Strat Sed Final

How does burial rate effect carbonate diagenesis?

-A fast burial ensures that the hydrocarbons are trapped

What are salt domes? How are salt domes formed?

-A salt dome is a mound or column of salt that has intruded upwards into overlying sediments -Salt domes can form in a sedimentary basin where a thick layer of salt is overlain by younger sediments of significant thickness

What conditions result in the formation of Sabkhas?

-An initial rise in sea-level floods coastal areas and creates shallow water features. If the features silt up, or land rises, or the sea level falls, then the trapped water evaporates, leaving a flat salt pan, or sabkha

What factors, biological and geological, that has led to the Monterey formation to become an important petroleum resource?

-Anoxic pull apart basin -Cooling climate, high upwelling -TOC (total organic carbon) can be as high as 23% but averages around 2-5% -Tectonic fracking cracks the rock so that more oil can be trapped

What environments are large bryozoan deposits commonly found?

-Bryozoans may be found on all types of hard substrates: sand grains, rocks, shells, wood, and blades of kelps. Shallow waters mostly. Bryozoans are colonial organisms whose skeletons look superficially like corals, but are structurally different. The animals themselves are very different from corals. Ecologically, bryozoans are filter feeders, using their lophophores to generate currents that pull food particles to the mouth

What is the Carbonate Compensation Depth (CCD)? How does it affect the accumulation of sediments on the deep seafloor? How deep is it on average in the Pacific? What controls the depth of the CCD?

-CCD is the depth in the oceans below which the rate of supply of calcium carbonate lags behind the rate of solvation, such that no calcite is preserved -Calcareous plankton and sediment particles can be found in the water column above the CCD. If the sea bed is above the CCD, bottom sediments can consist of calcareous sediments called calcareous ooze, which is essentially a type of limestone or chalk. If the exposed sea bed is below the CCD tiny shells of CaCO3 will dissolve before reaching this level, preventing deposition of carbonate sediment

What is the origin of Biogenic Chert?

-Clastic Starved Basin, silica rich -Pelagic setting (deep sea) -Shelf edge (upwelling)

How can turbidites be identified?

-Clastic, low-density turbidites are characterized by graded bedding, current ripple marks, climbing ripple laminations, alternating sequences with pelagic sediments, absence of shallow water features.

What sedimentary structures are found in turbidites?

-Climbing ripples -Laminated silts and sands -Sole marks -Rip up clasts -Slumping- soft

*What are some of the major differences between siliciclastic and carbonate diagenesis?

-Different sediments involved -Siliciclastic offers better reservoirs

What are whitings?

-Drifting clouds of water, milky because of suspended carbonate -Physical precipitation of calcium carbonate muds

How do fecal pellets affect the deposition sediments in the deep sea?

-It was discovered that plankton shells are delivered to seafloor by "biopackaging" via fecal pellets. In other words, various microorganisms that eat other planketon excrete their shells in fecal pellets. These "biopackaged" fecal pellets are large enough and dense enough to sink to the seafloor, where they become part of the sediment

What is the carbonate material known as micrite? What is it made of today? What is its origin? Under what conditions does it accumulate as sediments?

-Made of lime muds -Microorganisms breaking down reefs -It is deposited in generally quiet water

What mechanisms cause basins to subsidence?

-Sediment loading -Isostasy -Crustal cooling

What are facies and what is Walther's Law?

-The characteristics of a rock or sediment unit that reflect its environment of deposition and allow it to be distinguished from rock or sediment deposited in an adjacent environment. -Sedimentary environments that started out side-by-side will end up overlapping one another over time due to transgression and regression

What is the importance of salt domes for oil exploration?

-The development of salt domes can deform rock units into traps that hold oil and natural gas -Salt domes serve as oil and natural gas reservoirs

What is the oil window and at what temp does oil form?

-The temp range in which oil forms -Below the minimum temp. oil remains trapped in the form of kerogen, and above the maximum temp. the oil is converted to natural gas through the process of thermal cracking ~90 C, Carbon changed into a liquid

Why are turbidites important targets for oil exploration?

-The turbidite sequences are highly sought by petroleum geologists because they can constitute good reservoirs for hydrocarbons

What factors influence the stability of carbonate materials?

-There is an increase in mineral stability with decreasing grain size -CCD

Why are turbidites important?

