S. Cirilli: Sedimentology
Sedimentology
S.Cirilli-Sedimentology
Sedimentology (9 cfu)
TeacherProf. Simonetta Cirilli
0755852631
S.Cirilli-Sedimentology
I. Processi di trasporto e deposizione; principali strutture sedimentarie II. Analisi di facies e architetture deposizionali, geometrie e relazioni tra i corpi sedimentari. Relazioni tra subsidenza e sedimentazione. Ambienti sedimentari e modelli di facies IIa. Sistemi deposizionali e sedimenti terrigeno-clastici . depositi continentali: glaciali, eolici, fluviali, lacustri, . depositi costieri, deltizi e di mare basso
Course outlineI. Fundamentals of Sedimentology
II. Rock cycle and Sedimentary rocks: general introduction
Classification of Sedimentary Rocks Siliciclastic sediments and rocks
carbonate sediments and rocks: origin and classification
This part will be briefly presented.
Details on textures, mineralogical composition, rock classification and diagentic processes are matter of the Course on Sedimentary petrography
S.Cirilli-Sedimentology
III. Sedimentary processes, transport and deposition IV. Sedimentary structures
S.Cirilli-Sedimentology
V. Facies, Facies Models and Modern Stratigraphic Concepts
VI. Facies and Sedimentary Environments: Facies analysis and depositional architectures - Siliciclastic dominated systems
Alluvial Fans Desert Lacustrine Deposits River Deposits Delta Sedimentation Coastal Sedimentation The Shore Zone Barrier Islands Tidal Sedimentation Clastic ShallowMarine Shelves Carbonate shallow water platfrom Slope basin Deep-water depositional environments
S. Cirilli: Sedimentology
S.Cirilli-Sedimentology
VII. Facies and Sedimentary Environments: Facies analysis and depositional architectures - Carbonate depositional settings
Shallow water carbonate factories
Peritidal depositional facies
shelf margin distribution facies
Platform slope distribution facies
Basin depositional settings
S.Cirilli-Sedimentology
Testi consigliati
Reading H.G. (2004) third edi t ion- Sedimentary
Environments: Processes, Facies and Stratigraphy .
Blackwell Science. pp.689.
Richard C. Selley (2000)- Applied Sedimentology, Second
Edition . Academic press
Maurice E. Tucker: Geologia del sedimentario
Editore: Flaccovio Dario
Textbooks James N.P & Dalrymple (2010) - Facies Models 4. GEOtext6. Geological Association of Canada Nichols G. (2009) - Sedimentology and Stratigraphy, 2nd Edition, 432 pages, Wiley-Blackwell Additional texts Reading H.G. (2004) third edition- Sedimentary Environments: Processes, Facies and Stratigraphy . Blackwell Science. pp.689. Richard C. Selley (2000)- Applied Sedimentology, Second Edition. Academic press D. Emery and K. Myers (a cura di) (2009) - Sequence Stratigraphy. pp.304. Wiley¸ Moore C.H. (2004) third edition – Carbonate reservoirs- porosity evolution and diagenesis in a sequence stratigraphic framework. Roger. M. Slatt (2007) - Stratigraphic Reservoir characterization for petroleum geologists, Geophysicists and Engineers. Handbook of Petroleum exploration and production, Vol.6, John Cubitt (Ed), Elsevier , pp. 478.
S. Cirilli: Sedimentology
Additional References and the Pdf of lectures will be provided by the teacher
S.Cirilli-Sedimentology
http://www.fisica.unipg.it/~sc570001/
Recognition of ancient sedimentary environments
(depositional systems)
Recognition of sedimentation processes and structures
Analysis/reconstruction of depositional systems
and recognition of their stratigraphic organization
Interpretation of systems organization as a record of relative
sea-level changes
SEDIMENTOLOGY
FACIES ANALYSIS
SEQUENCE STRATIGRAPHY
THIS CO
URSE
S. Cirilli: Sedimentology
S.Cirilli-Sedimentology
S.Cirilli-Sedimentology
Sedimentary Rocks
Sedimentary rocks are those rocks which form at or near the earth's surface primarily through:
Deposition of weathered silicate material by water, wind, or ice (detrital, clastic, terrigenous) Direct inorganic chemical precipitation from water Precipitation by organic processes
S.Cirilli-Sedimentology
Types of Sedimentary Rocks
Clastic (terrigenous or detrital)
Conglomerate or Breccia
Sandstone
Siltstone
Shale
Chemical/biochemical
Carbonate sedimentary rocks (limestones and dolostone)
Evaporites
Siliceous sedimentary rocks
Organic (coals)
Other
S.Cirilli - Sedimentary Petrology
Sedimentary Rocks
Clastic Rock – composed of fragments of preexisting rocks.
Nonclastic Rock – composed of chemical precipitates or biogenic
matter.
