Sed and Strat
EARTH SURFACE PROCESSES AND SEDIMENTATION! 2/27 Lecture 7- Exposure: Weathering and the Sediment Factory 3/04 Lecture 8 - Rivers and Landscapes 3/06 Lecture 9 - Waves (not Tides) 3/11 Lecture 10- Shorelines and Tides 3/13 Lecture 11 - Preservation: Into the Rock Record (HW #3 due, HW#4 assigned) 3/18 Lecture 12 Sedimentation and Stratigraphy (readings) 3/20 Lecture 13- Some other sedimentary environments 3/21 Mid-term (take home, due Monday March 31)
Terms/Concepts! Sedimentology the study of the formation, transport and deposition of material which accumulates as sediment in continental and marine environments eventually forms sedimentary rocks; focuses primarily on facies and depositional environments (how were sediments/sedimentary rocks formed?)!! Stratigraphy the study of rocks to determine deposition order and timing of events in Earth history; focuses on the larger-scale strata and Earth history; focuses on when and where sediments/ sedimentary rocks formed.!!!
Plan-form Depositional Coastal Systems!
Goal: Interpret the geologic past! History of Earth and its life can be read as a sequence of events recorded in sedimentary deposits (rocks)! Basis in the principle of uniformitarianism! the geologic time scale! records major geologic events! notes appearances of varied forms of life!
Sedimentary Facies! facies: the total textural, compositional and structural characteristics of a sedimentary deposit resulting from accumulation and modification in a particular setting. grain size, sorting, rounding lithology sedimentary structures bedding type fossil assemblages
Sedimentary structures! Sedimentary structures occur at very different scales, from less than a mm (thin section) to 100s 1000s of meters (large outcrops-used to reconstruct depositional environments! Microforms (e.g., ripples)! Mesoforms (e.g., dunes)! Macroforms (e.g., bars)! Laminae and beds are the basic sedimentary units that produce stratification; the transition at 10 mm! Normal grading is an upward decreasing grain size within a single lamina or bed (associated with a decrease in flow velocity), as opposed to reverse grading! Fining-upward successions and coarsening-upward successions are the products of vertically stacked individual beds!
Depositional environments!
Ripples!
Barchan Dunes!
Barchan Dunes!
Transverse Dunes!
Vegetation and Dunes!
Parabolic Dunes!
Evaporation!
Mudcracks!
Cross-bedding!
Bedding!
Grading!
Flow Regimes
Hummock and Swale Dumas & Arnott, 2006
Incision and Infilling!
Ice Contact! Dumas & Arnott 2006
Offshore Grading!
The study of sedimentary rock sequences! Involves the relationships to other sedimentary rock units above, below, and laterally! The changes in sequences record:!! Tectonic activity! Stratigraphy!! Rising or falling sea level!! Climate changes!
Gilbert Delta!
Gilbert Delta!
Gilbert Delta!
Transgression and Regression! Changing (of relative) sea level greatly influences distribution of depositional facies! Also balanced by sediment input!! Transgression:! Rising sea level: the ocean rises and covers the continental margin! Shoreline moves towards continental interior! Regression! Relative lowering of sea level! Shoreline migrates away from the continental interior!
Transgression! Rising sea level = shoreward migration of sedimentary facies! Deeper-water sediment deposited over shallower! Mud facies is superimposed over sandy beach facies! Fining upward (in sequences)!
Strat Movie! Play CLASTICSYSTEMTRACTS.MOV!
Clastic Depositional Systems Terrestrial Transitional Marine
Clastic Depositional Systems Terrestrial Transitional Marine
Clastic Depositional Systems Terrestrial Transitional Marine
sediment supply vs. rate of sea level rise!
Regression types! After Catuneanu, 2002 Normal! Forced!
Coast Types
Whether transgression or regression occurs controls the preservation potential and vertical succession of environments like barrier islands
Bayhead Delta!
Chenier Plain!
Capes and Shoals!
Mallinson et al., 2010! Paleovalleys!