Upper Jurassic radiolarians from the Naga Ophiolite, Nagaland, northeast India

Alan T. Baxter, Jonathan C. Aitchison, Sergey V. Zyabrev, Jason R. Ali

Radiolarians, extracted from cherts collected from an ophiolitic mélange near Salumi, Nagaland, NE India, have well-preserved tests and can be assigned to the Upper Jurassic (Kimmeridgian–lower Tithonian). These are the first well-preserved and clearly imaged radiolarians reported from the Naga Ophiolite. They are significantly older than fossils previously reported from this mélange, and their ages are similar to those determined radiometrically from associated igneous units.

Early Cretaceous radiolarians from the Spongtang massif, Ladakh, NW India: implications for Neo-Tethyan evolution

The discovery of two Early Cretaceous (mid-Valanginian – mid-Aptian range) radiolarian faunal assemblages from ribbon-bedded cherts collected near Photoskar in northern Ladakh, NW India, provides the first robust biostratigraphic age constraints associated with the Spongtang massif. This klippe of relict Neotethyan suprasubduction-zone ophiolitic rocks and related arc volcanic rocks crops out 30 km south of the Indus suture in Ladakh. The radiolarian assemblages, the age assignment of which lies between published radiometric ages, provide new constraints on the evolution of this intra-oceanic island arc system. Critically, from them it can be inferred that the system was appreciably long-lived (Jurassic – Cretaceous) and more continuous than is commonly considered.

Radiolarian age constraints on Mesotethyan ocean evolution, and their implications for development of the Bangong Nujiang suture, Tibet

Published in the Journal of the Geological Society, London, 2009

Radiolarian discoveries indicate that deep-marine conditions prevailed in central Tibet from the early Middle Jurassic until well into the Early Cretaceous (late Hauterivian – early Aptian; 131 – 121 Ma) and help to constrain the temporal extent of oceanic conditions along the Bangong – Nujiang suture. These new fossils occur in chert or siliceous mudstone blocks associated with the Lagkor Tso ophiolitic mélange. Basin inversion associated with closure of Mesotethys between the Qiangtang and Lhasa terranes was accompanied by mélange formation and predated regionally widespread deposition of overlying shallow-marine late Aptian – Albian orbitolinid limestones.