Misplaced Pages

#296703

32-538: The Morrissey Formation is the basal unit of the Kootenay Group . It consists of massive, cliff-forming, fine- to coarse-grained sandstone , with minor beds and lenses of conglomeratic sandstone, and rare beds of siltstone , mudstone , carbonaceous mudstone , and coal . The sequence coarsens upward and, in most areas, it can be subdivided into two members, the Weary Ridge Member at the base, and

64-653: A country have become erodible. For example, on the Madagascar high central plateau , which constitutes approximately ten percent of that country's land area, most of the land area is devegetated, and gullies have eroded into the underlying soil to form distinctive gulleys called lavakas . These are typically 40 meters (130 ft) wide, 80 meters (260 ft) long and 15 meters (49 ft) deep. Some areas have as many as 150 lavakas/square kilometer, and lavakas may account for 84% of all sediments carried off by rivers. This siltation results in discoloration of rivers to

96-468: A dark red brown color and leads to fish kills. In addition, sedimentation of river basins implies sediment management and siltation costs.The cost of removing an estimated 135 million m of accumulated sediments due to water erosion only is likely exceeding 2.3 billion euro (€) annually in the EU and UK, with large regional differences between countries. Erosion is also an issue in areas of modern farming, where

128-432: A grain, such as pits, fractures, ridges, and scratches. These are most commonly evaluated on quartz grains, because these retain their surface markings for long periods of time. Surface texture varies from polished to frosted, and can reveal the history of transport of the grain; for example, frosted grains are particularly characteristic of aeolian sediments, transported by wind. Evaluation of these features often requires

160-458: A higher density and viscosity . In typical rivers the largest carried sediment is of sand and gravel size, but larger floods can carry cobbles and even boulders . Wind results in the transportation of fine sediment and the formation of sand dune fields and soils from airborne dust. Glaciers carry a wide range of sediment sizes, and deposit it in moraines . The overall balance between sediment in transport and sediment being deposited on

192-426: A hydrodynamic sorting process within the marine environment leading to a seaward fining of sediment grain size. One cause of high sediment loads is slash and burn and shifting cultivation of tropical forests. When the ground surface is stripped of vegetation and then seared of all living organisms, the upper soils are vulnerable to both wind and water erosion. In a number of regions of the earth, entire sectors of

224-672: A maximum thickness of about 1,355 metres (4,450 ft), and it thins eastward. The Kootenay Group conformably overlies the marine shales of the Fernie Formation. In most areas it is disconformably overlain by the nonmarine strata of the Blairmore Group , although in some western areas the contact may be conformable. North of the North Saskatchewan River the Kootenay Group grades into

256-470: A result, can cause exposed sediment to become more susceptible to erosion and delivery to the marine environment during rainfall events. Sediment can negatively affect corals in many ways, such as by physically smothering them, abrading their surfaces, causing corals to expend energy during sediment removal, and causing algal blooms that can ultimately lead to less space on the seafloor where juvenile corals (polyps) can settle. When sediments are introduced into

288-945: Is unconformably overlain by the Cadomin Formation . Its correlation south of the Canada-United States border in Montana is uncertain. Kootenay Group The Kootenay Group , originally called the Kootenay Formation , is a geologic unit of latest Jurassic to earliest Cretaceous age in the Western Canada Sedimentary Basin that is present in the southern and central Canadian Rockies and foothills. It includes economically important deposits of high-rank bituminous and semi-anthracite coal , as well as plant fossils and dinosaur trackways . The strata of

320-551: Is expected to be delivered to the outlet of the river. The sediment transfer and deposition can be modelled with sediment distribution models such as WaTEM/SEDEM. In Europe, according to WaTEM/SEDEM model estimates the Sediment Delivery Ratio is about 15%. Watershed development near coral reefs is a primary cause of sediment-related coral stress. The stripping of natural vegetation in the watershed for development exposes soil to increased wind and rainfall and, as

352-581: Is measured on a log base 2 scale, called the "Phi" scale, which classifies particles by size from "colloid" to "boulder". The shape of particles can be defined in terms of three parameters. The form is the overall shape of the particle, with common descriptions being spherical, platy, or rodlike. The roundness is a measure of how sharp grain corners are. This varies from well-rounded grains with smooth corners and edges to poorly rounded grains with sharp corners and edges. Finally, surface texture describes small-scale features such as scratches, pits, or ridges on