Source
Sink
fluvial transport
landslides
glacialerosion
fjords
shoreline
Stratigraphy
shelf break
fans
abyssal plainsor basin floor
openslopes
deltaic & estuarinetrapping
tidewater
glacial runoffstreams
floodplains
primaryproductivity
Coral reefs
weathering
hillslopeerosion
shelf
Sedimentary environments: the framework
The composition of clastic rocks in sedimentary sequences depends to a large extent on the supply of sediments from source areas undergoing weathering and erosion. S.Cirilli-Sedimentology
The physical properties of sedimentary rocks are controlled by the primary sediment composition and changes during burial (diagenesis). We shall here briefly look at the processes producing sediments. S.Cirilli-Sedimentology
• The rock cycle is driven by surface processes: the hydrologic cycle (rainfall, streams, ice), gravity, aqueous chemistry.
• Weathering, erosion and transportation are the processes that form and transport sediments.
• Sedimentation, burial and lithification are the processes that transform weathering products into sedimentary rocks.
S.Cirilli-Sedimentology
Weathering and Sedimentation in the Rock Cycle
Weathering: decomposition of rocks
– The agent and duration of transportation and deposition strongly influence the character and distributions of the sediments
S.Cirilli-Sedimentology
Physical weath. produces fragments Chemical weath. converts exposed rock to soil in place
Erosion and Transportation move dissolved or fragmented material from the source area where weathering is occurring to a depositional environment .
Weathering
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The destruction of rocks at the Earth’s surface by weathering has two fundamental modes of operation:
Physical and Chemical weathering
Physical (or Mechanical) weatheringis the physical breakdown of rocks (from outcrop) into smaller pieces which can then be transported as clastic sediment.
Physical weathering makes loose pieces of rock available for downslope movement by mass wasting or transport in flowing water as suspended or bed load.
Chemical weathering
S.Cirilli-Sedimentology
19
Chemical Weathering: Clay MineralsGenerated strictly as a weather product by many
types of chemical weatheringKAlSi3O8 + 2H+ + 12H2O KAl3Si3O10(OH) 2 + 2K+ + 6H4SiO4
K-spar Muscovite ClayHydrolysis + Hydration
2KAl3Si3O10(OH) 2 + 2H+ + 3H2O 3Al2Si2O5(OH) 4 + 2K+
Muscovite Clay Kaolinite ClayHydrolysis + Hydration
Al2Si2O5(OH) 4 + 5H2O 2Al(OH) 3 + 2H4SiO4Kaolinite Clay Gibbsite Clay
Hydrolysis + HydrationSmectiteYucca Mtn., Nev.
KaolinitePhoto from Dr. Alan Jay Kaufman at http://www.geol.umd.edu/%7Ekaufman/kaufman.html
S.Cirilli-Sedimentology
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grains cement
matrix
S. Cirilli: Sedimentology
These properties collectively make up the texture of a sediment or sedimentary
rock.
Each can be used to infer something of:
The history of a sediment.
The processes that acted during transport and deposition of a sediment.
The behavior of a sediment.
S. Cirilli: Sedimentology
Sedimentary Textures refers as
Grade Scales
Grade scales define limits to a range of grain sizes for a given class (grade) of grain size
They provide a basis for a terminology that describes grain size.
Sets most boundaries to vary by a factor of 2.
e.g., medium sand falls between 0.25 and 0.5 mm.
Sedimentologists use the Udden-Wentworth Grade
Scale
Odmmd )(log2−=φ
Where dO = 1 mm.
After Wentworth, 1922
GRAIN SIZE
A threefold division is used to name clastic sediments and sedimentary rocks (Udden-Wentworth Scale): 1) Gravel-sized grains are greater than 2mm in diameter
2) Sand-sized grains are between 2mm and 1/16mm (63 microns) across 3) Mud (clay and silt) is made of particles less than 63 mm in diameter.
FORSE da METTERE?
S.Cirilli-Sedimentary Petrology
Disk Spheroid
Rod Blade
TEXTURAL FEATURES Shape: defined in terms of closeness to a sphere (similar length of a-, b- and c-axis)
a
cb
After Nichols, 2009 S. Cirilli: Sedimentology
Sorting
Sorting refers to the variation in size of particles making up sediment or sedimentary rocks.
Sorting refers to uniformity of size.
Very-well sorted sediment has only a small range of sizes (i.e: only grains
1.0-2.0 mm in diameter).
Very poorly-sorted sediments shows a huge variation in clast size
S. Cirilli: Sedimentology
- well sorted sediments indicate gradually-changing velocities (like a stream) or
extensive re-working (like a beach); or “selective” current as the wind
- Poorly sorted sediments indicate not selective transport (e.g. gravity flow)
It results from
processes that selectively transport and deposit sediments of particular sizes
Sorting
S. Cirilli: Sedimentology
Rounding
S. Cirilli
is the degree to which detrital particles have their sharp corners and edges warn away by abrasion
S. Cirilli: Sedimentology
TEXTURAL FEATURES Roundness: degree of surface smoothing
After Pettijhon et al., 1987
ROUNDING
Changes in Shape by Transport
Transport of particles by water, wind or flowing glaciers has the potential to cause changes to their shape over time.
Transport by wind or water results in rapid rounding
Fragments might be angular if coming straight from an igneous or metamorphic source, or if moved by ice.
S. Cirilli: Sedimentology
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