Pt 3

Question 2

¹⁴C half life

Answer 2

This is 5730 years which makes carbon 14 unuseful for dating things older than 50 kyr

Question 3

¹⁸O vs. evaporation, precipitation, glaciation, land, lakes

Answer 3

the heavier ¹⁸O is preferred in a liquid state so evaporation will leave more of the heavier isotope and precipitation will prefer the heavier isotope.

This means that during glacial highs the ocean has high ¹⁸O and during warm periods it has more ¹⁶O because ice partitions ¹⁶O.

This also means that at latitude extremes and at high elevation there will be less ¹⁸O.

As lakes become more arid they become enriched in the heavier isotope.

Question 4

Abrupt contacts

Answer 4

These are the most common contacts that directly separate lithologically different beds. AKA a sharp contact.

Question 5

Abyssal Plane Depositional Environment

Answer 5

These are dominated by hemipelagic muds and ooze oftentimes bioturbated. The water in the deep water is very cold but is oxygenated because of deep sea churning related to more briny fluid circulation (glaciers do not freeze salt)

Question 6

Accumulation and preservation space

Answer 6

The accumulation space is the area of elevation available for accumulating material.

There is an erosional line that defines the preservation space by being the space where migration will not erode the material.

Preservation space can change due to compression/subsidence, rising water table, or changes in migration.

Question 7

Acme zone

Answer 7

This is the zone of maximal abundance. It is important for climate studies and used in reference to pollen counts and similar measures that can be compared as a ratio.

Question 8

Actualism

Answer 8

The present processes approximate the past but it must be interpreted with a grain of salt.

Question 9

Aggradation

Answer 9

This is the vertical build up of the sedimentary sequence. It usually coincides with a relative rise in sea level that is even with the amount of sediment supply.

In comparison progradation is the lateral outward motion of sedimentary sequences.

Question 10

ahermatypic coral deposits

Answer 10

These will be more likely be framestones where the allochems are bound at deposition because of the calmer enviroment.

Question 11

Allochems

Answer 11

These include ooids, pisoids, peloids, oncoids, and intrachlasts. It includes any carbonate clasts with D>fine sand (63microns)

Question 12

Allochthonous carbonates

Answer 12

This is all carbonates with coarse grains (10% has D>2mm) that are not organically bound at deposition indicating that grains were transported.

If it is grain supported it is a packstone.

If it is matrix supported grainstone.

If there are more than 10% grains then it is a wackestone.

If there are less than 10% grains than it is a mudstone.

Question 13

Allocyclic succession

Answer 13

These are cause by external influences like tectonics or climate. They are widespread and not limitted to one basin.

Question 14

Alpha Decay

Answer 14

This is the release of ⁴He causing the daughter atom to have 2 less protons, neutrons, and electrons.

Question 15

Angular Unconformity

Answer 15

This is when younger sediment sits about older strata that is older and was tilted, folded, and eroded.

Question 16

Assemblage Zone

Answer 16

This is marked by the appearance of one fossil within an assemblage. It is notable because it is the time when all the fossils are present.

Question 17

Assimilation

Answer 17

This is the integration of gaseous ¹⁴C within CO₂ in organic compounds, primarily plants.

Question 18

Attentuation

Answer 18

This is the idea that high frequency waves do not penetrate deep into the subsurface and have lower resolution whereas long wavelengths have better resolution at high depths because they do not attenuate.

Question 19

Autocyclical successions

Answer 19

These are like cyclical successions that are controlled by interbasin processes and therefore lack lateral continuity.

This includes the tetonic spurts related to alluvial fan deposits.

Question 20

Back Barrier deposits

Answer 20

The sub-enviroments of this area vary with the barrier island configuration but can show signs of being marshy (anoxic, organics) to bidirectional channelized flow that produces lenticular and flaser bedding.

Question 21

Barred/Borderland Basins

Answer 21

These are “underwater lakes” related to shallow marine depressions that are in the “anoxic zone” where water does not circulate and is not readily replenished with oxygen. It occurs on the continental slope where deposition does not occur.

These basins are most common where structure controls (West Coast CA) and are significant because they, like lakes, accumulate alot of organic sediment which create oil shales and can record cyclical depositions related to paleoclimates. Additionally, ferromanganese and phosphorites can precipitate here.

Question 22

Barrier island facies from backshore to offshore

Answer 22

root traces within fine sands. coals and other lagoon deposits

Eolian dunes (trough cross beds, 3d ripples)

Swash-related deposits (planar beds or multidirectional trough cross beds). Well-sorted, mature sediments.

There are increasingly massive beds of coarse sediments as the breaker zone is at a lower depth.

alternating muds and sands grading into fine sands with bioturbation

Question 23

Barrier Island Facies Model

Answer 23

General shift from eolian to shallow marine.

Question 24

Barrier Island Reaction to Eustatic SL Shifts

Answer 24

Transgression: The Barrier islands erode and slump into deeper water

Regression: They prograde like shores or dunes. The Back-barrier becomes increasingly brackish and is capped by evaporites.

Question 25

Barrier Island Subenviroments

Answer 25

There is the subtidal/subaerial barrier-beach complex: Sand islands about 1-20 m thick and long. This protects the coast from high energy waves.

Back-barrier region: calm, swampy/marshy areas aka a lagoon

Inlet-Channel complex: This is the calmish breaks in the barrier islands that allow for water to transfer between the back and front areas.

Question 26

Base Level:

Answer 26

This is the plane/surface where total erosion=total deposition. It is usually just below the sea level for most systems and/or lake level also said to be where rivers end in a deposystem.

If sediments are above the base level, then deposition is a short-term placement

Question 27

Baseline

Answer 27

This is the “elevation” that separates erosion and deposition. It is most commonly marked by the current sea level.

