Question

Which one of the following primary structures can be used for paleocurrent measurement?

• A. Oscillation ripple
• B. Hummocky cross-strata
• C. Flute cast
• D. Load and flame structures

Hint:

Flute casts always indicate flow direction — the pointed end faces upstream and the rounded end faces downstream.

Answer 1

The Correct Option is C

Step 1: Understanding paleocurrent measurement.
Paleocurrent measurement refers to determining the direction of sediment transport in the geological past using sedimentary structures preserved in rocks.

Step 2: Requirement of an ideal indicator.
A good paleocurrent indicator must clearly show flow direction, distinguishing between upstream and downstream.

Step 3: Analysis of Oscillation ripple.
Oscillation ripples are formed due to wave motion and show symmetrical patterns. Since the movement is bidirectional, they do not indicate a specific flow direction.

Step 4: Analysis of Hummocky cross-strata.
Hummocky cross-stratification forms under storm conditions with complex, multidirectional flow. Hence, it does not provide a reliable paleocurrent direction.

Step 5: Analysis of Flute cast.
Flute casts are erosional structures formed by unidirectional current flow. They have a tapered upstream end and a wider downstream end, clearly indicating flow direction.

Step 6: Analysis of Load and flame structures.
Load and flame structures are deformation features caused by density differences in sediments. They do not indicate current direction.

Step 7: Final conclusion.
Among the given options, only flute casts serve as reliable indicators of paleocurrent direction.
\[ \boxed{\text{Flute cast}} \]