-Turbidites provide a mechanism for assigning a tectonic and depositional setting to ancient sedimentary sequence. --Turbidity flows often move sediments with organic material from shallow marine environments to deep ocean. The bottom-following sediment-transport processes brought potential reservoir sands into close juxtaposition with basin-floor anoxic muds, ideal "source beds," thus combining two petroleum prerequisites and in a setting requiring a minimum amount of "primary migration" of the petroleum from source to reservoir;

*During evaporation of saline water, what is the sequence of mineral deposition?

1) Calcite- calcium carbonate 2) Gypsum- calcium sulfate 3) Rock salt- halite, NaCl 4) Bitter salts- K and Mg salts

What are 3 types of reef formation?

1) Fringing 2) Barrier 3) Atoll

Describe the modern environments where evaporites form

1) Lakes -Playa: complete evaporation -Saline: Carbonate rich lake 2) Intertidal Sabkha 3) Saline giants

What environmental conditions produce organic rich sediments?

1) Little or no oxygen 2) Organic rich matter 3) Rapid burial

In what ways can carbonate rocks be influenced by diagenesis and alteration?

1) Opal A turning to Opal-CT 2) Kerogen turning to oil/gas

What are the basic stratigraphic principles or laws?

1) Original horizontality 2) Lateral Continuity 3) Law of Inclusions 4) Superposition 5) Law of Cross Cutting Relationship

What sedimentary facies are associated with each basin?

1) Rift basin -fluvial, lacustrine, alluvial fans -evapories form -volcanic rocks can be present 2) Forearc basin -turbidites 3) Foreland basin -alluvial fans

*What basins are produced in each tectonic setting? (6)

1) Rift basins-divergent, east african rift, high heat flow, elongated valleys bound by normal faults 2) Passive margin basin-continental margin, divergent, subsidence increases in offshore direction, mainly due to cooling 3) Forearc basin & Backarc basin-convergent, deep sea trenches, oceanic crust subduction 4) Retroarc basin-convergent, sediment loading 5) Foreland basin- on land, convergent, himalayas 6) Strike-slip Basin- transform boundary

What are 3 facies, (lithology, comp, and age) found in the Monterey Formation?

1) Siliceous facies: 14-6 mya, major cooling, radiolarians and diatoms, banded chert, upper member 2) Phosphatic facies: 15-14 mya, CaCO3 to chert on top, mudstone, phosphate rocks, shale, middle member 3) Calcareous facies: 16-15 mya, carbonate rich, chalks, coccoliths/forams, warmer period, lower layer

What are the environment conditions that are required to build large reefs?

1) Sunlight -Corals depend on zooxanthellae that grow inside of them for oxygen and other things, and since these algae needs sunlight to survive, corals also need sunlight to survive 2) Clear water -Corals need clear water that lets sunlight through 3) Warm water temp 4) Clean water 5) Saltwater

What is a reef?

A biologically mediated wave resistant, build up of calcium carbonate with associated sediments that form in shallow, nutrient poor, tropical waters

How is karst formed?

A landscape formed from the dissolution of soluble rocks such as limestone, dolomite, and gypsum. It is characterized by underground drainage systems with sinkholes and caves. As the soluble rocks are exposed to the surface, rain (slightly acidic) dissolves away the surface

Flysch

A sedimentary deposit consisting of thin beds of shale or marl alernating with coarser strata such as sandstone or conglomerate

What are turbidites?

A turbidite is the geologic deposit of a turbidity current, which is a type of sediment gravity flow responsible for distributing vast amounts of clastic sediment into the deep ocean

Make sure that you know the 4 elements of petroleum geology. Esp understand what makes the best source beds and reservoirs

A. Source Bed -organic rich rocks (Shale) -Temp and Pressure conditions to make oil and gas form (depends on depth) B. Conduits bed -Oil flows up from source to reservoir C. Reservoir -Porous and permeable rocks- sandstone and carbonates D. Seal -Shale or salt

What are rudist clams?

About 100 million years ago, during the heydey of the dinosaurs, reefs were built by mollusks called rudist clams. Like modern clams, rudists were bivalves with 2 shells joined at a hinge.

What is the importance of heat and burial in the formation of petroleum?

As the organicc matter is buried (insufficient oxygen for complete decomp of organic matter) and the depth increases, the heat from earth allows the matter to result in petroleum. If the temp is not consistently hot enough, only gas is formed. If the temp is too hot, the original biomass is destroyed and no gas or petroleum is formed

How do atolls age?