Question 28

Beach Morphology

Answer 28

Moving seaward:

• Eolian dunes (backshore) grade into the beach that starts with the foreshore this area is below the high tide line
• This grades into a steeper subaqueous zone that is the surf zone
• The base of the surf zone is at the low tide line where another steep dip occurs and this is the breaker zone
• There is then another sloe and that becomes the transition zone and grades into ​offshore
• Nearshore describes the areas in the surf, breaker, and transition zone.

Question 29

Beta minus decay

Answer 29

This is when an electron switches to a proton increasing mass number by 1

Question 30

beta plus decay

Answer 30

This is when a proton switches to a nuetron and loses an electron.

Question 31

biofacies in submarine fans

Answer 31

Fossils (often broken and rearranged) are very important to these sedimentologists because they are indicators of depth.

Question 32

Calcium carbonate compensation depth

Answer 32

This is the depth in the ocean where supply=dissolution. It decreases towards the cold poles that can have more carbon dioxide in solution. The lysocline refers to the gradient of carbonate compesation.

Dissolution is preferred in environments with low T, low pH (basic), and low CaCO3. At the equator the warm water lowers the CCD because of the increased supply of carbonates.

Question 33

Carbon 14 formation

Answer 33

¹⁴N+ ¹nuetron -> +EMR -> ¹⁴C + ¹proton

Question 34

Carbon 14 vs. time

Answer 34

The production of carbon 14 changes with time so to calibrate its use we use the ratio of ¹⁴C/ ¹²C within tree rings.

Question 35

Carbon Cycle/places of assimilation

Answer 35

Carbon 14 is sequestered from the atmosphere either as CO₂ is plants which can then be eaten or as rain (H₂CO₃^-)

Either way it ends of in the ground or as runoff which can then end up in the ocean and sequestered as carbonates. It can also become gaseous again when it decays to ¹⁴N

Question 36

Carbonate ramps

Answer 36

These are similar to continental ramps but with carbonates. The inner shelf have grain/packstones, the outer shelf has pack,wackestones, the slope has wackestone with LS intraclasts that transition to deep water carbonates (micrites). This occurs on the inside of Florida. They differ from reefs sedimentologically by not having framestones or boundstones.

Question 37

Cenozoic fossils

Answer 37

Pollen, foramifera, diatoms, radiolarians, plankton, mammals

Question 38

chalk

Answer 38

An earthy LS derived from ooze. It forms in the deep ocean floor particularly near the equator and is more than 50% of the ocean floor and more than two thirds of carbonates.

Question 39

Chronostratigraphic Units

Answer 39

These are “reference” layers that are used to be related to other rocks. This is like the Jura section of W. Germany for the Jurrassic.

This where rock=time

Question 40

Chronostratigraphy and Geochronology

Answer 40

Chronostratigraphy is the practice of using observed time to define rocks and successions of rocks. Geochronology is the practice of geologic time.

Question 41

Clinoforms

Answer 41

This is a fancy term for inclined strata.

Question 42

Coastal Sand Belt

Answer 42

These are barrier islands. They form in wave dominated coastal systems.

Question 43

Common Decay series for geochronometry.

Answer 43

Uranium lead dating: This is on the scale of millions to billions of years.

Rb->Ar: This is on the scale of millions to billions of years but makes the bold assumption diffusion=0

¹⁴C : ~50 kyr

Fission tracking: 500kyr -> 1 byr

Question 44

Common Source of Radiogenic Isotopes

Answer 44

The most common source of radiogenic isotopes is from within Earth (lead, uranium, plutonium…)

Question 45

Common uses of absolute dating

Answer 45

Zircons: deriterial zircons can be used to find the absolute oldest time of deposition.

Authigenic minerals: Direct dating of K-spar using ⁴⁰K -> ⁴⁰Ar. This is good because argon is inert. Other gases react with the mineral and thus cannot be used.

Shells/bones/organics: ¹⁴C

Igneous associations: Date igneous intrusions and use logic to constrain system.

Question 46

Competence ADD FBD

Answer 46

The maximum particle size that a flow can move.

Determines by if the flow can exert a force that is greater than tau_c

Question 47

Concordance

Answer 47

This refers to how overlying parasequence beds are conformable. This is what is meant by concordance. It is a place of continuous building out.

Question 48

Concurrent Range Zone

Answer 48

This is the overlap of LAD and FAD. It is important because it constrains the system.

Question 49

Conformable strata

Answer 49

This is when there is unbroken/continuous deposition. Beds are separated by conformities and hiatuses are lacking.

Question 50

Contacts

Answer 50

These represent lithological unit interfaces

Question 51

Control Points

Answer 51

These are places in the rock record where we have absolute data to constrain the system of interest.

Question 52

Correlation

Answer 52

Relating units based on age, lithology, or fossil content in geographic space (x,y,z).

Question 53

Correlation chart

Answer 53

This relates formations or facies to time at various locations.

Question 54

Cosmogenic Isotopes

Answer 54

This is the formation of radiogenic isotopes from the interactions of atoms with electromagnetic radiation. This is most commonly seen with ¹⁴C.

Question 55

Cross section

Answer 55

This is the observed sequence of rocks as a function of depth.

Question 56

Curie Point

Answer 56

This is the temperature (~500^oC) that magnetically susceptible reorient with the local declination.

Question 57

Cyclical Sedimentation

Answer 57

This is strata that show characteristic patterns from repeated shifts in the depositional process.

Examples include turbidites, laminated evaporites, LS-shale sequences, coal cyclotherms, black shales, and cherts.

Question 58

Dating glacial deposits

Answer 58

These are generally difficult to date because they have very low biogenic materials but if they are interbedded with basalts like some in the Andes are it makes things easier.

Question 59

Decay Constants

Answer 59

This is marked by lambda and represents atoms/time period

Question 60

Declination

Answer 60

This is the directional vector of the magnetic field at a given point

Question 61

delta ¹⁸O

Answer 61

This is the ratio of ¹⁸O/ ¹⁶O *1000

Question 62

Diastems

Answer 62

These are short hiatuses like within microlaminae that are often ignored in the bigger picture.

