Question

Which one of the following chrons of Neogene and Quaternary geomagnetic polarity time scale is arranged in the order from oldest to youngest?

• A. Brunhes → Matuyama → Gauss → Gilbert
• B. Matuyama → Brunhes → Gauss → Gilbert
• C. Brunhes → Gauss → Gilbert → Matuyama
• D. Gilbert → Gauss → Matuyama → Brunhes

Hint:

The present day sits in the Brunhes chron, the youngest of the four, so the oldest to youngest order must end with Brunhes.

Answer 1

The Correct Option is D

Step 1: Recall the geomagnetic polarity time scale for the Neogene and Quaternary.
Earth's magnetic field reverses its polarity over geologic time, and these intervals of stable polarity are called chrons. The youngest part of the time scale, covering roughly the last 5 to 6 million years, is divided into four named chrons.

Step 2: List the chrons with their approximate ages.
Gilbert chron runs from about \(5.3\) to \(3.6\) million years ago, and is the oldest of the four.
Gauss chron follows, from about \(3.6\) to \(2.58\) million years ago.
Matuyama chron comes next, from about \(2.58\) to \(0.78\) million years ago.
Brunhes chron is the youngest, running from about \(0.78\) million years ago to the present day, and it is the chron we are living in now.

Step 3: Arrange them from oldest to youngest.
Oldest first gives us Gilbert, then Gauss, then Matuyama, then Brunhes as the youngest.

Step 4: Check each option against this order.

(A) Brunhes → Matuyama → Gauss → Gilbert: This is the correct set of four chrons but written youngest to oldest, the reverse of what is asked. Incorrect.

(B) Matuyama → Brunhes → Gauss → Gilbert: Places Matuyama before Brunhes, which is wrong since Matuyama is older, and it is not a consistent order at all. Incorrect.

(C) Brunhes → Gauss → Gilbert → Matuyama: Starts with the youngest chron and ends with one of the middle ones, so the sequence is scrambled. Incorrect.

(D) Gilbert → Gauss → Matuyama → Brunhes: This is exactly oldest to youngest as derived above. Correct.

Step 5: Final conclusion.
\[ \boxed{\text{Gilbert}\rightarrow\text{Gauss}\rightarrow\text{Matuyama}\rightarrow\text{Brunhes}} \]
Hence, the correct option is (D).