W6L1: Terrigenous Sediments

relict sediment:

Sediments that are remnants from an earlier environment and are now in disequilibrium

what is hydrogenous sediment?

a sediment formed directly by precipitation of dissolved minerals from seawaater

what are the society islands?

a series of volcanic islands in the South Pacific that have experience weathering. Many are under the surface of water

what is a terra rosa?

a type of red clay

aeolian processes:

pertain to wind activity in the study of geology and weather; specifically to the wind's ability to shape the surface of the Earth

for a time frame up to 100,000,000 years, ____ has determined the type of margin that developed and controlled sedimentation

plate tectonics

where do glacial till and ice-rafted sediments dominate?

polar shelves

sediments transported via ice rafting are typically ___

poorly sorted

what is the distribution of hydrogenous sediments

present with other, more dominatn sediments

what is the source of biogenous sediment

organic: accumulation of hard parts of some marine organisms

Where does the Colorado dump its sediment?

pacific ocean

____ sands washed from adjacent land are important components of the sediments along continental margins

quartz

what are the two most common components of terrigenous marine sediments?

quarz and clay

the sands and muds on temperate shelves are usually supplied by ___

rivers

what is the main source of terrigenous sediments

rivers

when will precipitation dominate an environment?

when the precipitation is greater than evaporation

if you see a "random" spot in the deep sea with a lot of fine terrigenous sediment, how do you think it got there?

wind (aeolian) processes

what percentage of all ocean floor area does cosmogenous sediments cover?

0%

_____ of the world's shelves are covered with relict sediments that were formed about ____ years ago

1) 60% 2) 15,000

How are terrigenous sediments transported to deeper parts of the ocean?

1) aeolian 2) undersea sedimentary deposits (turbidites)

biogenous sediments are most abundant where ___, such as ____

1) ample nutrients encourage biological productivity 2) continental margins or areas of upwelling

What are the primary effect on the type of terrigenous sediments that end up in the oceans?

1) elevation of source region 2) weathering 3) types of materials transported 4) Reworking

Where would you expect the most runoff into the Indian Ocean to come from?

1) ganges river 2) Brahmaputra river 3) Indus river

Where would you expect the most runoff to the pacific ocean to come from (top 2)

1) hwang ho river 2) Yangtze river

what are the two major sources of cosmogenous sediments?

1) interplanetary dust that falls constantly into the top of the atmosphere 2) rare impacts by large asteroids and comets

what types of sandstones are there?

1) overbank 2) pebbly 3) Bedded 4) trough and planar cross-bedded

terrigenous sediments are delivered by ___

1) rivers 2) coastal erosion 3) wind (as dust) 4) volcanoes 5) glaciers 6) icebergs

for a time frame up to 1,000,000 years, ___ controlled sedimentation and caused rivers to deposit their sediments at _______ and ______

1) sea level lowered by glaciation 2) the shelf edge and onto the upper continental slope

what might you find below the major river deltas of the world, and what do they form here?

1) turbidites 2) abyssal cones

how long does it take for sand to settle 4 km deep?

1.8 days

what time frame would waves, currents and tides control sedimentation?

1000 years

how has the proportion of sediments changed over time?

15000 years ago, there was a higher proportion of glacial-marine sediment and biogenic sediment, and a lower proportion of relict sediments

how many types of sandstones are there?

4

how long does it take for clay to settle 4 km deep?

50 years

how long does it take for silt to settle 4 km deep?

6 months

what percentage of all ocean floor area do hydrogenous sediments cover?

< 1%

Where is the largest sediment discharge into the Atlantic ocean to come from from?

Amazon

Where would you expect most of the glacial sources of sediment to come from?

Antarctica, greenland and Canadian Arctic

aeolian processes are particularly prevelant in ___

Arabia, Australia and North Africa

T or F: the majority of weathering is chemcal

False; mechanical

where is the second largest sediment discharge river into the atlantic?

Mississippi

which rivers in North America discharge some of the most sediment globally?

Mississippi (#7) and Colorado (#10)

how long will cobbles take to settle 4 km deep?