Question 63

Discontinuity

Answer 63

This is when both rocks on a contact are sedimentary and of similar character but a clear erosional surface exists between the two surfaces.

Oftentimes the base of the younger layer has lag gravels eroded from the layer below. These are likely due to environmental shifts, or widespread shifts in uplift.

Question 64

Dolomite Problem

Answer 64

This is the issue that dolomite does not readily precipitate in normal conditions and requires a “pump” to be precipitated yet there seems to be a abnormally massive amount of natural dolomite in the geo-history of earth.

Question 65

Dolomitization

Answer 65

This is the diagenetic alteration of LS to produce dolomite. It occurs at a depth of 500-3000 m and requires Mg rich water circulating through relatively porous LS and higher temperatures.

Question 66

Downlap

Answer 66

This is the termination of inclined strata against a lower angle surface. It marks the seaward depositional limit and thus oftentimes represents progradation.

Question 67

Dunham Carbonate Classification

Answer 67

A classification system that enables classification via hand specimen that emphasizes the grain packing, micrite abundance, and grain binding.

Mud-supported rocks include mudstone (<10% grains) and wackestone (>10% grains)

Grain supported rocks include packstone (>1% mud) and grainstone (<1%mud)

Allochthonous is for coarse sediment not bound at deposition wheras autochtonoous is for coarse grains that are bounded at deposition.

Question 68

Epicontintental Seaways

Answer 68

These are like pericontinental seas but they are within the continent and are surrounded by land on both sides (Hudson Bay). They differ from normal seas because of limited fetch. This results in a large amount of organic shales similar to lakes with low wave circulation. They also can have storm dominated coastlines that create hummocky cross stratification.

Question 69

Episodic Sedimentation

Answer 69

This relates to Saddler’s studies and says that rapid events that deposit large amounts of sediment are more likely preserved and therefore the stratigraphic record is likely to be a series of episodic depositional events separated by non-deposition.

Question 70

Erosional Surface

Answer 70

These are surfaces that are subaerial uncomformaties that form during a sea regression

Question 71

Eustatic Sea Level/Eustasy

Answer 71

This is where the average sea level is relative to the Center of Earth.

Question 72

Eustatic sea level changes

Answer 72

This defines global shifts in seal level largely thought to be due to changes in contintental ice reserves, ocean basin volume, aquifer storage, and ocean temperature.

When there is an increase in seafloor spreading there is an increase in sea level.

Question 73

Evidence for uncommon events having higher preservation

Answer 73

If comparing extreme events (floods, meteorites, rock falls) they appear more often in the stratigraphic record than their recurrence interval would indicate

Question 74

Fabric

Answer 74

This is how sediments within a rock are related to one another. It can be said to be the internal organization of particles.

It is composed of grains, matrix, cement, porosity, permeability, grain contacts, and sorting.

Question 75

Facies

Answer 75

This is a recognizable lithology or group of lithologies. It is the “sum of a sedimentary rocks lithologic character and acts as a class of deposit type.”

They are not dependent on locale only on the nature of the rocks. They can be lumped together to create sequences of facies (Bouma Sequence).

These are objective observations of rocks that do not vary with time. interpretations vary with time.

Question 76

Facies features (10)

Answer 76

This includes grain size/maturity/composition, beforms, structures, geochemical character, diagenetic alternations, fossils, or geophysical character (polarity or magnetic susceptibility)

Question 77

FAD/LAD

Answer 77

This is the first appearance datum and the last appearance datum.

There is a regional and global distinction as well. Appearance is local and emergence is absolute.

Question 78

Falling Stage Systems Tract

Answer 78

There is a base level fall at the shoreline and forced regression of the shoreline. This is accompanied by subaerial erosion landward, high rates of progradation and offlap on the shelf-edge delta. There is significant progradation of deep-water lobes/splays.

Question 79

Ferestrae

Answer 79

These are fossil algea with holes.

Question 80

Flooding Surface

Answer 80

These are the sharp contacts that form during transgressive lags.

Question 81

Forced Regression

Answer 81

This is progradation driven by base-level fall which forces a regressive shoreline regardless of the sediment input. It will have progradation with downstepping (seaward movement of shoreline)

Question 82

Foreshore sediments

Answer 82

The primary process that dominates sediments is wave breaking and this is because as the wave depth approaches 0 the Froude Number approaches infinity (Fr=V/(gD)^.5) Which results in fine upper flow planar bed laminae with good sorting.

If there are larger particles there may be imbrication that is leaning in the foreshore direction.

Question 83

Foreshore, Backshore, nearshore, shoreface and offshore

Answer 83

Foreshore is the area that is flooded by tides daily

Backshore is the coast

nearshore is always underwater but waves occur

shoreface is the subtidal to wave base area

offshore is the region prior to breaking

Question 84

Formal Stratigraphic Units (2 types)

Answer 84

Formations: This is 1+ group of facies strictly defined by lithology and bounded by lithologic changes. These must be mappable at a regional scale at Earth’s surface and acts as the base unit for other lithostratigraphic units.

Allostratigraphic Units: These are mappable stratoform bodies defined by bounding.

Question 85

Formation Nomenclature:

Answer 85

This is “geographic name” + “formation” OR “rock type”

Question 86

Formations

Answer 86

This is a lithologically distinctive stratigraphic unit that is large enough to be mapped at a regional scale on Earth’s surface. These are often composed of 1+ lithosomes with member beds and groups/supergroups. They act as the base stratigraphic unit.

Question 87

Formations

Answer 87

This is a deposit that can be mapped on the surface. They are observed from the surface or mapped with seismology. They are gross lithology (sequence of facies) of a rock mass and represent a unit of stratigraphy.