SECTION 10

#1732788041297

384-827: The Canadian Rockies in Alberta. The Morrissey Formation abruptly but conformably overlies the "Passage Beds" at the top of the Fernie Formation , and is in turn abruptly but conformably overlain by the Mist Mountain Formation . To the north in the vicinity of the North Saskatchewan River it interfingers with and grades into the Nikanassin Formation . To the east it was truncated by pre- Aptian erosion and

416-664: The Nikanassin Formation . To the south it may correlate with the upper part of the Morrison Formation in Montana. It was originally mis-correlated with the Kootenai Formation which underlies the Morrison. Sediment Sediment is a naturally occurring material that is broken down by processes of weathering and erosion , and is subsequently transported by the action of wind, water, or ice or by

448-639: The Kootenay Group were originally described as the Kootenay Formation. D.W. Gibson revised the sequence as the Kootenay Group and defined it as encompassing the stratigraphic interval between the Jurassic Fernie Formation and the Lower Cretaceous Blairmore Group . He subdivided it into three formations as shown below and designated a type section for each of the formations, thus eliminating

480-653: The Moose Mountain Member at the top: The Morrissey sediments were derived from newly rising mountain ranges to the west and transported eastward by river systems. They were deposited along the edge of the Western Interior Seaway in extensive littoral , deltaic and beach environments. Thin beds of carbonaceous mudstone and coal near the top of the formation may have been deposited in interdune , lacustrine or swale environments. Fossils , including microfossils , are very rare in

512-688: The Morrissey Formation, but the Mist Mountain Formation includes plant fossils and dinosaur trackways , and the Elk Formation includes plant fossils, trace fossils and bivalves . The Kootenay Group is present in the front ranges and foothills of the Canadian Rockies in southeastern British Columbia and southwestern Alberta. It extends from the Canada–US border to north of the North Saskatchewan River . It has

544-406: The Morrissey Formation. Several genera of molluscs (e.g., Oxytoma , Modiolus , and possibly Pachyteuthis ) have been collected from the Weary Ridge Member. A single impression and a few fragments of the ammonite Titanites occidentalis , which have been recovered from the top of the Moose Mountain Member, indicate a Late Jurassic (Portlandian) age. Impressions of logs are also known from

576-600: The bed is given by the Exner equation . This expression states that the rate of increase in bed elevation due to deposition is proportional to the amount of sediment that falls out of the flow. This equation is important in that changes in the power of the flow change the ability of the flow to carry sediment, and this is reflected in the patterns of erosion and deposition observed throughout a stream. This can be localized, and simply due to small obstacles; examples are scour holes behind boulders, where flow accelerates, and deposition on

608-579: The body of water. Terrigenous material is often supplied by nearby rivers and streams or reworked marine sediment (e.g. sand ). In the mid-ocean, the exoskeletons of dead organisms are primarily responsible for sediment accumulation. Deposited sediments are the source of sedimentary rocks , which can contain fossils of the inhabitants of the body of water that were, upon death, covered by accumulating sediment. Lake bed sediments that have not solidified into rock can be used to determine past climatic conditions. The major areas for deposition of sediments in

640-417: The coastal regions of the ocean, the proportion of land, marine, and organic-derived sediment that characterizes the seafloor near sources of sediment output is altered. In addition, because the source of sediment (i.e., land, ocean, or organically) is often correlated with how coarse or fine sediment grain sizes that characterize an area are on average, grain size distribution of sediment will shift according to

672-422: The edges and corners of particle are. Complex mathematical formulas have been devised for its precise measurement, but these are difficult to apply, and most geologists estimate roundness from comparison charts. Common descriptive terms range from very angular to angular to subangular to subrounded to rounded to very rounded, with increasing degree of roundness. Surface texture describes the small-scale features of

SECTION 20

#1732788041297

704-510: The flow. In geography and geology , fluvial sediment processes or fluvial sediment transport are associated with rivers and streams and the deposits and landforms created by sediments. It can result in the formation of ripples and dunes , in fractal -shaped patterns of erosion, in complex patterns of natural river systems, and in the development of floodplains and the occurrence of flash floods . Sediment moved by water can be larger than sediment moved by air because water has both

