Lithostratigraphy

Question 1

Why is it important to a have a formal system for definig, classifying, and naming geologic units?

Answer 1

• Furnishes a systematic study of the physical properties
• Allows decipher the vertical and lateral relationships of strata
• Contributes to the interpretation of depositional environments
• Contributes to other aspects of earths history

Question 2

What is the purpose of stratigraphic classification?

Answer 2

Promote understanding of the geometry and successions of rock bodies

Question 3

What are the 2 sets of procedures of stratigraphic classification:

Answer 3

1) North American Stratigraphic Code

2) International Stratigraphic guide

Question 4

There are 2 categories of stratigraphic units:

Answer 4

1) Material Categories based on content or physical limits
- Lithostratigraphic, lithodemic, magnetopolarity, biostratigraphic, chronostratigraphic pedo, and allostratigraphic
2) Categories expressed or related to geologic age
- Various chronostratigraphic techniques

Question 5

Lithostratigraphy

Answer 5

Is the study and description of rocks based on their physical characteristics. Rock type, colour, mineralogy, grain size, etc..

A lithostratigraphic unit generally conforms to the law of superposition and is commonly stratified and tabular in form

It can be recognizes and defined on the basis of observable rock characteristics

Question 6

Name and describe the Hierarchy of lithostratigraphic units

Answer 6

Supergroup - A formal assemblage of related or superposed groups or groups and formations

Group - Consists of assemblages of formations, but groups need not be composed entirely of named formations

Formation - a body of rock, identified by lithic characteristics and stratigraphic position, that is prevailingly but not necessarily tabular and is mappable at the earth’s surface and traceable in the subsurface

Member - the formal lithostratigraphic unit next in rank below a formation and always part of some formation. A formation need not be entirely divided into members

Lens - a geographically restricted member that terminates on all sides within a formation

Tongue - A wedge shaped member that extends beyond the main boundary of a formation or that wedges or pinches out within another formation

Bed - distinctive subdivisions of a member, the smallest lithostratigraphic unit

Flow - the smallest lithostratigraphic unit of volcanic rock

Question 7

Name and describe the 2 types of lithostratigraphic contacts

Answer 7

Lateral - units can have a pinchout, intertounging, or lateral graditional contacts with neighbouring units

Vertical - can be conformable(abrupt or gradational) or unconformable (angular, dis, non, para)

Question 8

Very briefly describe cyclic successions and the 2 different types

Answer 8

Repetitions of strata that reflect a succession of related depositional processes

1. Autocyclic - processes within the basin itself (ex. turbidites)
2. All0cyclic - externall processes (ex climate change)

Question 9

What is lithocorrelation?

Answer 9

Lithological matching of stratigraphic succesions but generally more complex and requires application of more than one technique