Sedimentology Sedimentary Particles

1. Sedimentology Sedimentary
Particles
Lecture 1
Jyoti Khatiwada
Roll no 10

2. types of sedimentary particles
• 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, and/or by 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 be deposited by sedimentation and if buried this may
eventually become sandstone and siltstone, ( sedimentary
rocks).
• 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.

3. Solid breakdown Particles
• Sedimentary deposits are assemblages of individual grains, or particles,
which compose the framework of modern sand or mud deposits (beach,
flood plain) and its lithified equivalent (sedimentary rock). The goal of this
laboratory exercises is to provide you with an overview of some of the
many type of particles commonly found in Sedimentary Rocks, from
terrigenous and marine sediments.
• A. TERRIGENOUS/ BREAKDOWN PARTICLES. Terrigenous sedimentary
particles can be divided into 2 groups (Friedman and Sanders, 1978):
• 1) solid breakdown products of older deposits and
• 2) materials that are not solid breakdown deposits.
• Group 2 consists of volcanoclastic materials and those transported in
water solution and deposited at the site of accumulation by biologic
secretion or chemical precipitation.

4. Solid breakdown particles
• Those eroded from the land are terrigenous particles
and fall into 2 groups:
• a) inorganic terrigenous materials and
• b) carbonaceous materials. Most terrigenous particles
come from bedrock. Inorganic terrigenous particles
include: rock fragments, quartz, feldspar and heavy
minerals originally derived from igneous or
metamorphic rocks.
• Carbonaceous terrigenous particles include
• 1) solid carbonaceous materials reworked from older
strata, and
• 2) modern plant detritus. Breakdown particles are
also referred to as Siliciclastic.

5. Teachers slide solid breakdown products
• Inorganic particles =Rock fragments , Quartz,
Feldspar, Layered lattic silicates , Heavy
minerals , clay minerals and mica
• Particles not breakdown= Pyroclastic (erupted
bombs blocks, tepras, etc) and Authegenic (
Skeletal debris, Silicious skeletal debris,
Phosphatic skeletal debris, Non Skeletal
Calcium carbonate debris, Evaporites)
• Clay mineral conversion ( feldspsr to Kaolinite
),(Montomorolite to clay minerals)

6. • Clastic sedimentary rocks such
as breccia,conglomerate, sandstone, siltstone,
and shale are formed from mechanical weathering
debris.
• Chemical sedimentary rocks, such as rock salt, iron
ore, chert, flint, some dolomites, and
some limestones, form when dissolved materials
precipitate from solution
• Terrigenous sediments (siliciclastics) in the oceans are
concentrated on continental margins (decreasing
abundance into the basin) and in the deep sea, as red
clay. Because sediments of continental margins are
derived from land and sea, they are termed
hemipelagic sediments- essentially they are pelagic
sediments diluted by fluvial and Aeolian sediments.
The deep sea red (often brownish) terrigenous
sediments contain no or very rare calcareous
microfossils.

7. particles that are not solid breakdown
products of older sediment deposit
• Pyroclastic materials
• Authigenic particles
• Pyroclastic material is another name for a cloud
of ash, lava fragments carried through the air, and
vapor. Such a flow is usually *very* hot, and
moves *rapidly* due to buoyancy provided by
the vapors. Pyroclastic flows can
extend miles from the volcano,
and devastate life and property
within their paths.

8. Authigenic particle –Non solid
breakdown particle
• Authegenic = formed where found —used of mineral particles of
rocks formed by crystallization in the place they occupy —opposed to
allothogenic
• AUTHIGENIC. Authigenic sediments are those chemically
precipitated from seawater. Common examples include manganese
nodules and Glauconite (green sands).
• Precipitation of minerals on or within the sediments of the sea floor
generally results from supersaturation of the element or compound
required to form the mineral. Because authigenic mineral
accumulation rates are often less than 1 mm/1000 years, resulting
sediments are common only where terrigenous and biogenic
accumulation rates are nearly zero. In many cases, crusts of
authigenic minerals form where bottom currents prevent the
accumulation of other sediments.

9. Examples of authegenic
• Barite (BaSO4) occurs in crystalline or microcrystalline phases or as
replacement material in fecal pellets in deep-sea sediments. Barite
concentrations average 1% in deep sea sediments, but can make up as
much as 10% by weight of the carbonate-free fraction on the East Pacific
Rise, where it is associated with hydrogenous iron oxide. Most (80%) of
the elemental barite in the oceans enters through rivers, about 20%
comes from hydrothermal vents
• Evaporite-Glauconite is a well-ordered K- and Fe-rich mica-structure clay
mineral. It occurs as flakes or pellets, and may occur as infilling in
foraminiferal shells and sponge spicules. It may occur in fissures in
feldspars, as crusts on phosphorite nodules, and as replacement mineral in
coproliths. The color is usually blue-green, but this depends on the original
clay-type and chemical composition
• Marine Phosphates concentrations are typically very low within the
euphotic zone of the oceans because phytoplanktons extract phosphate
nutrients to photosynthesize organic matter. Vertebrates also concentrate
phosphate into apatite, from which their bones are constructed.
• Organic-Rich Sediments is measured in sediment as total organic carbon
(TOC) or particulate organic matter (POC) which in ocean water is primarily
living organisms or the remains of dead organisms. Upon the death of an
organism, its remains are subjected to chemical and bacterial degradation
processes

10. The End
• Thank You