Srp Exam 3

Front 1

transgression

Back 1

landward shift in a shoreline

Front 2

regression

Back 2

basinward shift in a shoreline

Front 3

lithofacies

Back 3

dominant characteristic = lithology

Front 4

biofacies

Back 4

dominant characteristic = fossils

Front 5

ichnofacies

Back 5

dominant characteristic = trace fossils

Front 6

logfacies

Back 6

dominant characteristic = wireline log profile [often related to texture profile]

Front 7

seismofacies

Back 7

dominant characteristic = acoustic response

Front 8

What are the 2 most important factors behind transgression and regression shifts?

Back 8

1. sea level change
2. subsidence

both involve shifts in the relative balance of the rate of sediment accumulation (ΔS) and the rate of accomodation space (ΔA)

Front 9

rate of accomodation space (ΔA)

Back 9

space made available for POTENTIAL sediment accumulation

Front 10

if ΔS < ΔA, then ______ results == rock record is _______

Back 10

transgression == retrogradation

Front 11

if ΔS > ΔA, then _______ results == rock record is ________

Back 11

regression == progradation

Front 12

if ΔS = ΔA, then ______ results == rock record is ______

Back 12

stasis == aggradation

Front 13

Walther's Law works only for a ________________

Back 13

conformable succession

Front 14

Principle of Uniformitarianism

Back 14

natural laws have acted consistently throughout time; "present is the key to the past"

Front 15

Principle of Actualism

Back 15

natural laws acted consistently throughout time but the magnitude of the processes may vary

Front 16

Walther's Law

Back 16

"Only those facies and facies areas can be superimposed, primarily, which can be observed beside each other at the present"

In other words, those sedimentary environments found today next to each other will be found vertically arranged in the same order with transgression or regression.

Front 17

What are 3 reasons Walther's Law is important?

Back 17

1. tool for correlation (connecting rock volumes and surfaces that are equivalent)

2. tool for prediction (making assumptions into unknown regions for example, from a single well or outcrop location to areas away from the way or outcrop)

3. fundamental for making facies models (vertical successions of genetically related rock units)

Front 18

facies model

Back 18

a conceptual generalization of the common rock characteristics of a particular depositional system

typically represented as either a vertical succession of sedimentary facies or a block diagram (3D representation) or as a combination of the two

Front 19

In what kinds of settings do alluvial fans develop?

Back 19

Alluvial fans develop in distinctive settings characterized by an abrupt change in stream gradients from steep (mountain canyons) to less steep, and by flow conditions that are confined (mountain canyons) changing to unconfined.

- steep mountain fronts
- block faulted moutain fronts (normal fault footwall = mountain, and hangingwall = basin)

Front 20

Alluvial fan radii vary considerably but in general they do not extend more than about ____ from the mountain front.

Back 20

5 km

Front 21

What 3 factors influence alluvial fan radii?

Back 21

1. size of drainage basin (bigger drainage basin --> larger fan)

2. erotion potential of the bedrock (more readily eroded --> larger fan)

3. discharge (greater discharge --> larger fan)

Front 22

What characterizes the upper fan portion of an alluvial fan?

Back 22

-concave upward profile
-slope 10-15 degrees
-few deep, narrow channels leading up to a feeder canyon

Front 23

What characterizes the middle fan portion of an alluvial fan?

Back 23

-intersection point marks the profile transition
-convex upward profile
-slope 5-10 degrees
-numerous shallow, wide channels and lobes

Front 24

What characterizes the lower fan portion of an alluvial fan?

Back 24

-convex upward profile
- slope 2-5 degrees
- numerous lobes and few narrow channels that head with in fan

Front 25

What is the climatic setting of alluvial fans?

Back 25

most commonly seen in arid to semiarid climates, but also occur in humid climate settings associated with large tectonically active mountain ranges (e.g. the Himalayas)

Front 26

Sedimentation on alluvial fans?

Back 26

Sedimentary processes on alluvial fans are highly variable, particularly in arid to semi-arid climates. Sedimentation takes place in short-lived, dramatic events followed by very long episodes of little activity.

Front 27

Alluvial fans have a ______ competence, ______ capacity ________.

_______ processes dominate sedimentation on alluvial fans.

______ is both confined _________ and unconfined on the ______ and _____ fan surfaces.

Back 27

high competence, low capacity traction current

sediment gravity flow processes dominate sedimentation

fluid flow is both confined within channels and unconfined on the middle and lower fan surfaces

Front 28

Sedimentation on the upper fan sediments:

Back 28

- channel erosion and filling dominant (poorly stratified, poorly sorted gravel)
- debris flow deposition as flow plugs and levees (very poorly to poorly sorted, matrix-supported boulder gravel)
- gravel traction deposits (moderately sorted gravel - may have coarse sand secondary mode)
- no clearly developed stratification or texture organization

Front 29

Sedimentation on the middle fan sediments:

Back 29

- debris flow lobe deposition (poorly sorted, matrix- to clast-supported boulder gravel; stratification thickens upwards; texture coarsens upward) This is due to lobe building after tectonic activity.
- sheetflood deposition across surface (unconfined (rapidly decelerating) tractions currents; fine upwards; moderately sorted cobble gravel up to moderately sorted pebbly coarse sand)
-physical structures include lower & upper plane bed and trough cross stratification
-sheet geomotry == width == 100's x thickness