They differ from facies by being a facies because they can be deposited in different sedimentary deposystems. Within a formation a facies may grade or extend beyond the formation and because it is an objective description the same facies can be found in multiple formations across the flobe.

Question 88

Fossil Use with abundance, body size, duration of existence, range, geography, and habitat

Answer 88

Abundance: increased abundance increases the probability of any fossil being preserved.

Body size: An increased body size decreases the preservation probability

Duration: Fossils that have been around for a very long time are abundant but they are not precise.

Range: Endemic (restricted) vs. Cosmopolitan (wide)

Biogeography: Some regional species are particularly useful for precision.

Habitat: some habitats (low E) are more likely to preserve fossils.

Question 89

Fractionation

Answer 89

This is the slight shifts in deposition based on atomic mass. These have the greatest impact on phase changes.

light isotopes tend to have slightly weaker bonds and are slightly more volatile.

Question 90

Froude Number

Answer 90

A dimensionless unit that describes how a surface wave passes through a liquid. The denominator describes the velocity of a surface wave through water and the numerator is the velocity of flow. Therefore a F_r<1 means that the wave’s velocity is greater than the flow’s.

F_r=V/(gD)^.5 D=water depth

Question 91

Full sedimentary cycle

Answer 91

Starting at a maximum flooding there is the onset of a forced regession

There is then progradation and subaerial erosion that ends with the lowstand system tract and the minimum flooding surface and there is a brief normal regression as the base level slowly begins to rise.

Rapid base level rise leads to backstepping and a trnsgression which ends with another short normal regression as base level rise slows.

Question 92

Genetically related sediments

Answer 92

This simply means the sediments were deposited in a laterally continuous segment aka Walthers law holds true.

Question 93

geochronologic units

Answer 93

This is the relative times based on type sections and chronostratigraphy. It was described before formalized time units so each passage of time is unequal.

It is based on superposition

Question 94

Geochronometry

Answer 94

This is the absolute measure of time by unstable isotope analyses. It was established very early (11 years) after Bequerel discovered radioactivity and was used in the early 1900’s to prove was much older than previously though because they forgot to consider that potassium decay in the crust creates a large amount of heat.

Question 95

Geomagnetic time scale before jurrasic

Answer 95

This is done through using core from some of the rift valleys that record polarity.

Question 96

Global Boundary Stratotype Section and Point (GSSP)

Answer 96

This is the “golden spike” used at the base of highest quality column that represents a geochronological sequence.

Modern days we use biostratigraphy or changes in isotopes to mark the shifts between time units.

Question 97

Gradational Contacts

Answer 97

These show a gradual shift in the depositional enviroment.

Question 98

Gravity Flows

Answer 98

Characterized by a mass of sediment forming a flow with or without significant fluid composition and is propelled by the particle mass.

This includes density flows (turbidity flows)

Question 99

Half life

Answer 99

This is the time it takes for have of the parent atoms to decay into daughter atoms and is given by ln(2)/lambda or .693/lambda.

Question 100

Hemipelagic muds

Answer 100

These are muds that are partly from continental sources. They are usually ~5% organics, ~40% silt and deposit through suspension settling. They are largely red and brown clays, loess from wind, glacial sediments, and colvanic ash.

Question 101

Hiatus length as a f(unconformity)

Answer 101

From the smallest to largest gap:

Paraconformity, discontinuity, angular unconformity, and non-conformity

Question 102

Hierarchy of Lithostratigraphic Units (8)

Answer 102

Supergroup

Group

Formation

Member: these can intraformational

Lens

Tongue: This is like a member that specifically begins in one formation and pinches out within another

Bed

Flow: This is like a bed reserved for volcanics

Question 103

Large scale high angle cross stratification

Answer 103

This is a term that describes the large troughs that form due to grain fall during dune migration. In comparison the low angle trough cross stratification is because of translatent ripple migration.

Question 104

Highstand systems tract

Answer 104

This is when there is little or deceleterating transgression so there is low rates of progradatation and aggradation. Base level rises at the shoreline and normal regression occurs

Question 105

How did we develop magnetic polarity

Answer 105

This was developed when using big magnets to track the sea floor and try to find German submarines in WW2.

Question 106

How does CaCO₃ extraction, photosynthesis, organic decay, feeding/deposition, and bacteria influence precipitation?

Answer 106

Extraction increases the amount of shells and exoskeletons which create more allochems/micrite.

Photosynthesis lowers carbon dioxide and increases pH. This increases the amount of ooids/micrite.

Decay of soft tissues increases pH and increases precipitation

Feeding and digestion creates pellets.

Bacteria conduct ion exchange and precipitas carbonates.

Question 107

How does sea level influence submarine fans?

Answer 107

This determines the type of sediment in the fan.

During low stands they are very sandy from beaches being eroded by rivers and subaerial exposure. During this time the fan also has less vertical accumulation and is much more planar.

During highs they are more vertical and have more muddy sediments. They tend to be restricted to the continental slope.

Question 108

Ideal Transgression/Regression Sequence

Answer 108

The ideal transgressive sequence will start on a beachfront environment with planar sands that transition to siltstones, shales, and then limestones at the highest sea levels. The reverse will occur during the following regression. The transgression usually does not exist.

Question 109

Inclination

Answer 109

This is a correction angle related to a deviation of magnetic north from vertical. At the equator inclination is 0.

Question 110

Induced/Anomolous Magnetic Field

Answer 110

This is a magnetically induced field carried by local materials like Fe₃O₄ (magnetite), FeTiO₃ (ilmitite), Fe₂O₃(hematite)

Question 111

Intercolated

Answer 111

This is interbeds that progressively fine or thicken.

Question 112

Interpretting shavian correlation slope change

Answer 112

A change in the slope either means that either section either increases or decreases sedimentation but the slope is a non-unique solution to be confident of which mechanism is dictating the curve. Look at the core to interpret the change in sedimentation.

