Earth and Planetary Sciences › Earth-Surface Processes

Geological formations and processes

Works Count: 83580

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This cluster of papers explores the various processes and mechanisms involved in sedimentation, including fluvial systems, sequence stratigraphy, turbidity currents, submarine landslides, delta evolution, and subaqueous sediment density flows. It also delves into the tectonic and Holocene development aspects influencing sedimentary deposition in Earth's geological history.

Keywords

Sedimentation; Fluvial Systems; Sequence Stratigraphy; Turbidity Currents; Submarine Landslides; Delta Evolution; Sedimentary Deposition; Tectonics; Subaqueous Sediment Density Flows; Holocene Development

Seismic Geomorphology and Stratigraphy of Depositional Elements in Deep-Water Settings

2003-05-01

Henry W. Posamentier , V. Kolla

Analyses of 3-D seismic data in predominantly basin-floor settings offshore Indonesia, Nigeria, and the Gulf of Mexico, reveal the extensive presence of gravity-flow depositional elements. Five key elements were observed: … Analyses of 3-D seismic data in predominantly basin-floor settings offshore Indonesia, Nigeria, and the Gulf of Mexico, reveal the extensive presence of gravity-flow depositional elements. Five key elements were observed: (1) turbidity-flow leveed channels, (2) channel-overbank sediment waves and levees, (3) frontal splays or distributary-channel complexes, (4) crevasse-splay complexes, and (5) debris-flow channels, lobes, and sheets. Each depositional element displays a unique morphology and seismic expression. The reservoir architecture of each of these depositional elements is a function of the interaction between sedimentary process, sea-floor morphology, and sediment grain-size distribution. (1) Turbidity-flow leveed-channel widths range from greater than 3 km to less than 200 m. Sinuosity ranges from moderate to high, and channel meanders in most instances migrate down-system. The high-amplitude reflection character that commonly characterizes these features suggests the presence of sand within the channels. In some instances, high-sinuosity channels are associated with (2) channel-overbank sediment-wave development in proximal overbank levee settings, especially in association with outer channel bends. These sediment waves reach heights of 20 m and spacings of 2-3 km. The crests of these sediment waves are oriented normal to the inferred transport direction of turbidity flows, and the waves have migrated in an up-flow direction. Channel-margin levee thickness decreases systematically down-system. Where levee thickness can no longer be resolved seismically, high-sinuosity channels feed (3) frontal splays or low-sinuosity, distributary-channel complexes. Low-sinuosity distributary-channel complexes are expressed as lobate sheets up to 5-10 km wide and tens of kilometers long that extend to the distal edges of these systems. They likely comprise sheet-like sandstone units consisting of shallow channelized and associated sand-rich overbank deposits. Also observed are (4) crevasse-splay deposits, which form as a result of the breaching of levees, commonly at channel bends. Similar to frontal splays, but smaller in size, these deposits commonly are characterized by sheet-like turbidites. (5) Debris-flow deposits comprise low-sinuosity channel fills, narrow elongate lobes, and sheets and are characterized seismically by contorted, chaotic, low-amplitude reflection patterns. These deposits commonly overlie striated or grooved pavements that can be up to tens of kilometers long, 15 m deep, and 25 m wide. Where flows are unconfined, striation patterns suggest that divergent flow is common. Debris-flow deposits extend as far basinward as turbidites, and individual debris-flow units can reach 80 m in thickness and commonly are marked by steep edges. Transparent to chaotic seismic reflection character suggest that these deposits are mud-rich. Stratigraphically, deep-water basin-floor successions commonly are characterized by mass-transport deposits at the base, overlain by turbidite frontal-splay deposits and subsequently by leveed-channel deposits. Capping this succession is another mass-transport unit ultimately overlain and draped by condensed-section deposits. This succession can be related to a cycle of relative sea-level change and associated events at the corresponding shelf edge. Commonly, deposition of a deep-water sequence is initiated with the onset of relative sea-level fall and ends with subsequent rapid relative sea-level rise.

The geology of fluvial deposits: sedimentary facies, basin analysis, and petroleum geology

1996-12-01

Andrew D. Miall

Fluvial deposits represent the preserved record of one of the major nonmarine environments.They accumulate in large and small intermontane valleys, in the broad valleys of trunk rivers, in the wedges … Fluvial deposits represent the preserved record of one of the major nonmarine environments.They accumulate in large and small intermontane valleys, in the broad valleys of trunk rivers, in the wedges of alluvial fans flanking areas of uplift, in the outwash plains fronting melting glaciers, and in coastal plains.The nature of alluvial assemblages -their lithofacies composition, vertical stratigraphic record, and architecture -reflect an interplay of many processes, from the wandering of individual channels across a floodplain, to the long-term effects of uplift and subsidence.Fluvial deposits are a sensitive indicator of tectonic processes, and also carry subtle signatures of the climate at the time of deposition.They are the hosts for many petroleum and mineral deposits.This book is about all these subjects.The first part of the book, following a historical introduction, constructs the stratigraphic framework of fluvial deposits, step by step, starting with lithofacies, combining these into architectural elements and other facies associations, and then showing how these, in turn, combine to represent distinctive fluvial styles.Next, the discussion turns to problems of correlation and the building of large-scale stratigraphic frameworks.These basin-scale constructions form the basis for a discussion of causes and processes, including autogenic processes of channel shifting and cyclicity, and the larger questions of allogenic (tectonic, eustatic, and climatic) sedimentary controls and the development of our ideas about nonmarine sequence stratigraphy.The final chapters address issues of concern to petroleum geologists.The geometry of reservoirs is discussed, and primary reservoir heterogeneities are evaluated from the point of view of facies architecture and porosity-permeability characteristics.Lastly, the stratigraphic and tectonic distribution of petroleum reservoirs is analyzed, leading to a stratigraphic-tectonic classification of oil and gas fields in fluvial deposits, and a description of selected case examples.The book is intended for advanced students, researchers, and professionals.Extensive references have been made to the published literature, and hundreds of examples and diagrams have been provided.It is to be hoped that the methods and classifications proposed here will assist in future research work and resource production.

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Sedimentology of some Flysch deposits : a graphic approach to facies interpretation

1962-01-01

Arnold H. Bouma , Philip Henry Kuenen , Francis P. Shepard

Depositional Sedimentary Environments

1980-01-01

Hans‐Erich Reineck , Indra Bir Singh

Siliciclastic Sequence Stratigraphy in Well Logs, Cores, and Outcrops

1990-01-01

John C. Van Wagoner , R. M. Mitchum , K. M. Campion +1 more

Application of sequence-stratigraphic analysis depends on the recognition of a hierarchy of stratal units including beds, bedsets, parasequences, parasequence sets, and sequences bounded by chronostratigraphically significant surfaces of erosion, nondeposition, … Application of sequence-stratigraphic analysis depends on the recognition of a hierarchy of stratal units including beds, bedsets, parasequences, parasequence sets, and sequences bounded by chronostratigraphically significant surfaces of erosion, nondeposition, or their correlative surfaces. This method of stratigraphic analysis contrasts with the use of transgressive and regressive cycles of strata for regional correlation of time and facies. Transgressive and regressive cycles have been used for regional correlation for at least 50 years. Recently, proponents of transgressive and regressive cycles, referred to as T-R units, for regional correlation have included Ryer (1983), Busch and Rollins (1984), Busch et al. (1985), and Galloway (1989a). Galloway (1989a) introduced the “genetic stratigraphic sequence,” which is a regressive depositional unit bounded by transgressive surfaces. Although he did not define it specifically, he described it as “a package of sediments recording a significant episode of basin-margin outbuilding and basin filling, bounded by periods of widespread basin margin flooding.”

Subaqueous sediment density flows: Depositional processes and deposit types

2012-10-30

Peter J. Talling , Douglas G. Masson , E. J. Sumner +1 more

Abstract Submarine sediment density flows are one of the most important processes for moving sediment across our planet, yet they are extremely difficult to monitor directly. The speed of long … Abstract Submarine sediment density flows are one of the most important processes for moving sediment across our planet, yet they are extremely difficult to monitor directly. The speed of long run‐out submarine density flows has been measured directly in just five locations worldwide and their sediment concentration has never been measured directly. The only record of most density flows is their sediment deposit. This article summarizes the processes by which density flows deposit sediment and proposes a new single classification for the resulting types of deposit. Colloidal properties of fine cohesive mud ensure that mud deposition is complex, and large volumes of mud can sometimes pond or drain‐back for long distances into basinal lows. Deposition of ungraded mud (T E‐3 ) most probably finally results from en masse consolidation in relatively thin and dense flows, although initial size sorting of mud indicates earlier stages of dilute and expanded flow. Graded mud (T E‐2 ) and finely laminated mud (T E‐1 ) most probably result from floc settling at lower mud concentrations. Grain‐size breaks beneath mud intervals are commonplace, and record bypass of intermediate grain sizes due to colloidal mud behaviour. Planar‐laminated (T D ) and ripple cross‐laminated (T C ) non‐cohesive silt or fine sand is deposited by dilute flow, and the external deposit shape is consistent with previous models of spatial decelerating (dissipative) dilute flow. A grain‐size break beneath the ripple cross‐laminated (T C ) interval is common, and records a period of sediment reworking (sometimes into dunes) or bypass. Finely planar‐laminated sand can be deposited by low‐amplitude bed waves in dilute flow (T B‐1 ), but it is most likely to be deposited mainly by high‐concentration near‐bed layers beneath high‐density flows (T B‐2 ). More widely spaced planar lamination (T B‐3 ) occurs beneath massive clean sand (T A ), and is also formed by high‐density turbidity currents. High‐density turbidite deposits (T A , T B‐2 and T B‐3 ) have a tabular shape consistent with hindered settling, and are typically overlain by a more extensive drape of low‐density turbidite (T D and T C ,). This core and drape shape suggests that events sometimes comprise two distinct flow components. Massive clean sand is less commonly deposited en masse by liquefied debris flow (D CS ), in which case the clean sand is ungraded or has a patchy grain‐size texture. Clean‐sand debrites can extend for several tens of kilometres before pinching out abruptly. Up‐current transitions suggest that clean‐sand debris flows sometimes form via transformation from high‐density turbidity currents. Cohesive debris flows can deposit three types of ungraded muddy sand that may contain clasts. Thick cohesive debrites tend to occur in more proximal settings and extend from an initial slope failure. Thinner and highly mobile low‐strength cohesive debris flows produce extensive deposits restricted to distal areas. These low‐strength debris flows may contain clasts and travel long distances (D M‐2 ), or result from more local flow transformation due to turbulence damping by cohesive mud (D M‐1 ). Mapping of individual flow deposits (beds) emphasizes how a single event can contain several flow types, with transformations between flow types. Flow transformation may be from dilute to dense flow, as well as from dense to dilute flow. Flow state, deposit type and flow transformation are strongly dependent on the volume fraction of cohesive fine mud within a flow. Recent field observations show significant deviations from previous widely cited models, and many hypotheses linking flow type to deposit type are poorly tested. There is much still to learn about these remarkable flows.

