Singhbhum Craton and Age of Emergence of Continents

A craton is defined as a stable but significantly old part of the lithosphere section of the continent. It primarily consists of two layers of earth, the topmost: crust and mantle. They have survived several rounds of rifting and merging of continents and are primarily found inside the tectonic plates. An exception is when rifting events have led to the separation of cratons and the creation of passive margins at edges. The composition primarily includes crystalline basement rock covered with sediments from Singhbhum that are significantly younger. It also has a thick crust and lithospheric roots that are deep, extending into the mantle of earth.

About Singhbum Craton

The Singhbhum craton is among the first stable continents bounded by the Sukhinda trust fault in the South, Mahamdi graben, Narmada-Son lineament in the west, the Bay of Bengal in the east, and Indo-Gangetic Plain in the west north and situated in eastern India itself. There are three main parts of this craton the 2.2 to 1.0 billion-year-old Singhbhum-Dhalbhum mobile in the north, the old Archean Singhbhum nucleus in the South, and the belt of gneisses and granites north and west of the mobile belt of Chotanagpur-Satpura.

The craton primarily comprises old rocks, including the 3.2 billion-year-old metamorphic group. Evidence indicates that the rocks in the Singhbhum nucleus can be as old as 3.8 billion. The magmatic activity that occurred ended in the nucleus of Singhbum about 2.7 billion years ago. The thrust belts composed in the Singhbum craton are the Singhbum thrust between the mobile belt and Singhbum nucleus, in the northern part of the Dalma thrust, and along the southern margin of craton the Sukinda thrust. The craton centre is cleaved by the major rift valley, which comprises Gondwana’s sediments in the Damodar Valley.

Strides about Singhbhum craton in 2021

The scientists found some evidence of sediments from the Singhbhum craton in November of 2021, and this supposedly appeared above sea level about 3 billion years ago. This indicated that the rocks found in the region were formed way before tectonic plates even existed.  

The tectonic plates are the reason for controlling the elevation of Earth’s surface currently. The formation of Alps and Himalayas were formed when the collision between the two tectonic plates was done. The growth of the Himalayan range is still imminent. Scientists have found a layer of sandstone presumed to be 3.1-billion-year-old on top of the Singhbhum craton. It is believed that the formation of the Singhbhum craton was done by a consistent accumulation of lava from the volcano. The rock elements collected and extracted from the craton were similar to those found in South Africa and Western Australia.

The emergence of Land Mass from the Ocean

The unique feature of the continent is primarily its thick, tender crusts which allow them to stay afloat on the mantle of the Earth. Around 3.2 billion years ago, the crust became even thicker and enough to emerge from oceans leading to the formation of one of the early landmasses. Ancient continents such as the Singhbhum Craton are primarily made up of granite and pre-existing rock at the base of crust melting. After a brief overview and analysis of granitoid extracted from the craton, sodium to potassium-based geochemistry transitioned from a brief timeframe from 3.53 to 3.1 billion years ago, which indicated a maturation of the crust progressively. 

This further became depleted increasingly in rare heavy elements and yttrium, which indicates the formation of granites at immense pressures, more than almost tripling from a period ranging from  3.5–3.25 billion years ago. The rock formation at the continental crust bottom indicated a drastic surge in Singhbhum Craton thickness ranging from 20 to 28 miles over the same time. The crust of the Singhbum Craton around 3 billion years ago has increased about 31 miles. 50 kilometres in thickness, making it ideal enough to emerge above sea level. 

Dating of Zircon

The researchers depicted the sandstone’s age by microscopic grains studying zircon, a mineral. Zircon contains trace amounts of uranium, leading to slow decay into the lead over a geological time frame. 

The lead to uranium measurement ratio helps determine the zircon crystal formation time frame. The uranium-lead dating indicated that the sediments of Singhbhum that were ancient in the Singhbhum Craton were composed in it 3 billion years ago, which made it one of the oldest known deposits of beach in the world.

Conclusion

The Singhbhum carton, one of the first stable continents of eastern India, is surrounded by Dhanjori, Dalma, etc. These belts are iron-rich. The Singhbhum carton is one of the major Indian shield Archean cratons. The other four cratons are the Dharwar craton, Bastar craton, Bundelkhand craton, and Aravalli craton. The Singhbhum craton comprises Archean rocks located in Jharkhand and Odisha’s northern parts. The Southern side of Bastor craton surrounds the craton, the Northern side of Chotanagpur plateau, the Southeastern side of Eastern ghats and the eastern side of Alluvium.