EES130 Exam 1

Ancient Environments. Intro, Earth Materials, Life & the Fossil Record, Sedimentary Rocks & Stratigraphy, Time, Plate Tectonics. Chapters 1, 2, 3, 5, 6, 8, 9.

Historical Geology

A branch of geology studying the origin & history of earth & life forms over time. Concerns the tectonic changes on earth, geological time, stratigraphy, fossils, & evolution. Studied using rock types, strata, fossils, geochronology, and structures (faults/folds).

What is Scientific Theory & what are the 2 big theories relied on in this course?

Scientific Theory is a unifying idea incorporating previously accepted hypotheses (theories) that are well documented by data.

1. Plate Tectonic theory - States that the lithosphere is cracked & composed of pieces that float on a hot, deformable asthenosphere. This idea explains all of earth’s features, namely the ocean & continents.

2. Evolutionary theory - states that biological species give rise to other species through genetic change.

Earth System’s Approach

Understanding that all the physical, chemical, & biological processes operating on/with the earth are connected, & you need to understand all of them to understand how the earth works.

The atmosphere, biosphere, geosphere, hydrosphere are all linked, a change in one impacts the others.

Tectonics, action of water in its various forms (climate), & biological processes (life) are the 3 processes that have altered the earth over time.

7 Principles of Earth Science

Actualism, Superposition, Original Horizontality, Lateral Continuity, Cross-cutting Relationships, Included Fragments, Biotic Succession

Actualism

The physical & chemical process that we observe acting on the earth today operated the same in the geologic past. However, the rates of change & some processes have varied slightly over time.

Principle of Superposition

Within any succession of undeformed strata, the oldest layers are at the bottom & the youngest layers are at the top. (YOUNGER OVER OLDER)

Principle of Original Horizontality

Sedimentary layers were deposited nearly horizontal & parallel to the Earth’s surface, forming flat layers of strata.

Principle of Lateral Continuity

Rocks extend to great distances. At the time of deposition, strata extePnds continuously in all directions until they end by thinning at the edge of a basin, encounter a barrier, or change laterally into a different sediment type.

Principle of Cross-Cutting Relationships

A rock unit/fault that cuts another geologic unit is younger than the unit that was cut.

Principle of Included Fragments

Fragments of rock within a larger rock unit are older than the rock in which they are enclosed. The older fragments had to exist first to be incorporated into the new rock.

Principle of Biotic Succession

Fossils occur in strata in a definite, determinable order. This principle is used to interpret relative ages of strata.

Catastrophism

Incorrect Pre-1850s view that changes in the past to the earth & life were caused by violent catastrophes.

Uniformitarianism

Processes we observe today can be used to explain the geologic past. (too ridgid for geology, not always true)

Minerals

The building block for rocks.

A naturally occurring inorganic crystalline solid with a characteristic atomic structure & definite crystal composition. The compositional arrangement of elements is what gives minerals the properties of hardness, color, luster, etc.

Biomineralization

Some organisms secrete crystalline materials with the same composition of some minerals (such as calcite) to make shells, teeth, & bones which can eventually collect to form rocks. Although these are not minerals by definition, they can be considered as organic “minerals.”

Atoms

The building blocks of minerals that show the smallest individual particles with all the distinctive properties of an element.

Contain a nucleus with most of the mass of the atom, called the atomic mass, which is calculated by the combined mass of positive protons & neutral neutrons. Atoms have distinct outer shells containing negatively changed electrons.

Ionic Bonds

Transfer of an electron from one atom to another, creating (+) or (-) charged ions.

These bonds are weak & form soft minerals such as Halite.

Covalent Bonds

Sharing of electrons through atoms, so they all have full outer shells.

These bonds are strong, resulting in hard minerals such as Quartz.

Metallic Bond

Atoms share clouds of electrons where the outermost electrons drift between atoms.

These atoms are densely-packed & create heavy minerals such as Gold.

Isotopes

Atoms of a given element always have the same number of protons, but they can have a different number of neutrons. Isotopes are atoms of the same element that have different sums of protons & neutrons (their atomic mass)

Important because they behave differently in biogeochemical reactions & explain the earth’s chemical cycle. To become stable, radioactive isotopes break down over time & this process can be used to date rocks.

Main mineral groups

Silicates, Carbonates, Oxides, Sulfates, Sulfides, & Halides.

Silicates

Minerals containing the silicate tetrahedron surrounded by other atoms (quartz, hornblende).

Most common mineral among all rock types.

Carbonates

Minerals with calcium, magnesium, iron, etc attached to a carbonate ion.

Includes minerals from biomineralization (calcite).

Common in sedimentary (limestone) and metamorphic (marble) rocks.

Sulfates

Minerals with calcium or other ions attached to sulfate ion.

Occurs in some sedimentary rocks (gypsum) & tells of historical dry environments.