Devonian eustatic fluctuations in Euramerica

1985-01-01

J. G. Johnson , Gilbert Klapper , Charles A. Sandberg

Research Article| May 01, 1985 Devonian eustatic fluctuations in Euramerica J. G. JOHNSON; J. G. JOHNSON 1Department of Geology, Oregon State University, Corvallis, Oregon 97331 Search for other works by … Research Article| May 01, 1985 Devonian eustatic fluctuations in Euramerica J. G. JOHNSON; J. G. JOHNSON 1Department of Geology, Oregon State University, Corvallis, Oregon 97331 Search for other works by this author on: GSW Google Scholar GILBERT KLAPPER; GILBERT KLAPPER 2Department of Geology, University of Iowa, Iowa City, Iowa 52242 Search for other works by this author on: GSW Google Scholar C. A. SANDBERG C. A. SANDBERG 3U.S. Geological Survey, M.S. 940, Federal Center, Denver, Colorado 80225 Search for other works by this author on: GSW Google Scholar GSA Bulletin (1985) 96 (5): 567–587. https://doi.org/10.1130/0016-7606(1985)96<567:DEFIE>2.0.CO;2 Article history first online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share MailTo Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation J. G. JOHNSON, GILBERT KLAPPER, C. A. SANDBERG; Devonian eustatic fluctuations in Euramerica. GSA Bulletin 1985;; 96 (5): 567–587. doi: https://doi.org/10.1130/0016-7606(1985)96<567:DEFIE>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract The Devonian System of Euramerica contains at least 14 transgressive-regressive (T-R) cycles of eustatic origin. These are separated into three groups (or depophases) and from Carboniferous cycles by three prominent regressions. Twelve post-Lochkovian T-R cycles are recognized, and they commonly appear to result from abrupt deepening events followed by prolonged upward shallowing. Deepening events in the western United States (especially Nevada), western Canada, New York, Belgium, and Germany have been dated in the standard conodont zonation and are demonstrably simultaneous in several or all five regions. This synchroneity indicates control by eustatic sea-level fluctuations rather than by local or regional epeirogeny. Facies shifts in shelf sedimentary successions are more reliable indicators of the timing of sea-level fluctuations than are strandline shifts in the cratonic interior, because the latter are more influenced by local epeirogeny. Strandline shifts are most useful in estimating the relative magnitude for sea-level fluctuations.Devonian facies progressions and the three prominent regressions are of a duration and an order of magnitude that could have been caused by episodes of growth and decay of Devonian oceanic ridge systems. The described T-R cycles could have formed in response to mid-plate thermal uplift and submarine volcanism. The latter process may have been a control on small-scale (1–5 m thick), upward-shallowing cycles within the major T-R cycles. Continental glaciation could have been a factor in sea-level fluctuations only in the Famennian and could not have been responsible for the Devonian facies progressions or the numerous T-R cycles.The Frasnian extinctions were apparently cumulative rather than due to a single calamity. Two rapid sea-level rises occurred just before, and one at, the Frasnian-Famennian boundary. It is probable that this series of deepening events reduced the size of shallow-shelf habitats, caused repeated anoxic conditions in basinal areas, and drowned the reef ecosystems that had sustained the immensely diverse Devonian benthos. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Determination of recent sedimentation rates in Lake Michigan using Pb-210 and Cs-137

1975-03-01

John A. Robbins , D.N. Edgington

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Water escape structures in coarse‐grained sediments

1975-05-01

Donald R. Lowe

ABSTRACT Three processes of water escape characterize the consolidation of silt‐, sand‐and gravel‐sized sediments. Seepage involves the slow upward movement of pore fluids within existing voids or rapid flow within … ABSTRACT Three processes of water escape characterize the consolidation of silt‐, sand‐and gravel‐sized sediments. Seepage involves the slow upward movement of pore fluids within existing voids or rapid flow within compact and confined sediments. Liquefaction is marked by the sudden breakdown of a metastable, loosely packed grain framework, the grains becoming temporarily suspended in the pore fluid and settling rapidly through the fluid until a grain‐supported structure is re‐established. Fluidization occurs when the drag exerted by moving pore fluids exceeds the effective weight of the grains; the particles are lifted, the grain framework destroyed, and the sediment strength reduced to nearly zero. Diagenetic sedimentary structures formed in direct response to processes of fluid escape are here termed water escape structures. Four main types of water escape structures form during the fluidization and liquefaction of sands: (1) soft‐sediment mixing bodies, (2) soft‐sedimsnt intrusions, (3) consolidation laminations, and (4) soft‐sediment folds. These structures represent both the direct rearrangement of sediment grains by escaping fluids and the deformation of hydroplastic, liquefied, or fluidized sediment in response to external stresses. Fundamental controls on sediment consolidation are exerted by the bulk sediment properties of grain size, packing, permeability, and strength, which together determine whether consolidation will occur and, if so the course it follows, and by external disturbances which act to trigger liquefaction and fluidization. The liquefaction and fluidization of natural sands usually accompanies the collapse of loosely packed cross‐bedded deposits. This collapse is commonly initiated by water forced into the units as underlying beds, especially muds and clays, consolidate. The consolidation of subjacent units is often triggered by the rapid deposition of the sand itself, although earthquakes or other disturbances are probably influential in some instances. Water escape structures most commonly form in fine‐ to medium‐grained sands deposited at high instantaneous and mean sedimentation rates; they are particularly abundant in cross‐laminated deposits but rare in units deposited under upper flow regime plane bed conditions. Their development is favoured by upward decreasing permeability within sedimentation units such as normally graded turbidites. They are especially common in sequences made up of alternating fine‐(clay and mud) and coarse‐grained (sand) units such as deep‐sea flysch prodelta, and, to a lesser extent, fluvial point bar, levee, and proximal overbank deposits.

Recent trends in the suspended sediment loads of the world's rivers

2003-06-02

D. E. Walling , Fang Duo

Tectono‐sedimentary evolution of active extensional basins

2000-09-01

Robert L. Gawthorpe , M. R. Leeder

We present conceptual models for the tectono‐sedimentary evolution of rift basins. Basin architecture depends upon a complex interaction between the three‐dimensional evolution of basin linkage through fault propagation, the evolution … We present conceptual models for the tectono‐sedimentary evolution of rift basins. Basin architecture depends upon a complex interaction between the three‐dimensional evolution of basin linkage through fault propagation, the evolution of drainage and drainage catchments and the effects of changes in climate and sea/lake level. In particular, the processes of fault propagation, growth, linkage and death are major tectonic controls on basin architecture. Current theoretical and experimental models of fault linkage and the direction of fault growth can be tested using observational evidence from the earliest stages of rift development. Basin linkage by burial or breaching of crossover basement ridges is the dominant process whereby hydrologically closed rifts evolve into open ones. Nontectonic effects arising from climate, sea or lake level change are responsible for major changes in basin‐scale sedimentation patterns. Major gaps in our understanding of rift basins remain because of current inadequacies in sediment, fault and landscape dating.

Fluvial Forms and Processes

1986-07-01

Richard A. Marston , David Knighton

Balanced cross sections

1969-08-01

Clinton D. A. Dahlstrom

Post-depositional concentric deformation produces no significant change in rock volume. Since bed thickness remains constant in concentric deformation, the surface area of a bed and its length in a cross-sectional … Post-depositional concentric deformation produces no significant change in rock volume. Since bed thickness remains constant in concentric deformation, the surface area of a bed and its length in a cross-sectional plane must also remain constant. Under these conditions, a simple test of the geometric validity of a cross section is to measure bed lengths at several horizons between reference lines located on the axial planes of major synclines or other areas of no interbed slip. These bed lengths must be consistent unless a discontinuity, like a décollement, intervenes. Consistency of bed length also requires consistency of shortening, whether by folding and (or) faulting, within one cross section and between adjacent cross sections.The number of possible cross-sectional explanations of a set of data is reduced by the fact that, in a specific geological environment, there is only a limited suite of structures which can exist. This imposes a set of local "ground rules" on interpretation. When these local restrictions are coupled with the geometric restrictions which follow from the law of conservation of volume, it is often possible to produce structural cross sections that have a better-than-normal chance of being right.The concept of consistency of shortening can be extrapolated to a mountain belt as a whole, thereby indicating the necessity for some kind of transfer mechanism wherein waning faults or folds are compensated by waxing en echelon features. These concepts are illustrated diagrammatically and by examples from the Alberta Foothills.

A review of the braided-river depositional environment

1977-05-01

Andrew D. Miall

Plate Tectonics and Geochemical Composition of Sandstones

1983-11-01

Mukul Bhatia

Sandstones of the Paleozoic turbidite sequences of eastern Australia show a large variation in their major element geochemistry, reflecting the distinct sedimentary provenance and tectonic setting of each suite. On … Sandstones of the Paleozoic turbidite sequences of eastern Australia show a large variation in their major element geochemistry, reflecting the distinct sedimentary provenance and tectonic setting of each suite. On the basis of bulk composition, five suites are discriminated: Tamworth, Hill End, Hodgkinson, Bendigo, and Cookman. A close correlation exists between the geochemical composition of sandstones and tectonic settings of sedimentary basins. The nature of the continental margin and oceanic basins can be deciphered on the basis of the major element composition of sandstones. The most discriminating parameters are and . In general, there is a progressive decrease in , and an increase in and in sandstones from oceanic island arc to continental island arc to active continental margins to passive margins. Oceanic island arc sandstones are characterized by the high abundance of , and low and ratios. The continental island arc type sandstones can be distinguished from the oceanic island arc type by their lower and , and higher and . The active continental margin type sandstones are characterized by low and . Passive margin type sandstones are generally enriched in and depleted in , CaO, and , suggesting their highly recycled and matured nature.

Geomorphic/Tectonic Control of Sediment Discharge to the Ocean: The Importance of Small Mountainous Rivers

1992-09-01

John D. Milliman , James P. M. Syvitski

Analysis of data from 280 rivers discharging to the ocean indicates that sediment loads/yields are a log-linear function of basin area and maximum elevation of the river basin. Other factors … Analysis of data from 280 rivers discharging to the ocean indicates that sediment loads/yields are a log-linear function of basin area and maximum elevation of the river basin. Other factors controlling sediment discharge (e.g., climate, runoff) appear to have secondary importance. A notable exception is the influence of human activity, climate, and geology on the rivers draining southern Asia and Oceania. Sediment fluxes from small mountainous rivers, many of which discharge directly onto active margins (e.g., western South and North America and most high-standing oceanic islands), have been greatly underestimated in previous global sediment budgets, perhaps by as much as a factor of three. In contrast, sediment fluxes to the ocean from large rivers (nearly all of which discharge onto passive margins or marginal seas) have been overestimated, as some of the sediment load is subaerially sequestered in subsiding deltas. Before the proliferation of dam construction in the latter half of this century, rivers probably discharged about 20 billion tons of sediment annually to the ocean. Prior to widespread farming and deforestation (beginning 2000-2500 yr ago), however, sediment discharge probably was less than half the present level. Sediments discharged by small mountainous rivers are more likely to escape to the deep sea during high stands of sea level by virtue of a greater impact of episodic events (i.e., flash floods and earthquakes) on small drainage basins and because of the narrow shelves associated with active margins. The resulting delta/fan deposits can be distinctly different than the sedimentary deposits derived from larger rivers that discharge onto passive margins.

