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Laboratorio di Sedimentoogia e Stratigrafia Gianluca Frijia 2020-2021 Coral reef surrounding a volcanic island
Laboratorio di Sedimentoogia e Stratigrafia
Gianluca Frijia2020-2021
Coral reef surrounding a volcanic island
Reference Books and course material
• Leeder, M. (2015) 2nd edition. Sedimentology and Sedimentary basins. 768 p. Wiley-Blackwell.
• Tucker, M.E.(2010). Geologia del Sedimentario. Dario Flaccovio
Editore.Palermo.
• Nichols, G. (2009). Sedimentology and Stratigraphy. Wiley-Blackwell, 355 pp.
• Tucker, M.E. (2001). Sedimentary Petrology: An Introduction to the Origin of Sedimentary Rocks. Blackwell, 262 pp.
Extra material provided by the instructor
Struttura del corso e esami
Teoria: 2h (Tutti)
Lab: 2h (Gruppi ??)
Martedi, Mercoledi,giovedi
Data esami: esame intercorso (data da stabilire) e esame orale finale.
Orario di ricevimento: Martedi, Mercoledi12-13
Course outline:
1. Origin and classification of sedimentary rocks
2. Principles of Hydrodinamics and trasport
3. Sedimentary structures
4. Depositional environments
5. Stratigraphy (principles, chrono-bio-litho-magneto-
chemo-sequence-cyclo-)
Sedimentology and Stratigraphy in Earth Sciences
Two disciplines often considered separately in the past. Now increasingly combined in textbooks, research and economic applications.
Sedimentology is primarily concerned with formation of sedimentary rocks but as soon beds of rocks are seen in terms of spatial and temporal relationships, we talk about Stratigraphy
Similarly, if a Stratigrapher wishes to interpret layers of rocks in terms or environments, the study is considered as Sedimentological.
Sedimentation – scientific study of only modern
sediments and sedimentary processes that excludes
subjects of diagenesis (fluids dynamic,sed transport,sed
structures)
Sedimentology & Stratigraphy
Sedimen-tation
Sedimentary
Petrology
Stratigraphy
FaciesAnalysis
Sedimentary Petrology – petrographic interpretation
and genetic interpretation of sedimentary rocks
(climate,paleoceanography, diagenesis,
porosity/permeability)
Sedimentology & Stratigraphy
Sedimen-tation
Sedimentary
Petrology
Stratigraphy
FaciesAnalysis
Stratigraphy – study of strata and their spatial
organization, paleogeography, paleoecology, and the
sequence of geologic events
Sedimentology & Stratigraphy
Sedimen-tation
Sedimentary
Petrology
Stratigraphy
FaciesAnalysis
Facies analysis– study of modern and fossils
dep.environments, predictive models, sea-level
changes,paleoclimate,tectonics
Sedimentology & Stratigraphy
Sedimen-tation
Sedimentary
Petrology
Stratigraphy
FaciesAnalysis
the vertical and lateral relationships
of sedimentary strata;
the origin of the sediments that
make up the strata; and
both the mechanisms of transport
and the environment of deposition
Ability to predict the depositional
environments evolution through time
and space
Goal of Sedimentology and stratigraphy
Enable the geologist (YOU) to interpret
• classification of rocks
• Formation, transport and deposition of sediments
• describe sedimentary strata
• Interpretation of environment of sedimentation
• spatial and temporal patterns in sediment deposition
Goals of the courseLearn the bases for interpreting sedimentary deposits in terms of
So..let s get started:
What is a sediment?
YOUR DEFINITION?
What is a sediment?
Any kind of particle that was in suspension in a fluid (air,
water) and that was deposited to form a geological layer, a
rock, after compaction
A sediment is thus formed of particles that are not
cemented: it can ‘flow’
Sedimentary deposits are the final result of weathering, erosion and deposition of particles which differ in origin, size, shape and
composition.
Origin and transport of sedimentary material
Origin and transport of sedimentary material
Processes of formation of a Sedimentary Clastic Rock:
Weathering and Erosion– mechanical & chemical
Transport– by gravity, water, air, ice, sediment-water mixtures.
Sedimentation–Different environments (beaches, dunes, basins, etc)
Burial and Diagenesis (Lithification)– loose sediment turns to solid rock
Sedimentary rocks
Origin of sediment:
1) erosion or older rocks
2) Material originated by volcanic eruptions (e.g. ash)
3) Supersatured solutions (chemical precipitation)
4) Action of organisms (direct or indirect)
Erosion and Weathering
Weathering Erosion
Erosion and Weathering
Weathering: reaction of minerals to conditions at the Earth’s
surface
Erosion: transport of material (often previously weathered) by
gravitational forces (wind, ice, water)
Denudation: sum of mobilization and transport processes of
material at the Earth’s surface
Erosion and Weathering
Weathering: Transformation of minerals (in physical and
chemical equilibrium with their conditions of formation) as a
response to new surface conditions
Dense, fresh, massive rocks are transformed in lighter, less
dense and massive material with a lower mechanical
resistance
Hinderer, 1999
Weathering
Breaking down of rocks and other
materials on the Earth’s surface
• Slow, continuous process
• effects are not easily observed
Two Types
Mechanical: rocks are broken down into
smaller pieces but their chemical
makeup does not change
Chemical: chemical makeup or rocks is
changed as rocks are broken down
Mechanical Weathering
Causes:
Temperature: rocks expand/contract (cycle), causes
exfoliation
Frost wedging: water seeps into small craks, freezes
and expand which enlarge cracks
Abrasion: wearing away of rocks by particles carried
by wind water etc.