Front 30

Sedimentation on the lower fan sediments:

Back 30

- mudflow and finer gravel debris flow deposits
- coarse sand sheetflood deposits (can be mica rich)
- narrow channel-fill deposits; fine upward

Front 31

During tectonically active episodes, vertical stratification and texture trends in the middle and lower fan are:

Back 31

thin and fining upwards trends;
coarse sediment trapped close to fault

Front 32

During tectonically inactive episodes, vertical stratification and texture trends in the middle and lower fan are:

Back 32

thicken and coarsening upward trends;
coarse sediment delivered farther down slope

Front 33

Eolian and subaqueous processes are similar in what ways? In what ways are they dissimilar?

Back 33

similar:
-same 3 modes of transport
-bedforms develop under appropriate velocity conditions

dissimilar:
- density of air is a few orders of magnitude less than water (so higher settling velocity of particles in air and higher entrainment velocity in air)
- lubricating effect of water not in air (so friction forces between particles are stronger in the air [higher angle of repose] & the cushioning effect is less in air & momentum is more transferrable in air than in water via particle collision)

Front 34

Where do we find eolian deposits accumulating today? (3 general characteristics)

Back 34

1. strong persistent winds and divergent winds (vertically or horizontally)

2. dry climate (microcliate; but can be intermittently wet)

3. large supply of dry sand

Front 35

What places fit the criteria for eolian deposit accumulation?

Back 35

-inland of beaches (generally parallel the shoreline)
-desert regions (can accumulate over vast regions called ergs = eolian sand seas)

Front 36

What are 3 generalizations about eolian processes and deposits?

Back 36

1. because abrasion is so severe, quartz grains are the dominant framework grain in most eolian deposits

2. because high entrainment velocities and persistent winds are required, eolian deposits are predominantly well sorted, very fine to fine sand

3. physical processes dominate

Front 37

What are the three types of eolian stratification types?

Back 37

1. wind ripple strata
2. avalanche strata (when angle of repose is exceeded, dry grainflow occurs)
3. grainfall strata (in lee of a dune or other obstruction, suspension sedimentation occurs)

Front 38

Eolian and subaqueous processes are similar in what ways? In what ways are they dissimilar?

Back 38

similar:
-same 3 modes of transport
-bedforms develop under appropriate velocity conditions

dissimilar:
- density of air is a few orders of magnitude less than water (so higher settling velocity of particles in air and higher entrainment velocity in air)
- lubricating effect of water not in air (so friction forces between particles are stronger in the air [higher angle of repose] & the cushioning effect is less in air & momentum is more transferrable in air than in water via particle collision

Front 39

Where do we find eolian deposits accumulating today? (3 general characteristics)

Back 39

1. strong persistent winds and divergent winds (vertically or horizontally)

2. dry climate (microclimate; but can be intermittently wet)

3. large supply of dry sand

Front 40

What places fit the criteria for eolian deposit accumulation?

Back 40

-inland of eaches (generally parallel the shoreline)
-desert regions (can accumulate over vast regions called ergs = eolian sand seas)

Front 41

What are 3 generalizations about eolian processes and deposits?

Back 41

1. because abrasion is so severe, quartz grains are the dominant framework grain in most eolian deposits

2. because high entrainment velocities and persistent winds are required, eolian deposits are predominantly well sorted, very fine to fine sand

3. physical processes dominate

Front 42

What are the three types of eolian stratification types?

Back 42

1. wind ripple strata
2. avalanche strata
3. grainfall strata

Front 43

Wind Ripple Strata are characterized by:

Back 43

-wind ripples are low amplitude (H), long wavelength (L) bedforms
-cross lamination rarely seen
-as wind ripples migrate and aggrade with time, they produce regular spaced 1-5 mm inversely graded lamination called "pinstripe lamination"
-sand is very tightly packed

Front 44

wind ripples have L/H = ____ versus subaqueous ripples which have L/H = _____

Back 44

wind ripples L/H = 10-70
subaqueous ripples L/H = 5-10

Front 45

Avalanche Strata are characterized by:

Back 45

-produces lenticular, 1-10 cm inversely graded cross strata
-sand is loosely packed

Front 46

Grainfall strata are characterized by:

Back 46

-sheets, 1-10's cm structureless strata, may also include diffuse, discontinuous 1 mm laminations
-sand is loosely packed

Front 47

Although uncommon, what types of records of biological and chemical processes are found in eolian strata?

Back 47

-terrestrial vertebrate tracks
-insect and amphibian burrows
-in arid settings, evaporite precipitation

Front 48

Erg depositional systems are composed of what 3 facies?

Back 48

1. Dune Facies
2. Interdune Facies
3. Sand Sheet Facies

Front 49

Dune Facies

Back 49

-dominate deposits in erg depositional systems
-eolian dune deposits are characterized by dm to 10's m thick cross stratified sets
-cross strata composed of varying combinations of the eolian strata types
-specific types of dune facies are based on the bedforms observed in the modern and style of cross stratification associated with each bedform

Front 50

What are the four main types of eolian dunes?