Human impact on land–ocean sediment transfer by the world's rivers

2006-08-02

D. E. Walling

Geologic Nomenclature and Classification of Porosity in Sedimentary Carbonates

1970-01-01

Philip W. Choquette , Lloyd C. Pray

Pore systems in sedimentary carbonates are generally complex in their geometry and genesis, and commonly differ markedly from those of sandstones. Current nomenclature and classifications appear inadequate for concise description … Pore systems in sedimentary carbonates are generally complex in their geometry and genesis, and commonly differ markedly from those of sandstones. Current nomenclature and classifications appear inadequate for concise description or for interpretation of porosity in sedimentary carbonates. In this article we review current nomenclature, propose several new terms, and present a classification of porosity which stresses interrelations between porosity and other geologic features. The time and place in which porosity is created or modified are important elements of a genetically oriented classification. Three major geologic events in the history of a sedimentary carbonate form a practical basis for dating origin and modification of porosity, independent of the stage of lithification. These events are (1) creation of the sedimentary framework by clastic accumulation or accretionary precipitation (final deposition), (2) passage of a deposit below the zone of major influence by processes related to and operating from the deposition surface, and (3) passage of the sedimentary rock into the zone of influence by processes operating from an erosion surface (unconformity). The first event, final deposition, permits recognition of predepositional, depositional, and post epositional stages of porosity evolution. Cessation of final deposition is the most practical basis for distinguishing primary and secondary (postdepositional) porosity. Many of the key postdepositional changes in sedimentary carbonates and their pore systems occur near the surface, either very early in burial history or at a penultimate stage associated with uplift and erosion. Porosity created or modified at these times commonly can be differentiated. On the basis of the three major events heretofore distinguished, we propose to term the early burial stage the late stage telogenetic, and the normally very long intermediate stage mesogenetic. These new terms are also applicable to process, zones of burial, or porosity formed in these times or zones (e.g., eogenetic ceme tation, mesogenetic zone, telogenetic porosity). The proposed classification is designed to aid in geologic description and interpretation of pore systems End_Page 207------------------------------ and their carbonate host rocks. It is a descriptive and genetic system in which 15 basic porosity types are recognized: seven abundant types (interparticle, intraparticle, intercrystal, moldic, fenestral, fracture, and vug), and eight more specialized types. Modifying terms are used to characterize genesis, size and shape, and abundance of porosity. The genetic modifiers involve (1) process of modification (solution, cementation, and internal sedimentation), (2) direction or stage of modification (enlarged, reduced, or filled), and (3) time of porosity formation (primary, secondary, predepositional, depositional, eogenetic, mesogenetic, and telogenetic). Used with the basic porosity type, these genetic modifiers permit explicit designation of porosity origin and evolution. Pore shapes are classed as irregular or regular, and the latter are subdivided into equant, tubular, and platy shapes. A grade scale for size of regular-shaped pores, utilizing the average diameter of equant or tubular pores and the width of platy pores, has three main classes: micropores (< 1/16 mm), mesopores (1/16-4 mm), and megapores (4-256 mm). Megapores and mesopores are divided further into small and large subclasses. Abundance is noted by percent volume and/or by ratios of porosity types. Most porosity in sedimentary carbonates can be related specifically to sedimentary or diagenetic components that constitute the texture or fabric (fabric-selective porosity). Some porosity cannot be related to these features. Fabric selectivity commonly distinguishes pore systems of primary and early postdepositional (eogenetic) origin from those of later (telogenetic) origin that normally form after extensive diagenesis has transformed the very porous assemblage of stable and unstable carbonate minerals into a much less porous aggregate of ordered dolomite and/or calcite. Porosity in most carbonate facies, including most carbonate petroleum reservoir rocks, is largely fabric selective.

Sediment Accumulation Rates and the Completeness of Stratigraphic Sections

1981-09-01

Peter M. Sadler

A compilation of nearly 25,000 rates of sediment accumulation shows that they are extremely variable, spanning at least 11 orders of magnitude. Much of this variation results from compiling rates … A compilation of nearly 25,000 rates of sediment accumulation shows that they are extremely variable, spanning at least 11 orders of magnitude. Much of this variation results from compiling rates determined for different time spans: there is a systematic trend of falling mean rate with increasing time span. The gradients of such trends vary with environment of deposition. Although measurement error and compaction contribute to these regressions, they are primarily the consequence of unsteady, discontinuous sedimentation. The essential character of the unsteadiness may be cyclic or random, but net accumulation is characterized by fluctuations whose magnitudes increase with increasing recurrence interval. Ratios of median long- to short-term accumulation rates provide a measure of the expected completeness of sedimentary stratigraphic sections, at the time scale of the short-term rate. Expected completeness deteriorates as finer time scales are considered.

Impact of Humans on the Flux of Terrestrial Sediment to the Global Coastal Ocean

2005-04-14

James P. M. Syvitski , Charles J Vörösmarty , Albert J. Kettner +1 more

Here we provide global estimates of the seasonal flux of sediment, on a river-by-river basis, under modern and prehuman conditions. Humans have simultaneously increased the sediment transport by global rivers … Here we provide global estimates of the seasonal flux of sediment, on a river-by-river basis, under modern and prehuman conditions. Humans have simultaneously increased the sediment transport by global rivers through soil erosion (by 2.3 +/- 0.6 billion metric tons per year), yet reduced the flux of sediment reaching the world's coasts (by 1.4 +/- 0.3 billion metric tons per year) because of retention within reservoirs. Over 100 billion metric tons of sediment and 1 to 3 billion metric tons of carbon are now sequestered in reservoirs constructed largely within the past 50 years. African and Asian rivers carry a greatly reduced sediment load; Indonesian rivers deliver much more sediment to coastal areas.

Towards the standardization of sequence stratigraphy

2008-10-22

Octavian Catuneanu , Vitor Abreu , Janok P. Bhattacharya +7 more

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Carbonate ramp depositional systems

1992-08-01

Trevor P. Burchette , V. Paul Wright

Mechanism of burial metamorphism of argillaceous sediment: 1. Mineralogical and chemical evidence

1976-01-01

John Hower , Eric Eslinger , MARK E. HOWER +1 more

Research Article| May 01, 1976 Mechanism of burial metamorphism of argillaceous sediment: 1. Mineralogical and chemical evidence JOHN HOWER; JOHN HOWER 1Department of Earth Sciences, Case Western Reserve University, Cleveland, … Research Article| May 01, 1976 Mechanism of burial metamorphism of argillaceous sediment: 1. Mineralogical and chemical evidence JOHN HOWER; JOHN HOWER 1Department of Earth Sciences, Case Western Reserve University, Cleveland, Ohio 44106 Search for other works by this author on: GSW Google Scholar ERIC V. ESLINGER; ERIC V. ESLINGER 2Department of Geology, West Georgia College, Carrollton, Georgia 30117 Search for other works by this author on: GSW Google Scholar MARK E. HOWER; MARK E. HOWER 3Department of Mathematics, Middlebury College, Middlebury, Vermont 05753 Search for other works by this author on: GSW Google Scholar EDWARD A. PERRY EDWARD A. PERRY 4Department of Geology, University of Massachusetts, Amherst, Massachusetts 01002 Search for other works by this author on: GSW Google Scholar Author and Article Information JOHN HOWER 1Department of Earth Sciences, Case Western Reserve University, Cleveland, Ohio 44106 ERIC V. ESLINGER 2Department of Geology, West Georgia College, Carrollton, Georgia 30117 MARK E. HOWER 3Department of Mathematics, Middlebury College, Middlebury, Vermont 05753 EDWARD A. PERRY 4Department of Geology, University of Massachusetts, Amherst, Massachusetts 01002 Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1976) 87 (5): 725–737. https://doi.org/10.1130/0016-7606(1976)87<725:MOBMOA>2.0.CO;2 Article history First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation JOHN HOWER, ERIC V. ESLINGER, MARK E. HOWER, EDWARD A. PERRY; Mechanism of burial metamorphism of argillaceous sediment: 1. Mineralogical and chemical evidence. GSA Bulletin 1976;; 87 (5): 725–737. doi: https://doi.org/10.1130/0016-7606(1976)87<725:MOBMOA>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract A detailed mineralogical and chemical investigation has been made of shale cuttings from a well (Case Western Reserve University Gulf Coast 6) in Oligocene-Miocene sediment of the Gulf Coast of the United States. The <0.1-, 0.1- to 0.5-, 0.5- to 2-, 2- to 10-, and >10-µm fractions from the 1,250- to 5,500-m stratigraphic interval were analyzed by x-ray diffraction. Major mineralogic changes with depth take place over the interval 2,000 to 3,700 m, after which no significant changes are detectable. The most abundant mineral, illite/smectite, undergoes a conversion from less than 20 percent to about 80 percent illite layers over this interval, after which the proportion of illite layers remains constant. Over the same interval, calcite decreases from about 20 percent of the rock to almost zero, disappearing from progressively larger size fractions with increasing depth; potassium feldspar (but not albite) decreases to zero; and chlorite appears to increase in amount. Variations in the bulk chemical composition of the shale with depth show only minor changes, except for a marked decrease in CaO concomitant with the decrease in calcite. By contrast, the <0.1-µm fraction (virtually pure illite/smectite) shows a large increase in K2O and Al2O3 and a decrease in SiO2 The atomic proportions closely approximate the reaction smectite + Al+3 + K+ = illite + Si+4. The potassium and aluminum appear to be derived from the decomposition of potassium feldspar (and mica?), and the excess silicon probably forms quartz. We interpret all the major mineralogical and chemical changes as the response of the shale to burial metamorphism and conclude that the shale acted as a closed system for all components except H2O, CaO, Na2O, and CO2. Compositional changes in the shale as a function of metamorphic grade closely parallel compositional changes in shale as a function of geologic age. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Links between erosion, runoff variability and seismicity in the Taiwan orogen

2003-12-01

Simon Dadson , Niels Hovius , Hongey Chen +7 more

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Turbidity Currents Generated at River Mouths during Exceptional Discharges to the World Oceans

1995-05-01

Thierry Mulder , James P. M. Syvitski

A marine hyperpycnal plume is a particular kind of turbidity current occurring at a river mouth when the concentration of suspended sediment is so large that the density of the … A marine hyperpycnal plume is a particular kind of turbidity current occurring at a river mouth when the concentration of suspended sediment is so large that the density of the river water is greater than the density of sea water. The plume can then plunge and possibly erode the seafloor to become self-maintained for a particular period of time (hours to weeks). Frequency of hyperpycnal plumes emanating from river discharge can be predicted with knowledge of rating curve characteristics, particularly during flood conditions. Examples of these curves are shown for middle-sized North American rivers. Semi-empirical relationships among average discharge, average sediment concentration, and the discharge during flood are proposed and applied to 150 world rivers. Results show the importance of small and medium sized rivers in their ability to trigger underflow at their mouth. There are at least nine "dirty" rivers that may trigger underflows during one or more periods of the year. Most other rivers are cleaner and have hyperpycnal plumes only during floods. Large rivers do not generate underflows at their mouth because sediment retention within their expansive coastal flood plains effectively reduces the upper limit of the suspended concentration. Underflow transport may be an important process in marine-delta construction and should be considered in sedimentary basinfill modeling. Proposed equations and nomograms may assist engineers in infrastructure design seaward of a river mouth.

