o Detrital grains/detritus -particles of various sizes
o rocks composed of silicate fragments
o rocks formed by biologic processes. (Calcite, araganite)
o compressed organics. (coal, oil shale)
Turbidity formed by?
earthquake, slumping, storms, rivers, glacial meltwater, volcanic ash fall.; subduction
zones; usually submarine fan or abyssal plain deposits
Turbidity current deposition sequence
similar to delta; proximal=gravels and coarse sand, t
chemical most important, biological 2nd, lastly physical
rate of chemical weathering affected by?
temp and precip
CHEMICAL. The break up of rock caused by moving water dissolving the rock. (caves.)
ex) halite or calcite
Sand in dunes?
water/wind carries sed but when current slows sand is deposited (so same spot)
pits, scratches, conchoidal fractures; frosted=dunes or polished=desert dunes; changed
more rapidly than sphericity or roundness; maybe remnant f
velocity and water depth/grain size
straight, sinuous, catenary, linguoid, and lunate; more complex forms=shallower water
and higher velocities
maximum depth which waves can disturb & erode the sea floor
wave energy ceas
standard length pole to measure dipping or horizontal beds; inexpensive w/ protractor
and rotating plate on top; expensive clinometer, sighting bar and brunton transit; only 1
person needed to work
measure of asymmetry of curve,
What is biostratigraphy?
correlation of strata and determination of relative ages based on index fossils
William "Strata" Smith
Invented biostratigraphy. Job = make a map of geology of England.
Noticed that same fossils in same order. Specie A always in r
affects porosity (% void space) and permeability (ease of transport of fluids);
porosity and permeability vs sorting
better sorted = better p&p; coarser grained= permeability better (small grains have thin
descriptive statistics from random samples are valid approximations of the population's
Types of graphs
Historgrams, Frequency Curve, Cumulative Curve (arthimetic and probability)
bar graph with grain size versus wt
Prob w/ 'fingerprinting' dep envirns
size distribution is due to processes and the same processes occur in diff environs; also
single environ contains many processes
moving along bottom
skipping-random contact with bottom
fossil has highest abundance
probs: not used for time-strat correlations
used for Correlation by biogeographical acme zones (fossils have specific geological
Worldwide biostratigraphic correlation difficult
most species not world wide
Once grain entrained moves as
Bed load-coarse on bottom;
Traction-boulders, cobbles, gravel, some sand;
Suspended-silt and clay
Dissolved load- solubles
predicts settling velocity of sediment; V= (ps-pf)*gd2)/18 ; V=settling ve
o wave produced, rounded or sloping cross-stratification (mounds) convex shape.
o found in mud deprived environment. lenses of mud that have accumulated in the
troughs of ripples. very thin layers.
o found in sa
o water particles moving parallel to each other.
o water particles moving in eddies. three zones on turbulent flow. laminar sublayer,
turbulent boundary layer, external zone.
o used to define a boundary between
Whats meant by rule of priority?
o When is it okay to not follow this rule?
Means to not use a name which has
already been used and established/accepted. Can be disregarded if a low priority
name is well established or if a high priority name is inadequa
o grains are interlocked; results from precipitation of mineral crystals; most igneous
rocks exhibit this texture
sorting and roundness
o variation in grain size; well sorted = little variation; sharpness or smoothness of
o underwater gravity flows in which sediment is supported by turbulence of the
fluid; when shock stirs up a suspended mass, it is more dense and moves
phi scale (Udden-Wentworth)
o specifies grain diameters in mm, fixed ratio
Whats the difference between a pinch out and a simple facies change?
o A facies change occurs when the type of rock changes due to depositional
changes. A pinch out occurs when a rapid transgression/regression occurs.
Why are fining-upward sequences of m
How could you recognize a paleosol and hence a surface of weathering within a sediment
o Best recognized by layers rich in organic matter and layers rich in reddish clays.
Disruption of original bedding due to organic activity is also an indica
o soil horizon consisting of humus and mineral matter (sediment)
o where the zone of accumulation begins, ions and clays that have leached from
above precipitate; red color
o partially altered parent material due to chemical
What causes pinch outs?
o A lateral decrease in the supply of a given type of sediment
facies (according to EOD)
o lithology characteristic of a give EOD
o when sediment is overwhelmed by a relative rise in sea level, causing the
Rocks formed from crystals that precipitate during evaporation of water
example - halite, anhydrite
gypsum at depth
become anhydrite b/c to much pressure
3 types of gypsum/anhydrite
nodular, laminated, massive