Back 50

1. Barchan dune
2. Ridge dune (Sinuous and Straight Crested Ridge dune)
3. Star dune
4. Linear (Seif) dune

Front 51

Barchan dune

Back 51

-arcuate crestlines in plan view, convex to the prevailing wind
-steep slip faces (high angle of repose) --> avalanche strata
-occur in isolation or as outriders at the fringe of large ergs
-commonly occur above "deflation surfaces"
-form where sand is in relatively short supply
-isolated sets of trough cross strata

Front 52

Sinuous and straight crested ridge dune

Back 52

-sharp crestlines with sinuous or straight plan trace
-tranverse to wind == steep slip face == avalanche deposits
-oblique to wind == poorly developed slip face == less avalanche, more commonly grainfall and wind ripple strata

Front 53

barchan --> ______ --> _______

Back 53

barchan --> sinuous crested --> straight crested

Front 54

Star dune

Back 54

-consists of series of sinuous ridges extending outward from a central peak
-internally very complex
-occur in areas of complex wind patterns

Front 55

Linear (Seif) dune

Back 55

-long, narrow ridges
-individual ridges are known to be as long as 200 km
-individual dunes are as tall as 100 m
-ridges are spaced about 1-2 km apart
-dunes commonly host dunes of varying types
-formed in very high wind velocities and typical of low sand supply

Front 56

3 types of ridge dunes with different internal structures:

Back 56

1. simple dunes = trough or tabular cross strata
2. compound draas = trough or tabular cross strata cosets
3. complex draas = smaller trough or tabular planar cosets in larger-scale tabular planar or trough cross strata

Front 57

2 proposed origins of linear (seif) dunes:

Back 57

1. helical flow = predict bimodal cross strata dips centered around prevailing wind direction

2. longitudinal to highly oblique flow = predict wind-rippled plinth or supported dune cross strata dips unimodal but nearly parallel to prevailing winds

Front 58

Eolian dune types and their corresponding paleocurrent distributions:

Back 58

barchan --> unimodal, wide variance
transverse --> unimodal, narrow variance
linear --> bimodal
star --> polymodal, wide variance

Front 59

The lithology of the interdune facies is dependant on the conditions in the interdune area:

Back 59

dry interdune = wind ripple strata +/- evaporite nodules

wet interdune = wind ripple strata + subaqueous physical and rare biogenic structures

wet interdune with marine influence = wind ripple strata + subaqueous physical, small marine burrowing traces, and/or algal-laminated dolobindstone with evaporite nodules

Front 60

Sand sheet facies form and are found:

Back 60

-eolian sand sheet facies develop where the sand supply is either too low for dune development or where the sand is not mobile
-these conditions are often found around the fringes of an erg

Front 61

Characteristic features of sand sheet facies?

Back 61

-horizontal to low angle wind ripple strata
-deflation lags of evenly spaced coarser (coarse to medium) sand
-isolated barchan dune deposits are sometimes found within the facies

Front 62

Rivers are categorized based on ________ and ________.

The two most important in the sedimentary rock record are:

Back 62

channel number & sinuosity

braided fluvial = multiple channels and low sinuosity (<1.5)
meandering fluvial = single channel and high sinuosity (>1.5)

Front 63

sinuosity

Back 63

the ratio of the length of the thalweg to the length of a straight line along the river valley

Front 64

thalweg

Back 64

the line connecting deep water at each river reach (a line that connects points of the deepest flow)

Front 65

What dunes are the best eolian reservoirs?

Back 65

transverse straight-crested ridge dunes which have tabular planar cross strata sets w/ avalanche strata

Front 66

How are linear (seif) dunes different from ridge dunes?

Back 66

- linear dunes have more continuity to their crestlines
- linear dunes are more widely spaced and larger than ridge dunes

Front 67

Braided fluvial rivers form in what conditions?

Back 67

-steeper gradients = 0.2 - 9 degrees
- high bed load to suspended load ratios (high competence, low capacity)
- flashy discharge

Front 68

The channels of braided rivers are characterized by the presence of _________ and ___________.

Back 68

transverse and longitudinal bars

Front 69

transverse bars

Back 69

-slip face (lee slope of grainflow deposits) oriented transverse to channel
-extend across most of the channel reach and usually attached to bank
-dm thick sets of tabular-planar cross strata; may include cosets

Front 70

longitudinal bars

Back 70

-slip faces oriented oblique to channel
-elongated longitudinally to channel and not attached to bank
-dm thick sets of tabular planar cross strata - internally complex

Front 71

The dominant record of braided fluvial systems is that of the _____________ facies

Back 71

channel fill facies

Front 72

channel fill facies of braided fluvial systems:

Back 72

base = erosional contact

channel lag of coarsest material including accumulations of logs; coarse sand with trough cross strata

transverse and longitudinal bar deposits

top = channel abandonment mud fill (low velocity allows this); if conditions appropriate paleosol (usually aridisols)

Front 73

Where do meandering rivers form?