ROLE OF FLUID PRESSURE IN MECHANICS OF OVERTHRUST FAULTING: REPLY

1965-01-01

WILLIAM W. RUBEY , M. KING HUBBERT

Research Article| April 01, 1965 ROLE OF FLUID PRESSURE IN MECHANICS OF OVERTHRUST FAULTING: REPLY WILLIAM W RUBEY; WILLIAM W RUBEY THE UNIVERSITY OF CALIFORNIA, LOS ANGELES, CALIF.; UNITED STATES … Research Article| April 01, 1965 ROLE OF FLUID PRESSURE IN MECHANICS OF OVERTHRUST FAULTING: REPLY WILLIAM W RUBEY; WILLIAM W RUBEY THE UNIVERSITY OF CALIFORNIA, LOS ANGELES, CALIF.; UNITED STATES GEOLOGICAL SURVEY, WASHINGTON, D. C., AND STANFORD UNIVERSITY, STANFORD, CALIF. Search for other works by this author on: GSW Google Scholar M KING HUBBERT M KING HUBBERT THE UNIVERSITY OF CALIFORNIA, LOS ANGELES, CALIF.; UNITED STATES GEOLOGICAL SURVEY, WASHINGTON, D. C., AND STANFORD UNIVERSITY, STANFORD, CALIF. Search for other works by this author on: GSW Google Scholar Author and Article Information WILLIAM W RUBEY THE UNIVERSITY OF CALIFORNIA, LOS ANGELES, CALIF.; UNITED STATES GEOLOGICAL SURVEY, WASHINGTON, D. C., AND STANFORD UNIVERSITY, STANFORD, CALIF. M KING HUBBERT THE UNIVERSITY OF CALIFORNIA, LOS ANGELES, CALIF.; UNITED STATES GEOLOGICAL SURVEY, WASHINGTON, D. C., AND STANFORD UNIVERSITY, STANFORD, CALIF. Publisher: Geological Society of America Received: 02 Jul 1964 First Online: 02 Mar 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Copyright © 1965, The Geological Society of America, Inc. Copyright is not claimed on any material prepared by U.S. government employees within the scope of their employment. GSA Bulletin (1965) 76 (4): 469–474. https://doi.org/10.1130/0016-7606(1965)76[469:ROFPIM]2.0.CO;2 Article history Received: 02 Jul 1964 First Online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation WILLIAM W RUBEY, M KING HUBBERT; ROLE OF FLUID PRESSURE IN MECHANICS OF OVERTHRUST FAULTING: REPLY. GSA Bulletin 1965;; 76 (4): 469–474. doi: https://doi.org/10.1130/0016-7606(1965)76[469:ROFPIM]2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Davis cites four areas of low-angle faulting in which he believes that high fluid pressures can have played no important part in the development and movement of the thrust plates, but it seems to us that the concept or some variant of it may help to explain the observed field relationships in the three out of these four areas with which we have had some first-hand experience. In the areas of the Heart Mountain thrust of Wyoming, the Muddy Mountain thrust of Nevada, and the structurally higher, crystalline thrust sheets of the Swiss Alps, field relationships which include evidence of dehydration reactions during metamorphism of evaporites and of pelitic rocks suggest that interstitial fluid pressures may have been high and thus have played an essential part in the development of the thrust faults. In the fourth area cited by Davis, that of his own studies in the Klamath Mountains of California, we have had no first-hand experience and thus are not competent to answer his criticisms. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Architectural-element analysis: A new method of facies analysis applied to fluvial deposits

1985-12-01

Andrew D. Miall

Reply to the comments of W. Helland-Hansen on “Towards the standardization of sequence stratigraphy” by Catuneanu et al. [Earth-Sciences Review 92(2009)1–33]

2009-03-14

Octavian Catuneanu , Vitor Abreu , Janok P. Bhattacharya +7 more

Grain Size Distributions and Depositional Processes

1969-01-01

Glenn S. Visher

ABSTRACT Extensive textural study of both modern and ancient sands has provided the basis for a genetic interpretation of sand texture. Analysis is based on recognizing sub-populations within individual log-normal … ABSTRACT Extensive textural study of both modern and ancient sands has provided the basis for a genetic interpretation of sand texture. Analysis is based on recognizing sub-populations within individual log-normal grain size distributions. Each log-normal sub-population may be related to a different mode of sediment transport and deposition, thus providing a measure of their importance in the genesis of a sand unit. The three modes of transport reflected are: (1) suspension; (2) saltation; and (3) surface creep or rolling. Each of these is developed as a separate sub-population within a grain size distribution. The number, amount, size-range, mixing, and sorting of these populations vary systematically in relation to provenance, sedimentary process, and sedimentary dynamics. The analysis of th se parameters is the basis for determining the process-response characteristics of individual sand units. A number of processes are uniquely reflected in log-probability curves of grain size distributions of sands and sandstones. These include: (1) current; (2) swash and backwash; (3) wave; (4) tidal channel; (5) fallout from suspension; (6) turbidity current; and (7) aeolian dune. The combination of two or more of these processes also produce characteristic log-probability curve shapes. Ancient sands show some differences from their modern analogues, but these are usually minor. Log-probability plots of ancient sands are directly comparable to those from modern sands. The principal limitation of this study is in comparing sands formed under comparable conditions and obtaining an independent determination of the processes of formation of ancient sands.

GRADISTAT: a grain size distribution and statistics package for the analysis of unconsolidated sediments

2001-09-28

Simon J. Blott , Kenneth Pye

Abstract Grain size analysis is an essential tool for classifying sedimentary environments. The calculation of statistics for many samples can, however, be a laborious process. A computer program called GRADISTAT … Abstract Grain size analysis is an essential tool for classifying sedimentary environments. The calculation of statistics for many samples can, however, be a laborious process. A computer program called GRADISTAT has been written for the rapid analysis of grain size statistics from any of the standard measuring techniques, such as sieving and laser granulometry. Mean, mode, sorting, skewness and other statistics are calculated arithmetically and geometrically (in metric units) and logarithmically (in phi units) using moment and Folk and Ward graphical methods. Method comparison has allowed Folk and Ward descriptive terms to be assigned to moments statistics. Results indicate that Folk and Ward measures, expressed in metric units, appear to provide the most robust basis for routine comparisons of compositionally variable sediments. The program runs within the Microsoft Excel spreadsheet package and is extremely versatile, accepting standard and non‐standard size data, and producing a range of graphical outputs including frequency and ternary plots. Copyright © 2001 John Wiley & Sons, Ltd.

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Sediment Gravity Flows: II Depositional Models with Special Reference to the Deposits of High-Density Turbidity Currents

1982-01-01

Donald R. Lowe

ABSTRACT Four principal mechanisms of deposition are effective in the formation of sediment gravity flow deposits. Grains deposited by traction sedimentation and suspension sedimentation respond individually and accumulate directly from … ABSTRACT Four principal mechanisms of deposition are effective in the formation of sediment gravity flow deposits. Grains deposited by traction sedimentation and suspension sedimentation respond individually and accumulate directly from bed and suspended loads, respectively. Those deposited by frictional freezing and cohesive freezing interact through either frictional contact or cohesive forces, respectively, and are deposited collectively, usually by plug formation. Sediment deposition from individual sediment flows commonly involves more than one of these mechanisms acting either serially as the flow evolves or simultaneously on different grain populations. Deposition from turbidity currents is treated in terms of three dynamic grain populations: 1) clay- to medium-grained sand-sized particles that can be fully suspended as individual grains by flow turbulence, 2) coarse-grained sand to small-pebble-sized gravel that can be fully suspended in large amounts mainly in highly concentrated turbulent suspensions where grain fall velocity is substantially reduced by hindered settling, and 3) pebble- and cobble-sized clasts having concentrations greater than 10 percent to 15 percent that will be supported largely by dispersive pressure resulting from clast collisions and by buoyant lift provided by the interstitial mixture of water and finer-grained sediment. The effects of hindered settling, dispersive pressure, and matrix buoyant lift are con entration dependent, and grain populations 2 and 3 are likely to be transported in large amounts only within flows having high particle concentrations, probably in excess of 20 percent solids by volume. Low-density turbidity currents, made up largely of grains of population 1, typically show an initial period of traction sedimentation, forming Bouma (Tb) and Tc) divisions, followed by one of mixed traction and suspension sedimentation (Td), and a terminal period of fine-grained suspension sedimentation (Te). The sediment loads of high-density turbidity currents commonly include grains belonging to populations 1, 2, and 3. Consequently, deposition often occurs as a series of discrete sedimentation waves as flows decelerate and individual grain populations can no longer be maintained in transport. Each sedimentation wave tends to show increasing unsteadiness and accelerating sedimentation rate as it evolves, passing from an initial stage of traction sedimentation, to one of mixed frictional freezing and suspension sedimentation within traction carpets, to a final stage of direct suspension sedimentation. Sequences of sedimentary structure divisions representing this succession of depositional stages are here termed the ecoR1-3) sequence, representing population 3 grains, and the S1-3) sequence, representing population 2. Deposition of the high-density suspended load leaves behind a residual low-density turbidity current composed largely of population 1 grains. At their distal ends, high-density turbidity currents deposit mainly by suspension sedimentation, forming thin (S3) divisions. These (S3) divisions are the same as Bouma (Ta) and, if subsequently capped by (Tb-e) deposited by the residual low-density flows, become the basal divisions of normal turbidities. Liquefied flows deposit by direct high-density suspension sedimentation. Grain flows of sand are characterized by frictional freezing and their deposits are limited mainly to angle-of-repose slipface units. Density-modified grain flows, in which larger clasts are partially supported by matrix buoyancy, and traction carpets, in which a dense frictional grain dispersion is driven by an overlying turbulent flow, are important in the buildup of natural deposits on submarine slopes. Cohesive debris flows depost sediment mainly by cohesive freezing, commonly modified by suspension sedimentation of the largest clasts.

