Geology Exam 2

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where are there high nutrients but low chlorophyll concentrations why would this happen

20 % of the world's ocean North Pacific Equatorial Pacific Southern Ocean too far from land

continental slope depth

200 to 3000 m water depth; gradient 4o (up to 90o

what are borings

Benthic organisms burrow downwards through rock. Organisms do not coincide with time of deposition.

describe turbidites

Fining-upwards succession ('Bouma Sequence'). Event deposits. - Originating from turbidity currents. Sharp lower boundary. Gradual return to 'normal'.

what are physical sedimentary structures

Formed by abiotic physical processes

what are biogenic sedimentary structures

Formed by physical/chemical activities of organisms

what are concretions

Hard features forming before lithification. Slow chemical changescementation. - Cement often calcite or siderite • Many form around a nucleus (particle in center). - can be a fossil • Consists of material delivered by the surrounding sediment!

why should we care about river deltas?

Human societies ecologic diversity carbon cycle

what are hydrogenous sediments

Hydrogenous authigenic, precipitated from seawater economically important

what is a turbidite current

a suspended layer needing a trigger to occur (storm or SL increase)

What is anastomosing

different patters forming from many rivers

where are the wave dominated shelves

southern ocean; wind is more common since there are no continents in the way

describe bedforms

Interface between fluid and moveable bed. Can infer flow depth, paleo-direction, and current strength. Can also be load structures.

Define stagnation

state of being inactive and not moving or changing

what causes a stronger contour current

steep slope

how do cuspate deltas form

strong wave influence

what is a popular example of cosmogenic sediments

KT boundary

what happens when continental shelves are widely exposed?

submarine canyons are cut and fluvial sediments more directly transported to deep ocean

what are turbidite beds

suspension clouds above sea bed

what determines the thickness of the cont self

tectonics dust deposits trade wind system

what is Estuarine Turbidity Maximum (ETM)?

Location of maximum suspended sediment concentration.

what is a primary sedimentary structure

Mechanical structures formed during the deposition of sediments (syn-depositional)

where are we trying crevasse splays approach?

Mississippi delta

what is the biggest delta

Mississippi i

what nutrients are important

N, P

4 types of sediment classes

terrigenous/Clastic Biogenic Hydrogenous Cosmogenic

describe water escape structure

Overburden weight lead to upward directed de-watering. Fluidization of either sand or mud beds. 'Chimneys' penetrating overlying beds.

what is the closest delta

Santee delta

what are cross beds

Sets of beds that are inclined relative to each other.

describe a bird foot delta

Widely spaced distributary lobes resulting in a claw like structure -RARE

what are turbidity currents

a rapid, downslope flows of water caused by high density due to a high suspension load.

what do carbonates tell us

a record of life and sea level, a record of ocean chemistry, insight into other planets, source of metals and hydrocarbons

describe cosmogenic sediments

• Permanent rain of cosmic dust. • Or... extra-terrestrial impact: rare, chemically unique stratigraphically important

what are terrigenous sediments made up of

• Siliciclastic grains + organic material + ferro-manganese crusts... • Detrital clay minerals, quartz, feldspars, ash...

how are burrows formed

•Benthic organisms burrow downwards through unconsolidated material.

describe bottom turbidity layer

➢Land-originating mud. ➢Suspended mud layer. ➢Suspension density controls where the layers will detach from the seabed.

accumulation rates calcareous ooze vs silicious ooze

calcareous is high accumulation in upwelling regoins

foraminifera

calcite tests, single celled ZOO PLANKTON

What forms lamination

- Pulse-like variations in sediment supply. • Tidal regime / Seasonal lake deposition / fluvial runoff changes. - Absence of bioturbation due to: • Either a very high sedimentation rate. • No oxygen available.

What does this mean for carbon sequestration?

-10 % of the marine carbon leaves the coastal ocean. -1 % of the marine carbon deposits permanently.

continental shelf depth

1 to ~140 m water depth; gradient <0.05o; average width ~78 km

threats to river deltas

1. Upstream river damming → Sediment retention 2. River embankment→ Reduction of flooding → Subsidence acceleration 3. Groundwater pumping 4. Land conversion 5. Sea level rise → Coastal erosion

downside of ocean iron fertilization

10 % of the emissions, 10 % of the ocean surface needed

Which of the following is not a problem associated with development in delta regions? 1) Flooding. 2) Nutrient-poor soils. 3) River channel avulsion. 4) Subsidence. 5) Salt intrusion. 6) Storm surges.

2) Nutrient-poor soils.

continental rise depth

3000 to 4000 m water depth; gradient: gentle and decreasing

What is lamination?

<1 cm beds of rich, organic material found in deep ocean

bottom boundary layer

= bottom nephdloid layer = bottom turbidity layer contains lots of suspended sediment

Describe graded bedding

As velocity decreases, large/dense particles settle first. Decrease in grain size from bottom of bed to top of bed.

why should we study the deep ocean

CO2 budget, Advancing energy extraction technology.

describe hydrogenous sediments

Clay minerals, cements - more volume; chemically important Often formed during diagenesis

where are we trying channelization?

