stratigraphy Flashcards
father of stratigraphy
nicolas steno
breaks due to variations in the normal processes in the environment
diastem
weathering and colonization of palnts
non-depositional diastem
migration of river channels
erosional diastem
changes in the base level of erosion or aggradation
non-depositional and erosional diastem
possesses charac that distinguish it from other parts of the formation
member
basic unit of stratigraphy
formation
basic unit of stratigraphy
formation
defined body of predominantly intrusive highly deformed and highly metarmophed rocks has boundaries placed at positions of lithic change
lithodemic
fundamental unit in lithodemic classification should posses distinctive lithic features and some degree of internal homegeneity
lilthodeme
two or more associated lithodemes of the same class
suite
it is a type of contact wherein it forms unbroken depostional sequences with layers deposited by uninterrupted deposition
conformable
refers to aspect, nature or manifestation of character or rock strata or specific constituents of rock strata
facies
facies adjacent to one another in a continuous vertical sequence also accumulated adjacent to one another laterally. 2 diff facies found superimposed on one another and not separated by unconformity must have deposited adjacent to each other at a given point in time
walther’s law
facies based on petrological characters such grain size and mineralogy
lithofacies
commonly preserved as buolbous or mamillia natural casts on the bottoms of sandstone beds
flute marks/flute casts
preserved on lower surfaces of sandstone beds as thin ridges
tool marks
sharply defined upper and lower surfaces enclosing or bounding beds
bedding plane
indicator of the depositional conditions under which the bed formed
bed shape
stratification thinner than 1cm produced by changes in the pattern of sedimentation
lamination
finely interbedded grain sizes such as sand and mud and can occur at a variety of scales
heterolithic bedding
0.5 to 3.0 cm in height with wavelengths 5 to 40 cm
less tahn 0.7 mm in diameter
ripples
typically have long straight parallel crests with bifurcations ripple index is high and rarely preserved
wind ripples
internal sedimentary structure of many sand grade and coarser sed rocks with a height of >6cm and thickness of 1cm or more
cross bedding
internal sedimentary structure of many sand grade and coarser sed rocks with a height of <6cm and thickness of only a few mm
cross lamination
cross stratification where the inter set boundaries are generally planar
tabular cross bedding
cross stratification where the inter set boundaries are scoop shaped from a curve crested bedforms
trough cross bedding
distinguished from current ripple by irregular and undulating lower set boundaries and drapping foreset laminae
wave formed cross lamination
cross beds dips of adjacent sets oriented in opposite directions produced by reversals of currents
herringbone cross bedding
cross laminated and contains mud streaks usually ripple troughs
flaser bedding
mud dominates and the cross laminated sand occurs in lenses
lenticular bedding
cross stratification where thin ripple cross laminated sandstones alternate with mudrock
wavy bedding
gently undulating low angle 1-5 degrees cross lamination with the convex upward part of the hummock and concave downward part of the swale
hummocky cross stratification
cross stratification where hummocks are rare and the bedding mostly consists of broad concave up laminae
swaley cross stratification
produced by wind action and generally forms sets which are much thicker and the cross beds themselves dip at higher angles >30degrees and reach up to 30m high
aeolian cross bedding
larger scale low angle bedding oriented normal to medium/smaller scale cross stratification formed through lateral accretion of point bars 1m or more in height and continue laterally for several meters to more than 10m
epsilon cross bedding
meandering river channel sandstones but can occur in delta distributary and tidal channel deposits
lateral accretion
deltas build into lakes or lagoons often referred as Gilbert type deltas occur aas wedge or fan in marginal lacustrine or marginal marine
small delta cross bedding
contains epilimnion, hypolimnion, and thermocline
stratified lake
have seasonal overturn and mixing and limit preservation of organic material
unstratified lake
a downstream spiraling effect resulting from 3d velocity component
helical flow
genetically related barcomplex and channel complex
storey
basal deposit that is often a relatively thin layer of pebbles and cobbles that are too coarse for the river to transport
lag deposit
occupied by the meander loops and consists of channel bar fill deposits
channel belt
sandy deposits that develop where overbank flooding causes a break in a channel levee
crevasse splay
channel belts shift location rapidly
avulsion
warm layer of the lake’s therman stratification that is usually oxic