Description and analysis of bioturbation and ichnofabric

1993-01-01

Andrew M. Taylor , R. Goldring

A new scheme for the description and analysis of bioturbation and the resultant ichnofabrics is proposed. This system can be used in core and field-based studies and consists of two … A new scheme for the description and analysis of bioturbation and the resultant ichnofabrics is proposed. This system can be used in core and field-based studies and consists of two parts. (1) A bioturbation index in which a descriptive grade is assigned to the degree of bioturbation. This integrates the sedimentology and ichnology, where the higher grades of bioturbation result from increased burrow overlap and the subsequent loss of the primary sedimentary fabric. (2) An ichnofabric constituent diagram which records the detail of the ichnofabric by graphically plotting the dimensional data of the ichnotaxa and their order of emplacement against their coverage. This scheme differs from previous attempts to characterize bioturbation using semi-quantatitive methods and visually portrays the ichnofabric so that comparative studies can be carried out. This is of particular use in facies analysis, the establishment of the ichnocoenoses and tier diagrams, and within sequence stratigraphic studies so that hiatal surfaces can be recognized.

Evolution of Metamorphic Belts

1961-01-01

Akiho Miyashiro

The metamorphic facies series in regional metamorphism may be classified into the following categories according to an order of increasing rock pressure: (1) andalusite-sillimanite type, (2) low-pressure intermediate group, (3) … The metamorphic facies series in regional metamorphism may be classified into the following categories according to an order of increasing rock pressure: (1) andalusite-sillimanite type, (2) low-pressure intermediate group, (3) kyanite-sillimanite type, (4) high-pressure intermediate group, and (5) jadeite-glaucophane type. In Japan and other parts of the circum-Pacific region, a metamorphic belt of the andalusite-sillimanite type and/or low-pressure intermediate group and another metamorphic belt of the jadeite-glaucophane type and/or high-pressure intermediate group run side by side, forming a pair. The latter belt is always on the Pacific Ocean side. They were probably formed in different phases of the same cycle of orogeny. Their origin is discussed. Regional metamorphism under higher rock pressures appears to have taken place in later geological times. The metamorphic facies series of contact metamorphism are briefly discussed.

Morphologic and facies trends through the fluvial–marine transition in tide-dominated depositional systems: A schematic framework for environmental and sequence-stratigraphic interpretation

2007-03-29

Robert W. Dalrymple , Kyungsik Choi

Estuarine facies models; conceptual basis and stratigraphic implications

1992-11-01

Robert W. Dalrymple , Brian A. Zaitlin , Ron Boyd

The nature and organization of facies within incised-valley estuaries is controlled by the interplay between marine processes (waves and tides), which generally decrease in intensity up-estuary, and fluvial processes, which … The nature and organization of facies within incised-valley estuaries is controlled by the interplay between marine processes (waves and tides), which generally decrease in intensity up-estuary, and fluvial processes, which decrease in strength down-estuary. All estuaries ideally possess a three-fold (tripartite) structure: an outer, marine-dominated portion where the net bedload transport is headward; a relatively low-energy central zone where there is net bedload convergence; and an inner, river-dominated (but marine-influenced) part where the net transport is seaward. These three zones are not equally developed in all estuaries because of such factors as sediment availability, coastal zone gradient and the stage of estuary evolution. Two distinct but intergradational types of estuaries (wave- and tide-dominated) are recognized on the basis of the dominant marine process. Wave-dominated estuaries typically possess a well-defined tripartite zonation: a marine sand body comprised of barrier, washover, tidal inlet and tidal delta deposits; a fine-grained (generally muddy) central basin; and a bay-head delta that experiences tidal and/or salt-water influence. The marine sand body in tide-dominated estuaries consists of elongate sand bars and broad sand flats that pass headward into a low-sinuosity (straight) single channel; net sand transport is headward in these areas. The equivalent of the central basin consists of a zone of tight meanders where bedload transport by flood-tidal and river currents is equal in the long term, while the inner, river-dominated zone has a single, low-sinuosity (straight) channel. These facies models and their conceptual basis provide a practical means of highlighting the differences and similarities between estuaries. They also allow the predication of the stratigraphy of estuarine deposits within a sequence-stratigraphic context.

Geophysical Fluid Dynamics

1981-09-01

Joseph Pedlosky , S. Leibovich

Preliminaries * Fundamentals * Inviscid Shallow-Water Theory * Friction and Viscous Flow * Homogeneous Models of the Wind-Driven Oceanic Circulation * Quasigeostrophic Motion of a Stratified Fluid on a Sphere … Preliminaries * Fundamentals * Inviscid Shallow-Water Theory * Friction and Viscous Flow * Homogeneous Models of the Wind-Driven Oceanic Circulation * Quasigeostrophic Motion of a Stratified Fluid on a Sphere * Instability Theory * Ageostrophic Motion

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The physical character of subaqueous sedimentary density flows and their deposits

2001-04-06

Thierry Mulder , Jan Alexander

The complexity of flow and wide variety of depositional processes operating in subaqueous density flows, combined with post‐depositional consolidation and soft‐sediment deformation, often make it difficult to interpret the characteristics … The complexity of flow and wide variety of depositional processes operating in subaqueous density flows, combined with post‐depositional consolidation and soft‐sediment deformation, often make it difficult to interpret the characteristics of the original flow from the sedimentary record. This has led to considerable confusion of nomenclature in the literature. This paper attempts to clarify this situation by presenting a simple classification of sedimentary density flows, based on physical flow properties and grain‐support mechanisms, and briefly discusses the likely characteristics of the deposited sediments. Cohesive flows are commonly referred to as debris flows and mud flows and defined on the basis of sediment characteristics. The boundary between cohesive and non‐cohesive density flows (frictional flows) is poorly constrained, but dimensionless numbers may be of use to define flow thresholds. Frictional flows include a continuous series from sediment slides to turbidity currents. Subdivision of these flows is made on the basis of the dominant particle‐support mechanisms, which include matrix strength (in cohesive flows), buoyancy, pore pressure, grain‐to‐grain interaction (causing dispersive pressure), Reynolds stresses (turbulence) and bed support (particles moved on the stationary bed). The dominant particle‐support mechanism depends upon flow conditions, particle concentration, grain‐size distribution and particle type. In hyperconcentrated density flows, very high sediment concentrations (>25 volume%) make particle interactions of major importance. The difference between hyperconcentrated density flows and cohesive flows is that the former are friction dominated. With decreasing sediment concentration, vertical particle sorting can result from differential settling, and flows in which this can occur are termed concentrated density flows. The boundary between hyperconcentrated and concentrated density flows is defined by a change in particle behaviour, such that denser or larger grains are no longer fully supported by grain interaction, thus allowing coarse‐grain tail (or dense‐grain tail) normal grading. The concentration at which this change occurs depends on particle size, sorting, composition and relative density, so that a single threshold concentration cannot be defined. Concentrated density flows may be highly erosive and subsequently deposit complete or incomplete Lowe and Bouma sequences. Conversely, hydroplaning at the base of debris flows, and possibly also in some hyperconcentrated flows, may reduce the fluid drag, thus allowing high flow velocities while preventing large‐scale erosion. Flows with concentrations <9% by volume are true turbidity flows ( sensu Bagnold, 1962 ), in which fluid turbulence is the main particle‐support mechanism. Turbidity flows and concentrated density flows can be subdivided on the basis of flow duration into instantaneous surges, longer duration surge‐like flows and quasi‐steady currents. Flow duration is shown to control the nature of the resulting deposits. Surge‐like turbidity currents tend to produce classical Bouma sequences, whose nature at any one site depends on factors such as flow size, sediment type and proximity to source. In contrast, quasi‐steady turbidity currents, generated by hyperpycnal river effluent, can deposit coarsening‐up units capped by fining‐up units (because of waxing and waning conditions respectively) and may also include thick units of uniform character (resulting from prolonged periods of near‐steady conditions). Any flow type may progressively change character along the transport path, with transformation primarily resulting from reductions in sediment concentration through progressive entrainment of surrounding fluid and/or sediment deposition. The rate of fluid entrainment, and consequently flow transformation, is dependent on factors including slope gradient, lateral confinement, bed roughness, flow thickness and water depth. Flows with high and low sediment concentrations may co‐exist in one transport event because of downflow transformations, flow stratification or shear layer development of the mixing interface with the overlying water (mixing cloud formation). Deposits of an individual flow event at one site may therefore form from a succession of different flow types, and this introduces considerable complexity into classifying the flow event or component flow types from the deposits.

Marine hyperpycnal flows: initiation, behavior and related deposits. A review

2003-06-01

Thierry Mulder , James P. M. Syvitski , Sébastien Migeon +2 more

Fluvial responses to climate and sea‐level change: a review and look forward

2000-02-01

Michael D. Blum , Torbjörn E. Törnqvist

Summary Fluvial landforms and deposits provide one of the most readily studied Quaternary continental records, and alluvial strata represent an important component in most ancient continental interior and continental margin … Summary Fluvial landforms and deposits provide one of the most readily studied Quaternary continental records, and alluvial strata represent an important component in most ancient continental interior and continental margin successions. Moreover, studies of the long‐term dynamics of fluvial systems and their responses to external or ‘allogenic' controls, can play important roles in research concerning both global change and sequence‐stratigraphy, as well as in studies of the dynamic interactions between tectonic activity and surface processes. These themes were energized in the final decades of the twentieth century, and may become increasingly important in the first decades of this millennium. This review paper provides a historical perspective on the development of ideas in the fields of geomorphology/Quaternary geology vs. sedimentary geology, and then summarizes key processes that operate to produce alluvial stratigraphic records over time‐scales of 10 3 −10 6 years. Of particular interest are changes in discharge regimes, sediment supply and sediment storage en route from source terrains to sedimentary basins, as well as changes in sea‐level and the concept of accommodation. Late Quaternary stratigraphic records from the Loire (France), Mississippi (USA), Colorado (Texas, USA) and Rhine–Meuse (The Netherlands) Rivers are used to illustrate the influences of climate change on continental interior rivers, as well as the influence of interacting climate and sea‐level change on continental margin systems. The paper concludes with a look forward to a bright future for studies of fluvial response to climate and sea‐level change. At present, empirical field‐based research on fluvial response to climate and sea‐level change lags behind: (a) the global change community's understanding of the magnitude and frequency of climate and sea‐level change; (b) the sequence‐stratigraphic community's desire to interpret climate and, especially, sea‐level change as forcing mechanisms; and (c) the modelling community's ability to generate numerical and physical models of surface processes and their stratigraphic results. A major challenge for the future is to catch up, which will require the development of more detailed and sophisticated Quaternary stratigraphic, sedimentological and geochronological frameworks in a variety of continental interior and continental margin settings. There is a particular need for studies that seek to document fluvial responses to allogenic forcing over both shorter (10 2 −10 3 years) and longer (10 4 −10 6 years) time‐scales than has commonly been the case to date, as well as in larger river systems, from source to sink. Studies of Quaternary systems in depositional basin settings are especially critical because they can provide realistic analogues for interpretation of the pre‐Quaternary rock record.

