BIO- AND CHEMOSTRATIGRAPHY OF THE KROL A FORMATION IN LESSER HIMALAYA, INDIA: EARLY EDIACARAN EUKARYOTE EVOLUTION AND ENVIRONMENTAL CHANGE

The Doushantuo Formation in the Yangtze craton of South China and Krol Group in the Lesser Himalaya of northern India archive the best paleontological and geochemical records to establish lower Ediacaran chronostratigraphy for global correlation, and to understand biological and environmental evolution after the terminal Cryogenian snowball Earth. Whereas the Doushantuo Formation has been intensively investigated using integrative approaches, there have only been isolated studies of the Krol Group—despite strong and persistent stratigraphic and biotic similarity between deposits of South China and the Lesser Himalaya through Ediacaran and lower Cambrian, thus impeding the development of both a regional and global picture. In this study, we carried out an integrative bio- and chemostratigraphic study of the Krol A Formation in the Solan area of northern India. We identified a prominent negative δ¹³C excursion and over a dozen species of acanthomorphic acritarchs from the Krol A Formation, including species belonging to the genera Appendisphaera, Cavaspina, Cymatiosphaeroides, Mengeosphaera, Tanarium, and Weissiella. Together with previous report of Tianzhushania from the underlying Infra-Krol Formation in the Lesser Himalaya and strata within a few meters above the basal Doushantuo cap dolostone in South China, the new data indicate that the negative δ¹³C excursion in Krol A likely correlates with the negative δ¹³C excursion EN2 in the lower Doushantuo Formation in South China. This correlation is consistent with Krol A acanthomorph species, most of which are also present in the lower Doushantuo Formation (e.g., upper part of member II in the Yangtze Gorges area and the Weng’an biota in Guizhou Province). The Indian data affirm the biostratigraphic significance of acanthomorphs, clarify key issues of lower Ediacaran bio- and chemostratigraphic correlation, and strengthen the global picture of eukaryote radiation after the Cryogenian snowball Earth glaciation.