Geo Final general info

Upper sandstone and mudstone unit

Shallow ocean sand and mud most likely to deposit there

Dark gray shale

Deep ocean dark colored mud is most likely to deposit there because of lower oxygen levels

Yellowish-tan sandstone

Beach color and size of sediments is typical of the beach

Lower basal conglomerate

Mountain streams are normally conglomerate deposits because they have large rounded grains

what is the oldest environment represented by the rock sequence?

Lower basal conglomerate

Does the change of environment from the base of the section (the basal conglomerate) up to the thick gray shale indicate an advance (transgression) or retreat (regression) of the sea? Explain the reasons for your answer

transgression as the clast size goes from big to small from the conglomerate to the shale

Does the change from the thick gray shale to the overlying sandstone indicate a transgression or a regression? Explain your answer.

regression as the clast size goes from small to big from the shale to the sandstone

Which of the following phrases summarizes the history of the entire sequence

a transgression following by a regression

Upper Shale

wetland and swamp that is muddy and plant-rich

Carbon Beds

wetland and swamp that is muddy and plant-rich

Tan Mtn. Sandstone

delta that is sandy

Muddy Shale

lagoon that is shallow and muddy

Lower Sandstone

beach

Lower Limestone

reef

Salt

narrow sea with very saline water and with a limited connection with the ocean

Structure 1

oil in fold

Structure 2

coal in fold

Structure 3

salt intrusion no fossil fuels

Structure 4

gas in a fault

Structure 5

oil in fold

fold

compressed rock bending due to pressure

fault

pressure causing rocks to break & slip ll to fracture

stress

pressures that cause rock deformation can be compressional or tensional

strain

deformation that results from stress

elastic strain

spring-like; deformation was temporary and recoverable

plastic strain

beyond elastic; permanent deformation & nonrecoverable

brittle strain

fracture (what rocks tend to do)

Anticline

Upward warp of rx strata w/ old at center

Syncline

downward warp of rx strata w/young at center

Mesozoic means

middle life

The geologic time scale was first constructed through the use of

fossils and the principles of stratigraphy as determined by Steno (relative aging).

A quartz sandstone most likely formed at the

beach

An undeformed sedimentary layer is ______ than the layer below and ______

younger ... older

Which of the following is used by geologists to determine the relative ages in a rock sequence?

superposition, fossils, cross-cutting relations

If pieces of one rock are included in another rock, the rock with the pieces in it is ____________.

younger

The geologic time scale is important because

it provided the time necessary for plate tectonics and evolution, it allows the correlation of rocks of similar age, revealed the changes of life underwent through time

What is the name for an erosion surface that separates two sets of sedimentary layers with non-parallel bedding planes (hint: tilted rock)?

angular unconformity

normal fault

Tensional; Hanging wall down

reverse fault

compressional, hanging wall up

strike-slip

shear only horizontal motion

floodplain

flat area on either side of channel within valley. Area where river meanders.

-point bar (deposition) vs. cutbank (erosion); oxbow lakes; natural levees

drainage basin

area of land that a river & tributaries drain

clastic sedimentary rocks

formed by weathering & erosion that is transported, deposited, and buried. Undergo lithification (compaction & cementation) that results in sed. rx. Non-local source

chemical sedimentary rocks

form from constituents that are in the area, i.e., shells of organisms

discharge

total volume of water flowing past a point in a given time period. D= v * A

D= discharge; A=area (ave width * ave height)

-D and v increase downstream with increasing water from tributaries

unconformity

a broken sequence between 2 rx layers or a gap in geologic time

disconformity

if bewtween 2 sedimentary rock layers

nonconformity

if between a sedimentary rock and underlying igneous Or metamorphic

angular unconformity

if 2 rock layers (regardless of rock type) are not parallel

formation

a series of rock layers that have the same physical properties & possibly the same fossils; gives a period of geologic time

radiometric dating

the use of naturally occurring radioactive elements to determine age

importance of geological time

It breaks down important events that happened since the formation of the Earth; Summarizes great chunks of Earth's history in terms that we can actually discuss and understand

age of earth

4.55 x 10^9 years or 4.543 billion years old

relative v. absolute time

Relative: "I am older than you, but younger than him"; Sequence of Events; Relative Dating Principles; Science of determining the relative order of past events w/o necessarily determining their absolute age

Absolute: "I am 20 years old."; Numerical Age; Radioactive Decay of Elements

relative age relations

laws of superposition, cross-cutting relations, inclusions

law of superposition

The oldest rock layers are furthest toward the bottom & the youngest rock layers are closest to the top; Relates to relative age relations for example one layer is 70 million yrs old and another is 100 million years old then the layer in between them would have a relative age somewhere between 70 and 100 million years old.

cross-cutting relations

Rock formations that cut across other rocks must be younger than the rocks that they cut across; This is especially useful for establishing the relative ages of faults and igneous intrusions in sedimentary rocks

inclusions

Foreign bodies of rock or mineral enclosed within another rock; Because the sedimentary rock had to have formed around the objects for it to be encased within the layers, geologists can establish relative dates between the inclusions and the surrounding rock; Inclusions are always older than the sedimentary rock within which they are found.

precambrian (before 544 ma)

Earliest fossils primitive bacteria 3.5 byr; Soft shelled organisms in ocean; First life at mid-ocean ridges; 1st fossil Isua Fm Greenland; Stromatolites (cyanobacteria by 3.2 BA)

Paleozoic (544- 251 ma)

Shelled organisms (1st in Cambrian Seas); Fossils can show plate positions in past (Pangea); Plants & animals on land by 400 MA; Insects smaller today

Mesozoic (251-65 ma)

Age of Reptiles; Not just Dinos & Not always fighting; Common Mesozoic fossils (more familiar than those of Paleozoic)

Cenozoic (65 ma- present)

Age of Mammals; Human ancestors (3ma); Paleogene Titanoboa (King of the Snakes) largest marine creature living on Earth; Many mammals; Humans could be cause for extinction of about 80% of large herbivores species

transgression

Clay to Sandstone to Mud; Event where sea level rises relative to the land & the shoreline moves toward higher ground, resulting in flooding; Caused by land sinking or ocean basins filling w/ water (or decreasing in capacity)

regression

Sandstone to Clay; Areas of submerged seafloor are exposed above sea level; Continental sediments are being deposited farther out to sea than they once were; Maximum regression occurs where the coarsest sediments reach the farthest seaward

associated with unconformities

role of fossils

Matching of rocks of similar ages in different regions is known as correlation; This is typically done using fossils; You can match rocks w/ other rocks; Fossils show same age; Certain fossils only at certain times; Fossils can reveal that continents were once together by some fossils in Europe are the same or almost the same as those in America