Neotethyan Ocean

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

by Alan Baxter

The discovery of two Early Cretaceous (mid-Valanginian – mid-Aptian range) radiolarian faunal assemblages from... more 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.

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

by Alan Baxter

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... more 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.