736-857: The force of gravity acting on the particles. For example, sand and silt can be carried in suspension in river water and on reaching the sea bed deposited by sedimentation ; if buried, they may eventually become sandstone and siltstone ( sedimentary rocks ) through lithification . Sediments are most often transported by water ( fluvial processes ), but also wind ( aeolian processes ) and glaciers . Beach sands and river channel deposits are examples of fluvial transport and deposition , though sediment also often settles out of slow-moving or standing water in lakes and oceans. Desert sand dunes and loess are examples of aeolian transport and deposition. Glacial moraine deposits and till are ice-transported sediments. Sediment can be classified based on its grain size , grain shape, and composition. Sediment size

768-539: The inside of meander bends. Erosion and deposition can also be regional; erosion can occur due to dam removal and base level fall. Deposition can occur due to dam emplacement that causes the river to pool and deposit its entire load, or due to base level rise. Seas, oceans, and lakes accumulate sediment over time. The sediment can consist of terrigenous material, which originates on land, but may be deposited in either terrestrial, marine, or lacustrine (lake) environments, or of sediments (often biological) originating in

800-406: The long, intermediate, and short axis lengths of the particle. The form ψ l {\displaystyle \psi _{l}} varies from 1 for a perfectly spherical particle to very small values for a platelike or rodlike particle. An alternate measure was proposed by Sneed and Folk: which, again, varies from 0 to 1 with increasing sphericity. Roundness describes how sharp

832-435: The marine environment include: One other depositional environment which is a mixture of fluvial and marine is the turbidite system, which is a major source of sediment to the deep sedimentary and abyssal basins as well as the deep oceanic trenches . Any depression in a marine environment where sediments accumulate over time is known as a sediment trap . The null point theory explains how sediment deposition undergoes

864-438: The need for a type section for the group. The Kootenay Group is an eastward-thinning wedge of sediments derived from the erosion of newly uplifted mountains to the west. The sediments were transported eastward by river systems and deposited in a variety of river channel , floodplain , swamp , coastal plain , deltaic and shoreline environments along the western edge of the Western Interior Seaway . Fossils are rare in

896-491: The relative input of land (typically fine), marine (typically coarse), and organically-derived (variable with age) sediment. These alterations in marine sediment characterize the amount of sediment suspended in the water column at any given time and sediment-related coral stress. In July 2020, marine biologists reported that aerobic microorganisms (mainly), in " quasi-suspended animation ", were found in organically-poor sediments, up to 101.5 million years old, 250 feet below

928-473: The removal of native vegetation for the cultivation and harvesting of a single type of crop has left the soil unsupported. Many of these regions are near rivers and drainages. Loss of soil due to erosion removes useful farmland, adds to sediment loads, and can help transport anthropogenic fertilizers into the river system, which leads to eutrophication . The Sediment Delivery Ratio (SDR) is fraction of gross erosion (interill, rill, gully and stream erosion) that

960-445: The surface of the grain. Form (also called sphericity ) is determined by measuring the size of the particle on its major axes. William C. Krumbein proposed formulas for converting these numbers to a single measure of form, such as where D L {\displaystyle D_{L}} , D I {\displaystyle D_{I}} , and D S {\displaystyle D_{S}} are

992-659: The top of Moose Mountain Member. The Morrissey Formation extends from the Flathead River area of southeastern British Columbia near the Canada–United States border to the North Saskatchewan River in western Alberta. It has a maximum recorded thickness of 80 metres (260 ft) near Mist Mountain and the Highwood Pass in Alberta, and it thins eastward, reaching a zero edge along the eastern foothills of

Morrissey Formation - Misplaced Pages Continue

1024-494: The use of a scanning electron microscope . Composition of sediment can be measured in terms of: This leads to an ambiguity in which clay can be used as both a size-range and a composition (see clay minerals ). Sediment is transported based on the strength of the flow that carries it and its own size, volume, density, and shape. Stronger flows will increase the lift and drag on the particle, causing it to rise, while larger or denser particles will be more likely to fall through

#296703