STRATIGRAPHY AND SEDIMENTATION (MARINE AND TIDES) Flashcards
The shape and depth of the Sea ,
Ocean’s depth relative to Sea level
Bathymetry
Ave depth of Spreading Ridges
2,500 km
Ave depth to Ocean Floor
4,000-5,000 km
Ave depth in Trenches
10,000 km
What marks the transition from Oceanic to Continental Crust
Continental Rise-Continenal Slope
A steeply dipping part of conintental margn which has an angle of 2-7 deg
Continental slope
Gently dipping part of the continental margin near the sea floor
Continental Rise
The relatively flat part of the sea floor
Abyssal Plain
the purely continental part of the continental margin which is ths shallow marine terrace of the cont crust
Continental Shelf
The junction between continental shelf and Continental slope which is 200m below sea level at present day margins
Shelf Edge Break
Large areas of Continental crust covered by sea water and bordered by land masses which are connecte by straits to the oceans
Epicontinental Seas or Epeiric Seas
Beach Environment
Littoral Zone
Shelf area covered by water up to 200 m (shelf edge break)
Neritic Zone
shelf edge break (200m) to 2000 m (Continental Slope)
Bathyal Zone
2000-5000m
Abyssal Zone
5000m below
Hadal Zone
Between Mean High Water to Mean Low water
Foreshore
Between Mean Low Water to Fair Weather Wave Base
Shoreface
The area between Fair Weather Wave Base and the Storm Wave Base
Offshore Transition Zone
The region below Offshore transition zone below up to 200m or the shelf edge break
Offshore
The depth at which waves normally affect the sea bottom
Fair Weather Wave Bse
The depth at which high energy wavs generated by storms affect the sea bottom
Storm Weather Base
The water that is closest to the moon which experiences largest gravitational attraction and create a bulge of water
Tidal Bulge
Why is the other side of the Earth also expriencing tide?
Because Earth is also being pulled by moon’s gravity
How long is the diurnal cycle?
12.5 hours
Alignment of the sun, moon and th earth
Syzygy
When are the highest tides experienced on Earth?
Spring tides during Late March (Spring)
spring tides during Late September (Autumn)
Why is it so?
Because of the sumperimposed tidal cycles
(Diurnal, Neap-Spring, Annual tidal Cylce)
Highest Tidal Change in the World
Bay of Fundy, Atlantic Seabord of Canada
15m
This is created when coriolis influences tide level moving to the right in the Northern Hemosphere and to the Left in the southern Hemsphere
Amphidromic Cells
The center of each cell at which the tidal wave rotates and there is no water level change in the water ycle
Amphidromic Point
2m mean tidal range regime
Microtidal
2-4m mean tidal range regime
Mesotidal
> 4m mean tidal regime
Macrotidal
These are daily changes in the elevation of the ocean surface
Tides
Who first explained the tide phonemenon and what did he do?
Sir Isaac Newton applied the Law of gravitation
What causes tides?
Mutationsl Gravitational attraction between two bodies and because both atmosphere and ocean are fluids and are free to move, both are deformed by this force.
How many high and low tides do most places on earth experience?
2 highs two lows (Daily Diurnal Tides)
How many days does the moon revolve around the Earth?
29 days
Every how many minutes do tides shift later each day?
50 minutes
by how much is the Sun’s tide-generating effect compared to that of the moon
Only 46%
This occurs when the Earth sun and Moon system is aligned during new and full moons that causes larger tidal bulges (higher high tides) and larger tidal toughs (Lower low tides), producing a large tidal range
Spring tides (Springer - to rise up)
This occurs when the sun and moon are at right angles and each partially offsets the influence of the other causing the daily tidal range to be less
Neap Tides
What phases of the moon do Neap Tides Occur?
1st and 3rd quarter
Factors that influence effects of tides
1) Shape of Coastlines
2) Configuration of Ocean Basin
3) Coriolis Effect
4) Water Depth
How many tidal patterns exist in the world?
3
A tidal pattern characterized by a single high tide and a single low tide each tidal day
Diurnal Tidal pattern
Where in the world does Diurnal Tidal Pattern happens
Gulf of Mexico
A tidal pattern which exhibits two high tides an two low ties each tidal day with the two highs and two lows about the same height
Semidiurnal Pattern
Where in the world does semidiurnal tiday pattern common?
Atlantic Coast
Similar to semidiurnal except that it is characterize by a large iequality of heights on the two high and two lows. Or there are two different highs and two different lows in terms of height
Mixed Tidal Pattern
Where in the world does mixed tidal pattern common?
