Lesson 1: Introduction Flashcards
broad scientific discipline that encompasses the study of all kinds of sedimentary rocks. specifically the:
-physiochemical properties
-mineralogy
-composition
-classification
-origin
-etc
sedimentary petrology
deals with the characterization of individual sediments. specifically:
-sizes
-physiochemical properties
-mineralogy
-depositional history (possible environment during deposition)
sedimentology
how do you usually start describing sedimentary rocks? and is this under sedimentary petrology or sedimentology?
sedimentary petrology.
start larger:
-size
-type, classification
-composition, mineralogy
-physical properties: color, sed features
difference between interbedded and intercalated
interbedding occurs when different lithologies alternate between layers.
intercalating is a special kind of interbedding in which the lithologies are from different depositional environments that are in close proximity to each other. (a layer gets inserted into an already existing sequence)
what does the sediment size tell about the depositional environment? ex.?
the larger the sediment sizes, the higher energy of environments and the closer proximity to the parent rock.
ex. breccias typically indicate upstream depositions with high energies, near the provenance (mountains)
2 importance of studying sedimentary petrology?
- genetic significance
-they reveal the nature of past environments (rocks themselves) and life forms (fossils), thus our only available clues to the earth’s surface history - economic significance
-metallic ores: iron, gold, uranium
-nonmetallics: natural gas, coal, sulfur, limestone, sand&gravel, silica for cement
-placer deposits
what are placer deposits?
heavy minerals that accumulate in basins bc of gravity
what percent do sedimentary rocks roughly cover the earth’s surface?
about 3/4 or almost 80%
what are the 3 things that affect the composition of siliciclastic sedimentary rocks?
- tectonic provenance
- kind of depositional basin
- depositional conditions present in tectonic setting
what are the 4 fundamental kinds of constituents?
- terrigenous siliciclastic particles
- chemical/biochemical constituents
- carbonaceous constituents
- authigenic constituents
depositional agents
water, wind, ice
describe the general process of sedimentary rock formation
formation of source rocks (intrusion, metamorphism, volcanism, tectonic uplift) -> weathering & dissolution of soluble constituents (explosive volcanism) -> erosion (transportation) -> deposition ->burial (+temp&pressure) -> diagenesis -> sedimentary constituents that make up the rocks
sediments derived from terrestrial environments and typically made out of silica
terrigenous siliciclastic particles
what are the range of sizes for terrigenous siliciclastic particles?
gravel to mud-sized
examples of silicates
quartz, feldspars, micas
forms of terrigenous siliciclastic particles
clasts (aggregate of minerals) or rock fragments (individual mineral grains)
rock types that make up terrigenous siliciclastic particles
igneous, metamorphic and older sedimentary rocks (as long as dominantly made up of silicate minerals)
how do secondary minerals (made up of terrigenous siliciclastic particles) form at weathering sites?
these minerals, particularly iron oxides and clays minerals, are formed from the recombination and recrystallization of chemical elements released from parent rock during weathering, during fluid phase then transported, not after deposition
other names for terrigenous silisiclastic particles
terrigenous constituents/ siliciclastic grains
how are terrigenous siliciclastic particles transported as? and where to? implication?
solids to depositional basins (thus extrabasinal origin, however some pyroclastic particles may form within the basin)
what common rocks do terrigenous siliciclastic particles make?
sandstone, conglomerates, shales
constituents derived from precipitates (minerals or mineral aggregates)
chemical/biochemical constituents
how do soluble constituents like calcite, gypsum and apatite form in basins?
chemical and biochemical processes lead to extraction of these soluble constituents from basin water, then moved about by currents and waves within the basin
example of chemical biochemical aggregate grains
carbonate ooids and pellets
aside from soluble constituents, what other precipitates can be formed through chemical and biochemical processes?
