Correct Option
The correct option is Jurassic.
Explanation
The question pertains to the geological evidences supporting the Continental Drift Theory and the subsequent Plate Tectonics Theory. Specifically, it addresses the timing of the breakup of the supercontinent Gondwanaland, which led to the separation of South America and Africa and the formation of the South Atlantic Ocean.
Detailed Analysis
- Geological Context: South America and Africa were once united as part of the Gondwanaland landmass. The coastline fit (Jig-Saw Fit) between the bulge of Brazil and the Gulf of Guinea is one of the most prominent physical evidences of this union.
- Timing of Separation: The rifting that separated these two continents and opened the South Atlantic Ocean began during the Mesozoic Era.
- Marine Deposits: As the continental blocks drifted apart, ocean water entered the rift valley, leading to the deposition of marine sediments. The earliest marine deposits found along the opposing coastlines of Brazil (South America) and West Africa date back to the Jurassic period.
- Significance: The presence of these Jurassic-aged marine sediments confirms that the ocean basin had begun to form by this time, marking the initial phase of the drift before the widening continued into the Cretaceous period.
Key Takeaway: The discovery of Jurassic-age marine deposits along the matching coastlines of South America and Africa serves as critical paleontological and geological evidence dating the initial opening of the South Atlantic Ocean.