Directional Structures

1
Directional Structures

• Show current direction
• Examples include such things as cross-beds,
  ripples, imbrications, flute casts
• Show current trend
• Examples include groove casts, parting lineation

2
Cross-bedding

• Current Direction

• Current from left to right

3
Ripple Marks

• Asymmetric Ripples show current direction

4
Flute Casts

• Found on the bottom of beds
• scoop like structure

5
Parting Lineation

• Yields current trend, not direction

6
Groove Cast

• Yields trend of direction

7
Topping Indicators

• Structures used to determine tops in sedimentary
  rocks include the following
• Sole marks, Graded beds, Cross-beds, Symmetrical
  ripples, Mudcracks

8
Ripple Marks

• Symmetric Ripples show tops

9
Graded Bed

• Usually found in greywacke, caused by deposition
  of coherent mixtures of gravel, sand, mud and
  water

10
Mudcrack

• Mudcracks occur in areas that are flooded and
  then dry out.

11
Sole Marks

• Sole marks occur on the bottom of beds. Include
  flute and groove casts

12
Cross-bedding

• Is truncated on the upper side of the bed