Halides

Minerals more commonly known as ‘salts,’ with positive ions (sodium) attached to negative ions (chlorine) to make a stable halide mineral (halite).

Occurs in sedimentary rocks (rock salts).

Oxides

Sulfides

Minerals that have metallic ions combined with oxygen (hematite).

Common minerals found in all rock types.

Sulfides

Minerals that have metallic ions combined with sulfur (pyrite).

Common minerals found in all rock types. In sedimentary rocks, it means they were deposited in an oxygen-free environment.

Rock Cycle

A conceptual model describing the origin, alteration, & destruction of rocks through the action of earth’s processes powered by the sun & earth’s internal heat.

Describes the processes by which rocks are formed, modified, & formed again.

Igneous Rocks

Rocks formed by the colling & crystallization of magma.

Classified by composition & texture.

Metamorphic Rocks

Rocks that have been transformed by heat, pressure, &/or chemically active fluids.

Commonly associated with burial or tectonic activity.

Classified based on texture & metamorphic grade.

Sedimentary Rocks

Usually layered, formed from sediments/minerals under aqueous conditions through lithification, compaction, and cementation.

Igneous Rock Classification

Texture:

1. Aphanitic - fine-grained, extrusive

2. Phaneritic - coarse-grained, intrusive

Composition:

1. Felsic - Light colored, high silica levels

2. Mafic - Dark colored, low silica levels

Igneous Rocks to Know

Granite - Phaneritic, Coarse-grained, felsic, intrusive

Gabbro - Phaneritic, Coarse-grained, mafic, intrusive

Basalt - Aphanitic, Fine-grained, mafic, extrusive

Rhyolite - Aphanitic, Fine-grained

Metamorphic Rock Classification

Texture:

1. Foliated - alignment of crystals perpendicular to the direction of pressure during metamorphism

2. Granular/Non-Foliated - have equidimensional crystals that cannot become aligned

Metamorphic Grade:

1. High-grade metamorphism - high temperatures & pressures, coarse grained rocks

2. Low-grade metamorphism - lower temperatures & pressures, fine grained rocks

Metamorphic Rocks to Know

Slate - foliated, fine grained, low grade metamorphism

Schist - foliated, coarse grained, high-grade metamorphism

Gneiss - foliated, gneissic banding, coarse grained, high-grade metamorphism

Marble - fine grained, forms from low-grade metamorphism of limestone

Quartzite - fine grained, forms from low-grade metamorphism of quartz sandstone

Regional Metamorphism

Occurs at areas of continental collisions, causing the progression of rocks from slate, phyllite, schist, & to gneiss.

Sedimentary Particle Types

Fragments - clasts of weathered & eroded rocks

Skeletal Debris - produced by organisms (biomineralization)

Crystals - precipitated from water

Lithification

process of converting loose sediment into sedimentary rock

Compaction

squeezing grains together under pressure

Cementation

gluing grains together through mineral precipitation

Linnaean Classification System

Based on similarities & differences among organisms, where the species is the fundamental unit of classification.

Species are categorized by ever-increasing size using a binomial nomenclature, naming organisms by their genus & species name.

3 Domains & 6 Kingdoms of Life

1. Archaea (prokaryotes)

   1. Archaebacteria

2. Bacteria (prokaryotes)

   1. Eubacteria

3. Eukarya (eukaryotes)

   1. Protista

   2. Fungiae

   3. Plantae

   4. Animalia

Kingdom Archaebacteria

Primitive bacteria who inhabit extreme environments, simple prokaryotes, solitary, chemosynthetic, oldest fossils on earth so they may have been first to evolve.

Kingdom Eubacteria

All prokaryotes not classified as archaebacteria, diverse cellular structure & metabolism, solitary or colonial, chemosynthetic or photosynthetic, dominate fossil record for the past 3 billion years.

Kingdom Protista

eukaryotic microorganisms (including algae, mold, & protozoans), usually unicellular.

Kingdom Fungiae

eukaryotes that develop from chitinous species & have chitinous cell walls (includes mushrooms, yeast, & lichen), mostly multicellular, acquire nutrients through living & dead tissue, reproduce asexually.

Kingdom Plantae

multi-celled eukaryotes that develop from an embryo & have separate sexes, includes vascular plants like flowers & trees, & nonvascular plants like moss, photosynthetic.

Kingdom Animalia

multi-celled eukaryotes that develops from a fertilized egg, separate sexes, obtain nutrients by digestion, made of specialized cells grouped into tissues & organs, distinguished based off vertebrates / invertebrates.