Danube delta

how do contour drift deposits look?

Either as mounting elongated sandy deposits. Or as mud deposits covering very large area on the abyssal plain. (mountain or flat)

what causes the formation of turbidity currents

Pressure changes within the sediment (storms, sea level, earthquakes) Slope failures; fluidization of internal weak horizons

Types of sedimentary structures

Primary secondary physical biogenic

what are mud cracks

Reduction in water contentcontraction. Exposed/at surface shortly after deposition. Curl up = can indicate original orientation.

what are secondary structures

Structures formed after deposition (post-depositional)

why is the CCD higher in the pacific compared to Atlantic

The Pacific Ocean water is colder than the Atlantic Ocean water due to the global thermohaline circulation patterns

bounce marks

The tool approaches the sediment surface at a low angle and immediately bounces back into current

roll marks

The tool rolls over the sediment surface, producing a continuous roll mark

skip marks

The tool travels down current with a saltating movement, hitting the sediment surface at nearly regular intervals

What are turbidites and how do they form?

Turbidites are deep ocean sediments formed from the build up in the continental rise with mostly terrigenous sediments

what are flute casts

Turbulent currents scour the bottom and excavate tapered depressions = Erosion. • Typicallytear-dropshaped. • Tapered end points down stream. - Paleo-current indicators! circular shape

which of the following is not a major challenge faced by deltas in the next century a. increasing sediment supply b. rising SL c. development pressure d. river management

a. increasing sediment supply

why is our sediment distribution the way it is

above the lysocline Is carbonates so it is very productive

what does syndepositional mean

as it is depositing

beds become ____ towards lower boundaries

asymptotic

where are we trying the internal sub deltas approach?

atcbafalaya basin

what are the two carbon sources

atmospheric CO2 and biogeneous shells, test. limestone

where are cross beds common

beach deposits, sand dunes, river beds, tidal deltas

what results from wave dominated river deltas

beach ridges and spits

How are cross beds formed?

bedlam transport; sand moves along an eroded surface creating layers

example of carbonates

biogenous- cretaceous coccoliths

what shape of delta is the Mississippi delta

bird foot

3 shapes of river deltaa

bird foot arcuate cuspate

what happens below lysocline?

carbonate corrodes

how does turbidity maximum position change?

changes with tide cycle and water discharge

another name for turbidites

channel levee system

continental shelf sediment sources

clastic; Brought in, pre existing siliclastic vs carboclastic biogenous; produced in the ocean, silicious vs carbonaceous authigenic; formed post depositional (pyrite, phosphorite, evaporites)

are contourites fining or coarsening upwad

coarsening

what is reverse bedding

coarsening upward

what happens when we dam deltas?

conflict is created; interrupt sediment supply and they drown

where do continental rise sediments come from?

continental slope and submarine canyons

3 types of clastic deep sea deposits

contourites pelagite turbidite

what does the continental rise form?

create deep sea fans

what is herring bone cross bedding?

current changes direction through time

how do we fix delta flow?

cutting new channels, breaking banks to build crevasses, constructing small internal deltas in lakes and lagoons, or creating new larger lobes in areas protected from waves and tides

where are contourite drifts located

deep ocean; runs parallel to continental slope

describe turbidite systems

deep sea channel systems connected to continental slope canyons; leads into fine grained deep sea fans

difference between delta plane and mega delta plane

delta: 10 mi wide mega delta: 100-150 mi wide

what are turbidites

depositional beds resulting from turbidity currents

how is sediment supply transported

energy tidal forces (type of gradient; steep or shallow) sediment type size of deposit mouth

what might be an appropriate solution to prevent the agricultural land from flooding and address the same subsidence issue at the same time?

engineers cut into the embankment, and the river flows into a depression inside a polder called a beel. sediment is scoured from the river and deposited in the beel or washed downstream opening the river channel and raising the polders land

are boundaries erosional or depositional

erosional = time gap

how do you classify river deltas

estuarine coastline: low sediment supply deltaic coastlines: high sediment supply

What are cosmogenous sediments?

extraterrestrial origin stratigraphically important

true or false: the coastline supply to ocean is indirect

false; it is very direct

are turbidites fining or coursing upward

fining

are turbidites fining upward or coursing upward

fining upward

how do deltas keep up with rising SL

flooding; crevasse splays create layers on top of layers

where is flaser bedding common

floor/ebb currents

what current is associated with countourite current

geostrophic current

what are contourite drifts

geostrophic currents within water masses; long lasting

The Hjulstrom diagram shows the relationship between

grain size of transported sediment and water velocity

how does turbidity sediment move offshore

gravity with the gradient

what influences all types of sediments @ earth's surface?

gravity, life, climate

what results from tide dominated delta

great tidal range (200 m or so), reverse water flow, periods of stagnation, elongated bars

how has sediment supply increased

increased by 467% from anthropogenic soil erosion, construction activities, mineral mining

What is hummocky cross stratification?

