Sedimentology, Stratigraphy, Sedimentary Basins

Task 4-1 Keyword Review Exercise: Sedimentology, Stratigraphy, Sedimentary Basins

Keyword Search

Weathering: The down of rocks into smaller rocks *Mechanical: The down, through abrasion, freeze thaw, erosion, and other processes, of rocks into smaller rocks. No new is old material is broken down into smaller Ex: Wind sand distances and abrading the surfaces of boulders in a breaking off pieces of boulder and new sand Freezing and thawing of a boulder expands fractures in the rock and eventually breaks it apart. *Chemical: Rocks react to substances in the environment and are broken down into smaller things such as Fe oxidizing to become rust when coming in to contact with 02. Chemical weathering produces new substances through chemical reactions. Ex: Through HydrolYSis feldspar crystals are hydrated creating silica hydrates that expand when engorged with water weakening the structure of the rock they are a and further breaking it down.

Clastic/Detrital: a notation for rocks composed of fractures or fragments of rocks. Clastic Rocks like conglomerates or breccias are of smaller rocks around the environments they were formed in. Ex: Through mass wasting, breccia can be formed out of poorly sorted angular to sub-angular debris from landslides given enough pressure and time.

Clay: A stiff sticky very fine-grained Can range in color depending on composition and location from which it was derived. It's basically hydrated aluminum-silica particles.

Describes the sizes and of throughout a rock. Poor would allude to a large discrepancy between the sizes of the within one rock.

Biochemical Sedimentary: rocks that are Also Known as these rocks are up this could be plants or shells of marine organisms. Ex: Plant and animal material accumulates for thousands of years in a swamp (reduction environment) and builds up until there is over 600 ft of accumulation total and millions of years later anthracite is found deep beneath the swamp.

Chemical rocks that are when minerals that were dissolved in water preCipitate out through evaporation of the solution or depOSition. Ex: An old dried riverbed is littered with talc and gypsum

Conglomerate vs. Breccia: Conglomerate: A rock composed of round sand and silt. Typically found in ancient riverbeds. Breccia: A rock of silts and Typically at the toes of mass wasting events. Shale: Ancient lake bed rock. Composed of fine silts and clays and formed in thin strata at the bottom of lakes.

Arkose: Sandstone composed of quartz, feldspar, and some micas, but has at least 25% feldspar in its composition. It forms in deserts with arkosic sand.

Gray Wacke: darker grey sandstone with quartz and feldspar. It's basically underwater sandstone breccia. it forms mainly at the bottom of the ocean where either underwater avalanches or turbidity currents spin up gravel and sand thoroughly mixing them before re-depositing them.

Limestone: A chemical or biochemical sedimentary rock that can form as a precipitate of groundwater (Stalagmites and stalactites), or from the shells of marine organisms (coquina). It is mainly composed of CaC03 (calcium carbonate).

Dolostone: Composed dolomite which is equal parts Magnesium and Calcium, dolostone is basically limestone, but a little bit harder with more magnesium. It forms in the same way limestone does and is thought to be altered post-deposition through magnesium rich groundwater combining with limestone.

Coal: A combustible Dark brown-black rock made of plant matter that is millions of years old. It can only form in reduction environments such as swamps or bayous which prevent bacteria from breaking down plant materials.

Chert: Composed of microcrystalline quartz (Si03), it can have fossils and fractures like glass. it's thought to form from deposits from the shells of some marine organisms, but it can also come from volcanic ash deposits.

Sedimentary Structures: Structures formed during sediment deposition. These could be ripple marks, graded bedding, or flow structures that indicate the original deposition of sediments within a specific strata. Ex: A strata is examined and shows evidence of being deposited from such an angle that it contradicts how it should be under normal conditions, this suggest faulting or some other process has occurred to alter the position of the strata

Lithofacies-biofacies: * Lithofacies: A rock record of a sedimentary environment, differing from adjacent sediment that's deposited, including the organic and physical characteristics such as weather and what flora and fauna live there. Ex: Finding some coal in the middle of the Namib Desert that was somehow uplifted to the surface. *Biofacies: a group of flora or fauna in a stratum that don't appear to belong in that stratum. Ex: Finding some bipedal dinosaurs among squid fossils.

Bed vs. lamina: Bed: A bed is basically a layer of deposited rocks, minerals, and/or sediments that is on a plane defined by differing strata. Beds are the smallest lithostratigraphic unit used to describe deposits. A bed can be several meters to a single centimeter and are differing in their layers through chemical composition, particle size, and rock or mineral type. lamina: Lamina is tiny layers within sedimentary rocks that are one centimeter or smaller. These layers can differ through a number of factors such as grain size, organic content, mineral content, ect. A single sedimentary rock may have both beds and lamina. *Not-so-artistic rendering:

Paleocurrent indicators: a sedimentary structure or marking that helps to determine the direction of flowing water in geological history. One might find directional ridges at the bottom of an ancient riverbed indicating the direction of flow. Ex: Clasts from a conglomerate indicating the direction of flow based off of the angle in which they were deposited.

Fluvial: of river origin

Lacustrine: of lake origin

Carbonate Ramp: Sometimes referred to as carbonate platforms, carbonate ramps are built up of carbonate sediments in large mounds.