Flux and fate of Yangtze River sediment delivered to the East China Sea

2006-09-09

Paul Liu , Kehui Xu , A.C. Li +4 more

Perspectives on the Sequence Stratigraphy of Continental Strata

1994-01-01

Peter J. McCa Keith W. Shanley

This report is the result of a working group on continental sequence stratigraphy that was set up at the 1991 NUNA conference in Banff, Canada. To date, sequence stratigraphic concepts … This report is the result of a working group on continental sequence stratigraphy that was set up at the 1991 NUNA conference in Banff, Canada. To date, sequence stratigraphic concepts have been applied mainly to the marine realm, but unconformity-bounded units have long been recognized in nonmarine strata. Successful application of sequence stratigraphic concepts to continental strata requires careful consideration of controls on base level and sediment supply. As with shallow marine environments, relative sea level can be considered as the stratigraphic as well as the geomorphic base level for coastal nonmarine settings. Farther inland, stratigraphic base level, which determines accommodation space, is more complex and takes various forms, such as the graded profile for fluvial strata, groundwater tables for some eolian strata, and lake level for some intermontane sediments. Sediment supply is also generally a more complex variable for nonmarine environments than in the marine realm because of the proximity to the source area. The influence of climate and tectonism on sediment supply can clearly be seen in many continental sediments. The fact that the major controls of climate, tectonism, and eustasy are somewhat interdependent, and that a change in one parameter will most likely be reflected in others, is also more readily apparent in continental strata. Although in its infancy, sequence stratigraphic concepts have been applied to a wide variety of continental settings in attempts to explain variations in facies architecture. Of particular interest are studies that have linked fluvial architecture on coastal plains to variations in relative sea level as indicated by coeval marine strata, and studies of lacustrine environments that show marked variation in facies between highstand and lowstand deposits. The application of sequence stratigraphy to continental strata will likely result in the development of better correlation techniques and models that better predict the location and nature of fluvial and eolian reservoirs.

Genetic Stratigraphic Sequences in Basin Analysis I: Architecture and Genesis of Flooding-Surface Bounded Depositional Units

1989-01-01

William E. Galloway

Marine basin margins are characterized by repetitive episodes of progradation punctuated by periods of transgression and flooding of the depositional platform. The resultant stratigraphic units consist of genetically related (1) … Marine basin margins are characterized by repetitive episodes of progradation punctuated by periods of transgression and flooding of the depositional platform. The resultant stratigraphic units consist of genetically related (1) depositional systems and their component facies sequences; (2) bypass, nondepositional, and erosional surfaces; and (3) in thick sequences affected by gravity tectonics and crustal response to loading, syndepositional structural discontinuities. Units are bounded by hiatal surfaces preserved as submarine unconformities or condensed sedimentary veneers and that record maximum marine flooding of the basin margin. The repetitive stratigraphic architecture is the product of the ongoing interplay among sediment supply, basin subsidence (and uplift), an eustatic sea level change. Each of these three variables may dominate depositional evolution; furthermore, stratigraphic architecture is very similar regardless of the dominant control. A genetic stratigraphic sequence is the sedimentary product of a depositional episode. The sequence incorporates and reconciles depositional systems, bedding geometries, and bounding surfaces within the framework of cycles of basin-margin offlap and flooding. Each sequence consists of the progradational, aggradational, and retrogradational or transgressive facies deposited during a period of regional paleogeographic stability. The defining genetic stratigraphic sequence boundary is a sedimentary veneer or surface that records the depositional hiatus that occurs over much of the transgressed shelf and adjacent slope during maximum marine flooding. The genetic sequence paradigm emphasizes preserving the stratigraphic integrity of three-dimensional depositional systems and does not rely n widespread development of subaerial erosion surfaces caused by eustatic falls of sea level to define sequence boundaries. The physical stratigraphic record of transgression and flooding--distinctive thin but widespread facies sequences, prominent erosional surfaces, and superjacent marine condensed intervals or sedimentary veneers--provides readily recognized, regionally correlative, easily and accurately datable, and robust sequence boundaries that commonly define times of major basin-margin paleogeographic reorganization in terrigenous clastic basins.

Influence of Texture on Porosity and Permeability of Unconsolidated Sand

1973-01-01

P. K. Weyl D. C. Beard

An investigation has been made of the relations among porosity, permeability, and texture of artificially mixed and packed sand, to determine the approximate porosity and permeability values to be expected … An investigation has been made of the relations among porosity, permeability, and texture of artificially mixed and packed sand, to determine the approximate porosity and permeability values to be expected for unconsolidated sand of eight grain-size subclasses and six sorting groups. The sand samples were prepared so that the weight fractions were distributed normally about the median grain size. Porosity values were determined for two packings, designated as dry-loose and wet-packed. Porosity data for sand samples remain about the same for changes in grain size of a given sorting, but decrease from an average of 42.4 percent for extremely well-sorted sand to 27.9 percent for very poorly sorted sand. These experimental data agree within 5 porosity percent with framework porosity values obtained for natural packing of 25 Holocene barrier-island sand samples of a limited size-sorting range, and appear to be representative of minimum porosities expected for natural packing of most unconsolidated, clay-free sand. The 48 artificially mixed and wet-packed experimental sands selected for porosity measurement also were used to determine permeability. Inasmuch as there are some irregularities in the experimental data caused by the inability to pack each sample uniformly, an average adjusted permeability value has been calculated. The average adjusted permeability values become progressively lower with decreasing grain size and poorer sorting, and agree well with permeability values computed by the Krumbein and Monk formula for most grain-size and sorting classes. Reference photographs or visual textural comparators enable a rapid estimation of grain shape, roundness, size, and sorting. Grain-size-sorting comparators, representing photomicrographs of thin sections of the porosity and permeability test samples, are especially useful in estimating original textural parameters form thin sections of severely compacted and silica-cemented sandstones.

Brazos River bar [Texas]; a study in the significance of grain size parameters

1957-03-01

Robert L. Folk , W Ward

A bar on the Brazos River near Calvert, Texas, has been analyzed in order to determine the geologic meaning of certain grain size parameters and to study the behavior of … A bar on the Brazos River near Calvert, Texas, has been analyzed in order to determine the geologic meaning of certain grain size parameters and to study the behavior of the size fractions with transport. The bar consists of a strongly bimodal mixture of pebble gravel and medium to fine sand; there is a lack of material in the range of 0.5 to 2 mm, because the source does not supply particles of this size. The size distributions of the two modes, which were established in the parent deposits, are nearly invariant over the bar because the present environment of deposition only affects the relative proportions of the two modes, not the grain size properties of the modes themselves. Two proportions are most common; the sediment either contains no gravel or else contains about 60% gravel. Three sediment types with characteristic bedding features occur on the bar in constant stratigraphic order, with the coarsest at the base. Statistical analysis of the data is based on a series of grain size parameters modified from those of Inman (1952) to provide a more detailed coverage of non-normal size curves. Unimodal sediments have nearly normal curves as defined by their skewness and kurtosis. Non-normal kurtosis and skewness values are held to be the identifying characteristics of bimodal sediments even where such modes are not evident in frequency curves. The relative proportions of each mode define a systematic series of changes in numerical properties; mean size, standard deviation and skewness are shown to be linked in a helical trend, which is believed to be applicable to many other sedimentary suites. The equations of the helix may be characteristic of certain environments. Kurtosis values show rhythmic pulsations along the helix and are diagnostic of two-generation sediments.

The propagation of two-dimensional and axisymmetric viscous gravity currents over a rigid horizontal surface

1982-08-01

Herbert E. Huppert

The viscous gravity current that results when fluid flows along a rigid horizontal surface below fluid of lesser density is analysed using a lubrication-theory approximation. It is shown that the … The viscous gravity current that results when fluid flows along a rigid horizontal surface below fluid of lesser density is analysed using a lubrication-theory approximation. It is shown that the effect on the gravity current of the motion in the upper fluid can be expressed as a condition of zero shear on the unknown upper surface of the gravity current. With the supposition that the volume of heavy fluid increases with time like tα, where α is a constant, a similarity solution to the governing nonlinear partial differential equations is obtained, which describes the shape and rate of propagation of the current. The viscous theory is shown to be valid for t [Gt ] t1, when α < αc and for t [Lt ] t1 when α > αc, where t1, is the transition time at which the inertial and viscous forces are equal, with for a two-dimensional current and αc = 3 for an axisymmetric current. The solutions confirm the functional forms for the spreading relationships determined for α = 1 in the preceding paper by Didden & Maxworthy (1982), as well as evaluating the multiplicative factors appearing in the relationships. The relationships compare very well with experimental measurements of the axisymmetric spreading of silicone oils into air for α = 0 and 1. There is also very good agreement between the theoretical predictions and the measurements of the axisymmetric spreading of salt water into fresh water reported by Didden & Maxworthy and by Britter (1979). The predicted multiplicative constant is within 10% of that measured by Didden & Maxworthy for the spreading of salt water into fresh water in a channel.

Submarine landslides

1996-02-01

Monty A. Hampton , Homa J. Lee , Jacques Locat

Landslides are common on inclined areas of the seafloor, particularly in environments where weak geologic materials such as rapidly deposited, fine‐grained sediment or fractured rock are subjected to strong environmental … Landslides are common on inclined areas of the seafloor, particularly in environments where weak geologic materials such as rapidly deposited, fine‐grained sediment or fractured rock are subjected to strong environmental stresses such as earthquakes, large storm waves, and high internal pore pressures. Submarine landslides can involve huge amounts of material and can move great distances: slide volumes as large as 20,000 km³ and runout distances in excess of 140 km have been reported. They occur at locations where the downslope component of stress exceeds the resisting stress, causing movement along one or several concave to planar rupture surfaces. Some recent slides that originated nearshore and retrogressed back across the shoreline were conspicuous by their direct impact on human life and activities. Most known slides, however, occurred far from land in prehistoric time and were discovered by noting distinct to subtle characteristics, such as headwall scarps and displaced sediment or rock masses, on acoustic‐reflection profiles and side‐scan sonar images. Submarine landslides can be analyzed using the same mechanics principles as are used for occurrences on land. However, some loading mechanisms are unique, for example, storm waves, and some, such as earthquakes, can have greater impact. The potential for limited‐deformation landslides to transform into sediment flows that can travel exceedingly long distances is related to the density of the slope‐forming material and the amount of shear strength that is lost when the slope fails.