As the volcanic island is eroded away, the atoll grows from the use of sediment, but once the island is completely eroded

How do hermatypic corals get their nutrients?

As the zooxanthellae photosynthesize they use the carbon dioxide respired by the polyp animal, water and sunlight to produce high energy nutrients and oxygen which they then share with their coral host. The energy can provide the full needs of the zooxanthella as well as up to 95% of energy needed by the coral

What facies are found in the cross-section of reef?

Basin--lower slope--upper slope--shelf margin--lagoon--shore-zone complex

What basins are most likely to be a source for oil?

Basins located in the ocean- rift basins and trenches formed from converging boundaries (forearc). it would alllow a more anoxic environment

What is the importance of bioerosion on coral reef? What animals commonly bore into corals?

Bioerosion plays a key role in producing carbonate sands/muds that fill in between coral and aid in growth Parrotfish, sea urchins, snails, clams, sponges

How are reefs constructed? What factors affect coral reef growth?

Brick-hard coral. Mortar-Red algae. As a reef grows it is simultaneously slowly eroding. When the corals die and the eroded materials begins to accumulate, the red corraline algae cements the material together and the new coral can grow on this new carbonate surface

Compare the 2 evaporation patterns associated with saline giants?

Bullseye-restricted basin Teardrop basin- can produce more evaporites, constantly refreshed

What role does calcareous algae play in the formation modern reefs?

Calcareous algae takes up space where other algae may grow. Many coral larvae need a surface of calcareous algae to settle and grow and this cannot happen on a surface covered by green, red, or brown algae

What marine cements form soon after burial?

Calcite cement

What sediments are found in association with reefs?

Carbonate sediments

Joggins Fossil Cliffs

Cliffs featuring carboniferous Period fossils exposed by tidal erosion. Constant erosion from the Fundy tides, rising and falling up to 13m at Joggins twice daily, creates possibilities for exposing new fossils

How did the discovery of plate tectonics and glaciation history alter Darwins theory of atoll formation?

Darwin thought that the inner volcano along with erosion eventually submerge the atoll complete making a sea mound. Glaciation can account for sea level rise/fall that exposes karst and creating the flat top we associate with sea mounds

What is the depositional history of the radiolarian cherts of the Marin Headlands?

Deep sea shelf complemented by upwelling. Silica levels are controlled by changes in the oceanographic process called upwelling, which brings nutrient-rich water to the ocean surface and allows the radiolaria to thrive

What are the differences and similarities between radiolarians and diatoms?

Diatoms are considered plants and found more frequently in high latitude areas while radiolarians are considered animals and are found in low latitude areas. Both have a siliceous composition

Why did the Miocene cooling cause the formation of widespread diatom deposits around the Pacific Rim?

Diatoms are normally accustomed to cooler waters at high latitudes. When this cooling event took place, it made it possible for the diatoms to move farther towards the equator than before, resulting in a substantial amount of siliceous diatom cherts deposited around the pacific rim towards the end of the Miocene

Know the Bouma sequence

E: Massive, ungraded mudstone, sometimes with trace fossils (usually structureless) D: Parallel-laminated siltstone, from tail of turbidite C: Ripple-laminated fine-grained sandstone (climbing ripples may be present) B: Parallel laminations in coarse to medium sand A: Massive to normally graded, fine to coarse grained sandstone, often with pebbles or rip up clasts of shale near the base. Scoured base with tool marks, flutes

In general, turbidite deposits are composed of couplets of arenites and mudstone. What does each couplet represent?

Each couplet is the result of a single turbide

Hemipelagic deposits

Fine grained sediments in the ocean water that has been directly derived from a nearby continent

What evaporitic minerals are common in marine and nonmarine environments?

In general, marine deposits are thicker. The most common are calcite, gypsum, halite (rock salt). The nonmarine evaporites usually bitter salts (potassium and magnesium salts)

Are corals an animal, vegetable, or mineral?

Its an animal that lives like a plant and makes a mineral-based skeleton

Red calcareous algae

Like the mortar between bricks, holds dead reef together so that more can grow on top. Light dependent

Messinian salinity crisis

Mediterranean Sea went into a cycle of partly or nearly complete desiccation throughout the latter part of the Messinian age of the Miocene epoch

In what ways can lime mud form?

Microorganisms

What is the relationship between carbonate deposition and water depth?