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Stratigraphy: The of the layers or strata of earth's rock record. There are two branches, lithostratigraphy and biostratigraphy. Lithostratigraphy studys the rock record and biostratigraphy studies within strata. Stratigraphy yields information that shows the environment of deposition and allows to propose how the sediment may have been deposited and to on what a particular environment is like. Ex: study of a stratum shows that it is all sandstone and likely the site an ancient desert.

Law of Horizontality: States that is originally horizontally through the influence of gravity. This can help geologist to understand and faulting strata that can occur post-deposition.

Law of Uniformitarianism: The same natural laws that apply today applied in the past and apply always wherever you go in the universe.

Law of superposition: The oldest stratum is at the bottom strata and the youngest strata will be the closest to

Law of Cross-Cutting relations: An igneous intrusion (such as a dike) is always younger than the rocks in the strata that it cuts across.

Law of Lateral Continuity: Layers of sediment initially extended laterally in all directions. This means that if a river cuts through several stratum, that the stratum at point x on one side of the river should match the stratum at point x on the other side of the river (exception when sediments are too far from source to appear on the other side of river). The law does not state that sediment extends in all directions indefinitely rather, that as one moves away from the source of what initially deposited the sediment, the strata should thinner. Ex: The strata on one side of the Deschutes River match the other side. of a species found in a stratum on one side of the river are also found on other side of river.

Law Floral and Faunal Succession: found in one stratum will match fossils found in the same stratum. A group of marine fossils in a r stratum should not include bipedal dinosaurs.

Walthers Law: Strata are the product of a series of different depositional environments occurring in succession. The strata will be "laterally adjacent" meaning that lay horizontally on top of one

Ex: A strata of a shoreline will show a record of sea level based off of the types of sedimentary rocks formed that are recorded in the strata and how or small individual stratum are within the strata.

to the geologic time of 542-251 million years ago Mesozoic: Referring to the geologic time frame of 252.2-66 million years ago

Cenozoic: Referring to the geologic time frame of 65.5million years ago to present time.

Lithostratigraphy: Is the study of strata utilizing geochronology, petrology and comparative geology. It focuses on the changing environments of deposition as time goes on and how the strata represent these changes.

Chronostratigraphy: The study of strata focusing speCifically on the age of individual stratum. Chronostratgraphers work to form a complete geologic record of time. Sediments are deposited obeying the Law of Superposition allowing Chronostratigraphers to determine the relative age of rock structures. Ex: A Chronostratigrapher assists a paleontologist in determining the age of a stratum where a fossil was found.

Biostratigraphy: The study of the flora and fauna that belong to a particular stratum and therefore, a speCific environment and point in time. Biostratigraphers can also determine the age of a stratum utilizing the theory of evolution to show that a fossil found in a stratum should precede or follow another fossil in a different stratum. Ex: A biostratigrapher assist a chronostratigrapher who's studying a faulted strata in determine what stratum should follow each other.

Index Fossils: What biostratigraphers use to determine the relative age of a stratum. Certain fossils belong to certain time periods in earth's history. Ex : A trilobite is found in a stratum helping geologist to determine the age of the stratum

Unconformity: When a very old stratum is in contact with a much younger stratum. It represents a hole in the geologic timeframe of strata. Ex : an ancient layer of sediment with fossils from the Triassic period is directly below a stratum with fossils from the Paleogene.

Interfingering Strata: Where stratum change laterally in intersecting wedges

Cross section of San Andres/Grayburg depositional sequences

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Lacuna: also a gap in the geologic time record that could be related to erosion.

Paraconformity: A specific type of unconformity where there is no way of knowing what caused the unconformity. They are bizarre as they literally suggest that a large period oftime never occured

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Transgression: When sea levels rise and the shoreline moves up higher relative to the continents

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Trans gressive F a cies Sequ e nce { Rift Basin: A sedimentary basin created by a rift boundary

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Strike-Slip Basin: A sedimentary basin created by a strike-slip boundary ---

Normal Fault: A fracture in the earth's crust that is the result of the movement of earth's tectonic plates.

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N ormal Fault Regression: Where sea level lowers and shorelines moves down relative to the continents

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Onflap-Offlap: Where younger rock stratum spread laterally cut into progressively older rock stratum over time and vise-versa for offlap transgression ["

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Eustacy: A global change in sea level that might reflect in the overall water contained in the ocean. Some geologist speculate that water may come out of the magma in our mantel and that was how our oceans formed. Reverse Fault: A fault in reverse

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Isostatic Subsidence: A glacier weighs down the earth's crust causing it to subside or stretch downward.

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Forearc Basin: The area between a volcanic chain and an oceanic trench that is the result of a convergent plate boundary. The uplift created by the volcanic arc creates a basin between the shoreline and trench slope Trench Slope Plate subduction zone Volcanic Break (TSB) Trench arc Arc- Trench Gap Trench Slope Axis Volcanic Front Basin Forearc Basin y Trench Slope ' Y' Forearc Basin Fill

Arc Massif Forearc ?-----Substratum Foreland Basin: The same as a forearc basic but is instead the result of a continent-continent collision.

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Backarc Basin: is a basin behind a volcanic arc and is the result of convection currents in the mantle from a subduction zone causing causing plates to diverge at a point and lower creating a basin

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Aulacogen: A failed arm of a three-way rift in a plate.

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