Select the incorrect sequence of Geological periods/Era using the codes given below :
A. Triassic → Jurassic → Cretaceous
B. Paleozoic → Mesozoic → Cenozoic
C. Devonian → Silurian → Carboniferous

Question

Select the incorrect sequence of Geological periods/Era using the codes given below : 
A. Triassic → Jurassic → Cretaceous 
B. Paleozoic → Mesozoic → Cenozoic 
C. Devonian → Silurian → Carboniferous

Accepted Answer

The correct option is 3: Only C

This question tests your knowledge of the established chronological order of the Geological Time Scale (GTS), which is the absolute framework used by scientists to date Earth's history. You are asked to identify the statement that presents an **incorrect** sequence. Statement C is incorrect because it reverses the order of two key periods within the Paleozoic Era. The correct sequence of these three periods, from oldest to youngest, is **Silurian $\rightarrow$ Devonian $\rightarrow$ Carboniferous**. The Silurian Period (approximately 443.8 to 419.2 million years ago) came first, characterized by the colonization of land by early plants. This was followed by the Devonian Period (approximately 419.2 to 358.9 million years ago), often called the "Age of Fishes," and finally the Carboniferous Period (approximately 358.9 to 298.9 million years ago), known for vast coal swamps. Since statement C lists the Devonian *before* the Silurian (Devonian $\rightarrow$ Silurian $\rightarrow$ Carboniferous), it presents a faulty chronological order, making 'Only C' the correct selection.

The incorrect option is 1: A and B

This option claims that both A and B are incorrect sequences, which is factually inaccurate. Statement A correctly presents the sequence of the three periods of the Mesozoic Era: Triassic $\rightarrow$ Jurassic $\rightarrow$ Cretaceous. Similarly, statement B correctly lists the three most recent major Eras in chronological order: Paleozoic $\rightarrow$ Mesozoic $\rightarrow$ Cenozoic. Since both sequences A and B are correctly ordered according to the GTS, the claim that *both* are incorrect sequences cannot be true.

The incorrect option is 2: Only B

This option is incorrect because statement B (Paleozoic $ightarrow$ Mesozoic $ightarrow$ Cenozoic) is a perfectly correct chronological sequence. These three blocks of time are the Eras that constitute the Phanerozoic Eon, moving from the 'ancient life' of the Paleozoic, through the 'middle life' (Age of Reptiles) of the Mesozoic, and into the 'recent life' (Age of Mammals) of the Cenozoic. To select this option would mean wrongly identifying a fundamental and correct part of the GTS as incorrect.

The incorrect option is 4: A and C

This option proposes that the incorrect sequences are the combination of A and C. While statement C is indeed an incorrect sequence, statement A (Triassic $\rightarrow$ Jurassic $\rightarrow$ Cretaceous) is a correct sequence of the Mesozoic periods. Therefore, to say that both A *and* C are the incorrect sequences misrepresents the fact that sequence A is accurate. Since the question asks to select the code representing the *incorrect* sequence, and only C is incorrect, selecting any option that includes a correct sequence like A would be logically flawed.