Week 1 Flashcards
Sedimentology =
Study of processes that create sediments and dynamic environments where they accumulate
~75% rocks are sedimentary
Uniformitarianism =
Present is the key to the past
but e.g. climate = changed?!
Used in palaeoclimatography, palaeogeography, transgression, regression, fossils
Rock cycle
Weathering
Transportationg
Deposition
Burial
Metamorphism/Magma
Uplift
Stratigraphy =
Layers of rock
Transgression =
Rising SL
Regression =
Falling sea level
The 5 basin settings
- Rift
- Intracratonic
- Passive margin
- Foreland
- Strike-slip
Rift basin
Crust thinned as stretched
Rift grows = crust blocks on fault border slip
–> low areas and narrow mountain ridges
Continental/marine
e.g. E African rift
Intracratonic basin
Interiors of continents (circular/oval)
Slow subsidence due to thermal sag over previous rifting areas
Continental BUT flooding from adjacent oceans = epicontinental seas
Passive margin basin
Along continent margins (NOT tectonic)
Underlain by former oceanic crust rift
Thermal relaxation/subsidence
Carbonate and clastic (10-20km thick)
e.g. Gulf of Mexico along Southern US
Foreland basin
Adjacent and // to mountain belts
Compressional tectonics = downward flexing of lithosphere due to weight of adjacent mountain belt
Deep marine –> continental (erosion of mountains) - thickness >10km
e.g. Persian Gulf due to Zagros Mountains of Iran
Strike-slip basin
“Pull apart” basin
Continental/marine
e.g. San Andreas, California
North Anatolian Fault, Turkey
Tabernas Basin, SE Spain
Uses for sedimentology
Hydrocarbons
Placer diamonds
(eroded/transported by sedimentary processes)
Groundwater
BIFs; iron ore
Limestone mining
“Liberation of sediment flux”
- WEATHERING AND EROSION
- chemical/physical
- uplift
- climate
- lithology
- vegetation - SEDIMENT YIELDS
= total amount of sediment exported from drainage basin in given period of t (/km2/a)
Denudation =
High/low???
Erosion
High levels due to orogenic belts/rivers
e.g. Brahmaputra
Also due glaciers; transport sediment (powerful) + no vegetation to stabilise
Low due to old cratons/low lying areas e.g. Africa
Sediment routing system =
Source –> sink pathway along different trajectories
e.g.
RIVER BED; short transit times, brief sediment storage
BARS/FLOOD PLAIN: long transit time, long sediment storage
Storage represents buffering of incoming sediment flux
Why are mass flows important?
Transport significant amounts of material
Types of mass flow from slow to fast
Creep
Slump
Mud flow
Rock/debris slide
Rock/snow avalanche
Rock/debris fall
Angle of repose =
35’
Past this = landslide
What causes thermohaline circulation?
Density - due to salinity/T
Contourite sediments =
Reworked turbidite sediments due to thermohaline circulation
N.B. No record during upper cretaceous b/c no bottom water circulation
What happens after sediment deposition?
Burial, lithification, compaction
N.B. Mudrocks 80% water!!!
Types of sediment
BIOGENIC
CLASTIC
CHEMOGENIC
VOLCANICLASTIC
ORGANIC
Biogenic sediment
Skeletal fragments of calcite/aragonite (and direct option)
Limestone/dolomite
