establishes that the sedimentological contribution of the brook is of 4,944,679,344.77 m3 / year; the soil was classified into four (4) groups (A-1-a, A-1-b, A-2-4, A-2-6), the most representative is A-1-a with 84.52% of the samples analyzed. Conclusions: La Floresta brook has a wide granulometric variability of sediments, with a greater proportion of gravel, coarse sand and fine sand, with or without well-graduated fine material, with a predominance of gravels and a sedimentological contribution of 4,944,679,344.77 m 3 / year.

Bank full discharge is generally considered to be the dominant steady flow which would generate the same regime channel shape and dimensions as the natural sequences of flows would. This is because investigation on the magnitude and frequency of sediment transport have determined that for stable rivers the flow which in the longer term transports most material has the same frequency of occurrence as bankfull flow. For stable gravel-bed rivers, this is considered to be the 1.5-year flood.

ABSTRACT This article aims to present the Holocene dynamics that are responsible for the creation and the evolution of the delta of the Kalamas River (65 km2, the smallest delta of Epirus, northwestern Greece). Archaeological remains prove a continuous occupation since the Upper Paleolithic times (site of Pyrgos Raghiou). In connection with the two archaeological sites of Mastilitsa (Bronze Age) and Pirgos Raghiou (continuous occupation since the Upper Paleolithic) and the published archaeological data, this paper presents the first results concerning the Holocene evolution of the delta. The methodology adopted crosses both geophysical data (seven profiles of electrical resistivity along three transects) and sedimentological studies, obtained through fourteen cores. The results are presented in two complementary parts: the first one emphasises the existence of several Holocene buried palaeochannels near the archaeological sites. The second presents the first description of the successive environments since 7440 BP. These results, associated with a series of three 14C datings, can open up interesting prospects for research on the environmental changes that occurred at the beginning of the Holocene.

Kepulauan Seribu means "Thousand Islands" and refers to a chain of small "coral islands", located 6" south of the equator in the West .Java Sea about 50 kilometers northwest of Jakarta, Indonesia. They are also referred to as "Pulau Seribu", a popular westernized version of the proper name, which actually means "thousand island" (singular). These islands provide an excellent field laboratory to demonstrate comparisons between living Holocene reef systems and Tertiary reef facies which host a major portion of Indonesia's hydrocarbon reserves. Kepulauan Seribu is easily reached from Jakarta, and numerous carbonate seminars have been conducted in this popular vacation area (Scrutton, 1978; Cook, 1985; Jordan et al., 1993).

Two groups of islands lie off the northern coast of Java: 1) those associated with the Kepulauan Seribu reefs and 2) those on reefs in Jakarta Bay and along the Java coast west of the bay. Islands referred to in the text are identified in Fig. 3. Modern studies of the Kepulauan Seribu reefs were conducted by Scrutton (1976) and Park et al. (1992) among others. Pioneering studies by Umbgrove (1928, 1929, 1939, and 1947) focused on the southernmost reefs in Jakarta Bay and laid the foundation for modern sedimentological work. The present report includes both areas of reef development, but concentrates on the reefs of Kepulauan Seribu. Preliminary results of this work were published by Jordan et al., 1985.

We present a high-resolution 1:15,000 bathymetric map (Main map) of Alderney Race located offshore of northwestern France, with the strongest currents in Europe. We use this map, underwater video transects and Shipek grabs to improve geological maps previously published. We distinguished Proterozoic crystalline rocks, Paleozoic and Cretaceous sedimentary rocks on the present-day sea floor. Some structures as faults and folds are also mapped. We identified a Quaternary cover made of pebbles, boulders and blocks interpreted as corestones resulting in differential erosion and alteration of the substratum. This cover is commonly encrusted by fixed fauna, such as bryozoans and barnacles. Finally, we describe the present-day mobile sediment cover characterized by sand patches and pebble dune fields (up to 10 m in height). Our videos show the presence of mobile fine-grained sediment patches under the resolution of our map lying between the cobble and pebble cover. We summarize our interpretations on a non-exhaustive geological-sedimentary map. ARTICLE HISTORY

