Chapter-5 Sediments and Surface Transfers Flashcards
are fragmented materials that originate from weathering and erosion of rocks or unconsolidated deposits, and are transported by, suspended in, or deposited by water
Sediments
soil material subsequently transported away from its source, mostly by water
Sediments
is essentially the erosional environment (source of sediment)
The Land
is essentially the depositional environment (sediment is buried beneath subsequent layers)
The Sea
Sedimentary materials:
Sandstone
Clay
Limestone
mineral grains (mostly quartz, muscovite), rock fragments and volcanic debris
Sandstone
– breakdown products, organic debris mainly dominated by plant material
Clay
organic debris dominated by marine shell debris, dominantly calcite solutes from sea water due to biological activity
Limestone
– movement of sediments
Sediment Transport
– how sediments are collected and added to a landform or landmass
Sediment Deposition
is far the most important agent of sediment transport, followed by wind and ice.
Water
– when suspended in water, coarser debris have lower velocities than finer debris.
Water’s ability to transport sediment depends on its velocity
Stoke’s law
Note:Larger particles can only be moved by faster flows
Therefore, sediment is sorted during water transport
works on the steeper slopes producing landslides and colluvium (loose unconsolidated soil in hillsides)
Gravity
moves only fine particles
Wind
transports are powerful, but restricted by climate
Ice
may blast debris over limited distances
Volcanic Activity
Types of Sediment Transport:
Water Stoke's Law Gravity Wind Ice Volcanic Activity
sorted and stratified, mostly sand and clay. Mostly forms alluvium and lake sediments
Water on Land
final destination of most sediment. Sorted and stratified in beds. Turbidity currents carry sediments into deeper basins
Sea
– unsorted debris dumped in the melt zones of glaciers
Ice
Types of Sediment Deposition
Water on land
River Deposition
sea
Ice
the process by which a weak, loose sediment is turned into a stronger sedimentary rock. Also known as diagenesis in geology and consolidation in engineering.
Lithification
three main processes of lithification:
COMPACTION
CEMENTATION
CRYSTALLIZATION
– restructuring and change in grain packing, with decrease in volume due to burial pressure, with consequent reduction of porosity as water is squeezed out.
Compaction
the filling of the inter-granular pore spaces by deposition of a mineral cement brought in by circulating ground water.
Cementation
– small scale solution and deposition of mineral, so that some grains become smaller and some become larger. Similar to cementation, but results are stronger mosaic texture.
Crystallization
– formed by weathering processes that break down rocks into pebble, sand, or clay particles by exposure to wind, ice, and water (moving fluids) aka Detrital Rocks
Clastic Sedimentary Rocks
– formed by chemical reactions and precipitation of different elements dissolved in water, chiefly in the ocean aka Chemical Rocks
Non-clastic Sedimetary Rocks
– composed of rounded gravel, pebbles, cobbles, or boulders along with similar rock pieces
Conglomerate
– similar to conglomerate except its gravel, pebbles, cobbles or boulders have a sharper, angular shape
Breccia
–composed of sand
Sandstone
composed of silt
Siltstone
composed of clay-sized particles (smaller than 4 micrometers in diameter)
Shale
– composed of the mineral calcite, may contain or may be made of marine fossils, formed by precipitation from water
Limestone
Clastic Sedimentary rocks:
Conglomerate Breccia Sandstone Siltstone Shale
– composed of sodium and chlorine, formed by evaporation. Also known as rock salt
Halite
– composed of gypsum, formed by evaporation
Rock Gypsum
– composed of microscopic mineral grains of quartz, very hard with sharp edges
Chert
Non-Clastic Sedimentary Rocks:
Shale
Halite
Rock gypsum
Chert
Types of Sedimentary Structures
Stratification/Bedding Cross-Bedding Graded Bedding Ripple Marks Mud Cracks Fossils
refers to the way sediment layers are stacked over each other, and can occur on the scale of hundreds of meters, and down to submillimeter scale. It is a fundamental feature of sedimentary rocks.
Stratification
are large scale reflection of transport of gravel and sand by currents that flow over the sediment surface (river channels). Sediment is moved up and eroded along a gentle up-current slope, re-deposited on the down current slope
Cross-Bedding
when the grain size within a bed decreases upwards. Commonly associated with turbulent suspension flows, they are initiated by slope failure, or earthquake that triggers down slope movement of sediment.
Graded Bedding
are produced by flowing water or wave action, similar to cross-bedding, only on a smaller scale
Ripple Marks
form when a water rich in mud dries out on the air.
Mud cracks
when remains of a number of biologically-created organisms exist in a sedimentary structure
Fossils
Types of Fossils
BODY FOSSILS – contain the actual organism remain
TRACE FOSSILS – contain geological records of a biological activity (footprint, burrows, imprints)
SEDIMENTARY ENVIRONMENTS (Depositional environments):
Continental Transitional Marine Evaporite Glacial Volcanic
Continental Depositional environment:
Alluvial
Aeolian
Fluvial
Lacustrine
Transitional Depositional Environment:
Deltaic
lagoonal
Beach
Marine Depositional Environment:
Shallow Water Marine
Deep water Marine
Reef
– is loose, unconsolidated environment which has been eroded, reshaped by water into another form and re-deposited in a non-marine setting
Continental Alluvial (Alluvium, Alluvial Fan)
– similar to alluvial fan, but deposition is via action of wind. Also known as dunes.
Continental Aeolian (Eolian)
processes associated with rivers and streams and the deposits and landforms created by them.
Continental Fluvial
– water localized in a basin, surrounded by land apart, may or maybe connected by any river or other outlet. Also known as lakes
Continental Lacustrine
– landform formed at the mouth of a river, where the river flows into an ocean, sea, estuary, lake or reservoir. Generally characterized by deposits of sediments.
Transitional Deltaic (River Delta)
– similar to lacustrine environment, except that it is a shallow body of water and it is separated from a larger body of water by small landmasses, barrier islands or reefs.
Transitional Lagoonal
– landform along the coast of an ocean, sea or lake, or river.
Transitional Beach