indicator for storm deposits; goes up and down

difference between gradient size in delta front and pro delta

it is coursening upward; delta front is sandy, pro delta is silt and clay

what makes Mississippi delta fascinating

its a mega delta but has a small bottleneck

memorize CO2 buffer chart

kms

how do sandy bedforms with high sand supply look?

lots of sediment available, sand waves and sand banks

what are the units for river discharge

m^3/s

what occurs in the continental rise during SL low stand?

major sink of terrigenous sediment (receives more than it provides)

what are biogenic sediments

marine organism remains spatially important

how do we count phytoplankton cocentration

measuring chlorophyll concentration in the water column

how do river dominated deltas look

minor tidal influence with well defined levees and overbank areas - sediment building on levees create thin strips of land either side of the main channel

what is lenticular bedding

more mud present (calmer environment)

older water means what in terms of nutrients

more nutrients

What is flaser bedding?

more sand present; higher energy and more currents

what are depositional fans bordered with

natural levees

where are tide dominated continental shelves

near large ocean basins

what are bedforms

non depositional structures that preserve history

what causes a rise in the CCD/carbonate compensation depth?

ocean acidifies, carbonate levels drop

are we on a passive or active margin

passive

Coccolithophores

phytoplankton with calcareous plates SINGLE CELLED

what is primary productivity based of

phytoplanton

how do terrigenous sediments enter the ocean (2 main ways)

point source (rivers/fluvial input) dust input (africa)

describe a cuspate delta

pointy (tiber river delta in Italy)

are concretions post depositional or syndepositional

post depositional

what does coarsening upward mean

progradation or drop in SL

are bedforms progradational or retrogradational

progradational

most shelf sediments are..

relict deposits- older than holocene

what happens as global warming increases

river damming and riverbed mining decreases

what is sediment supply dependent on

river discharge

what is type of delta is the Mississippi River delta (___ dominated)

river dominated

what is dominant in a bird foot delta

river sediment supply

what is the nepheloid Layer

river sediment that goes into the ocean and can be surface, intermediate, or bottom depending on density. continuously occurs like a conveyor belt

How big are foraminiferans?

sand sized

what is dominant in an arcuate delta

sediment supply mixed with tides waves and ocean

what is bjerrum plot

shows buffering vs acidification

How big are coccolithophores?

silt size

memorize chart on sediment structures

slide right before fossil tracks

how does fine grain material transport

they cluster together (flocculation) which may eventually grow and break apart (occurs over and over)

where can we find carbonates

• Pelagic carbonates • Deep water mud-mounds • Cool-water carbonates • Terrestrial & Lacustrine • Soils • Travertine • Reefs

how do sediments lay on storm dominated clastic shelves

they fine offshore - Foreshore facies: sandy, shell fragments - Shore facies: sandy mud/muddy sand, bioturbated - Offshore facies: muddy deposits with well preserved organics

where do you find herring bone cross bedding?

tidal environment onlu

What is the dominant process controlling the shape of the Ganges River Delta coastline?

tides

brush marks

tool approaches sediment surface at very low angle

prod marks

tools reaching the sediment at a high angle

what does fining upward mean

transgression OR turbidite beds

what does detrital mean

transported by water

Describe an arcuate delta

triangular

what river basins make up the Mississippi River delta

upper Mississippi River basin, Ohio river basin, lower Mississippi River basin, red river basin, Arkansas river basin, Missouri River basin

where is the coarser material in a depositional fan

upper fan

describe the upper fan medial fan distal fan (draw them

upper fan: trunk channel medial fan: depositional lobes distal fan: pinching out

where do we see the highest chlorophyll contents

upwelling cells, wide continental shelves, arctic oceans

how does the trade wind system affect continental shelf

upwelling cycles blow water west towards Africa making it highly productive

what is a lamination called if they're deposited annually

varves

how do sandy bedforms with low sand supply look

very few sand ribbons, sand patches, and sand waves

How do sand particles look at tide dominated shelves

very sandy • Sand sheets with ripples: tidal currents <0.5 m/s • Sand waves (subaqueous dunes): tidal currents 0.5 to 1 m/s • Sand ribbons: tidal currents >1 m/s • Sand ridges: amalgamation of sand ribbons form sand ridges (tens of m high, many km across)

what type of climate do carbonates like

warm climate with lots of primary productivity

what do contourite drifts form from

water current + Coriolis force

what form oscillating ripples

wave motion back and forth

what are terrrigenous/clasic sediments

weathering & erosion of continents often brought in by rivers volumetrically important

study sediment distribution map

what card said

study pictures in notebook

what the term says

when do tide sheets form

when the tide is low

where do we use the lobe building approach

yellow river delta

describe siliceous ooze

• Biogenic silica• Mineral: opal• Diatoms, Radiolarians • Production Signal

Describe calcareous ooze

• Calcium carbonate Minerals: calcite, aragonite • Foraminifers, Coccolith - preservation signal

what controls the biogenic carbonate productivity

• Light • Nutrients • Turbidity/translucency • Water temperature - Salinity

what does carbonate solubility increase with

• Lower temperature.• Higher pressure.• Higher salinity.


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