Gondwana Marine Intercalations Age Explained

The question asks about the geological age of specific rock layers known as marine intercalations found in the basal part of the Gondwana succession. We need to determine which geological period these layers belong to.

Understanding the Gondwana Succession

The term 'Gondwana succession' refers to a significant sequence of sedimentary rock layers found across large parts of the Southern Hemisphere, including India, Australia, Africa, South America, and Antarctica. These rocks were deposited during the time when the supercontinent Gondwana existed. In India, the Gondwana sequence is primarily known for its terrestrial deposits, laid down by rivers, lakes, and glaciers, and it contains important coal deposits and dinosaur fossils.

The Significance of Marine Intercalations

Within the largely terrestrial Gondwana sequence, the presence of marine intercalations is particularly noteworthy. These are distinct layers of rock that show clear evidence of having been formed in a marine (ocean or sea) environment. Such evidence can include marine fossils (like specific types of shells or plankton), minerals formed in seawater, or sedimentary structures typical of marine settings. These layers act as important markers, indicating periods when marine waters advanced over the continent.

Determining the Age of Basal Marine Layers

The 'basal part' refers to the lowest layers of the Gondwana rock sequence. Identifying the age of these basal marine intercalations is crucial for understanding the early history of Gondwana deposition in the region.

Based on extensive geological studies and the fossil content found within these specific marine layers in the lower sections of the Gondwana succession:

• The evidence strongly indicates an Early Permian age.
• These marine bands are often found above glacial deposits (like the Talchir Formation) and are associated with a rise in sea level early in the Permian period.
• The characteristic fossils found in these layers help geologists correlate them with other geological formations worldwide that are also dated to the Early Permian (approximately 299 to 273 million years ago).

These marine intercalations are vital for reconstructing the paleogeography and understanding the environmental conditions during the formation of the Gondwana sequence.

Conclusion

In summary, the marine intercalations located in the basal portion of the Gondwana succession are recognized as belonging to the Early Permian age.