Salt grow: salt in cracks by water evaporation
Organic activity: caused by living things (e.g. Plant
roots)
Mechanical weathering: Gelifraction-Frosting
Phase transition of liquid water into -> volume
change of +9%. Cryofracturing or gelifraction
is important if the rock is totally water
saturated and compressible air is absent
www.kesgrave.suffolk.sch.uk
http://www.alexstrekeisen.it/english/sedi/weathering.php
Erosion and Weathering
Some common example:
www.geosci.unc.edu
http://uts.cc.utexas.edu/~rmr/er.html
Tioga pass (CA, USA) Enchanted rock (Texas, USA)
Mechanical weathering: Decompression, dilatation and exfoliation
Erosion and Weathering
Weathering: Biological activity
Root wedging
As roots grow, they apply pressure to their
surroundings, and can push joints open in a
process known as root wedging
Animal attack
burrowing creatures, from earthworms to
gophers, push open cracks and move rock
fragments. in the past century, humans have
become perhaps the most energetic agent of
physical weathering on the planet.
Chemical Weathering
Water: Chemical weathering refers to the many chemical
reactions that alter or destroy minerals when rock comes in contact
with water solutions and/or air. Common reactions involved in
chemical weathering include the following:it dissolves minerals that
hold rocks together, forms acids when mixed with gases or acid
compounds, combines with minerals to make new minerals
(combine with feldspar to make clay)
(Bio-) chemical alteration
• Temperature: chemical reactivity doubles each 10°C
• Water as solvent
• Oxygen (oxydation), CO2 (acid, pH=5.6), H+ (pH, hydrolyse),
organic complexes (chelation)
• Surface of reaction: 1m3-> 6m2 but if divided into cubes of
1mm3 -> 6000m2
• Life: appearance of terrestrial plants in the Devonian may have
speeded up biochemical alteration by 7 times (R. Berner, Yale
Uni, pers. com to K. B. Föllmi)
• Mineral stability: olivine, anorthite, pyroxene, amphibole, albite,
biotite, orthose, muscovite, clays, oxydes (Si, Al, Ti, Zr, Fe, Mg)
What affects Weathering?
Rock composition (diff. rocks weather differently).Stable rock resists chemical
weathering
Climate: ex. Limestone Ok in warm/dry climate, when wet-weak acids weather
Time exposed on surface: old,, unexposed rocks no big changes
New exposed rocks weather quickly
Surface area: when rock is a small pieces more surface area is available for
weathering
Ph: Hydrolysis requires hydrogen ions. Thus pH, is a limiting factor for them.
Note: Whereas rain water (and consequently fresh water) is slightly acidic (pH
between 4 and 6.5), ocean water is slightly alkaline (roughly pH 8). Thus
chemical weathering is more prevalent on land.
Allen, 1997
Weathering(Bio-) chemical alteration
Bo
wen
’s r
ed
ucti
on
seri
es
Go
ldic
h’s
weath
erin
g s
erie
sFast
Slow
White et al., 1992
WeatheringProcess-oriented model of the weathering system
FASTSLOWweathering rate
Erosion and WeatheringF
reie
Un
ive
rsitä
tB
erlin
Time
Climate
Topography
Cynetic of
chemical
reaction (T, fluids
types,type of reagents, contact
surface )
Mineralogical
composition
What effects the weathering? To sum up:
Weathering? To sum up:
Weathering? To sum up:
Erosion
Process by which weathered rock and soil particles are moved
from one place to another. Erosion carries away the products of
weathering
The final stage in the erosion process is when sediments are laid
down in the new location (Deposition)
Erosion moves material, Deposition builds new features
Agents of Erosion
Gravity (pull rocks and soil down slopes.E.g.
Landslides,Avalanches)
Wind (major agent in hot,dry climate or little vegetation)
Running water (more powerful than wind to move particles.faster
it moves greater is erosion. Erosion in small channels on slide of
slope is called rill erosion, when channel become deep it becomes
gully erosion)
Glaciers (capacity to carry HUGE rocks over great distance)
Waves
Transport:
• Gravity
• Fluids
• Wind
• Turbidity flows
• Ice
Origin and transport of sedimentary material
Sedimentary rocks cycle
From Source…to Sink
From catchment area to depositional environments
Upstream: mainly production
and mobilization of sediments
from pre-existing formations
(crystalline or sedimentary)
Catchment / river segment:
transport, deposition and
reworking
Shelf segment:
transport, deposition and
reworking
Oceanic basin:
permanent storage
(a) Global Rainfall Erosivity map (spatial resolution 30 arc-seconds). Erosivity classes correspond to quantiles.
Map generated with ESRI ArcGIS ver. 10.4 (http://www.esri.com); (b) number and cumulative percentage of
GloREDa stations grouped by erosivity; (c) mean erosivity by continent; (d) mean erosivity by climate zone.
The Risk of Human-Induced Water Erosion map is based on an overlay of the
global Water erosion map and a global population density map.
U.S. Dpt of Agriculture