The Geology of Fluvial Deposits

2006-01-01

Andrew D. Miall

Factors controlling carbonate mud production and accumulation on Upper Jurassic western European mixed siliciclastic–carbonate ramps

2025-06-23

Claude Colombié , Fabienne Giraud , Pauline Guenser +1 more | Sedimentology

ABSTRACT The sedimentological and calcareous nannofossil analysis of the siliciclastic‐dominated Cap de la Crèche section (Boulonnais ramp, northern France) and its comparison with five other Upper Jurassic mixed ramps from … ABSTRACT The sedimentological and calcareous nannofossil analysis of the siliciclastic‐dominated Cap de la Crèche section (Boulonnais ramp, northern France) and its comparison with five other Upper Jurassic mixed ramps from western Europe provide a better understanding of the physico‐chemical and ecological parameters that controlled carbonate production and accumulation within these muddy ramp systems. The sedimentological analysis of the Cap de la Crèche section indicates that most of the carbonate fraction corresponds to sand bars and storm deposits, suggesting sediment reworking from the production area to the accumulation site. The calcareous nannofossil analysis shows that carbonate mud is partly composed of in situ ‐produced ascidian spicules. However, the comparison of these results with published data for the five other ramps indicates that these muddy systems differ more in their physico‐chemical characteristics than in their ecological features. The multivariate statistical analysis showed that variables contributing the most to the overall variance are: (i) calcium carbonate content, ramp morphology and main mid‐ramp facies; (ii) palaeolatitude and main inner ramp facies; and (iii) vertical facies evolution trend. The relationships between calcium carbonate content, ramp morphology and main mid‐ramp facies is interpreted to reflect the impact of local/specific physiographic and hydrodynamic processes shaping the ramps and favouring carbonate accumulation in the mid carbonate ramp. Hydrodynamics was one of the main parameters controlling these muddy systems, probably due to the presence of both sticky mud and moving mud waves. This work also shows that carbonate ramps positioned at the lowest palaeolatitudes display carbonate‐dominated inner ramp facies. This result is consistent with available classifications of carbonate factories, although each specificity may lead to discrepancies and require further investigation. Progradational or retrogradational vertical facies evolution trends most likely result from relative sea‐level changes rather than variations in clastics supply or carbonate production rates. Combined with the above specific/local controlling factors, relative sea‐level changes explain the sedimentary architectures observed in outcrop. The outcome of the evaluation discussed in this manuscript may be useful in forward stratigraphic modelling of other mixed siliciclastic–carbonate ramps.

Subaqueous multiscale bedform morphology dynamics in a mountainous macrotidal estuary

2025-06-23

Ruiqing Liu , Heqin Cheng , Jinfeng Chen +5 more | Frontiers in Marine Science

Bedforms in macrotidal estuaries and deltas are distinguished from those in rivers and oceans due to the tidally-driven water depth variations and the varying hydrodynamic processes resulting from the interaction … Bedforms in macrotidal estuaries and deltas are distinguished from those in rivers and oceans due to the tidally-driven water depth variations and the varying hydrodynamic processes resulting from the interaction between tidal and fluvial flows. The relations between hydrodynamics, sediment transport, and bedform morphology in these estuaries are complex, but research on the morphodynamics of bedforms in such environments is still lacking. This study explores the morphodynamic development patterns of multiscale bedforms in mountainous estuaries and tidal deltas, using the Minjiang Estuary as a representative case. Field observations were conducted in the Minjiang Estuary in the East China Sea in December 2021 (dry season) and August 2023 (flood season) using a multibeam echosounder system and an Acoustic Doppler Current Profiler (ADCP). Bedform presence and characteristics were calculated from bed elevation data. The results indicate that bedforms are widely developed from the underwater delta plain to the delta front channel of the Minjiang Estuary, with large compound bedforms being prevalent. Both primary and secondary bedforms coexist, with wavelengths ranging from 2 to 233 meters and heights from 0.1 to 6 meters. About 60% of primary bedforms exhibit ebb asymmetry, indicating ebb-directed sediment transport in the main channel. The average flood/ebb lee side angle is 6°, with an average maximum angle of 19°. The maximum side angle of primary bedforms is observed to be on average greater than that of secondary bedforms. Water depth and riverbed slope significantly affect bedform density, with non-sloping riverbeds favoring bedform development. Variations in bed shear stress throughout the tidal cycle drive differences in bedform size and morphology. High clay content in surface sediments correlates with lower bedform density, indicating fine-grained materials may inhibit bedform development. This study highlights a feedback mechanism where structural geology shapes channel morphology, influencing energy distribution and bedform evolution. The findings enhance our understanding of sediment transport and hydrodynamic processes in macrotidal estuaries, offering insights for estuarine management and conservation. Future research should explore how seasonal and tidal variations influence bedform evolution to refine models of estuarine dynamics.

Km-scale mounds and sinkites formed by buoyancy driven stratigraphic inversion

2025-06-21

Jan Erik Rudjord , Mads Huuse | Communications Earth & Environment

Critical factors affecting rheological properties of surface fluid sediment in one large shallow lake

2025-06-20

Chunliu Wang , Xinyue Zhou , Linqi Tian +7 more | Journal of Environmental Management

Geochemical and Digenetic controls on the Dammam Formation in the Southern Desert of Iraq

2025-06-19

Maher M. Mahdi , Falah H. Maziqa , Hamid Alsultan | Research Square (Research Square)

<title>Abstract</title> The integrated geochemical and diagenesis process provide valuable understandings into the depositional environments and mineral resources of the Eocene succession in the region, supporting both geological understanding and economic … <title>Abstract</title> The integrated geochemical and diagenesis process provide valuable understandings into the depositional environments and mineral resources of the Eocene succession in the region, supporting both geological understanding and economic exploration efforts. This research utilizes geochemical and petrographic analyses of sediment samples (24 core samples) from the Dammam Formation in southern Iraq to reconstruct paleoenvironmental conditions during the Eocene epoch. The formation is primarily composed of carbonate lithology, predominantly limestone with dolomitic and fossiliferous strata, and exhibits evidence of extensive diagenetic alterations such as dolomitization, silicification and other processes. Geochemical data reveal high concentrations of calcium and magnesium oxides, consistent with carbonate-rich, shallow marine depositional environments. Notably, the presence of unconformities at the boundaries with the Euphrates and Rus formations indicates depositional hiatuses likely linked to sea-level fluctuations. Elemental correlations suggest a dominant marine influence with limited terrigenous input, as reflected in the low concentrations of SiO₂, Al₂O₃, Fe₂O₃, and alkali oxides. Variations in sulfate oxides and the occurrence of gypsum nodules point to fluctuating salinity conditions, possibly related to lagoonal or restricted platform environments. Silicification processes, especially in the central regions of the formation, involve silica filling voids and replacing carbonate minerals, indicating diagenetic silica enrichment during lithification. The presence of red-stained marl zones and iron oxides signifies oxidative, coastal, peritidal settings. Overall, the integrated geochemical and petrographic evidence supports interpretations of a dynamic depositional environment characterized by shallow marine, lagoonal, and restricted platform conditions, which reflect significant sea-level changes during the Eocene and contribute to understanding regional sedimentation and diagenetic histories.

Depositional patterns of the Cambrian Araba Formation along the Taba-Naqab Road, east-central Sinai, Egypt: paleoenvironmental reconstruction and correlation in Northern Gondwana

2025-06-18

Ibrahim M. Ghandour , Olaf Elicki , Ramadan M. El-Kahawy | Journal of African Earth Sciences

Underlying mechanism of the great thickness of granite weathering crust: Reduction of ridge erosion via coarse quartz particles

2025-06-18

Yishan Liao , Dingqiang Li , Zaijian Yuan +5 more | CATENA

Systematic Description of Ammonites from the Jumara Formation at Jara Dome, Kachchh Mainland

2025-06-17

Rinku A. Patel , Paras M. Solanki | International Journal of Scientific Research in Science and Technology

The Jara Dome, situated in the Lakhpat Taluka of Kachchh District, Gujarat, represents a significant geological structure within the Kachchh Mainland and provides exceptional exposure of Middle to Upper Jurassic … The Jara Dome, situated in the Lakhpat Taluka of Kachchh District, Gujarat, represents a significant geological structure within the Kachchh Mainland and provides exceptional exposure of Middle to Upper Jurassic strata. This study documents ammonite-bearing horizons within the Dhosa Oolite Member of the Jumara Formation, composed of fossiliferous oolitic limestones interbedded with shales and ferruginous beds. Detailed field investigations and systematic sampling yielded five ammonite taxa, all recovered from stratigraphically constrained intervals. Taxonomic identification was conducted through comparative morphological analysis, revealing a diverse assemblage that contributes to refining the biostratigraphic framework of the region. The presence of genera such as Perisphinctes, Cadoceras, and Macrocephalites provides key insights into ammonoid evolution and regional stratigraphic correlation. Structurally, the study area is influenced by the Kachchh Mainland Fault and associated neotectonic activity, which have played a role in shaping the sedimentary and structural architecture of the Jara Dome. The integration of paleontological, stratigraphic, and structural data enhances our understanding of Jurassic depositional environments and basin evolution in western India.

Unraveling the impact of sediment size distribution on flow-sediment hysteresis in estuarine environments: insights from size-resolved sediment transport modeling

2025-06-13

Zheng Fang , Fanghua Xu , X. Zhang | Environmental Research Communications

Abstract Flow-sediment hysteresis, a nonlinear time-lagged relationship between sediment transport and hydrodynamic conditions, is particularly important yet difficult to simulate in tidal estuarine environments. This study introduces a size-resolved sediment … Abstract Flow-sediment hysteresis, a nonlinear time-lagged relationship between sediment transport and hydrodynamic conditions, is particularly important yet difficult to simulate in tidal estuarine environments. This study introduces a size-resolved sediment transport model to simulate flow-sediment hysteresis, with an application in the Hudson River estuary. By incorporating variations in sediment size distribution induced by flocculation, the model allows for a more accurate simulation of flow-sediment hysteresis compared to traditional size-fixed models, achieving accuracy improvements of 4.89%~12.19% during tidal cycles. Moreover, budget analyses and correlation matrix analyses are conducted. The results indicate that the dynamics of small and large flocs influence hysteresis differentially: flocculation processes dominate the behavior of small flocs, while settling and vertical diffusion processes primarily affect large flocs. These insights offer a deeper understanding of sediment transport in tidal estuaries, providing a robust framework for enhanced predictive modeling which can be adapted to other estuarine environments.

