The Terminal Proterozoic marine sequences, grading into Cambrian, are present in the Krol Basin (Lesser Himalaya), the Kashmir, Spiti-Zanskar and Kumaun Basins (Higher Himalaya) and in Marwar Basin (western India). These sequences postdate a major tectono-thermal event associated with Cadomian Orogeny and rest on eroded older successions which include well-dated Malani Igneous Suite (Malani Rhyolite 745 ±10 Ma; Siwana Granite 731± 14 Ma) in Western India and over the Salkhala Group with granites (745 ± 50 Ma) or the Simla Group in the Himalaya. This cycle of sedimentation terminated with Pan-African Orogeny in Late Cambrian. These sequences are dominantly siliciclastic in basins in Higher Himalaya while those in Krol Basin and Marwar Basin show development of thick carbonate-evaporite facies with or without phosphorite. From the Upper Vindhyan and Bhima Groups in central and south India, respectively a Chuaria-Tawuia Assemblage along with sphaeromorphida Acritarch of Early Neoproterozoic age has been recorded. The δ13C values range from +1.3 to +4.0 ‰ PDB and that of δ 18O from -5 to -9‰ PDB. These are, thus, not considered part of this sequence. In absence of age-determinating biota and radiometric dates from the basal part of the succession, the lower boundary of the Terminal Proterozoic cannot be delineated and dated. However, a significant depletion in values may be taken to mark the lower boundary. The upper boundary of the Terminal Proterozoic (Precambrian-Cambrian Boundary) cannot be demarcated in terms of GSSP due to the absence of trace fossils of Zone-1 (Harlaneilla podolika Zone) and Zone-II (Phycodes pedum Zone) in carbonate facies in Krol Basin and poor documentation of siliciclastic facies in Kashmir and Spiti-Zanskar Basins. The trace fossils correlative with ichnozone-III occur in all sections in the Himalayas and are useful for regional and global correlations. However, a significant depletion in δ13C values has been recorded in the carbonate facies of the Krol Basin between the horizons yielding Ediacaran and small shelly fossils of Meishucunian Zone-I. This has also been recorded in the Marwar Basin below the Phosphorite Bed. This depletion may be correlated with that recorded from the Precambrian-Cambrian transition in Siberian Platform, Anti Atlas Mountains, Morocco, China, etc. It may be taken into consideration to define and mark the boundary in the absence of trace fossils.
CITATION STYLE
Kumar, G., Shanker, R., Mathur, V. K., Maithy, P. K., Bhattacharya, S. K., & Jain, R. K. (1997). Terminal Proterozoic-Cambrian sequences in India: a review with special reference to Precambrian-Cambrian Boundary. Journal of Palaeosciences, 46((1-2)), 19–31. https://doi.org/10.54991/jop.1997.1314
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