Back 73

-gentle gradients < 0.1 degrees (usually a hundredth or a thousandth of a degree
-low bed load to suspended load ratios (i.e. rivers with high mud content)
-regular discharge

Front 74

As a river meanders, the elevation of the river surface is slightly ______ on the outside of a bend relative to the inside of a bend.

Back 74

higher on outside of bend

Front 75

_______ velocity flows develop under or near the thalweg

________ velocity flows develop along the inner part of the meander bend

Back 75

higher velocity - under or near thalweg

lower velocity - inner part of meander bend

Front 76

Helical flow makes water _________________ along the outside of a meander bend and __________________ along the inside of a meander bend.

Back 76

descend and accelerate along the outside of a bend

ascend and decelerate along the inside of the bend

Front 77

riffle

Back 77

the river reach where there is no helical flow

Front 78

As the sinuosity of the thalweg continues, ______ continues along the cut bank and _______________________ continues along the inside.

This process typically occurs sporadically with the river becoming temporarily in an ______________ state.

Back 78

erosion along cut bank, deposition of lateral accretion bar along the inside

over-capacity state

Front 79

the inner bank of a meandering river becomes either of what two things?

Back 79

1. the side of nondeposition (lateral accretion surface)
2. draped with mud (lateral accretion surface drape)

Front 80

lateral accretion surfaces and drapes dip gently (_-_ degrees) towards the ______.

Back 80

dip 2-15 degrees towards the thalweg

Front 81

characteristic facies of a meandering channel?

Back 81

-erosional basal contact
-fining upward texture profile
-thinning upward physical structures with lateral accretion surfaces
-geometry is a narrow ribbon of sand with locallized thick areas (lateral accretion bar deposits)

Front 82

Crevasse splay facies occur when...

Back 82

when river water rises during flood conditions and the channel margins (including the levee) are breached (a crevasse). This results in a sudden introduction of water and sand + mud onto the relatively flat floodplain

Front 83

the _____ debris is deposited near the crevasse, and the _______ debris is deposited farther out on the floodplain

the deposited sand near the crevasse is known as a ________

Back 83

coarsest debris near crevasse; finer debris farther out on floodplain

crevasse splay

Front 84

facies characteristics of a crevasse splay:

Back 84

base = gradational contact by texture of interstratification

coarsening upward texture profile

critical climbing ripple strata --> super critical climbing ripple strata --> convolute strata

dm scale cross strata cosets

top = soil development
(note: geometry = very low profile conical section no thicker than the adjacent channel-fill facies)

Front 85

Floodplain mudstone facies occur...

Back 85

during times of river flood, mud and hydraulically equivalent debris (fine-grained organic material and micas) are deposited in low-lying areas outside of the river channel

Front 86

facies characteristics of floodplain mudstone facies include:

Back 86

-mudrock
-coal, where the climatic conditions are appropriate
-paleosols, increasingly better developed closer to channel
-geometry = encase channel-fill and splay sandstones

Front 87

water depth in lacustrine (lake) systems is a function of what two things?

Back 87

1. "empounded water" (water discharge - evaporation)
2. sediment influx

Front 88

the facies unique to lakes are __________

Back 88

sensitive to climate

Front 89

the facies of lacustrine systems are ______ and include facies seen in ______ settings like:

Back 89

complex; marine settings like deltas, beaches, lake-floor fans, etc.

Front 90

delta systems form at locations where...

Back 90

rivers carrying their sediment load exceed the capacity of marine processes to remove the sediment load

Front 91

delta systems are _______ by nature

Back 91

constructional (they prograde into the receiving basin)

Front 92

What are the 5 types of delta facies?

Back 92

1. distributary channel-fill
2. splay
3. delta plain
4. channel mouth bar
5. prodelta

Front 93

distributary channel fills

Back 93

-narrow relative to their thickness - resulting from sediment loading subsidence (prodelta muds compact/subside)
- fine to very fine sand; mud deposited as abandonment fill
- most of the fill is by vertical accretion (dune and ripple cross strata); lateral accretion is much less important

Front 94

splay (delta facies)

Back 94

-delta splays develop in the same manner as described for meandering fluvial systems; however, the currents are usually not capable of carrying material coarser than mud so delta splays have more silt & mud and are much larger than meandering fluvial crevasse splay facies
-silt with climbing ripple stratification and mud

Front 95

delta plain

Back 95

-the low-lying area between distributary channels
-the character of the facies depends on climatic conditions in the coastal region:
- in humid temperate areas --> coals & mud
- in arid areas --> shallow water carbonates
-locallized framestones can develop is the suspended sediment load is not too high
-tidal deposits are likely found in this setting

Front 96

channel mouth bar

Back 96

-at the terminus of each distributary channel the river is required to deposit its traction load, building a lobate accumulation at the end of the channel
-each channel progrades basinward, thus the channel mouth bar muddy sand facies is gradational downward to the deeper water prodelta mud facies
-gradual coarsening and thickening upward succession
-prone to slumping due to rapid deposition

Front 97

specific structures (physical and biogenic) in channel mouth bars reflect the dominant process in delta development:

Back 97

river dominated --> ripples and dunes; channel erosion above

tide dominated --> elongate sand bodies with tidal bundling

wave dominated --> foreshore strata, offshore sand bars and wave ripples

(biogenic structures are abundant, especially dwelling traces)

Front 98

Prodelta

Back 98

-mud is deposited basinward of the channel mouth bars and delta plain resulting in a 1-2 degree sloping surface known as the prodelta
-mud deposited by suspension sedimentation; typically reworked into biogenic traces
-prone to slumping because of rapid sedimentation and the discharging of methanogenic gas

Front 99

estuaries are:
they form where:

Back 99

-elongate indentions along a coastline
-form where rivers carrying their sediment load do not exceed the capacity of estuarine processes to remove the sediment load, or where the storage capacity of the estuary is greater than the sediment influx

Front 100

in the sedimentary rock record, estuarine systems typically develop under conditions of _________

Back 100

transgression - the coastal inlets are being flooded by rising sea level faster than the sediment can fill the accomodation space (esp. true during Holocene w/ rapid sea level rise following the melting of continental glaciers)

Front 101

4 estuarine facies?

Back 101

1. bay head delta (usually intermediate between tide and river-dominated, though usually w/ a strong tidal signature)

2. tidal marshes (tidal bundling and tidal creek channel fills)

3. barrier (shares characteristics of barrier island)

4. central basin (perhaps most distinctive)

Front 102

central basin (1 of 4 types of estuarine facies)

Back 102

-carries geochemical signature of "brackish water" or fluctuating marine and fresh water conditions (below low tide, lots of suspension sedimentation b/c water is fairly quiet)
-in some settings can exclude benthic biota
-in deeper basins, anoxic bottom water and accumulation of organic carbon debris (w/ sufficient quantity & burial --> good gas reservoirs)

Front 103

longshore drift

Back 103

occurs along many coastlines: waves approach the shore at an angle to the general trend of the coastline, causing longshore drift, which is capable of transporting sand long distances from where the sand is introduced to the basin by rivers

Front 104

consequence of longshore drift?

Back 104

the tendency for sand to fill in any coastal irregularities--thus the sand accumulates as islands or peninsulas separated fro the shoreline by lagoons (quieter bodies of water)

Front 105

What are the 3 main barrier island facies?

Back 105

1. Island core (Washover, Dunes, Beach)

2. Tidal inlet (islands segmented by inlets that allow the exchange of water driven by tidal current)

3. Lagoon (quiet water sedimentation behind barrier island)

Front 106

Island core

Back 106

-the main accumulation develops a shore parallel, elongate lense of sand

-complexly cross stratified eolian sand is deposited above sea level (that has a limited preservation potential)

-on the lagoon side, washover fans are deposited where storm waves have breache dthe island -- tabular planar cross strata (foresets dip towards land) with plant debris

-on the ocean side, the island is flanked by the foreshore and shoreface

Front 107

foreshore (beach)

Back 107

-breaker swash zone (within tidal zone/between high & low tides)
-low angle (2-10 degrees) parallel stratified, very well sorted sand
-quartz rich (only thing that can survive heavy abrasion), and heavy mineral lags if present
-shallow, high velocity flows

Front 108

shoreface

Back 108

-just offshore of beach
-range of waves = from low tide level out to depths where waves first affect the sediment water interface (~15 m water depth)
-divided into breaker zone and the outboard of breakers

Front 109

breaker zone of shoreface

Back 109

-highest current strengths
-moderate to well sorted coarser sands (even gravel) than foreshore
-rip current channels and bars as trough cross strata with complex current patterns
-few dewlling biogenic structures (b/c sand is so mobile)

Front 110

outboard of breakers (outer part of shoreface)

Back 110

-moderate sorted, finer sand than in breaker zone, increasing mud content with increasing water depth

deeper = wave ripples
shallow = wave-modified current ripples

-dwelling, feeding and escape biogenic structures increasingly more abundant toward deeper water (bioturbation so heavy locally that original physical structures obliterated)
-storm dominated coasts have hummocky cross strata (unidirectional & modified by oscillatory waves)

Front 111

tidal inlet divided into...

Back 111

divided into inlet fill and tidal deltas

Front 112

inlet fill

Back 112

top = steep (up to 25 degrees) lateral accretion of beach sand

bidirectional dune cross strata

base = coarse lag including skeletal debris

Front 113

tidal deltas

Back 113

-tidal bundling in dune or delta front cross strata
-flood tide dominant direction on lagoon side
-ebb tide dominant direction on ocean side
-heavily bioturbated

Front 114

lagoon

Back 114

-deposition dependant on climate:
humid and temperate = mud and carbonaceous debris
arid = carbonates and evaporites
- geochemical signature variable between fresh, marine and hypersaline
-tidal marsh deposits at fringes

Front 115

Where does preservation of barrier island systems occur?

Back 115

where:
-sediment influx is great w/ continuous accomodation space development

or

-rapid increase in accomodation with low wave strength (sea level change or subsidence)

Front 116

in the barrier island systems, the preservation of only the upper part of the shoreface and lower parts of tidal inlet and lagoon occurs where:

Back 116

where there is a slow increase in accomodation with high wave strength (the rest is eroded away by waves attacking the shore)

Front 117

carbonate systems fundamentally contrast with clastic systems in that....