Question 113

Intertonguing

Answer 113

This is a form of lateral discontinuity where blocky or bladey intermittent spurts of a different lithology exist.

Question 114

Is sedimentation quantized

Answer 114

Yes. Saddler’s studies show that the system is either depositing or not.

Question 115

Isochronous

Answer 115

This is the basis of sequence stratigraphy/correlative beds that looks as strata bounds as being from one point in time. When looking at isochronous surfaces, like bedding planes, we assume that they extend laterally to represent some time.

Question 116

Isolith Maps

Answer 116

These show how one unit shifts in thickness laterally.

Question 117

Isopach maps

Answer 117

These show lines of equal sediment thickness not of equal lithology

Question 118

Isotope

Answer 118

This is an atom with equal electrical properties (electrons and protons) but a different mass.

Question 119

lapout

Answer 119

This is a change in the depositional environment or a movement of the preservation space. It is hard to distinguish in outcrops because they are oftentimes small shifts in the strata angles.

Question 120

Law of “Faunal Succession”

Answer 120

This was William Smith’s (a UK canal engineer) idea that fossils changed in the stratigraphic record through a process.

Question 121

Lithology

Answer 121

The study and description of objective physical characteristics of a rock. Often segmented by color, rock type, mineralogy, grain size.
This is seperated into lithostratigraphic units that are rock units seperated by lithologic changes.

Question 122

Lithostratigraphic unit inputs (2)

Answer 122

Stratotype: This is the unique stratigraphy or type of rock unit that is exclusively correlated to lithology not time.
Lithosome: This is a rock mass with complex boundaries with other nearby rock masses

Question 123

Lithostratigrapy

Answer 123

The is the recognition, subdivision, equivalency of sedimentary rocks on the basis of lithology.

Question 124

Lowstand systems tract

Answer 124

This at a minimum flooding surface where there is a small base level rise at the shoreline and normal regression. It is marked by fluvial onlap, small rates of progradation.

Question 125

Magnetic Excursions

Answer 125

This is fluctuations of inclination within a given period of polarity. The magnetic field pole can vary by as much as 45^o. This changes the magnitude and direction of remnant sediments and can be used to have greater precision regarding the deposition age. Generally they occur on a timescale of 500-3000 years.

Question 126

Magnetic Reversals

Answer 126

This is the switch of the magnetic field (N and S switch). This happens between 100-1000’s of years. It occurs over a very short time period.

Question 127

Magnetic sediments

Answer 127

In low energy environments, as particles that are magnetically susceptible settle, they will reorient themselves with the local magnetic field. Thus their orientation is proportional to the orientation and strength of the magnetic field at the point in time they settled.

Question 128

Magnetic Susceptibility

Answer 128

This is the ease to which something is magnetically oriented. It is used in magnetostratigraphy to ID specific sediments, provenance, and correlation.

Question 129

Magnetostratigraphic correlation

Answer 129

This is the process of using control points and remnant polarities to identify when sediments were deposited. It generally assumes that bed thickness is proportional to how long it took to deposit the sediments which assumes that there are no hiatuses within the section.

Question 130

Main Magnetic Field

Answer 130

This is the magnetic field produced by the outer core and would be homogenous without local deviation.

Question 131

Marl

Answer 131

A mudstone with interlayers of siliclastic mud or silt that is torigenous.

Question 132

Mass Spectrometer

Answer 132

This is a fancy particle accelerator that put particles around a curve and uses the difference in mass to orient their path. They intersect a sensor at different positions and the position is proportional to their mass. The mass of the atoms is used to identify the elements present.

Question 133

Max low sea level in Pleistocenes

Answer 133

100-120 m below current sea level

Question 134

Maximum Flooding Surface

Answer 134

This is where sea level stabilized at its deepest point. It is seen in the seismic section by where the seaward downlaps switch from backstepping to prograding during regression.

Question 135

Measured Sections

Answer 135

These descriptions of a section of rock act as samples for the development of regional correlation charts.

Different measured sections are compared based on their marker horizon which is the known boundary, geophysical property, lithology, or datum.

Question 136

Mesozoic fossil assemblages

Answer 136

These are most notably marked by the Permian extinction

ammonites, forminferons, pollen, ostracodes, marine fossils

Question 137

Modern reef controls

Answer 137

Reef formers aka Corals: Hermatypic corals are tropical shallow corals that rapidly build

Ahermatypic corals are deep water corals that are very slow to build

Reef Binders: These are algaes that laterall bind things

Question 138

Net transport of sediment due to waves

Answer 138

There is an assymmetry of velocity where it peaks when moving beachward. This means that there is only transport in the forward motion of sediments.

Question 139

Nonconformity

Answer 139

This is when sediments overlay meta or igneous rocks. This represents a significant time gap, uplift, and erosion.

Question 140

Normal and Reverse Polarity

Answer 140

Normal polarity is black. Reverse polarity is white. We are currently in a normal version of polarity.

Question 141

Normal Regression

Answer 141

Progradation driven by sediment supply. Sedimentation rates outpace the rates of base-level rise at the coastline.

Question 142

Ocean Anatomy

Answer 142

Starting at a passive margin there is the Continental shelf (low dip), which then has the shelf break at ~100 km from the shore and depths of ~200 m. This is followed by the erosive continental slope (~4^o slope) and meets the continental rise which is subaqueous fans. This grades into the Abyssal Plane (slope=0) until the MOR is reached.

The only difference in an active margin is everything is called a trench.

Question 143

Oceanic/Deep-Water sedimentology

Answer 143

These are rarely studied because they only exist as ompholites, have very low sedimentation rates, and economic value.

Generally along the continental slope submarine canyons have turbidity flows and in the deep oceans there is very slow sediment accumulation from loess, glaciers/icebergs, and MOR’s.

