Sedimentology, Stratigraphy and Paleontology Flashcards
What is the law of superposition?
Older layers of rock and sediment always lie beneath younger layers.
What is the law of initial horizontality?
Geologic layers were originally deposited in horizontal layers.
What about faunal and floral succession is used to determine relative rock ages?
Fossil assemblages indicate relative, and sometimes absolute ages for rocks or stratum.
Give 2 examples of mechanical weathering.
- Thermal Stress (temperature differentials causing expansion or contraction)
- Freeze-thaw (water in pre-existing fractures freezes into ice and expands causing the rock to fracture further)
Give 3 examples of chemical weathering.
- Dissolution (CaCO3 + water = dissolved)
- Hydrolysis (mineral + acid = clay mineral)
- Oxidation (rusting)
What type of sediment deposits do you expect to see in a “glacial ice” environment (i.e. clast size, roundness, clast/matrix supported?)
Deposited by a glacier melting in place: boulder - pebble sized, angular matrix supported (till) sediments.
What type of sediment deposits do you expect to see in a “glacial - fluvial” environment (i.e. clast size, roundness, clast/matrix supported?)
Deposited by glacial melt water running down a slope: cobble - sand sized, subrounded, clast supported sediments.
What type of sediment deposits do you expect to see in a “glacial- lacustrine” environment (i.e. clast size, roundness, clast/matrix supported?)
Lake deposits: sand - silt sized, well sorted and well-rounded sediments.
From top to bottom describe glacial stratigraphy.
TOP
Till (Matrix supported, angular, poor sorted)
Outwash (Clast supported, subrounded, bigger clasts near top)
Lacustrine (Lamination, well sorted, fine grained)
BOTTOM
From top to bottom describe meandering river stratigraphy.
TOP
Proximal floodplain: (interbedded sad and mud)
Single Channel (sand - ripples @ top, cross bedding)
Distal floodplain (mud)
BOTTOM
From top to bottom describe gravel braided river stratigraphy.
TOP
Conglomerate Channels (interbedded or lensed sand and gravels)
Proximal Floodplain (interbedded sand and silt)
Single Channel (sand - ripples @ top, cross bedding)
BOTTOM
From top to bottom describe sandy braided river stratigraphy.
Repeated Multistory Channels
TOP
- ripples
- cross bedding
- conglomerates
(erosional surface) - ripples
- cross bedding
- conglomerates
(erosional surface)
BOTTOM
From top to bottom describe delta top, river dominated stratigraphy.
TOP
Flood basin (coal bed, plant fossils)
Distal Crevasse-Splay (cross lamination, coarsening upwards, coal seams)
Channel (coarse sandstone, trough cross bedding, offset)
BOTTOM
From top to bottom describe Delta top to upper shoreface, tide dominated stratigraphy.
TOP
Salt marsh (rooted muds)
mud flats (lumpy ripples, lenticular bedding)
mixed flats (wavy bedding, more defined ripples)
sand flats (flaser bedding, well defined ripples)
subtidal (lots of sand, cross bedding)
BOTTOM
From top to bottom describe foreshore to upper shoreface stratigraphy.
TOP
beach sand (sand)
swash (sand low angle cross bedding)
offshore bar (sand cross bedding)
wave ripples (sand ripples)
