scholarly journals Characterization of a glacial paleo-outburst flood using high-resolution 3-D seismic data: Bjørnelva River Valley, SW Barents Sea

2021 ◽  
pp. 1-17
Author(s):  
B. Bellwald ◽  
S. Planke ◽  
S. Polteau ◽  
N. Lebedeva-Ivanova ◽  
J.I. Faleide ◽  
...  
Keyword(s):  
Seismic Data ◽  
Barents Sea ◽  
Ice Sheets ◽  
River System ◽  
High Energy ◽  
River Valley ◽  
Coarse Grained ◽  
Early Pleistocene ◽  
Braided River ◽  
River Systems

Abstract Proglacial braided river systems discharge large volumes of meltwater from ice sheets and transport coarse-grained sediments from the glaciated areas to the oceans. Here, we test the hypothesis if high-energy hydrological events can leave distinctive signatures in the sedimentary record of braided river systems. We characterize the morphology and infer a mode of formation of a 25 km long and 1–3 km wide Early Pleistocene incised valley recently imaged in 3-D seismic data in the Hoop area, SW Barents Sea. The fluvial system, named Bjørnelva River Valley, carved 20 m deep channels into Lower Cretaceous bedrock at a glacial paleo-surface and deposited 28 channel bars along a paleo-slope gradient of ~0.64 m km−1. The landform morphologies and position relative to the paleo-surface support that Bjørnelva River Valley was formed in the proglacial domain of the Barents Sea Ice Sheet. Based on valley width and valley depth, we suggest that Bjørnelva River Valley represents a braided river system fed by violent outburst floods from a glacial lake, with estimated outburst discharges of ~160 000 m3 s−1. The morphological configuration of Bjørnelva River Valley can inform geohazard assessments in areas at risk of outburst flooding today and is an analogue for landscapes evolving in areas currently covered by the Greenland and Antarctic ice sheets.

scholarly journals Braided-river and hyperconcentrated-flow deposits from the Carboniferous of the Lublin Basin (SE Poland) – a sedimentological study of core data

Geologos ◽  
2012 ◽  
Vol 18 (3) ◽  
pp. 135-161 ◽  
Author(s):  
Maria I. Waksmundzka
Keyword(s):  
Source Area ◽  
High Energy ◽  
Coarse Grained ◽  
Type I ◽  
Braided River ◽  
River Channels ◽  
Fine Grained ◽  
Braided Rivers ◽  
Base Level ◽  
Se Poland

Abstract Fining-upwards cyclothems found in five boreholes in the Carboniferous (Lower Bashkirian) of the Lublin Basin were analysed sedimentologically. It was established that the cyclothems represent fluvial deposits, and the lithofacies were grouped into lithofacies associations. Most lithofacies associations represent three types of sand-bed braided rivers: (1) high-energy, (2) deep and (3) distal sheetflood-affected. Other associations represent hyperconcentrated flows. Both coarse-grained (type I) and fine-grained (types IIa and IIb) occur among the fining-upward cyclothems. The formation of most thick cyclothems was related mainly to allocyclic factors, i.e. a decrease in the river’s gradient. The thickest fining-upward cyclothems are characteristic of hyperconcentrated flows and braided-river channels. The aggradation ratios were commonly high. During the early Namurian C and early Westphalian A (Early Bashkirian), the eastern part of the Lublin Basin was located close to the source area. The sedimentary succession developed due to a transition from high-energy braidedrivers and hyperconcentrated flows to lower-energy braided rivers, controlled by a rise of the regional base level.

scholarly journals Facies architecture of the fluvial Missão Velha Formation (Late Jurassic–Early Cretaceous), Araripe Basin, Northeast Brazil: paleogeographic and tectonic implications

2017 ◽  
Vol 67 (4) ◽  
pp. 515-545 ◽  
Author(s):  
Gelson Luís Fambrini ◽  
Virgínio Henrique M.L. Neumann ◽  
José Acioli B. Menezes-Filho ◽  
Wellington F. Da Silva-Filho ◽  
Édison Vicente De Oliveira
Keyword(s):  
Sand Dunes ◽  
High Energy ◽  
Coarse Grained ◽  
Dispersion Pattern ◽  
Northeast Brazil ◽  
River Systems ◽  
Alluvial Deposits ◽  
Architectural Elements ◽  
Overbank Flow ◽  
Facies Associations

