Ediacaran C-isotope chemostratigraphy of the Lesser Himalaya, India
|Location||International Geological Congress,oslo 2008|
|Author||Tewari, Vinod C.۱; Sial, Alcides Nobrega۲|
|Holding Date||15 September 2008|
We report additional δ13C chemostratigraphic data for the Tehri and Pauri Garhwal areas of the Uttarakhand Lesser Himalaya, India. A composite δ13C profile for the Krol Formation (Ediacaran System) was prepared based on new data from the Rikhnikhal and Luxmanjhula sections of the Garhwal syncline and previously published δ13C data from Mussoorie syncline. The Blaini diamictites are well developed in both the sections representing Neoproterozoic glacial Marinoan/Blainian event. The Blaini pink cap microbial carbonate shows a negative δ13C excursion characteristic of cap carbonates globally. At the Luxmanjhula section, near Rishikesh, the δ13C values for a stromatolitic pink cap limestone of the Cryogenian Blaini Formation varies from -1.73 to -1.86 ‰ PDB. Oxygen isotopes range from -9.13 to -11.63‰ PDB in carbonates. The Lower Krol Formation is composed of shaly limestone and characterized by Vendotaenids. δ13C values rise to +4.93‰ PDB in the overlying Krol C dolomite in Rikhnikhal area, which rise to +6 ‰ PDB in the Mussoorie syncline. The Upper Krol carbonates are cherty, oolitic, stromatolitic-oncolitic and zebra fabric is well developed. Krol D/E Member has yielded well-preserved Ediacaran medusoids and frondose forms in the upper silty layers.
A negative excursion has been recorded (δ13C -10.52‰ PDB) just below the Ediacaran-Lower Cambrian boundary. The Ediacaran C-isotope stratigraphy of the Krol Formation (Krolian) of the Lesser Himalaya is identical to the Doushantuo, Lower Dengying and Upper Dengying Formations of South China. The palaeo-geographic reconstruction of the palaeo-continents suggests that around 650-540 Ma, Lesser Himalaya and South China were very close to each other. Present Ediacaran chemostratigraphy allows a subdivision of Ediacaran System and its global correlation.