Question 144

Offlap

Answer 144

This is the progressive offshore shift of updip terminations. It is marked by updip terminations ending on older beds. It is diagnostic for forced regressions and base level lowering. There are lower angle strata intersecting higher angle underlying beds.

Question 145

Oldest sea floor

Answer 145

This is the Jurassic oceanic plates that are on the East coast. This is the oldest constraint that we have for general paleomagnetism.

Question 146

Onlap and types

Answer 146

This is when low angle cross-strata intersect with a higher angled stratigraphic surface. It marks the lateral termination of a sedimentary unit at its depositional limit.

Types: Marine, coastal, and fluvial

Question 147

Onlap, coastal

Answer 147

Refers to the termination of low-angle strata against more inclined ravinement surfaces in the shallow water strata.

Question 148

Onlap, Fluvial

Answer 148

Refers to the termination of low angle strata against a more inclined terrestial surface. This occurs during base level rises. If it is a normal regression it will be on top of toplap surfaces and if its in a trasgression it will be on an subaerially eroded surface.

Question 149

Onlap, Marine

Answer 149

This is the termination of low-angle strata against a steeper stratigraphic surface against an underlying continental slope that is diagnostic of transgression.

Question 150

Ooze

Answer 150

This is biogenic mud that is common on the abyssal plane. There are two types:

Calcareous fine sand and siliceous ooze from radiolarians and diatoms.

Question 151

Paleozoic Fossils

Answer 151

Trilobite, canadats, graptolites, fosilinids

Question 152

Paraconformity

Answer 152

This is where there are parallel beds without distinct erosional surfaces that are oftentimes only confirmed because of dating methods

Question 153

Parasequences

Answer 153

These are genetically related sediment packages that form a sequence. They are bounded by a marine flooding surface or conformable surface with above/below beds. They are usually on the scale of ~1-20 m.

To analyze parasequence sets in terms of base level/sedimentation rates look at where units start and end to define if there is progradation, aggradation, or retrogradation.

Question 154

Pelagic sediments

Answer 154

These are derived from the ocean. They include pelagic clays that are derived from loess and calcareous/siliceous ooze.

Question 155

Peritidal Shoaling Cycles

Answer 155

This refers the cyclical carbonate beds related to Milankovitch cycles.

Thick beds relate to shallow water and shales are deep water. They may also include transgressive lags and drowned carbonate platforms.

Question 156

pH controlling factor

Answer 156

Biology controls pH by extracting CO₂, bioturbing the base, producing organic acids, and producing shells.

Question 157

Pinchout

Answer 157

This is a form of lateral discontinuity where the shift between lithologies comes to a point or an alternative wedge shape.

Question 158

Principle of lateral continuity

Answer 158

This says that sediments are generally laid down on horizontal planes that extend in xyz directions

Question 159

Principle of Lateral Continuity

Answer 159

This basically says that rocks extend laterally showing similar depositional environments and are shown in cross sections where measured sections act as samples related on marker horizons (chronostratigraphic layers), geophysics (magnetic susceptibility), lithology, or datum (base value=0)

Question 160

Prograding sabkah

Answer 160

While subtidal there are lime muds that has a sharp contact with peloidal grainstones marking the inter-tidal perdiod that transition to a stromatilitic boundstone. This becomes supratidal with the appearence of massive anhydrite, muddy evaporites, and topped with a salt crust.

Question 161

Progressive graded contacts

Answer 161

These show a gradual change in quality within differing beds. For example SS to sandy shale to shale representing prograding finer grains.

Question 162

Proximal vs. Distal Turbidites

Answer 162

Proximal turbidites refers to turbidites that have prominent A-C horizons and form on or near the continental shelf. They are up to a meter thick.

Distal turbidites have more intense C-E layers and refers to deeper ocean turbidites.

Question 163

Radiogenic Isotope Decay

Answer 163

This is when unstable isotopes radioactively decay creating new daughter atoms at a predictable rate that makes them very useful for timing things.

Question 164

Regression

Answer 164

This is movement of the shoreline towards the ocean or sea. It can occer due to a lowering of sea level or an increase of sediment

Question 165

Regressive Phase

Answer 165

This is when the sea level lowers.

Question 166

Relative Sea Level

Answer 166

This is the elevation of the water column with respect to a datum slightly below the ocean floor.

Question 167

Relative sea level changes

Answer 167

This represents local uplift, subsidence, or ocean upwelling because relative sea level is the sea level with respect to basement rocks.

Question 168

Relatively Conformable

Answer 168

This refers to a sequence that only has diastoms

Question 169

sabkah

Answer 169

These are supratidal flats flooded episodically during storms. They tend to be very flat with subsidence. They are similar to playas.

Commonly include algal mats, evaporites, dessication structures, thin muds, fine grained sands. They will tend to form marls.

Question 170

Saddler: Implications

Answer 170

Sections of sediment representing longer timespans are more likely to have non-deposition.

Question 171

Saddlers sediment accumulation rate studies

Answer 171

Hypothesis: If sedimentation is continuous then measured sedimentation rates should be independent of the timespan of deposition.

Data: 25,000 + data based on cores, ¹⁴C, other radiometric dating, and measured sections

Findings: The shorter the timespan of deposition, the higher the rate of deposition.

Question 172

Seismic Stratigraphy

Answer 172

This is the use of sound wave two way travel time and amplitude to “see” subsurface surfaces, differentiate materials, and then conduct sequence stratigraphy.

Question 173

Sequence

Answer 173

This is a genetically related package of sediment bounded at the top and bottom by sequence boundaries (significant stratigraphic surfaces marking a change in the depositional system). These boundaries are either unconformities or the down-dip conformable surfaces that can be regionally traced (downlap onto ocean floor).

They are usually on the scale of 1+ km and correspond to a full stratigraphic cycle of depositional environment shifts.

