Climate reconstruction

Question 1

What is the difference between a diagnostic and non-diagnostic material?

Answer 1

Diagnostic material can be used to reconstruct the environment more accurately than non-diagnostic materials

Question 2

Diagnostic material

Answer 2

• Till/boulder clay (tillite) - Glacial
• Coral reef (Limestone) - Tropical sea
• Scree - Frosty hillside

Question 3

Nondiagnostic material

Answer 3

• Mud (mudstone) - River, Ocean
• Sand (sandstone) - River, Ocean, Desert

Question 4

How can Clonglomerate be sorted?

Answer 4

• Size
• Shape
• Material
• Sortedness

Question 5

Glacial Valve deposists

Answer 5

• Regular alternations in lake sediments desposited in annual cycle
• Occurs only in freshwater or brackish water
• Thick-light layers=summer
• Thin-dark layers =winter

Question 6

Sand

Answer 6

• All has ripples and dunes
• At low velocity, rippled beds form
• Fluvial crossbedding is smaller and unidirectional
• Sand can be sorted on texture, roundedness, compositional maturity, fossils and rock colour

Question 7

Reconstruction challenges

Answer 7

• Sedimentary rocks may be destroyed leading to an incomplete record
• Seafloor is contantly being subducted and new floor is created. Hard to access
• Sediment on a continental shelf may flow down as turbite due to an earthquake. Creating a deep sea fan
• Fossil record hard to interpret

Question 8

What is Diagensis?

Answer 8

Refers to the physical and chemical changes by which sediment are converted into rock by heat, pressure and chemical reactions

Question 9

Siliclastic sediment

Answer 9

• Caused by rock weathering, which contain Silicate materials
• The more intense the weathering, the less likely it is to find less resistant materials

Question 10

Chemical/Biological sediments

Answer 10

• C sediments form at their place of deposition (Salt water evaporation leaving minerals)
• B sediments are the result of mineral precpitation by organisms. Often formed from Aragonite and Calcite

Question 11

Continental Sedimentary basins

Answer 11

• Lake environments
• Alluvial environments - very common with organic sediment
• Desert environments, little organic sediment
• Glacial environments- meltwater streams and little organic sediment
• Shoreline environment, where rivers enter a lake/ocean (delta), tidal flats and beaches

Question 12

Marine sedimentary basins

Answer 12

• Organic reefs will become limestone
• Deep sea sediments most likely to be siliclastic