calcareous and siliceous tests or shells of organisms
example of intrabasinal sedimentary rocks
limestone, cherts, evaporites, phosphorites
constituents composed of carbonized residues of terrestrial (marine) plants and animals, and petroleum bitumen
carbonaceous constituents
three types of carbonaceous constituents
humic, sapropelic, bitumens
the woody residues of plant tissues
humic carbonaceous materials
humic carbonaceous materials are the chief component of most what?
coal
are the remains of spores, pollen, phytoplankton and zooplankton, macerated plant debris in water
sapropelic residues
sapropelic residues are the chief constituents of what?
cannel coals and oil shales
solid asphaltic residues that form from petroleum through the loss of volatiles, oxidation and polymerization
bituments
why do some siliciclastic rocks occur within the ocean?
because seawater has metal ions, i.e Zn, Cu, Fe that come from black smokers
what are black smokers?
hydrothermal vent chimneys formed by accumulations of iron sulfide (black in color)
are secondary constituents formed from precipitation of pore waters during burial diagenesis
authigenic constituents
what are the three sedimentary rocks that make up the bulk of all sedimentary rock records?
mudrocks (shales), sandstones and limestones
what kinds of materials are included in authigenic constituents?
silicate materials: quartz, feldspar, clay minerals, glauconite
nonsilicate materials: calcite, gypsum, barite, hematite
(they’re never the dominant type tho)
3 fundamental types of sedimentary rocks
- siliciclastic sedimentary rocks
- chemical/biochemical sedimentary rocks
- carbonaceous sedimentary rocks
further divided into grain size ang siliciclastic
in terms of volume how much do sedimentary rocks make up? of the earth’s total and the crust?
earth: 0.1%
crust: 11%
average thickness of sedimentary shell
2.2km, but varies
percentage of sedimentary rocks on continents?
about 70%, 29% sa earth’s surface
percentage of sedimentary rocks on continental shelf and slope?
13%, 14% sa earth
percentage of sedimentary rocks on ocean floors?
17%, 58% sa earth’s surface
5 types of sedimentary basins
- divergent settings
- intraplate settings
- convergent settings
- transform settings
- hybrid settings
2 basin subtypes under divergent setting sedimentary basins
- terrestrial rift valleys
- proto-oceanic rift troughs
3 subtypes of transform setting sedimentary basins
- transtensional
- transpressional
- transrotational
4 subtypes under hybrid setting sedimentary basins
- aulocagens
- impactogens
- successor basins
- intracontinental wrench basins
7 subtypes under intraplate setting sedimentary basins
- continental rises and terraces
- continental embankments
- intracratonic basins
- continental platforms
- active ocean basins
- oceanic islands, aseismic ridges and plateaus
- dormant ocean basins
10 subtypes under convergent setting sedimentary basins
- trenches
- trench-slope basins
- forearc basins
- intraarc basins
- backarc basins
- retroarc foreland basin
- remnant ocean basins
- peripheral foreland basins
- piggyback basins
- foreland intermontane basins (broken forelands)
commonly associated with bimodal volcanism
Terrestrial Rift Valleys
Incipient oceanic crust and flanked by young rifted continental margins
Proto-Oceanic Rift Troughs
Mature rifted continental Margins in intraplate settings at continental-oceanic interfaces
Continental Rise and Terraces
Progradational sediment wedges formed of rifted continental margins
Continental embankments
Broad cratonic basins floored by fossil rifts in axial zones
Intracratonic Basins
Stable cratons covered with thin laterally extensive sediment cover
Continental Platforms
floored with oceanic crust, no spreading or subduction
Dormant ocean basins
example of terrestrial rift valleys
rio grande rift
example of proto-oceanic rift troughs
red sea
example of active ocean basins
pacific ocean
Former failed rifts at high angles, which have been reactivated during convergent tectonics
Aulacogens
rifts formed at high angles to continental margins, without preorogenic history
Impactogens
Basins formed in intermontane settings following the cessation of local orogenic or taphrogenic activity
Successor Basin