NA

how long will granules take to settle 4 km deep?

NA

how long will pebbles take to settle 4 km deep?

NA

give examples of terrigenous sediments

Quartz sand, clays, and estuarine mud

most sediment deposits are composed of ___

a mixture of biogenous and terrigenous particles, with an occasional hydrogenous or cosmogenous supplement

describe quartz

a hard, relatively insoluble, very durable mineral that can withstand extensive weathering and transport

what percentage of all ocean floor area do terrigenous sediments cover?

about 45%

what percentage of all ocean floor area do biogenous sediments cover?

about 55%

other than continental margins, where do you see terrigenous sediments?

abyssal plains and polar ocean floors

where might you see manganese nodules (representative of hydrogenous sediments)?

along deep seabeds

globally, where do you see a large portion of silaceous ooze?

along northern coast of antarctica

where might you see phosphorite nodules (representative of hydrogenous sediments)?

along some continental margins

what is feldspar?

an important material in granite that ultimately combines with carbonic acid and seawater to form clay

what are turbidity currents?

an underwater avalanche of abrasive sediments; a means of transport for sediments accumulating on abyssal plains

which latitude regions have precipitation greater than evaporation?

around equator, and between 40 and 60 degrees

hydrogenous sediment is also called ___

authigenic sediment

what is the common source of hydrogenous sediment?

bacteria

the weathering of volcanoes in the ocean can cause ____

barrier reefs with lagoons in the middle

why is the highest precipitation weather regime not exactly at the equator?

because of shift in intertropical convergent zone northwards ??

what type of material would you expect to be transported the shortest distance from its source?

bedded conglomerate (Sheet floods)

where do you find siliceous ooze dominates?

below about 5 km

which latitude regions have evaporation greater than precipitation

between 15 and 40 degrees and above 70 degrees

what is the second-most abundant marine sediment?

biogenous

which covers a larger area of the ocean floor: terrigenous or biogenous sediments?

biogenous

what constitues gravel?

boulder, cobble, pebble, granule

how are terra rosa's formed?

by the weathering of limestone: clay contained within limestone rock is left behind. When above the water table, iron oxide forms in the clay (making it red)

how is clay carried to the ocean?

by wind, rivers or streams

give examples of biogenous sediment

calcareous and siliceous oozes

where is the lowest distribution of quartz (detrital) in the pacific?

off the western coast of usa

what is clay composed of?

clay

what is the chief component of soils?

clay

what is the order of grain diameter between marine sediments (smallest to largest)?

clay < silt < sand < gravel < boulders

mud grain diameter lies between those of ____ and ___

clay and silt

Within turbidites, what would you expect the grain sizes to be?

coarsest at the bottom and finest at the top

what does compaction of gravel create?

conglomerates

what type of sediment is the least abundant?

cosmogenous sediments

As you go from areas of high relief to plains, mechanical weathering ____

decreases

turbidites?

deposits produced by turbidity currents; mostly consists of sands and silts, but a few are composed of gravels

sediment is sorted into ____

different sizes

where are biogenous sediments distributed

dominant over deep-ocean floor

most organisms that produce biogenous sediments _____

drift free in the water as plankton

what are common causes of turbidity currents?

earthquakes

average grain size reflects the ____

energy of the depositional environment

the higher the elevation of a source region, the higher the potential for ____

erosion and thus deposition

what is the source of terrigenous sediments?

erosion of land, volcanic eruptions, and blown dust

how does elevation change as you enter the ocean?

goes from high to low - causes smaller particles to be carried furthest

Where are terrigenous sediments typically seen on the globe?

on continental margins

what is the source of the quartz and clay that makes up terrigenous sediments?

granite

what constitutes aeolian processes?

hurricanes

what river discharges the most sediment per year, globally?

hwang ho (Asia); discharges 2100 million tonnes/year

when might you see rapid deposition of hydrogenous sediment?

in rapidly drying lakes

clays are more likely to be found ___ in the oceans

in the abyssal zone (deep ocean basin)

how does weathering effect terrigenous sediments in the ocean?

