Sedimentology - Dipartimento di Fisica e Geologiasc570001/SEDIMENTOLOGY/01SED16_… · Clay Clay Hydration Al 2Si 2O 5(OH) 4 5H 22Al(OH) 3 2H 4SiO 4 Clay Clay Hydration Smectite

S. Cirilli: Sedimentology

Sedimentology

S.Cirilli-Sedimentology

Sedimentology (9 cfu)

TeacherProf. Simonetta Cirilli

([email protected])

0755852631


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


III. Sedimentary processes, transport and deposition IV. Sedimentary structures


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



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


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.


Additional References and the Pdf of lectures will be provided by the teacher


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




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


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.


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


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


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


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



grains cement

matrix


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.


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


- 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


Rounding

S. Cirilli

is the degree to which detrital particles have their sharp corners and edges warn away by abrasion


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.


Documents

Sedimentology - Dipartimento di Fisica e Geologiasc570001/SEDIMENTOLOGY/01SED16_… · Clay Clay Hydration Al 2Si 2O 5(OH) 4 5H 22Al(OH) 3 2H 4SiO 4 Clay Clay Hydration Smectite