Pacific Coasts
The horizontal flow of water accompanying the rise and fall of tides
Tidal Current
Tidal currents that flow landward into the coastal zone as tide rises
Flood Current
Currents which flow seaward as tide falls
ebb Current
Periods of little or no current produced due to tides which separate flood and ebb
Slack water
Tidal waves within amphidromic cells results in a flow of water in a circular or elliptical pattern
Rotary Tides
Areas affected by alternating tidal currents
Tidal Flats
When or at what point is tidal current at maximum flow velocity?
Mid tide point
Where are tidal currents rapid?
In narrow places like bays, rivers, estuaries, straits ad others
When are tidal currents considered to be major agets of erosion and sediment tranport?
When tides move thru narrow inlets where they scour the narrow entrance to many harbors that woul otherwise be blocked
Deposits created by tidal currents
Tidal delta
a landward deposition in an inlet
Flood Delta
Deposition on the seward side of an inlet
Ebb Delta
How do tidal deltas form?
as a rapily moving tidal current moves through a barrier island’s into the quiet water of the lagoon, the current slows and deposits sediment.
A bipolar cross stratification chracterized by alternation directions of ripple and dune migration
Herringbones Cross-Stratification
Sed structures formed during slack water stages of tidal cycle which can also occur in rivers that have only seasonal flow
Mud drapes on Cross Beds
Formed by erosion of part (crest) of a bedform when a current is reversed and recommencement of migration in the direction of dominant flow reoccurs
Recativation Surface
A cyclical variation in the thickness of foreset laminae in cross-beds that may be attributed to variations in flow strength in the neap-spring cucles
Tidal Bundles
The depth to which surface waves affect a water body
Wave Base
Weather systems that have associated strong surface winds typically in excess of 100km/h and may affect both land and marine envi
Storm
in what part of the oceans or marine realm does storm have an impact
Shallow Marine - Shelf and Epicontinental Seas
deposits of storm processes
Tempestites
Literal tanslation of Tsunami
Harbour Waves
Whats the periods of Tsunami Waves?
10^3 to 10^4 seconds
Events which can trigger tsunamis
1) Subsea Earthquakes
2) Large Volcanic Eruptions
3) Submarine landslides
Characteristics of Tsunami Deposits
Poorly Sorte Debris containing mixture of depoits and fauna may be larger in size compared to storm deposits
Deep ocean currents driven by DIFFERENCE IN WATER’S DENSITY controlled by TEMP and SALINITY which is weaker than storm and tidal current but is larger in volume
Termohaline Current
Cold surface water descends at high polar lattitudes known as
Sink Pooints
Wind driven currents related to GLOBAL WIND SYSTEMS and is result of DIFFERENCE IN AIR MASS TEMP combined with Coriolis
Geostrophic Current
Dark green minerals in marine sediments composed of K-rich Mica
Authigenic and forms through gluaconitisation
Glauconite
Materials made up of any these distinctive, medium to dark green mineral
Glaucony
Implication of Presence of Glauconite
1) Reliable Indicator of shallow marine environment
2) Commonly occurs in CONDENSED SECTIONS - which are strata that have deposited at anomalously low sed rates which is tends to coincide with SEA LEVEL RISE
3) Can be radiometrically dated and the age will corresponds to the time of deposition
Whats the minimum level of P2O5 for a sed rocks to be considered Phosporites
15% P2O5
implications of Phosphorite Presence?
Sea Level Rise because phosphorites authigenic accumulation are favored by slow sedimanetation rates of other materials and are characteristics of Condensed Sections
A mudrock which have 1-15% Organic Carbon
Black Shale
Implication of Black Shale
Anoxic Environment of Formation or reducing conditions in the DEEP SEAS
Can occur in shelves provided the supply of organic matter is greater that the rate at which it can be broken down
Why are shelves habitable environments for many plantonic and Benthic ogranism?
Because waters are relatively oxygenated which are periodically swept by currents to bring in nutrienst
Adaptation which is recognized in the lifestyle of an organism
Functional Morphology
Part of the marine realm that has the most diverse assemblages of benthic organism
Shoreface Environments
What controls the abundance of planktonic organism?