Bassic fossil records from each kingdom

Archaebacteria & Eubacteria - oldest body fossils (~3.4 ma) but biomarkers suggest they are even older, stromatolites are primarily evidence of life in the Proterozoic eon

Protists - their shells are well represented as fossils, date back to the Cambrian period, important for biostratigraphy

Fungi - poor fossil record

Plants - good fossil record of leaves, stems, bark, seeds, & spores; first appeared in the Silurian

Animals - most diverse fossil record, leave good body & trace fossils, extend back to late Proterozoic, Animals with hard parts are best preserved

Fossils

evidence (remains or traces) of once living organisms, usually only hard pieces are preserved, tells about sedimentary environment.

Body Fossils

direct or altered remains of ancient organisms.

Trace fossils

traces of once living organisms, but not of the organism itself (ex. Dinosaur tracks)

Biomarkers

organic compounds found in strata that are from specific types of organisms.

2 Types of Sedimentary Rocks

1. Siliciclastic - made of clasts of silicate minerals such as quartz & feldspar

2. Carbonate - made of carbonate minerals such as calcite & dolomite

Sedimentary Rock Classification

Grain Size, Sorting, & Rounding

Grain Size

Average size of sedimentary particles in a rock (fine = mud, medium = sand, coarse = gravel). Coarser grains are found closer to the mountains & finer grains are found downstream.

Sorting

The variations of grain size in a sediment sample. A well-sorted sample has grains of relatively the same size & are formed in areas with stable energy conditions (beach). A poorly-sorted sample contains grains of many different sizes & are formed in areas with varying energy conditions (river).

Rounding

The degree to which a sediment has been worn down. A rounded sediment has traveled far distances and has been significantly worn down. An angular sediment has not traveled very far, so it has not worn down.

Sedimentary Structures

an arrangement of grains in sedimentary rocks that result from depositional processes that create distinctive features

Primary vs. Secondary Sedimentary Structures

1. Primary - generated at the time/near the time of sediment deposition and tell of the depositional processes (ex. bedding, cross-bedding, ripples, graded-bedding)

2. Secondary - formed after the sediment is deposited, usually due to chemical processes (mudcracks, bioturbation, dinosaur tracks)

Bedding(strata)/Bedding Plane

the arrangement of sedimentary rock into discrete layers thicker than 1 cm

Cross-Bedding

groups of strata that lie at angles

Ripple-marks

small dune-like structures formed on the surface of rocks by moving water/wind

Graded Bedding

structure where grain size increases from bottom to top, created especially by alluvial/submarine fans

Mudcracks

form as fine-grained, clay-rich sediments dry out & shrink

Bioturbation

The displacement & mixing of particles through the burrowing of animals.

Differences between depositional environment and depositional facies.

Depositional environment - the geologic setting in which sediments were deposited. By examining the changes in the depositional environment, we can interpret the history of environmental change & climate.

Depositional facies - set of characteristics of a rock that represent a particular depositional environment, the characteristics used to interpret the environment. We can see & measure depositional facies.

Continental Sedimentary Environments

include rivers, lakes, deserts, glaciers, & more. Often contain coarse-grained, immature sediments. Can be reddish in color - from iron oxidation, contain coal - swamps, have large-scale cross bedding - deserts, & have the fossils of land animals & plants.

Transitional Sedimenatary Environments

include deltas, bays, beaches, & more. Contain evidence of wave activity & marine fossils due to better preservation of marine elements, but continental depositions are also evidenced.

Marine Sedimentary Environments

include shelf, shelf-slope, and ocean floor. Often contain fine-grained, mature sediments. Deep ocean basins often exhibit graded bedding from submarine fans. Limestone, reefs, and ooids are almost always associated with marine environments.

Transgression

a landward migration of a marine shoreline due to sea-level rise, flooding more land. Facies patterns include features that reflect shrinkage of land area as sea level rises, landward shift of facies over time, & a fining-upward trend as the water deepens.

Regression

a seaward migration of a marine shoreline due to sea-level falling, exposing more land. Facies patterns include features that reflect increase in land area as sea level falls, basinward shift of facies over time, & a coarsening-upwards trend as the water gets shallower.

Arid Climates

reddish-colored rocks due to oxidation of iron, evaporite minerals & ooids, mudcracks, giant cross beds from sand dunes

Humid Climates

coal, lake deposits, lots of shale, ancient soil types

Icehouse climates

global climates characterized by cooler temperatures (especially at the poles) & polar ice caps, low sea levels, vigorous ocean circulation, arid climates, ice ages, low rates of tectonic activity.

Large continental landmasses prevents the ocean from warming the earth, low rates of tectonic activity, less volcanic activity leads to low atmospheric CO2 levels & cooler temperatures.

Greenhouse climates

global climates characterized by warm temperatures (especially at the poles) & lack of polar ice caps, high sea level, sluggish ocean circulation, reefs are common, more humidity, ocean anoxia (lack of oxygen in deep waters), accumulation of organic matter, high rates of tectonic activity

Stratigraphy

the study of sedimentary rock layers (strata), which record geologic history