increased weathering of sediments on land (via precipitation) will increase erosion and runoff, increasing transport of sediment to oceans via rivers and streams

worldwide distribution of recent shelf sediments by composition is strongly related to _____

latitude and climate

which areas have absolutely zero chemical weathering?

lowlands with inland ice, and mountain ranges (i.e. glaciated areas)

give examples of hydrogenous sediments

manganese nodules and phosphorite deposits

occasionally, cosmogenous sediment includes _____

microtektites

where is the highest distribution of quartz (detrital) in the pacific?

middle, at about 30 degrees N

describe the cycle involving terrigenous sediments

mountains rise as plates collide, fuse and subduct. The mountains erode, and sediments are transported to sea via wind and water. sediments collect on sea floor, and travel with the plate. They are either uplifted or subducted, and made into mountains where the cycle begins again

what does compaction of clay create?

mudstone

what are some different types of materials being transported?

mudstone, sandstones, massive conglomerates, debris, bedded conglomerate, and volcanic ash

how are neritic sediments different from the deeper basin floor sediments?

neritic sediments consist primarily of terrigenous material contains coarser sediments, and lower proportion of biogenous sediment. Deep-ocean floors are covered by finer sediments, and have a greater proportion of biogenous sediment

what does compaction of sand create

sandstone

____ is a strong function of sediment size

sediment mobility (e.g. settling velocity)

Biogenous sediment:

sediment of biological origin; organisms can deposit calcareous or siliceous residue

what are cosmogenous sediments

sediment of extraterrestrial origin

turbidites build _____

sedimentary deep-sea fans adjacent to the base of the continental slope

pelagic sediments:

sediments of the slope, rise and deep-ocean floor that originate in the ocean

mudstone is also called __

shale

if you see a turbidite with a mix of remnants of shallow water organisms and deep water organisms, where did each remnant come from?

shallow water organisms: from areas where the density current originated Deep-water forms: existed in the area where the load was deposited or where the current followed

what is silt composed of?

silt

what does compaction of silt create?

siltstone

what is the basis of sediment classification?

size and origin

give examples of cosmogenous sediments

tektite spheres and glassy nodules

where do sands and muds typically dominate?

temperate shelves

which sediments dominate in total volume?

terrigenous

how does elevation of source region effect types of terrigenous sediments in the ocean?

the higher the elevation, the higher the energy thus the increased ability to carry sediments to the ocean

Ice rafting:

the transport of various material by ice; objects deposited on ice become embedded in the ice., and when it melts after drifting, these objects are deposited onto the bottom of river beds or ocean floors

geologic controls of continental shelf sedimentation must be considered in terms of a ___

time frame

clays will settle _______

to the deep-ocean floor

the presence of material on the ocean floor via ice rafting is useful to ___

track the history of iceberg dischage, glacial melting, and climate change

microtektites:

translucent, oblong particles of glass; thought to form from violent impact of large meteors or small asteroids on Earth's crust

which latitudes would you expect lots of weathering to happen, and thus more terrigenous sedimentation deposition in oceans?

tropical

the amount of mechanical weathering is highest in ____ areas that are _____

tropical areas that are at a very high elevation

where do calcareous biogenic sediments dominate?

tropical shelves

as you go from tropical to arctic, what areas have highest weathering?

tropical, subtropical, and humid temperate areas

T or F: glacial sediment grain diameter is very broad

true: ranges from clay-size to gravel size

what is the distribution of cosmogenous sediments?

typically in very small proportions (< few ppm) mixed with more dominant sediments

what time frame would lowered sea level from glaciation control sedimentation?

up to 1,000,000 years

what time frame would plate tectonics determine sedimentation and the type of margin?

up to 100,000,000 years

what constitutes sand?

very coarse sand, medium sand, fine sand, and very fine sand

hydrogenous sediments usually accumulate ______

very slowly

what is tuff?

volcanic ash

for a time frame of 1000 years, ____ control sedimentation

waves, currents and tides

what is the only thing with a grain diameter as large as boulders?

whale earbones

What is reworking?

when over time the sediments from low tide are brought offshore to the middle of the ocean