Question 174

Sequence of Marine Evaporite Precipitation

Answer 174

This depends on exact chemistry but,

~40 ppm CaCO₃ = calcite

~40-60 ppm (Ca,Mg)CO₃=dolomite

~60-270 ppm CaSO₄H₂o*2H₂O=gypsum + anhydrite (dehydrated gypsum)

>270 ppm NaCl = halite +- sylvite

Question 175

Sequence Stratigraphy

Answer 175

This is based on the idea of separating surfaces based on chronostratigraphic significance. It combines the two approaches of correlating rocks using lithology and facies to recognize packages of deposition. It is most often used to recognize a cycle of relative sea-level change and/or sediment supply.

Andy def: The study of rock relationships within the chronostratigraphic framework of unconformities and correlative conformities

Question 176

Sequence sub-division

Answer 176

Sequence -> Parasequence Set -> Parasequence -> Bed sets -> Beds -> Laminae Sets -> Laminae

Question 177

Shavian Correlation

Answer 177

This was created by an oil guy that thought that regional biases made biostratigraphy poor. The idea is to plot appearance vs. depth so that you can create a relationship between the depths of the two boreholes.

Question 178

small delta sign

Answer 178

This stand for the ratio of the heavy isotope to the light isotope. Mathmetically it is shown as 1000((sample-standard)/standard)

Thus positive values show a greater proportion of heavy isotope than is within the standard.

Question 179

Spontaneous Nuclear Fission

Answer 179

This is when atoms split, like within an atomic bomb. It is very rare but does occur in nature.

Question 180

Stable isotopes

Answer 180

These are isotopes that do not decay over time. They have similar electric properties but behave physically and sometimes chemically different.

Question 181

stratigraphic record completeness

Answer 181

This idea is that no section is ever fully complete because there is always some erosion or non-deposition. Completeness is a function of the rate of deposition at one point in time.

Generally beds represent “instant” deposition that are altered during non-deposition.

Question 182

Stratigraphic sequence features

Answer 182

There are two components, the depositional sequence which is the genetically related conformable sediments bounded by the uncomformitites/correlative uncomformaties.

Question 183

Submarine Canyons

Answer 183

These are about 100 meter deep subaqueous canyons that formed during the Pleistocene. These oftentimes lead into canyons that were never at the surface (1000’s of meters deep) that are from continued turbidity flows.

Question 184

Submarine fans

Answer 184

These are oftentimes at the base of the continental slope and are large wet alluvial fan like deposits. They are often sand dominated turbidites that have erosional features, troughs, tool marks, and soft sediment deformation.

Compared to alluvial fans these will have trace fossils, grey anoxic shales, pelagic sediments, and turbidites.

Question 185

Syndepositional deformation

Answer 185

This is related to soft sediment deformation common on deltas.

Question 186

Synthem

Answer 186

This is an allostratigraphic unit that is bounded by uncomformities.

Question 187

System Tract

Answer 187

These are a linkage of contemporaneous deposition systems forming a subdivision of a sequence. They are interpreted based on stratal stacking patterns, position within the sequence, and types of bounding surfaces. Their timing is inferred relative to a curve that describes shoreline base level changes.

This is the concept that certain sedimentation patterns can occur during linked shoaling cycles. They often include many facies that are not linked by the same environment but the same change in processes.

Question 188

Taxon Range Zone

Answer 188

This is the time range of a single species (LAD-FAD)

Question 189

Tempesites

Answer 189

These are sandy cross bedded beds that form from storms where the suspended sands rapidly settle out of suspension. Oftentimes this is couples with mudstones.

Question 190

Temporal Stratigraphic Categories

Answer 190

These are all conceptual categories

geochronological units are divisions of time based on the rock record and superposition

Polarity-chronologic units are divisions of time found via polarity

Dichronic Units: there are unequal spans of time that are identified because of diachronous rock bodies (rocks with 1 or more bounding surfaces that are not developed at the time of deposition aka time synchronous)

Geochronometric units: Isochronous units (of equal timespan) and are direct divisions of geo-time in years

Question 191

Time Divisions of rock and modifiers

Answer 191

This is the era (Mesozoic), Period (Jurassic), Epoch (Early/lower), Age (Hettongian) distinction.

It is academic

Modifiers include the early, middle, and late times which are abstract.

Question 192

Time-Rock Divisions and Modifiers

Answer 192

This is the erothem, system, series, stage, zone system that is used in the field.

The modifiers include lower, middle, and upper based on how someone would observe the rocks.

Question 193

Toplap

Answer 193

Termination of inclined strata against an overlying lower angle surface, mainly resulting from nondeposition or very minor erosion. Strata lapout in the landward direction at the top of the bed. This signifies the base level at the time of deposition. They are most common in normal regressions. Look for the upper beds becoming tangential shoreward.

Question 194

Topsets, Foresets. and Bottomsets

Answer 194

Topsets are fluvial deposits from the river. They are dominated by sands, gravels, muds, organics (from interweaved lagoons and marshes)

Foresets are silty sands with lightly dipping beds. Also called subaqueous delta plain.

Bottomsets are from suspension settling that are fine laminae that dip more steeply seaward. This is also called the prodelta.

Question 195

Transgression

Question 196

Transgression

Answer 196

This is the rise of ocean levels. It is unlikely to be preserved than regressive phases.

Question 197

Transgression

Answer 197

This is the term that describes the landward shift of the shoreline.

Question 198

Transgressional Lag

Answer 198

This is the term that underpins the idea that transgression is often not preserved within the sedimentological record. This is because the sediment will be deposited laterally and not vertically.

Question 199

Transgressive/regressive barrier island deposits

Answer 199

During periods of transgression the islands are eroded away and will often “slump” into the ocean creating soft sediment deformation structures

During periods of regression the barrier islands prograde to form lee side dune cross beds, sand avalanches, and slump structures. Of significance is that the back-barrier environment

can become isolated and thus grades into evaporites.