Back 117

carbonate systems rapidly fill any accomodation space provided (this is because the organisms that produce carbonate particles have a very high productivity potential)

Front 118

the rate of carbonate sediment production is _____ the rate of accomodation

Back 118

rate of carbonate sediment production is > or = rate of accomodation

Front 119

most carbonate facies successions are __________ or __________

Back 119

aggradational or progradational

Front 120

What are the two characteristic facies of carbonate tidal systems?

Back 120

1. supratidal
2. peritidal

Front 121

supratidal

Back 121

-flooded by highest high tide and storm surge followed by evaporation
-laminated algal bindstone (mm-scale laminated carbonate mudstone)
-dessication cracks and intraclast rudstone
-gypsum/anhydrite nodules or septated vugs
-typically experiences early dolomitization (dolostate)
-chickenwire fabric / enterolithic

Front 122

peritidal

Back 122

-within tidal range

-depends on wave energy:
low = algal bindstone (laminated and stromatolithic)
high = grainstone and packstone

- biogenic structures depends on salinity:
normal = common dwelling and feeding
hypersaline = rare; major exception are stromatolite structures

Front 123

Nearshore Carbonate Subtidal Systems facies are largely controlled by the ______ of the water across the carbonate platform, which in turn effects the ________ of the system

Back 123

salinity, ecology:
normal marine salinity = diverse marine fauna
hypersalinity = restricted faunal diversity, but can be large in numbers (due to smaller competition)

Front 124

typical facies of nearshore carbonate subtidal systems:

Back 124

-packstone and wackestone carbonate rock types
-grain types reflect chemistry of the water
-locallized development of framestone and bafflestone (patch reefs)

Front 125

Most clay is deposited near continents. Why?

Back 125

the two things that take clay out of suspension are cohesiona and biogenic processes (pellets) and these occur most often near continents

Front 126

Offshore Muddy systems facies:

Back 126

character of facies limited and includes:
-heavily bioturbated mudstone and claystone with carbonaceous debris

some common variants include:
-admixtures of planktonic calcereous or siliceous skeletals
-interbedded chert and phosphates (near upwelling zones)
-volcanic ash (near eruptive centers)

Front 127

B/C the offshore zone is typified by weak currents, how does the sand get to such water depths as in Offshore Sandy Systems?

Back 127

-strong storm surges force sand below fairweather wave base by deflected (Coriolis effect) density undercurrents = geostrophic flow
-shelf tidal and strong oceanic currents
-sands are reworked from relic sands deposited at former low sealevel stands

Front 128

facies characteristics of offshore sandy systems:

Back 128

-moderately sorted fine to very fine sand
-glauconite (a variant of illite clay) is common
-physical strucures depend on the dominant source of currents: (and accumulation vs. progradation)
storm currents = hummocky cross strata
tidal currents = tidal bundling and reactivation surfaces; large scale tabular planar sets or cosets
-biogenic structures common and consist mostly of dwelling traces

(note: geometry = sand sheets with irregular margins surrounded by offshore muds)

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Carbonate reefs and buildups form:

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at low latitudes (typically within <25 degrees of equator), where marine waters are warm, and away from clastic input

platform or ramp edge reefs = connected to continents
atolls = marine platforms not connected to continents

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preservation potential of deep marine sedimentary environments and facies?

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abyssal plain sediments very rarely survive into the ancient geologic record (older than Cretaceous Period) because these sediments are swept into subduction zones along ocnvergent plate margins

Front 131

olistholiths

Back 131

large blocks typically underriding the continental rise of shallow water sediments that have been displaced into deeper waters

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How does such coarse material get transported to realms that are mainly characterized by quiet water sedimentation (deep marine systems)?

Back 132

-by sediment gravity flows from the continental slope
-mostly by turbidity currents carrying sediment out of submarine canyons (canyons intersecting coarse materials in longshore drift)

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lithostratigraphy

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-length X length X length
-2 geographic dimensions and 1 thickness dimension

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chronostratigraphy

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-length X length X time
-2 geographic dimensions and 1 geologic time dimension, which usually is coaxial with thickness

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lithostratigraphic equivalency

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linked by similar physical rock characteristics

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biostratigraphic equivalency

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linked by similar fossil assemblages

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chronostratigraphic equivalency

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linked by same geologic age or geologic time span

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Principle of Superposition

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a stratum is younger than the rocks upon which it rests

(straightforward principle that establishes the relative ages of a succession of stratified rocks)

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Principle of Original Horizontality

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because most sedimentary particles settle from a fluid under the influence of gravity, the resulting stratification should be horizontal

therefore, steeply inclined strata must have suffered structural deformation after deposition

the exception to the above generalization is cross stratification, which develops by the migration of ripple and dune bedforms

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Principle of Original Lateral Continuity

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an individual stratum extend in all directions until it:

