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Flashcards in Geological Time in Strata Deck (20)
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1

Define stratigraphy

The study of the layers of sedimentary rock at a macroscopic scale

2

Define the Principle of Original Horizontality

Strata tend to be deposited more or less horizontally

3

Define the Principle of Superposition

In a vertical succession of sedimentary or volcanic rocks, a higher rock unit is younger than a lower one. “Up” is younger.

4

Define the Principle of Lateral Continuity

Upon initial deposition, strata tend extend in all directions until they pinch out or until they grade laterally into a different kind of sediment.

5

Define the Principle of Cross-cutting

A structure that cross-cuts another structure is the younger of the two.

6

Define the Principle of Inclusion

A structure included in another is the older of the two.

7

Principle of faunal succession

Fossils in stratigraphic successions change upward (i.e., with time) in a predictable way. For example, strata containing trilobites always underlie strata containing Tyrannosaurus fossils, which in turn always underlie strata with woolly mammoth fossils.

8

Define index fossils

fossils used to define geological periods

9

Define uniformitarianism

The physical laws of Nature have remained the same since the dawn of time. The Earth may change, but the laws that govern this change do not.

10

Define lithostratigraphy

Process by which strata are correlated given their physical attributes

11

What is lithology

Classification of rock types

12

Lithostratigraphic unit:

A rock unit that can be correlated (mapped) over a certain region and is defined by its observable physical traits (i.e., defined by its lithology, aka rock type).

13

Biostratigraphic unit

A rock unit that can be correlated (mapped) over a certain region and is defined by its fossil content.

14

Define conformable contacts

no significant break (hiatus) in sedimentation has occurred, and the geological record is complete.

15

Define unconformable contacts

a significant break (hiatus) in sedimentation has occurred due to non-deposition or erosion.

16

Three methods of dating the earth

Annual layers on trees, estimation of geological rates, and geometric dating

17

Why does stratigraphy typically require correlation?

a)Because the goal of stratigraphy is to identify large-scale patterns in sedimentary rocks. b)Because outcrops tend to be small and isolated. c)Because proving an event is local or global in extent can help understand how the Earth system operates.

18

List the ages of the rocks from oldest to youngest

C B A D E

19

Define a varve

A sedimentary unit deposited in a year.

20