The geological complexity in north Serayu basin make it as “Terra Incognita” in oil and gas exploration field in northern Java. As one of the challenge in oil and gas exploration, it can be used to know the petroleum system and the approach to reduce failure risk in exploration activity. This research aims to know the petroleum system in north Serayu basin specifically in Paguyangan, Brebes, Central Java. Methodology in this research is geological mapping method consist of facies and environmental sedimentation analysis, Total Organic Carbon (TOC) analysis, and petroleum system analysis. This research proceed from observation of rock layers arrangement in detail consisting of sediment structure, sedimentation environment, fossil composition contained in the rocks, and stratigraphy that grown in research area, which later grouped into some facies type. According to the field data and laboratory data analysis, it can be found that Rambatan Formation has good potential as source rock. The emergence of oil seepage in research area shows that there is petroleum system that can be found in channel filler rocks such as pebbly sandstone from Halang Formation that is interpreted as reservoir zone. Meanwhile, the caprock is interpreted as claystone from upper Tapak Formation. The trap in research area is structural trap that is anticline and thrust fault in Miocene - Pliocene, which possibly happened because of hydrocarbon migration route in late Miocene. From geology cross-section model, it is shown the factor that controls released hydrocarbon is fractures that formed on the peak of anticline. The results of TOC is in low to middle range showed by TOC value 0,43 - 1,2%. Kerogen type of the tested sample shows the kerogen type III and also identified that there is potential to generate a small amount of hydrocarbon into gas.

The study area is located in the Buntok town which is administratively a capital Dusun Selatan district as well the capital of South Barito regency, Central Kalimantan Province. Flooding always being yearly problematic disaster significantly happens, this has an impact on social aspects, but particularly impact on infrastructure development problems. Geological investigations should be conducted by means of geological mapping with analysis of geomorphology and hydrology as well. Based on the investigation it was found that the Buntok town is situated by young sediment fraction predominantly fine grain. In addition, from the manual analysis of coring obtained multiple layers that show the ancient flood sediment. Geomorphological analysis shows the city area Buntok is situated in the Flood Plain landform unit on Barito drainage basin (DAS) with an average elevation of 1-2 meters above sea level. As well as on the analysis of aerial photographs shows the presence of ancient Barito river flow patterns that head to giving area. Based on a series of investigations it is known that the study area is currently included in the flood-prone area with high intensity that the relocation of the urban area to a safer area is assumedly needed. Keyword: study environmental geology, flood disaster mitigation, buntok town, barito drainage basin

Daerah penelitian berada di kota Buntok secara administratif merupakan ibukota kecamatan Dusun Selatan sekaligus ibukota Kabupaten Barito Selatan, Provinsi Kalimantan Tengah. Daerah penilitian sering mengalami bencana banjir yang cukup signifikan, selain berdampak pada sosial tetapi sering berdampak pada permasalahan pembangunan infrastruktur. Maka perlu dilakukan penyelidikan geologi dengan pemetaan geologi serta analisis geomorfologi serta hidrologi dimana data menunjukan kota Buntok disusun oleh endapan muda dengan fraksi butir dominan halus. Selain itu juga dalam analisis manual coring didapatkan beberapa lapisan menunjukan endapan banjir purba. Selain itu analisis geomorfologi menunjukan wilayah kota Buntok termasuk dalam unit bentuklahan Dataran Banjir pada Daerah Aliran Sungai (DAS) Barito dengan elevasi rata-rata 1-2 mdpl serta dari analisis foto udara menunjukan adanya pola aliran purba sungai Barito yang mengarah kewilayah kota. Sehingga data tersebut menunjukan bahwa kawasan kota saat ini memiliki resiko kawasan banjir yang sangat besar sehingga perlua danya relokasi wilayah perkotaan kekawasan yang lebih aman. Kata kunci: kajian geologi lingkungan, mitigasi banjir, kota buntok, daerah aliran sungai barito

