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Ophiolites in the southern belt (SB) occur as much larger peridotite massifs compared with those of the northern belt (NB), sporadically overlain by a thin layer of isotropic gabbro in the western part of Yarlung Zangbo suture zone (YZSZ) in Tibet, which in turn is tectonically thrust over a volcanic-sedimentary sequence. Geochemical data and radiolarian fauna of cherts and detrital zircon ages of litho-quartz sandstones in the sequence provide robust constraints to elucidate the stratigraphic and paleo-depositional environments in which these rocks formed. Eight cherts from Purang, Dongbo, Daba Qu, East Daba, and Labuzha massifs in the SB reveal Late Jurassic–Early Cretaceous radiolarians; they are coeval with minimum detrital zircon U-Pb ages of 132 and 149 Ma, respectively, from two litho-quartz sandstones in the northwestern part of Purang massif. Thirty chert samples from five massifs geochemically show that they have high SiO2 contents of 86.51–95.93 wt%, and high mean ratios of Al / (Al + Fe + Mn) ranging from 0.59 to 0.78, indicating a nonhydrothermal, biogenic, and terrigenous origin. Ce/Ce* ratios of cherts range from 0.93 to 1.52, combined with claystone interlayered with radiolarian chert sporadically overlying litho-quartz sandstone and quartzose sandstone, suggesting a continental slope setting. Given the structural and stratigraphic evidences of ophiolites associated with sedimentary strata and no arc-related magmatism in the SB, we propose that SB ophiolites and ophiolitic mélanges represent southward-thrust nappes from the NB. [ABSTRACT FROM AUTHOR]