The age of fossil rocks is determined using isotopes.
Bhimbetka, the famous Central Indian cave art repository near Bhopal dating from the Paleolithic and Mesolithic times, yields a fossil find dating back about 550 million years, the first time that the specific fossilized organism has been recorded in India. It dates from an era considered to be the forerunner of the explosion of life on earth during the Cambrian period and places India firmly on the map for studies of the Ediacaran era along with Australia and Russia. This is what makes the discovery a global milestone:
India’s first Dickinsonia
The recent discovery of the very first fossils of the organism Dickinsonia by a team of researchers led by Gregory J. Retallack, reported in the journal Gondwana Research that scientists studied the evolution of some of the earliest living species during a period of the earth’s history, known as the Ediacaran, is named after the Ediacara hills in South Australia.
This period in Earth’s history when Dickinsonia and several multicellular organisms existed was about 635 million years ago (Ma) and 541 Ma, with the living beings of the era called vendobionts. Earlier, Dickinsonia fossils were found in Russia and Australia, among others. They have expanded to a size of even one meter. The first Indian fossils were discovered in the roof of the auditorium cave in Bhimbetka Rock Shelters, preserved in the Maihar sandstone of the Bhander group, which is part of the Vindhyan subgroup rocks. The research was reported late last year.
Proximity to Australia
The age of fossil rocks is determined using isotopes. Zircon dates from the latest Maihar sandstone in Madhya Pradesh, setting its age at 548 Ma, while the lower Bhander group in the Sun and Chambal valleys yielded an isotope-derived age for limestones ranging from 978 Ma to 1073 Mom, and it takes place in the older Toniaan. period. The Ediacaran period was the forerunner of the Cambrian (about 541 Ma to 485.4 Ma) when the earth saw an explosion of life forms, of which modern animal life today is very much in shape.
The age profiles of the Dickinsonia fossils in the Maihar sandstone, which are determined using Zircon dating, make them approximately 555 Ma comparable to those from the Russian White Sea region. Further evidence comes from comparable fossils Dickinsonia tenuis and Dickinsonia costata in South Australia, which are estimated to be 550 Ma. Studies of the rock features in and around Bhimbetka show that they shared several properties with rocks in Australia, including an ancient elephant skin texture and also a trace fossil, Prasinema gracile, according to the research article.
The scientists found that fossils of Dickinsonia from India are identical to the Rawnsley quartzite in South Australia, which provides evidence of their age and the proximity of the two land masses in Gondwanaland in that era. However, the evidence does not support reconstructions adapted to the phenomenon of the polar walk [which involves motion of continents over geologic time and its impacts].
A characteristic feature of these creatures is the absence of hard protective parts such as skeletons and carapaces (exteriors), perhaps because there were no predators. It was also the time when evidence showed some of the earliest multicellular organisms, or metazoa. The evidence comes from life forms in water when soil did not have life.
Marine, animal or other?
From an evolutionary point of view, the finding of Dickinsonia and other Ediacaran species such as Ernietta and Arumberia, as discussed by the team led by Retallack, raises the question of whether they were shallow marine organisms or non-marine in nature. The researchers take note of the remote locations of the fossil finds separated by deep oceans and the grouping of Dickinsonia in Australia-India and the Baltic Sea, rather than in a single biogeographic province in an ancient geological time. .
Whether Dickinsonia was an animal or another organism is a matter of divergent interpretation, and one group of researchers led by Ilya Bobrovskiy argued that their finding of cholesterol in preservatives using lipid biomarkers indicated that they were indeed animals. Retallack and colleagues argue that such cholesterol is also found in red algae and most fungi. Knowledge of Ediacaran biogeography is evolving, and India is now a theater of studies on life on earth from a time when the subcontinent was elsewhere on earth.