Carbonate rocks occur in isolated forms in the Volta Basin and each isolated occurrence is of such a quantity that inspires a sedimentological and geochemical study. This will allow proper evaluation of these significant geo-resources in terms of their usage for industrial purposes. Therefore, this study characterizes the northeastern carbonate rocks of the Volta Basin based on their field relations, sedimentary features, and geochemistry of fifteen (15) samples using X-Ray Fluorescence (XRF) analytical method. The suitability of the carbonate rocks for industrial usage has also been elucidated. The geochemical results show close variations as; SiO2 (12.9 - 17.4% with an average of 13.6%), MgO (15.2 - 17.4% with an average of 16.3%), CaO (24.7 - 27.2% with an average of 26.2%), CaCO3 (44.1 - 48.5% with an average of 44.7%), Al2O3 (0.7 - 1.7% with an average of 0.9%), and Fe2O3 (0.5 - 0.7% with an average of 0.6%). MnO, K2O, TiO, P2O5 and SO3 were recorded in trace quantities. The carbonates of the northeastern Nalerigu – Gbandaa areas of the Oti/Pendjari Group, define four (4) classes of facies with a dominant lacustrine to deep marine environment controlled by high seawater evaporation under a moderate saline water regime. The geochemical results indicate the dominance of dolomitic limestone carbonate rocks with Ca/Mg ratios ranging from 1.47 to 1.76. The study also reveals that the prevailing amount of CaO, CaCO3 and SiO2 supports their suitability for industrial production of natural cement. The carbonate rocks in the Volta Basin can be used as raw materials for dimension stones and other constructional grades for roads based on their silica content.
… Read more

The tectono-sedimentary evolution of asymmetric extensional systems driven by the activity of major normal faults or detachments associated with footwall exhumation is often characterized by a sequence of slower, faster, and ultimately again slower subsidence rates in the center of hanging wall half-grabens during their synkinematic and postkinematic evolution. We have studied this specific evolution by the means of 3-D stratigraphic numerical modeling that accounts for the variability of the sediment and water flux combined with climatic and sea level variations, and sediment compaction. The model setup is constrained by observations from the Pannonian back-arc basin of central Europe. Our modeling predicts the formation of low-order tectonic and higher-order sea level and climate-driven transgressive-regressive sedimentary cycles. Furthermore, we model and analyze the autocyclic nature of the depositional systems. Retrograding-prograding cycles are visible on the proximal flank of the half-grabens by their different spatial and temporal expressions, while depocenters record large water depth variations linked to the specific and episodic activity of normal faults and their migration with time. The application to a system of multiple half-grabens in the Pannonian Basin, which are activated in different locations, at different times and with different kinematics, demonstrates a complex interplay between direct sediment sourcing and the sediments' ability to bypass trapping subbasins and paleo-reliefs created by eroded footwalls. Plain Language Summary The formation and evolution of sedimentary basins is of prime interest as they record different Earth processes. The understanding of rifting mechanics and associated evolution of extensional sedimentary basins is also important for the assessment of their potential for georesources including freshwater. The spatial and temporal variabilities of vertical movements in asymmetric extensional systems control landscape evolution coupled to sedimentary and climatic processes. This paper aims to quantify the effect of tectonics and climatic variations on the overall architecture of such basins. Our numerical modeling demonstrates the low-order tectonic and higher-order sea level and climate-driven influence on the sedimentary transport routes and overall architecture. The application of our model in the Pannonian Basin of central Europe shows how tectonic inheritance control sedimentary transport routes.