Abstract Sedimentological analysis of the Missão Velha Formation (Araripe Basin, northeast Brazil) is the aim of this paper through detailed facies analysis, architectural elements, depositional systems and paleocurrent data. The main facies recognized were: (i) coarse-grained conglomeratic sandstones, locally pebbly conglomerates, with abundant silicified fossil trunks and several large-to-medium trough cross-stratifications and predominantly lenticular geometry; (ii) lenticular coarse-to-medium sandstones with some granules, abundant silicified fossil wood, and large-to-medium trough cross-stratifications, cut-and fill features and mud drapes on the foresets of cross-strata, (iii) poorly sorted medium-grained sandstones with sparse pebbles and with horizontal stratification, (iv) fine to very fine silty sandstones, laminated, interlayered with (v) decimetric muddy layers with horizontal lamination and climbing-ripple cross-lamination. Nine architectural elements were recognized: CH: Channels, GB: Gravel bars and bed forms, SB: Sand bars and bedforms, SB (p): sand bedform with planar cross-stratification, OF: Overbank flow, DA: Downstream-accretion macroforms, LS: Laminated sandsheet, LA: Lateral-accretion macroforms and FF: Floodplain fines. The lithofacies types and facies associations were interpreted as having been generated by alluvial systems characterized by (i) high energy perennial braided river systems and (ii) ephemeral river systems. Aeolian sand dunes and sand sheets generated by the reworking of braided alluvial deposits can also occur. The paleocurrent measurements show a main dispersion pattern to S, SE and SW, and another to NE/E. These features imply a paleodrainage flowing into the basins of the Recôncavo-Tucano-Jatobá.

scholarly journals Sedimentation style of a Pleistocene kame terrace from the Western Sudety Mountains, S Poland

Geologos ◽  
2010 ◽  
Vol 16 (2) ◽  
pp. 101-110 ◽  
Author(s):  
Małgorzata Pisarska-Jamroży ◽  
Katarzyna Machowiak ◽  
Dariusz Krzyszkowski
Keyword(s):  
Ice Sheet ◽  
River System ◽  
High Energy ◽  
Braided River ◽  
Braided Rivers ◽  
Mountain Valley ◽  
Sedimentary Succession ◽  
Sudety Mountains ◽  
S Poland ◽  
Lithofacies Association

Sedimentation style of a Pleistocene kame terrace from the Western Sudety Mountains, S PolandThe depositional conditions of kame terraces in a mountain valley were analysed sedimentologically and petrologically through a series of kame terraces in the Rudawy Janowickie mountains. The kame terraces comprise five lithofacies associations. Lithofacies association GRt, Sp originates from deposition in the high-energy, deep gravel-bed channel of a braided river. Lithofacies association GC represents a washed out glacial till. Probably a thin layer of till was washed out by sandy braided rivers (Sp). The fourth association (Fh, Fm) indicates a shallow and quite small glaciomarginal lake. The last association (GRt, GRp) indicates the return of deposition in a sandy-bed braided channel. The petrography of the Janowice Wiekie pit and measurements of cross-stratified beds indicate a palaeocurrent direction from N to S. The Janowice Wielkie sedimentary succession accumulated most probably during the Saalian (Odranian, Saale I, Drenthe) as the first phase of ice-sheet melting, because the kame terrace under study is the highest one, 25-27 m above the Bóbr river level. The deposits under study are dominated by local components. The proglacial streams flowed along the margin of the ice sheet and deposited the kame terrace. The majority of the sedimentary succession was deposited in a confined braided-river system in quite deep channels.

scholarly journals Badenian (middle Miocene) continental paleoenvironment in the Novohrad–Nógrád Basin (Central Paratethys): a volcano-sedimentary record from the Páris-patak Valley in Hungary