Caracterização granulométrica dos depósitos alúvio-coluviais de microbacias do rio Copiapó – região de Atacama (Chile)

2025-06-13

Keyla Manuela Alencar da Silva Alves , Drielly Naamma Fonsêca , Marcelo Lagos +1 more | Revista de Geociências do Nordeste

Este estudio se enfoca en caracterizar la granulometría de los sedimentos en depósitos aluvio-coluviales en la cuenca del río Copiapó, Chile, con el objetivo de generar información detallada de la … Este estudio se enfoca en caracterizar la granulometría de los sedimentos en depósitos aluvio-coluviales en la cuenca del río Copiapó, Chile, con el objetivo de generar información detallada de la composición granulométrica de los depósitos y aportar en la comprensión del comportamiento de los flujos de detritos (Aluviones). Los flujos de detritos son eventos de remociones en masa, gatillados por eventos de precipitaciones intensas y concentradas, con gran ocurrencia en las zonas áridas de la Cordillera de la Costa y la Cordillera de los Andes. Los flujos de detritos son caracterizados por su alta densidad y composición mayoritariamente de gravas mezcladas con agua, exhiben propiedades de fluidos no-newtonianos y viscoplásticos, lo que los hace especialmente dinámicos y capaces de transportar materiales de gran tamaño. La granulometría, en particular la concentración de sedimentos finos es determinante para las propiedades reológicas de estos flujos, afectando su viscosidad y resistencia al movimiento. Este estudio busca contribuir en la relación entre la composición de sedimentos y la dinámica de los flujos, proporcionando datos granulométricos relevantes para la caracterización de la composición de los sedimentos transportables por los flujos. Palabras - claves: Composición granulométrica, Flujos de detritos, Cuenca del río Copiapó.

Structure, Tectonics, and Hydrocarbon Entrapment Styles of Cauvery Basin, India

2025-06-12

J. Nagaraju , Subhankar Banerjee , Subhash Sharma +1 more | CRC Press eBooks

The Influence of Seasonal Variations in a Continental Lacustrine Basin in an Arid Climate on the Occurrence Characteristics of Gypsum: A Case Study from the Paleogene Bottom Sandstone Member, Tabei Uplift

2025-06-12

Gao Xiaoyang , Wenxiang He , Luxing Dou +4 more | Minerals

The occurrence of gypsum in clastic rocks of continental saline lake basins reflects complex depositional and diagenetic processes. However, its genesis remains relatively understudied. Based on core descriptions and thin-section … The occurrence of gypsum in clastic rocks of continental saline lake basins reflects complex depositional and diagenetic processes. However, its genesis remains relatively understudied. Based on core descriptions and thin-section analyses, this study investigates the occurrence types and genetic mechanisms of gypsum in the Bottom Sandstone Member of the northern Tabei Uplift. Five types of gypsum occurrences are identified: layered gypsum, gypsum clasts, spotted gypsum, gypsum nodules, and a mixed deposition of clastic rocks and gypsum. The mixed deposition of clastic rocks and gypsum includes gypsiferous mudstone, muddy gypsum, gypsiferous mudstone containing muddy clasts, and sandy gypsum. Layered gypsum, spotted gypsum, gypsiferous mudstone, and muddy gypsum mainly result from in situ chemical precipitation during periods of high evaporation and reduced runoff. In contrast, gypsum clasts, gypsiferous mudstone containing muddy clasts, and sandy gypsum reflect processes of transportation and reworking induced by flood events. Seasonal variations in hydrodynamic conditions play a critical role in the formation and distribution of gypsum. During dry periods, surface runoff weakens or ceases, and the salinity of lake water or pore water in clastic deposits increases due to intense evaporation, promoting gypsum precipitation. During flood periods, increased runoff can erode previously formed gypsum, which is subsequently transported and deposited as gypsum clasts. The morphology of gypsum varies with its transport distance. These findings enhance our understanding of clastic–evaporite mixed systems in arid continental lacustrine settings and provide insights into sedimentary processes influenced by seasonal climatic fluctuations.

Navigating the Future Research of the Cauvery Basin

2025-06-12

Sreepat Jain | CRC Press eBooks

Proposed Marine Low-stand Depocenter as a Contributor to the Development of the Namib Sand Sea or Namib Pleistocene Coastal Dune Sheet, Namibia

2025-06-11

Curt D. Peterson | Journal of Geography and Geology

Two isolated dune complexes are developed in the Namibia and southern Angola coastlines in the southwest coast of Africa. They include the very-large Namibia Sand Sea or Namib dune sheet … Two isolated dune complexes are developed in the Namibia and southern Angola coastlines in the southwest coast of Africa. They include the very-large Namibia Sand Sea or Namib dune sheet (35,000 km2 surface area) and two smaller dune sheets or ergs (~4,500 km2 combined surface areas) at the north end of the Skeleton Coast. In this article, 31 across-shelf and across-shore transects are used to test regional factors of 1) shelf width, 2) coastline orientation, 3) coastline elevation, and 4) alongshore eolian deflation corridors for controlling the localized development of the coastal dune sheets. A lack of apparent correspondence between the four factors and the isolated dune complexes prompted a search of the continental shelf for submerged barriers that could have bounded northward alongshore transport of Orange River sand during Pleistocene marine low-stands. Such localized entrapment of littoral sand could have enabled across-shelf sand supply by coast-oblique eolian transport and marine transgression wave transport to the Namib dune sheet and the Skeleton Coast dune sheets. Two mid-shelf paleo-headlands do correspond to the two anomalous dune complexes. They include a Namib paleo-headland with a 28 km projection distance (80&deg; west-of-north offset of the -100 m MSL depth contour) and a north Skeleton Coast paleo-headland with a 14 km projection distance (50&deg; west-of-north offset of the -100 m depth contour). Smaller offsets occur in the -75 m depth contour but not in the -50 m depth contour in both paleo-headlands. The Namib paleo-headland currently extends between -75 and -140 m depth or 60 % of the mid-shelf width. Together with alongshore sand supply from a southern eolian deflation plain corridor, the localized offshore sand supply from the Namib paleo-headland, and an associated low-stand depocenter, might have contributed to the origin of the Namib Sand Sea or Pleistocene coastal dune sheet.

A first chronological framework for fluvial terrace deposits of the Kampar Kanan River, Indonesia

2025-06-06

Yuniarti Yuskar , Melanie Bartz , Christoph Schmidt +3 more | Geochronometria

Drainage evolution in accretionary thrust systems as responses to tectono‐climatic variability: Insights from sandbox modelling

2025-06-04

Qin Li , Yiquan Li , Xianyan Wang +3 more | Earth Surface Processes and Landforms

Abstract Orographic evolution is a dynamic process that unfolds as structural deformation and climate‐driven surface processes interact. In these topographic regions, the intricate ways in which fluvial processes respond to … Abstract Orographic evolution is a dynamic process that unfolds as structural deformation and climate‐driven surface processes interact. In these topographic regions, the intricate ways in which fluvial processes respond to tectonics and climate require a more quantitative investigation. Given the inherent challenges in directly observing these evolutionary processes in nature, here we employ an analogue sandbox modelling approach to explore the dynamic interplay among orographic evolution, structural deformation and climate‐driven surface processes within accretionary thrust systems across a spectrum of tectono‐climatic conditions. Specifically, we investigate how the development of drainage and the evolution of fluvial processes adapt to varying tectonic shortening rate and precipitation. The results show that the formation and orientation of longitudinal rivers are not solely dictated by structural elements such as faults or folds; they are also significantly influenced by the configuration of alluvial fan as modulated by climate‐induced sediment erosion and deposition. It is uncovered that increased precipitation shifts dominant river erosion patterns from predominantly lateral to headward erosion. A notable outcome is the strong positive correlation identified between drainage density ( D d ) and the ratio of crustal shortening rate to rainfall rate (RSR), highlighting the intricate relationship among tectonic activity, hydrology and landscape evolution. In the context of mountain front sedimentation, it demonstrates that material derived from upstream erosional landscape exhibits varying responses to structural and climatic factors. Specifically, bedding patterns are primarily shaped by tectonic forces, whereas climate exerts a controlling influence on particle size distribution. Generally, an acceleration in tectonic deformation rates or a reduction in precipitation rates results in a steeper fan slope. To validate the model's predictive capabilities, select outcomes are compared with natural examples, such as the Longmen Shan, showcasing the high accuracy of the models in replicating real‐world scenarios. Overall, this study contributes novel perspective on the intricate mechanism linking tectonic movements, surface processes and climatic fluctuations, enhancing our comprehension of landscape evolution in tectonically active regions with accretionary thrust systems.

Short communication: Multiscale topographic complexity analysis with pyTopoComplexity

2025-06-03

Larry Syu‐Heng Lai , Adam M. Booth , Alison R. Duvall +1 more | Earth Surface Dynamics

Abstract. pyTopoComplexity is a Python package designed for efficient and customizable quantification of topographic complexity using four advanced methods: two-dimensional continuous wavelet transform analysis, fractal dimension estimation, rugosity index, and … Abstract. pyTopoComplexity is a Python package designed for efficient and customizable quantification of topographic complexity using four advanced methods: two-dimensional continuous wavelet transform analysis, fractal dimension estimation, rugosity index, and terrain position index calculations. This package addresses the lack of open-source software for these advanced terrain analysis techniques essential for modern geomorphology and geohazard research, enhancing data comparison and reproducibility. By assessing topographic complexity across multiple spatial scales, pyTopoComplexity allows users to identify characteristic morphological scales of studied landforms. The software repository also includes a Jupyter Notebook that integrates components from the surface-process modeling platform Landlab (Hobley et al., 2017), facilitating the exploration of how terrestrial processes, such as hillslope diffusion and stream power incision, drive the evolution of topographic complexity over time. When these complexity metrics are calibrated with absolute age dating, they offer a means to estimate in situ hillslope diffusivity and fluvial erodibility, which are critical factors in determining the efficiency of landscape recovery after significant geomorphic disturbances such as landslides. By integrating these features, pyTopoComplexity expands the analytical toolkit for measuring and simulating the time-dependent persistence of geomorphic signatures against environmental and geological forces.

Re-understanding Sedimentary Characteristics of Shallow-water Delta in Funing Formation, Gaoyou Sag, Subei Basin, Eastern China

2025-06-02

Zhenyu Yang , Guiyu Dong , Lianbo Zeng +6 more | Applied Geophysics

Rift marginal coarse-grained sediment gravity flow deposits in the Eocene Dongying Depression, Bohai Bay Basin, China: Balancing tectonic and climatic controls

2025-06-01

Rongheng Tian , Benzhong Xian , Peng Chen +7 more | Petroleum Science

Drainage evolution in response to the growing northeastern Tibetan Plateau: Provenance analysis from drill core of the Jinta Basin (NW China)

2025-06-01

LI Xiao-hua , Dianbao Chen , Pan Baotian +7 more | Geomorphology

The role of the Westward Equatorial Undercurrent in feeding the Seychelles–Chagos Thermocline Ridge upwelling

2025-06-01

Weiqi Hong , Gengxin Chen , Weiqing Han +1 more | Climate Dynamics

THE STRUCTURAL AND TECTONIC BOUNDARIES USING THE GRAVITY METHOD AT THE CRETACEOUS-CENOZOIC MARAJÓ BASIN, EASTERN AMAZONIA COAST

2025-06-01

Cássio da Cruz Nogueira , Cristiano Mendel Martins , Afonso César Rodrigues Nogueira +4 more | Journal of South American Earth Sciences