Estudio del fenómeno del crushing en el ensayo de compactación de un proctor normal aplicado al terreno ubicado al NW del Centro Comercial Guatapurí... 60 Estudio del fenómeno del crushing en el ensayo de compacta-ción de un proctor normal aplicado al terreno ubicado al NW del Centro Comercial Guatapurí en Valledupar (Cesar) RESUMEN En la ejecución de obras civiles, es necesario realizar procesos de compactación del terreno para aumentar su resistencia a grandes presiones y disminuir así su capacidad de deformación donde se pueda generar el fenómeno del crushing, muy común en obras civiles, pero a su vez poco evaluado; el crushing, ocurre cuando las partículas del suelo se agrietan o se disgregan al soportar altas presiones. Se plantea estudiar el fenómeno del crushing en el terreno ubicado al NW del Centro Comercial Guatapurí en Valledupar (Cesar), con base a muestreos tomados a profundidades mayores a un metro, en cantidades aproximadas a 30 kg de suelos, empleándose el método C establecido por la norma I.N.V.E-141-07. Resultando un aumento significativo en la densidad máxima del suelo de 2,23 lb/ft2 y una disminución en la humedad óptima del 0,2 %, concluyendo que los suelos tienden a mostrar diferencia en las resistencias finales significativas. Es de esperar que la energía aplicada en la particulación seca, se gaste en gran parte al romper la estructura inicial de suelo, disgregándolos, sin lograr acomodamiento, por lo que al aplicar mayor humedad se logra distribuciones más uniformes de agua en los grumos. ABSTRACT In the execution of civil works, it is necessary to carry out compaction processes of the land to increase its resistance to high pressures and thus diminish its deformation capacity where the crushing phenomenon can be generated, very common in civil works but at the same time poorly evaluated; Crushing occurs when soil particles crack or disintegrate when bearing high pressures. It is proposed to study the phenomenon of crushing in the land located NW of the Commercial Center Guatapurí in Valledupar (Cesar), based on samples taken at depths greater than one meter, in approximate quantities to 30 kg of soil, using method C established by the standard INVE-141-07. Resulting in a significant increase in maximum soil density of 2.23 lb / ft2 and a decrease in optimum humidity of 0.2%, concluding that soils tend to show difference in significant final resistances. It is expected that the energy applied in the dry particulate will be spent to a large extent by breaking the initial structure of the soil, disintegrating them, without achieving accommodation, so that by applying greater humidity, more uniform water distributions are obtained in the lumps.

A crevasse is a geomorphological unit that consists of channel, bar, and splay deposits that form at a breach in the natural levee of a river, extending into the flood basin. They are common features in river delta and tidal landscapes where they form relatively highly elevated elements in otherwise low-lying flood basins. Hence, crevasses have an effect on sediment distribution within deltas and tidal landscapes.

So far, research on crevasses is generally limited to single crevasse case-studies in fluvial settings. Due to the focus on the effects of fluvial boundary conditions, there is a knowledge gap in the understanding of the effects of tidal boundary conditions. Therefore, the objective of this thesis is to assess the effect of tidal and fluvial boundary conditions, their interplay, and the initial flood basin conditions on the formation, evolution, and morphology of crevasses in the fluvial-tidal realm.

To address the objective, the Old Rhine system was used as a case study. The Old Rhine is a former main branch of the Rhine in the Western part of the Rhine-Meuse delta in the Netherlands. Multiple abandoned crevasses are well-preserved and its palaeogeographic development and changes in boundary conditions have been generally well reconstructed. The sedimentary build-up of four long crevasses was reconstructed based on borehole data of hand-augered corings. Lithogenetic cross-sections of each crevasse were constructed. Archaeological data were used in conjunction with the crevasse stratigraphy to get an indication of crevasse ages. Hence, three crevasse phases of the Old Rhine were identified. Their timing was compared to changes in boundary conditions and flood basin configuration of the Old Rhine to infer the effect of these changes on crevasse formation and evolution.

It was found that with regular tidal flushing of the crevasse throats (i.e. the initial natural levee breach) due to water level fluctuations induced by the tidal backwater effect, more crevasses can be formed by preventing crevasse healing. As such, regular tidal flushing facilitates crevasse evolution and progradation. When the tidal backwater effect decreased in the Old Rhine due to gradual closure of the estuary, the number of active crevasses decreased. This occurred because of the abandonment of existing crevasses on one hand and a decrease in the formation and establishment of new crevasses on the other as infilling of the crevasse throats was no longer or to an increasingly lesser extent prevented.