Question 200

Transgressive lag

Answer 200

This refers to how a rising sea level equates to a rising base level and thus the coast becomes the point of deposition. This means that the transgressive sequence will jump from coastal (sandstones, shallow marine carbonates) to deep-water deposition (Limestone and shale) and not have the gradual transition that an ideal sequence would show.

This is why trawlers off of the East coast can find mammoth tusks with only loess and biogenic sediments covering them.

Question 201

Transgressive Surface

Answer 201

This is the surface the sea transgresses over. It seperates low stand system tracts and transgressive system tracts.

Question 202

Transgressive systems tract

Answer 202

There is a large base level rise and transgression of the shoreline. It is marked by retrogradation (backstepping) and aggradation with more fluvial onlap.

Question 203

Transition zone sediments

Answer 203

Finer very finely laminated sands that dip seawards

Question 204

Truncation

Answer 204

This refers to where strata terminate against an overlying erosional surface. This surface is sometimes uneven/hackly and the clinoforms do not end tangentially but abruptly.

Toplap may develop into truncation but truncation is more extreme and implies an angular unconformity.

Question 205

turbidite anatomy

Answer 205

Head: The erosive part of the flow that scours the base of the bed.

Body: A steady and uniform portion of flow that begins depositing a and b layers of the bouma sequence. It flows faster than the head.

Tail: Dilute part of the flow that can auto suspend fine particles.

Question 206

Turbidite/Bouma Sequence

Answer 206

.2-.4 m deposits derived form turbidity currents with an a-layer that has a scoured base, massive granular sands, and normal grading of coarse particles.

b layer is planar bedding from the upper flow regime.

c layer has ripple structures and represents the shift from upper to lower flow regimes.

d is laminated silts with tail ripples (lower flow)

e is pelogic (oceanic) and hemipelogic muds.

Question 207

turbidity flows

Answer 207

A type of gravity flow derived from sediment accumulation following seasonal floods, storms, quakes, or tsunamis and characterized by a shift from plastic to fluid flow. It has low viscosity, high turbulence, and lacks an internal structure.

Question 208

Type Section

Answer 208

This is the use of biofacies and absolute dating to relate chronostratigraphic units across vast distances like oceans and continents.

Question 209

Types of Density Flows

Answer 209

Homopycnal flow: This is when the density of the river ~ density of the water. This leads to rapid deposition (v~0)

Hyperpycnal flow: This is when the river is more dense than the water. It leads to currents that deposit fluvial materials at the basin base. This can create an anoxic environment in the base of the lake

This occurs in fluvial deltas.

Question 210

Types of Stratigraphic Units based on physics (5)

Answer 210

Lithostratigraphic Units: These are based on the law of superposition and superposition

Lithodemic Units: These are intrusions, deformed, meta rocks that do not conform to the law of superposition

Magnetostratigraphic Units: Units defined by remnant magnetic polarity.

Pedostratigraphic unit: 1+ paleologic (soil) horizons

Allostratigraphic units: These are mappable stratiforms (formations/layers) that have bounding discontinuities

Question 211

Types of stratigraphic units based on geologic age (2)

Answer 211

Chronostratigraphic units are bodies of rocks with known date of deposition that act as control points for other layers

Polarity-Chronostratigraphic Units: These are divisions of geologic time determined by the magnetic poarity.

Question 212

Unconformity

Answer 212

This is a time of non-deposition that is used for separating younger and older strata based on nondepositions, erosion, or weathering.

Question 213

Uniformitarianism

Answer 213

This says that the processes that occur now are those that occcured previously. It biases the gradual and continuous depositional events but stratigraphy is biased towards odd events that are more likely to be preserved.

Question 214

Using decays

Answer 214

Generally we use two decay series to better constrain the system. For example using ²³⁸U and ²³⁵U.

Question 215

Value of Shavian Correlation

Answer 215

It enables us to have a better understanding of how sediments were deposited on a regional lateral scale and enables us to have a prediction for missing boreholes. It is like psuedo-kriging.

Question 216

Walther’s Law

Answer 216

The deposits that form together laterally are superimposed on others vertically if deposition is continuous and post-depositional structure does not shift. The failure of walther’s law is when facies “pinch-out” which indicated that the sedimentological process has terminated laterally when deposition occured.

The implication is that vertical sections reveal lateral relationships.

Question 217

Water Depth

Answer 217

This is simply how high the average water column is with respect to the ocean floor.

Question 218

Wave Base

Answer 218

This is the depth where wave oscillation ceases. It is roughly .5*wavelength.

Near the shore the interaction of the oscillation of the wave causes shearing.

Question 219

What does the slope of a Shavian correlation mean?

Answer 219

The slope is related to the relative rates of sedimentation. Therefore shifts in the slope indicate a shift in sedimentation at one of the locations.

Question 220

Why do reefs not form near river mouths?

Answer 220

There is too much siliclastic sediment that fluctuates the water composition and blocks sunlight.

Question 221

Why is dolomite difficult to precipitate?

Answer 221

Mg(OH)₂ is stronger than ca(OH)₂ making it much less likely to react with carbonic acid and the kinetics for Ca is much more favored.

Dolomite is favored in high Mg/Ca ratio, low Ca/CO₃ ratio, low salinity or high T (T>100C)

Question 222

marine flooding surface

Answer 222

These are surfaces with evidence of abrupt shifts (ravinement surfaces) in water depth

Question 224

Ravinement surface

Answer 224

This is a minor erosional surface that forms at the trangressive lag.

Question 225

eustasy vs time

Answer 225

This describes the use of sequence stratigraphy and isotopic analysis to attempt to constrain eustatic shifts in sea level over geo-time.

This has shown large swings in the Pleistocene (+-150 m) and similar large swings throughout the Creteceous over short time periods