epillimnion
oxygenated lake facies that display evidence of wave process and occassionally contains pervasive bioturbation on and plant fossils
epilimnic facies
cold layer of lake that is anoxic
hypolimnion
non oxygenated lake facies that have fine laminated terrigenous, biogenic and authigenic minerals and turbidite sands
hypolimnic facies
also called metalimnion and the boundary of epilimnion and hypolimnion
thermocline
waters with salinity with 5g/1L of solutes
brackish water
blowing out and scattering of rock particles by wind
deflation
mechanical scraping of rock surface by friction between rocks and moving particles
abrasion
consists of gravel sized particles that are too large to be transported and forms a deflation pavement
lag deposits
layer of lag deposits left by deflation processes
desert pavement
dark surface of iron and manganese oxides resulting from long exposure of a rock surface in the oxidizing conditions of a desert
desert varnish
undulation in a scale of hundreds of meters to kilometers in wavelength and tens to hundreds of meters in amplitude
draas
single wind blown faced ventifact
einkanter
2 wind blown faced ventifact
zweikanter
3 wind blown faced ventifact
dreikanter
biogenic laminated structures which have a great variety of growth forms developed through trapping and binding of carbonate particles by surficial microbial mat and biochemical precipitation of carbonate
stromatolites
used for deposits of large blocks result of fault activity during deposition and erosion of fault scarps or collapse of carbonate platform
megabreccia
consists of concave up laminae and separated by structureless zones
dish and pillar structures
soles of sandstone bed overlying mudrock occurring as bulbous rounded structures no orientation
load casts
result of loading bed or sand can sink into underlying mud and break up into discrete masses
ball and pillow structure
local patches of cementation that form sediments after deposition
nodules/concretions
develop within the soul of semi arid environments where evaporation exceeds precipitation found in red bed successions in floodplain mudrocks or marine clastic sediments
calcrete
sutured type bedding parallel high angles. ocur as single sutured planes or as zones or swarms
stylotites
type of trace fossil that is more complicated surface trails found in symmetrical or ordered pattern eithr coiled radila meandering and mostly drtritus feeders
grazing tralls
ratio of flow inertia versus viscosity
reynold’s number
ratio of flow inertia and gravity forces
froude number
gradual transition from lower to upper flow regime as froude number increases but a change from upper to lower flow regime is accompanied by an instantaneous decrease in velocity and increase in water depth
hydraulic jump
function of grain size and shape wehre generally large spherical grains settle faster than small irregulary shaped grains
drag
formed when an existing rock is eroded or broken down into pieces by water, wind, or ice
Detrital sedimentary rocks
region of the shelf between the low tide mark and the depth to which waves normally affect the seat bottom
shoreface
depth at which waves normally affect the sea bottom
fair weather wave base
depth at which higher energy waves generated by storms that affect the sea bed
storm wave base
tidal cycle that occurs due to the elliptical nature of the Earth’s orbit
annual tidal cycles
cause tides due to earth being on its closest proximity to the sun, where the gravitational effect is strongest
spring and autumn equinoxes
flows in the opposite direction as the water returns to low tide
ebb tide current
wind driven curretns related to global wind systems that have differences in air mass temperature and coriolis force
geostrophic currents
produce a coarsening upward
deltas
ground hugging flow of suspended sediment in river water
hyperpycnal flow
water surface hugging flow of sediments
hypopycnal flow
processes w/o any external control
autocyclic process
causes lobe switching
delta distributary channels
formed due to settling of sand suspended during flood events
graded rhytmites
floor of the receiving basin immediately seaward of the base of the delta front slope
prodelta
large volume of sediment and tends to lobate there is moderate sediment supply and elongate when the sediment supply is large
fluvial dominated delta
a fluvial dominated delta that has created when very large amounts of sediment were carried into quiet water
mississippi delta
dominance of stream sedimentation that forms the finger like distributaries
bird foot
long linear sand bodies deposited as mouth bars shift seaward as a distributary system advances
bar finger sands
forms as mouth bars are reworked more heavily by the waves
barrier bars
converted abandoned distributaries due to ongoing subsidence
interdistributary bays
