Sedimentology S.Cirilli-Sedimentology S. Cirilli: Sedimentology Sedimentology (9 cfu) Teacher Prof. Simonetta Cirilli ([email protected]) 0755852631 S.Cirilli-Sedimentology Course outline I. 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 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 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 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 Testi consigliati 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 Maurice E. Tucker: Geologia del sedimentario Editore: Flaccovio Dario Additional References and the Pdf of lectures will be provided by the teacher http://www.fisica.unipg.it/~sc570001/ S.Cirilli-Sedimentology Interpretation of systems SEQUENCE organization as a record of relative STRATIGRAPHY sea-level changes Analysis/reconstruction of depositional systems and recognition of their stratigraphic FACIES ANALYSIS organization THIS COURSE Recognition of ancient sedimentary environments (depositional systems) SEDIMENTOLOGY Recognition of sedimentation processes and structures 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-Sedimentology Sedimentary Rocks Clastic Rock – composed of fragments of preexisting rocks. Nonclastic Rock – composed of chemical precipitates or biogenic matter. S.Cirilli - Sedimentary Petrology Sedimentary environments: the framework Source glacial erosion glacial runoff weathering streams hillslope erosion fjords landslides Coral reefs deltaic & estuarine tidewater trapping fluvial transport primary floodplains productivity open shoreline slopes shelf shelf break abyssal plains Sink or basin floor Stratigraphy fans 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 Weathering and Sedimentation in the Rock Cycle • 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 Physical weath. produces fragments Weathering: decomposition of rocks Chemical weath. converts exposed rock to soil in place – The agent and duration of transportation and deposition strongly influence the character and distributions of the sediments S.Cirilli-Sedimentology 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) weathering is 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. S.Cirilli-Sedimentology Chemical weathering S.Cirilli-Sedimentology Chemical Weathering: Clay Minerals Generated strictly as a weather product by many types of chemical weathering + + KAlSi3O8 + 2H + 12H2O KAl3Si3O10(OH) 2 + 2K + 6H4SiO4 K-spar Muscovite Clay Hydrolysis + Hydration + + 2KAl3Si3O10(OH) 2 + 2H + 3H2O 3Al2Si2O5(OH) 4 + 2K Muscovite Clay Kaolinite Clay Hydrolysis + Hydration Al2Si2O5(OH) 4 + 5H2O 2Al(OH) 3 + 2H4SiO4 Kaolinite Clay Gibbsite Clay Hydrolysis + Hydration Smectite Yucca Mtn., Nev. Photo from Dr. Alan Jay Kaufman at http://www.geol.umd.edu/%7Ekaufman/kauf man.html Kaolinite 19 S.Cirilli-Sedimentology ΜϋϊϏϓϋϔϚχϘϟΐϋϕϒϕύϟ ΍ϋϖͨΎχϘϚώΜωϏͨͥΗχϚͨΌϋϔϚϘχϒΞϔϏϜͨ ΙϘϋϖχϘϋϊψϟ΍ϘͨΊϔϊϘϋϝΝͨΕϏϔ S.Cirilli-Sedimentology cement grains 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 Sets most boundaries to vary Sedimentologists use the by a factor of 2. Udden-Wentworth Grade Scale They provide a basis for a terminology that describes d(mm) grain size. φ = −log2 dO Where d = 1 mm. e.g., medium sand falls between O 0.25 and 0.5 mm. GRAIN SIZE A threefold division is used to name clastic sediments and sedimentary rocks (Udden- FORSE da METTERE? 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. After Wentworth, 1922 S.Cirilli-Sedimentary Petrology TEXTURAL FEATURES Shape: defined in terms of closeness to a a sphere (similar length of a-, b- and c- axis) c b Disk Spheroid Blade Rod 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 Sorting It results from processes that selectively transport and deposit sediments of particular sizes - 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) S. Cirilli: Sedimentology Rounding is the degree to which detrital particles have their sharp corners and edges warn away by abrasion S. Cirilli S. Cirilli: Sedimentology TEXTURAL FEATURES ROUNDING Roundness: degree of surface smoothing After Pettijhon et al., 1987 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.