Most modern, and probably most ancient, carbonates are predominantly shallow water deposits. This is because the organisms that produce carbonate are either photosynthetic or require the presence of photosynthetic organisms. Since photosynthesis requires light from the sun, and such light cannot penetrate to great depths in the oceans, the organisms thrive only at shallow depths. Furthermore, carbonate deposition in general, only occurs in environments where there is a lack of siliciclastic input into the water. Siliciclastic input increases the turbidity of the water and prevents light from penetrating, and silicate minerals have a hardness much greater than carbonate minerals, and would tend to mechanically abrade the carbonates. Most carbonate deposition also requires relatively warm waters which also enhance the abundance of carbonate secreting organisms and decrease the solubility of calcium carbonate in seawater. Nevertheless, carbonate rocks form in the deep ocean basins and in colder environments if other conditions are right.

How does oil originate

Oil is formed from the remains of small animals and plants that died and fell to the bottom of the sea. Their remains were covered by mud. As the sediment was buried by more sediment, it started to change into rock as the temp and pressure increased.

How and when was Darwin's theory of atoll formation verified?

On Bikini atoll, there was a nuclear testing being done. The researchers did core tests to see what would happen to the island after it occurred. They discovered in the core that it began as limestones but eventually they "hit" basalt rocks, aka volcanos

What is the relationship between the "oil window" and the diagenesis of silica?

Opal-A turns to Opal-CT at around the same temperature that kerogen turns to oil

What does it mean, "Carbonate sediments are born, not made"?

Over 95% of carbonate sediments are biological in origin and found in the marine environment

Molasse

Sandstones, shales, and conglomerates that form as shallow marine deposits in front of rising mountain chains -good oil reservoir

Zooxanthellae

Single-celled photosynthetic algae that works within the coral

What plants and animals formed reefs over the last 500 million years?

Skeletal coral and algae

What is the importance that chert fractures easily?

Tectonic fracking cracks the rock so that more oil can be trapped

What is the Bakken Basin?

The Bakken Shale is a rock formation from the Late Devonian, early Mississsippian age that is stimated to hold as much as 24 billion barrels of recoverable oil. The Bakken formation consists of 3 layers: upper black shale layer, middle silty-dolomite, and lower black shale layer. The shale layers are petroleum source rocks as well as seals for an oil reservoirs in the dolomite layer

How are atolls formed?

The formation of an atoll begins when an underwater volcano erupts, creating a volcanic mountain beneath the surface. When this mountain builds up and approaches the surface, its rough edges provide an ideal surface for coral to develop. Over time, a circular coral reef builds around the mountain. However, this kind of volcanic rock tends to be soft and porous. The ocean gradually erodes it away, leaving behind a circular reef and a large lagoon

What is fracking?

The process of injecting liquid at high pressure into subterranean rocks, boreholes, etc. to force open existing fissures and extracts oil or gas

Relative to sea level, where are caves on limestone islands formed?

They are formed at sea level- Wave action

What is Vuggy Porosity?

This is secondary porosity generated by dissolution of large features (such as macrofossils) in carbonate rocks, leaving large holes, vugs, or even caves

What are the facies associated with sabkha?

Top -Salt crust -Anhydrite -Algal mat -Gypsum -Dolomite Bottom

What is the paradox of the reef?

Tropical waters contain few nutrients yet a coral reef can fluorish like an "oasis in the desert". This has given rise to the ecosystem conundrum, sometimes called "Darwins paradox". How can such high production flourish in such nutrient poor conditions? Filter feeders and warm surface waters floating above the cooler deeper waters help keep nutrients out/get rid of nutrients

What is the relationship between earthquakes and turbidites?

Turbidites form from the flow of debris in offshore environments. The sediments are usually built up along a shelf and with an event like an earthquake, the buildup of sediments will unravel and become a turbidite.

What role does biology have in carbonate deposition?

Well over 95% of the carbonate sediments are biological in origin and found in the marine environments. Forams, corals, and algaes produce carbonate structures as well

What types of allochems and orthochems combine to produce carbonate rocks?

allochems: ooids Orthochems: cement

What are oolites and how are they formed?

oolite is a sedimentary rock made up of ooids that are cemented together. Most oolites are limestones--ooids are made of calcium carbonate. Oolites form today in warm, supersaturated, shallow, highly aggitated marine water. -The mechanism of formation is to begin with a seed of some sort, perhaps a shell fragment. The strong currents wash this seed around on the bottom where it accumulates a layer of chemically precipitated calcite from the supersaturated water.