1. thins to a zero-thickness edge
2. terminates against the edge of basin of deposition (usually as unconformity w/ igneous rocks)
3. merges into laterally adjacent deposits

unfortunately, this has led to concept of "layer cake stratigraphy" whereas in reality original lateral continuity is appropriate only within the limits specified

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Rule of Cross-Cutting Relations

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a rock body r planar surface that cuts across or terminates other rock boundaries must be younger than the truncated rock body

this has come to be known as the "Rule of T's":
-the rocks associated with the hat of the T is younger than the rocks associated with the stem of the T

in stratigraphy, most useful in sorting the relative ages of stratal surfaces

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Principle of Included Fragments

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any rock fragment included in the body of another must be older than the enclosing rock body (in other words, such a fragment had to exist before t could be reworked and included in a younger rock body)

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Lithology

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the combined characteristics of a rock, particularly sedimentary rocks, and includes mineral compositon, texture, color, and a smaller scale stratification

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lithostratigraphic unit

Back 144

based on a "stratotype" (a typical example of the unit being defined that should be readily accessibly, preferably natural exposure)

criteria: lithologic characteristics, thickness, vertical and lateral (if known) contact relationships)

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What are the 3 basic lithostratigraphic units?

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1. formation
2. member
3. group and supergroup

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What are the two types of contacts?

Back 146

vertical and lateral

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vertical contacts

Back 147

sharp = abrupt vertical changes in lithology
gradational by textural or compositional changes
gradational by interstratification of lithologies

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lateral contacts

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pinch out = lateral termination to zero thickness
intertonguing = lateral change by interstratification
lateral gradation = lateral subtle change in texture or composition

Front 149

the chronostratigraphic relationships of most sedimentary rock successions are based on _________

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biostratigraphy

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biostratigraphic zones

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based on the "stratigraphic range" of a taxon (a named group of fossil organisms)
-interval over which a fossil (or taxon) is known to occur
-range is limited by its first appearance and last appearance
-can only be established after detailed studies over large geographic areas--ideally global coverage
-each zone is named from an "index fossil" (a fossil species most characteristic of that zone)

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What are the 5 types of biostratigraphic zones and what are they?

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1. taxon zone = range of a single taxon

2. oppel zone (concurrent range zone) = based on the overlapping ranges of two or more fossil taxa

3. partial range zone = gap between the ranges

4. lineage zone = gap between the first occurences

5. interval zone = gap between the last occurrences

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a succession of sediment is considered conformable when...

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sediment accumulation is continous through geologic time

Front 153

unconformity

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a stratigraphic surface where geologic time has not been recorded as a rock volume

instead, geologic time planes are captured on an unconformity surface

develops as a result of erosion or nondeposition

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lacuna

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the total geologic time not recorded

erosional vacuity + hiatus

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erosional vacuity

Back 155

the amount of geologic time not recorded as a result of erosion

Front 156

hiatus

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time where nondeposition was taking place

Front 157

rank the 4 types of unconformities in order of increasing magnitude of the lacuna:

Back 157

1. nonconformity
2. angular unconformity
3. disconformity
4. paraconformity

Front 158

Rank the 5 methods of correlation in order of reliability:

Back 158

1.continuous lateral tracing (physically demonstrating equivalency)
2. index fossils (biostratigraphy)
3. stratigraphic position using a marker bed
4. stratigraphic position w/o using a marker bed
5. lithologic similarity

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stratigraphic sequence

Back 159

a sedimentary rock unit bound above and below by unconformities (typically a disconformity)

Front 160

what is the basis for the topic of "facies architecture"?

Back 160

building blocks

Front 161

parasequence

Back 161

a conformable succession of shoaling upward facies that is bound on top by a marine flooding surface (paraconformity)

the fundamental building block of stratigraphic sequence

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retrogradational parasequence set

Back 162

vertical stacking records a basin margin (landward) shift of facies within the parasequences

Front 163

parasequence set

Back 163

a group of parasequences that have a distinctive stacking pattern

Front 164

aggradational parasequence set

Back 164

vertical stacking records a stasis in facies within the parasequences

Front 165

progradational parasequence set

Back 165

vertical stacking records a basinward shift in facies within the parasequences

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nonconformity

Back 166

-sedimentary rocks resting on igneous and metamorphic rocks
-suggests a long time period of exposure to erosion (lacuna is an erosional vacuity)
-the magnitude would not be as great for volcanic flows and debris that is essentially contemporaneous with the associate sedimentary rocks
-can transition regionally to an angular unconformity

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angular unconformity

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-rocks below the unconformity are tilted at a higher angle relative to the sedimentary rocks above
-suggests tectonic uplift and exposure to erosion (the greater the angular discordance, the more likely the lacuna is an erosional vacuity)
-can transition regionally into a disconformity

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disconformity

Back 168

-above and below the bedding planes have the same tilt
-visible, irregular erosion surface
-lacuna some combination of erosional vacuity and hiatus
-can transition regionally to a paraconformity

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paraconformity

Back 169

-above and below the bedding planes have the same tilt
-no visible erosion; lacuna likely dominated by an hiatus

Front 170

clues to a disconformity:

Back 170

-bedding planes have the same tilt but there is clear evidence of erosion along contact
-included fragments