Flood events cause the initial natural levee breach which starts the crevasse formation. Subsequent flood events cause crevasse maturation and progradation, given that filling-in of the crevasse throat is prevented by regular flushing by the tidal backwater effect. Periods with a high frequency of flood events coincide with phases of increased crevasse formation and extensive progradation. Periods with a decreased frequency of flood events compared to a preceding high frequency period show a decrease in number of crevasses formed and a cease of crevasse progradation. Storm surge events probably have the same effect on crevasses as flood events, but the lack of a storm surge record for the Old Rhine estuary prevents any definitive statements about their effect.

Pre-existing channels, in the case of the Old Rhine peat drainage channels draining the raised bogs in the flood basins, can be intercepted by progradating crevasses. Hence, hybrid crevasse-peat drainage channels are formed. Such channels can still function as drainage channels of the raised bogs after a decrease or cease of morphodynamic crevasse activity due to a decrease in the tidal backwater effect, in the flood frequency or both. In the case of the Old Rhine, the three most upstream located crevasses in this study were formed as hybrid crevasse-peat drainage channels.

The outcomes presented in this thesis increase the understanding of the formation and maturation of crevasses in the fluvial-tidal realm of lowland river systems. They show that changes in both upstream as well as downstream boundary conditions affect the potential of crevasse formation and maturation. The presence of raised bogs in the flood basins and associated peat drainage channels can lead to the formation of hybrid crevasse-peat drainage channels.

These outcomes have implications for the archaeology of the Old Rhine area and future natural land-building projects in deltas. The three identified crevasse phases aid archaeologists to estimate the archaeological expectation of crevasse deposits in the Old Rhine area. Crevasses could be used in natural land-building projects to provide sediment to vulnerable flood basins to match (relative) sea level rise rates. Whether crevasse sedimentation rates would be high enough cannot be concluded based on the outcomes of this thesis. Implementation of crevasses for natural land-building projects would require that enough fluvial or marine sediment is available, sufficient vegetation cover is present to trap sediment efficiently, and flood events and storm surges are allowed to flood the flood basins.

Riprendiamo per un attimo la figura 22 del primo capitolo. Illustra un bacino con uno sversamento che tende a generare una nuova morena più a valle, secondo questo schema, la nuova morena può apparire come una goccia esilmente collegata al bacino di origine ma anche semplicemente come un semicerchio. Questo a seconda della rapidità con la quale il ghiaccio fuoriuscito può procedere. La quantità del flusso di alimentazione può variare la dimensione del canale di collegamento. Il rapporto tra la quantità di alimentazione e la capacità del nuovo ambiente di fondere tale afflusso determinerà invece la lunghezza del nuovo ramo. Punta Martin, dalla quale si osserva bene l'ambiente intorno al Turchino è situata in un punto critico di confronto tra un ghiacciaio ed il mare. Il primo è potente poiché riuscito a farsi largo in pianura Padana ed a riempirla fino al livello di metri 500. Il secondo però non è da meno: riesce a contrapporre alla corrente fredda costituente il ghiacciaio una corrente calda molto attiva che ne contrasta l'avanzata. Si crea quindi un punto di equilibrio piuttosto stabile dove tendono a formarsi morene terminali piuttosto evidenti: il Turchino e Punta Martin, appunto. Questa catena si trova in cima alla valle Stura. Sbarra la strada alla valle verso il mare ed obbliga l'omonimo torrente a rivolgere il proprio corso verso nord verso il bacino padano. Si, il ghiacciaio si scioglie e lascia al proprio posto degli esili corsi d'acqua che seguono percorsi improbabili, quasi beffardi per uno studioso che si affida all'ipotesi erosiva. Ma qui si sta valutando un ipotesi opposta: quella costruttiva. Qui troviamo questa piccola catena montuosa. Secondo me formata da un ghiacciaio. Vediamo se ci sono altri indizi. Un ghiacciaio tenderà talvolta a traboccare. Questa catena dovrebbe presentare delle discontinuità. In prossimità delle stesse si dovrebbero trovare tracce di scorrimento. Figura 1: Catena del Turchino vista da punta Martin