2021 ◽  
Vol 151 (2) ◽  
pp. 159
Author(s):  
Emese M. Bordy ◽  
Orsolya Sztanó
Keyword(s):  
Grain Size ◽  
Middle Miocene ◽  
River System ◽  
High Energy ◽  
Volcanic Field ◽  
Bedload Transport ◽  
Coarse Grained ◽  
Facies Association ◽  
Cross Bedding ◽  
Facies Associations

Two levels of volcaniclastics, comprising conglomerates, sandstones and mudstones, are interbedded with upper middle Miocene (upper Badenian) andesite pyroclastics near the Hungarian-Slovakian border in the distal region of the Central Slovakian Neogene Volcanic Field. Based on the field sedimentological investigations, the facies of the volcaniclastics (e.g., lateral and vertical grain size changes, sedimentary structures, textures, clast composition), their geometry and field relationships are documented herein with the aim of reconstructing the depositional environment. The silica-cemented volcaniclastics are mostly andesite clasts with only ~ 5% being granitoid, quarzitic, and tuff clasts as well as charred fossil wood fragments. The coarse-grained facies association includes crudely stratified, tabular or lenticular, clast-supported pebble-cobble conglomerates with erosive basal surfaces, b-axis imbrication, alternating with sets of cross-bedding. The fine-grained facies association comprises cross-bedded pebbly to medium-grained sandstone and lenses of tuffaceous clayey siltstone with rare horizontal lamination and water-escape structures. Rip-up mudstone clasts, with diametre up to 1 m, are present in both facies associations, revealing the co-existence of abandoned silty palaeo-channel plugs. Facies associations are arranged in several 0.5-4-m-thick, fining-upwards successions that likely formed in shallow channels as downstream- to laterally accreting longitudinal bars, extensive gravel sheets and bars that migrated in peak flow during floods. Palaeocurrent indicators (i.e., clast imbrication, direction of planar cross-bedding, orientation of petrified wood logs) show bedload transport by traction currents, initially towards ~S, and later towards ~W. Intermittently debris flows also occurred. Cross-bedded sandstones formed as in-channel transverse bars during medium/low discharge. Variation of grain size shows frequent discharge fluctuations during permanently wet conditions in the late Badenian. The 4-5-m-deep, low-sinuosity channels were part of a high-energy, gravel-bed braided-river system on the south-eastern foothills of the Lysec palaeo-volcano. Here, pyroclastics were reworked and redeposited as volcaniclastics during inter-eruption, high-discharge episodes.

Depositional Placer Accumulations in Coarse-Grained Alluvial Braided River Systems

2003 ◽  
Vol 98 (5) ◽  
pp. 985-1001 ◽  
Author(s):  
J. P. Burton ◽  
Philip Fralick
Keyword(s):  
Coarse Grained ◽  
Braided River ◽  
River Systems

Extreme wave events recorded in sedimentary archives of the Geropotamos River (north-central Crete, Greece)

2019 ◽  
Vol 62 (2) ◽  
pp. 63-100
Author(s):  
Vera Werner ◽  
Kalliopi Baika ◽  
Anastasia Tzigounaki ◽  
Klaus Reicherter ◽  
Ioannis Papanikolaou ◽  
...  
Keyword(s):  
Bronze Age ◽  
Sedimentary Environment ◽  
River Mouth ◽  
High Energy ◽  
River Valley ◽  
Coarse Grained ◽  
Northern Coast ◽  
Natural Setting ◽  
Extreme Wave ◽  
Cretan Sea