Supply of nutrients and the surface temperature of water
High Plantnic remains indicate what water depth
Deeper water
Burrows vs Borings
Burrows:Soft = Borings: Hard
Small Vertical Tubes in the Sands Trace Fossils
Skolithos
Crawling Trail by a multilimbed organism which can be Trilobites
Cruziana - Sublittoral
A pellet-lined burrow which is identical to burrows made by modern Callianassid Shrimps
Ophiomorpha
A boring in rock or solid substrate which is similar to those created by Bivalve Lithopaga
Trypanites
What is the implication of Escape Burrows
Rapid Sedimentation by storms or Turbidity Currents
Escape traces ichnofossils
Fugichnia
Changes in Trace Fossil Assemblages
Ichnofacies
MAJOR DIVISION OF MARINE REALM
FACIES
Littoral Zone (Sandy Shore)
Skolithos - Vertical burrows, simple u-shaped or pellet lined (Ophiomorpha)
Neritic/Sublittoral (Shelf Zone)
Cruziana - Wide variety of forms, Surface tracks and trails, complex network of burrows and horizontal, Vertical Branching
Bathyal Zone
Zoophycos - variable partly radial form that may be tens of cm across
Abyssal Zone
Nereites - Regular surface seen on bed surface only which are characteristically feedc traces. Mostly have regular structure. Because of scarcity of nutrients.
Hardground Ichnofacies (Borings) - even Slow Sedimentation
Trypania Ichnofacies
Firmground Ichnofacies (Burrows) - relatively slow Sedimentation
Glossifungite Ichnofacies
Evidence of organisms disturbing sediments
Bioturbation
An improtant surface current in the Atlantic Ocean that flows Northwards along the east coast of the US
Gulf Stream
What factors influence global suface-ocean circulation
1) Global Wind pattern
2) Distribution of major landmasses
3) Spinning of Earth on its Axis
These are large whirls of water within an ocean basin
Gyres
What are the world’s five main gyres?
1) North Pacific
2)South Pacific
3) North Atlantic
4) South Atlantic
5) Indian
Where is the centre of each gyre situated?
at the subtropocs at about 30 deg north or south latitue
Other terms for the five world gyres
Subtropical Gyres
What is the rotation of the subtropical gyres in the Northern Hemisphere and Southern Hemisphere respectively?
N-CW, S-CCW
This is the phenomenon caused by earth’s rotation in which currents are deflecye the right in the northern hemisphere and deflected to the left in the southern hemisphere
Coriolis Effect
What are the four main current existing in Npacific Gyre?
1) N Equatorial Current
2) Kuroshio Current
3) N pacific Current
4) California Curent
How many years does it take to go all the way around the loob in Ngyre?
6 years
What are the four main current existing in NAtlantic Gyre?
1)Nequatiorial Current
2) Gulf Stream
3)N Atlantic Current
4)Canary Current
How long does it take to go completely around the Natlantic Gyre?
3 years
What is the direction of the wind in the Northern Indian Ocean during summer?
Wind blow from the Oean towards Asian Landmass
The only current that completely encircles the earth and flows around the ice-covered content of antarctica
West Wind Drift
Portions of Pacific, Atlantic and Indian Oceans south of about 50 deg S Lat
Southern Ocean or Antarctic Ocean
Which latitude have a net gain of energy?
Lower Latitudes
Which lattudes have a net loss of energy
Higher Latitudes
What equalizes latitudinal energy imbalances?
Transfer of heat by winds and oceans
How much of the heat transport is accounted by Ocean Water Movements?
01-Apr
What are the principal West coast deserts?
1) Atacama in Peru and Chile
2) Namib in Southwestern Africa
Driest desert on Earth with an average rainfall of not more than 3mm/0.12 inch
Atacama Desert
Why is Atacama desert’s aridity intensified?
Because of the ffects of the cold peru current which chills the lower atmosphere which in turn becomes very stable and resist upward movement necessary for precipitation-producing clouds
This is the temperature at which water vapor condenses which often happened in the presence of cold currents
Dew Point
This is the rising of the cold water from deeper layers to replace the warmer surace water and is a common wind-induced vertical movement
Upwelling
Occues when wind blows toward the equator and parallel to the coast and with the combined effects of coastal winds and coriolis effect cuase sruface water to move awar from the shore and as it moves awat, water from below upwells and replaces the one on the sufcae
Coastal Upwelling
Which parts of the world does upwelling happen?
western coasts of continents
What are the effects of upwelling?
Brings greater conc. Of dissolved nutrients such as nitrates and phosphates to the ocean suface which promote growth of microscopic plankton which then support extensive populatioons of fish and other marine organism
This has vertical component which accounts for the throrough mixing of deep-water masses which is a response to density diffrences among water masses
Deep Ocean Circulation
Another term for Deep Ocean Cicrulation
Thermohaline Circulation
What can cause increase of seawater density?
1) Decrease in Temperature
2) increase in salinity
Where in the world are seawater/surface conditons create the highest density water?
Near Antarctica
How many years do deep waters stay under the surface?
500 - 2000 years