wave action is limited and tidal ranges excess 4m lobes are no longer recognizable seaward extension of a microtidal estuary with tidal influence increasing further and delta becoming tide dominated elongate perpendicular to the shoreline
tide dominated delta
wave action reworking the sediments and make such deltas much sandier than other type of deltas and occurs where wave energy is high and outflowing freshwater behaving as countercurrent
wave dominated delta
coarser sediments that may enter hen storms was sediments over the barrier
washover deposits
zone where the fluvial processes are dominant
bay head delta
lowest energy part of the estuarine system where the river flow rapdilty decreases and wave energy is concentrated at the barrier ba aregion of fine grained depostion often rich inorganic
central lagoon
central lagoon that becomes filled with sediment crossed by channels where wave ripples form and draped with mud
salt water marsh
formed in the outer zone of the estuary where the wave action reworks marine sediments
barrier
forms funnel shaped estuary tends to increase flood tidal current strength
tidal dominated estuary
platforms with gentle slopes <1 degrees down the deep water w/o any break in slope
carbonate ramp
flat topped with a sharp change in slope at the edge forming a steep margin, with a higher carbonate platform at the edge
rimmed shelf
rimmed shelf but lacks the higher carbonate platform at the edge
non rimmed shelf
it is an anthozoans and the largest class within the phylum cnidaria
corals
at what depth does calcite starts to dissolve and what do you call this?
3.5-5.5km below sea level
calcite compensation depth
at what depth does aragonite starts to dissolve and what do you call this?
1.8-2.2km
aragonite compensation depth
at what depth does opal starts to dissolve and what do you call this?
6km below sea level
opal compensation depth
depth at which the organisms lie is essential for photosynthetic marine organisms
bathymetry
mound like dome like mass of rock built up by sedimentary organisms composed of their calcareous remains and enclosed or surrounded by rock of different lithology organic reef or a non reef limestone mound
bioherm
non reef building
ahermatypic
reef building
hermatypic
contains zooxanthellae and symbiotic algae
zooxanthellate
distinctly bedded and widely extensive or broadly lenticular blanket like mass of rock built by and composed mainly of the remains of sedentary organisms and not swelling into a mound like or lens like form
biostrome
low energy areas shelf ward of the reef flat zone where fine sediments winnowed from the reef settle out with a prolific growth of a diverse bottom biota where colonial organisms are typically delicate stubby dendroid to bushy knobby and globular and can construct patch reefs and have water depths that are normally less than 10m but can be in excess of 70m from the reef settle out
back reef zone (lagoonal)
very shallow water surface immediately shelf ward of the reef crest composed of cemeted coarse skeletal debris derived from reef and locally the loose material may be swept into small islands which further protect their areas through meteoric diagenesis
reef flat zone (sandflat)
highest part of modern reefs that shows the most wave resistant organisms typically encrusting sheet like forms but may include massive or heavy branched forms in lower energy environments
reef crest (buttress)
extends from the surf zone into deeper water <100 where domination by growth of massive corals grades
reef front zone (lit zone)
light penetration diminishes with increasing water depth >30 and with decreasing wave intensity
lower reef front
slope developed at the base of the reef front in deep water with little or no light penetration no in place growth of colonial organisms
fore-reef zone (dark slope)
province of reefs found in australia with individual buildups in varying states of infill with respect to sea level
great barrier reef
deposited through sand transported down steep slopes near the angle of repose by dispersive pressure
grain flow deposits
poorly sorted clast rich muddy deposits where the clasts are transported down slope by buoyancy pressure
debris flow deposit
also known as zone of eluviation and leaching contains a little organic material
E Horizon
washing out of the fine soil components
eluviation
depletion of soluble materials from the upper soil
leaching
known as subsoil the zone of accumulation
b soil
true soil OAEB
solum
form under boreal forests or broadleaf deciduous forests rich in iron and aluminum. fertile productive soils because they are neither too wet or too dry
alfisols (high nutrient)
parent material is volcanic ash and cinders deposited by recent volcanic acitivity
andisols volcanic soils
develop in dry places insuffiecient water to remove soluble minerals may have accumulation of calcium carbonate gypsum or salt in subsoil low organic content
aridisols desert soils
limited development and exhibiting properties of the parent material.
