Stratigraphy Flashcards
the study of temporal and spatial relationships between bodies of sedimentary rocks.
Stratigraphy
What is the goal of Stratigraphic analysis?
to establish the temporal sequence of
sedimentary rocks in the area under investigation
Enumerate the Principles of Stratigraphy
- Law of Super Position
- Law of Original Horizontality
- Lateral Continuity
- Cross-Cutting Relationships
- Inclusion
- Unconformity
- Law of Faunal Succession
the oldest layer is at the base and that the layers are progressively younger with ascending order in the sequence.
Law of Super Position
all rock layers are originally laid down (deposited) horizontally and can later be deformed.
Law of Original Horizontality
all rock layers are laterally continuous and may be broken up or displaced by later events
Lateral Continuity
younger rocks cut across older rocks.
Cross-Cutting Relationships
any rock fragments that are included in rock must be older than the rock in which they are included.
Inclusion
represents a long period during which deposition ceased, erosion removed previously formed rocks, and then deposition resumed. In each case, uplift and erosion are followed by subsidence and renewed sedimentation.
Unconformity
states that a species appears, exists for a time, and then goes extinct. Time periods are often recognized by the type of fossils you see in them.
Law of Faunal Succession
determining a sequence of events occurred in the history of earth using the evidence of organic evolution in the sedimentary rocks accumulated through geologic time.
Dating
it is when rocks and events are put in correct order of sequence relative to one another.
Relative Dating
the age of rocks units are determined precisely in years using the rate of decay of naturally occurring radioactive elements.
Absolute Dating
usually a product of interpretation of other stratigraphic analysis of the basin. Its ultimate aim is to arrange the sequence of deposition and the time of deposition of all rocks within a geological region.
Chronostratigraphy
uses fossils to establish relative ages of rock and correlative successions of sedimentary rocks within and between depositional basins.
Biostratigraphy
is an interval of geologic
strata characterized by certain fossil taxa.
Biozone
fossils that are used in petroleum industry
Microfossils,
Nanofossils, and Palynomorphs
relies on the correlation of rocks of the same characteristics. Most maligned stratigraphic method and also the oldest of them all.
Lithostratigraphy
the study of seismic data for the purpose of extracting stratigraphic information.
Seismic/Tectonic Stratigraphy
Generated by the accumulation of sediments in a basin wherein major changes brought about by the tectonics in the area affects the gross structure of sediment package
Seismic/Tectonic Stratigraphy
enumerate the Different Margins Identified by Tectonic Stratigraphy
- Rift Basins
- Passive Margins
- Foreland Basins
- Wrench Systems
packages of sediment deposited before, during, and after the active rift phase can often be clearly identified on regional seismic lines
Rift Basins
a development of a successful rift. It can develop over a substantial period of time, thus, the megasequence can be enormously thick
Passive Margins
forms contemporaneously with the flexuring of the lithosphere caused by thrust loading. The shape is commonly elongate parallel to the thrust belt.
Foreland Basins
Megasequences developed during strike-slip are commonly of small aerial extent. The sequences may be symmetric, as in transtensional systems, or asymmetric, as in transpressional systems.
Wrench Systems
involves the geochemical classification and correlation of sedimentary strata by using
major and trace element geochemistry, which is highly helpful when applied to sequence with poor biostratigraphic control.
Chemostratigraphy
a geophysical correlation technique used to date sedimentary and volcanic sequences. The method works by collecting oriented samples at measured intervals throughout the section and analyzing the magnetic polarity of each sample
Magnetostratigraphy
a branch of sedimentary stratigraphy that deals with the order or sequence in which depositionally related stratal successions (time-rock) units were laid down in the available space or accommodation. It is developed from seismic stratigraphy.
Sequence Stratigraphy
a geologic event in which sea level rises relative to the land and the shoreline moves toward higher ground, resulting in flooding. It can be caused by either the land sinking or the ocean basin filling with water.
Transgression
a geological process occurring when areas of submerged seafloor are exposed above the sea level.
Regression
a sedimentary rock that contains sufficient organic matter such that when it is buried and heated, it will produce petroleum
Source Rock
chemical composition of organic matter is diverse because the organisms from which it is derived are complex
Organic Matter
What is the primary requirement for the preservation of organic matter in source rocks?
Anoxic conditions
What is the primary source of lipids that contribute to hydrocarbon generation?
Chlorophyll
are fatty organic compounds, insoluble in water, and found in most abundance in algae, pollen, and spores.
Lipids
a class of hydrocarbon polymers consisting of aliphatic and aromatic structures.
Lignins
The two basic requirements for the generation and preservation of organic matter in sediments
- high productivity of organic matter
- oxygen deficiency of the water column and the sea level (anoxic depositional environment)
Enumerate Depositional Environment with High OM Productivity
- Continental Margins
- Lagoons and Restricted Seas
- Deltas in Warm Margins
- Lakes
Two Types of Organic Matter
Bitumen
Kerogen
composed of compounds that are soluble
in organic solvents.
Bitumen
most abundant organic component on
earth
Kerogen
Four (4) Types of Kerogen
- Liptinite
- Exinite
- Vitrinite
- Inertinite
has a high hydrogen to carbon ratio but a low oxygen to carbon ratio; It is rich in lipids; fluoresces under UV light.
Liptinite
has intermediate hydrogen to carbon and oxygen to carbon ratios; The source is mainly membranous plant debris (spores, pollen, and cuticle), and phytoplankton and bacterial microorganisms in marine sediments; fluoresces under UV light; high proportion of sulfur and is termed Type II-S kerogen.
Exinite
has a low ratio of hydrogen and high ratio of oxygen relative to carbon; the primary source is higher plant debris found in coals and/or coaly sediments; does not fluoresce under UV light
Vitrinite
Which depositional environment is associated with high organic matter productivity?
Continental margins
is the non-fluorescing product of any of kerogens; It is high in carbon and very low in hydrogen, and is often termed “dead-carbon,” having no effective potential to yield oil and gas.
Inertinite
Type 2 kerogen is derived from which sources?
Membranous plant debris and marine microorganisms
Which type of kerogen is primarily derived from higher plant debris?
Vitrinite (Type 3)
What does the principle of faunal succession imply?
Fossil organisms succeed one another in a definite and recognizable
order
The lipid group contains a special group of compounds called ______________, which are found in chlorophyll and include ___________ and ____________.
isoprenoids, pristane, phytane