Recent tsunami events have shown that tsunamis may propagate far inland by entering rivers mouths and may cause massive damage along the river banks. However, so far, only a few studies have been conducted such a search for studying tsunami signals in incised valley systems along the Mediterranean coasts although the tsunami hazard is high. The island of Crete is known to have been affected several times by strong tsunamis, e. g., by the AD 365 and the Late Bronze Age (LBA) Santorini tsunamis. The narrow Geropotamos River valley, distinctly incised into local bedrock and located at the northern coast of Crete and fully exposed to the Cretan Sea, was selected as a promising natural setting to search for palaeotsunami signatures in fluvial sedimentary archives. Based on a multi-electrode geoelectrical survey and a set of sediment cores, we investigated the event-geochronostratigraphic record of both the Geropotamos River mouth area and the river valley ca. 1 km upstream by means of sedimentological, geo-chemical, geochronological, geomorphological, and micropalaeontological methods. The sedimentary environment towards the present-day river mouth is dominated by (fluvio-)lagoonal muds since the mid- Holocene. These lagoonal sediments are intersected by six coarse-grained sand layers each representing an extreme wave event (EWE). EWE layers are up to several decimetres thick and are characterized by an allochthonous foraminiferal assemblage comprising shallow marine to open marine species. Also ca. 1 km further upstream, the sedimentary record revealed grain size and microfossil evidence of two high-energy events showing a clear marine imprint. Based on this, we suggest inundation from the seaside that reached minimum 1 km inland and left EWE signatures in a presently inactive external bank position of the Geropotamos River. Considering the sedimentary characteristics, the local wind and wave climate of the Cretan Sea, and the overall geomorphological setting, we interpret these EWE layers as tsunami- related. A major hiatus identified in the Geropotamos River mouth sediments seems to be related to the LBA Santorini tsunami as can be inferred based on local age-depth relations. The LBA tsunami is known to have severely hit the northern coast of Crete. However, the hiatus may also reflect changes in the subsidence rate and the local accommodation space architecture. The youngest EWE signal in the Geropotamos River archive appears to have been caused by the AD 365 tsunami event. Candidate deposits for both tsunami deposits were identified ca. 1 km further inland. Evidence of EWE impact documents channelling and acceleration effects of intruding water masses caused by the narrow and steeply incised Geropotamos River valley in an upstream direction. Further geochronological studies based on OSL dating are necessary for a reliable age control of these EWE candidate layers.

Lithostratigraphy of the Palaeoproterozoic Hekpoort Formation (Pretoria Group, Transvaal Supergroup), South Africa

2020 ◽  
Vol 123 (4) ◽  
pp. 655-668
Author(s):  
N. Lenhardt ◽  
W. Altermann ◽  
F. Humbert ◽  
M. de Kock
Keyword(s):  
South Africa ◽  
Bushveld Complex ◽  
Sedimentary Rocks ◽  
Type Locality ◽  
Large Igneous Province ◽  
Braided River ◽  
River Systems ◽  
The West ◽  
Igneous Province ◽  
Transvaal Supergroup

Abstract The Palaeoproterozoic Hekpoort Formation of the Pretoria Group is a lava-dominated unit that has a basin-wide extent throughout the Transvaal sub-basin of South Africa. Additional correlative units may be present in the Kanye sub-basin of Botswana. The key characteristic of the formation is its general geochemical uniformity. Volcaniclastic and other sedimentary rocks are relatively rare throughout the succession but may be dominant in some locations. Hekpoort Formation outcrops are sporadic throughout the basin and mostly occur in the form of gentle hills and valleys, mainly encircling Archaean domes and the Palaeoproterozoic Bushveld Complex (BC). The unit is exposed in the western Pretoria Group basin, sitting unconformably either on the Timeball Hill Formation or Boshoek Formation, which is lenticular there, and on top of the Boshoek Formation in the east of the basin. The unit is unconformably overlain by the Dwaalheuwel Formation. The type-locality for the Hekpoort Formation is the Hekpoort farm (504 IQ Hekpoort), ca. 60 km to the west-southwest of Pretoria. However, no stratotype has ever been proposed. A lectostratotype, i.e., the Mooikloof area in Pretoria East, that can be enhanced by two reference stratotypes are proposed herein. The Hekpoort Formation was deposited in a cratonic subaerial setting, forming a large igneous province (LIP) in which short-termed localised ponds and small braided river systems existed. It therefore forms one of the major Palaeoproterozoic magmatic events on the Kaapvaal Craton.