entisols new soils
little profile development that occur in regions with permafrost. low temperatures and frozen conditions for much of the year slow soil forming processes.
gelisols permafrost soils
little or no climatic implications. dark partially decomposed organic material; referred to as peat
histosols organic soil
weakly developed young soils in which the beginning of profile development is evident common in humid climates exist in arctic to the tropics native vegetation is often forest
inceptisols young soils
dark soft soils that have developed under grass vegetation found in prairie areas
humus rich surface horizon that is rich in calcium and magnesium found in hardwood forests with significant earthworm activity climatic range is boreal or alpine to tropical
molisols prairie soils
occur on land surfaces unless parent materials were strongly weathered before they were deposited found in the tropics and subtropical regions rich in iron and aluminum oxides heavily leached poor soils for agricultural
oxisols tropical forest soils
found only in humid regions on sandy material common in northern coniferous forests and cool humid forests light colored horizon leached material
spodosols conifer forest soil
represent the products of long periods of weathering poor soil quality
ultisols low nutrient soils
large amounts of clay found in subhumid to arid climates adequate supplies of water are available to saturate the soil after periods of drought soil expansion and contraction exert stresses on human structures
vertisols swelling clay soils
still later shallow diagenesis that occurs as sed rocks approach the surface due to erosion
telodiagenesis
later deeper diagenesis
mesodiagenesis
early shallow diagenesis that occurs shortly after burial
eodiagenesis
what is the form silica cement
syntaxial quartz overgrowth
grain size increases upwards
reverse or inverse grading
low amplitude bedforms sand grade which migrate upstream throughout deposition of sediment on the upstream facing slope of the bedroom
antidune cross bedding
referred to at least 50m thick commonly developed at carbonate platform margins and adjacent to reefs where the dipping beds will be made of shallow water material, reef fragments angle of dip varies from few degrees to 30 degrees
very large scale cross strata and clinoforms
where the coarser particle at the base give way t finer particles higher up
normal grading
having no apparent internal structure during deposition or was destroyed by bioturbation recrystallization dolomitization formed through sedimentation or dumping
massive beds
when strong current flows, elongate and discoidal pebbles can become oriented with in upstream dip
imbrications
incomplete polygonal patterns that form through dewatering from salinity changes or osmotic effects and occur in shallow sublittoral lacustrine deposits
synresis cracks
develop in carbonate sediments through early cementation and expansion of the surface crust
polygon cracks
cavities filled with internal sediment and spray calcite cement
geopetal structure
continuous cavities either parallel or cutting the bedding very considerably in size and formed by cracking of the lithified or lithified sediments and opening up the cavities or through penacontemporaneous tectonic movements early compaction and settling or lsight lateral movement
sheet cracks/ neptunian dykes
through subaerial exposure and meteoric dissolution of a limestone surface under humid conditions have irregular topography with potholes or cracks
paleokaratic surfaces
present in limestone where there has been synsedimentary cementation so that sediment was partly or wholly lithified on the seafloor
hardgrounds
when cemented surface layer can expand and crack into polygonal pattern as a result of sedimentary cementation of carbonate sediments and can develop in shallow subtidal sediments but commonly tidal flat carbonates
topaz structures
collection of multiple genetically related facies formed within a single depositional system
facies association
progressive change in certain facies properties in a specific direction vertically, laterally
facies successions
