EXAM 1. REVIEW

Stratigraphy. Define stratigraphy:

Who developed the following principles and define each (use sketches where possible):

Define these other important stratigraphic concepts:

1. conformable sequence

2. unconformable sequence

3. gradational contact

4. erosional contact

5. stratigraphic correlation

6. angular unconformity

SEDIMENTARY ENVIRONMENTS

The character of sedimentary rocks provides clues to the geologic history of a region. The character of a rock is determined by the environmental conditions under which it formed. Environmental Conditions = tectonic setting and environment of deposition (review each if required). Environmental conditions influence many aspects of sedimentary deposits such as texture and primary sedimentary structures.

Define the following related concepts:

1. Texture

2. Planar cross bedding

3. Trough cross bedding

EXAMPLES OF SEDIMENTARY ROCKS RELATED TO DEPOSITIONAL ENVIRONMENT

For each of the following describe the character of the rock and where each typically forms:

1. Graywacke

2. Arkose

3. Quartz sandstone

4. Shale

5. Carbonates

PALEOGEOGRAPHY & FACIES

Rock units. Define the following:

1. Formation

2. Member

3. Group

The major inadequacy in this approach is that no regard is made to TIME BOUNDARIES and, consequently, formations may be DIACHRONOUS. The solution is:

Time-rock units (Chronostratigraphic units): This refers to sedimentary rocks deposited during the same time period. Unlike rock units, lithology can vary greatly within time-rock units, and the upper and lower boundaries consist of time-planes. The fundamental time-rock unit is the SYSTEM, which corresponds to a PERIOD of geologic time. This approach enables PALEOGEOGRAPHIC MAPS to be constructed (i.e. maps showing the geography of a region at a given instant in the geologic past).

Facies: An important question is.."how do you interpret the environment of deposition?" Answer = the facies concept. A facies is a description of the attributes of a sedimentary rock which are specifically related to to its environment of deposition and is intended to aid in the interpretation of that environment. Good examples of environmental change are global, or EUSTATIC, sea-level changes that have resulted in inland seas, referred to as EPEIRIC SEAS, covering as much as 2/3 of the North American continent. Much of the sedimentary rock record of the Paleozoic and Mesozoic Eras were deposited during these periods of marine inundation. Many rock sequences record transgressions (carbonates over shale over sandstone) and regressions (sandstone over shale over carbonates).

FOSSILS

Fossilization. Define the following:

1. Permineralization

2. Replacement

3. Carbonization

4. Mold

5. Cast

6.Trace Fossils

Classifying Organisms:

The modern system of classification is referred to as TAXONOMY. The smallest taxonomic unit = SPECIES - "group of organisms basically alike in their structural and functional characteristics; can interbreed and produce fertile offspring" (proves genetically related). The rest of the system is hierarchical levels of kinship (kingdom-phylum-class-order-family-genus-species). Organism usually identified by genus and species eg. Homo sapiens (Man); Canis lupus (Wolf).

THE GEOLOGIC TIME SCALE

The standard geologic time scale was not developed in an organized and systematic manner. Instead, the scale took shape over centuries as a number of geologists discovered and named the various intervals, on the basis of time-rock units identified by superposition, fossils and correlation (absolute ages from radiometric dating have only recently been added). Often the units were named after the local area or the type of rocks present.

Divisions:

Eons – Archean, Proterozoic (Precambrian) + Phanerozoic (evident life)

Eras - Based on major changes in fossils. Paleozoic (544-245 mybp); Mesozoic (245-66 mybp); Cenozoic (66mybp-present day).

Periods: Again, based on fossil changes. Named after local features i.e.

1. Cambrian; after cambria (latin for Wales) 542-488 mybp.

2. Ordovician; after ordovices, early celtic tribe, 488-443 mybp.

3. Silurian; after silures, English/Welsh tribe, 443-416 mybp.

4. Devonian; after Devonshire, 416-359 mybp.

5. Mississippian; from the Mississippi River basin, 359-318 mybp.

6. Pennsylvanian; rock outcrops in Pennsylvania, 318-299 mybp.

   (last two only used in N. America, elsewhere = Carboniferous,

    based on coal beds in northern England).

7. Permian; from Perm, a province of Russia, 299-251 mybp.

8. Triassic; rocks in Germany, 3 divisions, 251-200 mybp.

9. Jurassic; the Jura mountains in Switzerland, 200-145 mybp.

10. Cretaceous; from 'creta' for chalk, 145-65 mybp.

11. Paleogene (65 – 23 mybp); beginning of “Age of Mammals”.

12. Neogene (23-2.6 mybp); “Neo” = newer part of  Cenozoic, pre-ice ages.

13. Quaternary; suggested by a French geologist, 1.8-0 mybp. Time of ice ages.

(Absolute ages were not available when these divisions were first made).

Based on radioactive decay i.e. the nucleus of certain elements (PARENT ELEMENT) spontaneously emit atomic particles and in so doing change to a different element (DAUGHTER ELEMENT). When dealing with a large number of atoms, studies have shown how long it will take FOR HALF OF THEM TO DECAY - this is the HALF LIFE. The ratio of PARENT ELEMENT to DAUGHTER ELEMENT thus follows a predictable pattern. Therefore, radiometric dating methods are based on finding the radioactive element in a mineral from which none of the daughter element has escaped and calculating the ratio between them to find the age of the mineral.

(Multiple Choice)

William "strata" smith developed the principle of:
a. biological succession b. original lateral continuity
c. cross-cutting relationships d. original horizontality
e. uniformitarianism

In which of the following are the eras ordered from oldest to yougest:
a. mesozoic, paleozoic, cenozoic b. cenozoic, mesozoic, paleozoic 
c. paleozoic, cenozoic, mesozoic d. paleozoic, mesozoic, cenozoic 
e. cenozoic, paleozoic, mesozoic

(Short Answer)

With the aid of diagrams, define "superposition".
With the aid of diagrams, define "angular unconformity".
Define "half-life".

(Longer Answer)

1. Describe the characteristics and typical origin of TWO of the following rock types: graywacke; quartz sandstone; arkose.

2. Explain radiometric dating. 

3. Describe the seven principles of stratigraphy (including their authors; use sketches where possible).

4. Explain the difference between conformable and unconformable sequences, including the concept of gradational and erosional contacts.

5. Sketch the geologic time scale, including eons, eras and periods.

6. Describe the 6 modes of fossilization covered in class.

7. Illustrate how paleogeographic maps are constructed based on characteristics of sedimentary rocks (include sketches of maps).

The first exam will be 1 hour and 15 minutes and consist of 10 multiple choice questions, 4 short answer questions and 1 longer answer question out of a choice of 2 (the 2 questions will be selected from the list of 7 above). Lab material NOT covered in a lecture (e.g. material covered only in a virtual museum visit) will NOT be on the exam (this applies to all four exams).