Stratigraphy and palaeoenvironments of the Red Crag and Norwich Crag formations between Aldeburgh and Sizewell, Suffolk, England

1988 ◽  
Vol 322 (1210) ◽  
pp. 221-272 ◽  
Keyword(s):  
Amino Acid ◽  
High Energy ◽  
Coarse Grained ◽  
Core Material ◽  
Stage System ◽  
Pollen And Spores ◽  
Shallow Marine Sediments ◽  
Amino Acid Chronology ◽  
Tectonic Origin ◽  
Borehole Core

This study uses a variety of criteria to examine short-range correlation within the Crag deposits in order to assess the validity of longer-range correlations within the British Pleistocene stage system. To this end, six rotary cored boreholes spaced at 0.5-1.0 km intervals were drilled along a north-south-aligned traverse between Aldeburgh and Sizewell, Suffolk. These show that the thick Red/Norwich Crag sequence is confined to a deep, sharply bounded basin, which is of probable erosional rather than tectonic origin. The undisturbed borehole core material enabled an assessment of the limits of stratigraphic resolution within these dominantly high-energy, shallow marine sediments to be made. Subdivision of the sequence was done on the basis of lithostratigraphical and biostratigraphical (foraminifera, pollen and spores, dinoflagellate cysts, and molluscs) criteria; chronostratigraphical methods (palaeomagnetism and amino acid chronology) were also applied. The various subdivisions indicated by each of these disciplines were in large part consistent, demonstrating that valid stratigraphic units had been identified. Only amino acid chronology did not indicate any obvious subdivision of the sequence. Three lithostratigraphical units were recognized within the thick Crag sequence. The lowest unit (AS-Lith 1) consists of coarse shelly sands interbedded with thinly laminated muds and fine sands. The middle unit (AS-Lith 2) consists of fine- to coarse-grained shelly sands arranged in two coarsening-upwards cycles. Units AS-Lith 1 and AS-Lith 2 are correlated on a lithostratigraphical basis with the Red Crag Formation of the adjacent Aldeburgh-Orford area to the south and are named the Sizewell Member and the Thorpeness Member respectively. The uppermost unit (AS-Lith 3) comprises fine- to medium-grained, well-sorted sands; it correlates with the Chillesford Sand Member of the Norwich Crag Formation of the adjacent Aldeburgh-Orford area. The Sizewell Member of the Red Crag Formation is normally magnetized and palaeontologically distinctive. The pollen, foraminifera and dinoflagellate assemblages firmly establish it as Pre-Ludhamian in age, and probably equivalent to an interval within the Reuverian C to Praetiglian Stages of the Netherlands. The Thorpeness Member of the Red Crag Formation is less easy to place within the British Pleistocene stage system. It is reverse magnetized, at least in part, and foraminifera assemblages suggest possible correlation with the Ludhamian Stage. No identifiable pollen or dinoflagellate assemblages were obtained. The Chillesford Sand Member of the Norwich Crag Formation is largely unfossiliferous but the borehole material has yielded a single pollen spectrum that suggests correlation with the Bramertonian Stage.

Chutes and ladders and other games we play with rivers. II. Simulated effects of translocation on white sturgeon

2006 ◽  
Vol 63 (1) ◽  
pp. 176-185 ◽  
Author(s):  
Henriette I Jager
Keyword(s):  
Fish Species ◽  
Simulation Study ◽  
River System ◽  
Genetic Effects ◽  
White Sturgeon ◽  
Acipenser Transmontanus ◽  
River Systems ◽  
Short Segment ◽  
River Fragmentation ◽  
Demographic Effects

Restoring connectivity is viewed as an important recovery option for fish species adversely affected by river fragmentation. This simulation study quantified the genetic and demographic effects of translocation on metapopulations of white sturgeon (Acipenser transmontanus) inhabiting a series of long (source) and short (sink) river segments. Genetic effects were predictable; upstream translocations increased introgression and downstream translocations had no effect. Demographic results suggest that indiscriminant efforts to reconnect populations may do more harm than good. Simulated river systems with high interspersion of long and short segments and a long segment far upstream tended to benefit most from translocation, but only when narrow screening or downstream passage was also provided below the river segment receiving fish. When combined with narrow screening, upstream translocation to a long segment subsidizing several downstream short segments produced the best results. Downstream passage outperformed narrow screening only when the translocation recipient was a short segment in a river system with low interspersion and no long, upstream river segment. This model-based evaluation of reconnection options has helped to refine ideas about restoring populations in fragmented rivers by predicting which options benefit riverine metapopulations as a whole.

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