Front 171

clues to a paraconformity:

Back 171

-unexpected vertical change in facies according to Walther's Law
-fossils you can date
-included rock fragments (indicate SUBSTANTIALLY younger)

Front 172

clues to a nonconformity:

Back 172

-if no contact metamorphism, likely a depositional contact
-also if no included sed. rock fragments

Front 173

clues to an angular unconformity:

Back 173

-application of superposition
-rocks below unconformity tilted at higher angle relative to above sed. rocks

Front 174

continuous lateral tracing

Back 174

-direct, continuous lateral tracing of a bed or particular stratal surface
-most reliable for outcropping rocks on surface
-also reliable for seismic reflection surveys, except for scale resolution

Front 175

stratigraphic position

Back 175

-relates equivalency to stratigraphic context
-reliable for outcrop and subsurface applications
-uncertainty reduced by using "marker bed"
-use stratigraphic units vertical distance from marker as a correlation criterion

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lithologic similarity

Back 176

-patterns of similar lithology of lithologic succession
-also used widely in subsurface for patterns in well log profiles
-most widely used and least reliable

Front 177

index fossil

Back 177

-basis for biostratigraphy
-reliability and resolution dependant on fossil taxa
-very useful in graphic correlation method

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5 ideal qualities of a marker bed

Back 178

1. a distinctive lithology and/or paleontology rare in the section under study

2. laterally consistent in thickness over a large area

3. may yield radiometric date (e.g. volcanic ash bed)

4. may have a distinctive well log profile

5. can be assumed to have been deposited along/on a horizontal plane

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What are hallmarks of a sequence boundary?

Back 179

erosional relief and a strong basinward shift in depositional facies across the unconformity

Front 180

the stratigraphic sequence (the rock volume) is made up of ____________ that typically progress upward from _________ to ____________ to _________-.

Back 180

parasequence sets that progress upward from retrogradational to aggradational to progradational

Front 181

maximum flooding surface

Back 181

the turn around from retrogradational to aggradational or progradational is known as the maximum flooding surface, which is generally regarded as the record of maximum rate of sea level rise

Front 182

What are the 3 systems tracts generally recognized?

Back 182

1. lowstand systems tract
2. transgressive systems tract
3. highstand systems tract

Front 183

What are the 3 components of accomodation space?

Back 183

1. sediment compaction
2. tectonic subsidence
3. eustacy
-glacial
-thermo-tectonic

Front 184

lowstand systems tract

Back 184

-deposition occurs when relative sea level rapidly falls and continues through a low position in a sea level cycle

clastic depositional systems:
-submarine fans
-deltas extending beyond the shelf break
-braided fluvial and estuarine deposited in the incised valleys

carbonate depositional systems:
-carbonate subaqueous debris aprons
-marginal reefs
-karsting of the former carbonate platforms

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transgressive systems tract

Back 185

-deposition occurs when relative sea level rapidly rises, particularly at a rate that is higher than the long-term sedimentation rate

clastic depositional systems:
-barrier island, typically only those facies below sea level
-shelf
-capped by a condensed section (nondepositional hiatus of the maximum flooding surface)

carbonate depositional systems:
-reefs and expansion of lagoon and peritidal systems

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highstand systems tract

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-deposition occurs when relative sea level slows in its rise and through early stages of falling

clastic depositional systems:
-deltas and barrier islands
-wide-spread shelf systems
-meandering fluvial

carbonate depositional systems:
-reefs, lagoons and peritidal
-evaporates under arid conditions

Front 187

sediment compaction

Back 187

local phenomena that is dependant on the compaction rate of the different sediment types

Front 188

tectonic subsidence

Back 188

vertical displacement of the crust, both locally and regionally variable in its creation, as well as destruction, of accomodation (also varies w/ different types of plate tectonic margins)

Front 189

eustacy

Back 189

global fluctuations in sea level which varies with storage of Earth's water in different repositories and the shape of the ocean basins

eustatic fluctuations operate as aperiodic and periodic cycles through a wide range of magnitudes and recurrence episodes

Front 190

glacial eustacy

Back 190

-the freeze and thaw of polar ice caps
-operates on time scales of 1^4 to 10^5 years (Milankovitch cycles)
-magnitudes of 100-200 meters

Front 191

thermo-tectonic eustacy

Back 191

-the lithosphere resides at different elevations depending on its thermal state
-rapidly spreading divergent plate boundaries are hotter, so the ocean waters are displaced on to the marie shelves and platforms, and vice versa
-assembly of supercontinents cause the continental lithosphere to reside at higher elevation because continental crust has lower thermal conductivity, and vise verse
-it operates at the time scales of 10^6 to 10^8 years
-produces fluctuations on the order of 100+ meters

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formation criteria (critical!)

Back 192

-lithologically distinctive (from both subjacent and superjacent strata)
-exposure is large enoug to be mappable at the surface (1:24,000 scale)
-must be specified by a stratotype from which it usually derives its name

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member

Back 193

-subdivision of a formation
-same general criteria apply, EXCEPT does not have to be mappable

Front 194

group and supergroup

Back 194

-collection of formations and groups, respectively
-same general criteria apply