GEOL1002 Lecture Notes - Lecture 17: Viscosity, Hematite, Diagenesis
5 Jul 2018
School
Department
Course
Professor
Sands and Depositional Environments
Every feature of a sediment gives us a clue…
Sediments, through their properties, can reveal us their origin, transport, deposition and
diagenetic histories.
Observe and document: Unit morphology, composition, grain size, grain sorting, structures
and fossils.
Interpret: Weathering and erosion history, transport mechanism/energy, transport direction
and cyclicity.
Reconstruct: Provenance, transport medium and environment of deposition.
Sedimentary environments
Glacial deposits
Massive units
Very poorly sorted
Very compositionally diverse
Randomly orientated clasts
Striations and polishing
Alluvial fans
Common at the break in slope between upland and low-land areas
Gravity and water movement typically result in very high energy systems that lose
energy very rapidly
Poorly to well stratified
May show channels
Matrix and grain supported
Poorly sorted
Sub-angular clasts
Fluvial deposits
Erosive channel morphology
Ripples
Laminations
Interbedded with over bank fines
Sometimes contains fossils
Unidirectional water movement
Variable flow rates and velocities
Variable energy along river course
Channels migrate
As rivers meander and migrate they sweep back and forth depositing cyclical
packages of coarse and fine sediments
Lacustrine deposits
Fine laminations
Fine grained and well sorted
Wave ripples possible
Freshwater fossils
Predominantly low-energy
Relatively shallow with nutrient rich conditions
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Document Summary
Every feature of a sediment gives us a clue . Sediments, through their properties, can reveal us their origin, transport, deposition and diagenetic histories. Observe and document: unit morphology, composition, grain size, grain sorting, structures and fossils. Interpret: weathering and erosion history, transport mechanism/energy, transport direction and cyclicity. Reconstruct: provenance, transport medium and environment of deposition. Common at the break in slope between upland and low-land areas. Gravity and water movement typically result in very high energy systems that lose energy very rapidly. As rivers meander and migrate they sweep back and forth depositing cyclical packages of coarse and fine sediments. Air"s low viscosity limits grain size and increases impact energy. Mix of mineral grains and shelly fossils. Mostly quartz with caco3 cements and shells. Alternating marine and terrestrial structures ripples and laminations. Dominant mineral grain with some shelly material.