sea level rise producing a vertical sequence of facies with a landward movement of shoreline representing progressive deeper water environments
transgression
transgressive sequence that has finer grained facies overlying coarser grained facies
onlap sequence
landward building of strata
retrogradation
decrease in sea level producing a sequence of facies with a seaward movement of shoreline representing progressively shallower water environments
regression
regressive sequence that has coarser grained facies overlying finer grained facies
offlap sequence
seaward building of strata
progradation
body of rock defined exclusively of bounding uncomformable surfaces
allostratigraphic unit
using fossil assemblage contained within the rock strata
biostratigraphy
determining that two or more rock bodies we deposited at the same time
temporal correlation
study of mineralized microfossils of microscopic size
micropaleontology
study of nanometer sized calcareous microfossils
nanopaleontology
study of nanometer sized organic walled fossils
palynology
observation of one or more definable unique features in two separate rock sections
stratigraphic correlation
observation of one or more definable paleontological features in two separate rock sections with the basic assumption that identical fossils found in the areas are probably the same age
biostratigraphic correlation
fundamental biostratigraphic unit
biozone
divides earth history into recognizable intervals and includes both material and non material units
time stratigraphy
at the same time or over the same period of time
synchronous
time transgressive
diachronous
photosynthesizer
phytoplankton
non photosynthesizer
zooplankton
juvenile plankton
merplankton
rafters
pseudoplankton
attached to bottom
sessile benthos
crawl along bottom
vagrant benthos
fine grained material derived from the platform and resedimented by suspension into the slope and basinal environment, with rock types include finely laminated to bioturbated mudstone and wackestone with deep water fauna or transported shallow water fauna
hemipelagic carbonate
sediment deposited by slow suspension of material biochemically produced in surface waters
pelagic carbonate
freshwater surface plumes carrying sediment across the shelf before mixing and flocculation cause clay particles to settle
sediment plumes
turbid body of suspended sediment that is denser than the surrounding water but not dense enough to sink rapidly
nepheloid flow
owing to density stratification of ocean water bottom currents adjacent to continental margins tend to flow parallel depths contours or isobaths
contour currents
calcareous and siliceous shelled planktonic to depth organisms settle through the water column to the seafloor upon death
pelagic rain
mixtures of terrigeneous mud and biogenic remains deposited from nepheloid plumes by suspension settling and pelagic rain out
hemipelagic mud
2/3 siliclastic clay deposited by suspension settling and authigenic formation of clay minerals
pelagic clay
shallow water carbonates emplaced by storms or sediment gravity flows
allochtonous deep sea carbonates
products of debris flows where individual clasts are not in contact with each other and there is no grain fabric
matrix supported conglomerate
the basal unit being the coarsest layer has an erosional base often with sole marks and is structureless but normally graded
Ta
layer above the Ta layer which is made up of parallel laminated sand
Tb
overlying layer above the Tb layer which is comprised of rippled and convulated sand
Tc
parallel laminated silt and mud layer above the Tc layer
Td
the topmost layer in the bouma sequence made up of mud partly from the turbidity current and partly from hemipelagic deposition
Te
form form the deposits of successive flows of turbidity currents
submarine fans
channels that are depositing sediment that have much different morphology than those that are erosional which also vary considerably with the grain size of the sediment load
submarine fan channels
part of submarine fan that has the channel and leevee system and is largerly a sediment by pass area except for overbank and leevee deposits and sands deposited in the channel by small flows
inner fan
