Cyclostratigraphy

Question 1

Cyclic Sedimentation

Answer 1

Succession of related depositional processes and conditions that are repeated in the same order through time

Question 2

Cyclical Uniformitarianism

Answer 2

Geological history and processes are episodic and cyclical

Question 3

Cyclicty may be?

Answer 3

Diurnal (tidal couplets), Annual (Glacial lake varves), and longer term (transgressive-regressive cycles)

Question 4

What are the 2 types of cyclicity?

Answer 4

Autocyclic: cyclic succession controlled by processes within the basin itself

Allocyclic: Cyclic succesions controlled by factors outside of the basin

Question 5

What two factors contribute to the development of cyclic sedimentation?

Answer 5

Terrestrial and Extraterrestrial controls

Question 6

List and describe the Extraterrestrial cycles:

Answer 6

Tidal: Earth moon system, gravitational and centripital forces

Annual: Seasonal changes of the year

Milankovitch: Lunar, eccentricity (Change of orbit from near circular to strongly elliptical), obliquity (Change in tilt of earths axis) and precession (Change in direction of the axis)

Question 7

List and describe the Terrestrial cycles:

Answer 7

Wilson Cycle (cycle driven by plate tectonics, involves stages of rifting, drifting, and converging) lasts 400 Ma

Eustatic Changes (changes in the volume of water in the ocean largely controlled by the volume of terrestrial ice)

Question 8

How many orders of Cyclicity are there? and how does there time range?

Answer 8

5. First order cycles are the longest. Fifth orders are the shortest.

Question 9

First order cycles:

Answer 9

(200-400Ma) Accretion and subsequent splitting apart of super continents

Question 10

Second order cycles:

Answer 10

(10-100 Ma) Sloss’ sequences

Question 11

Third order:

Answer 11

(0.5 - 10 Ma) Not well documented. Believed to be from glacio and tecteno eustatic controls

Question 12

4th and 5th order cycles:

Answer 12

4th: (500ka to 200ka)
5th: (10ka to 200ka)

Both cycles are well documented and widely attributed to orbitally driven mechanisms (milankovitch cycles)

Question 13

What is Eustasy?

Answer 13

The absolute change of sea level and therfore a global phenomenom

Question 14

What is sedimentation controlled by?

Answer 14

Available accomodation space which is either created or destroyed by eustatic and tectonic changes

Question 15

Transgression? Regression?

Answer 15

T: Caused by increase in relative sea level and is defined by landward shifting of shore line

R: Caused by relative decrease in sea-level and is defined by a seaward shifting of the shore line

Question 16

Relative sea level?

Answer 16

Measured between the sea-surface and a local moving datum

Question 17

Accomodation space?

Answer 17

Space available for accumulation of sediments

Question 18

Progradation? Retrogradation? Aggradation?

Answer 18

P: Occurs when rate of sedimentation is greater than creation of Accomodation space (S/A > 1)

R: When S/A < 1

A: When S/A = 1

Question 19

Allostratigraphy?

Answer 19

Refers to stratigraphic subdivisions into mappable rock bodies defined and identified on the basis of their bounding discontinuities and their correlative conformable surfaces